Synthesis of 5,6‐dihydrothieno(and furo)pyrimidines bearing an active methine group at the 4‐position

Abstract

Abstract The reactions of 2‐benzamido‐4,5‐dihydro‐3‐thiophene(and ‐3‐furan)carbonitriles ( 1a‐c and 4a‐c ) with ethyl acetoacetate in the presence of tin(IV) chloride and triethylamine provided the corresponding ethyl 2‐(5,6‐dihydro‐2‐phenylthieno(and furo)[2,3‐ d ]pyrimidin‐4‐yl)‐3‐oxobutanoates ( 2a‐c and 9a‐c ). Similarly, compounds 1a‐c and 4a‐c reacted with dialkyl malonates to give the corresponding dialkyl(5,6‐dihydro‐2‐phenylthieno(and furo)[2,3‐ d ]pyrimidin‐4‐yl)propanedioates ( 5a‐c, 6a‐c, 10a‐c and 11a‐c ).