Cu(I)-Catalyzed Cyclized Coupling Reaction of o-Ethynylphenylphosphonic Acid Monoesters with Allyl Bromide

4-Allylphosphaisocoumarins can be prepared in good yield and with high regioselectivity by the reaction of o-ethynyl phenylphosphonic acid monoesters with allyl bromide catalyzed by CuI. The present reaction represents the first example of a phosphonic acid monoester cyclized coupling reaction with alkyl halide.