| Abstract: | The heterocyclic cyclopropf]indene 19 was synthesized via cycloaddition of diene 10 to the cyclopropene 11a and subsequent base-induced aromatization. While 19 is isolable, although very short-lived, the oxa analogue 18 decomposed under the conditions required for its preparation. The difluoro derivatives 14 and 15 , in which the heterocyclic moiety is saturated, are accessible by the cycloaddition approach, but the corresponding dichlorides are again not isolable. Cyclopropf]indenes carrying substituents at C(4) have been obtained via cycloaddition of 22b to 1-bromo-2-chlorocyclopropene. The key step of the sequence is a double Curtius degradation of the cycloadduct 23b to the ketone 27a . While aromatization of the alcohol 27b provided the cyclopropf]indenol 28b , the reaction failed with 27a . Attempts to convert 28b to 1,3-dihydrocyclopropf]indene ( 25 ) via the methanesulfonate 28d failed. |
