Copper-Catalyzed α,β-Regioselective (2+4) Cycloaddition of Propargylic Esters

A copper-catalyzed alpha,beta-regioselective (2+4) cycloaddition of propargylic esters with o-hydroxyphenyl substituted secondary phosphine oxides (SPOs) was established, which afforded a series of phosphorus-containing six-membered heterocycles in high yields. This reaction represents the first alpha,beta-regioselective (2+n) cycloaddition of propargylic esters via the intermediates of copper-allenylidenes, which will enrich the chemistry of propargylic esters and copper-allenylidenes. Moreover, this work also represents the first application of o-hydroxyphenyl substituted SPOs as 1,4-dinucleophiles in (2+4) cycloadditions, which provides a useful protocol for the synthesis of phosphorus-containing six-membered heterocycles with potential bioactivity. A copper-catalyzed alpha,beta-regioselective (2+4) cycloaddition of propargylic esters with o-hydroxyphenyl substituted secondary phosphine oxides (SPOs) was established, which afforded phosphorus-containing six-membered heterocycles in high yields. This reaction not only represents the first alpha,beta-regioselective (2+n) cycloaddition of propargylic esters via the intermediates of copper-allenylidenes, but also represents the first application of o-hydroxyphenyl substituted SPOs as 1,4-dinucleophiles in (2+4) cycloadditions.image