Preparation of Alkynes and Triazoles Using Modular Flow Reactors

Significance

The Seyferth-Gilbert homologation of aldehydes 2 with 1 (the so-called Ohira-Bestmann reagent) was performed in the continuous flow system A, where the convection flow coil and purification columns were equipped affording the corresponding terminal acetylenes 3 in 84-55% yield (>95% purity, 9 examples). The sequential homologation and cycloaddition were carried out in flow system B [CFC + immobilized copper(I) catalyst (A-21˙CuI) + purification columns] to give the triazoles 6a (69%) and 6b (62%) (>95% purity). Flow system C of sequential oxidation, homologation and cycloaddition was built up to give triazole 9 in 55% yields from 1, 7 and 8.