A Re-Examination of the Reaction of 3,4-Diamino[1,2,5]oxadiazole with Glyoxal

Rodney L. Willer, University of Southern Mississippi
Robson F. Storey, University of Southern Mississippi
Christopher G. Campbell, University of Southern Mississippi

Abstract

Reaction coordinate mapping was used to study the reaction of 3,4-diamino[1,2,5]oxadiazole (3,4-diaminofurazan) and 3,4-diamino[1,2,5]thiadiazole with glyoxal. The thiadiazole was known to give a good yield of [1,2,5]thiadiazolo[3,4-b]pyrazine, whereas the oxadiazole had not yielded, until now, [1,2,5]oxadiazolo[3,4-b]pyrazine (or furazano[2,3-b]pyrazine). The calculations suggested that the diols, 5,6-dihydroxy-4,5,6,7-tetrahydro[1,2,5]oxadiazolo[3,4-b]pyrazine and 5,6-dihydroxy-4,5,6,7-tetrahydro[1,2,5]thiadiazolo[3,4-b]pyrazine should be stable intermediates, and once formed, should provide a pathway to the target compounds via two dehydration steps, under forcing conditions. With this information in mind, the reactions of 3,4-diamino[1,2,5]oxadiazole with glyoxal and pyruvic aldehyde were re-examined. The reaction of 3,4-diamino[1,2,5]oxadiazole with glyoxal and pyruvic aldehyde produced, under slightly basic conditions, a near quantitative yield of the expected initial products, 5,6-dihydroxy-4,5,6,7-tetrahydro[1,2,5]oxadiazolo[3,4-b]pyrazine and the 5-methyl analog, respectively. The diols were easily isolated by lyophilizing the aqueous reaction mixture. The diols were pyrolized on silica gel at 160 degrees C to give the desired [1,2,5]oxadiazolo[3,4-b]pyrazine and the 5-methyl analog. Both compounds were easily reduced to the corresponding 4,5,6,7-tetrahydro-derivative using sodium borohydride in THF/methanol. The [1,2,5]oxadiazolo[3,4-b]pyrazine also displayed other interesting chemistry.