Direct Solar Energy-Mediated Synthesis of Tertiary Benzylic Alcohols Using a Metal-Free Heterogeneous Photocatalyst

Direct hydroxylation via the functionalization of tertiary benzylic C(sp(3))-H bonds is of great significance for obtaining tertiary alcohols, which find wide applications in pharmaceuticals as well as in fine chemical industries. However, current synthetic procedures use toxic reagents, and therefore, the development of a sustainable strategy for the synthesis of tertiary benzylic alcohols is highly desirable. To solve this problem, herein, we report a metal-free heterogeneous photocatalyst to synthesize the hydroxylated products using oxygen as the key reagent. Various benzylic substrates were employed into our mild reaction conditions to afford the desirable products in good to excellent yields. More importantly, the gram-scale reaction was achieved via harvesting direct solar energy and exhibited high quantity of the product. The high stability of the catalyst was proved via recycling the catalyst and spectroscopic analyses. Finally, a possible mechanism was proposed based on electron paramagnetic resonance and other experimental evidence.

Automated summary

In this study, a metal-free heterogeneous photocatalyst was developed for the direct hydroxylation of tertiary benzylic C(sp(3))-H bonds using oxygen as the key reagent. The gram-scale reaction was achieved with high product yield using direct solar energy. The high stability of the catalyst was proven through catalyst recycling and spectroscopic analyses, and a possible mechanism was proposed based on experimental evidence.