Gas–Liquid Segmented Flow Microfluidics for Screening Copper/TEMPO‐Catalyzed Aerobic Oxidation of Primary Alcohols

Abstract

Aerobic oxidation using a combination of copper salts and 2,2,6,6-tetramethylpiperidine Noxyl (TEMPO) represent useful tools for organic synthesis and several closely related catalyst systems have been reported. To gain further insights, these catalytic systems were evaluated in a gasliquid segmented flow device. The improvement of oxygen mass transfer has a significant influence on the turnover-limiting step. Hence, an improved catalytic system using copper(II) as copper source was implemented in a microreactor for the safe and efficient oxidation of primary alcohol.

Liquid phase oxidation chemistry in continuous-flow microreactors

“…170 An improved protocol for the selective aerobic oxidation of primary alcohols by Cu(I)/TEMPO catalysis in micro flow was reported by Favre-Réguillon. 172 Kinetic studies revealed that oxygen showed a first order relationship, which indicates that a higher oxygen concentration could be beneficial. Therefore, the mixture of 9% O2 in N2 was exchanged for a pure oxygen feed.…”

Aerobic Oxidations in Continuous Flow

“…This limitation can be elegantly circumvented by the well-established homogeneous copper-catalyzed aerobic oxidation protocol developed by Stahl using a catalytic mixture of Cu(OTf) 2 , 2,2 0 -bipyridine, TEMPO, and NMI [49]. Similar reactor concepts as for the Pd-catalyzed protocol were used in order to test the feasibility of the copperbased system for continuous purposes [109,110]. Importantly, a stainless steel syringe pump and storage unit for the catalyst mixture caused severe problems since a significant drop in catalytic activity was observed [109].…”

Katalytische, aerobe Oxidation von C(sp3)‐H‐Bindungen

“…Favre‐Réguillon et al. entwickelten eine Methode, die auf segmentiertem Gas‐flüssig‐Fluss in Perfluoralkoxy(PFA)‐Röhren beruht . Darüber hinaus untersuchten Stahl et al.…”