Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones |
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Authors: | Dr Frédéric Beltran Enrico Bergamaschi Dr Ignacio Funes-Ardoiz Dr Christopher J Teskey |
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Institution: | 1. Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany;2. Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
These authors contributed equally to this work. |
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Abstract: | Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch. |
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Keywords: | homogeneous catalysis cobalt DFT calculations hydroboration selectivity |
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