Diels‐Alder‐Reaktionen mit Diakzeptor‐substituierten Methylencyclopropanen — Ein neuer Aspekt für die doppelte nucleophile Substitution an Cyclopropanen

Abstract

(Diacylmethy1ene)cyclopropanes 3, generated from aminocyclopropanes 1 or 2 and acetyl chloride as highly reactive intermediates, are trapped by dienes 9a -c yielding the Diels-Alder products 10. Regioisomers lOAb and lOAc were isolated exclusively from the interaction of LA with pentadiene 9b and isoprene (9c), respectively. Cycloadditions with bicyclic methylenecyclopropanes 3A and 3B stereospecifically generated the la,6a,7@-isomers 10A and 10B. Starting from 10 the products 16,19, and 20 are obtained by a degradation reaction of the Meldrum's acid moiety or by an oxidative ring cleavage of the cyclohexene unit. An X-ray structural analysis is reported for 1OAc. Using MNDO calculations the reactivity of various (diacylmethy1ene)cyclopropanes 3 as dienophiles has been studied.