Nitrogen-1.5 NMR spectra were obtuined for a systemu t ic series of. azacvcl[3.3.3]uz ines : 1 ,3,4,6,7,9-hexaaza-,1,3,4,6,7-penttzuza-,1,3,4,6-tetruazu-, 1,3,4,6,8-pentaaza-, und 1,3,4,6,8-pc~iitauzat~~cl[3.3.3]azine, which has a peripheral I ,J-diazine-type nitrogen, are distinct from those of' the rest of' the series.
INTROD C'CTIONHigh-resolution nitrogen-1 S nuclear magnetic resonance spectroscopy [ 11 has provided detailed information on the shielding of nitrogen atoms in a series of cyclic azines and azolopyridines [2]. The effects of interaction between nitrogen atoms and of additional fused aromatic rings in mono-and polyazines were examined systematically. A 1,2-arrangement of nitrogen atoms in a diazine results in a large downfield shift of the I5N resonance rel-"To whom corrcspondencc may be addressed. Dedicated t o Professor Ernest Eliel on the occasion of his seve n t ie t h b i rt hcLiy.ative to that in a monoazine; a l,.l-arrangement results in a smaller downfield shift; and, by contrast, a 1,3-arrangement produces a large upfield shift [2]. Ring systems containing a bridgehead nitrogen atom between two or more six-membered rings have not yet been similarly examined.
RESULTS AND DISCUSSIONWe have now investigated the I5N NMR spectra of a systematic series of azacycl[3.3.3]azines, 1-5. The term cyclazine denotes a fused conjugated ring system held planar by three covalent bonds to an internal nitrogen atom [3,4], as in 1-5, also 6 and 7 . 1,3,4,6,7,9-Hexaazacyc1 [S] to orange (2) [7], lavendar (3) [7-91, blue (5and 7) [7, 10-121, and brown ( 6 ) [6]. The wavelength of the lowest energy transition,
