title: Metal-free C-H bond activation of branched aldehydes with a hypervalent iodine(III) catalyst under visible-light photolysis: successful trapping with electron-deficient olefins.
abstract: Direct acyl radical formation of linear aldehydes (RCH2-CHO) and subsequent hydroacylation with electron-deficient olefins can be effected with various types of metal and nonmetal catalysts/reagents. In marked contrast, however, no successful reports on the use of branched aldehydes have been made thus far because of their strong tendency of generating alkyl radicals through the facile decarbonylation of acyl radicals. Here, use of a hypervalent iodine(III) catalyst under visible light photolysis allows a mild way of generating acyl radicals from various branched aldehydes, thereby giving the corresponding hydroacylated products almost exclusively. Another characteristic feature of this approach is the catalytic use of hypervalent iodine(III) reagent, which is a rare example on the generation of radicals in hypervalent iodine chemistry.
authors.affiliation: Laboratory of Synthetic Organic Chemistry and Special Laboratory of Organocatalytic Chemistry, Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502 (Japan).
authors.forename: Shin A
authors.initials: SA
authors.lastname: Moteki
authors.forename: Asuka
authors.initials: A
authors.lastname: Usui
authors.forename: Sermadurai
authors.initials: S
authors.lastname: Selvakumar
authors.forename: Tiexin
authors.initials: T
authors.lastname: Zhang
authors.forename: Keiji
authors.initials: K
authors.lastname: Maruoka
keywords: aldehydes; hypervalent compounds; iodine; photochemistry; radicals