Continuous Flow Process for the Synthesis of Betahistine via Aza-Michael-Type Reaction in Water

A continuous flow process for the preparation of betahistine with a 90% isolated yield has been reported. 2-Vinylpyridine and saturated methylamine hydrochloride aqueous solution were used as starting materials to achieve excellent results in the silicon carbide flow reactor, which can tolerate the corrosion of chloride ions at high temperature (170 °C) and pressure (25 bar). In the continuous flow process, the product can be obtained in 2.4 min with excellent conversion (>99%) and product selectivity (94%). The throughput can reach 1.06 kg h–1, and the purity of the final product was greater than 99.9% by distillation, which were in accordance with the needs of production. This new process using environmentally friendly water as the solvent is energy-efficient, time- and cost-economic, and offers a 50% reduction in process mass intensity compared to the batch process.