A stereoselective approach to γ-functionalized carbonyls exploiting the Cu-promoted S(N)2' reaction

While several efficient processes exist to effect the stereoselective creation of carbon-carbon bonds in the α- and β-position of carbonyls, functionalization of the γ-position is much more challenging. We disclose an alternative methodology exploiting the Cu-promoted S(N)2' reaction to achieve the addition of various nucleophiles upon the allylic lactones 5a-d which lead to the generation of the desired γ-functionalized α,β-unsaturated aldehydes 6 following in situ hydrolysis.     

Fullerol cluster formation in aqueous solutions: implications for environmental release

Here we report on the characteristics of fullerol in aqueous systems and examine those conditions that affect the physical state of fullerol in water. When dispersed in water fullerol forms polydisperse suspensions characterized by both small ( approximately 100 nm) and large associations (>500 nm). These clusters are charged with a point of zero net proton charge (PZNPC) of approximately pH 3. Though the size of fullerol clusters may be manipulated through changes in solution chemistry, principally pH, cluster formation cannot be entirely prevented through these means alone. The fullerol cluster structure is amorphous as revealed by X-ray diffraction analysis, which is in contrast to clusters of C(60) formed through dissolution in toluene and then introduced into water through sonication (SONnC(60)). The SONnC(60) clusters are crystalline with a structure similar to that of unreacted C(60) crystals.     

Mapping Antiretroviral Drugs in Tissue by IR-MALDESI MSI Coupled to the Q Exactive and Comparison with LC-MS/MS SRM Assay

This work describes the coupling of the IR-MALDESI imaging source with the Q Exactive mass spectrometer. IR-MALDESI MSI was used to elucidate the spatial distribution of several HIV drugs in cervical tissues that had been incubated in either a low or high concentration. Serial sections of those analyzed by IR-MALDESI MSI were homogenized and analyzed by LC-MS/MS to quantify the amount of each drug present in the tissue. By comparing the two techniques, an agreement between the average intensities from the imaging experiment and the absolute quantities for each drug was observed. This correlation between these two techniques serves as a prerequisite to quantitative IR-MALDESI MSI. In addition, a targeted MS² imaging experiment was also conducted to demonstrate the capabilities of the Q Exactive and to highlight the added selectivity that can be obtained with SRM or MRM imaging experiments. Fig. a

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Large-scale computational fluid dynamics by the finite element method

Solution methods are presented for the large systems of linear equations resulting from the implicit, coupled solution of the Navier-Stokes equations in three dimensions. Two classes of methods for such solution have been studied: direct and iterative methods. For direct methods, sparse matrix algorithms have been investigated and a Gauss elimination, optimized for vector-parallel processing, has been developed. Sparse matrix results indicate that reordering algorithms deteriorate for rectangular, i.e. M × M × N, grids in three dimensions as N gets larger than M. A new local nested dissection reordering scheme that does not suffer from these difficulties, at least in two dimensions, is presented. The vector-parallel Gauss elimination is very efficient for processing on today's supercomputers, achieving execution rates exceeding 2.3 Gflops the Cray YMP-8 and 9.2 Gflops on the NEC on SX3. For iterative methods, two approaches are developed. First, conjugate-gradient-like methods are studied and good results are achieved with a preconditioned conjugate gradient squared algorithm. Convergence of such a method being sensitive to the preconditioning, a hybrid viscosity method is adopted whereby the preconditioner has an artificial viscosity that is gradually lowered, but frozen at a level higher than the dissipation introduced in the physical equations. The second approach is a domain decomposition one in which overlapping domain and side-by-side methods are tested. For the latter, a Lagrange multiplier technique achieves reasonable rates of convergence.     

Current technologies for analysis of biomass thermochemical processing: A review

Pyrolysis and gasification are two of the more promising utilization methods for the conversion of biomass toward a clean fuel source. To truly understand and model these processes requires detailed knowledge ranging from structural information of raw biomass, elemental composition, gas-phase reaction kinetics and mechanisms, and product distributions (both desired and undesired). The various analytical methods of biomass pyrolysis/gasification processing are discussed, including reactor types, analytical tools, and recent examples in the areas of (a) compositional analysis, (b) structural analysis, (c) reaction mechanisms, and (d) kinetic studies on biomass thermochemical processing.     

Practical asymmetric synthesis of a potent Cathepsin K inhibitor. Efficient palladium removal following Suzuki coupling

A large-scale, chromatography-free synthesis of a potent and selective Cathepsin K inhibitor 1 is reported. The key asymmetric center was installed by addition of (R)-pantolactone to the in situ-generated ketene 4a. The final step of the convergent synthesis of 1 was completed via Suzuki coupling of aryl bromide 7a with unprotected aryl piperazine boronic acid 13. Residual palladium and iron generated in the Suzuki coupling were efficiently removed from crude 1 via a simple extractive workup using lactic acid.     

First example of direct reductive amination of aldehydes with primary and secondary amines catalyzed by water-soluble transition metal catalysts

An unprecedented efficient and highly selective direct reductive amination of aldehydes with primary and secondary amines in water using gaseous hydrogen and water-soluble catalysts is developed. The catalytic system formed in situ from Pd(PhCN)₂Cl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), allows full conversion of aldehydes and the formation of desired alkylated amines with excellent yields and selectivities. The catalytic system is stable and can be recycled and reused three times without loss of activity.     

Synthesis of 3,3-disubstituted oxindoles

A novel and efficient two-step synthetic sequence for the preparation of 3,3-disubstituted oxindoles was developed starting from arylhydrazines and α-branched aldehydes via Fischer indole type synthesis followed by imine oxidation.     

Chemoselective hydrogenation of nitriles to primary amines catalyzed by water‐soluble transition metal catalysts

The water‐soluble rhodium complex generated in situ from [Rh (COD)Cl]₂ in aqueous ammonia has been revealed as a highly efficient catalyst for the hydrogenation of aromatic nitriles, to primary amines with excellent yields. The catalyst is also highly selective towards primary amines in the case of sterically hindered aliphatic nitriles. The catalytic system can also be recycled and re‐used with no significant loss of activity.