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

A copper‐catalyzed α,β‐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 α,β‐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 α,β‐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 α,β‐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.