Misa V. Jovanovic

15N nuclear magnetic resonance of some pyrazines, 1, 2, 4-triazines and their N-oxides. Correlation and interrelationship of 15N with 13C chemical shifts of π-deficient heterocyclic systems

Abstract The 15 N chemical shifts of a number of pyrazines, 1,2,4-triazines, and their N-oxides are reported. The shielding effects of a substituent ortho to a ring nitrogen on that nitrogen atom depend on the π-deficiency of the heterocyclic ring. These π-deficiency values are related to ortho 13 C chemical shifts in substituted benzenes. A new relationship between 13 C and 15 N chemical shifts of several π-deficient heteroaromatic compounds is described. The N-oxides of pyrazine and 1,2,4-triazine show significant “backdonation” to the groundstate of these ring systems. This contribution becomes more important as the number of nitrogens in the ring increases. The “backdonation” is also reflected by a significant shielding of nitrogen atoms α and/or γ to the N-oxide group.

Nitrogen-oxygen and oxygen-oxygen alkyl group migrations. Synthesis of 1,2,4-triazine hydroxamic acid esters

Abstract Novel 1,2,4-triazine hydroxamic acid esters and alkylated 2, 3-dihydro-1,2,4-triazine N-oxides were prepared by rearrangement and selective alkylations of 3-alkoxy and 3-alkylamino-1,2,4-triazine N-oxides.

Π-Deficiency parameters of heteroaromatic N-oxides

Abstract The 13ϱ parameters, originally developed for the parent heterocyclic ring systems, and representing a quantitative measure of π-deficiency and π-excessiveness, have been extended to their N -oxides, and some of the N -alkylated quaternary salts. These parameters, obtained from 13 C chemical shift data, have been correlated with the ν NO (cm −1 ) frequencies of the N -oxides.

Structure of 2-chloro-10-phenylphenothiazine

ClsH12C1NS, M r= 309.82, monoclinic, P2Jc, a = 19.689 (4), b = 7.240 (1), c = 23.582 (4) A, f l = 1 1 6 . 9 0 ( 1 ) °, V = 2997.8 (9),~, s, Z = 8 , D x = 1.373, D_ = 1.37 g cm -3 (by flotation), 2(Mo Kct) = 0 . 7 1 0 7 , ~ , p = 3.78 cm -~, F ( 0 0 0 ) = 1280, T = 295 K. Final R = 0.036 for 2929 observed reflections. The central ring of the phenothiazine ring system is in a boat conformation. The folding angle between the least-squares planes of the benzo and the chlorobenzo rings is 153.0 (1) and 153.3 (1) ° for the two crystallographically independent molecules in the unit cell. The 10-phenyl substituent is in an equatorial position with respect to the central ring of the phenothiazine ring