1. This investigation was supported in part by research grant C6516 and research career development award K3-CA-22, 151 from the National Cancer Institute, National Institutes of Health, U.S. Public Health Service.
2. R. Barchet and K. W. Merz, Tetrahedron Letters, 2239 (1964). The authors mention the reaction of 2,3-diaminopyridine with ethyl benzoylacetate and ethyl 3-nicotinoylacetate and, avoiding the question of alternate possibilities of cyclization, arbitrarily assign to the products structure IIa, in which the 2-methyl group is replaced by phenyl and 3-pyridyl, respectively.
3. The identity of this material, as established by alternate synthesis, and the nature of its origin in the reaction mixture will be discussed in a subsequent report.
4. N.m.r. spectra were obtained by means of a Varian A-60 spectrometer, equipped with a variable temperature controller, with tetramethylsilane as the internal reference; the solvent was anhydrous deuteriopyridine, stored over Linde 4A molecular sieves. The time averaged spectrum, where indicated, was obtained by means of a Japan Electron Optics Laboratory Company JRA-1 Spectrum Accumulator.
5. Diazotation of IV in dilute acid afforded an unstable diazonium intermediate which readily eliminated nitrogen gas and which failed to couple with α-naphthol. This behavior is consistent with that of 2-aminopyridine and its derivatives, which, on diazotization, readily give α-pyridones, whereas 3-aminopyridines behave like aniline and afford diazonium intermediates which are stabilized by aromatic resonance and which couple with α-naphthol to give deep red colored arylazo adducts;;