Continuous Flow Chemo-Enzymatic Baeyer–Villiger Oxidation with Superactive and Extra-Stable Enzyme/Carbon Nanotube Catalyst: An Efficient Upgrade from Batch to Flow

• Published in: Organic process research & development Vol. 23; no. 7; pp. 1386 - 1395
• Main Authors: Szelwicka, Anna, Zawadzki, Przemysław, Sitko, Magdalena, Boncel, Sławomir, Czardybon, Wojciech, Chrobok, Anna
• Format: Journal Article
• Language: English
• Published: American Chemical Society 19.07.2019
• Subjects: (nano)biocatalyst; carbon nanotubes; lipase; chemo-enzymatic Baeyer−Villiger oxidation; flow chemistry
• ISSN: 1083-6160; 1520-586X
• DOI: 10.1021/acs.oprd.9b00132

Continuous flow chemo-enzymatic Baeyer–Villiger oxidation in the presence of exceptionally active Candida antarctica lipase B immobilized via simple physical adsorption on multiwalled carbon nanotubes has been investigated. The nanobiocatalyst was used to generate peracid in situ from ethyl acetate and 30 wt % aq. hydrogen peroxide as the primary oxidant. Application of the highly stable and active nanobiocatalyst in the Baeyer–Villiger oxidation of 2-methylcyclohexanone to 6-methyl-ε-caprolactone after 8 h at 40 °C led to a high product yield (87%) and selectivity (>99%). Environmentally friendly ethyl acetate was applied as both solvent and the peracid precursor. To determine the most favorable reaction conditions, a series of experiments using various parameters was performed. The main contribution of this work is that it describes the first application of the nanobiocatalyst in a chemo-enzymatic Baeyer–Villiger oxidation in a flow system. Since the process was performed in a flow reactor, many improvements were achieved. First of all, substantially shorter reaction times as well as a significant increase in the product yield were obtained as compared to the batch process. Since peracids are unstable, a large increase in the safety of the process was demonstrated under mild conditions in this work. In summary, this work shows a particularly efficient upgrade in the studied processes by transfer from a batch to a flow system.