High resolution 13C NMR spectroscopy. IV—stereochemical assignments in butenedioic acids and 3-pentene-2-ones

Vicinal ¹³C, H coupling constants ³J(CO, H) for butenedioic acids and ³J(CH₃, H) for 3-pentene-2-ones have been determined and are correlated with the configuration of the corresponding C?C double bond. For both types the relationship ³J(CH) trans > ³J(CH)cis holds; in the case of the CH₃, H couplings, however, the ³J(CH₃, H) trans values are reduced because of steric reasons, so that configurational assignments seem possible only when both isomers are present. Additionally, the coupling constants ³J(COC H₃,H ) and the chemical shifts δ have been evaluated for the pentenones and it is shown that these parameters give information about the predominating conformation of α, β-unsaturated methyl ketones.     

Etude par resonance magnetique nucleaire des interactions noyau-substituant dans les acetanilides para-substitues

The NMR spectra of fifteen para-substituted acetanilides, XC₆H₄·NH·CO·CH₃ (X = NH·CO·Me; NH₂; CO·OEt; COOH; Cl; OEt; F; H; OMe; CH₃; NO₂; C₆H₅; ? N?N? C₆H₅; Me₃Si), have been recorded. δ and δ_NH are linearly related to Hammett's σ_p constant. The coupling J (o-H? H) between aromatic protons is mainly dependent on σ_R⁰. J(¹³C? H), in methyl group is approximatively constant in the series.     

Korrelation Tolmanscher Kegelwinkel mit 1J-Werten von Phosphoniumfluorsulfonaten

The Correlation of Tolman's Cone Angles with ¹J of Phosphonium Fluorosulfonates A ¹H-n.m.r. study of three series of phosphonium salts [HPR_3?nH_n]X, and [HPPh₂R_1?nH_n]X and (R = aliphatic substituent and H, X = SO₃ F) gives a good relationship between increasing values of ¹J versus decreasing size of substituted phosphines. A method to obtain Tolman's cone angle is described.     

Etude par Résonance Magnétique Nucléaire du carbone 13 de complexes du cobalt (III) et de la diméthylglyoxime

From a carbon magnetic resonance study of several alkylcobaloximes RCo(DMG)₂B (DMG = dimethylglyoximate monoanion), it was possible to estimate the α, β and γ effects of the Co(DMG)₂B group on the chemical shifts of the carbon atoms of various alkyl groups R. The chemical shifts of the carbon atoms belonging to the equatorial ligands and to the axial base B are not significantly affected by structural modification of the R groups. Values of δ in benzylcobaloximes XC₆H₄CH₂Co(DMG)₂B agree with a donor effect of the ? CH₂Co(DMG)₂B radical. Values of ¹J(¹³C? H) coupling constants, measured in ¹³C enriched methylcobaloximes, do not vary appreciably when B is changed (J(¹³C? H) = 137 ± 1 Hz) and are close to the value obtained for methylcobalamine.     

Transition‐Metal‐Catalyzed CH Bond Functionalizations: Feasible Access to a Diversity‐Oriented β‐Carboline Library

Diversification of the β‐carboline skeleton has been demonstrated to assemble a β‐carboline library starting from the tetrahydro‐β‐carboline framework. This strategy affords feasible access to heteroaryl‐, aryl‐, alkenyl‐, or alkynyl‐substituted β‐carbolines at the C1, C3, or C8 position through three categorically different types of transition‐metal‐catalyzed C?C bond‐forming reactions, in the presence of multiple potentially reactive positions. These site‐selective functionalizations include; 1) the Cu‐catalyzed C1/C3‐selective decarboxylative C?C and C?C_sp coupling of hexahydro‐β‐carboline‐3‐carboxylic acid with a C?H bond of a heteroarene or terminal alkyne; 2) the chelation‐assisted Pd‐catalyzed C1/C8‐selective C?H arylation of hexahydro‐β‐carboline with aryl boron reagents; and 3) the chelation‐assisted Pd‐catalyzed C1/C3‐selective oxidative C?H/C?H cross‐coupling of β‐carboline‐N‐oxide with arenes, heteroarenes, or alkenes. The saturated structural feature of the hexahydro‐β‐carboline framework can increase reactivity and control site selectivity. The robustness of these approaches has been demonstrated through the synthesis of hyrtioerectine analogues and perlolyrine. We believe that these strategies could provide inspiration for late‐stage diversifications of bioactive core scaffolds.     

Aryl‐Copper(III)‐Acetylides as Key Intermediates in CCsp Model Couplings under Mild Conditions

The mechanism of copper‐mediated Sonogashira couplings (so‐called Stephens–Castro and Miura couplings) is not well understood and lacks clear comprehension. In this work, the reactivity of a well‐defined aryl‐Cu^III species ( 1 ) with p‐R‐phenylacetylenes (R=NO₂, CF₃, H) is reported and it is found that facile reductive elimination from a putative aryl‐Cu^III‐acetylide species occurs at room temperature to afford the C_aryl?C_sp coupling species ( I_R ), which in turn undergo an intramolecular reorganisation to afford final heterocyclic products containing 2H‐isoindole ( P , P , P_Ha ) or 1,2‐dihydroisoquinoline ( P_Hb ) substructures. Density Functional Theory (DFT) studies support the postulated reductive elimination pathway that leads to the formation of C?C_sp bonds and provide the clue to understand the divergent intramolecular reorganisation when p‐H‐phenylacetylene is used. Mechanistic insights and the very mild experimental conditions to effect C_aryl?C_sp coupling in these model systems provide important insights for developing milder copper‐catalysed C_aryl?C_sp coupling reactions with standard substrates in the future.     

Amines α et β acétyléniques. Couplages J(15N?H), J(15N?13C) et hybridation de l'azote

¹H and ¹³C NMR spectra of ¹⁵N-methylaniline, ¹⁵N-methylphenylpropargylamine and ¹⁵N-methylphenylpropynylamine have been studied. The s character of nitrogen, deduced from ¹J(¹⁵N? ¹³C) and ¹J(¹⁵N? ¹³C), indicates that nitrogen hybridisation is intermediate between sp³ and sp² in ¹⁵N-methylaniline and ¹⁵N-methylphenylpropargylamine, while nitrogen is sp² in the α-acetylenic amine. The ¹J(¹⁵N? ¹³C_sp)cou pling constant calculated with the help of Binsch's relation does not agree with the experimental value, suggesting that orbital and dipolar mechanisms make substantial contributions to this coupling constant.     

Copper‐Catalyzed Aerobic Oxidative NS Bond Functionalization for CS Bond Formation: Regio‐ and Stereoselective Synthesis of Sulfones and Thioethers

A regio‐ and stereoselective synthesis of sulfones and thioethers by means of Cu^I‐catalyzed aerobic oxidative N?S bond cleavage of sulfonyl hydrazides, followed by cross‐coupling reactions with alkenes and aromatic compounds to form the C?S bond, is described herein. N₂ and H₂O are the byproducts of this transformation, thus offering an environmentally benign process with a wide range of potential applications in organic synthesis and medicinal chemistry.     

Couplages J des groupes méthyle dans les phényltriméthylsilanes p-substitués: Effets de solvants

The J coupling constants of a series of p-substituted phenyltrimethylsilanes were measured in CH₂Cl₂ and CCl₄ solutions. The solvent effect is discussed; it is too large to allow any straightward conclusion on ring-substituent interaction.     

The quantum efficiency of the primary processes in formaldehyde photolysis at 3130 Å and 25°C

The mechanism of the photolysis of formaldehyde was studied in experiments at 3130 Å and in the pressure range of 1–12 torr at 25°C. The experiments were designed to establish the quantum yields of the primary decomposition steps (1) and (2), CH₂O + hν → H + HCO (1): CH₂O + hν → H₂ + CO (2), through the effects of added isobutene, trimethylsilane, and nitric oxide on Φ_CO and Φ. The ratio Φ_CO/Φ was found to be 1.01 ± 0.09(2σ) and (Φ + Φ_CO)/2 = 1.10 ± 0.08 over the range of pressures and a 12-fold change in incident light intensity. Isobutene and nitric oxide additions reduced Φ to about the same limiting value, 0.32 ± 0.03 and 0.34 ± 0.04, respectively, but these added gases differed in their effects on Φ_CO. With isobutene addition Φ_CO/Φ reached a limiting value of 2.3; with NO addition Φ_CO exceeded unity. The addition of small amounts of Me₃SiH reduced Φ to 1.02 ± 0.08 and lowered Φ_CO to 0.7. These findings were rationalized in terms of a mechanism in which the “nonscavengeable,” molecular hydrogen is formed in reaction (2) with ?₂ = 0.32 ± 0.03, while the “free radical” hydrogen is formed in reaction (1) with ?₁ = 0.68 ± 0.03. In the pure formaldehyde system these reactions are followed by (3)–(5): H + CH₂O → H₂ + HCO (3); 2HCO → CH₂O + CO (4); 2HCO → H₂ + 2CO (5). The data suggest k₄/k₅ ? 5.8. Isobutene reduced Φ by the reaction H + iso-C₄H₈ → C₄H₉ (20), and the results give k₂₀/k₃ ? 43 ± 4, in good agreement with the ratio of the reported values of the individual constants k₃ and k₂₀.     

1,3,5-Trideoxy-1,3,5-tris(dimethylamino)-cis-inositol,an Efficient Ligand for Hard Trivalent Metal Ions. Determination of the stability constants of the FeIII,AlIII, and CuII complexes in aqueous solution

The complexes [Fe(tdci)₂]Cl₃ and [Al(tdci)₂]Cl₃ (tdci = 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol) were prepared and characterized by mass spectrometry, NMR spectroscopy, and magnetic-susceptibility measurements. The formation constants were determined in aqueous solution (25°, 0.1M KCl) by potentiometric titration. pK values of H₃(tdci)³⁺: 5.89, 7.62, 9.68; Fe^III complexes: log β_ML = 18.8, log β = 32.6; Al^III complexes: log β_ML = 14.3, logβ = 26.4. The protonated complex [FeH(tdci)₂]⁴⁺ has also been identified. In contrast to the high stability of the Fe^III and Al^III complexes, only weak interactions of tdci with Cu^II have been observed in aqueous solution (25°, 0.1M KNO₃).     

The mechanism of O(3P) atom reaction with ethylene and other simple olefins

Reactions of oxygen atoms with ethylene, propene, and 2-butene were studied at room temperature under discharge flow conditions by resonance fluorescence spectroscopy of O and H atoms at pressures of 0.08 to 12 torr. The measured total rate constants of these reactions are K = (7.8 ± 0.6)·10^?13cm³s^?1,K = (4.3 ± 0.4) ± 10^?12 cm³ s^?1, K = (1.4 ± 0.4) · 10^?11 cm³ s^?1. The branching ratios of H atom elimination channels were measured for reactions of O atoms with ethylene and propene. No H-atom elimination was found for the reaction of O-atoms with 2-butene. A redistribution of reaction O + C₂ channels with pressure was found. A mechanism of the O + C₂ reaction was proposed and the possibility of its application to other olefins is discussed. On the basis of mechanism the pressure dependence of the total rate constant for reaction O + C₂ was predicted and experimentally confirmed in the pressure range 0.08–1.46 torr.     

trans Influence and Steric Effect on the Distortions in Planar NiS4, NiS2PN,and NiS2P2 Chromophores

The planar diamagnetic complexes [Ni(achdtc)₂] ( 1 ),[Ni(achdtc)(PPh₃)(NCS)] ( 2 ), and [Ni(achdtc)(PPh₃)₂]ClO₄ · 0.5EtOAc ( 3 ) (achdtc = allylcyclohexylcarbodithioate) were prepared, characterized by elemental analysis, electronic, IR, NMR (¹H, ¹³C, and ³¹P) spectroscopy and the crystal structures were determined by single‐crystal X‐ray crystallography. The characteristic thioureide bands occur at 1478, 1503, and 1507 cm^–1 for 1 , 2 , and 3 , respectively and the corresponding ¹³C chemical shifts are observed at 207.67, 204.16, and 202.31 ppm. ³¹P chemical shifts are observed at δ = 29.24 and 22.73 ppm for 2 and 3 , respectively, indicating a strong interaction. Electronic spectral bands are observed at 480, 483, and 475 nm for 1 , 2 , and 3 , corresponding to d → d_xy/d transitions. Ni–S distances are asymmetric. The trans influence of PPh₃ elongates the Ni–S bonds. The decrease in the S–Ni–S bite angle in 2 [78.80(16)°] and in 3 [78.36(2)°] compared to that observed in 1 [79.42(3)°] is due to the steric crowding of PPh₃ around the central metal atom. A comparison of the bond parameters of compounds 1 – 3 shows a change in the arrangement from a planar NiS₄ chromophore to distorted planar NiS₂P₂ chromophores. The observed distortion from planar to tetrahedral arrangement is influenced by the bulky triphenylphosphine ligand.     

Synthesis and Characterization of a Family of POCOP Pincer Complexes with Nickel: Reactivity Towards CO2 and Phenylacetylene

A cyclohexyl‐based POCOP pincer ligand (POCOP=cis‐1,3‐bis(di‐tert‐butylphosphinito)cyclohexyl) cyclometalates with nickel to generate a series of new POCOP‐supported Ni^II complexes, including the halide, hydride, methyl, and phenyl species. trans‐[NiCl{cis‐1,3‐bis(di‐tert‐butylphosphinito)cyclohexane}], [(POCOP)NiCl] ( 1 a ) and the analogous bromide complex ( 1 b ) were synthesized and fully characterized by NMR spectroscopy and X‐ray crystallography. Cyclic voltammetry measurements of 1 a and 1 b alongside their bis(phosphine) analogues [(PCP)NiCl] ( 2 a ) and [(PCP)NiCl] ( 2 a ) (PCP=cis‐1,3‐bis(di‐tert‐butylphosphino)cyclohexyl) indicate a reduced electron density at the metal center upon introducing electron‐withdrawing oxygen atoms in the pincer arms. The methyl [(POCOP)NiMe] ( 3 ) and phenyl [(POCOP)NiPh] ( 4 ) complexes were formed from 1 a by reaction with the corresponding organolithium reagents. 1 a also reacts with LiAlH₄ to give the hydride complex [(POCOP)NiH] ( 5 ). The methyl complex 3 reacts with phenyl acetylene to give the acetylide complex [(POCOP)NiCCPh] ( 6 ). The reactivity of compounds 3 – 5 towards CO₂ was studied. The hydride complex 5 and the methyl complex 3 both underwent CO₂ insertion to form the formate species [(POCOP)NiOCOH] ( 7 ) and acetate species [(POCOP)NiOCOCH₃] ( 8 ), respectively, although with a higher barrier of insertion in the latter case. Compound 4 was unreactive towards CO₂ even at elevated temperatures. Complexes 3 – 8 were all characterized by NMR spectroscopy and X‐ray crystallography.     

The kinetics of the reaction F + H2 → HF + H. A critical review of literature data

Published experimental studies concerning the determination of rate constants for the reaction F + H₂ → HF + H are reviewed critically and conclusions are presented as to the most accurate results available. Based on these results, the recommended Arrhenius expression for the temperature range 190–376 K is k = (1.1 ± 0.1) × 10⁻¹⁰ exp |-(450 ± 50)/T| cm³ molecule⁻¹ s⁻¹, and the recommended value for the rate constant at 298 K is k = (2.43 ± 0.15) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The recommended Arrhenius expression for the reaction F + D₂ → DF + D, for the same temperature range, based on the recommended expression for k and accurate results for the kinetic isotope effect k/k is k = (1.06 ± 0.12) × 10^×10 exp |-(635 ± 55)/T|cm³ molecule⁻¹ s⁻¹, and the recommended value for 298 K is k = (1.25 ± 0.10) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 67–71, 1997.     

Conformational studies by nuclear magnetic resonance—IV: Restricted rotation in vinylogous thioamides

Enamino -thial and -thiones R¹C(S)CH?CHNR (R¹ = H or alkyl; R² = Me or Et) have been shown by NMR spectra to exist in two rotational forms, s-cis and s-trans, the populations of the latter being approximately the same as in the case of the parent oxa analogues. An increase of the order of 2 to 4 Kcal/mole in the heights of C? C and C? N rotation barriers (ΔG*) was found on comparing the title compounds with their oxa analogues. IR spectra failed as a tool to establish the rotational equilibrium. IR absorption bands of the ν_{C? C}, ν_{C? H} (in the NMe₂ group) and γ_HC?CH vibrations have been found, but the ν_C?S band could not be assigned unambiguously. Anomalies concerning the frequency and intensity of the ν_C?C band are discussed.     

Hyperfine Shifts of the 13C-NMR. in Protoporphyrin IX Iron (III) Dicyanide and Deuteroporphyrin IX Iron (III) Dicyanide

The ¹³C-NMR. in Zn(II) (Protoporphyrin IX), Fe(III) (Protoporphrin IX) (CN)₂, Zn(II) (Deuteroporphyrin IX dimethylester), and Fe(III) (Deuteroporphyrin IX) (CN)₂ have been identified, and the ¹³C hyperfine shifts in the iron complexes evaluated. In a partial analysis of these data the parameters Q^H, Q_CCH^H, and Q_C′CH^C, which characterize the isotropic coupling through hyperconjugation between the ¹H and ¹³C nuclei of the porphyrin side chains and the unpaired electron spin density on the aromatic ring carbon atoms, have been re-examined. This paper is part of an investigation of the electronic states in low spin ferric hemes and hemoproteins, and the relations between the electronic structures and the biological roles of these molecules.     

Über die Reaktion von Schwefel mit Aminen und Formaldehyd. Eine neue Methode zur Herstellung von Thioformamiden und Dithiocarbamaten

The reaction of sulfur with primary or secondary amines and formaldehyde has been studied. A simple one step process for the preparation of thioformamides (RR′NCHS; R ? H, R′ ? CH₃, C₂H₅; R ? R′ ? CH₃, C₂H₅; R+R′ ? ? (CH₂), ? (CH₂), ? C₂H₄OC₂H) and the amine salts of N, N-dialkyl-dithiocarbamic acids (R₂NCS₂ · H₂NR₂, R ? CH₃, C₂H₅, C₄H₉; R₂ ? ? (CH₂), ? (CH₂), ? C₂H₄OC₂H) is reported. In addition, the isolation of diethylamidosulfoxylic acid, (C₂H₅)₂NSOH · 1/2 H₂O, the first derivative of a new class of compounds, is described. The physical properties and the ¹H-NMR. spectra of the above mentioned compounds are given.     

The 13C and D kinetic isotope effects in the reaction of CH4 with Cl

The kinetic isotope effects in the reaction of methane (CH₄) with Cl atoms are studied in a relative rate experiment at 298 ± 2 K and 1013 ± 10 mbar. The reaction rates of ¹³CH₄, ¹²CH₃D, ¹²CH₂D₂, ¹²CHD₃, and ¹²CD₄ with Cl radicals are measured relative to ¹²CH₄ in a smog chamber using long path FTIR detection. The experimental data are analyzed with a nonlinear least squares spectral fitting method using measured high‐resolution spectra as well as cross sections from the HITRAN database. The relative reaction rates of ¹²CH₄, ¹³CH₄, ¹²CH₃D, ¹²CH₂D₂, ¹²CHD₃, and ¹²CD₄ with Cl are determined as k/k = 1.06 ± 0.01, k/k = 1.47 ± 0.03, k/k = 2.45 ± 0.05, k/k = 4.7 ± 0.1, k/k = 14.7 ± 0.3. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 110–118, 2005     

2–Butoxyethanol and benzyl alcohol reactions with the nitrate radical: Rate coefficients and gas‐phase products

The bimolecular rate coefficients k and k were measured using the relative rate technique at (297 ± 3) K and 1 atmosphere total pressure. Values of (2.7 ± 0.7) and (4.0 ± 1.0) × 10^?15 cm³ molecule^?1 s^?1 were observed for k and k, respectively. In addition, the products of 2‐butoxyethanol + NO₃^? and benzyl alcohol + NO₃^? gas‐phase reactions were investigated. Derivatizing agents O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine and N, O‐bis (trimethylsilyl)trifluoroacetamide and gas chromatography mass spectrometry (GC/MS) were used to identify the reaction products. For 2‐butoxyethanol + NO₃^? reaction: hydroxyacetaldehyde, 3‐hydroxypropanal, 4‐hydroxybutanal, butoxyacetaldehyde, and 4‐(2‐oxoethoxy)butan‐2‐yl nitrate were the derivatized products observed. For the benzyl alcohol + NO₃^? reaction: benzaldehyde ((C₆H₅)C(?O)H) was the only derivatized product observed. Negative chemical ionization was used to identify the following nitrate products: [(2‐butoxyethoxy)(oxido)amino]oxidanide and benzyl nitrate, for 2‐butoxyethanol + NO₃^? and benzyl alcohol + NO₃^?, respectively. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with a plausible 2‐butoxyethanol or benzyl alcohol + NO₃^? reaction mechanisms based on previously published volatile organic compound + NO₃^? gas‐phase mechanisms. © 2012 Wiley Periodicals, Inc.

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

© 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 778–788, 2012