Technical production of aldehydes by continuous bleach oxidation of alcohols catalyzed by 4-hydroxy-TEMPO

Aldehydes can be easily prepared from the corresponding alcohols in good to excellent yields by oxidation with technical bleach and catalytic amounts of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (1b, 4-hydroxy TEMPO, "HOT"). Whereas the well-known batch process performed on lab scale is not suitable for the technical synthesis especially of activated P-substituted aldehydes, this transformation can be performed continuously in a simple tube reactor. This layout meets all requirements necessary for the process, i.e., turbulent mixing of the biphasic mixture, removal of heat, short contact times, and high output. Thus, a single tube of 3 mm diameter renders about 60 mol of aldehyde per day.