| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
1,2-Diacyl-1-chloroethylenes were reacted with several disubstituted diazomethanes to give the pyrazolines and the cyclopropanes. The thermal stability of the pyrazolines increases with the variation of the substituents at C-5 in the order biphenylylene<Ph, Ph<Ph, Me<Me, Me, while pyrazolines bearing bulky vicinal substituents at C-3, C-4, and C-5 in cis configuration are substantially more stable than other isomers. This abnormal stability is explained by reasonable expectation that bulky C-4 substituents partly inhibit conformations of the conjugated substituents at C-3 or C-5 favorable for the decomposition. Although most of the thermal transformations of the pyrazolines to the cyclopropanes retain the stereochemistry of the starting materials, some pyrazolines bearing bulky vicinal cis groups gave mixtures of stereoisomeric cyclopropanes. The mechanism for the thermolysis of these pyrazolines is explained on the basis of stereochemical distribution of decomposition products by (90,
… More
90) trimethylene intermediates.
Treatment of 5,5-disubstituted 3-chloro-1-pyrazolines, derived from the reaction of disubstituted diazomethanes (2-diazopropane, phenyldiazoethane, diphenyldiazomethane, diazofluorene, and diazoindene) with 1,2-diacyl-1-chloroethylenes (dimethyl chlorofumarate, chloronaphthoquinone, and N-tolylchloromaleimide), with triethylamine gave the corresponding 3,3-disubstituted pyrazolenines in good yields except some cases. Five-membered imide ring fused bicyclopyrazolines did not afford the pyrazolenines but diazoalkenes, in contrast to isolation of the pyrazolenines for the six-membered fused system. Formation of the diazoalkenes is explained by thermal ring opening of the pyrazolenines. Isolation of the diazoalkenes in five-membered ring fused systems is explained by destabilization of the pyrazolenines due to angle strain arising from two five-membered rings fused bicyclic systems, which results in increase of the relative stability of the diazoalkenes. The presence of the strain was born out from the MM2 calculation as well as chemical evidences. Less
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