Anti-Markovnikov hydration of alkenes over platinum-loaded titanium oxide photocatalyst

Hydration of various alkenes proceeded over a platinum-loaded titanium oxide photocatalyst. It is notable that, unlike conventional acid-catalysts, the photocatalyst preferentially promoted the hydration according to the anti-Markovnikov rule. The results of some reaction experiments and semiempirical molecular orbital calculations suggested the reaction path of this hydration as follows: an electrophilic surface oxygen radical species formed on the photoexcited titanium oxide attacks a carbon double bond of the alkene to produce an intermediate, followed by the addition of a hydrogen radical formed on the platinum sites to produce an alcohol. The anti-Markovnikov selectivity for each investigated alkene would be determined by the stability of the radical intermediate.