Butadienic building blocks from 2-nitrothiophene as precursors of nitrogen heterocycles: intriguing dichotomic behavior

Sulfides and sulfones, derived from the initial ring-opening of 2-nitrothiophene with pyrrolidine/AgN[O.sub.3] in EtOH, are reacted with diazomethane for the synthesis of heterocycles. Dichotomic behavior has yielded pyrazolines from sulfides and isoxazolines from sulfones.