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Issue 2, 2018
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Continuous flow oxidation of benzylic and aliphatic alcohols using bleach: process improvement by precise pH adjustment in flow with CO2

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Abstract

An improved method for the oxidation of benzylic and aliphatic alcohols using concentrated bleach (1.6 M NaOCl) using 2-step continuous flow microreactors is reported herein. Enhancement of the reaction rate was obtained by on-line pH adjustment. In the first step, the pH of the bleach was precisely decreased to pH 8.5 using CO2. Such pH is a compromise between oxidative properties, chemical stability and unwanted precipitation. The aqueous bleach solution was subsequently used for the oxidation of benzyl alcohols in EtOAc using catalytic amounts of TBAB (n-Bu4N+Br) in a segmented flow microreactor. The total conversion of benzyl alcohols was obtained in less than 1 min using 2 eq. of NaOCl at r.t. without any metal catalysts. Selective benzyl alcohol oxidation (>98%) was demonstrated on primary and secondary alcohols. For aliphatic alcohols, 0.1 mol% TEMPO was used as a co-catalyst in synergy with TBAB and a total conversion with high selectivity (>98%) was achieved in less than 2 min.

Graphical abstract: Continuous flow oxidation of benzylic and aliphatic alcohols using bleach: process improvement by precise pH adjustment in flow with CO2

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Publication details

The article was received on 26 Sep 2017, accepted on 23 Jan 2018 and first published on 23 Jan 2018


Article type: Paper
DOI: 10.1039/C7RE00155J
Citation: React. Chem. Eng., 2018,3, 188-194
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    Continuous flow oxidation of benzylic and aliphatic alcohols using bleach: process improvement by precise pH adjustment in flow with CO2

    L. Vanoye, L. Yehouenou, R. Philippe, C. de Bellefon, P. Fongarland and A. Favre-Réguillon, React. Chem. Eng., 2018, 3, 188
    DOI: 10.1039/C7RE00155J

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