Oxidation of Phenyl-Derived Ethers to Esters via Photocatalytic C-H Activation

Functionalization of the ether fragment is a challenging task for classical organic chemistry. Meanwhile, radical C–H activation of ethers has emerged as a powerful synthetic tool. However, most transformations of this kind are described for aliphatic ethers. Thus, the search for a method of C–H activation of phenol-derived ethers may significantly expand the existing set of synthetic approaches for this class of compounds.

In this work, a method for radical C–H activation of phenol-derived ethers is proposed, affording the corresponding α-halogenated ethers. Subsequent addition of potassium tert-butoxide gives the corresponding α-halogenated ester instead of elimination. In contrast, the mixing of tBuOK with DMSO before the addition led to unsubstituted ester.

As a result, radical bromination of a series of ethers followed by the addition of a base was carried out, a mechanism of radical C–H activation was proposed, and the influence of the alkyl fragment and photocatalyst was investigated. In the second stage, the effect of the amount and nature of the base on the final product was studied. The yields and structures of the products of the first stage were confirmed by NMR spectroscopy. The second stage was monitored by GC. The work was performed with financial support from the Ministry of Science and Higher Education of the Russian Federation.