✍ Scribed by Arnold Brossi; Fu-Lian Hsu; Kenner C. Rice; Maria D. Rozwadowska; Helmut Schmidhammer; Charles D. Hufford; Chian Chian Chiang; Isabella L. Karle
No coin nor oath required. For personal study only.
Bromination of (−)‐4‐hydroxy‐N‐methylmorphinan‐6‐one (3), prepared from natural morphine, with 1 mol of bromine in acetic acid, afforded the 1‐bromo ketone 5. The structure of 5 was assigned by ^13^C‐NMR.spectroscopy, and confirmed by X‐ray diffraction analysis of its hydrobromide salt. It is suggested that monobromination of synthetic (±)‐2,4‐dihydroxy‐N‐formylmorphinan‐6‐one (7) takes in principle a similar course, although the ^13^C‐NMR.spectrum of the primary reaction product 9 could not be measured because of insolubility in commonly used solvents. Monobromination of (−)‐4‐acetoxy‐N‐formylmorphinan‐6‐one (12) of the natural series, and of (±)‐2,4‐diacetoxy‐N‐formylmorphinan‐6‐one (8) of the synthetic series, followed by treatment of the monobrominated ketones with potassium carbonate in methanol resulted in closure of the O‐bridge, and afforded after acid hydrolysis, the corresponding 4,5‐epoxy‐morphinan‐6‐ones (−)‐16 and (±)‐17 respectively. This variation of the ring closure reaction represents a novel and convenient method to convert 4‐hydroxymorphinan‐6‐ones into their corresponding 4,5‐epoxymorphinan‐6‐ones, without involving aromatic bromination and with only 1 mol of bromine.
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