Download PDF by Author Unknown: Advances in Heterocycling Chemistry. Vol. 44

By Author Unknown

ISBN-10: 0080576311

ISBN-13: 9780080576312

ISBN-10: 0120206447

ISBN-13: 9780120206445

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Extra info for Advances in Heterocycling Chemistry. Vol. 44

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At -65"C, 50-55% of 78 was isolated, with none of the isomeric 4-aminoquinoline (125). At 15"C, 125 was formed in 60-65% yield with only 6-7% of 78. (781 (125) For quinoline derivatives substituted with electron-withdrawing groups, such as 3-nitroquinoline (126), the amide ion is not necessary for a-adduct formation. Liquid ammonia is a sufficiently strong nucleophile to attack the highly electron-deficient heterocycle (Scheme 50). The attack occurred at C-4 and was not dependent on temperature in the range of -45 to +20°C.

For example, 2-phenylpyridine was aminated in DMA with sodium amide to give 6-amino-2-phenylpyridine in 87:/, yield (72KGS1642). The yield was a function of reaction time and temperature; prolonged heating decreased the yield, and the optimum temperature was in the range 130-140°C (73MI1). Preferential attack at the 2-position of 3-substituted pyridines is a general phenomenon in the Chichibabin reaction (64CJC1627). 5: 1 ratio of 2amino-3-methylpyridine to 2-amino-5-methylpyridine (see Section IV,A).

A new catalytic procedure has made it possible to prepare alkyl sodium amides in good yields and in reasonable time. The ADVANCES I N T H E C H I C H I B A B I N R E A C T I O N Sec. B] n-BuNH, + Na catalyst PhCH, 33 d3uNHNa procedure involved refluxing sodium sand and the amine in toluene with a catalyst consisting of a 3- or 4-alkylpyridine, 3,3’-dialkyl-2,2’-bipyridine, or 3or 4-alkylquinoline. The preformed alkyl sodium amide underwent a normal Chichibabin reaction with evolution of hydrogen at lower temperatures than required for sodium amide (83USP4405790).

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Advances in Heterocycling Chemistry. Vol. 44 by Author Unknown


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