Diastereoselective Diels-Alder reaction of 2-thienyl and 2-furyl substituted 3-propenethioamides with electron deficient dienophiles

The hetero-Diels-Alder reaction of N-aryl-3-(2-thienyl)-2-propenethioamides with N-phenylmaleimide and maleimide yielded a mixture of endo- and exo-2-arylimino-4-(2-thienyl)tetrahydrothiopyran[2,3-c]pyrroles. Cycloaddition to diethyl fumarate required acylation and furnished a mixture of diastereoisomeric 5-(N-acetylphenylamino)-2,3-bis-(ethoxycarbonyl)-4-(2-thienyl)-3,4-dihydro-2H-thiopyrans. Reactions of 3-(2-furyl)-2-propenethioamides with N-arylmaleimides furnished the correspondent 2-arylimino-4-(2-furyl)tetrahydrothiopyran[2,3-c]pyrroles. In the cycloadditions of the heterodienes with N-arylmaleimides the endo-cycloadducts were formed as the major products.