Integration of Halogen-Atom Transfer with Photoredox/Chromium Dual Catalysis for Carbonyl Addition of Unactivated Alkyl Bromides

Abstract

The development of efficient and sustainable methods for carbonyl addition reactions remains a central focus in organic synthesis. The Nozaki–Hiyama–Kishi (NHK) reaction provides a compelling alternative to classical nucleophilic carbonyl additions with preformed organometallic reagents, and significant advancements have been made over the past decades. However, its application to unactivated halides has long been hindered by their prohibitively negative reduction potentials, which are resistant to single-electron transfer (SET) reduction. Herein, we circumvent this challenge by utilizing a halogen-atom transfer (XAT) strategy, and report a photoredox/Cr dual catalytic system for the carbonyl addition of unactivated alkyl bromides. The key to the success of this reaction is the judicious choice of silanol as the XAT reagent, which enables the transformation of unactivated alkyl bromides into the corresponding alkyl radicals through a silyl radical-mediated XAT process. This protocol operates under mild conditions and exhibits an exceptionally broad substrate scope, and good functional group compatibility, accommodating a wide range of unactivated primary, secondary, and even tertiary alkyl bromides, as well as various alkyl and aryl aldehydes, providing a robust platform for the synthesis of alcohols. Moreover, this method effectively enables the late-stage functionalization of complex molecules derived from natural products and pharmaceuticals, underscoring its practical utility. Preliminary mechanistic investigations suggest a pathway in which alkyl radicals are intercepted by a chromium species through a radical–polar crossover process to form nucleophilic alkyl–chromium(III) complexes that undergo addition to carbonyl compounds. This work further highlights the versatility and broad compatibility of chromium-based cooperative catalytic systems in carbonyl addition chemistry.

Keywords

Photoredox/chromium dual catalysis / Halogen-atom transfer / Unactivated alkyl bromides / Nozaki–Hiyama–Kishi reaction / Radical–polar crossover / Carbonyl addition / Alcohols / Late-stage functionalization

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2026 SIOC, CAS, Shanghai, & WILEY-VCH GmbH