Microflow High-p,T Intensification of Vitamin D₃ Synthesis Using an Ultraviolet Lamp

Herewith a new process concept for synthesis is presented which combines both UV-photoirradiation and high-p,T intensification (photo-high-p,T) in continuous flow. The application of this procedure to Vitamin D₃ synthesis promotes thermal shifting of the equilibrium from the reaction intermediate to the product. This is enabled by microreactors which allow operation under harsh conditions such as the high temperature used here. This provides, to our best knowledge, a new kind of process combination (novel process window). As a result, in less than 1 min, 42% conversion of 7-dehydrocholesterol can be achieved giving a 17% yield and 40% selectivity of Vitamin D₃. This approach enhances productivity by up to 2 orders of magnitude compared with the current capillary based vitamin D₃ synthesis, because, under the microflow conditions, photochemistry can be performed at fairly high concentration and up to 20 times faster.