Pd-catalyzed addition-carbocyclization of α,ω-diynes with H-P(O)R2 compounds

Chelating phosphines are much higher performing than mono-dentate phosphines in palladium-catalyzed reaction of α,ω-diynes with HP(O)R1R2 (R1,R2 = Ph, alkoxy) to afford (E)-3-(phosphorylmethylene)-2-methylcyclopentenes.