Studies on heterocyclic enaminonitriles. II. Synthesis and aromatization of 2-amino-3-cyano-4,5-dihydrothiophenes.

Abstract

Thirane reacted with malononitrile and sodium hydride to give 2-amino-3-cyano-4, 5-dihydrothiophene (IIa) in 57% yield. Similarly, 2-methyl (or 2-phenyl) thirane reacted with malononitrile to form 2-amino-3-cyano-5-methyl (or 4-phenyl)-4, 5-dihydrothiophene (IIb or IIc). The reactions of the 2-benzamido (or 2-acetamido) derivatives of (IIa or c) with N-bromosuccinimide (NBS) in the presence of 2, 2'-azobisisobutyronitrile gave the corresponding 5-bromothiophenes. On the other hand, the 2-benzamido (or 2-acetamido) derivative of IIb reacted with NBS to yield 2-benzamido (or 2-acetamido)-3-cyano-5-methylthiophene.