Electrochemical‐In‐Situ‐Oxidative Sulfonylation of Phenols with Sulfinic Acids as an Access to Sulfonylated Hydroquinones

Abstract

The electrochemical in-situ oxidative sulfonylation of phenols with sulfinic acids access to sulfonylated hydroquinones has been developed. A series of sulfonylated hydroquinones were prepared under mild mediator-, catalyst-and exogenous-oxidant-free conditions. Notably, such an electrochemical in-situ-oxidative synthetic strategy presented wide functional group tolerance and amenability to gram-scale synthesis with 62-80% yields.

Sulfinic Acids in Organic Synthesis: A Review of Recent Studies

“…Inexpensive catalysts [4b,5d,9,10a,f,11a,13b,14b,e,20b,21a,b] have been successfully employed in visible‐light‐mediated methods. Electrooxidative conditions [14c,f,15,16,21c,22] were able to provide mild and efficient choices for tandem reactions of sulfinic acids. On the other hand, simple radical initiators, such as pyridine system [2a,5a,7a,8,14a,19] or TBHP, [2e,10b–d,12,13a,17a,b,20a] were frequently utilized in radical reactions solely.…”

“…Compare with para‐substituted aryl sulfinic acids, the yield of ortho‐substituted one was lower (2‐Me, 63%), [21b] which might due to the steric hindance. In 2021, Wen and co‐workers [21c] extended the sulfonylation to phenols at a constant current of 10 mA in an undivided cell, using platinum plate as the anode and graphite rod as the cathode. Benzoquinone intermediates might be involved during the process.…”

“…Aliphatic sulfinic acids were not suitable, while the methyl group in o ‐position of the benzene ring showed an obvious steric effect. He's [21b] and Wen's [21c] work still work in a gram‐scale [21b] (Scheme 15).…”

Ultrasound‐Mediated Monodesulfonation of Polyphenol Sulfonate and One‐Pot Generation of Alkyl Aryl Ether under Solvent‐Free Conditions

“…[11] Sulfonyl-based protecting groups have been involved for protection of phenols for the stability of sulfonates. [12][13][14] Favorable crystallizability of sulfonyl derivatives contributes to the determination of structures of multifunctional compounds. As a viable method, trifluromethylsulfonyl [15,16] and meth-ylsulfonyl-based [17,18] protocol have certain selectivity in monodeprotection, while 4-toluenesulfonyl case, being cost effective and highly stable, is not so widely employed as it can because of long reaction time or the harsh conditions for cleavage of SÀ O of sulfonyl groups and phenols.…”

“…Sulfonyl‐based protecting groups have been involved for protection of phenols for the stability of sulfonates [12‐14] . Favorable crystallizability of sulfonyl derivatives contributes to the determination of structures of multifunctional compounds.…”