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An efficient and general copper(I)-catalyzed silylation of p-quinone-methides is described. Non-symmetric dibenzylic silanes are obtained in high yields under mild reaction conditions. These compounds can be used as bench-stable benzylic carbanion precursors.

We present new facts about polymorphism based on (i) crystallographic data from the Cambridge Structural Database (CSD, a database built over 50 years of community effort), (ii) 229 solid form screens conducted at Hoffmann-La Roche and Eli Lilly and Company over the course of 8+ and 15+ years respectively and (iii) a dataset of 446 polymorphic crystals with energies and properties computed with modern DFT-d methods. We found that molecular flexibility or size has no correlation with the ability of a compound to be polymorphic. Chiral molecules, however, were found to be less prone to polymorphism than their achiral counterparts and compounds able to hydrogen bond exhibit only a slightly higher propensity to polymorphism than those which do not. Whilst the energy difference between polymorphs is usually less than 1 kcal mol(-1), conformational polymorphs are capable of differing by larger values (up to 2.5 kcal mol(-1) in our dataset). As overall statistics, we found that one in three compounds in the CSD are polymorphic whilst at least one in two compounds from the Roche and Lilly set display polymorphism with a higher estimate of up to three in four when compounds are screened intensively. Whilst the statistics provide some guidance of expectations, each compound constitutes a new challenge and prediction and realization of targeted polymorphism still remains a holy grail of materials sciences.

and related isoxazolonaphthoquinone (IV) via reaction of 2-acetylnaphthoquinone (I) with hydrazines and hydroxylamine, respectively

The Cu(II)-catalyzed hydro- and carboboration of strained alkenes, such as (I), (IV), and (VI) is reported.

A novel Cu-catalyzed diastereo- and enantioselective desymmetrization of cyclopropenes to afford nonracemic cyclopropylboronates is described. Trapping the cyclopropylcopper intermediate with electrophilic amines allows for the synthesis of cyclopropylaminoboronic esters and demonstrates the potential of the approach for the synthesis of functionalized cyclopropanes.

N,N-Dialkylhydrazones (I) are subjected to a Strecker-type reaction using TmsCN (II) as the cyanide source.

Due to the adverse effects of mercury on human health and the environment, restrictive legislations and world-wide common efforts are now under way to reduce both the supply and demand of mercury. As a result, all excess Hg must be stored in safe conditions in secure places. This paper is an attempt to review the various treatment technologies types of liquid mercury (Hg 0 ) and mercury-containing wastes, which can be used to store these residues in a safe way. The different treatments were classified as a function of the waste treated. The main treatments described are amalgamation, formation of sulfides, thermal treatments, vitrification, soil washing, sulfur polymer stabilization solidification, chemically bonded phosphate ceramics and other encapsulation processes, being highlighted the stabilization/solidification processes that are the treatments that provide better results, according to the consulted bibliography.

The title compound, a phase alteration product of spent nuclear fuel, is characterized by solid state cyclic voltammetry and Raman spectroscopy.

The cross-coupling uses the inexpensive, bench-stable catalyst NiCl2(PCy3)2 to deliver biaryls in good to excellent yield.

The authors have explored the possibilities offered by the modification of thiolato bridges in dinuclear rhodium complexes on the selective hydroformylation of cylic vinyl and allyl ethers. The dinuclear complex [Rh{sub 2}({mu}-S(CH{sub 2}){sub 3}NMe{sub 2}){sub 2}(cod){sub 2}] (cod = 1,5-cyclooctadiene) has been prepared, and its reactivity with CO, phospines, and phosphites has been investigated. The complex crystallizes in the monoclinic space group C2/c with Z = 8, {alpha} = 22.543 (4) A, B = 12.040 (2) A, c = 21.547 (3) A, and {Beta} = 98.77 (1){degrees}. For the determination of the structure 4091 unique reflections were used, and the final refinement gave R = 4.1% and R{sub w} = 4.4%. The molecular structure reveals that the two rhodium atoms are bridged by the two thiolato ligands, and the cyclooctadiene completes the coordination of the metal atoms. The amine groups are not bonded to the rhodium. The dinuclear complex has been used in the hydroformylation of 2,3-di-hydrofuran, 2,5-dihydrofuran, 3,4-dihydro-2H-pyran or 3,6-dihydro-2H-pyran was tetrahydropyran-2-carbaldehyde. A systematic study of the influence of the reaction parameters on the selectivity of the hydroformylation of 2,3-dihydroformylation of 3,4-dihydro-2H-pyran or 3,6-dihydro-2H-pyran was tetrahydropyran-2-carbaldehyde. A systematic study of the influence of the reaction parameters on the selectivitymore » of the hydroformylation of 2,3-dihydrofuran and 2,5-dihydrofuran was undertaken. The study allowed the rationalization of the observed selectivity and the optimization of the yields and regioselectivities. Thus, by modification of the reaction parameters, tetrahydrofuran-3-carbaldehyde was obtained in quantitative yields from 2,5-dihydrofuran and tetrahydrofuran-2-carbaldehyde can be prepared from either 2,3-dihydrofuran or 2,5-dihydrofuran in approximately 75% yield. 33 refs., 3 figs., 9 tabs.« less

4-Alkyldithiocarboxylate-3,5-dihydroxy-1-phenylpyrazoles 2, are prepared in good yield by the reaction of 3-hydroxy-1-phenyl-2-pyrazolin-5-one 1 with sodium acetate in dimethylformamide (DMF), carbon disulfide and alkyl halides.

3-Hydroxy-1-phenyl-2-pyrazolin-5-one 1 reacts with primary, secondary and allylic alcohols under catalytic acidic conditions and in the presence of 3 A molecular sieves, to afford 3-alkoxy-1-phenyl-2-pyrazolin-5-ones 3.

2,4-Pentanedione, ethyl acetoacetate, benzoyl acetate and diethyl malonate 1a-d react with sodium acetate and dimethyl trithiocarbonate in dimethylformamide to afford methyl-β,β′-dicarbonyldithiocarboxylate derivatives 2a-d in moderate yield.

We analyze in this article the evolution of the chemical bonding in group III nitrides (MN, M = Al, Ga, In), from the N−N bond dominated small clusters to the M−N bond dominated crystals, with the aim of explaining how the strong multiple bond of N2 is destabilized with the increase in coordination. The picture that emerges is that of a partially ionic bond in the solid state, which is also present in all the clusters. The covalent N−N bond, however, shows a gradual decrease of its strength due to the charge transfer from the metal atoms. Overall, Al clusters are more ionic than Ga and In clusters, and thus the N−N bond is weakest in them. The nitrogen atom charge is seen to be proportional to the metal coordination, being thus a bond-related property, and dependent on the M−N distance. This explains the behavior observed in previous investigations, and can be used as a guide in predicting the structures and defects on semiconductor quantum dot or thin film devices of these compounds.

Rh(I) and Ir(I) cationic complexes [M(cod)(PP)]BF 4 have been synthesised from diphosphite ligands 4 – 6 derived from ribofuranose. They have been used in the rhodium and iridium catalysed asymmetric hydrogenation of acrylic acid derivatives. Ribose derivative ligands 4 – 6 have also been used as auxiliaries in the Rh-catalysed hydroformylation of styrene. Hydroformylation results have been explained on the basis of the species formed under hydroformylation conditions. Comparative experiments with the related epimer d -(+)-xylose derivatives showed that the configuration of the product is controlled by the absolute configuration of the stereogenic carbon atom C-3.

We have calculated the ground-state geometry, vibrational frequencies, and bonding properties of MgF2 at the Hartree−Fock (HF), second-order (MP2), and fourth-order Moller−Plesset (MP4(SDTQ)) levels of calculation. Several high-quality basis sets have been used, with special attention on the influence of polarization and diffuse functions on the above properties. The best HF and MP2 calculations predict that MgF2 is a linear molecule. MP2 and MP4 results are very similar. The MP2 symmetric (ν1) and asymmetric (ν3) stretching frequencies are about 5−7% smaller than the HF values and agree well with the observed data. The MP2 ν2 (bending) frequency is close to that found in other ab initio calculations and the experimental gas-phase value but is 80 cm-1 smaller than the value observed in the IR spectrum of MgF2 trapped in solid argon. Polarization functions shorten noticeably the magnesium−fluorine equilibrium distance and increase ν1 and ν3. An atoms in molecules (AIM) analysis of the wave functions reveal...

Hartree-Fock (RHF) and second-order Moller-Plesset (MP2) first principles calculations have been performed to study the structures, stabilities, harmonic vibrational frequencies, and bonding properties of MgF 2 dimers and trimers, complementing our previous work (J. Phys. Chem. 2001, 105, 4126) on the MgF2 monomer. The less energetic isomers found for (MgF2)2 and (MgF2)3 are the bridged F-(Mg2F2)- F( D2h) and F-MgF2MgF2Mg- F( D2d) structures, respectively. A new Cs trimer structure has been found and characterized. Correlation energy corrections increase the Mg-F distances by 1.2-1.4% and do not modify appreciably the Mg-F-Mg and F-Mg-F angles. The dissociation energy per MgF2 unit (DE) of (MgF2)n increases with n. MP2 frequencies for the (MgF2)2 D2h isomer are around 1.0% lower than their RHF equivalents. The whole set of computed frequencies for (MgF2)n has allowed us to perform a critical analysis of the experimental vibrational data, where some spectral assignments remained uncertain. The atoms in molecules analysis of the electron density reveals that (MgF2)nclusters are highly ionic, with almost nominal net atomic charges (qMg = +1.8jej and qF = -0.9jej). Our previous polarizable-ions model accounts fairly well for the properties of these clusters, rationalizing the energy ordering of trimers in a physically sound way.

A series of novel phosphite–phosphoroamidite ligands, derived from readily available D-xylose, has been used for the first time in the asymmetric Rh-catalyzed hydrogenation of a series of α,β-unsaturated carboxylic acid derivatives with excellent enantioselectivity (ee up to >99%).

A series of diphosphite ligands 1 – 3 derived from readily available d -(+)-glucose and bisphenol or binaphthol derivatives have been applied as ligands in the Cu-catalyzed 1,4-addition of diethylzinc to cyclohexenone. Excellent reaction rates (TOF>1200 h −1 ) and good enantioselectivities (e.e. of up to 84%) were achieved. The modular nature of these ligands allows easy systematic variation in the configuration of the stereocenters (C(3), C(5)) at the ligand backbone and in the biaryl substituents, so the optimum configuration for maximum enantioselectivity in the asymmetric 1,4-addition can be determined. The results obtained show that the enantioselectivity induced by the ligand depends strongly on the absolute configuration of the C(3) stereogenic centre, while the sense of the enantiodiscrimination is predominantly controlled by the configuration of the biaryl groups of the phosphite moieties.

A series of diphosphite 1–6 and phosphite–phosphoroamidite 7 ligands, derived from inexpensive d -(+)-xylose and d -(+)-glucose, were evaluated in the asymmetric Rh-catalyzed hydrosilylation of different ketones. Systematic variation of the configuration of the stereocenters at the ligand backbone and that of the substituents at the phosphite moiety provide useful information about the ligand parameters that control the enantiodiscrimination.

A series of novel diphosphite ligands derived from readily available d-(+)-glucose have been synthesized. These ligands were screened in the Rh-catalyzed hydrogenation of a series of α,β-unsaturate...

A series of new chelating diphosphite ligands with a furanoside backbone and axially chiral biphenyl or binaphthyl moieties have been synthesized. Their Rh(I) complexes have been tested as catalyst precursors for the asymmetric hydroformylation of styrene. Systematic variation in chirality at both chiral sugar backbone stereocenters (C-3 and C-5) and either the axial chiral biphenyl or binaphthyl substituents revealed a remarkable effect on the selectivity of the hydroformylation catalysts. In this way, by judicious choice of these elements, both regio- and enantioselectivities can be optimized. Thus, both high enantioselectivity (up to 93% S) and regioselectivity in 2-phenylpropanal (up to 98.8%) were found under mild reaction conditions (15–40°C, 10 bar of syngas) for the ligand with a glucofuranoside backbone and bis(trimethylsilyl)-2,2′-biphenyl moiety. The solution structures of HRh(L–L)(CO)2 complexes have been studied by high pressure NMR and IR. Varying the configuration of the binaphthyl moieties revealed a remarkable effect on the diphosphite coordination modes on the intermediate HRh(L–L)(CO)2 species and, therefore, on enantioselectivity. Enantioselectivity was highest for ligands with a strong bis-equatorial coordination preference.

In addition to the total synthesis of the thiomethyl thiazole side chain analogue of epothilone B ( 3 ), a series of related trans -12,13-cyclopropyl epothilone B analogues ( 6 , 8 , 10 , 12 – 14 ) was accomplished. While the synthesis of the epothilone B analogue ( 3 ) proceeded through a Stille coupling of a vinyl iodide substrate containing the epothilone macrocycle with the appropriate side chain stannane, that of the cyclopropyl analogues ( 6 , 8 , 10 , 12 – 14 ) involved a convergent strategy in which a Nozaki–Hiyama–Kishi coupling as a means of introducing the side chains prior to Yamaguchi macrolactonization and final elaboration to the target molecules. The synthesized analogues were subjected to biological evaluation involving in vitro tubulin polymerization, affinity for the microtubule Taxol ® binding site and cell cytotoxicity assays. The results identified the methylthio thiazole side chain as a potency enhancing moiety for the epothilones and shed further light on the structure–activity relationships within this important class of chemotherapeutic agents.

The first Suzuki−Miyaura cross-coupling of an aryl O-carbamate, a versatile and powerful directed metalation group (DMG) in directed ortho metalation (DoM) chemistry, is described using the inexpensive, bench-stable catalyst NiCl2(PCy3)2. Broad synthetic scope and good efficiency are demonstrated for aryl and heteroaryl O-carbamates. The role of water and hydrolysis equilibrium between free boronic acid and boroxine was established to be a crucial parameter for this transformation. When combined with DoM and traditional Pd-catalyzed Suzuki−Miyaura strategies, the methodology offers concise routes to uniquely substituted molecules, avoiding the need for protection/deprotection of the phenol and the use of strongly nucleophilic cross-coupling partners.

Several new 6-(3-pyrazolylpropyl) derivatives of 1,4-naphthohydroquinone-1,4-diacetate (NHQ-DA) have been prepared by chemical modifications of the Diels-Alder adduct of alpha-myrcene and 1,4-benzoquinone. All these new compounds and precursors have been evaluated in vitro for their cytotoxicity against cultured human cancer cells of MB-231 breast-adeno carcinoma, A-549 lung carcinoma, and HT-29 colon carcinoma. GI(50) values ranged in and below the micromolar concentration level.

Several new prenyl-1,2-naphthohydroquinone derivatives have been prepared by chemical modifications of Diels-Alder products which were obtained from cycloaddition of alpha-myrcene to 1,2-benzoquinone and then evaluated in vitro for their cytotoxic activity against A-549 lung carcinoma, HT-29 colon carcinoma, and MB-231 breast adeno-carcinoma culture cells. Most of them exhibited GI50 values in the microM-concentration level.

Arbuscular mycorrhizal (AM) fungi are obligate symbionts that need their plant hosts to complete their life cycle. In the absence of the plant, germlings arrest growth after a few days and retract most of their cytoplasm back into the multinuclear spores. The spores can germinate again during more favorable conditions. How AM fungi recognize compatible host roots and activate their symbiotic program is not yet understood. However, research in this field in the last years has shed light into this topic. We, and others, have approached some of these aspects by studying changes in fungal gene expression observed at early stages of development, before and at the plant recognition stage in an attempt to identify genes and proteins featuring as key regulators in the switch between the asymbiotic and symbiotic style of life. The molecular bases of this recognition process are now starting to be understood and point to common signaling pathways shared with other microbe-plant associations and to arbuscular mycorrhiza specific signaling pathways.

The results of density functional theory based calculations on Ga3O, Ga3O2, Ga3O3, Ga2O3, and GaO3 clusters are reported here. A preference for planar arrangement of the constituent atoms maximizing the ionic interactions is found in the ground state of the clusters considered. The sequential oxidation of the metal-excess clusters increases the binding energy, but the sequential removal of a metal atom from the oxygen-excess clusters decreases the binding energy. The increase in the oxygen to metal ratio in these clusters is accompanied by increase in both electron affinity and ionization potential. The ionization induced structural distortions in the neutral clusters are relatively small, except those for Ga3O2. In anionic (cationic) clusters, the added (ionized) electron is shared by the Ga atoms, except in the case of GaO3. The vibrational frequencies and charge density analysis reveal the importance of the ionic Ga−O bond in stabilizing the gallium oxide clusters considered in this study.