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Extra resources for Advances in Heterocycling Chemistry. Vol. 44
Support for the existence of dianionic a-adducts has been presented by Novikov et al. (76CHE210) and Kessar et al. (73IJC825). The function of the partial pressure of ammonia is to inhibit the formation of the dianionic a-adducts. Once the dianionic a-adducts are formed, they become good hydride donors and aromatize to products 58 and 59. As the concentration of products slowly becomes significant, the principal amination pathway is taken over by autocatalysis by means of a six-membered transition complex, as described in Section II,A,2 and as shown for the 2,5-isomer in Scheme 20.
In this manner, the reaction was cleaner and the yields were better than under the conditions of Vajda and Kovacs, in which the heterocycle and alkylamine were required to react simultaneously with alkali metals, thus yielding appreciable amounts of dimers and tarry materials. 1. Preparation of Alkyl Sodium Amides Primary alkylamines are extremely difficult to metallate with sodium amide or sodium hydride and generally d o not react with metallic sodium. It is known that the amines react quickly and smoothly under mild conditions with potassium hydride, but from a practical viewpoint, metallation with sodium would be preferred (73JA982).
5 . Intramolecular Alkylaminations A variation in the use of alkylamines as aminating agents is the intramolecular nucleophilic cyclization of appropriate 3-aminoalkylpyridines. M c G I L L AND ANGELA RAPPA [Sec. In like manner, 3-(3-pyridyl)propylamine (95) gave 1,2,3,4-tetrahydro-1,8-naphthyridine(96) in 30% yield and 4-(3pyridy1)butylamine (97)afforded 6,7,8,9-tetrahydro-5H-pyrido[2,3-b]azepine (98) in 87% yield (Scheme 38). The latter compound was also prepared using sodium hydride, potassium hydride, and sodium amide, giving lower yields (73JHC39).