81801-17-4Relevant articles and documents
Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
supporting information, p. 21176 - 21182 (2020/09/17)
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.
Fungi-mediated biotransformation of the isomeric forms of the apocarotenoids ionone, damascone and theaspirane
Serra, Stefano,De Simeis, Davide
, (2019/01/16)
In this work, we describe a study on the biotransformation of seven natural occurring apocarotenoids by means of eleven selected fungal species. The substrates, namely ionone (α-, β- and γ-isomers), 3,4-dehydroionone, damascone (α- and β-isomers) and theaspirane are relevant flavour and fragrances components. We found that most of the investigated biotransformation reactions afforded oxidized products such as hydroxy- keto- or epoxy-derivatives. On the contrary, the reduction of the keto groups or the reduction of the double bond functional groups were observed only for few substrates, where the reduced products are however formed in minor amount. When starting apocarotenoids are isomers of the same chemical compound (e.g., ionone isomers) their biotransformation can give products very different from each other, depending both on the starting substrate and on the fungal species used. Since the majority of the starting apocarotenoids are often available in natural form and the described products are natural compounds, identified in flavours or fragrances, our biotransformation procedures can be regarded as prospective processes for the preparation of high value olfactory active compounds.
Selective Base-free Transfer Hydrogenation of α,β-Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source
Farrar-Tobar, Ronald A.,Wei, Zhihong,Jiao, Haijun,Hinze, Sandra,de Vries, Johannes G.
supporting information, p. 2725 - 2734 (2018/02/28)
Commercially available Ru-MACHOTM-BH is an active catalyst for the hydrogenation of several functional groups and for the dehydrogenation of alcohols. Herein, we report on the new application of this catalyst to the base-free transfer hydrogenation of carbonyl compounds. Ru-MACHOTM-BH proved to be highly active and selective in this transformation, even with α,β-unsaturated carbonyl compounds as substrates. The corresponding aliphatic, aromatic and allylic alcohols were obtained in excellent yields with catalyst loadings as low as 0.1–0.5 mol % at mild temperatures after very short reaction times. This protocol tolerates iPrOH and EtOH as hydrogen sources. Additionally, scale up to multi-gram amounts was performed without any loss of activity or selectivity. An outer-sphere mechanism has been proposed and the computed kinetics and thermodynamics of crotonaldehyde and 1-phenyl-but-2-en-one are in perfect agreement with the experiment.
