Tandem thia-Michael/Dieckmann condensation of allenyl esters for the regioselective synthesis of trisubstituted thiophenes

[Display omitted] •Regioselective tandem thia-Michael/Dieckmann condensation of allenyl esters with methyl mercaptoacetate were developed.•In the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, 2,3,5-trisubstituted thiophenes were obtained.•In the presence of magnesium bromide and triethylamine, 2,3,4-trisubstituted thiophenes were obtained.•Thia-Michael adduct was cyclized to 2,3,5-trisubstituted thiophene in the presence of DBU.•The geometry of thia-Michael adduct was determined on the basis of the 1H–1H nuclear Overhauser effects. Tandem thia-Michael/Dieckmann condensation of allenyl esters with methyl mercaptoacetate in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene afforded 2,3,5-trisubstituted thiophenes regioselectively. On the other hand, 2,3,4-trisubstituted thiophenes were obtained as the sole product by tandem thia-Michael/Dieckmann condensation employing magnesium bromide and triethylamine.