Two Scalable Syntheses of (S)-2-Methylazetidine

Two orthogonal routes for preparing (S)-2-methylazetidine as a bench stable, crystalline (R)-(−)-CSA salt are presented. One route features the in situ generation and cyclization of a 1,3-bis-triflate to form the azetidine ring, while the second route involves chemoselective reduction of N-Boc azetidine-2-carboxylic acid. Both sequences afford the desired product in good overall yields (61% and 49%) and high enantiomeric excess (>99% ee), avoid column chromatography, and are suitable for the large-scale production of this material.