Efficient synthesis of 14-hydroxymorphinans from codeine

Abstract
Codeine is converted to 7,8-dihydro-14-hydroxynorcodeinone (noroxycodone) in 6 steps and 52% overall yield or to noroxymorphone in 7 steps and 43% overall yield. N-Demethylation and oxidation of codeine afford N-(ethoxycarbonyl)norcodeinone, which is converted to its dienol acetate derivative and oxidized with singlet oxygen to give N-(ethoxycarbonyl)-14-hydroxynorcodeinone in the key step. Hydrogenation of the latter affords N-(ethoxycarbonyl)noroxycodone, which upon acid hydrolysis yields noroxycodone. O-demethylation of N-(ethoxycarbonyl)noroxycodone with boron tribromide and subsequent acid hydrolysis gives noroxymorphone. The results of the singlet oxygen oxidation of the pyrrolidine dienamine derived from N-(ethoxycarbonyl)norcodeinone are also described.

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