Visible-Light-Mediated Deoxyalkynylation of Activated Tertiary Alcohols

Abstract

In this paper, visible-light-induced deoxyalkynylation of activated tertiary alcohols has been successfully performed under mild reaction conditions with ethynylbenziodoxole as the readily available alkynylation reagent. The desired C(sp 3 )−C(sp) coupling can smoothly occur with 4-CzIPN as a photocatalyst, affording a wide range of valuable alkynylation products bearing quaternary carbon centers in 37−84% yields.

Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions**

“…In the case of the deoxyalkynylation of oxalates, we also developed a photocatalytic approach using 4CzIPN ( 2 a ) as organophotocatalyst and accessed an extended scope of alkynylated quaternary centers. [24] The direct excitation approach discovered in our work results in simplified reaction design and will therefore facilitate the discovery of new alkynylation reactions using ArEBX reagents, as demonstrated in the case of deoxy‐ and deamino‐alkynylation. [25]…”

“…We have discovered the direct photoexcitation of aryl EBX reagents in the context of the deoxyalkynylation of cesium oxalates.T he broad applicability of the direct excitation of ArEBXs was then exemplified in alkynylation processes requiring ap hotocatalyst before,i ncluding decarboxylative and deboronative alkynylations,t he oxyalkynyla-tion of enamides and the CÀHa lkynylation of THF.T he direct excitation of ArEBXs has also enabled afirst example of deaminative alkynylation via an aryl imine.I nt he case of the deoxyalkynylation of oxalates,wealso developed aphotocatalytic approach using 4CzIPN (2a)asorganophotocatalyst and accessed an extended scope of alkynylated quaternary centers. [24] Thed irect excitation approach discovered in our work results in simplified reaction design and will therefore facilitate the discovery of new alkynylation reactions using ArEBX reagents,a sd emonstrated in the case of deoxy-and deamino-alkynylation. [25]…”

Updates on hypervalent-iodine reagents: metal-free functionalisation of alkenes, alkynes and heterocycles

“…This alkynynation strategy has certain advantages such as mild reaction conditions, being external oxidant free, and a broad substrate scope with good functional group compatibility. 74…”

“…This alkynynation strategy has certain advantages such as mild reaction conditions, being external oxidant free, and a broad substrate scope with good functional group compatibility. 74 A recent report by Waser et al described the direct excitation of aryl-substituted EBX reagents by visible light irradiation. This strategy allows EBX reagents to act both as an oxidant and radical trapper without the requirement of any photocatalyst as reported in common EBX-mediated processes such as decarboxylative and deboronative alkynylations, oxy-…”

Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions**

“…We have discovered the direct photoexcitation of aryl EBX reagents in the context of the deoxyalkynylation of cesium oxalates.T he broad applicability of the direct excitation of ArEBXs was then exemplified in alkynylation processes requiring ap hotocatalyst before,i ncluding decarboxylative and deboronative alkynylations,t he oxyalkynyla-tion of enamides and the CÀHa lkynylation of THF.T he direct excitation of ArEBXs has also enabled afirst example of deaminative alkynylation via an aryl imine.I nt he case of the deoxyalkynylation of oxalates,wealso developed aphotocatalytic approach using 4CzIPN (2a)asorganophotocatalyst and accessed an extended scope of alkynylated quaternary centers. [24] Thed irect excitation approach discovered in our work results in simplified reaction design and will therefore facilitate the discovery of new alkynylation reactions using ArEBX reagents,a sd emonstrated in the case of deoxy-and deamino-alkynylation. [25] Stichwçrter: alkynes •h ypervalent iodine •p hotochemistry • quaternary centers •s ynthetic methods…”