Pechmann Reaction of Resorcinol with Methyl Acetoacetate Structure of a By-product

Abstract

The reaction of resorcinol [1] with. methyl acetoacetate [2] in the presence of 10 mol% of concentrated sulfuric acid has been studied. In addition to the expected 7-hydroxy-4-methylcoumarin [3] as the major product, a small amount of by-product (9.2%) [4] was obtained. The structure of [4] was found to be 7, 7'-dihydroxy-4, 4'-dimethyl-3, 4-dihydro-4, 6'-bicoumarin, a dimer of [3], based on microanalytical data, MS, IR, and NMR spectra of [4]and its bis(ethoxycarbonylmethyl)ether [5]. The plausible mechanism for the formation of [4] is discussed briefly.