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, compounds 3 appear as single (E,E) isomers. The reaction of 3 with various organometals in THF represents a novel access to unknown (E,E)-1,4-dialkyl- and (E,E)-1,4-diaryl-2,3-dinitro-1,3-butadienes 4. Finally, Pb-reduction of the two nitrovinylic functionalities of 4 effectively leads to the corresponding symmetrically 1,4-disubstituted 2,3-butanedione dioximes 5.