Reactions of 3-methylamino-5-phenylthiophene with α,β-unsaturated esters and α,β-unsaturated nitriles

Abstract

Treatment of 3-methylamino-5-phenylthiophene with α,β-unsaturated esters, i.e., methyl acrylate, (E)-methyl crotonate, diethyl fumarate, diethyl maleate and ethyl propiolate, in tetrahydrofuran for several days at reflux gave 1-methyl-3,4-dihydrothieno[2,3-e]pyridin-2-ones 4 and/or 1-methylthieno[2,3-e]pyridin-2-ones 5, depending on the structure of the esters. On the other hand, the same reactions with α,β-unsaturated nitriles such as acrylonitrile and tetracyanoethene, gave the corresponding thiophenes 7 and 10 bearing 2-cyanoethyl and 1,2,2-tricyanoethenyl groups at C-2, respectively. The reaction with (Z)-1,2-dicyanoethene under the same conditions produced the corresponding thiophene 9 bearing the 1,2-dicyanoethenyl group and 1,2-dicyano-5-methylaminobiphenyl.