Reactions of N-(Ethoxycarbonyl)-3-halo-3-(halomethyl)azetidines with DBU. The Halogen Dance.
Reaction of N-(ethoxycarbonyl)-3-(bromomethyl)-3-chloroazetidine (3) with DBU results in the formation of two haloalkenes, i.e., N-(ethoxycarbonyl)-3-(bromomethylene)azetidine and N-(ethoxycarbonyl)-3-(chloromethylene)azetidine (4a and 4b, respectively). The results of control experiments suggest that Cl(-) is capable of promoting nucleophilic displacement of bromine in the CH(2)Br groups of both 3 and N-(ethoxycarbonyl)-3-bromo-3-(bromomethyl)azetidine (8), but Br(-) is incapable of displacing chlorine in the CH(2)Cl groups of both N-(ethoxycarbonyl)-3-chloro-3-(chloromethyl)azetidine (7) and N-carbethoxy-3-bromo-3-(chloromethyl)azetidine (10). Thus, it is suggested that the formation of 4b via reaction of 3 with DBU is a result of DBU-promoted elimination of HCl from 7, a key reaction intermediate. The observations reported herein can be explained without invoking the intermediacy of any bridged halonium ion.
Marchand
Alan P.
AP
Department of Chemistry, University of North Texas, P.O. Box 5068, Denton, Texas 76203-0068.
Devasagayaraj
Arokiasamy
A