Thebaine-maleic anhydride

Thebaine-maleic anhydride 27Od. xylene prisms. . 1-2... 

Evidence for the conjugated double-bond system in thebaine is provided by the ready condensation of the alkaloid with maleic anhydride and benzoquinone [90-91]. 

Thebaine behaves as an active conjugated diene in undergoing addition of maleic anhydride [42-43], benzoquinone [42-43], 1 4-naphthoquinone [42], and acrolein [102], The adduct with benzoquinone undergoes deep-seated rearrangement on heating for three hours with concentrated hydrochloric acid to give flavothebaone [43-44] (see Chap. XXI). 

Dihydrothebaine- was originally given the structure [n], which was in accord with most of its chemical properties [3-4] except its failure to condense with benzoquinone or maleic anhydride and its failure to yield a derivative of 14-bromothebainone [iii] on treatment with bromine [5], However, the production of a conjugated diene as final product in a sodium-alcohol or sodium-ammonia reduction is contrary to general experience and examination of the infra-red and ultra-violet absorption spectra of dihydrothebaine-, thebaine, /3-dihydrothebaine, several 1 4-dihydroanisole derivatives, and 1-alkoxy-l 3-dienes led to modification of the structure of dihydrothebaine- to [iv] [6], which structure is more in accord with its properties than is [n], and in particular explains why the hydrogenation of this base proceeds with absorption of only one mole of hydrogen (see Chap. XIV). 

The diethyl ester derived from the Diels-Alder adduct of thebaine with maleic anhydride has been converted into the lactone (124), by methylmagnesium iodide, and into a diol by lithium aluminium hydride. The diol has been dehydrated to the diene (125), which undergoes Diels-Alder addition of N-phenylmaleimide to give the adduct (126). °... 

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