Synthesis of thieno[2,3‐ d ]pyrimidines from 4,6‐dichloropyrimidine‐5‐carbaldehydes

Several thieno[2,3‐ d ]pyrimidines have been prepared by intramolecular cyclisation of 6‐(substituted methylthio)‐5‐pyrimidinecarbaldehyde and carbonitrile intermediates derived from 6‐chloropyrimidine‐5‐carbaldehydes and 5‐carbonitriles and methyl thioglycolate or 5‐formylpyrimidine‐4‐(3 H )‐thiones and appropriate α‐halogeno compounds. Thienopyrimidines 18 and 5c were nitrated to the corresponding nitro compounds 23 and 24 . Hydrolysis at position 4 of compound 18 also occurred during nitration. The ester 5g was hydrolysed in base to the acid 25 .