Selective alkane C-H-bond functionalizations utilizing oxidative single-electron transfer and organocatalysis

Alkane C-H-bond functionalization methods not utilizing metal-catalysis are discussed based on experimental and computational data, beginning with molecule-induced homolysis (reactions of alkanes with dioxiranes). Electrophilic reactions are elaborated next with an emphasis on mechanistic details that reveal that many so-called electrophilic C-H or C-C-bond insertions can be rationalized by electron-transfer reactions (inner sphere, H-coupled, and outer sphere). Finally, radical functionalizations utilizing carbon-centered (relatively stable) radicals generated under organocatalytic (phase-transfer catalysis, PTC) conditions are presented as valuable alternatives to other radical-chain alkane functionalizations. The remarkable chemo- and regioselectivities of these PTC radical reactions and the tolerance of high strain in certain aliphatic hydrocarbons make them particularly useful for laboratory-scale halogenations, in particular, iodinations of unactivated alkane C-H-bonds. (C) 2004 The Japan Chemical journal Forum and Wiley Periodicals, Inc. Chem Rec 3: 247-257; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10070.