Rapid Access to Free Phenols by Photocatalytic Acceptorless Dehydrogenation of Cyclohexanones at Room Temperature

Phenols are ubiquitous substructures in natural products and bioactive compounds. However, practical methods for the direct construction of phenols under mild conditions remain challenging. Herein, a photocatalytic acceptorless hydrogen-evolution aromatization of cyclohexanones or cyclohexenones at room temperature has been developed. The reaction features the visible-light and cobalt co-catalyzed sequential dehydrogenation of in-situ formed enol silyl ethers, which are regarded as a challenging process. This operationally simple method enables the synthesis of a series of phenols with diverse substitution patterns from cyclohexanones or cyclohexenones. Moreover, diverse substituted 1,2-, 1,3-, and 1,4-benzenediols were obtained from cyclohexanediones, providing a general and straightforward method for the synthesis of phenols from simple starting materials under mild conditions.