AZIRIDINES .66. ARENE HYDRIDES .12. REACTIONS OF CARBANIONS WITH 2 STERICALLY DEMANDING 1-BENZOYLAZIRIDINES - SET, S(N)2, CARBONYL ATTACK

Reactions of 2-phenyl (1a) and 2-benzyl (1b) 1-benzoyl-2-butylaziridines with carbanions X(-), AH(-), and Fl(-) of xanthene, dihydroanthracene and fluorene always form N-(2-butylethyl)-benzamides carrying phenyl (9a) or benzyl (9b). This reductive ring opening indicates an SET mechanism with aziridino ketyls 6a, b as intermediates. Nucleophilic ring opening (S(N)s) is found only with the carbanion of the lowest reducing power: Fl(-) --> 5a, b (62 %, 14 %). These two mechanisms cleave different bonds, a finding without precedence in S(N)2/SET competitions. Carbonyl addition resulting in benzoyl transfer to xanthene, dihydroanthracene or fluorene is usually also observed. It is the main reaction with X(-) and 1a. The highest yields of 9a, b are obtained with AH(-) since a special inner-sphere SET is available.