Tuning selectivity among acetalization, pinacol coupling, and hydrogenation reactions of benzaldehyde by catalytic and photochemical pathways at room temperature

Benzaldehyde is one of the industrially most useful feedstocks, and its transformation to high-value chemicals very attractive. Different transformations benzaldehyde, such as acetalization, pinacol coupling, hydrogenation, have been achieved herein by adjusting pH, light source, selection a catalyst. Consequently, corresponding products obtained with excellent yields (e.g. 92% yield for 96% 85% hydrogenation). The mechanisms behind each were studied, it revealed that coupling reaction was through photochemical process under 365 nm irradiation at pH 12, where introduction TiO2 (P25) catalyst would completely shift selectivity toward benzyl alcohol photocatalytic pathway benzaldehyde dimethyl acetal via low-temperature thermal catalysis.