Studies On Catalytic Asymmetric Decarboxylative Addition Reaction Of Enamides With ?-ketoacids And The Synthesis Of Benzoxazines

This paper includes two parts:In the first part,a highly enanatioselective decarboxylative addition reaction of?-keto acids to enamides have been achieved by combining metal and Br?nsted acid catalysis.In presence of 5 mol%of copper?I?thiophene-2-carboxylic acid and 7 mol%?S?-binaphthol-derived chiral phosphoric acid,a series of chiral amines bearing a quaternary carbon stereocenters have been obtained in 65%-92%yields with excellent enantioselectivities?90%-94%ee?.In the second part,a convenient and efficient synthesis of 4H-3,1-benzoxazines was developed.By using a base-mediated amide tautomerization and subsequent cyclization of N-[2-?chloromethyl?aryl]formamide,a variety of aromatic and alkyl4H-3,1-benzoxazines could be obtained without oxidants and metal additives.Excellent yields were generally achieved.The direct oxidation of4H-3,1-benzoxazineswithKMnO₄couldaffordbiologicallyactive4H-3,1-benzoxazin-4-ones in high yields.