Preparation of alpha-(2,2-diphenylhydrazino)- and alpha-(benzyloxyamino)-lactones by radical cyclization: Use of glyoxylic acid diphenylhydrazone and glyoxylic acid O-benzyloxime

Glyoxylic acid diphenylhydrazone (2, Y = NPh(2)) and the corresponding O-benzyloxime (2, Y OBn) are easily esterified in high yield by beta-bromo alcohols, and the resulting esters undergo radical cyclization to alpha-(2,2-diphenylhydrazino) or alpha-(benzyloxyamino) lactones on treatment with tributyltin hydride; the initial radical can be formed by homolysis of a carbon-selenium bond as well as a carbon-bromine bond and, when applied to appropriate alcohols, the esterification-radical closure sequence can also be used to make six- or seven-membered lactones.