Study On Halogenation Of Unsaturated Carbamate Compounds

Electrophilic halogenation of olefins is one of the most fundamental reactions in organic chemistry, and provides an important transformation for organic synthesis. The halogen groups can be readily transformed to other functional groups. The halo functional group is widely spread in bioactive natural products and pharmaceutical intermediates. As an important way to build halogen groups, it is highly desirable to develop halogenation reactions. Studies on the halogenation of alkenes have a history of more than 100 years, however, the catalytic asymmetric version has only recently emerged.This thesis is divided into two chapters, the first chapter reviewed the asymmetric halogenation of alkenes from intramolecular and intermolecular point of view. Intramolecular halocyclization reactions involving halolactonization, haloetherification, haloamination and halolactamization, and intermolecular haloesterification, dihalogenation and haloamination are documented.In the second chapter, the regio-and enantioselective halocyclization of unsaturated N-tosylcarbamates and enantioselective bromoamination of allylic alcohols were presented. Regioselective bromocyclization of unsaturated N-tosylcarbamates by using N,N-dibromosulfonamides has been developed. Both bromo-N- and -O-cyclization products can be prepared in high regioselectivity. The enantioselective chloro-O-cyclization of unsaturated carbamates by using ammonium salts of cinchona alkaloids as phase transfer catalysts was also described. Furthermore, the asymmetric intermolecular bromoamination of allylic alcohols by using a novel cinchona alkaloid thiourea catalyst has been achieved, leading to various vicinal haloamines with high enantioselectivity.