Study On Phosphorus Catalyzed Cyclization Of Conjugated Olefin

Organic phosphine catalysts is one of many small-molecular organocatalysis.It has attracted more and more attention from chemists because of its atomic economy,step economy,mild reaction conditions and simple operation.Herein,we reported a novel phosphine-catalyzed[4+2]annulation reaction of electron-deficient conjugated dienes with enones to generate functionalized dihydropyran skeletons that are important structural motifs in numerous biologically active entities.Mechanistic investigation reveals that the reaction produces a new phosphonium zwitterion,and generated a remote controlled region-selective cycliaddition reaction through the domino sequence cyclization.The chemical selectivity of the products was controlled by using two different phosphorus catalysts(PBu3 and PCy3).In addition,the first asymmetric variant of phosphine-catalyzed annulation of electron-deficient conjugated dienes with enones was reported.It has been found that commercial chiral tBu-binepine can be used to obtain up to 96%enantioselectivity and chemical selectivity of dihydropyran compounds with E/Z=13:1.The successful application of this electron-deficient conjugated diene opens up a new avenue for efficient and economical chiral phosphine catalyzed annulation reaction and provides access to currently inaccessible reaction pathways.