Efficient three-component Gewald reactions under Et3N/H2O conditions

摘要

In a medium consisting of triethylamine and water, α-methylene ketones undergo room temperature Gewald reactions with elemental sulfur and ethyl cyanoacetate (or malononitrile) to yield 2-aminothiophene derivatives efficiently within short time periods. Because of the high polarity of the medium, products precipitate in the reaction mixtures spontaneously. This makes isolation of the products easy by simple filtration and avoids cumbersome chromatographic separations. Mechanistic studies suggest that the reactions proceed via a Knoevenagel condensation pathway.