Synthetic exploitation of the ring-opening of 3,4-dinitrothiophene. Access to 1,4-disubstituted 2,3-dinitro-1,3-butadienes and 2,3-diaminobutanes

The reactions of 1,4-bis(diethylamino)-2,3-dinitro- 1,3-butadiene 1 (deriving from ring-opening of 3,4-dinitrothiophene with diethylamine) with one mole of Grignard reagents give, together with disubstituted products 1,4-dialkyl- and 1,4-diaryl-2,3-dinitro-1,3-butadienes 2, the monosubstituted 1-alkyl-4-diethylamino- and 1-aryl-4-diethyl-amino-2,3-dinitro-1, 3-butadienes 8 in yields dependent on the nature of the reagent employed. Aryl-substituted compounds 8 undergo a highly regioselective reaction with aryl Grignard reagents to furnish good yields of 1-Ar-1-4 Ar-2-2,3-dinitro-1,3-butadienes 9. Preliminary results are also reported on the transformation of some dinitrobutadienes 2 and 9 into the corresponding 1,4-disubstituted 2,3-diaminobutanes 10.