Aziridines, 66 [1]. Arene Hydrides. 12 [2]. Reactions of carbanions with two sterically demanding 1-benzoylaziridines: SET, SN2, 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 (SNs) 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 SN2/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.