Enantioselective Desymmetrization Reactions Mediated By Magnesium Catalysis

The desymmetrization reaction of prochiral or meso-molecules is a direct and efficient method for the synthesis of chiral compounds.In recent years,it has been particularly important to develop new catalytic systems for the study of desymmetry reactions.In this dissertation,we have achieved highly enantioselective desymmetrization of several types of compounds by developing and utilizing a series of magnesium catalysts.This dissertation is divided into nine chapters.The first chapter mainly includes the introdution of the enantioselective desymmetrization reaction with several representative substrates.In the second chapter,by using commercially available chiral binaphthol ligand and dibutylmagnesium as catalyst,we achieved the desymmetrization of aziridine with benzofuranone.In the third chapter,we designed a bi-ligand catalytic system to realize the asymmetric ring opening reaction of aziridines with isocyanoacetates,observing that the introduction of diphenylphosphoramide can significantly increase the enantioselectivities of the reaction.In the fourth chapter,the desymmetrization ring-opening reaction of aziridines with?-sp~2-carbon of carbonyl compounds was achieved mediated by magnesium catalyst.Then,using the in-situ generated magnesium catalyst,we respectively achieved the desymmetrization reaction of aziridine with hydroxylamines and tetrazoles.In the former case,a series of compounds with types of diamine skeletons have been obtained in excellent chemical yields and enantioselectivities.While in the latter reaction,we successfully obtained a series of tetrazole-modified primary amines through a simple conversion of chiral desymmetrization products,which was further applied into the modification of peptides.In the seventh chapter,we designed and synthesized a series of prochiral cyclohexadienones,and the intramolecular enantioselective desymmetrization of these compounds was successfully operated using magnesium catalyst.Furthermore,we introduced the magnesium catalyst into the[3+2]cycloaddition reaction of isocyanoacetates with alkyne ketones,both of enantioenriched 2H-and 3H-pyrroles can be obtained respectively by cycliztion and chirality maintaining 1,5-ester shift reactions.In the last section,we briefly summarize the desymmetrization reaction mediated by magnesium catalyst.