Direct and Unified Access to Carbon Radicals from Aliphatic Alcohols by Cost‐Efficient Titanium‐Mediated Homolytic C−OH Bond Cleavage

Abstract

Low‐valent Ti‐mediated homolytic C−O bond cleavage offers unified access to carbon radicals from ubiquitous non‐activated tertiary, secondary, and even primary alcohols. In contrast to the representative Ti reagents, which were ineffective for this purpose, “TiCl2(cat)”/Zn (cat=catecholate) was found to be specifically active. This method was applied to the addition reactions of radicals to alkenes and exhibited high generality and yields. More than 50 combinations were examined. The excellent cost‐efficiency and accessibility of “TiCl2(cat)”/Zn further enhance its applicability. Control experiments proved the presence of a carbon radical intermediate and excluded the pathway via alkyl chlorides. Further mechanistic study indicated that the 1 : 2 complex of alkoxide (R−O−) and TiIII is an active species in the C−O cleavage.

Divergence in CH alkylation of indoles under Mn catalysis

“…Notably, the total number of available commercial alcohols is much higher than the number of alkyl halides. 8 Likewise, C3 alkylation of indoles has been explored under borrowing hydrogen catalysis using precious transition metal catalysts such as Pd, Ir, and Ru. 9 Recently, earth-abundant first-row transition metal complexes of Co, Mn, Fe, Cu, etc., with an elegant ligand backbone, have been used as an alternative to these expensive catalysts.…”