Iodine-catalyzed cycloalkenylation of dihydroquinolines and arylamines through a reaction with cyclic ketones under neat conditions

An iodine-catalyzed direct cycloalkenylation of dihydroquinolines and arylamines has been developed. This method consists of a Friedel–Crafts reaction between dihydroquinolines (or arylamines) and cyclic ketones in which the double bond is selectively generated throughout the course of the reaction resulting in a direct cycloalkenylation, under neat conditions.     

Mass Spectral Analyses of Trimethylsilyl Glucuronic Acids

Mass spectral analysis of carbohydrates has become an important tool for the biological chemist^1–3 and the use of mass spectrometers interfaced with gas-liquid chromatographs has provided a convenient method of study for volatile derivatives of carbohydrates. Several groups^4–7 have accomplished separations of the various isomeric trimethylsilyl (TMSi) esters and ethers of the glucuronic acids. The present work utilizes a gas-liquid chromatograph-mass spectrometer to examine the previously unreported mass spectra of pertrimethylsilylated glucuronic acids and these spectra are compared to the previously reported⁸ spectra of the pemethylated glucuronic acids.     

Geographical influences of an emerging network of gang rivalries

We propose an agent-based model to simulate the creation of street gang rivalries. The movement dynamics of agents are coupled to an evolving network of gang rivalries, which is determined by previous interactions among agents in the system. Basic gang data, geographic information, and behavioral dynamics suggested by the criminology literature are integrated into the model. The major highways, rivers, and the locations of gangs’ centers of activity influence the agents’ motion. We use a policing division of the Los Angeles Police Department as a case study to test our model. We apply common metrics from graph theory to analyze our model, comparing networks produced by our simulations and an instance of a Geographical Threshold Graph to the existing network from the criminology literature.     

Iridium-Catalyzed Formyl-Selective Deuteration of Aldehydes

We report the first direct catalytic method for formyl-selective deuterium labeling of aromatic aldehydes under mild conditions, using an iridium-based catalyst designed to favor formyl over aromatic C−H activation. A good range of aromatic aldehydes is selectively labeled, and a one-pot labeling/olefination method is also described. Computational studies support kinetic product control over competing aromatic labeling and decarbonylation pathways.     

Halogenation of 2-Hydroxynicotinic Acid

A convenient method to prepare 5-halo-2-hydroxy-nicotinic acid is described.     

Chromium(V) Oxide Trichloride,and some Pentachlorido‐­oxido‐chromate(V) Salts: Structures and Spectroscopic ­Characterization

Crystalline CrOCl₃ contains [Cl₂OCr(μ‐Cl)₂CrOCl₂] molecules with two square pyramidal CrOCl₄ units sharing a common edge and with the Cr–O arranged anti, a new structure type for transition metal MOX₃ compounds. Crystals are monoclinic with space group P2₁/c, Z = 4, with a = 5.735(5), b = 13.738(7), c = 11.318(4) Å, α = 90°, β = 98.346(6)°, γ = 90°. Its IR and UV/Vis spectra are reported and compared with those of the C_3v monomer found in the gas phase. Structures are also reported for M₂[CrOCl₅] (M = Cs or Rb) and show a pseudo‐octahedral anion. Cs₂[CrOCl₅] adopts a K₂PtCl₆‐type structure with [CrOCl₅]^2– ions randomly orientated, but Rb₂[CrOCl₅] is orthorhombic with space group Pnma with a = 13.6471(7), b = 9.9175(5), and c = 6.9562(4) Å. Rietveld refinement of the data on the rubidium salt gave Cr–O = 1.628(1), Cr–Cl_transO = 2.652(7), Cr–Cl_transCl = 2.239(8)–2.342(3) Å. Corresponding Cr^V oxide bromide species do not form.     

Diagnosis of suspicious breast lesions using an empirical mathematical model for dynamic contrast-enhanced MRI

The purpose of this study was to test whether an empirical mathematical model (EMM) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can distinguish between benign and malignant breast lesions. A modified clinical protocol was used to improve the sampling of contrast medium uptake and washout. T(1)-weighted DCE magnetic resonance images were acquired at 1.5 T for 22 patients before and after injection of Gd-DTPA. Contrast medium concentration as a function of time was calculated over a small region of interest containing the most rapidly enhancing pixels. Then the curves were fitted with the EMM, which accurately described contrast agent uptake and washout. Results demonstrate that benign lesions had uptake (P<2.0 x 10(-5)) and washout (P<.01) rates of contrast agent significantly slower than those of malignant lesions. In addition, secondary diagnostic parameters, such as time to peak of enhancement, enhancement slope at the peak and curvature at the peak of enhancement, were derived mathematically from the EMM and expressed in terms of primary parameters. These diagnostic parameters also effectively differentiated benign from malignant lesions (P<.03). Conventional analysis of contrast medium dynamics, using a subjective classification of contrast medium kinetics in lesions as "washout," "plateau" or "persistent" (sensitivity=83%, specificity=50% and diagnostic accuracy=72%), was less effective than the EMM (sensitivity=100%, specificity=83% and diagnostic accuracy=94%) for the separation of benign and malignant lesions. In summary, the present research suggests that the EMM is a promising alternative method for evaluating DCE-MRI data with improved diagnostic accuracy.     

Stereoselective Remote Functionalization via Palladium-Catalyzed Redox-Relay Heck Methodologies

Exploration of novel, three-dimensional chemical space is of growing interest in the drug discovery community and with this comes the challenge for synthetic chemists to devise new stereoselective methods to introduce chirality in a rapid and efficient manner. This Minireview provides a timely summary of the development of palladium-catalyzed asymmetric redox-relay Heck-type processes. These reactions represent an important class of transformation for the selective introduction of remote stereocenters, and have risen to prominence over the past decade. Within this Minireview, the vast scope of these transformations will be showcased, alongside applications to pharmaceutically relevant chiral building blocks and drug substances. To complement this overview, a mechanistic summary and discussion of the current limitations of the transformation are presented, followed by an outlook on future areas of investigation.     

The Origin of Shape Sensitivity in Palladium‐Catalyzed Suzuki–Miyaura Cross Coupling Reactions

The shape sensitivity of Pd catalysts in Suzuki–Miyaura coupling reactions is studied using nanocrystals enclosed by well‐defined surface facets. The catalytic performance of Pd nanocrystals with cubic, cuboctahedral and octahedral morphologies are compared. Superior catalytic reactivity is observed for Pd NCs with {100} surface facets compared to {111} facets. The origin of the enhanced reactivity associated with a cubic morphology is related to the leaching susceptibility of the nanocrystals. Molecular oxygen plays a key role in facilitating the leaching of Pd atoms from the surface of the nanocrystals. The interaction of O₂ with Pd is itself facet‐dependent, which in turn gives rise to more efficient leaching from {100} facets, compared to {111} facets under the reaction conditions.