Recent Advances of Oxidative Radical Cross‐Coupling Reactions: Direct α‐C(sp³)–H Bond Functionalization of Ethers and Alcohols

Abstract

Oxygen-containing heterocycles are an importantc lass of compounds with diverse biological activities.

Radical condensation between benzylic alcohols and acetamides to form 3-arylpropanamides

“…Replacing the base with sodium tert-butoxide again gave exclusive formation of amide 2 although in a slightly lower yield due to some unreacted alcohol remaining (entry 14). A number of other bases were also included in the study, but very poor results were obtained in all cases (entries [15][16][17][18][19][20][21]. Consequently, the optimum conditions for the condensation uses 2 equiv.…”

“…It has been debated whether potassium tert-butoxide is able to serve as a single electron donor to form the alkoxyl radical, 11 which would rapidly remove an a-hydrogen atom from A. 19 As an example, potassium tert-butoxide reduces benzophenone under photoexcitation conditions to the benzophenone ketyl radical anion. 20 Our transformation, however, is not affected by light and instead potassium tert-butoxide may perform an additional deprotonation of A to form the dianion PhCHO 2À .…”

Visible light-induced direct α C–H functionalization of alcohols

“…For example, remarkable works on the cross-coupling between alcohols with unsaturated bonds such as alkenes, allenes and alkynes have been extensively reported 32–40 , providing effective routes for α sp 3 C–H activation and functionalization of alcohols. Furthermore, oxidation-induced C–H functionalization as a powerful tool 41–48 , is successfully applied in the α sp 3 C–H functionalization of alcohols 49–58 . Direct oxidative α sp 3 C–H arylation by C–H/C–H cross-coupling to acquire the modified alcohols is undoubtedly the most step- and atom-economical method.…”

Recent Advances in Functionalization of α‐C(sp3)–H Centres in Inactivated Ethers through Cross Dehydrogenative Coupling

“…α‐C–H functionalization in such inactivated ethers is a challenging task but is of great significance, because these systems constitute important units in many biologically active natural products . Many reports that depict carbon–carbon and carbon–heteroatom bond formation under oxidative conditions in these substrates have appeared , , . In this account we summarize only cross dehydrogenative coupling reactions resulting in C–C, C–O and C–N bond formation in these ethers.…”