Quinolizidines dehydro

Upon methylation of /) -dehydroindolizidine (55), dialkylated compounds 115 and 116 are formed in addition to C-monomethylated product 114. Compound 115 is accessible also by methylation of 8-methyl-zJ -dehydro-quinolizidine (//i). 

Treatment of perhydro-4-azaazulene (3) with mercuric acetate produces a mixture of dehydro derivatives 31a and 31b, which, with acids, yields homogeneous salts of structure 32 (56JOC344). The enamine 34, which was obtained by the same route from 33, served as a model compound in a study of the synthesis of cephalotaxine (72JOC3691). A reaction with ethyl y-bromo-acetoacetate surprisingly yielded the quinolizidine 36, which was formed by rearrangement of the intermediate annellation product 35 (Scheme 3) Phthalimides 38 were obtained from a Baeyer-Villiger oxidation of 4-azaazulen-3-ones 37 (77JOC1093). 

Dehydrosparteine diperchlorate reacts with butyl hydroperoxide in pyridine to give a 17-hydroxydehydrosparteine salt (LIX) (5S) which rearranges to a mixture of dehydro bases these in turn can be reduced to a mixture of A-formylpiperidylquinolizidine (LX) and piperidyl-quinolizidine (LXI). This is a method for opening the sparteine nucleus. 

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