2,1,3-benzoselenadiazoles as valuable synthetic intermediates

N-alkyl-1,2-benzenediamines, 4-substituted-3-nitro-1,2-benzenediamines and 3,4-diamino-2-nitrophenols are readily obtained by deselenation of alkyl qu aternary salts of 2,1,3-benzoselenadiazoles (bsd) and 5-substituted-4-nitro -bsd. The latter are easily obtained by nitration of 5-X-bsd (X = Me, Br, C l, F, OMe, NHMe). Nitration of 5-fluoro-bsd yields the 4-nitro derivatives that are accompanied by substantial amounts of the corresponding 4-nitro-bs d-5-ols. ipso-Nitration of 5-fluoro-4-methyl-bsd is followed by instantaneo us hydrolysis to (+/-)-4-methyl-4-nitro-bsd-5(4H)-one. Batcho-Leimgruber in dole synthesis on 5-methyl-4-nitro-bsd followed by reductive deselenation o f 1,2,5-selenadiazolo[3,4-g]indole affords 6,7-diaminoindole. Cyclocondensa tion of 3-nitro-1,2-benzenediamines with acetylacetone provides a convenien t route for the preparation of 2-methyl-4-nitrobenzimidazoles. Less-accessi ble 6-halo-5-nitro- and 6-methoxy-5-nitroquinoxalines are efficiently synth esized by regioselective condensation of alpha-dicarbonyls with 4-halo- and 4-methoxy-3-nitro-1,2-benzenediamines. The reactive halogen atom or methox yl group ortho to the nitro substituent renders these quinoxalines versatil e intermediates to further heterocycles. The Se-77, C-13 and H-1 NMR chemic al shifts of sixteen bsd derivatives, and the C-13 NMR chemical shifts of e ight derivatives of 2-methylquinoxalines are presented.