(5aS,8R,9aR)-5,5,8-Trimethyloctahydrobenzo[f][1,4]oxazepin-3(2H)-one

The monoterpene-derived 1,4-oxazepan-3-one, (5aS,8R,9aR)-5,5,8-trimethyloctahydrobenzo[f][1,4]oxazepin-3(2H)-one, was synthesized from the corresponding (−)-isopulegol-based chloroacetamide by intramolecular cyclization in acetonitrile. The product was isolated in 70% yield as colorless crystals. Its structure was established by one- and two-dimensional NMR spectroscopy and high-resolution mass spectrometry and was confirmed by single-crystal X-ray diffraction analysis. The transformation provides concise access to a fused bicyclic 1,4-oxazepan-3-one bearing a stereochemically defined para-menthane scaffold.