Acridine Orange Hemi(Zinc Chloride) Salt as a Lewis Acid-Photoredox Hybrid Catalyst for the Generation of α-Carbonyl Radicals,Advanced Synthesis & Catalysis

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Acridine Orange Hemi(Zinc Chloride) Salt as a Lewis Acid-Photoredox Hybrid Catalyst for the Generation of α-Carbonyl Radicals
Advanced Synthesis & Catalysis ( IF 4.4 ) Pub Date : 2021-11-22 , DOI: 10.1002/adsc.202101053
Sanju Das ₁ , Tanumoy Mandal ₁ , Suman De Sarkar ₁

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A readily accessible organic-inorganic hybrid catalyst is reported for the reductive fragmentation of α-halocarbonyl compounds. The robust hybrid catalyst is a self-stabilizing combination of ZnCl₂ Lewis acid and acridine orange as the photoactive organic dye. Mechanistic specifics of this hybrid catalyst have been studied in detail using both photophysical and electrochemical experiments. A systematic study enabled the discovery of the appropriate Lewis acid for the effective LUMO stabilization of α-halocarbonyl compounds and thereby lowering of reduction potential within the range of a standard organic dye. This strategy resolves the issues like dehalogenative hydrogenation or homo-coupling of alkyl radicals by guiding the photoredox cycle through an oxidative quenching pathway. The cooperativity between the photoactive organic dye and the Lewis acid counterparts empowers functionalization with a wide range of coupling partners through efficient and controlled generation of alkyl radicals and serves as an appropriate alternative to the expensive late transition metal-based photocatalysts. To demonstrate the application potential of this cooperative catalytic system, four different synthetic transformations of α-carbonyl bromides were explored with broad substrate scopes.

中文翻译：

吖啶橙半（氯化锌）盐作为路易斯酸-光氧化还原杂化催化剂用于生成 α-羰基自由基

据报道，一种易于获得的有机-无机杂化催化剂用于α-卤代羰基化合物的还原断裂。稳健的杂化催化剂是 ZnCl ₂ Lewis 酸和吖啶橙作为光活性有机染料的自稳定组合。已经使用光物理和电化学实验详细研究了这种混合催化剂的机械特性。一项系统的研究使我们能够发现合适的路易斯酸以有效地稳定α-卤代羰基化合物，从而降低标准有机染料范围内的还原电位。该策略通过引导光氧化还原循环通过氧化猝灭途径解决了脱卤氢化或烷基自由基同源偶联等问题。光活性有机染料和路易斯酸对应物之间的协同作用通过有效和受控地生成烷基自由基，使功能化与广泛的偶联伙伴成为可能，并作为昂贵的后过渡金属基光催化剂的合适替代品。为了证明这种协同催化体系的应用潜力，研究了四种不同的α-羰基溴的合成转化，具有广泛的底物范围。

更新日期：2021-11-22

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