Zinc-catalyzed regioselective C-P coupling of p-quinol ethers with secondary phosphine oxides to afford 2-phosphinylphenols

Org Biomol Chem. 2019 Mar 13;17(11):2972-2984. doi: 10.1039/c9ob00129h.

Abstract

The zinc triflate-catalyzed highly regioselective C-P cross coupling reaction of p-quinol ethers with secondary phosphine oxides is reported. The reaction provides a facile alternative method for the synthesis of 2-phosphinylphenols in good to high yields. Mechanistically, zinc triflate may serve as an oxophilic σ-Lewis acid to activate the C-O bond in p-quinol ether first. Then the regioselective attack of the phosphorus nucleophile at the α-carbon position takes place to form the C-P bond and give the product. In addition, α-alkynyl substituted p-quinol ethers also react with secondary phosphine oxides in the same reaction mode to give 6-alkynyl 2-phosphinylphenols in the presence of the zinc catalyst.