Silica Gel-mediated Synthesis of β-Enamino Esters and its Application for the Synthesis of Indeno 4-Hydroxypyridin-2(1H)-Ones

The full scope of SiO2-based condensation of aliphatic or aromatic amines and beta-keto esters to give beta-enamino esters was examined. Functionalized linear beta-enamino esters were easily obtained from SiO2-based condensation of beta-keto esters and amines only after simple filtration. It was also demonstrated that cyclic beta-enamino esters with 99% purity can be prepared in a practically large scale (60 g) without using silica gel column chromatography. The utility of the present method was fortified by the preparation of pharmaceutically useful indeno-4-hydroxypyridin-2(1H)-one analogue 11.