The chromous chloride promoted addition of N-haloamides to olefins. III. Scope and limitations for the synthesis of N-(2-haloalkyl)amides

Abstract

A study of the chromous chloride promoted addition of various N-chloro- and N-bromoamides (ZCONHX) to a variety of olefins shows that two types of addition products can be obtained, namely N-(2-haloalkyl)amides (1,2-adducts) which generally predominate and N-alkylamides (1,H-adducts). The total yield of addition products, the relative proportion of N-(2-haloalkyl)amide(s) and N-alkylamide, and the stereochemistry of 1,2-addition to cyclic olefins vary with the N-haloamide, that is with both Z and X, and also with the olefin. The best yields of 1,2-adducts were obtained with N-chlorocarbamates (Z = O-alkyl) and the proper choice of Z (e.g., 2,2,2-trichloroethoxy, benzyloxy) shows the potential of this method for the synthesis of N-protected β-chloro primary amines where the amino group is attached to the less substituted carbon atom. The use of an excess of N-haloamide results in high yields (>90%) of 1,2-addition based on the olefin, the excess of N-haloamide being simply reduced to the corresponding amide. N-Chloro-N-alkylamides (ZCONRCl) do not add to cyclohexene and are simply reduced to the corresponding amides.