Stereoselective free-radical addition of secondary phosphine selenides to aromatic acetylenes

Free-radical addition (AIBN, 65–70 °C, 5–7 h) of secondary phosphine selenides to arylacetylenes proceeds stereoselectively to give anti-Markovnikov adducts of predominantly Z-configuration (up to 97%) in 60–80% isolated yields, thus representing a rare example of stereoselective free-radical addition to the triple bond. Microwave irradiation (600 W) of the reactants with the same content of AIBN reduces the reaction time to 8 min though compromises the stereoselectivity. Under UV-initiation the reaction loses its stereoselectivity due to isomerization of the primary Z-adducts. In this reaction, a specific facilitating and Z-configuration-controlling effect of aromatic substituents at the triple bond has been revealed.

Reported herein are the stereoselective free-radical additions (AIBN, 65–70 °C) of secondary phosphine selenides to aromatic and heteroaromatic acetylenes. UV irradiation of the reactants distorts stereoselectivity due to isomerization of the primary Z-adducts. Microwave activation of the process allows the reaction time to be reduced significantly.Figure optionsDownload as PowerPoint slide