Enantioselective Syntheses Of 4H-3,1-Benzoxazines Via Catalytic Asymmetric Chlorocyclization Of O-Vinylanilides

4H-3,1-Benzoxazine is one of the important heterocyclic compounds.The compounds containing 4H-3,1-benzoxazine core usually show a wide range of biological activities and have been used as anti-anxiety and anti-convulsion.Futhermore,these compounds also are fungicides and progesterone receptor agonists.Although substantial efforts have been devoted to the synthesis of benzoxazine derivatives,methods for enantioselective synthesis of 4H-3,1-benzoxazines are rare.In order to promote the biological evaluation of optically active 4H-3,1-benzoxazine derivatives,it is necessary to further develop the catalytic system for the enantioselective synthesis of these compounds.The catalytic asymmetric halogenation of alkenes is one of the most promising research fields in recent years,especially asymmetric halocyclizations have been successfully applied as the powerful and straightforward strategies to construct the chiral cyclic compounds such as lactones,cyclic ethers,nitrogen heterocycles,and related structures.Consequently,inspired by the success of asymmetric chlorocyclization reactions for the synthesis of chiral oxazolines,dihydrooxazines and related compounds,this thesis has developed a simple method for the synthesis of4H-3,1-benzoxazine derivatives via the halocyclization of o-vinylanilides catalyzed by a novel cinchonidine-based chiral ester in excellent yields(up to 99% yield)and high enantioselectivities(up to 92% ee).Moreover,we proposed a possible transition state model for this reaction.