Synthesis of 2,3-disubstituted thiophenes from 2-aryl-3-nitro-cyclopropane-1,1-dicarboxylates and 1,4-dithiane-2,5-diol

Abstract

A two-step synthesis of 2,3-disubstituted thiophenes from trans-2-aryl-3-nitrocyclopropane-1,1-dicarboxylates and 1,4-dithiane-2,5-diol is described. The nitrocyclopropane dicarboxylates when treated with boron trifluoride etherate formed aroylmethylidene malonates in situ through ring-opening followed by rearrangement and a Nef reaction, and subsequent addition of 1,4-dithiane-2,5-diol and triethylamine to the same flask gave tetrahydrothiophenes via a tandem thia-Michael addition/aldol reaction in a sequential one-pot manner. The product tetrahydrothiophenes upon treatment with p-toluenesulphonic acid underwent dehydration followed by monodecarbethoxylation to afford 2,3-disubstituted thiophenes.