Synthetic exploitation of the ring-opening of 3,4-dinitrothiophene. Access to 1,4-disubstituted 2,3-dinitro-1,3-butadienes and 2,3-butanedione dioximes
The optimized ring-opening reaction of 3,4-dinitrothiophene 1 with either primary or secondary amines leads to 1,4-bis(alkylamino)- and 1,4-bis(arylamino)- 2 or 1,4-bis(dialkylamino)-2,3-dinitro-1,3-butadienes 3 in satisfactory to excellent yields. While compounds 2 in solution appear to be mixtures of (Z,Z), (Z,E) and (E,E) stereoisomers, whose composition is influenced by the nature of the solvent