Treatment of dihydrocodeinone (thio)semicarbazones 1a–d with Ac2O/ZnCl2 afforded (6S)‐spiro[morphinan‐6,2′(3′H)‐[1,3,4]oxadiazolines] 2a, b and (6R)‐spiro[morphinan‐6,2′‐(3′H)‐[1,3,4]thiadiazolines] 3a, b, respectively. The structure of the products including the configuration of the spiro carbons was determined by 1H‐ and 13C‐NMR measurements.
QC 20220915