Metal–organic frameworks-TiO2 as a recyclable photocatalyst for the synthesis of acetals/ketals

Abstract

Carbonyl compounds are the most critical skeletons in organic synthesis owing to their ubiquitous and versatile reactivities. For instance, ketals and acetals may be employed as carbonyl-protecting groups, and several synthetic methods of preparing ketals and acetals have been reported in the recent decades. However, most of these transformations exhibit several limitations such as long reaction time, harsh reaction conditions, tedious workup procedures and unrecoverable catalyst, etc. Therefore, developing a novel metal–organic framework (MOFs)-TiO2 as an efficient, recyclable photocatalyst for converting carbonyl compounds to acetals/ketals is critical. We demonstrate the efficient acetalisations of carbonyl compounds, enabling access to a wide variety of acyclic/cyclic acetals, ketals or thioacetal by using various aromatic or aliphatic aldehydes/ketones under blue light. This strategy exhibits striking features, such as the use of abundant, sustainable alcohols as solvents and coupling agents, excellent yields, a recyclable photocatalyst and broad substrate scope. Therefore, this strategy may be applied in broadly green catalytic systems in industry.