Bull. SOC. Chim. Belg. vol. 103 I no 5-6 / 1994 EUROPEAN SECTION

0037-9646 I94 1 $2.00 + 0.00 Q 1994 Comitb van Beheer van het Bulletin V.Z.W.

LEWIS ACID MEDIATED REACTION OF SELENOACETALS WITH ALLYLSILANES AND ALLYLSTANNANES : SYNTHESIS OF HOMOALLYLSELENIDES

Bernard Hermans and Usz lo Hevesi* Department of Chemistry, Facultes Universitaires N.-D. de la Paix, 61, rue de Bruxelles, 8-5000 Namur (Belgium)

Dedicated to Professor Jacques Nasielski (ULB) 011 the occasion of his retireritent

ABSTRACT Selenoacetals react with allyltrimethylsilane in the presence of tin tetrachloride to produce homoallyl selenides in

moderate to good yields. Aliphatic acetals react less efficiently than do aromatic ones, especially when steric factors can play a significant role. The use of allyl stannanes as nucleophiles is complicated by transmetallation side reactions with Lewis acids; in the case of tin tetrachloride this is the only observable transformation. However, non transmetallating Lewis acids such as BF3 0 OEtn, ZnCln, AIC13, etc ... also allow the synthesis of homoallyl selenides from selenoacetals and allyl stannanes. The reaction of bis(methylseleno)phenylmethane with tributylcrotylstannane gave a diastereo- isomeric mixture of homoallyl selenides where the syn isomer predominated (synlanti = 70/30), whereas the reverse stereoselectivity was observed for the reaction of 1,l -bis(methylseleno)-2-phenylpropane with allyltributylstannane.

We have shown some years ago that stable a,a-bis- (methylse1eno)carbenium ions can be generated in high yield by the reaction of 1,1,1 -tris(methylseleno)alcanes with triphenylcarbenium ion salts’. On similar grounds, it was found that the same orthoselen~esters~~~, and more signifi- cantly, selenoacetals could be activated by suitable Lewis acids in order to bring about useful C-C bond forming reactions with various carbon nucleophiles such as silyl enol ether^^-^, olefinic double bonds7-’, aromatic hydrocar- bons”, furan’ ’, pyrrole’ ’-16 and trimethylsilyl cyanide”.

In this paper we wish to report our work using allylsilanes and allylstannanes’sa’b.

RESULTS AND DISCUSSION In connection with earlier studies of the Lewis acid

mediated reaction of selenoacetals with silyl enol ethers4”’, we have found that both tin and titanium tetra- chloride did allow the reaction to take place, but usually better yields were obtained with SnC14. However, since allylstannanes are known to undergo transmetallation reaction with tin tetrachloride20’2’, it was of primary impor-

n-Hex SeMe ’ Lewi; A ‘ ’ n-Hex, SeMe

, c\ +

Me’ ’SeMe

s HClO \ ‘ l V 1

C H ~ I , I T O C I ~ ( ~ )

l c 2c

Entry Lewis Acid M T “C t (h) Yield in 2c (%)

Tic14 (2.0 eq.) SnC14 (2.0 eq.) ZnCln (1 .O eq.)

BF3 0 OEtn (2.0 eq.) CuCIn (2.0 eq.) Tic14 (2.0 eq.) SnC14 (2.0 eq.) ZnCln (1 .O eq.)

BF3 0 OEt2 (2.0 eq.)

SiMea (2.0 eq.) SiMes (2.0 eq.) SiMes (2.0 eq.) SiMes (2.0 eq.) SiMea (2.0 eq.) SnBua (2.0 eq.) SnBua (2.0 eq.) SnBus (1 .O eq.) SnBus (1 .O eq.)

- 40 3.0 - 40 1 .o 25 22

- 40 4.5 25 4.0

- 40 4.0 - 40 4.0 25 16 25 16

0 69 0 0 0 0 0

60 5a

SCHEME 1.

- 257 -

tance to screen first different Lewis acids in order to find the best suited one(s) for our purposes. The results of this screening are displayed in Scheme 1, and they show that among those tried, only tin tetrachloride is efficient in promoting the reaction of 2,2-bis(methylseleno)octane l c with allyltrimethylsilane to form the corresponding homo- ally1 selenide 2c in 69% yield. In all the other cases, the starting selenoacetal 1 c was recovered unchanged.

The same type of reaction of the selenoacetal lc and allyltributylstannane occurred at room temperature and in the presence of zinc chloride or BF30OEtn; it did not proceed at all using Tic14 or SnC14.

These results are roughly understandable in terms of what is presently known on the role Lewis acids can play in this type of reactions2*. In agreement with our own expe- rience, it has been reported23 that allyltrimethylsilane does not undergo transmetallation (also called redistribution or metathesis) reaction with Tic14 even after several hours at room temperature. Therefore, the absence of reaction (Scheme 1, entry 1) must be due to an inappropriate activa- tion of the selenoacetal by titanium tetrachloride. This is corroborated by our earlier findings on the reaction of selenoacetals with silyl enol ethers4'", as well as by literature reports on the reaction of thioacetals with silyl enol ethers24 and with allyltrimethyl~ilane~~. For all these reactions SnC14 appeared to be a superior Lewis acid as compared to TiC14. The difference between these two Lewis acids is further illustrated by the 'H NMR chemical shifts (CDCb, RT) of the methyne and SeCH3 protons of selenoacetal la : i) 3.91 and 2.02 ppm, respectively, for the free acetal, ii) 4.35 and 2.62 ppm, respectively, for la in the presence of 1 eq. of TiC14, and iii) 4.54 and 3.00 ppm, respectively, for la in the presence of 1 eq. of SnC14. These data suggest stronger complexation of the selenoacetals by SnC14 than by TiC14. On the other hand, we have also found that transmetallation does occur between SnC14 and allyltrimethylsilane, although this reaction is dependent on solvent and temperature. It takes 4 hours in carbon tetra- chloride at room temperature, a few minutes in CDC13 at the same temperature, and about 0.5 h at - 40°C in methylene chloride. This phenomenon might have a dramatic nega- tive effect on the allylation reaction due to the great reacti- vity difference that can be assumed between allyltrimethyl- silane and allyltrichlorostannane resulting from transmetal- lation of the former by SnC1426. Consequently, the only explanation for the efficiency of the reaction shown in Scheme 1, entry 2 is that the strong complexation of the selenoacetal with SnC14 prevents the latter from transme- tallation of the allylsilane. Similar scenarios have been shown to occur during the SnC14 promoted reaction of alde- hydes with allyl~tannanes~', as well as in the intramolecular

reaction of an oxygen acetal with an allylsilane moiety induced by the Same Lewis acid28.

In the light of the above and of the much higher propensity of allyltributylstannane for transmetallation22 by SnC14 and TiC14, the total inefficiency of our reaction using these two Lewis acids (Scheme 1, entries 6, 7) appears reasonable if we assume that in these cases complexation of the Lewis acid can not prevent them from transmetal- lation of allyltributylstannane.

It also appeared from these preliminary experiments that the best procedure was to add the allylsilane (or stannane) to a preformed and cooled dichloromethane solution of the methylselenoacetal and the Lewis acid. As shown in Scheme 2, all the reactions of methylseleno- acetals derived from ketones and aromatic aldehydes could be performed in this manner. In the case of seleno- acetalsderived from aliphatic aldehydes (Scheme 2, entries 1,2) however, the reactions had to be conducted at room temperature, but they did not go to completion, even under these conditions, presumably because of the faster trans- metallation side reaction. Consequently, homoallylsele- nides 28 and 2b were formed in low yields from la and 1 b respectively. That transmetallation of allyltrimethylsilane could be incriminated for these low yields was also sugges- ted by the fact that i) untransformed starting selenoacetals could be isolated from the product mixtures; ii) when after 1 h of reaction of la at room temperature, a second batch of 2 eq. SnC14 / 2 eq. allyltrimethylsilane was added to the reaction mixture, t.1.c. monitoring has shown complete consumption of la within 1 h of further reaction, and the yield of isolated homoallylselenide 2a was raised to 50%. Applying the same procedure for the reaction of 11 did not improve significantly the yield in homoallylselenide 21, whereas starting from I f 61 % of homoallylselenide 2f was obtained. With a few exceptions, considerably more efficient reac- tions were observed with selenoacetals of aromatic aldehy- des (Scheme 2, entries 9-13), of aliphatic ketones (Scheme 2, entries 4-8) and of aromatic ketones (Scheme 2, entries 14, 15). These findings parallel those observed for the Lewis acid mediated reactions of selenoacetals with silyl enol ethers4 : electronic effects tending to stabilise the developing carbenium ion favour the reaction, whereas steric crowding around the electrophilic centre disfavour them. It is of interest to note that quite comparable trends were observed in the DMTSF [dimethyl(methylthio)sulfo- nium fluoroborate] mediated reactions of methylthioacetals with alIyl-n-tributylstannanea, whereas in the aluminium trichloride promoted reactions of allylsilanes with phenyl- thioacetals, the acetals derived from aliphatic aldehydes gave significantly cleaner products and in better yields than those derived from ketonesm. In the latter series the reac-

- 258 -

R', ,SeMe 2eq.R3\//\/ SiMe3 / 2 eq.SnCl4 R', ,SeMe C b C

R2 ' 'SeMe CHK12 / Conditions R ? '

1 2

Entry R3 Conditions Yield, % (syn/anti ratio) Selenoacetal 1

R1 R2

1 l a 2 l b 3 l c 4 Id 5 le 6 If 7 19 8 l h 9 l i

10 li

12 l k 13 11 14 1m 15 In

11 li

C6H 13 H PhCH(Me) H

C6H 13 CH3 C3H7 CH3

C3H7 C3H7 C2H5 C2H5

-(CH2)5- -4-B~t-(CH2)5-

C6H5 H C6H5 H

p-Me-CsH4 H

P-NOZ-C~H~ H p-MeO-C6H4 H

C6H5 CH3 p-NOn-CsH4 CH3

H H H H H H H H H

CH3 H H H H H

25"C/1 h 25"C/1 h

- 40°C/1 .5h - 40°C/5h

- 40°C/1 .5h - 40°C/2h

- 40°C/0.25h - 40°C/3 h - 40°C/4h - 40°C/2h - 40"C/4h - 40°C/2 h - 40"C/2h

- 40°C/2.5h - 40°C/1 .5h

33 32 (30:70) 69 60 28 25 60 55 48 60 (70:30) 60

1751 *

(491 * 30

72

(*) Crude yields estimated by H NMR, considerable decomposition occurs during chromatographic (Si02) purification

SCHEME 2.

tion course was also strongly dependent on the solvent used (toluene), as well as on the order of mixing of the reagents.

Besides adventitious hydrolysis of the starting sele- noacetal in the strongly acidic reaction media, two side- reactions have been identified as being operative in some cases (Scheme 3).

From the reaction of selenoacetal 1 m the bis-allyla- tion product 4-methyl-4-phenyl-l,6-heptadiene has been isolated in about 10%. Although in the present context this is a relatively minor reaction path, Lewis acid activation of suitably substituted selenides can lead to very efficient transformations3'. The second side-reaction detected in the product mixture obtained from selenoacetal If basically

l m

CHzCl2 / -40 "C

- b)

MeSeXSeMe n-Pr n-Pr

If

49 % 2m

+ & /

10 %

+

(6-8 %)

SCHEME 3.

- 259 -

consists of the demethylation of the SeMe group during the allylation reaction as featured in Scheme 3b. Even though only 6-8% of the produced homoallylic silylselenide was detected (GC/MS) it could have been formed in larger amounts and decomposed during w 0 r k - u ~ ~ ~ .

Presumably due to their diminished Lewis basicity, phenylselenoacetals do not react with allyltrimethylsilane. For example, no trace of homoallylphenylselenide was for- med from 1,l -bis(phenylseleno)-4-t-butylcyclohexane and allyltrimethylsilane under neither one of the following condi- tions : SnC14 / CH2C12 / - 40°C; AIC13 / CH2C12 125°C or AgC104 / CH3CN 125°C.

Our preliminary experiments have shown that sele- noacetals can also be transformed into homoallylic seleni- des by reacting them with allylstannanes in the presence of non-transmetallating Lewis acid such as BF3 0 OEt2 or ZnCln, at the condition of conducting the reaction at room temperature and for longer periods of time (Scheme 1, entries 8, 9). A few additional results on some aspects of this reaction are displayed in Scheme 4 : i) the yields in homoallyl selenides are roughly comparable to those obtai- ned with allyltrimethylsilane as nucleophile (Scheme 2); ii)

1 , l -bis(phenylseleno)-4-t-butylcyclohexane leads to the corresponding homoallylselenide in reasonable yield on reaction with allyltributylstannane (Scheme 4, entry 13); iv) the reaction of selenoacetal 1 i with crotyltributylstannane producing homoallyl selenides 2i' proceeds with significant stereoselectivity, the syn/anti isomer ratios varying from 60/40 to 95/5, depending on the reaction conditions (Scheme 4, entries 2-8).

These values can be compared to those observed in related reactions such as those of silyl end ethers with [0, 01 a ~ e t a l s ~ ~ and those of allyltrirnethyl~ilane~~ or of allylstan- n a n e ~ ~ ~ with [S,S] acetals. Particular examples of reac- tions of thioacetals leading to much higher diastereoselec- tivity have been r e p ~ r t e d ~ ~ ~ ~ a s well as cases without a n p or showing very low sele~tivities~~.

The reaction of selenoacetal 1 b with allyltrimethylsi- lane (Scheme 2, entry 2) and with allyltributylstannane (Scheme 4, entry 10) gives inverted diastereoisomer ratios (syn/anti = 30/70 and 40160, respectively) because in these cases stereocontrol arises from the presence of a chiral center in the electrophilic partner.

R3 R3

* R'+ +

R', ,SeR

R2 SeR Soh. I T "C / t (h)

R3- SnBu3 I L.Ac. .c\ 1 R2 SeR 2 R2 SeR

T"C1t (h) syn:anti Yield ("h) Entry R' R2 R3 R LewisAcid Solvent

1 2 3 4 5 6 7 8 9

10 11 12 13

Ph H Ph H Ph H Ph H Ph H Ph H Ph H Ph H

C-CsH11 H PhCH(Me) H

n-Pr n-Pr 4-t-B~-(CH2)5- 4-t-B~-(CH2)5

H Me BF3oOEtn CH2C12 Me Me BFsoOEt2 CH2C12 Me Me BF30OEt2 CH2C12 Me Me BF30OEt2 CH3N02 Me Me ZnCln CH2C12 Me Me AIC13 CsH5CH3 Me Me AIC13 CH2C12 Me Me AIC13 CH3NOdCH2C12 (1 :2) H Me AIC13 CsH 5C H 3

H Me AIC13 C6H5CHs H Me BF30OEt2 CH2C12 H Me BF30OEt2 CH2C12 H Ph BF3oOEta CH2C12

2011 6 20/16 20172 2016

20124 - 4012 - 4012 - 7814 2012 2014

2011 6 2013 2013

95:5 67:33 70:30 60:40 60:40 67:33 80:20

40:60

2i 49 2i' 12 2i' 52 2i' 25 2i' 44 2i' 46 2i' 50 2i' 12 20 78 2b 13 2f 25 2h 30 2p 47

SCHEME 4.

aluminium trichloride appears to help the reaction to occur, but its efficiency seems to depend on the structure of the

EXPERIMENTAL PART All reactions were carried out under argon, in sep- -

starting selenoacetal used as well as on the reaction conditions (Scheme 4, compare entries 6-1 0); iii) in contrast with its lack Of reactivity towards allyltrimethylsilane,

tum-fitted glassware. Dry dichloromethane and nitrome- thane were obtained by distillation from P2O5, toluene was distilled from sodium. Selenoacetals have been prepared according to published procedures%.

- 260 -

NMR spectra were recorded on JEOL PMXGOSi, JEOL FXSOQ, JEOL EX90 or JEOL EX400 using TMS as internal standard. Mass spectra were recorded on a Hewlett-Packard 5995A spectrometer.

Reactioti of selerioacetals with al!\,lmnriiemli~~lsilarie proriioted by Sri C14 (Procedure A ) Synthesis of 4-methylseleno-1 -decene (2a)

In a two-necked round-bottom flask under argon, 520 mg of SnC14 (2.0 mmol) were dissolved in 5 ml dry CH2C12, then a solution of 290 mg (1.0 mmol) of 1,I-bis- (methylse1eno)heptane l a in 2 ml of dry CH2C12 was slowly injected on the Lewis acid at room temperature, the reac- tion mixture turning yellow. After 5 min. a solution of 228 mg of allyltrimethylsilane (2.0 mmol) in 2 ml of dry CH2C12 was added. The yellow color disappeared and the reaction medium became turbid. After 1 h of reaction 20 ml of a 1 N KOH solution was added and the mixture was transferred into a separatory funnel and extracted with 20 ml ether. The organic layer was washed with brine, dried over MgS04, filtered and concentrated under vacuum yielding 283 mg of crude product which was purified on preparative t.1.c. (eluent : ether/pentane 2/98) (Rr = 0.6) yielding 76 mg (33%) of pure 2a.

Reactior i of seler ioacetals with allyltiibi rtylstar iri at i e pror i i oted by BF3 OE9 (Procedure B ) Synthesis of 1 -phenylseleno-1 -allyl-4-t-butylcyclohexane

In a two-necked round-bottom flask under argon, 450 mg (1 .O mmol) of 1 , I -bis(phenylseleno)-4-t-butylcy- clohexane 1p and 370 mg (1.1 mmol) of allyltributylstan- nane were dissolved in 3 ml of dry CH2CI2 and 0.13 ml (1 .I mmol) of BF3 OEt2 was injected at room temperature. After 3h, 10 ml of saturated sodium bicarbonate solution was added and the mixture was extracted with 20 ml ether, washed with brine, dried over MgS04, filtered and concen- trated under vacuum yielding 980 mg of crude product. This crude material was purified by preparative t.1.c. (eluent : pentane) yielding 158 mg (47%) of homoallylic selenide 2p (Rt =0.5).

The same procedures (A or B) were used for the syntheses of the other homoallylselenides.

4-Metliylselerio-I-decarie 2a37 'H NMR (60 MHz, CDC13,d in ppm) : 0.88 (3H, t, J =6Hz); 1.08-1.75 (IOH, br); 1.93 (3H, s); 2.42 (2H, m); 2.8 (1 H, m); 4.90-5.20 (2H, m); 5.8-6.0 (IH, m). 13C NMR (100 MHz, CDC13,d in ppm) : 2.3, 14.0,22.6,27.6, 29.1, 31.8, 34.7, 39.7, 41.1, 116.4, 136.4.

(2P)

2-Plietiyl-3-tiietliylsele~io-5-li~etie 2b 'H NMR (400 MHz, CDC13, d in ppm) : 1.39 (anti), 1.40 (syn) (3H, d, J = 5.1 Hz); 1.76 (anti); 1.78 (syn) (3H, s); 2.2-2.5 (2H, m);2.8-3.1 (2H,m);5.0-5.1 (2H,m);5.8-6.0(lH,m);7.1-7.3 (5H, m). 3C NMR (100 MHz, CDC13, b in ppm) : 8.8, 13.7, 27.4,28.5,

29.3, 37.6, 48.8, 116.9, 125.5, 125.8, 128.0, 135.5, 149.2.

4-Metliylseletio-Cmetliyl-I-decetre 2~ 'H NMR (60 MHz, CDC13, 6 in ppm) : 0.88 (3H, t, J =6Hz); 1.08-1.68 (IOH, br); 1.88 (3H, s); 2.33 (2H, dd, JI =6HZ, J2=0.5Hz); 4.82-5.28 (2H, m); 5.53-6.23 (1 H, m).

37

CMetliylseler 10-4-1 i i ethyl- I -1iepter I e 2d H NMR (90 MHz, CDC13,6 in ppm) : 0.93 (3H, t, J = 7Hz); 1

1.30 (3H, s); 1.46 (2H, q, J =7Hz); 1.77 (3H, s); 2.30 (2H, d, J = 8Hz); 4.85-5.25 (2H, m); 5.30-6.30 (1 H, m).

4- Metliylseler to-4-etlyl- 1-11 ever 1 e 2e 'H (90 MHz, CDC13, 6 in ppm) : 0.93 (6H, t, J = 7Hz); 1.57 (4H, m); 1.83 (3H, s); 2.32 (2H, dd, JI =8Hz, J2=0.5Hz); 4.85-5.30 (2H, m); 5.36-6.33 (IH, m).

4-Metliylselerio-4-ri-propyl-I-heptarie 2f 'H NMR (60 MHz, CDC13,d in ppm) : 0.90 (6H, t, J =7Hz); 1.20-1.60 (4H, m); 1.84 (3H, s); 2.31 (2H, d, J=6Hz); 4.90-5.32 (2H, m); 5.65-6.25 (IH, m). M.S. 234 (M'"), 194 (-C3H5), 139 (-CH3Se).

I-Metliylselerio-I-allylcycloliexaiie 29 'H NMR (90 MHz, CDC13, 6 in ppm) : 1.0-2.0 (IOH, br); 1.82 (3H, s); 2.35 (2H, d, J=6Hz); 4.81-5.30 (2H, m); 5.43-6.40 OH, m). M.S. 218 (M'"), 177 (-C3H5), 123 (-CH$e). Calculated C : 55.29, H : 8.35; found C : 55.80, H : 8.50.

l-Metliylseletio-I-allyl-4-t-bir~lcycloli~atie 2h 'H NMR (90 MHz, CDC13,6 in ppm) : 0.70 (9H, s); 1.07-2.03 (9H, br); 1.80 (3H, s); 2.33 (2H, d, J =7HZ); 4.83-5.30 (2H, m); 5.67-6.45 (IH, m). M.S. 274 (M'"), 233 (-C3H5), 179 (-CH3Se). Calculated C : 61.52, H : 8.35; found C : 61.44, H : 8.50.

I-Metliylselerio-I-pheriyl-3-birterie 2i 'H NMR (60 MHz, CDC13,d in ppm) : 1.58 (3H, s); 2.51 -2.84 (2H, m); 3.86 (IH, t, J =8HZ); 4.83-5.05 (2H, m); 5.35-6.33 (IH, m); 7.21 (5H, br, s). M.S. 226 (M'"), 185 (-C3H5), 131 (-CH3Se). Calculated C : 58.67, H : 6.27; found C : 58.14, H : 6.30.

I-Metliylseletio-l-plietiyl-2-tiietliyl-3-birtene 2i' ' H NMR (90 MHz, CDC13,d in ppm) : 0.92 (anti) (d, J =7Hz); 1 . I8 (syn) (d, J = 8HZ) (3H); 1.59 (anti); 1.67 (syn) (3H, s); 2.4-3.0 (2H, m); 3.70 (anti) (d, J=IIHz); 3.78 (syn) (d, J=8Hz) (IH); 4.71-5.19 (2H, m); 5.40-6.30 (IH, m); 7.06-7.32 (5H, m).

I-Metliylseletio-1-p-tolyl-3-birterie 2j 'H NMR (60 MHz, CDC13, d in ppm) : 1.76 (3H, s); 2.30 (3H, s); 2.51-2.84 (2H, m); 3.93 (IH, t, J =8HZ); 4.80-5.27 (2H, m); 5.36-6.13 (IH, m); 7.10 (5H, br, s). M.S. 240 (M'"), 199 (-C3H5), 145 (-CH3Se), 128. Calculated C : 60.25, H : 6.74; found C : 60.44, H : 6.87.

I-Metliylselerio- I-p-ariisyl-3-birterie 2k 'H NMR (60 MHz, CDC13,d in ppm) : 1.66 (3H, s); 2.50-2.90 (2H, m); 3.75-3.85 (1 H, m); 3.73 (3H, s); 4.85-5.30 (2H, m); 5.65-6.45 (1 H, m) ; 6.66-7.33 (4H, m).

1- Metliylseleno- I-p-riitropli enyl-3-biiterte 21 'H NMR (400 MHz, CDC13, 6 in ppm) : 1.83 (3H, s); 2.76 (2H, t, J =8Hz); 4.03 (IH, t, J =8Hz); 4.90-5.20 (2H, m); 5.45-5.95 (IH, m); 7.45 (2H, d, J=13Hz); 8.15 (2H, d,

13CNMR(100MHz,CDC13,6inppm):4.5,39.8,42.3,117.7, J = 13Hz).

124.0, 128.6, 134.8, 146.7, 150.3.

- 261 -

2-1itetltylseletto-2-pltettyl-4-pe1tterte 2m 'H NMR (60 MHz, CDCb, b in ppm) : 1.63 (3H, s); 1.80 (3H, s); 2.80 (2H, d, J =6Hz); 4.83-5.20 (2H, m); 5.45-6.07 (1 H, m); 7.10-7.63+(5H, m). M.S. 240 (M O ) , 199 (-C3H5), 145 (-CH&e). Calculated C : 60.25, H : 6.74; found C : 60.43, H : 6.89.

2-Metltylselert0-2-p-1titroplteityl-4-pe1tterte 2n H NMR (60 MHz, CDC13,d in ppm) : 1.70 (3H, s); 1.83 (3H,

s); 2.66-3.00 (2H, m); 4.87-5.25 (2H, m); 5.30-6.00 (1 H, m);

1

7.56(2H,d, J=12Hz); 8.10 (2H,d, J=12Hz).

I-Metltyl~elett0-I-~y~l0h~l-3-biitette 20 'H NMR (90 MHz, CDC13, d in ppm) : 1 .O-2.0 (9H, m); 1.93 (3H, s); 2.30-2.50 (3H, m); 4.96-5.16 (2H, m); 5.54-6.00 (lH, m).

l-Pltertylsele1to-I-allyl-4-t-bii~lcycylcyclolte 2p 'H NMR (90 MHz, CDCh b in ppm) : 0.9 (9H, s); 0.9-2.0 (9H, br); 2.17 (2H, d, J =7Hz); 4.73-5.17 (2H, m); 5.60-6.40 (1 H, m); 7.03-7.73 (5H, m). M.S. 336 (M'"), 234, 178 (-CsH&), 123. Calculated C : 68.04, H : 8.41; found C : 68.12, H : 8.43.

ACKNOWLEDGMENT We thank the "lnstitut pour I'encouragement de la Recherche dans I'lndustrie et I'Agriculture" (I.R.S.I.A.) for supporting this work (fellowship to B.H.).

REFERENCES AND NOTES

1. L. Hevesi, S. Desauvage, 8. Georges, G. Evrard, P. Blanpain, A. Michel, S. Harkema and G.J. van Hummel, J. Ant. Clteiit. Soc., 1984, 106, 3784.

2. K.M. Nsunda and L. Hevesi, J. Cltnn. SOC., Citern. Cotntniin., 1985, 1000.

3. L. Hevesi and K.M. Nsunda, Tetrahedron Lett., 1985,26, 6513.

4. K.M. Nsunda and L. Hevesi, Tetraltedrott Lett., 1984,25,

18.

19. 20.

21.

22.

23.

24. 25.

26.

27.

28.

29. 30.

31.

32.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16. 17.

4441. C.C. Silveira, J.V. Comasseto and V. Catani, Syttth. Contntiut., 1985, 15, 931. L. Hevesi and A. Lavoix, Tetrahedrort Lett., 1989, 30, 4433. 34. K.M. Nsunda and L. Hevesi, J. Citein. SOC., Citetlt. Coininiin., 1987, 151 9. 35. T. Kataoka, M. Yoshimatsu, H. Shimizu and M. Hori, Tetrahedron Lett., 1991, 32, 105. M. Yoshimatsu, T. Sato, H. Shimizu, M. Hori and T. Kataoka, J. Otg. Cltetn., 1994, 59, 101 1. C.C. Silveira, E.J. Leonardo, J.V. Comasseto and M.J. Dabdoub, Tetrahedrott Lett., 1991, 32, 5741. M. Renard and L. Hevesi, Tetraltedron Left., 1983, 24, 391 1. M. Renard and L. Hevesi, J. Cheni. Soc., Citetit. Cointniirt., 1986, 688. L. Hevesi, M. Renard and G. Proess, J. Cltertt. SOC., Cltent. Cotnntiitt., 1986, 1725. G. Proess, D. Pankert and L. Hevesi, Tetraltedron Lett., 1992, 33, 269. L. Hevesi, G. Proess, A. Lazarescu-Grigore, Synthetic Metals, 1993, 59, 201. G. Proess and L. Hevesi, J. Mol. Cat., 1993, 80, 395. M. Yoshimatsu, T. Yoshiuchi, H. Shimazu, M. Hori and T. Kataoka, Syttlett, 1993, 121.

33.

36.

37.

Preliminaryresults have been published : a) B. Hermans and L. Hevesi, Tetrahedron Lett,, 1990, 31, 4363; b) A. Krief, E. Badaoui, W. Dumont, L. Hevesi, B. Hermans and R. Dieden, Tetrahedrort Lett., 1991, 32, 3231. K.M. Nsunda, PhD Thesis, Namur, 1988. G.E. Keck, D.E. Abbott, E.G. Bolden and E.J. Enholm, Tetrahedron Lett., 1984,25, 3927. Y. Naruta, Y. Nishigaishi, K. Maryama, Tetruhedrort, 1989,45,1067. Y. Nishigaisi, A. Takuwa, Y. Naruta, K. Maruyama, Tetrahedron, 1993, 49, 7395. S.E. Denmark, N.G. Almstead, Tetrahedron, 1992, 48, 5565. M.T. Reetz, A. Giannis, Syttth. Coinmiin., 1981, 11, 315. I. Mori, P.A. Bartlett, C.H. Heatcock, J. Am. Citein. Soc., 1987,109,7199. a) H. Mayr, G. Hagen, J. Client. SOC., Chern. Cornmutt., 1989,91; b) G. Hagen, H. Mayr, J. Ant. Chern. Soc., 1991, 113,4954; c) J. Bartl, S. Steenken, H. Mayr, J. Am. Cltent. SOC., 1991, 113, 7710. a) G.E. Keck, M.B. Andrus, S. Castellino, J. Am. Client. SOC., 1989, I l l , 8136; b) S.E. Denmark, T. Wilson, T.M. Willson, J. Ant. Cheiit. SOC., 1988, 110, 984; c) S.E. Denmark, E.J. Weber, T.M. Wilson, T.M. Willson, Tetraltedrott , 1989, 45, 1053. S.E. Denmark, T.M. Willson, J. Am. Chent. SOC., 1989, 111,3475. B.M. Trost, T. Sato, J. Am. Citein. Soc., 1985, 107, 719. A. Mann, A. Ricci, M. Taddei, Tetrahedron Lett., 1988,29, 61 75. a) Activation of a-(2-pyrrolyl)-a-allyl selenides, see ref. 12-16; b) Activation of tertiary selenides : A. Krief, J.-L. Laboureur, W. Dumont, D. Labar, Bull. SOC. Chitn. Fr., 1990, 127, 681; c) Activation of benzylic selenides : A. Krief, J. Bousbaa, M. Hobe, Syttlett, 1992, 320; A. Krief, B. Kenda, P. Barbeaux, E. Guittet, Tetrahedron, 1994, 50, 7177. Silylselenides in general are both oxygen and moisture sensitive compounds (see for example : D. Liotta, J. Johnston and G. Zima, Tetrahedron Lett., 1978, 5091. a) S. Murata, M. Suzuki, R. Noyori, J. Am. Chent. SOC., 1980, 102, 3248; b) S. Murata, M. Suzuki, R. Noyori, Tetrahedron, 1988, 44, 4259. K. Saigo, Y. Hashimoto, N. Kihara, K. Hara and M. Hasegawa, Client. Lett., 1990, 1097. T. Takeda, Y. Kaneko and T. Fujiwara, Tetrahedron Lett., 1986,27,3029. M. Clarembeau, A. Cravador, W. Dumont, L. Hevesi, A. Krief, J. Lucchetti, D. Van Ende, Tetruhedron, 1985,4I, 4793. M. Clarembeau, J.L. Bertrand, A. Krief, 1984, 24, 125.

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