Esters and Amides in the Pyridine Series

Hydrogenation of these compounds does not pose much of a problem. Nickel under elevated pressure and temperature has been used with success (3, 60). Platinum catalyzed reductions in the presence of an 

Some esters may undergo cyclization if the side chain is long enough and it is in 2-position. The following is an example of such a reaction (62). 

When the same pyridyl compound was reduced under low pressure conditions with platinum oxide in acetic acid, the intermediate piperidyl ester was obtained (63). It was, however, converted to the same ring closed compound on distillation. 

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