Study On Palladium-catalyzed[2+2+1]Cyclization Of 1,6-Enynes With Vinyl Bromides And The Synthesis Of Biaryl Derivatives

Tetrahydro-lH-cyclopenta[c]furans represent an important class of fused O-heterocyclic owing to their broad distribution in natural products with the appealing pharmacological activities.Therefore,we have developed a Pd(0)-catalyzed[2+2+1]intermolecular cyclization reaction by using a novel Cl-synton,easily accessible vinyl bromides,and 1,6-enynes to access intriguing tetrahydro-1H-cyclopenta[c]furan derivatives bearing two quaternary carbon centers in good yields and excellent diastereoselectivity.The main contents include the following sections:In the first section,we briefly review the progress of research on 1,6-enyne cyclization reactions and their application to organic synthesis.Two part on the cyclization reaction models are discussed,including:(1)the intramolecular cycloisomerization of 1,6-enyne,such as palladium,rhodium and ruthenium catalyzed cycloisomerization of 1,6-enyne;and(2)the intermolecular cyclization reaction of 1,6-enyne.This section mainly described the[2+2+2]and[2+2+1]reaction modes with the mechanism for the intermolecular cyclization of 1,6-enynes.In the second section,a novel palladium-catalyzed[2+2+1]cyclization of 1,6-enynes with vinyl bromides is described.Firstly,we optimized the reaction by screening various catalysts,solvents,bases and additives systematically and found the optimal conditions.Secondly,a variety of corresponding fused bicycle products with different functional group could be obtained in moderate to good yields with excellent diastereoselectivities(>19:1).Finally,we made some attempts on an asymmetric version of this reaction.Meanwhile,a plausible reaction mechanism was also proposed.In the third section,we described the method to synthesize a series of novel biaryl derivatives through the Suzuki coupling reaction.