Annulation Cascade of Sulfamate-Derived Cyclic Imines with Glycine Aldimino Esters: Synthesis of 1,3-Benzoxazepine Scaffolds
Mallu Kesava Reddy, Vinod Bhajammanavar and Mahiuddin Baidya*
*Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, Tamil Nadu, India, Email: mbaidyaiitm.ac.in
M. K. Reddy, V. Bhajammanavar, M. Baidya, Org. Lett., 2021, 23, 3868-3872.
DOI: 10.1021/acs.orglett.1c01001 (free Supporting Information)
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Benzo-fused sulfamate-derived imines readily react with glycine aldimino esters in the presence of an amine base to furnish 1,3-benzoxazepine frameworks in good yields.
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General procedure for the synthesis of 1,3-Benzoxazepines:
In an oven dried reaction tube equipped with a magnetic stir bar, sulfamate-derived imine (0.2 mmol, 1.0 equiv), glycine aldimino ester 2 (0.22 mmol, 1.1 equiv), and quinidine (20 mol %) were taken. Then, dry DCM (2 mL), followed by dry Et3N (2.0 equiv) were added and the reaction mixture was stirred at room temperature. After 36 h (progress of the reaction was monitored by thin layer chromatography) reaction mixture was concentrated under reduced pressure and the crude product was purified by silica gel column chromatography (1→5% EtOAc : hexane) to give pure product.