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The mechanism for borohydride reduction of pyridinium salts was suggested as involvement of initial irreversible nucleophilic attack by hydride ion at the 2 and/or 4 positions of pyridine nucleus to generate the corresponding dihydropyridines.It was also suggested that addition of a hydride ion at the 2 position is kinetically favored because the site is closest to the positive nitrogen and therefore, most favored by coulombic attraction.

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