Title

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

Document Type

Article

Publication Date

7-1-2012

Department

Chemistry and Biochemistry

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.

Publication Title

Journal of Heterocyclic Chemistry

Volume

49

Issue

4

First Page

919

Last Page

925

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