Practical Synthesis of (S)-Pyrrolidin-2-yl-1H-tetrazole, Incorporating Efficient Protecting Group Removal by Flow-Reactor Hydrogenolysis

A practical, safe, high-yielding and efficient synthesis of (S)-pyrrolidin-2-yl-1H-tetrazole has been developed, which avoids the generation of ammonium azide in the cyclisation step and the use of a 9:1 acetic acid-water mixture as the solvent in the ­hydrogenation. The previously extended hydrogenolysis reaction time (three days) is now reduced to hours through the use of an H-CubeTM (a continuous-flow reactor employing a mixed hydrogen-liquid flow stream)