0-Codeimethine reduction

Hydrogenation of -codeine in dilute acetic acid [65] or electrolytic reduction [55] affords dihydro- -codeine-B [xxv] obtained together with dihydro-i/r-codeine-C [xxvm] by reduction with sodium and alcohol [66]. These two compounds suffer Hofmann degradation in the usual way giving, respectively, dihydro-e-codeimethine-B [xxvi] [55, 60] and dihydro-e-codoimothine-C [xxix] [00], the latter also being... 

Though the reduction of allo-i/ -codeine shows certain differences from that of i/r-codeine (see Chap. IV), reduced -codeimethines corresponding to [xxiv], [xxn], [xxvn], and [xxxi] have been prepared [55, 63, 68]. 

Desoxycodeine-E [xxx] pan be prepared by the lithium aluminium hydride reduction of codeine [n] p-toluenesulphonyl ester [17-18], Its structure is shown to be [xxx] by hydrogenation of the base to dihydrodesoxycodeine-D [xiii], degradation of the methiodide to desoxy-a-codeimethine [xxix], and isomerization of the latter to desoxy-/3-codeimethine [xxvin], production of cyanonordesoxy codeine-E [xxxi] by the action of cyanogen bromide on the base, and by the facts that desoxycodeine-E is neither a phenol nor an enol ether [17]. Desoxycodeine-E can be demethylated to desoxymorphine-E [62]. 

Hofmann degradation of dihydrocodeinone methiodide affords dihydrocodeinone methine [Lvm] [55] which can also be prepared by the hydrolysis of dihydrothebaine methine [lix] [78], and by the catalytic rearrangement of a-codeimethine [lx] by boiling with Raney nickel in alcohol [79]. It can be reduced to the dihydromethine, available by the hydrolysis of dihydrothebaine dihydromethine and by the chromic acid oxidation of a-tetrahydrocodeimethine [lxi] [78]. The cyclic ether link of the methine [lviii] and dihydromethine can be opened by aluminium amalgam reduction in wet ether, giving dihydrothebainone methine [lxii] and dihydromethine respectively [78]. 

Hydrogenation of thebainone-B methine proceeds rapidly, with the absorption of two moles of hydrogen and production of /S-dihydro-thebainone dihydromethine [xvin] [20-21] this is the only case in morphine series in which reduction of an 8 14 double bond results in configuration of the asymmetric carbon atom C-14 in the abnormal manner. The possibility of thebainone-B methine having the isomeric structure [xix] is ruled out by the ultra-violet absorption spectrum, which is closely similar to that of /S-codeimethine [xx] and dissimilar from that of a-codeimethine [xxi] (Kg. 9) [21]. 

Codeine dihydromethine [xn] has now been prepared by the sodium-ammonia reduction of codeine methiodide, together with dihydrodesoxy-codeine-C dihydromethine [xiii]. Both [xii] and [xni] result from the sodium and liquid ammonia reduction of a-codeimethine [xiv] [2] (cf. p. 106). The sodium and liquid ammonia reduction of dihydrocodeine methiodide affords a-tetrahydrocodeimethine, and the reduction of /3-codeimethine [xv] yields neopine dihydromethine [xvi]. When the methiodide of the latter is heated with sodium cyciohexyloxide in cyciohexanol a mixture of methyl-morphenol [xvn] and (-f-)-6-hydroxy-3-methoxy-5 6 7 8 9 10-hexahydro-phenanthrylene-4 5-oxide [xviii] is obtained. The latter structure is assigned to the product on account of the close resemblance of its ultra-violet absorption spectrum to that of a-codeimethine. This represents a new type of degradation with hydrolytic scission of the side-chain [2]. Metathebainone methine has also been degraded in this way [2]. 

Dihydbodesoxycodeine-C dihydromethine [xrn] has been prepared by the sodium and liquid ammonia reduction of a-codeimethine [xiv] [2]. 

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