Synthesis of functionalized fluorine-containing trimethylsilylcarbodiimides

New functionalized polyfluorinated carbodiimides R_FN=C=NSiMe₃ were prepared by the reactions of bis(trimethylsilyl)carbodiimide with electrophilic reagents. The structures of the resulting compounds were confirmed by¹H,¹³C,²⁹Si,¹⁴N,¹⁵N, and¹⁷O NMR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 775–777, April, 1999.     

The investigation of the electronic effects of polyfluoro-aryl group by means of nmr spectroscopy

The relationship between NMR ¹⁵N, ¹⁷O, ³¹P, ⁷⁷Se, ¹³C spectral parameters and electronic structure of number of polyfluoroaromatic compounds has been discussed. The increase of the nuclei shielding has been found in all classes of investigated polyfluorinated compounds in respect to the corresponding hydrocarbon analogues. That effect has been discussed in terms of decrease of the conjugation between the unshared electron density of heteroatoms and the π-system of polyfluorinated benzene ring. The conductivity of substituent electronic effects on the π-system of the polyfluoroaryl group by the heteroatom has been estimated from NMR ¹³C data. The sensitivity of nuclei shielding towards interamolecular electronic effects has been noticed to increase from oxygen to selenium and the analysis of the influence of the intramolecular electronic effects on the ¹⁷O and ⁷⁷Se shifts has been given. The influence of the substituents either in pentafluorophenyl ring or adjacent to heteroatom have been shown to correspond those in the hydrocarbon analogues.The conclusion about the influence of polyfluoroaryl group on the character of bonds between different atoms in functional group has been made from the NMR ¹⁷O and ¹⁵N data for aromatic nitro-derivatives. Polyfluorophenyl group in respect to phenyl one deshields the oxygen atom and shields the nitrogen atom. The same effect of pentafluorophenyl group has been observed by other spectral methods.The different screening of ¹⁷O, ¹⁵N, ³¹P and ⁷⁷Se nuclei due to the action of substituents adjacent to the element and variation of the coordination number of heteroatom have been used to the solvation of a number of problems in chemistry of the heteroanalogues of carbenium ions and the detail investigation of the mechanism of electrophylic substitution in the field of polyfluoroaromatic compounds.     

13C-NMR studies of polyfluorinated hydrocarbons,carboxylic acid derivatives,alcohols and ethers

δ¹³C values and coupling constants (¹J(¹³C¹H), ¹J(¹³C¹³C), ⁿJ(¹⁹F¹³C) are reported for 19 polyfluorinated organic compounds. It is shown that the shielding of carbon depends upon the number of fluorine atoms in α -position. If the R_F-group is linked to a π -system hyperconjugative $\text{and}$ η-π interaction accounts for the δ¹³C data. The values ¹J(¹³C¹H) and ¹J(¹³C¹³C) are in qualitative agreement with changes of the s-character of the respective bonds.     

Oxygen-17 and Carbon-13 Nuclear Magnetic Resonance. Chemical shifts of unsaturated carbonyl compounds and acyl derivatives

The ¹⁷O and ¹³C chemical shifts (δ) of 14 α,β-unsaturated aldehydes and ketones and 33 acyl derivatives RXC = O (X = Cl, OH, OMe, OEt, NH₂ and R = H or alkyl) have been measured. In the unsaturated carbonyl series, a correlation exists between δ ¹⁷O and the π electron density at the β-carbon atom. From this correlation, an δ ¹⁷O of 530 ppm was extrapolated for the loss of one electron at the oxygen atom. In the acyl series, the δr ¹⁷O were also sensitive to changes in the polarity of the carbon-oxygen bond. A partial correlation between ¹⁷O-NMR. chemical shifts and the nuclear quadrupole coupling constants exists for aldehydes, ketones, esters and amides but not for acyl chlorides.     

Carboncarbon bond formation by radical addition-fragmentation reactions of O-tert-alkyl enols and O-cyclopropylcarbinyl enols

Terminal alkenes of the type H₂CC(OR¹)X, in which R¹ is a tertiary alkyl or a 1-cyclopropylethyl group and X=Ph, OSiMe₂Bu^t, OEt or H, undergo radical-chain reactions with organic halides R²Hal to give carbonyl compounds R²CH₂C(O)X.     

Torsion angle relationship of the 17O NMR chemical shift in α,β‐unsaturated carbonyl compounds

The torsion angle effect on the isotropic shielding of ¹⁷O nucleus in α,β‐unsaturated carbonyl groups is studied by means of density functional theory (DFT) calculations using a polarizable continuum model (PCM) for the solvent, employing the PBE0 functional together with the 6‐311G(d,p) basis set for geometry optimization, and the 6‐311+G(2d,p) basis set for calculating the NMR shielding with the gauge‐including atomic orbitals (GIAO) method. This study adds new information on the sensitivity of the ¹⁷O nucleus to conformational changes, revealing a strong dependence of the ¹⁷O NMR chemical shift on the dihedral angle between the carbonyl and the vinyl moiety in all studied compounds; remarkable differences are observed with the data reported for α‐diketones. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrogen‐Bonding in Cyclic 2‐(3‐Oxo‐3‐phenylpropyl)‐Substituted 1,3‐Diketones: 17O‐NMR Spectra and X‐Ray Structure Determination

Structures of cyclic 2‐(3‐oxo‐3‐phenylpropyl)‐substituted 1,3‐diketones 4a – c were determined by ¹⁷O‐NMR spectroscopy and X‐ray crystallography. In CDCl₃ solution, compounds 4a – c form an eight‐membered‐ring with intramolecular H‐bonding between the enolic OH and the carbonyl O(11)‐atom of the phenylpropyl group, as demonstrated by increased shielding of specifically labeled 4a – c in the ¹⁷O‐NMR spectra (Δδ(¹⁷O(11))=36 ppm). In solid state, intermolecular H‐bonding was observed instead of intramolecular H‐bonding, as evidenced by the X‐ray crystal‐structure analysis of compound 4b . Crystals of compound 4b at 293 K are monoclinic with a=11.7927 (12) Å, b=13.6230 (14) Å, c=9.8900 (10) Å, β=107.192 (2)°, and the space group is P2₁/c with Z=4 (refinement to R=0.0557 on 2154 independent reflections).     

13C NMR investigation of the structure of cationic carbonyls in transition metal zeolites

¹³C NMR spectroscopy was used to investigate the nature of carbon monoxide adsorbed on transition metal ions hosted in a synthetic faujasite type zeolite. The adsorbed CO species was characterised by a highly shielded carbon nucleus. Using the Pople approximation for the paramagnetic shielding term, the observed chemical shift was rationalised assuming the formation of a cationic carbonyl species with an appreciable electronic transfer from the carbon lone pair to the transition metal ion and negligible π back-bonding if at all.     

Effect of collision interactions on 13C nuclear magnetic shielding in monosubstituted benzenes in halogen-containing solvents

The ¹³C nuclear magnetic shielding in benzene and ten monosubstituted benzenes was studied when these compounds were dissolved in cyclohexane, carbon tetrachloride, tetrachloroethylene, methylene bromide and methylene iodide. The results revealed that the observed changes of ¹³C magnetic shielding are dependent on both the solute and solvent molecular properties, although the dependence on the solvent is much more significant. It was also shown that the solvent effects for aromatic carbons are independent of the π electron density distribution in an aromatic ring. The observed ¹³C deshielding was attributed mainly to overlap effects which take place during molecular collisions.     

Reactivity of an N,N‐Chelated Germylene Toward Substituted Alkynes,Alkenes, and Allenes

Treatment of N,N‐chelated germylene [(iPr)₂NB(N‐2,6‐Me₂C₆H₃)₂]Ge ( 1 ) with ferrocenyl alkynes containing carbonyl functionalities, FcC≡CC(O)R, resulted in [2+2+2] cyclization and formation of the respective ferrocenylated 3‐Fc‐4‐C(O)R‐1,2‐digermacyclobut‐3‐enes 2 – 4 [R = Me ( 2 ), OEt ( 3 ) and NMe₂ ( 4 )] bearing intact carbonyl substituents. In contrast, the reaction between 1 and PhC(O)C≡CC(O)Ph led to activation of both C≡C and C=O bonds producing bicyclic compound containing two five‐membered 1‐germa‐2‐oxacyclopent‐3‐ene rings sharing one C–C bond, 4,8‐diphenyl‐3,7‐dioxa‐2,6‐digermabicyclo[3.3.0]octa‐4,8‐diene ( 5 ). With N‐methylmaleimide containing an analogous C(O)CH=CHC(O) fragment, germylene 1 reacted under [2+2+2] cyclization involving the C=C double bond, producing 1,2‐digermacyclobutane 6 with unchanged carbonyl moieties. Finally, 1 selectively added to the terminal double bond in allenes CH₂=C=CRR′ giving rise to 3‐(=CRR′)‐1,2‐digermacyclobutanes [R/R′ = Me/Me ( 7 ), H/OMe ( 8 )] bearing an exo‐C=C double bond. All compounds were characterized by ¹H, ¹³C{¹H} NMR, IR and Raman spectroscopy and the molecular structures of 3 , 4 , 5 , and 8 were established by single‐crystal X‐ray diffraction analysis. The redox behavior of ferrocenylated derivatives 2 – 4 was studied by cyclic voltammetry.     

An ab initio study of the influence of substituents and intramolecular hydrogen bonding on the carbonyl bond length and stretching force constant. I. Monosubstituted carbonyl compounds

The C?O bond length and f_C?O,C?O, the corresponding harmonic stretching force constant, are calculated ab initio using the 4-31G basis set (augmented by polarization functions on the sulfur and chlorine) with full geometry optimization for the monosubstituted carbonyl compounds RCHO, where R = H, CHO, CH?CH₂, CO₂H, CH?CHOH, OH, OC(?O)OH, OOH, S? H, Li, F, Cl, and NH₂. Straight-line relationships are found in plots of ln[f_C?O,C?O] vs. ln[r_C?O] for the series of compounds in which carbon atoms and oxygen atoms are bonded directly to the carbonyl carbon, in accordance with the empirical expression f = C′/rⁿ. The slopes and intercepts give n = 7.62 and 6.47, C′ = 62.6 and 48.6, for the lines with carbon and oxygen as the atom bonded directly to the carbonyl carbon, respectively. The point for formaldehyde lies very close to the C line, whereas the points for SH, Li, F, Cl, and NH₂ lie closer to the O line.     

Some fluorinated heterocyclic and acyclic derivatives of chlorocarbonylsulfenyl chloride

For the first time, fluorinated oxathialones, polyfluoroalkylchlorothioformates, chlorocarbonylpolyfluoroalkylsulfenate esters, a chlorocarbonylhexafluoroisopropylidenimino sulfenate, and a 5-tri-fluoromethyl-2-oxo-1,3,4-oxathiazole were synthesized by reacting chlorocarbonylsulfenyl chloride with R_fC(O)CH₂C(O)R′ (R_f = CF₃; R'= CF₃, OC₂H₅), R_fO^-Li⁺ (R_f = CF₃CH₂, (CF₃)₂C=N^-Li⁺ and CF₃C(O)NH₂. Perfluorosuccinic acid and mercury(II) trifluoroacetate with ClC(O)SCI gave their respective anhydrides.     

Effect of the X and Y substituents on the carbonyl bond in 4-YC<Subscript>6</Subscript>H<Subscript>4</Subscript>C(O)X compounds

Mechanistic aspects of the effect of the X and Y substituents (X = Me, H, CF₃, CN, Br, Cl, F, OH, NH₂; Y = H, NMe₂, NH₂, CN, NO₂) on the carbonyl bond in 4-YC₆H₄C(O)X compounds are discussed on the basis of the ¹³C and ¹⁷O NMR data.     

Action des perfluoroalkylcuivre(I) sur les perfluoroalkylethylenes

A series of new polyfluorinated dienes 3, containing the novel -CFCHCHCF-, pattern has been synthesized (50–70% yields) by reacting perfluoroalkyl iodides with perfluoroalkyl-ethylenes in the presence of copper. The monoalkenes R_fCFCHCH₂CF₂R′_f and the saturated compounds R_fCF₂CH₂CH₂CF₂R′_f were obtained by varying the experimental conditions. The ¹H and ¹⁹F NMR spectra are analysed and the reaction mechanism is discussed.     

Gas-phase 13C chemical shifts in the zero-pressure limit: refinements to the absolute shielding scale for 13C

¹³C chemical shifts have been measured relative to ¹³CO in the zero-pressure limit for over twenty molecules for which theoretical calculations of ¹³C nuclear shielding have recently been reported. Rovibrational averaging effects on the spin-rotation constant in ¹³C¹⁶O have been used to find σ_e(¹³C in ¹³C¹⁶O) = 3.0 ± 1.2 ppm and σ₀(¹³C in ¹³C¹⁶O) = 1.0 ± 1.2 ppm. With the latter, the σ₀ values for the ¹³C nuclei in this work have been determined absolutely and compared with calculated values. Agreement is generally good in most cases except where low-lying n → π transitions contribute significantly to the paramagnetic shielding.     

Different cyclic motifs in phosphoric triamides containing a C(O)NHP(O)(NH)2 skeleton and an R22(10) graph set in three new compounds: a database analysis of hydrogen‐bond strengths based on motifs

In the crystal networks of N,N′‐bis(2‐chlorobenzyl)‐N′′‐(2,6‐difluorobenzoyl)phosphoric triamide, C₂₁H₁₈Cl₂F₂N₃O₂P, (I), N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis(4‐methoxybenzyl)phosphoric triamide, C₂₃H₂₄F₂N₃O₄P, (II), and N‐(2‐chloro‐2,2‐difluoroacetyl)‐N′,N′′‐bis(4‐methylphenyl)phosphoric triamide, C₁₆H₁₇ClF₂N₃O₂P, (III), C=O...H—N_C(O)NHP(O) and P=O...H—N_amide hydrogen bonds are responsible for the aggregation of the molecules. This is the opposite result from that commonly observed for carbacylamidophosphates, which show a tendency for the phosphoryl group, rather than the carbonyl counterpart, to form hydrogen bonds with the NH group of the C(O)NHP(O) skeleton. This hydrogen‐bond pattern leads to cyclic R₂²(10) motifs in (I)–(III), different from those found for all previously reported compounds of the general formula RC(O)NHP(O)[NR¹R²]₂ with the syn orientation of P=O versus NH [R₂²(8)], and also from those commonly observed for RC(O)NHP(O)[NHR¹]₂ [a sequence of alternate R₂²(8) and R₂²(12) motifs]. In these cases, the R₂²(8) and R₂²(12) graph sets are formed through similar kinds of hydrogen bond, i.e. a pair of P=O...H—N_C(O)NHP(O) hydrogen bonds for the former and two C=O...H—N_amide hydrogen bonds for the latter. This article also reviews 102 similar structures deposited in the Cambridge Structural Database and with the International Union of Crystallography, with the aim of comparing hydrogen‐bond strengths in the above‐mentioned cyclic motifs. This analysis shows that the strongest N—H...O hydrogen bonds exist in the R₂²(8) rings of some molecules. The phosphoryl and carbonyl groups in each of compounds (I)–(III) are anti with respect to each other and the P atoms are in a tetrahedral coordination environment. In the crystal structures, adjacent molecules are linked via the above‐mentioned hydrogen bonds in a linear arrangement, parallel to [010] for (I) and (III) and parallel to [100] for (II). Formation of the N_C(O)NHP(O)—H...O=C instead of the N_C(O)NHP(O)—H...O=P hydrogen bond is reflected in the higher N_C(O)NHP(O)—H vibrational frequencies for these molecules compared with previously reported analogous compounds.     

Intermolecular interactions in the chiral and racemic forms of 3‐­hydroxy‐2‐(1‐oxoisoindolin‐2‐yl)­butanoic acid derived from threonine

The title compounds, C₁₂H₁₃NO₄, are derived from l ‐threonine and dl ‐threonine, respectively. Hydro­gen bonding in the chiral derivative, (2S/3R)‐3‐hydroxy‐2‐(1‐oxoisoindolin‐2‐yl)­butanoic acid, consists of O—H_acid?O_alkyl—H?O=C_indole chains [O?O 2.659 (3) and 2.718 (3) Å], Csp³—H?O and three C—H?π_arene interactions. In the (2R,3S/2S,3R) racemate, conventional carboxylic acid hydrogen bonding as cyclical (O—H?O=C)₂ [graph set R₂²(8)] is present, with O_alkyl—H?O=C_indole, Csp³—H?O and C—H?π_arene interactions. The COOH group geometry differs between the two forms, with C—O, C=O, C—C—O and C—C=O bond lengths and angles of 1.322 (3) and 1.193 (3) Å, and 109.7 (2) and 125.4 (3)°, respectively, in the chiral structure, and 1.2961 (17) and 1.2210 (18) Å, and 113.29 (12) and 122.63 (13)°, respectively, in the racemate structure. The O—C=O angles of 124.9 (3) and 124.05 (14)° are similar. The differences arise from the contrasting COOH hydrogen‐bonding environments in the two structures.     

Chemical shift correlations in the 13C, 17O and 31P NMR spectra of some Mo(CO)4((PPh2O)2Y(R)R′) (Y(R) = P(O), Si(Me); R′ = alkyl,haloalkyl, aryl) and [Mo(CO)4(PPh2O)2]2Si complexes

The syntheses and ¹³C, ¹⁷O, ²⁹Si and ³¹P NMR spectra of a series of Mo(CO)₄((PPh₂O)₂Y(R)R′) (Y(R) = P(O), Si(Me); R′=alkyl, haloalkyl, aryl) and [Mo(CO)₄(PPh₂O)₂]₂Si complexes are given. The chemical shift ranges of the cis and trans carbonyl ¹³C and ¹⁷O, phenyl C(1) ¹³C and ³¹P resonances are relatively large and, with the exception of the cis carbonyl ¹⁷O chemical shifts, the correlations between the chemical shifts of the various resonances are excellent. These correlations are consistent with the model of metal carbonyl ¹³C and ¹⁷O chemical shifts proposed by Bodner and Todd. In addition they allow the model to be extended to include the diphenylphosphinite ³¹P chemical shifts in these complexes. The excellent correlations may be due to the presence of the chelate ring which limits the rotation around the molybdenum-phosphorus bond and to the fact that all three groups directly bonded to the phosphorus remains constant.     

Résonance Magnétique Nucléaire de 17O. Aldéhydes et cétones aliphatiques: additivité des effets de substitution et corrélation avec la 13C-RMN

¹⁷O-NMR. Aliphatic aldehydes and ketones, additivity of substituent effects and correlation with ¹³C-NMR. The ¹⁷O-chemical shifts of 9 aldehydes, 22 aliphatic and 4 alicyclic ketones, in the natural abundance FT.-NMR. spectra followed a good correlation with the ¹³C-chemical shifts of the terminal C-atoms of corresponding methylene compounds. An additivity relation involving 6 parameters represents the ¹⁷O-shifts of 28 of the measured products with a standard deviation of 2.5 ppm. The additivity parameters are discussed with respect to the modifications of the polarity of the carbonyl group induced by the hyperconjugative interaction of π and π* orbitals with the πCH ₃ orbitals of the alkyl substituent groups.