Piperidines, dehydrogenation from pyridines

The synthesis of pyridine from renewable raw materials, i.e., tetrahydrofurfuryl alcohol has also been investigated several times. An intermediate of this process, which has found no industrial application to date, is piperidine, which is dehydrogenated to pyridine. 

The reaction of piperidine conjugated dehydrogenation with hydrogen peroxide [99] opens the way to dehydrogenation of natural compounds, which include piperidine fragments. As shown by experimental data, pyridine yield increases from 45% to 65.2% with hydrogen peroxide concentration from 20% to 25%, respectively, with reaction selectivity above 98%. A further increase of H202 concentration reduces pyridine yield to 59%. It follows from these... 

Dehydrogenation of himbacine with palladium-charcoal at 260° furnished dehydrohimbacine (V). That the transformation involved the saturation of the double bond and the conversion of an A -methyl-piperidine system into a pyridine derivative was apparent from the elemental analysis of the product, its UV-spectrum 265 mp, log 3.65), and the marked change in p/v from 9.3 to 5.4 (50% ethanol). Compound V was also obtained from dihydrohimbacine under the same conditions. 

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