β-Scission of Tertiary Alcohols on a Platinum-Loaded Titanium Dioxide Photocatalyst for C─C Bond-Forming Reactions.

Here, we report the β-scission of nonactivated tertiary (3°) alcohols using a Pt-loaded TiO2 (Pt/TiO2) photocatalyst in the absence of external oxidants or additives. This method generates various C-centered radicals, including methyl and acyl radicals, which undergo subsequent C─C bond-forming reactions. Density functional theory (DFT) calculations suggest that the selectivity of C─C bond cleavage can be predicted according to the relative thermodynamic favorability among competing β-scission pathways. Competition experiments showed that the β-scission of a 3° alcohol is suppressed in the presence of a carboxylic acid, where then decarboxylation of the carboxylic acid predominates. These results were attributed to the less favorable adsorption of the 3° alcohol on TiO2 relative to that of the carboxylic acid. By leveraging the adsorption-controlled reaction kinetics, a synthetic strategy involving decarboxylation, and subsequent β-scission was developed, which enabled the sequential incorporation of two different components into a substrate that contains a carboxylic acid and a 3° alcohol moiety. This work thus showcases the unique reactivity and selectivity of the Pt/TiO2-photocatalyzed β-scission of 3° alcohols, offering a new and distinctive addition to the toolkit of the modern organic chemist (186/200).