STRUCTURE OF THE REACTION-PRODUCTS FROM DEHYDROASCORBIC ACID ANALOGS, O-PHENYLENEDIAMINE, AND ARYLHYDRAZINES - X-RAY MOLECULAR-STRUCTURE OF 3-[L-THREO-2,3,4-TRIACETOXY-1-(PHENYLHYDRAZONO)BUTYL]QUINOXALIN-2(1H)-ONE HEMIHYDRATE

Acetylation of the product obtained from successive reaction of dehydro-L-ascorbic acid with o-phenylenediamine and phenylhydrazine gave 3-[L-threo-2,3,4-triacetoxy-1-(phenylhydrazono)butyl]-quinoxalin-2(1H)-one (3) rather than the cyclic structure (4) previously assigned for the reaction product. The structure of compound (3) was confirmed based on 1H NMR, 13C NMR, and X-ray analysis. Reinvestigation of the reaction of 5-phenylfuran-2,3,4(5H)-trione (6) with o-phenylene-diamine and an arylhydrazine led to the isolation of two components (7) and (10). The former was found to exist in dimethyl sulphoxide solution as a tautomeric mixture of hydrazone imine and diazenyl enamine. Attempted acetylation of compound (7) afforded the furo[2,3-b]quinoxaline ring system (8).