Heterocyclization of acetamidine adducts with N-(2,2-dichloroethenyl)benzamides

It was shown previously [1, 2] that accessible chlorine-containing enamides I readily react with primary and secondary amines to give 1 : 1 adducts. Here, an important role is likely to be played by N-acylimino tautomers II which are highly electrophilic, and therefore they readily take up an amine molecule at the electron-deficient C=N bond [1]. We have found that reactions of tautomers II with acetamidine result in the formation of 2 : 1 adduct which readily undergo regioselective cyclization in the presence of sodium methoxide (transformation sequence II III IV V shown in the scheme below). The fact that the cyclization involved two acylamino groups and two dichloromethyl moieties in compounds IV was confirmed by IR and H NMR spectroscopy. The molecular weights of new oxazole derivatives V was determined by mass spectrometry. The scope of application of the revealed cyclocondensation IV V and related transformations will be considered elsewhere.