A study on the regioselectivity in N,C-acylation of β-enamino-esters

With the aim to produce the new corresponding amide, amino pyrone 1 [=4-(benzylamino)-6-methyl-2H-pyran-2-one] was acylated in dichloromethane in the presence of triethylamine, obtaining an unexpected mixture of N- and C-acyl products in a 60:40 ratio, respectively. The regioselective investigation was enlarged by using a series of organic bases and taking into account both solvent effects and acyl halide structure. Conditions able to give pure amides or pure C-acyl products were established. The study also includes the reactivity of a β-enamino-ester with NH group involved in an intramolecular hydrogen bond, where pure C-acyl products were obtained.