This paper describes a liquid-liquid biphasic flow reaction system that is simple to control. In a liquid-liquid biphasic flow reaction, the slug-flow in the tube reactors generally improves the reaction rate. However, we show that larger tube diameters decreased the reaction rate and the formation of the slug-flow was influenced by the tube diameter, the size of the mixer, and the pump mechanism. These results indicated that technical difficulties with the slug-flow could be an obstacle to scale-up. To resolve this problem, we suggest the use of a Taylor vortex flow reactor to achieve a higher reaction rate than with batch and slugflow systems.
This work presents a case study of process development using continuous flow synthesis. In developing a process for manufacturing drug substances in batch reactors, we unexpectedly obtained a significant amount of a trimerized byproduct on addition of MeMgBr to an aldehyde. Consideration of a plausible generation mechanism for the byproduct indicated that it arose from a reaction between the starting material and the Mg salt of the target product. This led us to try applying continuous flow synthesis to the process to shorten the time during which the starting material coexists with the Mg salt of the target product. This led to drastic suppression of the byproduct under very mild conditions and the establishment of a more robust process than that for batch reactors.
The asymmetric alkynylation of aliphatic and aromatic aldehydes with propiolates was mediated by dialkylzinc and a novel prolinol catalyst without high reagent loading and any additives, such as Ti(Oi-Pr)(4), to give the corresponding γ-hydroxy-α,β-acetylenic esters with high enantiomeric excess of up to 95%.
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