Chemo‑, Regio‑, and Stereoselective Synthesis of Polysusbtituted Oxazolo[3,2‑d][1,4]oxazepin-5(3H)ones via a Domino oxa-Michael/aza-Michael/Williamson Cycloetherification Sequence

The access to new oxazolo­[3,2-d]­[1,4]­oxazepin-5­(3H)-ones starting from α-bromoamido alcohols and Michael acceptors under mild conditions is presented. This domino process proved to be chemo-, regio-, and stereoselective and allows the formation of a large diversity of highly functional 7-membered rings in good yields up to 95%. The complete shift of the regioselectivity of the intermediate enolate from a C–C to a C–O bond formation, contrary to the already known alkylations of such ambident nucleophiles, is mostly triggered by steric effects. The last step of the sequence was modeled by DFT giving some important insights for this C–C vs C–O bond shift.