Preparation of alpha-(2,2-diphenylhydrazino)lactones and related compoundsby radical cyclization: Use of glyoxylic acid hydrazone derivatives

Glyoxylic acid diphenylhydrazone (2a) and the corresponding O-benzyloxime ( 2b) are easily esterified in high yield by beta -bromo alcohols. The result ing esters undergo radical cyclization to alpha-(2,2-diphenylhydrazino)- or alpha-[(phenylmethoxy)amino]lactones on treatment with tributyltin hydride . Esters for radical cyclization were also made using a beta-(phenylseleno) alcohol and an enol ether. Several derivatives of glyoxylic acid were eval uated, but none was as effective as 2a or 2b. The imine 28 was prepared by an indirect route; it undergoes radical cyclization with displacement of th e nitrogen substituent (28 --> 30) so that an alpha -amino lactone can be g enerated by acid hydrolysis of the cyclization product.