Carbon-13 NMR spectroscopy of sulfonium ylides

C-13 NMR data for a series of stabilized and unstabilized ylides indicate flattening at the ylidic carbon with respect to the parent salts. For unstabilized ylides association between the carbanionic center and the lithium cation cannot be neglected.     

Structure and13C NMR spectra of alkaloid-like compounds,products of intramolecular cyclization of phthalimidoketo-stabilized sulfonium ylides

The structures of 14 products of intramolecular cyclization of aminoketo-stabilized sulfonium ylides, analog of natural alkaloids, were determined by¹³C NMR spectroscopy.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2298–2302, October, 1991.     

13C NMR spectra and electronic structure of alkenylalanes

The parameters of¹³C NMR spectra of linear and cyclic alkenylalanes synthesized from mono- and disubstituted acetylene and the simplest alkylalanes have been obtained. A strong paramagnetic effect of the aluminum atom on shielding of α- and β-carbon atoms at the double bond has been observed for the dimeric form of organoaluminum compounds (OAC) in inert solvents, unlike that for the monomeric form solvated in electron-donor solvents (Et₂O, THF, and Et₃N). The results were interpreted in terms of the model of the electron density redistribution on going from the dimeric structure of OAC to the monomeric one. The PM3 method describes most adequately (as compared to MNDO and AM1) the equilibrium geometry of cyclic dimers of OAC.     

Spectra and structure of sulfonium C-mononitro ylides

Conclusions Based on the data of the vibrational spectra and quantum-chemical calculation, in its electronic structure the nitro group in sulfonium C-nitro ylides is closer to the nitro groups in nonionized nitro compounds than in their salts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1403–1406, June, 1981.     

13C NMR spectra and the structure of dithizone

The structural characteristics of dithizone in the solid state and in solution were studied by a high-resolution¹³C NMR method. A highly symmetrical structure of dithizone was established in the crystalline state, and it was suggested that it exhibits dual behavior in complexation reactions with metal ions.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 117975 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 113–117, January, 1992.     

Spectra and structure of sulfonium C-dinitro ylides

Conclusions Based on the data of the vibrational spectra of sulfonium C-dinitro ylides and the quantum-chemical calculation of the electronic structure of the molecule the nitro groups of dinitro ylides in their electronic structure differ substantially from the nitro groups of both the gem-dinitroalkanes and their salts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1407–1409, June, 1981.     

13C NMR spectra and structure of some coumarin derivatives

The results are given of a study of the¹³C NMR spectra of (?)-3(R)-decursinol, obtusifol, bergapten, isoimperatorin, and oxypeucedanin and its hydrate. The possibility has been shown of using the principle of additive contributions in the assignment of the signals of the carbon atoms in the compounds under investigation.     

13C NMR spectra of alkenylsilanes

Conclusions The¹³C NMR spectra of 12 alkenylsilanes were measured and the values of the increments of the chemical shifts of the (CH₃)₃Si group were determined for some allylsilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 938–939, April, 1978.     

13C NMR spectra and structure of bungeidiol and its transformation products

The results are given of a study of the¹³C NMR spectra of the new terpenoid coumarin bungeidiol (I) and of the products of its transformation (II) and (III) and some model compounds (IV–VII). On the basis of the results obtained from these¹³C NMR spectra and with the use of additive contributions depending on the nature and positions of various substituents (hydroxy and methoxy groups) in the aromatic ring, the structure (I) has been confirmed and a complete assignment of the signals of all the carbon atoms both in the coumarin ring and in the aliphatic part of the molecule of (I) has been made.     

13C NMR spectra of S-methylquinolines

The ¹³C chemical shifts and the increments () of the SCH₃ group in the NMR spectra of S-methylquinolines were measured. It is shown that the chemical shifts of S-methylquinolines correlate satisfactorily with the total charges on the carbon atoms calculated within the CNDO/2 approximation. The coupling of the SCH₃ group with the quinoline ring was examined on the basis of the values.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1665–1671, December, 1979.The authors thank É. É. Liepin' for his discussion of the results.Original article submitted October 1, 1978.     

Carbon-carbon bond-forming reaction of cyclic sulfonium ylides stabilized by a carbonyl group

Rhodium(II)-catalyzed decomposition of diazoketones 1 and 5 bearing a cyclic dithioacetal, in the presence of aldehyde and ClTi(Oi-Pr)(3), afforded both or one of the C=C-bonded products, i.e., ring-enlarged enone 2 and ring-transformed thiophenone 3, that were formed between aldehyde and intermediate bicyclosulfonium ylide. The stereochemistry of the exocyclic C=C bond in the products was exclusively Z. The sulfonium atom that transiently composed the ylide was incorporated into products, but no oxirane was formed.     

Synthesis of some sulfonium salts and ylides containing the isoxazole nucleus

Some dimethylisoxazolylmethylsulfonium salts and the corresponding ylides were synthetized and their chemical behaviour studied. Dimethylsullonium-5-isoxazolyl methylides (XIa,b) give 5-isoxazolyloxiranes (XIIa,d) and XIII when allowed to react with carbonyl compounds. Ring opening products from these oxiranes are also reported.     

1H and13C NMR spectra and structure of 2,3,4-trisubstituted sulfolanes

Conclusions The¹H and¹³C NMR spectra were studied for 2,3,4-trisubstituted sulfolanes and the isomerism of these compounds was determined, The use of chemical shift information is more convenient to determine the isomerism of polysubstituted cyclic compounds by PMR spectroscopy, while use of the direct carbon-proton coupling constants is more convenient for this problem when employing¹³C NMR spectroscopy.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2498–2501, November 1984.     

The 13C NMR spectra of homoisoflavonoids

The study of a set of 3-benzylidene-4-chromanones, 3-benzyl-4-chromanones, 3-benzyl-3-hydroxy-4-chromanones and 3-benzylchromones (homoisoflavonoids) by ¹³C NMR spectroscopy shows the influence of the structure of these molecules on the chemical shifts of the more characteristic carbon atoms at positions 2, 3 and 4.