Radical Deoxygenative Alkynylation Reactions Of Tertiary Alcohols Via Visible-Light Photoredox Catalysis

Alcohols are widely exist in nature,and have been broadly used.Therefor,compared with traditional reactants such as halide,alcohols have great potential for application.Compare to primary and secondary alcohols,tertiary alcohols have relatively larger steric resistance,lower reactivity,and easy to elimination,resulting in higher reaction difficulty and lower efficiency.At the same time,through the conversion of tertiary alcohols,a series of compounds that contain quaternary carbon centres,which cannot be synthesized usually,can be generated.So it has high research value for the activation of tertiary alcohols.Recently,visible light catalysis has entered a period of rapid development.Because of its high efficiency,green and mild,it has been widely concerned by chemists.In this paper,we design to use cesium salts of tertiary alcohol oxalate monoester to activate tertiary alcohol,using photocatalyst to achieve coupling reaction with alkyne based high iodine reagent.In order to prepare a series of non terminal alkynes containing quaternary carbon center.Firstly,we established the optimal reaction conditions through investigation:using Ir[dF(CF3)ppy]2(dtbbpy)PF6 as photocatalyst,dioxane as solvent,water as additive,under 28W white CFL at room temperature.Though examination of substrate scope,we found that the substituents of alkynyl reagent had a gread impact,and the reaction cannot occur if the tertiary carbon radical were too stable.Finally,we obtained the target compounds in medium to good yields,and determined by NMR.And we also tried deoxygenative carobonylative alkynylation reaction.However,after systematic screening,the efficiency of this reaction is not very high.Maybe due to the difficulty of tertiary center radical react with carbon monoxide.