73222-61-4

Partially deuterated and 13C-labeled bis(biphenylenyl)propenyl radicals have been studied by means of ESR and ENDOR spectroscopy.Isotropic and anisotropic hyperfine contributions could be determined from measurements in isotropic solutions and in nematic and smectic phases of liquid crystals.Assignments of hyperfine coupling constants and shifts to molecular positions were achieved.Conclusions concerning molecular structure, e.g., twist angles, could be drawn by relating the experimental data to quantum mechanical calculations.These results could be confirmed by taking account of the 13C hyperfine shifts determined by ESR and 13C ENDOR experiments.A marked isotope effect on the β-proton hyperfine coupling could be observed when replacing 1H by 2H in the biphenylenyl moieties.The essential feature of the 2H ENDOR measurements in liquid crystals is the detection of deuterium quadrupole splittings.The relaxation behavior of the different magnetic nuclei is discussed.A novel multinuclear ENDOR standard for checking the engineering design of a liquid-phase ENDOR spectrometer is proposed.

N-Methylation of amines with CO2/H2 to N-methylamines over non-noble metal catalysts is very interesting but remains challenging. Herein, we present an alcohol (e.g., ethanol) promoted strategy for the N-methylation of anilines with CO2/H2 with high efficiency under mild conditions (e.g., 125 °C), which is achieved over a cobalt catalytic system composed of Co(OAc)2·4H2O, triphos and Sn(OTf)2. This catalytic system has a broad substrate scope and is tolerant toward a wide range of anilines and N-methyl anilines, and a series of N,N-dimethyl anilines were obtained in high yields. Mechanism investigation indicates that the alcohol solvent shifts the equilibrium of CO2 hydrogenation by forming an alkyl formate, which further reacts with the amine to produce N-formamide, and Sn(OTf)2 promotes the deoxygenative hydrogenation of N-formamides to afford N-methylamines. This is the first example of the N-methylation of amines with CO2/H2 over a cobalt catalytic system, which shows comparable performance to the reported Ru catalysts and may have promising applications.

A low-temperature CH3OH synthesis was achieved at 120-170 °C using tertiary amine and alcohol in the presence of a Cu/ZnO/Al2O3 catalyst by CO2 hydrogenation. A series of 1°, 2° and 3° amines and alcohols were screened to study their influence on the formation of CH3OH. Particularly, 3° amines such as NEt3 in combination with EtOH formed CH3OH with 100% yield with respect to the amine. Unlike the traditional gas-phase heterogeneous metal catalyzed CO2-to-CH3OH reactions, no CO is used in the feed gas mixture in this method. In addition, the hydrogenation gives good selectivity (>95%) to CH3OH and only trace amounts of CO and CH4 are formed. The presence of CO in the gas mixture was attributed to the decomposition of the CH3OH product, which was confirmed by high-temperature and high-pressure MAS NMR. The reaction was performed in the condensed phase at relatively lower temperatures, thus the RWGS reaction, which typically operates at >250 °C, was significantly reduced at these temperatures (120-170 °C). The first in situ spectroscopic evidence for the condensed phase hydrogenation of alkylcarbonate to CH3OH via ammonium formate and alkylformate intermediates was also presented under the experimental conditions.

The chemistry of [13C]methyl phenyl sulfide is exploited to produce new isotopically labeled precursors that allow for the facile assembly of a wide range of labeled molecules from simple and relatively inexpensive starting materials. These compounds are applicable to a variety of research areas such as quantum computing, metabolism and materials science.

An efficient synthesis of [1-13C]-para-xylene (1a) and [2-13C]-para-xylene (1b) is described. The incorporation of the label has been achieved by cyclocondensation of suitable 1,5-bis(bromomagnesio)alkanes with either ethyl [1-1

Nitroxides (Aminyl Oxides), 43.- The Effect of Structural Features upon the Dimerization of Vinyl Nitroxides Substituted in β-Position by cyclic Acyl Groups Reaction between N-alkyl- and N-arylhydroxylamines and hydroxymethylene compounds 4 (derivatives of menthone, norbornanone, bornanone, indanone, and γ-butyrolactone) affords nitrones existing in the tautomeric forms 5 and 6.Oxidation of these nitrones generates the β-acylated vinyl nitroxides 7, which dimerize in various ways.The N-alkyl-susbstituted vinyl nitroxides 7Da, De, Ea, Ga, and Gf yield simple CC-bonded dimers 8.From 7Ba dimer 10 is formed via 8Ba.The structure of 10 is confirmed by an X-ray analysis.In contrast, the N-aryl-substituted vinyl nitroxides 7Ab, Fc, and Bc as well as the N-alkyl-substituted 7Aa afford the bicyclic dimers 9 which arise by OC dimerization followed by an intramolecular 1,3-dipolar cycloaddition.Finally, the vinyl nitroxides 7Dc and Dd underwent further oxidation to give dehydrodimers 12. 12e is formed only if 6De is oxidized by a large excess of lead dioxide.

Samples of 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (Trimethoprim) were synthesized, enriched with 13C at the following positions: 2 and 5; 4 and 6; α and 4-methoxy.For the first two series (having 13C-enrichment at the pyrimidine), appropriately labelled cyanoacetic acid was converted into labelled methyl 2-(3,4,5-trimethoxybenzyl)cyanoacetate and thence to the labelled 6-hydroxy derivative of Trimethoprim.For the last series (having 13C-enrichment at the trimethoxybenzyl moiety), the key reaction was the nucleophilic attack of C-5 of 2,4-diamino-6-hydroxypyrimidine on labelled 3,4,5-trimethoxybenzyl bromide, again yielding the labelled 6-hydroxy derivative of Trimethoprim.The conversion of the 6-hydroxy derivatives into 13C enriched Trimethoprim was via the 6-chloride.Also synthesized was -2,4-diaminopyrimidine by cyclization of guanidine and -3-anilino-acrylonitrile.The identity, and the site(s) of the 13C label(s) of each final product and intermediate, were established on the basis of 1H and 13C n.m.r. spectral evidence.