康 · 学术 | Reaction of the Day No. 1720

Partial Hydrogenation of Aryl-Substituted Benzothiophenes, Benzofurans and Indoles by Photocatalytic Water Activation

Robin Mayska and Armido Studer*

Organisch-Chemisches Institut, Universit?t Mu?nster, Germany

—JACS Au 2026, DOI: 10.1021/jacsau.6c00756

Recommended by Bing Han_MC3

KEY WORDS: photo chemistry, Partial Hydrogenation (反应类型), benzofurans, indoles, benzothiophenes,water (原料), 2,3-dihydrobenzothiophenes, aryl substituted DHBTs (产物), Csp3-H (成键类型), [Ir(dF(CF3)ppy)2(dtbbpy)]PF6,  phosphine (其它) 

ABSTRACT: Transition-metal-catalyzed hydrogenation of heteroarenes provides direct access to three-dimensional, semisaturated scaffolds but remains particularly challenging for sulfur-containing compounds due to catalyst poisoning and undesired desulfurization. As a result, general methods for the direct catalytic hydrogenation of aryl-substituted benzothiophenes to the corresponding 2,3- dihydrobenzothiophenes (DHBTs) are lacking. Herein, we report a photocatalytic phosphine-mediated radical hydrogenation using water as the hydrogen source, enabling direct access to DHBTs. The generality of this method was demonstrated by a broad substrate scope, including diverse aryl- and heteroaryl-substituted substrates as well as related benzofurans, indoles, and other N-heterocycles. Gram-scale and deuteration experiments further highlight the practicality of this approach.

Background

Initial Results and Control Experiments

Substrate Scope (Selected Examples)

Gram Scale Experiment and Deuteration Experiment

Proposed Mechanism

Summary and Comments

Prof. Armido Studer and his co-workers reported a photocatalytic phosphine-mediated radical hydrogenation method that enables the partial hydrogenation of aryl-substituted BTs using water as the hydrogen source, providing direct access to the corresponding DHBTs. The generality of this approach was demonstrated by a broad substrate scope, including various aryl- and heteroaryl-substituted substrates and related benzofurans, indoles, and N-heterocycles. Taken together, this work provides a complementary strategy to established hydrogenation methods, enabling access to aryl substituted DHBTs that were previously difficult to obtain.