Synthesis Of Substituted Terahydrofuran And Coupling Decarboxylation Reactions Of O-halocarboxylic Acid At High Timperature

T?is thesis includes two sections.1.Synthesis of substituted tetrahydrofuranbenzofuran and benzopyran are one of the common structure of natural products,which have important applications in the fields of biology and medicine.At present,there are many methods on the synthesis of these structures,but most of it are weakness in enantioselective control.Few enantioselective synthesis of these structures were reported.The organic catalysis has play a significant role in the construction of chiral molecules because of its mild reaction conditions and the reaction is green.A novel and efficient method for enantioselective synthesis of chiral tetrahydrofuro[2,3-b]dihydropyran,tetrahydropyrano[2,3-b]dihydropyran,tetrahydrofuro[2,3-b]benzofuran and tetrahydropyrano[2,3-b]benzofuran motifs has been developed.The organocatalyst promoted Michael addition reaction between hemiacetal and ortho hydroxy nitrostyrene or quinone followed by the treatment of acid provided the required product.Whether five-or six-membered ring hemiacetals are used,the reaction works smoothly.This method has the advantages of simple operations,mild reaction conditions and high product ee values(in most cases,up to 99%).The absolute configuration of the product was determined by X-Ray single crystal diffraction method.2?Coupling decarboxylation reactions of o-halocarboxylic acid at high temperatureThe transition-metal-catalyzed cross-coupling reaction are efficient and versatile routes to the formation of carbon-nitrogen and carbon-carbon bonds,which has a widespread application among the organic processes.Since carboxylic acids are low cost,stable and easy to store,extensive studies have been accomplished in this area.In recent years,the reactions reported in the literature were mainly focused on decarboxylation cross-coupling reactions of carboxylic acids involving the breaking of C-COOH bond and then formation of a new carbon-nitrogen and carbon-carbon bonds.But few decarboxylation coupling reactions involving the new mechanism were reported.An efficient method for the direct arylation of heterocycles has been developed.The copper and silver catalyzed coupling reactions of carboxylic acid with heterocycles through direct decarboxylation reaction.This method has the advantages of simple operations and can tolerate a broad range of substrates.