Tetrahedron Letters,Vol.28,No.39,pp 4611-4614,1987 Printed in Great Britain

oo4o-4039,'87 $3.00 + .oo Perqamon Journals Ltd.

STUDIgSON EHAMIDKS.PART- 1 :PROTOCREUICAL REARRAZ-S OF N-AROYLCARBAZOLRS

Somnath Ghosd, Taxma Kurpor Ik8, Diptendu Bhusan Datta and Sweeta Mehta Department of Cheuistry, Jadavpur University, Calcutta 700032, IWDIA

Abstract : The synthesis of l- and 3-aroylcarbazoles has been achieved by the photolysis of N-aroylcarbazoles alongwith the formation of carbazole and the rearranged product ratio is wavelength dependent.

The photochemical reaction of ensmides, apparently as first demonstrated by Eschenmoser et al' -- in early aixties, has received considerable attention in recent years for the synthesis of a

large variety of heterocycles, alkaloids and aza-steroids and several excellent reviews 2-5

have been published on this methodology. An extensive study of the literature revealed that

the lone pair of the nitrosen atom of the enamide functionality, excepting in a few cases6, is

not involved in the aromaticity of the parent substrate. We, therefore, envisaged to make a

systematic study of the latter class of enamides with N-aroylcarbazoles[z(a - d)] as

representative examples, since their photochemical reaction has not been reported so far and

the results obtained thereof may be useful for our continuing interest for the synthesis of

alkaloids7 - 9.

Irradiation of a methanolic solution (350 ml) of N-benzoylcarbazole (20) (1.0 6; 3.69

mmole), prepared by the benzoylation of carbazole (1) with sodium hydride in benzene - DKF

mixture (Scheme - 1) in a quartz vessel (i~rrsion type) by a low pressure mercury lemp (16~‘

> 9O$ 254 1118, Applied Photophysics Ltd, Rngland) with iodine as oxidant under nitrogen

atmoephere for 44 hr. (monitored by TLC) neatly afforded, after usual workup and chromatography

(silica gel, 60 - 120 mesh, BDH), crrbazole u (0.36 6; 5896) and the [1,5]-benzoyl nigrated

product, 3-benzoylcarbazols (La) (0.30 6; TO%), mp. 201-202' (acetone - petroleum ether)

(1it.'O mp. 203-205'). IR (KBr) s_ 3240 (b), 1640 (8) cm-'; 'II NMR (100 MHz, d6 - DKSO)b

7.20 (lH, m), 7-28-7.96 (9E, m), 8.20 (lH, d, J-8.0 Hz), 8.58 (1% s) and 11.76 (lR, 8, D20 -

l xchangeable)g MS m/z 271 (M'+, 43$), 270 (M'+ - H, lOO$). The photochemical reaction was found to be consistent for other substrates [l(b - d)]

leading to the fornation of 1 and $b - d) in vary- yields (Table - 1).

We next turned our attention to observe the photochemical behaviour ofz(a - d) by

irradiatw under the same oxidativo condition using a medium pressure mercury 1-p (4OOW, A_

365-366 M). While the photolysis of $a - o) afforded the hitherto unknown 11 l-aroylcarbazoles

Ma - c)] in addition to land $a - c) in reasonable to good yields (Table - 1), W-(3-nitro-

benzoyl)-oarbazole @d) yielded odly 1, Id and a compoti (s) of UllknOm atNCtm*p ~Po 138'

(acetone - petroleum ether), IR (KBr) 3, 3010, 2960, 1720 (vB), 1500, 1430, 1405 cm-'; 'R NMB

(100 t4kt5, d6 - DMsO)h 3.84 (a) and 8.08 (a) with an inte&ration ratio of 3r2.

The genesis of the aroyl migrated products is analogous to the Photo-Fries RearrPryement 12

(Scheme - 2) exceptinS the fact the substrates [z(a - d)] exhibit, only in the presence of low

pmm*ue mercury lamp, on exclusive [1,5]-migration, for reason8 not so clear, of aroy drouP

from nitrogen to the C3 position of the oromatic ring. Such type of [1,5]-migration is well

documented in the literature 13.14 s The distinct inertness of the substrate (1) to undergo photocyclisation so as to afford

4611

9-indolo-[J,Z,l-de]-phenanthridin-q-one" under the oxidative photolytic condition may be

rationalised by considering the mechanism of enamide photocyclisation 15 - 17 which requires

the participation of the lone pair of nitrogen atom in the transition state so as to induce a

[2+2+2]-cycloaddition reaction. In the present case such participation of lone pair would

incur considerable amount of the loss of resonance energy of the parent compound (2). As a

result the photocyclisation nor becomes competitive with the alternate gathnays leading to the

formation of 2, 1 and 4.

Thus we conclude the oxidative photolysis of N-aroylcarbazoles leads to [?,?I- or [1,5]-

aroyl migration from nitrogen to the ring, the product ratio being wavelength dependent and

offers an easy access to the synthesis of l-aroylcarbazole, difficult to prepare by conven- 11 tional chemical procedures ~

SCHEME-l

a:R,=R2=R3=H; b: R,=CI;R2=R3=H;

c: R,=R3=H; R2=OCH3; d: R,=R2=H; R3=N02 Ar =

SCHEME-2

4 (a-c)

&to-c)

Path B

Ar : Phenyl/Aryl

4613

TABLE - 1 : RESULTS OF OXIDATIVE IRRADIATIOM OF N-AROYLCARBAZOLES 2(a - d)

Entry N-Aroyl- Lanp(W)/ Carbazole (1) 3-Aroylcarbazolc (I)" I-broylcarbazole (4):

carbazole (2)' Time(h) Yield in mg($)' Y.P.(Solvent)b IR(KBr) M.P.(Solvent)b IR(KBr)

M.P.(Solvent)b Yield in ag($)' (cm-') Yield in mg($)' (cm-')

1. a : 98'(aq. E) 161 44 360( 58) 201-202'(A - P) 3240(b) -

1it.18 lit." 1640(s)

mp. 98' mp. 203-205’

300(3(J)

4Ow 10 200(32) 202'(A - P) 139O(A - P) 3410(h)

50(5) 150(15) 3380(s)

1627(w)

2. k : 95’(B - P) 16/ 30 lOO( 18) 198-200°(A - P) 33@xvs) -

200(20) 1645(s)

400/ 11 150(27) 202’(A - P) 181°(A - P) 3400(m)

150(15) 300( 30) 1630(m)

3. 2 t lll'(B - P) 16/ 29 200(36) 186-188’(A - P) 3220(b)

50(5) 1640(r)

4001 10 190(35) 190°(A -P) 141°(A -P) 3420( sh)

150(15) 150(15) 3400(m)

1637(a)

4. a I 151°(B - P) 16/ 32 350(66) 195O( crude) -

20

4w 12 200(38) 205’(A - P) 3240(b)

60(6) 1650(m)

a :

b:

c :

Compounds z(b - cl), l(b - d) and &(a - C) are all new and give satisfactory

elemental analyses (C, + 0.2%; H, + 0.446 and N, + 0.346).

Spectral data for l(b - d) and 4(a - c) are given in Note 19.

Ylelting points are uncorrected (recorded in H2S04 bath in open capillary tube)

and solvent abbreviations are : A - Acetone; B - Benzene; E - Ethanol and

P - Petroleum ether (60' - 80').

Yield refers to the combined amounts of the first and second crop of crystallised

product obtained after chromatography.

The authors rish to thank Dr. P. Ghoshdastider, IICB,

measurements and to Mr. B. Bhattacharya, JU, Calcutta

Financial assistance (to SNG) from the authorities of

is also acknowledged.

Calcutta for 'H NMR spectral

for microanalytical results.

Jadavpur University, Calcutta

ah

1.

2.

3.

4.

5.

6.

7*

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

4

REFERENCES AND NOTES

E. Bertele, B. Boos, J.D. Dunitz, F. Elsinger, A. Pachenmoser, I. Falner, R.p. Gribi R. Gschwend, E.F. Meyer, M. Pesaro and R. Schtffold, u. Chem., & 393 (1964); ' m. Chem. _ IntO Ed. g&., 1, 490 (1964).

M. Shamma, "The Isoauinoline Alkaloids", Academic Press, New York, pp 197 ff (1972). - I I. Einomiyo, Heterocycles, 2, 105 (1974).

T. Kametani and K. Fukaoto, &. Chcm, I&., 2, 212 (1972).

G.R. Lenz, Synthesis, 409 (1978).

P. Bouchet, C. Joncherny, R. Jacquisr and J. Elaero, J. Heterocycl, a., and references cited therein.

2, 625 (1978)

A. Chatterjee and S.N. Ghosh, Synthesis, 818 (1981).

A. Bansrji, D. Bandyopadhyay, K. Sarkar, A.K. Siddhanta, S.C. Pal, S.N. Ghosh, K. Abraham and J.N. Shoolery, Phytochemiatq, 2& 279 (1985).

S.N. Ghosh, D.B. Datta and N. Sun, Synth. Commun., u1, 299 (19B7).

W.B. Hunter and S.F. Darling;, J. Amer. Chem. e., 2, 4183 (1931).

S.G.P. Plant and M.L. Tomlinson, 2. m. a., 2188 (1932).

D. &llus, Advan. Photochem., 2. 109 (1971).

B.W.- Lardelli, H.J. Rosenkranz, H.J. Hansen, H. S&mid, B. Blank and H. Fischer, Holv. Chim. m., -- %, 2428 (1973).

A.E. Lyubrrakaya, G.D. Peuli, V. Bren, Yu.A. Zhdanov, M.I. Knyazhmskii, V.I. Minkin and L.P. Otekhnovich, 2. a. m., 2, 918 (1976).

N.C. Yang, A. Shani and G.R. Lenz, J. Amer. Chem. *., 88, 5369 (1966).

P.C. Cleveland and O.L. Chapman, J. Chew Sot. Chen. Common., --- 1064 (1967).

G.R. Lenz, 2. a. m., Q, 2201 (1976).

H.T. Clarke, "A Ha&book of Organic Amal ale : Qualitative and Quantitative'*, Edward Arnold, London, 4 th. Ed., pp 207 1949). --+ -

I-Benzoylcarbazole (Aa) : Smrx 3410 (sh). 33m (s), 1627 (vs), 1615, 1590, 1565, 1490,

1445, 1315, 1265, 1220, 1115, 965, 840, 750, 720, 700 cm-'; 'II E~!R (100 MHZ, d6 - DMSO)

6 7.24-7.84 (IOH, m), 8.24 (lH, d, J=S.O Hz), 8.52 (lH, d, JIB.0 Hz), 11.84 (IH, s, ~20 -

exchangeable); Ms m/z 271 (It’+, 21%), 270 (XC+ - H, low), 253 (26%). 240 (72$), 193 (9@),

166 (98qb), 165 (Se%), 148 (98%), 139 (74%), 105 (96%). 77 (9%).

J-(P-Chlorobenzoyl)-carbaaole (lb) : 'H NKR (100 MKz, d6 - DMSO)6 7.24 (IH, m), 7.46-7.64

(7rr, m), 7.80 (lH, d, J,=B.o Hz, J2=2.0 Ifz), 8.20 (lH, d, J-8.0 Hz), 8.55 (lH, s), 11.64

(1% 8, D20 - exchangeable); MS D/Z 305 (MS+, 44%), 149 (lo@).

1-(2-Chlorobenzoyl)-carbazole (Ab) : 'H NKR (100 MRz, d6 - DMSO)~ 7.17-7.65 (8~. m), 7.81

(lH, d, Jm8.0 Hz), 8.25 (lH, d, J=8.0 Hz), 8.53 (la, d, J18.0 Hz), 12.02 (IH, a, D20 -

exchangeable).

- 4-Methoxybenzoyl -carbazole (AC) : 'H NMR (100 MHz, d6 - DMSO)& 3.88 (3H, a), 7.13

(2H, d, J-8.0 Hz), 7.20-7.64 (5H, II), 7.80 (2H, d, Jg8.0 Hz), 8.24 (1H, d, J=B.O Hz), 8.56

(lH, a), 11,75 (lH, 8, D20 - exchaqeable); MS m/z 301 (la*+, IO(@), 300 (M'+ - 8, 78$),

270 (75%, 195 (72$), 166 (9496)s 130 (8496). 77 (21%).

l- (4-Methoxybenzoyl)-oarbazole (kc) : ‘H NMR (100 MKz, d6 - DMSO)6 3.85 (3H, a), 7.14

(2H, d, J=lO Hz), 7.20-7.72 (5H, r), 7.83 (2B, d, J,=lO.O Hz, J2-2.0 Hz), 8.20 (IR, d,

J-8.0 Hz), 8.44 (la, d, J-8.0 Hz), 11.68 (lH, 8, D20 - exchangeable).

3-(3-Nitrobenzoyl)-carbazole (ld) : 'H NMR (100 M&s, d6 - DMSO) 6 7.18-7.80 (4H, m), 7.91

(2H, d, Jz10.0 Ha), 8.22 (2H, d, J,-8.0 k, J,-3.0 Hz), 8.48 (2H, m), 8.64 (lH, s), 11.84

(lH, s, D20 - axchamgeable).

(Received in UK 19 June 1987)