Giese Reactions Of Alkanes Utilizing Alcohols As Hydrogen Atom Transfer Agents

Alkyl radicals with high reactivity,distinctive chemical selectivity and stereoselectivity are widely used in radical reactions.How to efficiently and selectively obtain alkyl radicals under mild conditions and further obtain various functionalized products has always been one of the most challenging scientific problems faced by synthetic chemists.Among them,the activation and breaking of C–H bonds is the most direct and efficient way to obtain alkyl radicals.In recent years,visible light-induced HAT using hydrogen atom transfer reagents provides a green and efficient method for directly activating and breaking C–H bond to generate alkyl radicals.At present,there are few studies on alcohols as hydrogen atom transfer reagents,and current methods usually require the use of transition metal photocatalysts or strong oxidants,which limits its application in organic synthesis.In response to above scientific issues,this thesis presents a cooperative catalytic system of the organic photocatalyst 4Cz IPN and the sulfur-containing small organic molecule thianthrene for generation of alkoxy radicals direct from alcohols inducted by visible light.The Giese reactions of alkanes and a variety of electron-deficient alkenes were achieved upon using alkoxy radicals as hydrogen atom transfer reagents.The reaction can be performed under mild conditions,avoiding the use of transition metal photocatalysts and strong oxidants,to provide the corresponding products in medium to good yields.Mechanism studies show that the excited photocatalyst 4Cz IPN first oxidizes thianthrene to generate stable free radical cations,the free radical cation reacts with the deprotonated alcohol to obtain a sulfur radical intermediate,then generate alkoxy radicals through O–S bond cleavage and regenerate thianthrene,which makes thianthrene circulate in the reaction system as a catalyst.This thesis develops the Giese reaction of alkanes with alkenes by applying thianthrene as a co-catalyst and alcohols as hydrogen atom transfer agents,which builds a new bridge for organic photocatalyst 4Cz IPN with low oxidation potential to activate alcohols,and provides a more green and efficient way for the generation of alkoxy radicals and the activation of C-H bonds.