Studies on the chemistry of morphine and Amaryllidaceae alkaloids

Nitrosation of thebaine using nitrosyl chloride, pentyl nitrite and nitrosyl sulphuric acid was investigated. Substitution was shown to take place at C-7 of thebaine. The major product of nitrosation was the dimethyl or diethyl ketal of 7-hydroxyiminoneopinone depending on whether methanol or ethanol was used as the solvent. The transient 7-nitroso derivatives which tautomerized to these oximes were also found to attack the diene system of another molecule of thebaine, especially when nitrosyl sulphuric acid was used as a nitrosating agent, to give adducts the structures of which were established. 1,4-cycloadditions of nitrosoarenes to thebaine were investigated to establish the orientation of the cycloaddition and the chemistry of the products studied. The oxime obtained from nitrosation was converted to the parent ketone by further nitrosation with pentyl nitrite and acetic acid. [Continues.]