Polynuclear Compounds Containing a Bridgehead Nitrogen

1 Indolizine (pyrrocoline). Indolizine109,110 and its 2-methyl (eq. 12.57), 3-methyl, and 2,3-dimethyl derivatives110 were hydrogenated to the corresponding indolizidines (octahydropyrrocolines) over platinum oxide in acetic acid. Indolizine was also hydrogenated to indolizidine over prereduced platinum oxide in ethanol and a drop of hydrochloric acid.111 

3-Acetyl-2-phenyl- (eq. 12.60) and 3-ethyl-2-phenylindolizines were hydrogenated to the corresponding 5,6,7,8-tetrahydro derivatives over Raney Ni at room temperature.113 Water and Margolis hydrogenated various 1-substituted 2-phenylindolizines, which were not hydrogenated with palladium or platinum catalysts, over Raney Ni to the 5,6,7,8-tetrahydro derivatives in ethanol at room temperature and 0.41 MPa H2.115 

2 Quinolizine (Pyridocoline). Quinolizine (32) does not appear to have ever been prepared in a pure state. However, quinolizinium iodide (33)117 and dehydroquinolizinium iodide (34)117 118 were readily hydrogenated over Adams platinum oxide in ethanol to yield quinolizidine hydroiodide with the uptake of 4 and 5 equiv of hydrogen, respectively (eq. 12.61). Similarly, 2-methyldehydro-quinolizinium iodide rapidly absorbed 5 mol of hydrogen over platinum oxide in methanol to give octahydro-2-methylquinolizine.119 

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