Efficient synthesis of 14-hydroxymorphinans from codeine

Codeine is converted to 7,8-dihydro-14-hydroxynorcodeinone (noroxycodone) in six steps and 52% overall yield of the noroxymorphone in seven 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. Alternatively, 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.