Synthesis and Transformations of Methyl 4-(2-chloroethyl)-4H-thieno3,2-bpyrrole-5-carboxylate

A novel methyl 4-(2-chloroethyl)-4H-thieno3,2-bpyrrol-5-carboxylate was synthesized by refluxing methyl 4H-thieno3,2-bpyrrol-5-carboxylate in 1,2-dichloroethane in the presence of K2CO3. The acylation of the product with thiophene-2-carbonyl chloride under standard Friedel–Crafts conditions using SnCl4 yielded the target methyl 4-(2-chloroethyl)- 2-(thiophene-2-carbonyl)-4H-thieno3,2-bpyrrole-5-carboxylate. A by-product, 5,6-dihydro-8H-thieno2′,3′:4,5pyrrolo2,1-c1,4oxazin-8-one, was also isolated, which was formed by an unusual intramolecular cyclization. The condensation of methyl 4-(2-chloroethyl)-4H-thieno3,2-bpyrrol-5-carboxylate with 1H-indole allowed the synthesis of the 2-(4-ethyl-4H-thieno[3,2-bpyrrol-5-yl)methyl]-1H-indole.