Preparation of alpha-(2,2-diphenylhydrazino)lactones and related compounds by 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 resulting 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 evaluated, 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 the nitrogen substituent (28 --> 30) so that an alpha-amino lactone can be generated by acid hydrolysis of the cyclization product.
Clive
D L
DL
Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2. derrick.clive@ualberta.ca
Zhang
J
J
Subedi
R
R
Bouétard
V
V
Hiebert
S
S
Ewanuk
R
R