Base-catalysed reactions of glyoxal. Part I. 1,4-Diformyl- and 1,4-bis-methylsulphonyl- derivatives of 2,3,5,6-tetrahydroxypiperazines

The base-catalysed additions of glyoxal to formamide and methane sulphonamide gave 1,4-diformyl- and 1,4-bis-methylsulphonyl- derivatives of 2,3,5,6-tetrahydroxypiperazines, respectively, in addition to the corresponding NN′-disubstituted 1,2-diamino-1,2-ethanediols. Trifluoroacetamide, chloroacetamide, ethyl oxamate, and oxamic acid gave only the corresponding 1,2-ethanediols when treated with basic aqueous glyoxal; other amides examined gave inconclusive results. The structures of the tetrahydroxy-compounds were confirmed by their conversion to esters, ethers, and chloro-derivatives. The thermal decomposition of 2,3,5,6-tetrachloro-1,4-diformylpiperazine gave 2-chloropyrazine hydrochloride.