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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). 2. A Iky lumina t ion of 3- Suhst it uted Pyr idines Butylamination of 3-picoline is shown in Scheme 35. The ratio of the 2amino-5-isomer (89)to the 2-amino-3-isomer (90)was 16: 1.
McGILL A N D ANGELA RAPPA QcoNHz 350 si /&* HzN (67) \ ~~~~z (68 SCHEME 23 1 [Sec. A + (64) Sec. C] ADVANCES IN THE CHICHIBABIN REACTION 27 SCHEME 25 26% yield. It is recorded in the literature that the atmospheric amination of nicotinic acid gave 13% 2,6-diaminopyridine (65) (56RC621). Nicotinamide (66), under pressure, gave 17% 6-aminonicotinamide (67) and 7% 64. Under atmospheric pressure, a 20% yield of 2-aminonicotinamide (68) was obtained (Scheme 23) (44JA1479). B. AMINATION OF 2-SUBSTITUTED PYRIDINES Pressure amination of 2-picoline (I) led to a ring-opening/ring-closure reaction giving m-phenylenediamine (69) as the principal product (Scheme 24).
McGlLL AND ANGELA RAPPA [Sec. A 7 10 1 20 SCHEME 42 Na 00 9) SCHEME 43 Sec. Some other examples are illustrated in Scheme 42 (78RCR1042). Several explanations have been offered for the preference of amination in the 2-position. If aromatization of the intermediate is the rate-determining step, this behavior may be due to the fact that a-adduct 108 loses a hydride ion more readily than 109 (Scheme 43). This argument is weakened by the lack of a kinetic isotope effect in the Chichibabin amination (65CJC725).