enamines and ylides.docx

7/27/2019 enamines and ylides.docx

1/18

ENAMINES AND

YLIDES

M.SC-II (SEM-III)

ORGANIC CHEMISTRY


2/18

PREPERATION OF SULFOXIDES:

R S R1

O

Oxidation of alkyl sulphides by :

SR R1

+ H2O2 R S R1O

+ OH2

SCH3 CH3 H2O2 R S R1

O

OH2

Oxidation of alkyl sulphides using per-acids:

SR R1 R''COOOH CH3 S CH3

O

+ R''COOH

Generation of carbanion from sulfoxide:

CH3 S CH3

OBuLi/LDA/PhLi

or MeLiCH3 S CH2

-

O

Li+

+ Bu-Hmethyl sulphinyl carbanion

Application in C-C bond formation:


3/18

CH3 S CH3

O

CH3 S CH2-

O

Li+

OO

R S CH3

-keto sulphoxide

R Cl

O

- LiCl

n -BuLi

Red Al-Hg

CH3 CH3

O

i.e RCOCH 3

ketone

1)

CH3 S CH2-

O

+R

X

O

CH3

S R

Redn CH3

R

2)

OO

CH3

S

CH3

NaOH

BrCH2COOMe

Redn

NaBH4

OO

R

S

CH3

CH2COOMe

OOH

R

S

CH3

CH 2COOMe

3)

-MeOH

O

O

S

CH3

O

R

Redn

O

O

R

Lactone


4/18

O

(CH2)n

H

S PhLDA

RIO(CH2)n

R

S Ph R

(CH2)n

CH3S

PhH

2O

(CH2)n

OH

5)

O

CH3

S

CH2

CH3

CH3 I

CH3

LDA

SCH3

CH2

CH3

CH3

Ph

O

S PhOCH3

CH3

CH3

H2O

CH3

CH3

OH

CH3

6)

PREPARATION OF SULPHONES:

RS

R

O O

Addition of sulphuric acid to polar C=C bonds:

RS

H

O O+

H

H

Z

H

CH3 S

O

O

Z

H

Here, R=donor oracceptor group


5/18

Z= withdrawing group

O

+ PhSO 2H

O

H

H

SO2Ph

Addition of sulphuric acid to polar C=O or C=N bond:

SO O

HR

+ R1O

H RSO 2

OH

R1

S

O O

HR

+R

1NR'' RSO 2 R'

NHR''

O

O

O

CH3

CH3+ CH3 SO2H

O

SO2O

CH3

CH3

OH

CH

Generation of carbanion from sulphones:

CH3 SR1

O

O

n -BuLi or

LDA orPhLi

O

CH3 S

CH-

R1

O

Carbanion Now, this carbanion formed can be used in various C-C bond forming reactions.

Applications in C-C bond formation:

Formation of cyclopropane derivatives:


6/18

O

Ar-

S

Cl

On -BuLi

LDA

O

Ar-

S

CH-

ClO

Ar --SO2

Ni -Hg

i)

O

Ph

S O TS

O

LDA

O

PhS

CH-

O TS

OPh S

O

O

n-BuLi

C-Ph S

O

O

CH3IPh S

O

O CH3

CH3

ii)


7/18

O

CH3 S R

O+

Br

Br

LDA CH3 S

O

O

C-

R

Br

CH3 S

O

O

C-

R

Ni -Hg

R

iii)

Bamford-Steven Reaction

The BamfordStevens reaction is achemical reactionwhereby treatment

oftosylhydrazoneswith strong base givesalkenes.[1][2][3]

It is named for the British

chemistWilliam Randall Bamfordand the Scottish chemistThomas Stevens Stevens(1900

2000). The usage ofaprotic solventsgives predominantly Z-alkenes, whileprotic solventgives a

mixture of E- and Z-alkenes.

The treatment of tosylhydrazones with alkyl lithium reagents is called theShapiro reaction.

Reaction mechanism

The first step of the BamfordStevens reaction is the formation of the diazo compound 3.[4]

In protic solvents, the diazo compound 3 decomposes to thecarbenium ion5.
http://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/Carbenium_ionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Tosylhydrazonehttp://en.wikipedia.org/wiki/Tosylhydrazonehttp://en.wikipedia.org/wiki/Tosylhydrazonehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-bamford1952-1http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-bamford1952-1http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-adlington1983-3http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-adlington1983-3http://en.wikipedia.org/w/index.php?title=William_Randall_Bamford&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=William_Randall_Bamford&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=William_Randall_Bamford&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Thomas_Stevens_Stevens&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Thomas_Stevens_Stevens&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Thomas_Stevens_Stevens&action=edit&redlink=1http://en.wikipedia.org/wiki/Aprotic_solventhttp://en.wikipedia.org/wiki/Aprotic_solventhttp://en.wikipedia.org/wiki/Aprotic_solventhttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Protic_solventhttp://en.wikipedia.org/wiki/Protic_solventhttp://en.wikipedia.org/wiki/Protic_solventhttp://en.wikipedia.org/wiki/Shapiro_reactionhttp://en.wikipedia.org/wiki/Shapiro_reactionhttp://en.wikipedia.org/wiki/Shapiro_reactionhttp://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-creary1986-4http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-creary1986-4http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-creary1986-4http://en.wikipedia.org/wiki/Carbenium_ionhttp://en.wikipedia.org/wiki/Carbenium_ionhttp://en.wikipedia.org/wiki/Carbenium_ionhttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_Reaction_Scheme.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismA.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_Reaction_Scheme.pnghttp://en.wikipedia.org/wiki/Carbenium_ionhttp://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-creary1986-4http://en.wikipedia.org/wiki/Shapiro_reactionhttp://en.wikipedia.org/wiki/Protic_solventhttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Aprotic_solventhttp://en.wikipedia.org/w/index.php?title=Thomas_Stevens_Stevens&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=William_Randall_Bamford&action=edit&redlink=1http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-adlington1983-3http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-bamford1952-1http://en.wikipedia.org/wiki/Bamford%E2%80%93Stevens_reaction#cite_note-bamford1952-1http://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Tosylhydrazonehttp://en.wikipedia.org/wiki/Chemical_reaction


8/18

In aprotic solvents, the diazo compound 3 decomposes to the carbene 7.

Julia olefinationThe Julia olefination (also known as the JuliaLythgoe olefination) is thechemical

reactionofphenylsulfones(1) withaldehydes(orketones) to givealkenes(3) after alcohol

functionalization and reductive elimination usingsodium amalgam[1][2]orSmI2.[3]The reaction is

named after the French chemistMarc Julia.

This transformation highly favors formation of the trans-alkene.

All four steps can be carried out in a single reaction vessel, and use of R3X is optional. However,

purification of the sulfone intermediate 2 leads to higher yield and purity. Most often

R3

isacetylorbenzoyl, withacetic anhydrideorbenzoyl chlorideused in the preparation of 2.

Several reviews have been published.[4][5]

Reaction mechanism
http://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Phenylhttp://en.wikipedia.org/wiki/Phenylhttp://en.wikipedia.org/wiki/Sulfonehttp://en.wikipedia.org/wiki/Sulfonehttp://en.wikipedia.org/wiki/Sulfonehttp://en.wikipedia.org/wiki/Aldehydeshttp://en.wikipedia.org/wiki/Aldehydeshttp://en.wikipedia.org/wiki/Aldehydeshttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Sodium_amalgamhttp://en.wikipedia.org/wiki/Sodium_amalgamhttp://en.wikipedia.org/wiki/Sodium_amalgamhttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1978http://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1978http://en.wikipedia.org/wiki/Samarium(II)_iodidehttp://en.wikipedia.org/wiki/Samarium(II)_iodidehttp://en.wikipedia.org/wiki/Samarium(II)_iodidehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Keck1995http://en.wikipedia.org/wiki/Julia_olefination#endnote_Keck1995http://en.wikipedia.org/wiki/Julia_olefination#endnote_Keck1995http://en.wikipedia.org/wiki/Marc_Juliahttp://en.wikipedia.org/wiki/Marc_Juliahttp://en.wikipedia.org/wiki/Marc_Juliahttp://en.wikipedia.org/wiki/Acetylhttp://en.wikipedia.org/wiki/Acetylhttp://en.wikipedia.org/wiki/Acetylhttp://en.wikipedia.org/wiki/Benzoylhttp://en.wikipedia.org/wiki/Benzoylhttp://en.wikipedia.org/wiki/Benzoylhttp://en.wikipedia.org/wiki/Acetic_anhydridehttp://en.wikipedia.org/wiki/Acetic_anhydridehttp://en.wikipedia.org/wiki/Acetic_anhydridehttp://en.wikipedia.org/wiki/Benzoyl_chloridehttp://en.wikipedia.org/wiki/Benzoyl_chloridehttp://en.wikipedia.org/wiki/Benzoyl_chloridehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1985http://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1985http://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1985http://en.wikipedia.org/wiki/File:Juila_Olefination_Scheme.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismC.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismB.pnghttp://en.wikipedia.org/wiki/File:Juila_Olefination_Scheme.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismC.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismB.pnghttp://en.wikipedia.org/wiki/File:Juila_Olefination_Scheme.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismC.pnghttp://en.wikipedia.org/wiki/File:Bamford-Stevens_MechanismB.pnghttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1985http://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1985http://en.wikipedia.org/wiki/Benzoyl_chloridehttp://en.wikipedia.org/wiki/Acetic_anhydridehttp://en.wikipedia.org/wiki/Benzoylhttp://en.wikipedia.org/wiki/Acetylhttp://en.wikipedia.org/wiki/Marc_Juliahttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Keck1995http://en.wikipedia.org/wiki/Samarium(II)_iodidehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Kocienski1978http://en.wikipedia.org/wiki/Sodium_amalgamhttp://en.wikipedia.org/wiki/Sodium_amalgamhttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Aldehydeshttp://en.wikipedia.org/wiki/Sulfonehttp://en.wikipedia.org/wiki/Phenylhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reaction


9/18

The initial steps are straightforward. The phenyl sulfoneanion(2) reacts with an aldehyde to

form thealkoxide3. The alkoxide is functionalized with R3-X to give the stable intermediate 4.

The exact mechanism of the sodium amalgam reduction is unknown but has been shown to

proceed through a vinylic radical species (5).[1]Protonation of the vinylic radical gives the

desired product (6).

The stereochemistry of the alkene (6) is independent of the stereochemistry of the sulfone

intermediate 4. It is thought that the radical intermediates are able to equilibrate so that the morethermodynamically stable trans-olefin is produced most often.

Variations

Heteroaryl sulfones

The replacement of the phenyl sulfones with heteroaryl sulfones greatly alters the reaction

pathway.[6]

The most popular example is thebenzothiazolesulfone.[7]

The reaction of the

benzothiazole sulfone (1) withlithium diisopropylamide(LDA) gives a metallated benzothiazolyl

sulfone, which reacts quickly with aldehydes (or ketones) to give an alkoxides intermediate (2).Unlike the phenyl sulfones, this alkoxide intermediate (2) is unstable and will undergo aSmiles

rearrangement[8]

to give the sulfinate salt 4. The sulfinate salt (4) will spontaneously

eliminatesulfur dioxideandlithiumbenzothiazolone (5) producing the desired alkene (6).
http://en.wikipedia.org/wiki/Anionhttp://en.wikipedia.org/wiki/Anionhttp://en.wikipedia.org/wiki/Anionhttp://en.wikipedia.org/wiki/Alkoxidehttp://en.wikipedia.org/wiki/Alkoxidehttp://en.wikipedia.org/wiki/Alkoxidehttp://en.wikipedia.org/wiki/Julia_olefination#cite_note-1http://en.wikipedia.org/wiki/Julia_olefination#cite_note-1http://en.wikipedia.org/wiki/Julia_olefination#cite_note-1http://en.wikipedia.org/wiki/Julia_olefination#endnote_Blakemore2002http://en.wikipedia.org/wiki/Julia_olefination#endnote_Blakemore2002http://en.wikipedia.org/wiki/Julia_olefination#endnote_Blakemore2002http://en.wikipedia.org/wiki/Benzothiazolehttp://en.wikipedia.org/wiki/Benzothiazolehttp://en.wikipedia.org/wiki/Benzothiazolehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Baudin1991http://en.wikipedia.org/wiki/Julia_olefination#endnote_Baudin1991http://en.wikipedia.org/wiki/Julia_olefination#endnote_Baudin1991http://en.wikipedia.org/wiki/Lithium_diisopropylamidehttp://en.wikipedia.org/wiki/Lithium_diisopropylamidehttp://en.wikipedia.org/wiki/Lithium_diisopropylamidehttp://en.wikipedia.org/wiki/Smiles_rearrangementhttp://en.wikipedia.org/wiki/Smiles_rearrangementhttp://en.wikipedia.org/wiki/Smiles_rearrangementhttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Truce1970http://en.wikipedia.org/wiki/Julia_olefination#endnote_Truce1970http://en.wikipedia.org/wiki/Julia_olefination#endnote_Truce1970http://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Lithiumhttp://en.wikipedia.org/wiki/Lithiumhttp://en.wikipedia.org/wiki/Lithiumhttp://en.wikipedia.org/wiki/File:Juila_Olefination_Mechanism.pnghttp://en.wikipedia.org/wiki/Lithiumhttp://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Truce1970http://en.wikipedia.org/wiki/Smiles_rearrangementhttp://en.wikipedia.org/wiki/Smiles_rearrangementhttp://en.wikipedia.org/wiki/Lithium_diisopropylamidehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Baudin1991http://en.wikipedia.org/wiki/Benzothiazolehttp://en.wikipedia.org/wiki/Julia_olefination#endnote_Blakemore2002http://en.wikipedia.org/wiki/Julia_olefination#cite_note-1http://en.wikipedia.org/wiki/Alkoxidehttp://en.wikipedia.org/wiki/Anion


10/18

Since the benzothiazole variation of the Julia olefination does not involve equilibrating

intermediates, the stereochemical outcome is a result of the stereochemistry of the initial

carbonyl addition. As a result, this reaction often generates a mixture of alkene stereoisomers.

Bestmann-ohira reagent:

Introduction

Bestmann-Ohira reagent [(1-diazo-2-oxopropyl)phosphonate] can be prepared by the reaction ofdimethyl-2-oxopropylphosphonate, TosN3[a] orp-acetamidobenzenesulfonyl azide, [b] NaH, t-BuOK or Et3N in benzene and THF. An alternative is the preparation using polymer-supportedsulfonyl azide and t-BuOK in methylenchloride. [c] The Bestmann-Ohiro reagent is widely usedin the conversion of primary alcohols, aldehydes, ketones, and amides into alkynes. Recently, itwas employed in the synthesis of pyrazoles as well as 1,3-oxazoles.
https://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Ahttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Ahttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Ahttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Bhttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Bhttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Bhttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Chttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Chttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Chttp://en.wikipedia.org/wiki/File:Benzothiazole-Julia_Olefination_Mechanism.pnghttp://en.wikipedia.org/wiki/File:Benzothiazole-Julia_Olefination_Mechanism.pnghttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Chttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1Bhttps://www.thieme-connect.de/ejournals/abstract/10.1055/s-0029-1218101#RV29809ST-1A


11/18

Scheme1

Bestmann modification

OhiraBestmann reagent

IUPAC name[hide]

imethyl (1-diazo-2-oxopropyl)phosphonate

Dimethyl (diazomethyl)phosphonate can be generated in situ from dimethyl-1-diazo-2-

oxopropylphosphonate (also called Bestmann's reagent) by reaction

withmethanolandpotassium carbonate. Reaction of Bestmann's reagent with aldehydes gives

terminal alkynes often in very high yield.[4][5]
http://en.wikipedia.org/wiki/International_Union_of_Pure_and_Applied_Chemistry_nomenclaturehttp://en.wikipedia.org/wiki/International_Union_of_Pure_and_Applied_Chemistry_nomenclaturehttp://en.wikipedia.org/wiki/International_Union_of_Pure_and_Applied_Chemistry_nomenclaturehttp://en.wikipedia.org/wiki/Methanolhttp://en.wikipedia.org/wiki/Methanolhttp://en.wikipedia.org/wiki/Methanolhttp://en.wikipedia.org/wiki/Potassium_carbonatehttp://en.wikipedia.org/wiki/Potassium_carbonatehttp://en.wikipedia.org/wiki/Potassium_carbonatehttp://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-muller1996-4http://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-muller1996-4http://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-muller1996-4http://en.wikipedia.org/wiki/File:Ohira-bestmann_reagent_2d-skeletal.pnghttp://en.wikipedia.org/wiki/File:Ohira-bestmann_reagent_2d-skeletal.pnghttp://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-muller1996-4http://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-muller1996-4http://en.wikipedia.org/wiki/Potassium_carbonatehttp://en.wikipedia.org/wiki/Methanolhttp://en.wikipedia.org/wiki/International_Union_of_Pure_and_Applied_Chemistry_nomenclaturehttp://en.wikipedia.org/wiki/International_Union_of_Pure_and_Applied_Chemistry_nomenclature


12/18

The use of the milder potassium carbonate makes this procedure much more compatible with a

wide variety offunctional groups.

Another modification for less reactive aldehydes is made by replacement of potassium

carbonate withcaesium carbonatein MeOH and results in a drastic yield increase.[6]

BartonKellogg reaction

The BartonKellogg reaction is acoupling reactionbetween aketoneand

athioketonethrough adiazointermediate forming analkene.[1][2][3]

This reaction was pioneered byHermann Staudinger[4]

, and the reaction also goes by thename Staudinger type diazo-thioketone coupling.

Reaction mechanism

In thereaction mechanismfor this reaction thediazocompound is a1,3-dipolewhich reacts with

thethioketonein a1,3-dipolar cycloadditionto athiadiazoline. This intermediate is unstable and

through nitrogen gas expulsion and formation of an intermediatethiocarbonyl ylideit forms a

stableepisulfide.Triphenylphosphineopens the three-membered ring and then forms a

sulfaphosphatane in a manner similar to theWittig reaction. In the final step

triphenylphosphinesulfoxide is expulsed liberating thealkene.
http://en.wikipedia.org/wiki/Functional_grouphttp://en.wikipedia.org/wiki/Functional_grouphttp://en.wikipedia.org/wiki/Functional_grouphttp://en.wikipedia.org/wiki/Caesium_carbonatehttp://en.wikipedia.org/wiki/Caesium_carbonatehttp://en.wikipedia.org/wiki/Caesium_carbonatehttp://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-6http://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-6http://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-6http://en.wikipedia.org/wiki/Coupling_reactionhttp://en.wikipedia.org/wiki/Coupling_reactionhttp://en.wikipedia.org/wiki/Coupling_reactionhttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Bartonhttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Bartonhttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Kellogg1976http://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Kellogg1976http://en.wikipedia.org/wiki/Hermann_Staudingerhttp://en.wikipedia.org/wiki/Hermann_Staudingerhttp://en.wikipedia.org/wiki/Hermann_Staudingerhttp://en.wikipedia.org/wiki/Hermann_Staudingerhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/1,3-dipolehttp://en.wikipedia.org/wiki/1,3-dipolehttp://en.wikipedia.org/wiki/1,3-dipolehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/1,3-dipolar_cycloadditionhttp://en.wikipedia.org/wiki/1,3-dipolar_cycloadditionhttp://en.wikipedia.org/wiki/1,3-dipolar_cycloadditionhttp://en.wikipedia.org/w/index.php?title=Thiadiazoline&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Thiadiazoline&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Thiadiazoline&action=edit&redlink=1http://en.wikipedia.org/wiki/Thiocarbonyl_ylidehttp://en.wikipedia.org/wiki/Thiocarbonyl_ylidehttp://en.wikipedia.org/wiki/Thiocarbonyl_ylidehttp://en.wikipedia.org/wiki/Episulfidehttp://en.wikipedia.org/wiki/Episulfidehttp://en.wikipedia.org/wiki/Episulfidehttp://en.wikipedia.org/wiki/Triphenylphosphinehttp://en.wikipedia.org/wiki/Triphenylphosphinehttp://en.wikipedia.org/wiki/Triphenylphosphinehttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/File:Barton-Kellogg_reaction.pnghttp://en.wikipedia.org/wiki/File:Bestmann's_Reagent_Scheme.pnghttp://en.wikipedia.org/wiki/File:Barton-Kellogg_reaction.pnghttp://en.wikipedia.org/wiki/File:Bestmann's_Reagent_Scheme.pnghttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Triphenylphosphinehttp://en.wikipedia.org/wiki/Episulfidehttp://en.wikipedia.org/wiki/Thiocarbonyl_ylidehttp://en.wikipedia.org/w/index.php?title=Thiadiazoline&action=edit&redlink=1http://en.wikipedia.org/wiki/1,3-dipolar_cycloadditionhttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/1,3-dipolehttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Hermann_Staudingerhttp://en.wikipedia.org/wiki/Hermann_Staudingerhttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Kellogg1976http://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Bartonhttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_Bartonhttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Coupling_reactionhttp://en.wikipedia.org/wiki/Ohira-Bestmann_reaction#cite_note-6http://en.wikipedia.org/wiki/Caesium_carbonatehttp://en.wikipedia.org/wiki/Functional_group


13/18

Scope

The diazo compound can be obtained from aketoneby reaction withhydrazineto

ahydrazonefollowed byoxidation. Many reagents exist for this conversion for examplesilver(I)

oxideand(bis(trifluoroacetoxy)iodo)benzene[5]

. Thethioketonerequired for this reaction can be

obtained from a ketone andphosphorus pentasulfide. Desulfurization of the episulfide can be

accomplished by many phosphines and also bycopperpowder.

The main advantage of this reaction over theMcMurry reactionis the notion that the reaction

can take place with two different ketones. In this regard the diazo-thioketone coupling is a cross-

coupling rather than a homocoupling.

Stevens rearrangement

The Stevens rearrangement inorganic chemistryis anorganic reactionconvertingquaternary

ammonium saltsandsulfonium saltsto the correspondingaminesorsulfidesin presence of a

strongbasein a1,2-rearrangement.[1]
http://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Hydrazinehttp://en.wikipedia.org/wiki/Hydrazinehttp://en.wikipedia.org/wiki/Hydrazinehttp://en.wikipedia.org/wiki/Hydrazonehttp://en.wikipedia.org/wiki/Hydrazonehttp://en.wikipedia.org/wiki/Hydrazonehttp://en.wikipedia.org/wiki/Organic_oxidationhttp://en.wikipedia.org/wiki/Organic_oxidationhttp://en.wikipedia.org/wiki/Organic_oxidationhttp://en.wikipedia.org/wiki/Silver(I)_oxidehttp://en.wikipedia.org/wiki/Silver(I)_oxidehttp://en.wikipedia.org/wiki/Silver(I)_oxidehttp://en.wikipedia.org/wiki/Silver(I)_oxidehttp://en.wikipedia.org/wiki/(bis(trifluoroacetoxy)iodo)benzenehttp://en.wikipedia.org/wiki/(bis(trifluoroacetoxy)iodo)benzenehttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_terWielhttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_terWielhttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_terWielhttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Phosphorus_pentasulfidehttp://en.wikipedia.org/wiki/Phosphorus_pentasulfidehttp://en.wikipedia.org/wiki/Phosphorus_pentasulfidehttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/McMurry_reactionhttp://en.wikipedia.org/wiki/McMurry_reactionhttp://en.wikipedia.org/wiki/McMurry_reactionhttp://en.wikipedia.org/wiki/Organic_chemistryhttp://en.wikipedia.org/wiki/Organic_chemistryhttp://en.wikipedia.org/wiki/Organic_chemistryhttp://en.wikipedia.org/wiki/Organic_reactionhttp://en.wikipedia.org/wiki/Organic_reactionhttp://en.wikipedia.org/wiki/Organic_reactionhttp://en.wikipedia.org/wiki/Quaternary_ammonium_salthttp://en.wikipedia.org/wiki/Quaternary_ammonium_salthttp://en.wikipedia.org/wiki/Quaternary_ammonium_salthttp://en.wikipedia.org/wiki/Quaternary_ammonium_salthttp://en.wikipedia.org/wiki/Sulfonium_salthttp://en.wikipedia.org/wiki/Sulfonium_salthttp://en.wikipedia.org/wiki/Sulfonium_salthttp://en.wikipedia.org/wiki/Aminehttp://en.wikipedia.org/wiki/Aminehttp://en.wikipedia.org/wiki/Aminehttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/1,2-rearrangementhttp://en.wikipedia.org/wiki/1,2-rearrangementhttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Pine-1http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Pine-1http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Pine-1http://en.wikipedia.org/wiki/File:Barton-Kellogg_reaction_example.svghttp://en.wikipedia.org/wiki/File:Barton-Kellogg_reaction_mechanism.svghttp://en.wikipedia.org/wiki/File:Barton-Kellogg_reaction_example.svghttp://en.wikipedia.org/wiki/File:Barton-Kellogg_reaction_mechanism.svghttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Pine-1http://en.wikipedia.org/wiki/1,2-rearrangementhttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Aminehttp://en.wikipedia.org/wiki/Sulfonium_salthttp://en.wikipedia.org/wiki/Quaternary_ammonium_salthttp://en.wikipedia.org/wiki/Quaternary_ammonium_salthttp://en.wikipedia.org/wiki/Organic_reactionhttp://en.wikipedia.org/wiki/Organic_chemistryhttp://en.wikipedia.org/wiki/McMurry_reactionhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Phosphorus_pentasulfidehttp://en.wikipedia.org/wiki/Thioketonehttp://en.wikipedia.org/wiki/Barton%E2%80%93Kellogg_reaction#endnote_terWielhttp://en.wikipedia.org/wiki/(bis(trifluoroacetoxy)iodo)benzenehttp://en.wikipedia.org/wiki/Silver(I)_oxidehttp://en.wikipedia.org/wiki/Silver(I)_oxidehttp://en.wikipedia.org/wiki/Organic_oxidationhttp://en.wikipedia.org/wiki/Hydrazonehttp://en.wikipedia.org/wiki/Hydrazinehttp://en.wikipedia.org/wiki/Ketone


14/18

The reactants can be obtained byalkylationof the corresponding amines and sulfides.

ThesubstituentR next the aminemethylene bridgeis anelectron-withdrawing group.

The original 1928 publication by T.S. Stevens[2]concerned the reaction of1-phenyl-2- (N, N-

dimethyl) ethanone withbenzyl bromideto the ammonium salt followed by the rearrangement

reaction withsodium hydroxidein water to the rearranged amine.

A 1932 publication[3]described the corresponding sulfur reaction.

Reaction mechanism

The reaction mechanism of the Stevens rearrangement is one of the most controversial reaction

mechanism in organic chemistry.[4]

Key in thereaction mechanism[5][6]

for the Stevens

rearrangement (explained for the nitrogen reaction) is the formation of

anylideafterdeprotonationof the ammonium salt by a strong base. Deprotonation is aided by

electron-withdrawing properties of substituent R. Several reaction modes exist for the actual

rearrangement reaction.

Aconcerted reactionrequires anantarafacialreaction mode but since the migrating group

displaysretention of configurationthis mechanism is unlikely.

In an alternative reaction mechanism the NC bond of the leaving group ishomolyticallycleaved

to form a di-radical pair (3a). In order to explain the observed retention of configuration, the
http://en.wikipedia.org/wiki/Alkylationhttp://en.wikipedia.org/wiki/Alkylationhttp://en.wikipedia.org/wiki/Alkylationhttp://en.wikipedia.org/wiki/Substituenthttp://en.wikipedia.org/wiki/Substituenthttp://en.wikipedia.org/wiki/Substituenthttp://en.wikipedia.org/wiki/Methylene_bridgehttp://en.wikipedia.org/wiki/Methylene_bridgehttp://en.wikipedia.org/wiki/Methylene_bridgehttp://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Stevens3193-2http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Stevens3193-2http://en.wikipedia.org/wiki/Benzyl_bromidehttp://en.wikipedia.org/wiki/Benzyl_bromidehttp://en.wikipedia.org/wiki/Benzyl_bromidehttp://en.wikipedia.org/wiki/Sodium_hydroxidehttp://en.wikipedia.org/wiki/Sodium_hydroxidehttp://en.wikipedia.org/wiki/Sodium_hydroxidehttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-3http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-3http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-4http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-4http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-4http://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-6http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-6http://en.wikipedia.org/wiki/Ylidehttp://en.wikipedia.org/wiki/Ylidehttp://en.wikipedia.org/wiki/Ylidehttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Concerted_reactionhttp://en.wikipedia.org/wiki/Concerted_reactionhttp://en.wikipedia.org/wiki/Concerted_reactionhttp://en.wikipedia.org/wiki/Antarafacialhttp://en.wikipedia.org/wiki/Antarafacialhttp://en.wikipedia.org/wiki/Antarafacialhttp://en.wikipedia.org/wiki/Retention_of_configurationhttp://en.wikipedia.org/wiki/Retention_of_configurationhttp://en.wikipedia.org/wiki/Retention_of_configurationhttp://en.wikipedia.org/wiki/Homolysis_(chemistry)http://en.wikipedia.org/wiki/Homolysis_(chemistry)http://en.wikipedia.org/wiki/Homolysis_(chemistry)http://en.wikipedia.org/wiki/File:Stevens1928rearrangement.pnghttp://en.wikipedia.org/wiki/File:Stevens_rearrangement_overview.svghttp://en.wikipedia.org/wiki/File:Stevens1928rearrangement.pnghttp://en.wikipedia.org/wiki/File:Stevens_rearrangement_overview.svghttp://en.wikipedia.org/wiki/Homolysis_(chemistry)http://en.wikipedia.org/wiki/Retention_of_configurationhttp://en.wikipedia.org/wiki/Antarafacialhttp://en.wikipedia.org/wiki/Concerted_reactionhttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Ylidehttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-6http://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-4http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-3http://en.wikipedia.org/wiki/Sodium_hydroxidehttp://en.wikipedia.org/wiki/Benzyl_bromidehttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-Stevens3193-2http://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Methylene_bridgehttp://en.wikipedia.org/wiki/Substituenthttp://en.wikipedia.org/wiki/Alkylation


15/18

presence of asolvent cageis invoked. Another possibility is the formation of a cation-anion pair

(3b), also in a solvent cage. Recently the elimination recombination coupling mechanism opens

a new approach to understand the formation of normal and abnormal product in the stevens

rearrangement[7]

Scope

Competing reactions are theSommelet-Hauser rearrangementand theHofmann elimination.

In one application a double-Stevens rearrangement expands acyclophanering.[8]

The ylide is

preparedin situby reaction of thediazocompound ethyl diazomalonate with asulfidecatalyzed

by dirhodium tetraacetate inrefluxingxylene.
http://en.wikipedia.org/wiki/Solvent_cagehttp://en.wikipedia.org/wiki/Solvent_cagehttp://en.wikipedia.org/wiki/Solvent_cagehttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-7http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-7http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-7http://en.wikipedia.org/wiki/Sommelet-Hauser_rearrangementhttp://en.wikipedia.org/wiki/Sommelet-Hauser_rearrangementhttp://en.wikipedia.org/wiki/Sommelet-Hauser_rearrangementhttp://en.wikipedia.org/wiki/Hofmann_eliminationhttp://en.wikipedia.org/wiki/Hofmann_eliminationhttp://en.wikipedia.org/wiki/Hofmann_eliminationhttp://en.wikipedia.org/wiki/Cyclophanehttp://en.wikipedia.org/wiki/Cyclophanehttp://en.wikipedia.org/wiki/Cyclophanehttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-8http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-8http://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-8http://en.wikipedia.org/wiki/In_situhttp://en.wikipedia.org/wiki/In_situhttp://en.wikipedia.org/wiki/In_situhttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Refluxhttp://en.wikipedia.org/wiki/Refluxhttp://en.wikipedia.org/wiki/Xylenehttp://en.wikipedia.org/wiki/Xylenehttp://en.wikipedia.org/wiki/Xylenehttp://en.wikipedia.org/wiki/File:Stevens_mechanism.pnghttp://en.wikipedia.org/wiki/Xylenehttp://en.wikipedia.org/wiki/Refluxhttp://en.wikipedia.org/wiki/Sulfidehttp://en.wikipedia.org/wiki/Diazohttp://en.wikipedia.org/wiki/In_situhttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-8http://en.wikipedia.org/wiki/Cyclophanehttp://en.wikipedia.org/wiki/Hofmann_eliminationhttp://en.wikipedia.org/wiki/Sommelet-Hauser_rearrangementhttp://en.wikipedia.org/wiki/Stevens_rearrangement#cite_note-7http://en.wikipedia.org/wiki/Solvent_cage


16/18

HornerWadsworthEmmons reaction(Redirected fromWittig-Horner reaction)

The HornerWadsworthEmmons reaction (orHWE reaction) is thechemical reactionof

stabilizedphosphonatecarbanionswithaldehydes(orketones) to produce predominantly E-

alkenes.[1]

In 1958,Leopold Hornerpublished a modifiedWittig reactionusing phosphonate-stabilized

carbanions.[2][3]

William S. WadsworthandWilliam D. Emmonsfurther defined the reaction.[4][5]

In contrast tophosphonium ylidesused in theWittig reaction, phosphonate-stabilized carbanions

are morenucleophilicbut less basic. Likewise, phosphonate-stabilized carbanions can be
http://en.wikipedia.org/w/index.php?title=Wittig-Horner_reaction&redirect=nohttp://en.wikipedia.org/w/index.php?title=Wittig-Horner_reaction&redirect=nohttp://en.wikipedia.org/w/index.php?title=Wittig-Horner_reaction&redirect=nohttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-1http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-1http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-1http://en.wikipedia.org/wiki/Leopold_Hornerhttp://en.wikipedia.org/wiki/Leopold_Hornerhttp://en.wikipedia.org/wiki/Leopold_Hornerhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-2http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-2http://en.wikipedia.org/w/index.php?title=William_S._Wadsworth&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=William_S._Wadsworth&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=William_S._Wadsworth&action=edit&redlink=1http://en.wikipedia.org/wiki/William_D._Emmonshttp://en.wikipedia.org/wiki/William_D._Emmonshttp://en.wikipedia.org/wiki/William_D._Emmonshttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-4http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-4http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-4http://en.wikipedia.org/wiki/Phosphonium_ylidehttp://en.wikipedia.org/wiki/Phosphonium_ylidehttp://en.wikipedia.org/wiki/Phosphonium_ylidehttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Nucleophilichttp://en.wikipedia.org/wiki/Nucleophilichttp://en.wikipedia.org/wiki/Nucleophilichttp://en.wikipedia.org/wiki/File:Horner-Wadsworth-Emmons_Reaction_Example.pnghttp://en.wikipedia.org/wiki/File:Stevens_rearrangement_applied.pnghttp://en.wikipedia.org/wiki/File:Horner-Wadsworth-Emmons_Reaction_Example.pnghttp://en.wikipedia.org/wiki/File:Stevens_rearrangement_applied.pnghttp://en.wikipedia.org/wiki/Nucleophilichttp://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Phosphonium_ylidehttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-4http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-4http://en.wikipedia.org/wiki/William_D._Emmonshttp://en.wikipedia.org/w/index.php?title=William_S._Wadsworth&action=edit&redlink=1http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-2http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-2http://en.wikipedia.org/wiki/Wittig_reactionhttp://en.wikipedia.org/wiki/Leopold_Hornerhttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-1http://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/w/index.php?title=Wittig-Horner_reaction&redirect=no


17/18

alkylated. Unlike phosphonium ylides, the dialkylphosphate salt byproduct is easily removed

byaqueousextraction.

Several reviews have been published.

Reaction mechanism

The HornerWadsworthEmmons reaction begins with thedeprotonationof thephosphonateto

give the phosphonatecarbanion1.Nucleophilic additionof the carbanion onto the aldehyde 2

(or ketone) producing 3a or 3b is therate-limiting step.[10]If R2=H, then intermediates 3a and 4a

and intermediates 3b and 4b can interconvert with each other.[11]The finaleliminationof 4a and

4b yield E-alkene 5 and Z-alkene 6.

The ratio of alkeneisomers5 and 6 is dependent upon thestereochemicaloutcome of the initial

carbanion addition and upon the ability of the intermediates toequilibrate.

Theelectron-withdrawing group(EWG) alpha to the phosphonate is necessary for the final

elimination to occur. In the absence of an electron-withdrawing group, the final product is the -

hydroxyphosphonate 3a and 3b.[12]However, these -hydroxyphosphonates can be transformed

toalkenesby reaction withdiisopropylcarbodiimide.

Stereoselectivity

The HornerWadsworthEmmons reaction favours the formation of E-alkenes. In general, the

more equilibration amongst intermediates, the higher the selectivity for E-alkene formation.
http://en.wikipedia.org/wiki/Aqueoushttp://en.wikipedia.org/wiki/Aqueoushttp://en.wikipedia.org/wiki/Liquid-liquid_extractionhttp://en.wikipedia.org/wiki/Liquid-liquid_extractionhttp://en.wikipedia.org/wiki/Liquid-liquid_extractionhttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Nucleophilic_additionhttp://en.wikipedia.org/wiki/Nucleophilic_additionhttp://en.wikipedia.org/wiki/Nucleophilic_additionhttp://en.wikipedia.org/wiki/Rate-limiting_stephttp://en.wikipedia.org/wiki/Rate-limiting_stephttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-10http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-10http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-10http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-11http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-11http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-11http://en.wikipedia.org/wiki/Elimination_reactionhttp://en.wikipedia.org/wiki/Elimination_reactionhttp://en.wikipedia.org/wiki/Elimination_reactionhttp://en.wikipedia.org/wiki/Isomerhttp://en.wikipedia.org/wiki/Isomerhttp://en.wikipedia.org/wiki/Isomerhttp://en.wikipedia.org/wiki/Stereochemicalhttp://en.wikipedia.org/wiki/Stereochemicalhttp://en.wikipedia.org/wiki/Stereochemicalhttp://en.wikipedia.org/wiki/Chemical_equilibriumhttp://en.wikipedia.org/wiki/Chemical_equilibriumhttp://en.wikipedia.org/wiki/Chemical_equilibriumhttp://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-12http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-12http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-12http://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Diisopropylcarbodiimidehttp://en.wikipedia.org/wiki/Diisopropylcarbodiimidehttp://en.wikipedia.org/wiki/Diisopropylcarbodiimidehttp://en.wikipedia.org/wiki/File:Horner-Wadsworth-Emmons_Mechanism.pnghttp://en.wikipedia.org/wiki/Diisopropylcarbodiimidehttp://en.wikipedia.org/wiki/Alkenehttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-12http://en.wikipedia.org/wiki/Electron-withdrawing_grouphttp://en.wikipedia.org/wiki/Chemical_equilibriumhttp://en.wikipedia.org/wiki/Stereochemicalhttp://en.wikipedia.org/wiki/Isomerhttp://en.wikipedia.org/wiki/Elimination_reactionhttp://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-11http://en.wikipedia.org/wiki/Wittig-Horner_reaction#cite_note-10http://en.wikipedia.org/wiki/Rate-limiting_stephttp://en.wikipedia.org/wiki/Nucleophilic_additionhttp://en.wikipedia.org/wiki/Carbanionhttp://en.wikipedia.org/wiki/Phosphonatehttp://en.wikipedia.org/wiki/Deprotonationhttp://en.wikipedia.org/wiki/Liquid-liquid_extractionhttp://en.wikipedia.org/wiki/Aqueous


18/18

Bibliography:BOOKS:

AHLUWALIA

PS KALSI

ADVANCED ORGANIC CHEMISTRY BY BRUCKNER

NET:

WWW.WIKIPEDIA.COM

GOOGLE.COM
http://www.wikipedia.com/http://www.wikipedia.com/http://www.wikipedia.com/

Documents

enamines and ylides.docx