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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 7, Number 3
BKCSDE 7(3)
March 20, 1986 

 
Title
Reduction of N-Arylpyridinium Compounds by Sodium Borohydride and Dithionite: Regioselectivity and Isomerization of Reduction Products
Author
Kwanghee Koh Park*, Duhee Han, Daehyun Shin
Keywords
Abstract
Reduction of N-arylpyridinium compounds by NaBH4 gave mixtures of the corresponding 1,2-dihydropyridine(major) and 1,4-dihydropyridine(minor), whereas similar reduction by Na2S2O4 produced 1,4-dihydropyridines regioselectively. The proportion of 1,4-isomer in the product by NaBH4 reduction appeared to increase with the electron-donating ability of N-aryl groups. When the N-aryl group is p-methylphenyl, p-ethylphenyl or p-methoxyphenyl, the 1,2-dihydropyridines in ethanol-water (4:1) solutions isomerized to the corresponding 1,4-dihydropyridines. N-(p-methylphenyl)-1,2-dihydropyridine and N-(p-ethylphenyl)-1,2-dihydropyridine in solid state also isomerized to the corresponding 1,4-dihydropyridines. The different behaviors of reduction among N-arylpyridiniums and isomerization of the reduction products depending on the substituent in N-aryl group were explained in terms of difference in the electronic effects of the substituents.
Page
201 - 204
Full Text
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