A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed-bed microreactor

Abstract

SummaryWe demonstrate the preparation and characterization of a simplified packed-bed microreactor using an immobilized TEMPO catalyst shown to oxidize primary and secondary alcohols via the biphasic Anelli-Montanari protocol. Oxidations occurred in high yields with great stability over time. We observed that plugs of aqueous oxidant and organic alcohol entered the reactor as plugs but merged into an emulsion on the packed-bed. The emulsion coalesced into larger plugs upon exiting the reactor, leaving the organic product separate from the aqueous by-products. Furthermore, the microreactor oxidized a wide range of alcohols and remained active in excess of 100 trials without showing any loss of catalytic activity.

Liquid phase oxidation chemistry in continuous-flow microreactors

“…Another way to promote excellent mixing between biphasic systems, was demonstrated by McQuade et al 319 The TEMPO catalyst was immobilized on a commercially available resin (AMBERZINE® Oxirane) and was packed in polymer tubing (1.2 mL). A liquid-liquid slug flow was formed between the aqueous bleach phase and organic alcohol phase before entering the packed bed.…”

Flow chemistry vs. flow analysis

“…3 mm (Fig.3B) [32]. Another example of such reactors is a packed-bed microreactor developed for a biphasic oxidation of alcohols to aldehydes and ketones [33] where flow reactions were performed in 60 cm 1.6 mm I.D. fluoroelastomeric tubing packed with appropriate resin.…”

Managing Hazardous Reactions and Compounds in Process Chemistry

“…Safety issues can be reduced when flow methodology is used for this powerful reagent. TEMPO can be immobilized for use in a continuous process (325). TEMPO is often used in substoichiometric amounts to reduce safety problems.…”