Formation of an Unusually Stable Enol by Conjugate Addition of Active Methylene Compounds to E-3-aryl-2-cyanopropenoates

Abstract

The purpose of this study was to research the chemical transformation of the Warfarin molecule. The reactions of 4-hydroxycoumarin with substituted a-cyanocinnimate esters gives addition products that are entirely in the form of the enol tautomer, as demonstrated by the appearance of the doubly benzylic proton as a singlet rather than as a doublet (half an AB quartet).