Pergamon

0040-4039(95)00099-2

Tetrahedron Letters, Vol. 36, No. 10, pp. 1605-1608, 1995 Elsevier Science Ltd

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[4~+2~]Cycloadditions of o-Quinones to Fulvenes: A Facile Synthesis of Bicyclo[2.2.2]Octen-7,8-Diones #

Vijay Nair *a Sasi Kumar a and Paul G. Williard b

aOrganic Chemistry Division, Regional Research Laboratory,

Trivandrum-695 019, INDIA.

bDepartment of Chemistry, Brown University,

Providence, RI, 02912, USA.

Abstract: 3,5-Di-tert-butyl-, 4-tert-butyl-, and 3-methoxy-o-benzoquinones have been shown to

undergo thermal cycloaddition to symmetrical and unsymmetrical fulvenes to give

bicyclo[2.2.2]octen-7,8-diones in high yields.

o-Quinones are an important class of compounds and their reactivity profile in cycloaddition

is quite interesting. 1 Potentially they can function as carbodienes, heterodienes or dienophiles in

Diels-Alder reactions. Although a number of investigations on Diels-Alder reactions involving

o-quinones have been reported 2-7, questions.on the reactivity profile of these compounds remain

unanswered. In this context we were interested in uncovering the reactivity of o-quinones towards

fulvenes. In such cases, either the quinone or the fulvene can function as the diene or the

dienophile. Additionally, the possibility of higher order cycloadditon also exists. There has been

some work on the cycloaddition of o-quinones to fulvenes, but for the most part, this is concerned

with the cycloaddition of tetrachloro-o-benzoquinone with 2,3,4,5-tetraaryl- and 6,6-

dimethylfulvenes. 8,9 In these cases the quinone functions as a heterodiene leading to inverse

electron demand Diels-Alder reaction. In addition to the [4+2]cycloaddition, products arising from

[6+4] addition with the fulvene acting as the 6= component were also isolated. There are isolated

examples of the [4+2]cycloaddition of methyl substituted o-quinones with diarylfulvenes in which

the quinone participates as the carbodiene, lo

As a part of a comprehensive programme on the cycloaddition of o-quinones, we have

investigated the reactions of 4-tert-butyl-, 3,5-di-tert-butyl- and 3-methoxy-o-benzoquinones with a variety of symmetrical and unsymmetrical fulvenes. Our preliminary results indicate that the

cycloaddition occurs smoothly with the quinone functioning as the carbodiene and the fulvene as the dienophile. Predominently endo addition leading to bicyclo[2.2.2]octen-7,8*diones in high

yields were observed.

#Dedicated to the memory of Professor Peter Yates who passed away on November 16, 1992.

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1606

a R2 = H, R3 = Ph

RI a R = RI = CMe3 R2. ,~ .R3 b R2 = H, R3 = p - M e O P h

~ ~ b R = O M e , R I = H c R 2 f R 3 = p h

c R=H, RI=CMe3 ~ d R 2 =H,R 3 = R e R2 = R3 = - ~

I II

The quinones were prepared by the oxidation of the corresponding catechols11,12 and the

fulvenes were obtained by the condensation of cyclopentadiene with the corresponding aldehyde or ketone.13,14

The cycloaddition can be illustrated by the following example (Eqn.1).15

Me3C~Me~

O fi~OMe o~CMe3

H ~ / t ~ TOLUENE " 3C ~ + (Eqn.I) ~ SEALED TUBE Me

II0oC, 5 h, 56% Me ch'~4~ ~ ~, ~ - v H

2

The product 2 was characterized by elaborate spectral analysis and ultimately by single crystal-X-ray analysis. 16

C(1U

I Ct~

~ ' t ~ Cl31

X-Ray Crystal Structure of 2

1607

Similar results were obtained with the quinones la-c and the fulvenes Ila-e and these are

summarised in Table 1.

R ' ~ ~ + R2~ 3

R

O H

R 1 2

1-10

Table 1. Cycloaddition Reactions of o-Quionones to Fulvenes.

Entry Quinone Fulvene Condition M p o c Yield %

1 R = R 1 = CMe3 R2 = H, R3 = Ph Toluene,110oc, 190-192 82 Sealed tube, 24 h

2 ,, R2 = H, R3 = P-OMePh Toluene,110oc, 178-180 56 Sealed tube, 5 h

3 ,, R2 = R3 = Ph Toluene,110oc, 178-180 90 Sealed tube, 12 h

4 ,, R2 = H, R 3 = ~ Benzene, 100oc 169-171 91

Sealed tube, 2 h

5 ,, R2 = R3 = - - ~ Toluene, __ 62 Reflux, 4 h

6 R = OMe, RI. = H R2 = H, R3 = Ph Benzene, 166-168 56 Reflux, 30 min

7 " R2 =H, R 3 = p-OMePh " 170-172 50

8 ,, R2 = R 3 = Ph " 175-177 70

,, R2 = H, R3 = - ~ ~ . 9 138-140 63

10 ,, R2 = R3 =--<~ " __ 60

In conclusion, the cycloaddit ion of substituted o-benzoquinones with symmetrically- and

unsymmetrically-substituted fulvenes has been shown to be a very efficient method for the

synthesis of highly functionalised bicyclo[2.2.2]octen-7,8-diones, which can conceivably undergo a

variety of interesting transformations. Further work along this line is underway to uncover the

synthetic potential as well as the mechanistic underpinnings of the reaction.

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Acknowledgement: SK thanks Regional Research Laboratory and Department of Science and Technology, India, for a research fellowship. Thanks are due to Mr. George O. Morton, Medical Research Division, American Cyanamid Company, USA, for high resolution NMR spectra.

References and Notes 1. For a recent review of the

Compounds, 2. Ansell, M. F., 3. Ansell, M. F.,

1971, 1414. 4. Horspool, W. 5. AI-Hamdany, 6. AI-Hamdany, 7. Ansell, M. F., 8. Friedrichsen, 9. Friedrichsen, 10. 11. 12. 13. 14. 15.

16.

Chemistry of o-quinones, see, The Chemistry of the Quinonoid

ed. S. Patai, John Wiley & Sons, 1988, Vol. 2 Gosden, A. F., Leslie, V. J., Murray, R.A.J . Chem. Soc., (C), 1971, 1401. Bignold, A. J., Gosden, A. F., Leslie, V. J., Murray, R. A. J. Chem. Soc., (C),

M., Tedder, J. M., Din, Z. U. J. Chem.Soc., (C), 1989, 1692. R., Salih, S. J. Chem. Soc., Chem. Commun., 1978, 397. R., Salih, S. J. Iraqi Chem.Soc., 1981, 6, 53-61. Leslie, V. J..J. Chem.Soc., (C), 1971, 1423. W., Schroer, W. D., Smidt, R. Justus LJebigs Ann. Chem., 197'6, 793. W., Jurg'ens, H. J., Betz, M. Tetrahedron, 1976, 147.

Friedrichsen, W., Buldt, E., Betz, M., Smidt, R. Tetrahedron Lett., 1974, 2469. Takata, T., Tejima, R., Ando, W. J. Org. Chem., 1983, 48, 4764. Schafer, W., Leute, R, Schlude, H. Ber., 1971, 104, 3211. Stone, K. J., Little, R. D. J. Org. Chem., 1984, 1849. Erickson, M. S., Cronan, J. M., Garcia, J. G., McLaughlin, M. L. J. Org. Chem., 1992,1849. Details of the experiment, which are typical are as follows: 3,5-Di-tert-butyl-o-benzoquinone (0.236 g, 1 mmol.) and p-methoxy-phenylfulvene (0.184 g, 1 mmol.) were dissolved in dry toluene (1 mL) and taken in a glass tube. The tube was then evacuated, sealed under nitrogen and heated at- 110oC. After 5 h the colour of the solution changed from red to yellow. The reaction mixture was cooled, and the solvent was removed in vacuo and chromatographed On silica gel (10% ethyl acetate/petroleum ether) to afford yellow crystals of 2 (0.22 g, 56%). mp.178-180oC. All new compounds were identified by IR, NMR, and mass spectra. Spectral data of representative compound 2: 1H NMR (CDCI3) 8 ppm: 0.89 (s, 9H), 1.23

(s, 9H), 3.76 (s, 1H), 3.79 (s, 1H), 3.83 (s, 3H), 3.86 (s, 1H), 5.80 (d, 1H), 6.03 (d, 1H), 6.37 (m, 2H), 6.90 (d,.2H), 7.26 (d, 2H). IR (CH2CI2): 1732 (C=O) cm -1. 13C NMR (CDCI3)

(5 ppm: 27.5, 28.0, 34.0, 35.0, 41.0, 48.5, 51.0, 55.0, 61.0, 114.5, 121.0, 122.0, 129.0, 134.0, 141.0, 144.5, 150.0, 158.5, 190.0, 192.5. MS m/z. 41, 56, 57, 63, 76, 91,115, 164, 184 (100%), 252, 291,346, 404(M+).

(Received in USA 25 October 1994; revised 13 December 1994; accepted 9 January 1995)