Epoxidation of methyl oleate with molecular oxygen: Implementation of Mukaiyama reaction in flow

Abstract

Continuous‐flow technology with channel dimension in the millimeter region found widespread applications in numerous applications. The epoxidation of methyl oleate with molecular oxygen using an aldehyde as sacrificial reductant (Mukaiyama reaction) was implemented in a segmented flow microreactor. The effect of aldehyde structure and aldehyde/methyl oleate molar ratio on the conversion to epoxides was studied. Total conversion of methyl oleate (0.67 M in heptane) with a selectivity higher than 99% and a cis/trans ratio ∼75/25 was reach in less than 4 min, at room temperature, using three equivalents of 2‐ethylhexanal, 100 ppm of Mn(II) as catalyst and five bar of oxygen. Practical applications: As the result of the small reactor volumes, very high surface‐to‐volume ratio and high heat exchange efficiency compared to classical batch reactors, the overall safety of oxidation processes is significantly improved using continuous‐flow technology. Microreactors also provide better mass transfer, and thus, improve the productivity of the aerobic epoxidation of methyl oleate using aldehyde as sacrificial reductant while maintaining the high selectivity of the process. (i) Epoxidation of methyl oleate with molecular oxygen is performed safely using continuous‐flow technology. (ii) Total conversion is obtained in 4 min at r.t. using 100 ppm of Mn(II) and a sacrificial reductant. (iii) The selectivity and cis/trans ratio are comparable to batch.

One-Pot Conversion of Epoxidized Soybean Oil (ESO) into Soy-Based Polyurethanes by MoCl2O2 Catalysis

“…In this context, special attention has been paid to oxidation methods employing organocatalysts [ 14 , 15 ] or based on mild and safe oxidants, such as H 2 O 2 [ 16 , 17 ] organic (hydro)peroxides [ 18 , 19 , 20 ] and even O 2 [ 21 ]. On the other hand, typical protocols prescribe the use of strong Brønsted acids (e.g., p -Toluene sulfonic acid SA, H 3 PO 4 , and HBF 4 ) to catalyze the epoxide ring-opening reaction step, while hazardous Lewis acids (e.g., tin-, mercury-compounds) and/or toxic bases (e.g., tertiary amines) are usually employed in the formation of urethane linkages [ 22 , 23 , 24 ].…”

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

“…Additionally, the system requires lower catalyst loading compared to the batch approach (0.1 mol % vs 100 ppm) and quantitative conversion and high selectivity (>99%). The same system was also explored for the epoxidation of several fatty acids [ 336 ].…”

Flow Chemistry for Cycloaddition Reactions

“…The same group did the epoxidation with methyl oleate as an example of an unsaturated fatty materials. With similar conditions, a mixture of cis ‐ and trans ‐epoxides of methyl oleate (25/75) were prepared in less than 4 min with a >99 % selectivity toward the epoxide …”