Study On Lewis Acid-catalyzed Ammonium Ylide’s [2,3]-sigmatropic Rearrangement-based Asymmetric Cascade Reaction

The [2,3]-sigmatropic rearrangement of ammonium ylides is widely recognized as a versatile process for the synthesis of useful nitrogen-containing compounds.Current limitations of this reaction include the difficulty with the generation and isolation of the reactive ammonium salts,substrate compatibility and chemselectivity issues under the strong basic condition for the generation of the ammonium ylide,and the paucity of catalytic asymmetric methods with good stereocontrol.In this thesis,we developed a silver-catalyzed asymmetric cascade reaction based on an [2,3]-sigmatropic rearrangement of the in situ formed ammonium ylide.This cascade reaction include an intramolecular 1,4-conjugated addition of tertiary amine to the alkyne,a subsequent deprotonation of the resultant ammonium salt for the formation of ylide,and finally a [2,3]-sigmatropic rearrangement.In this process,the chirality was fully transferred from the precursor to the product in a chiral relay manner through the formation of the quaternary ammonium salt with a chiral nitrogen center,producing series of nitrogen-containing compounds,posessing a versatile allene group and with 5/6 and 6/6 fused ring systems,in good yield with good enantiopurity(up to 98.7% ee).Given the wide distribution of such skeleton in natural products,such as erythrina and cephalotaxus,this method will find broad application in the synthesis of such type of molecules.