Hydride transfer reactions are of significance in both academic and industrial fields. A variety of hydrogen donors and acceptors have been well organized and discussed, especially in the field of [1,5]-hydride transfer/cyclization reactions. The intramolecular Cannizzaro reaction of α-keto aldehydes is by nature a [1,2]-hydride transfer reaction. The asymmetric intramolecular Cannizzaro reaction of α-keto aldehydes is an efficient access to optically active α-hydroxy carboxylic acids and derivatives. In order to achieve such transformation, a green catalyst chiral N,N'-dioxide/FeCl3 was developed. Aryl and alkyl glyoxal monohydrates were applied to obtain α-hydroxy acid esters with excellent results. Control experiments shed light on the reaction mechanism. Unlike former proposed, the reaction can undergo both dynamic kinetic resolution process and asymmetic addition process. Meerwein-Ponndorf-Verley (MPV) reaction is an intermolecular hydride transfer between aluminium isopropoxide and carbonyl compounds. Catalytic asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of simple ketones has achieved some progresse, but, the catalytic asymmetric reaction of other ketones has not been explored. A non-aluminium catalyst, chiral N,N'-dioxide/Y(III) was applied in reducing glyoxylates. Aluminium alkoxide and molecular sieve (MS) were found crucial for this reaction. A variety of optical active α-hydroxyesters were obtained with excellent results. Control experiments, HRMS analysis and kinetic informations all suggested that the additive aluminium alkoxide may be the reductant in the hydride transfer process.

Asymmetric intramolecular Cannizzaro reaction and MPV reaction: Hydride transfer reactions enabled by Lewis acid catalysis

256th National Meeting (2018)

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