Substitution-Controlled Selective Formation of Hexahydrobenz[e]isoindoles and 3-Benzazepines via In(OTf)3-Catalyzed Tandem Annulations

A dramatic N-substituent controlled tandem annulation of 2-(2-(2-bromoethyl)phenyl)-1-sulfonylaziridines with 1,3-dicarbonyl compounds has been developed. When the N-substituent was a 4-methylbenzenesulfonyl group (Ts), sequential ring opening of aziridines, nucleophilic substitution, and lactamization took place to provide a series of hexahydrobenz[e]isoindole compounds in good yields with good diastereoselectivities. By contrast, 3-benzazepine compounds were afforded in good yields via ring opening of aziridines and nucleophilic substitution when the N-substituent was the 4-nitrobenzenesulfonyl group (Ns).