G. A. Kalabin

Carbon-carbon coupling constants - a new guide in the stereochemistry of oximes

A positive contribution of more than 7 Hz to the direct 13C-13C spin-spin coupling constants induced by the proximity of the nitrogen lone pair in syn-orientation to the coupled nuclei allows an unambiguous configuration assignment of diverse oximes.

One-pot synthesis of divinyloxy propenes by reaction of glycerol with accetylene

Abstract The synthesis of 1,2-divinyloxy-1-propene (I) and 1,2-divinyloxy-2-propene (II), via the reaction of glycerol with acetylene in the potassium hydroxide-hexamethylphosphoramide (HMPA) system in reported.

An example of a novel synthetic approach to alkenylpyrroles

Abstract The synthesis of 2-methyl-3-(2-propenyl)pyrrole ( 2 ) and E- and Z-2-methyl-3-(1-propenyl)pyrroles ( 3 ) via the reaction of 3-butenyl methyl ketoxime ( 1 ) with acetylene in the KOH-DMSO system is reported.

Thiylation of diallyl sulfide by hydrogen sulfide in the alkali metal hydroxide-DMSO system

Preparative methods have been developed for the synthesis of 3,7-dimethyl-1,2,5-trithiacycloheptane and 4-thia-1-heptene-6-thiol from diallyl sulfide and hydrogen sulfide in a system containing an alkali metal hydroxide and DMSO.

Pyrroles from ketoximes and acetylene. No. 36. 4,4,6,6-Tetramethyl-4,5,6,7-tetrahydro-5-azaindole, its nitroxyl and vinyl derivatives, and spin-labelled copolymer

An oxime containing a nitroxyl functional group site, 2,2,6,6-tetramethyl-1-nitroxyl-4-hydroxyiminopiperidine, has been shown for the first time to engage in productive pyrrole synthesis via reaction with acetylene in KOH-DMSO. The behavior of 2,2,6,6-tetramethyl-4-piperidone oxime and its 1-hydroxy derivative in this reaction has also been investigated. The corresponding 5-azaindole and its 5-nitroxyl and 1-vinyl derivatives have been synthesized in this manner. 1-Hydroxy-4-piperidone oxime reacts at 50–60‡C under the general reaction conditions undergoing oxidative conversion to 5-azaindole, while at 105‡C in the presence of excess acetylene reduction of the hydroxy group also takes place. The formation of a pyrrole ring does not involve radical chains, although vinylation of the resulting pyrroles apparently involves one-electron transfer. 1-Vinyl-4,4,6,6-tetramethyl-4,5,6,7-tetrahydro-5-azaindole has been used for the preparation of a spin-labelled polyvinyl alcohol copolymer.

Effect of the nitrogen unshared electron pair on the direct13C-13C spin-spin coupling constant of a neighboring bond in oximes

The authors have previously established that the direct /sup 13/C-/sup 13/C coupling constants are stereospecific relative to the orientation of unshared electron pairs (UEP) of nitrogen and oxygen atoms. Here they show that the nitrogen UEP produces a positive contribution to the direct /sup 13/C-/sup 13/C coupling constant of an adjacent syn-periplanar carbon-carbon bond and not to a negative contribution of the corresponding constant of the anti-periplanar bond. Thus, the observed effect is not a consequence of the interaction of the heteroatom UEP with the anti-bonding orbital of the adjacent anti-periplanar bond (n/sub o-o/* interaction) as in the case of anomeric and related effects.

Pyrroles from ketoximes and acetylene. 13. Study of some substituted pyrroles by13C NMR spectroscopy and calculations with the CNDO/2 approximation

The13C chemical shifts of six substituted pyrroles are compared with the calculated charges of the corresponding carbon atoms. The correlation is linear only when the charges of the immediate environment are taken into account. The sensitivity of the13C chemical shift to a change in the charge is increased substantially in 1-vinylpyrroles as compared with their NH analogs. The energetically favorable conformations of the 2-methyl-1-vinyl molecule were established by the CNDO/2 method.

Pyrroles from ketoximes and acetylene. 11. Conformation of 1-vinylpyrroles from1H NMR data

A number of 1-vinylpyrroles were studied by PMR spectroscopy. Bulky substituents in the α position of the pyrrole ring give rise to deshielding of hb and a decrease in2J(HA,HB) and6J(H3,HB). The results were interpreted as a decrease in the p, π conjugation in the N-vinyl group due to distortion of the coplanarity. The dihedral angle (ϕ) between the planes of the pyrrole ring and the double bond was estimated (with an accuracy of ±5 °).

Study of conjugation effects by means of NMR spectroscopy. 13. NMR spectra of divinyl chalcogenides

Conclusions1.Parameters of the1H,13C,17O,77Se, and125Te NMR spectra have been obtained for divinyl chalcogenides. Estimates have been made of the effective group electronegativities and the resonance constants of the XCH=CH2 and XCH2CH3 groups, with X=O, S, SO, SO2, Se, and Te.2.In the interaction with the unsaturated fragment, for the Group VI-A heteroatoms, theπ-donor effect predominates, decreasing in the series O>S>Se>Te;π-acceptor interaction is manifested in the series of sulfoxides and sulfones.

NMR-spectroscopic study of conjugation effects. 9.13C NMR spectra of alkyl vinyl sulfoxides and sulfones

ConclusionsPolarization and steric effects of the alkylhetero groups have the main influence on the C1,2 chemical shifts of the vinyl fragment in alkyl vinyl sulfoxides and sulfones. In sulfones, an appreciable role can be played by a π-acceptor interaction between the sulfur atom and the double bond.