Cycloaddition reactions between 2-vinylthiophen and the dienophiles maleic anhydride, dimethyl acetylenedicarboxylate,'methyl propiolate, and methyl acrylate, are reported. Products include simple benzo [b] thiophen carboxylates (6, 13, 17) and reduced derivatives (3, 4, 18). The acetylenic dienophiles also gave a dihydrobenzthienyl-acrylate (16) or- fumarate (11), and the dithienylcyclohexene esters (7) and (14).
![4,5,6,7-Tetrahydro-4-benzo[b]thiophen carboxylic acid methylester Structure](https://image.chemsrc.com/caspic/346/100590-46-3.png)
![Methyl benzo[b]thiophene-4-carboxylate Structure](https://image.chemsrc.com/caspic/460/100590-43-0.png)