Tetrachlorocyclopentadienone Ethylene Acetal1

[2082-08-8]  · C7H4Cl4O2  · Tetrachlorocyclopentadienone Ethylene Acetal  · (MW 261.91)

(Diels-Alder adduct formation;1-3 employed in the synthesis of condensed polycyclic systems4,5)

Alternate Name: 6,7,8,9-tetrachloro-2,5-dioxaspiro[4.4]nona-6,8-diene.

Physical Data: mp 65-67 °C; bp 78-80 °C/0.13 mmHg.

Solubility: insol H2O; sol ether, alcohol, acetone; slightly sol hexane.

Form Supplied in: not available commercially; can be made before use and stored.

Preparative Method: the title reagent can be prepared from hexachlorocyclopentadiene, Ethylene Glycol, and Potassium Hydroxide.

Purification: by distillation followed by recrystallization from ether-pentane.1

Handling, Storage, and Precautions: dimerizes in solution within a few months at 0 °C and within 1 h at 100 °C. It is stable for at least 1 year when stored at 0 °C. It is carcinogenic and should be handled in a fume hood.

Diels-Alder Reactions.

The principle use of the title reagent is as a diene in [4 + 2] cycloaddition reactions. It provides 1:1 adducts as shown in eq 1 with dienophiles such as Maleic Anhydride, 2-butene-1,4-diol, 2,5-Dihydro-2,5-dimethoxyfuran, allyl alcohol, methyl maleate, indene, Vinyl Acetate, 3-thiolen-2-one,3a vinylcyclopropane,3b 1,1-diphenyl-2-vinylcyclopropane,3b cyclopropene,3c 1-methylcyclopropene,3c phenylacetylene,2b diallylamine, Cyclopentadiene, cis,cis-cycloocta-1,3-diene, cis,cis-cycloocta-1,5-diene, and cyclooctadeca-1,5,9-triene.1c It is notable that reactions occur with both electron-rich and electron-deficient dienophiles. Other alkenes that react with the title reagent include norbornadiene,5d 7-t-butoxy norbornadiene,6 cycloheptatriene, tropone, and p-benzoquinone.7 Several of the polyenes afford 2:1 cycloadducts.

Cycloadducts with properly selected dienophiles can lead to structures of potential interest by unmasking and manipulating the carbonyl group, and using the chlorides as precursors for other functional groups of interest.4 For example, the title reagent has been used as a starting material in syntheses of condensed polycyclic systems, as shown in eqs 2 and 3.5

Miscellaneous Reactions.

The reaction of nitrosobenzene with the title reagent has been reported to give N-phenyldichloromaleimide and the unsaturated lactam shown in eq 4.8 The mass spectra of Diels-Alder adducts of alkenes with the title reagent are much simpler than the spectra of other derivatives, and have been used to determine double bond position and alkene geometry.9

1. (a) Newcomer, J. S.; McBee, E. T. JACS 1949, 71, 946. (b) Mackenzie, K. JCS 1964, 5710. (c) Chang, W.-H. JCS 1965, 2305. (d) Chang, W.-H. CI(L) 1964, 709.
2. (a) Chang, W.-H. CI(L) 1964, 1491. (b) Lemal, D. M.; Gosselink, E. P.; Ault, A. TL 1964, 579.
3. (a) Dowd, P.; Weber, W. JOC 1982, 47, 4777. (b) Shimizu, N.; Fujioka, T.; Ishizuka, S.; Tsuji, T.; Nishida, S. JACS 1977, 99, 5972. (c) Bicker, R.; Kessler, H.; Steigel, A. CB 1974, 107, 3053.
4. (a) Van Bree, J.; Anteunis, M. J. O. T 1977, 33, 3331. (b) O'Connor, U.; Rosen, W. TL 1979, 601.
5. (a) Stedman, R. J.; Miller, L. S. JOC 1967, 32, 35. (b) Akhtar, I. A.; Fray, G. I. JCS(C) 1971, 2802. (c) O'Connor, U.; Rosen, W. JOC 1980, 45, 1824. (d) Mackenzie, K. TL 1974, 1203. (e) Fray, G. I.; Saxton, R. G. T 1978, 34, 2663.
6. Astin, K. B.; Mackenzie, K. JCS(P2) 1975, 1004.
7. Bratby, D. M.; Fray, G. I. JCS(P1) 1972, 195.
8. Adler, P. M.; Bennet, R. J.; Fieldman, J.; Fray, G. I. T 1978, 34, 591.
9. Kidwell, D. A.; Blemann, K. AC 1982, 54, 2462.

Palaniappa Nanjappan

Bristol-Myers Squibb Company, Princeton, NJ, USA

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