A novel synthetic route to 2-halo-3,4-dicyanopyridines

2-Bromo-3,4-dicyanopyridine 2 was obtained in moderate yield by reacting 1,1,2,2-tetracyano-3-trimethylsiloxycyclobutane 1 with phosphorus tribromide. Similarly, reaction of 1 with chlorinating reagents such as thionyl chloride and oxalyl chloride led to the corresponding 2-chloro-3,4-dicyanopyridine 3 in 40% yield. A reaction mechanism is suggested.     

Highly enantioselective synthesis of alpha-alkyl-alanines via the catalytic phase-transfer alkylation of 2-naphthyl aldimine tert-butyl ester by using O(9)-allyl-N(1)-2',3',4'-trifluorobenzylhydrocinchonidinium bromide

Systematic investigations to develop an efficient enantioselective synthetic method for alpha-alkyl-alanine by catalytic phase-transfer alkylation were performed. The alkylation of 2-naphthyl aldimine tert-butyl ester, 1E, with RbOH and O(9)-allyl-N-2',3',4'-trifluorobenzylhydrocinchonidinium bromide, 6, at -35 degrees C showed the highest enantioselectivities, up to 96% ee.     

Chromatographic characteristics of cholesterol-imprinted polymers prepared by covalent and non-covalent imprinting methods

Cholesterol-imprinted polymers were prepared in bulk polymerization by the methods of covalent and non-covalent imprinting. The former involved the use of a template-containing monomer, cholesteryl (4-vinyl)phenyl carbonate, while the latter used the complexes of template and functional monomer, methacrylic acid or 4-vinylpyridine prior to polymerization. Columns packed with these molecularly imprinted polymers (MIPs) were all able to separate cholesterol from other steroids. For different combinations of cholesterol and beta-estradiol concentrations in a total of 1 g/l, the peak retention times for both compounds were nearly constant. The adsorption capacity for cholesterol onto the MIPs was found to significantly depend on the use of functional monomers, but the selectivity factors were only slightly different from each other at 2.9 to 3.2 since the separation was all based on the specific binding of cholesterol to recognition sites formed on the imprinted polymers. The capacity factors for cholesterol were determined to be 3.5, 4.0 and 3.1, respectively, for covalently imprinted, 4-vinylpyridine-based, and methacrylic acid-based non-covalently imprinted polymers. However, the covalently imprinted polymer was found to have a higher adsorption capacity for cholesterol and about fivefold higher chromatographic efficiency for cholesterol separation, in comparison with non-covalently imprinted polymers. The use of covalent imprinting significantly reduced the peak broadening and tailing. This advantage along with constant retention suggests that the covalently imprinted polymer has potential for quantitative analysis.     

Ruthenium‐catalyzed formal alkyl group transfer: Synthesis of quinolines from nitroarenes and alkylammonium halides

Nitroarenes are reductively cyclized with an array of tetraalkylammonium halides and trialkylarnmonium chlorides in the presence of a catalytic amount of a ruthenium catalyst along with tin(II) chloride dihydrate at 180° to afford the corresponding quinolines in moderate to good yields. The addition of tin(II) chloride dihydrate is necessary for the effective formation of quinolines and toluene is the solvent of choice. A reaction pathway involving initial reduction of nitroarenes to anilines and conversion of alkylammonium halides to alkylamines, alkyl group transfer from alkylamines to anilines to form an imine, dimerization of imine, and heteroannulation is proposed for this catalytic process.     

Matching-pursuit/split-operator-Fourier-transform computations of thermal correlation functions

A rigorous and practical methodology for evaluating thermal-equilibrium density matrices, finite-temperature time-dependent expectation values, and time-correlation functions is described. The method involves an extension of the matching-pursuit/split-operator-Fourier-transform method to the solution of the Bloch equation via imaginary-time propagation of the density matrix and the evaluation of Heisenberg time-evolution operators through real-time propagation in dynamically adaptive coherent-state representations.     

Kinetics and mechanism of benzylamine additions to ethyl alpha-acetyl-beta-phenylacrylates in acetonitrile

Kinetic studies of the addition of benzylamines to a noncyclic dicarbonyl group activated olefin, ethyl alpha-acetyl-beta-phenylacrylate (EAP), in acetonitrile at 25.0 degrees C are reported. The rates are lower than those for the cyclic dicarbonyl group activated olefins. The addition occurs in a single step with concurrent formation of the Calpha-N and Cbeta-H bonds through a four-center hydrogen bonded transition state.The kinetic isotope effects (kH/kD > 1.0) measured with deuterated benzylamines (XC6H4CH2ND2) increase with a stronger electron acceptor substituent (deltasigmaX > 0) which is the same trend as those found for other dicarbonyl group activated series (1-4), but is in contrast to those for other (noncarbonyl) group activated series (5-9). For the dicarbonyl series, the reactivity-selectivity principle (RSP) holds, but for others the anti-RSP applies. These are interpreted to indicate an insignificant imbalance for the former, but substantial lag in the resonance delocalization in the transition state for the latter series.     

Highly efficient Pd-catalyzed carbonylative cross-coupling reactions with tetraorganoindates

Tetraorganoindates, which were prepared easily from the reaction of 1 equiv of InCl(3) with 4 equiv of organometallics, could be employed as effective nucleophilic cross-coupling partners in Pd-catalyzed carbonylative cross-coupling reactions with a variety of organic electrophiles. The present method gave unsymmetrical ketones and 1,4-diacylbenzenes in good yields with highly efficient transfer of almost all the organic groups attached to the indium under a carbon monoxide atmosphere in THF at 60 degrees C.     

Application of Arene-Ruthenium Chemistry to a Formal Total Synthesis of OF 4949 III

A convergent formal total synthesis of OF 4949 III is described. Arene-ruthenium chemistry was used in the construction of the diaryl ether linkage in high yield, and cycloamidation under high dilution conditions (0.005 M) was achieved using DPPA as coupling reagent. SmI(2) was used to reductively remove the 2-iodoethyl ester protecting group in the presence of DMPU or HMPA.     

Catalysis in supercritical CO2 using dendrimer-encapsulated palladium nanoparticles

Dendrimer-encapsulated nanoparticles are shown to be versatile catalysts for both the hydrogenation of styrene and Heck heterocoupling of iodobenzene and methacrylate in supercritical CO2 (scCO2).