Sandmeyer reaction with 3-aminopyridines

A -oxide which is easily reduced to codeine with sulphur dioxide [303]. The 0-methylation of certain Erythrina alkaloids has been carried out in a similar manner [304]. A -Oxidation has also been used to protect tertiary ring nitrogen atoms in heteroaromatic compounds. Protonation of the ring nitrogen atom in 4- (and 2-) aminopyridines renders their diazonium salts very susceptible to hydrolysis, thus they cannot be converted into cyanides by the Sandmeyer reaction. The corresponding TV-oxides may, however, be used in the normal way and the oxide function removed at a later stage, as in the sequence (63) (64) used by Berson and Cohen in studies on ipecac... 

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