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Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst
Published on: April 22, 2016
Visible-Light-Promoted Radical Mono- and Bisphosphinylation of Alkynes Under Neutral Conditions
He-Xiang Dang1, Fu Cheng1, Dong-Sen Duan1
1School of Pharmacy and State Key Laboratory of Natural Product Chemistry, Lanzhou University, Lanzhou, China.
None:
A visible-light-driven radical phosphinylation of alkynes under neutral conditions has been developed. This metal-free, redox-neutral protocol enables divergent synthesis, as alkyl alkynes afford 1,2-bisphosphonoethanes, whereas aryl, heteroaryl, or sterically hindered alkynes yield vinylphosphine oxides. The reaction exhibits excellent functional group tolerance and high regioselectivity, providing a green and practical route to valuable bisphosphonates and vinylphosphine oxides without requiring strong bases or transition-metal catalysts. Mechanistic studies indicate a radical pathway initiated by visible-light photolysis.
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Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.

