Oxidation products of 5-ethenyl-4-methyl-3-pyridinecarbonitrile and 2- and 4-methylpyridines

The anion of 5-ethenyl-4-methyl-3-pyridinecarbonitrile 1 undergoes oxidative coupling on treatment with dibenzoyl peroxide affording 1,2-bis-(5′-ethenyl-3′-cyano-4′-pyridyl)-ethane, 2. It is also shown that the anions of 2- and 4-methylpyridine undergo oxidative coupling. In the latter case, however, the coupling reaction is accompanied by addition to the carbonyl group of dibenzoyl peroxide. The addition products have been identified as phenacyl pyridines and dipicolyl phenyl carbinols. The ethenyl side chain of 1 has been hydrated by way of the oxymercuration–reduction process and the secondary alcohol oxidized to a ketone. Both the alcohol and ketone in protected form are potentially useful intermediates in alkaloid synthesis. Keywords: oxidative coupling, 2- and 4-methylpyridines, dibenzoyl peroxide, oxymercuration–reduction.