Comparative reactivity of N′-(5-benzoyl/ethoxycarbonyl)thiazol-2-yl-N,N-dimethylformamidines with ketenes

The comparative account of the reactivities of N′-(5-benzoyl and ethoxycarbonyl)thiazol-2-yl]-N,N-dimethylformamidines (1a and 1b), tremendously influenced by the electronic nature of the substituents on C-5 of the thiazolic ring with various monosubstituted and conjugated ketenes is reported herein. The DA cycloadditions of the dienyl pyrimidinone 3h with both symmetrical as well as unsymmetrical dienophiles leading to the formation of various thiazolic pyrimidinone derivatives are also reported.