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.
![[5-chloro-2-(2-phenylethynyl)phenyl]-ethoxyphosphinate Structure](https://image.chemsrc.com/caspic/140/639517-07-0.png)
