The Synthesis of Phosphaisocoumarins by Cu(I)-Catalyzed Intramolecular Cyclization of <i>o</i>-Ethynylphenylphosphonic Acid Monoesters

Abstract

Cu(I)-catalyzed intramolecular cyclization of o-ethynylphenylphosphonic acid monoethyl esters was examined, and a new class of six-membered phosphorus heterocycles was formed with high regioselectivity and good yields. The present reaction is the first example of intramolecular addition of P-OH to alkynes, which provides a convenient way to synthesize novel phosphorus heterocycles having potential bioactivities.