Effets de Substituants en Série Diazolique et Diazinique‐1,3—Etude par Résonance Magnétique Nucléaire du Carbone‐13

Abstract

We have recorded the "C n.m.r. spectra of thiones and thioethers in the 1,3-diazole and 1J-diazine series with various alkyl substituents at the nitrogen atoms. Some analogous oxygen containing heterocycles were also examined. We have shown that in the thiocarbonylated compounds the thiol thione equilibrium is displaced towards the thione form, but that "C n.m.r. gives only qualitative results. In the sulphur containing derivatives the isopropyl group is in a fixed conformational position because of the steric hindrance of the sulphur atom. Substitution by a rerbbutyl group leads to unexpected y values. We ascribe this phenomenon to ring deformation or to variations in the valence angles of the substituted nitrogen atoms.Nous avons enregistrt les spectres de RMN du carbone-13 de thiones et de thioethers, en strie diazolique et diazinique-1,3, diversement substituts sur les atomes d'azote par des groupements alkyles, ainsi que certaines des structures oxygtntes homologues. Toutes les raies de rhsonance ont Btt attributes. Dans le cas des dtrivts thiocarbonylts, nous montrons que l'tquilibre thiol thione est dtplact vers la forme thione, mais que la RMN du carbone-13 ne peut conduire qu'h une tvaluation qualitative de la position de cet tquilibre.L'analyse des effets de substituant montre que, contrairement aux composts oxygknb, Ie groupement isopropyle adopte dans les dtrivts soufrts une conformation privilkgite par suite de l'encombrement sttrique dO B l'atome de soufre. La substitution par un groupement tertiobutyle conduit B des valeurs des effets y inattendus. Nous attribuons ce phgnom5ne B des dgfonnations de cycle ou B des variations des angles valentiels de l'azote porteur du substituant, provoqutes par des interactions sttriques entre le substituant et le cycle correspondant. Nous relions ces modifications B certaines modalitts de la rtactivitt, et B des risultats de spectroscopie photoClectronique.

Resonance Raman spectroscopic and density functional theory investigation of the excited state structural dynamics of 2‐mercapto‐1‐methylimidazole

“…thione form (II) tautomerization reaction (Scheme 1) was previously studied. [24][25][26][27][28][29] It was revealed that thione (II) dominated in the gas phase and in solution phases on the basis of the infrared (IR), [24] Raman [25] and 13 C/ 15 N NMR experimental measurements [26,27] and the theoretical computations. [28,29] The crystal structure of MMI in the triclinic system was determined experimentally, and the results also indicated that thione form (II) in dimer, which was formed through the -N-H. .…”

Diorganotin dihalide complexes of N‐bidentate ligands: crystal structures of diethyldibromo‐ and dibutyldichloro[bis(1‐methyl‐2‐imidazolylthio)methane]tin(IV)

“…The signals for H(4,4') and H(5,5') were assigned on the basis of a NOE experiment. The 13 C NMR spectrum was interpreted by means of a 1 H- 13 C HMQC experiment [33.4,-CH 3 ; 40.0,-CH 2 -; 122.8,-C(5,5'); 129.8,-C(4,4'); 140.1,-C(2,2')]; the C(2,2') signal shows considerable shielding with respect to C(2) in Hmimt (d = 160.2 ppm), shifting close to its position in N-methyl-2-methylthioimidazole (141.7 ppm) 22 as a consequence of thione-thiol evolution.…”

Spectres RMN‐1H Et‐13C De Phenyl‐1‐Propanediamines‐1,2 Derives De L'Ephedrine Et De Leurs Imidazolidines

“…Signalons cependrrnt que mame dans le conformbre TR l'interaction du subetituant tertiobutyle avec l e phknyle est importante at dona une ddformation du cycle eat trbs vraieemblable (23).…”