One-Pot Synthesis of 4-Substituted 3-Amino-2-cyanothiophenes Involving O-Ethyl Thioformate

An efficient one-pot synthesis of 4-substituted 3-amino-2-cyanothiophenes is described. Treatment of 2-alkyl or aryl substituted acetonitrile sequentially with 2.1 equiv of LDA, 1.1 equiv of O-ethyl thioformate, and 1.2 equiv of 2-chloroacetonitrile afforded the thiophenes in moderate to good yields. The thiophene core can be readily incorporated into more elaborate pharmaceutically relevant structures as demonstrated by converting 3-amino-2-cyano-4-phenylthiophene (1g) to various functionalized thieno[3,2-d]pyrimidines in only two steps.