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Abstraet: Differenlly SubSlilUled 2-aminopyridines 1u:Jvebun prepared in rwo sleps from pyridinium-N-(2-pyridyl)aminide. by reaelion wilh lhe co"esponding eleetrophiles and reduclion O/Ihe N-N bond.As the body of knowledge about the reactivity of azinium N-ylides expands, the interest in such compounds as building blocks for the synthesis of heterocyclic derivatives continuously increases.1 Some of our work in the field has been concemed with the synthesis of heteroaryl-stabilized cycloiminium ylides as a way of producing highly stable dipoles, with heterocyclic moieties of unusual reactivity.2In this paper we wish to repon our first results with the pyridinium-N-(2-pyridyl)aminide 1 in which there is a negatively charged 2-aminopyridine fragmento The precursor pyridinium bromide was prepared by using the method of Beyer,3 and convened into the stable aminide 1 by treatment with K2C0y'acetone. The structure of 1 in solution showed an intramolecular hydrogen bond as indicated, which has been described for related compounds.4 HRY8Because of its structure in solution, reaction of 1 with alkyl halides produced regioselective alkylation on the exocyclic nitrogen (compounds 2, Fig. 2), with no signs of alkylation on the NI of the 2-pyridyl ring.Reaction of 1 with electrophiles producing C-substitution was obtained under very mild conditions. Thus, iodination with equirnolar amounts of iodine at room temp., yielded the monoiodo salt 3 (61%), while when iodination was made in the presence of base (K2C03)' the initially formed 3 was deprotonated and attacked again, being the diiodo betaine 4 isolated (22%). On treatment with bromine, the process was out of control, being obtained then a rnixture of 5-bromo and 3,5-dibromo salts (1:4), even when working at OOC. Again, in the presence of base, only the 3,5-dibromo betaine 5 was obtained (75%). 2019

Azinium-N-(2'-azinyl)aminides: Synthesis, Structure and Reactivity. -The structures of the title compounds (V) and (XV) are confirmed by NMR spectroscopic data (X-ray analysis of (Va): space group P21/n with Z = 4). -(CARCELLER, R.; GARCIA-NAVIO, J. L.; IZQUIERDO, M. L.; ALVAREZ-BUILLA, J.; FAJARDO, M.; GOMEZ-SAL, P.; GAGO, F.; Tetrahedron 50 (1994) 17, 4995-5012; Dep. Quim. Org., Univ. Alcala, E-28871 Alcala de Henares, Spain; EN)

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