Suppression of the reversible thermal behavior of the layered double hydroxide (LDH) of Mg with Al: stabilization of nanoparticulate oxides

The layered double hydroxide of Mg with Al decomposes below 600 degrees C with the loss of nearly 48% mass, resulting in the formation of an oxide residue having the rock salt structure and nanoparticulate morphology. However, this product reconstructs back into the parent LDH, owing to its compositional and morphological metastability. The oxide can be kinetically stabilized within an amorphous phosphate network built up through an ex situ reaction with a suitable phosphate source such as (NH4)H2PO4. This oxide transforms into a thermodynamically more stable phase with a spinel structure on soaking in an aqueous medium. The oxide residue has a nanoparticulate morphology as revealed by the Scherrer broadening of the Bragg reflections as well as by electron microscopy. This work shows that the hydroxide reconstruction reaction and spinel formation are competing reactions. Suppression of the former catalyzes spinel formation as the excess free energy of the metastable oxide residue is unlocked to promote the diffusion of Mg2+ ions from octahedral to tetrahedral sites, which is the essential precondition to the formation of a normal spinel. This reaction taking place as it does at ambient temperature and in solution helps in the retention of a nanostructured morphology for the spinel. Another way of stabilizing the oxide is by incorporating the thermally stable borate anion into the LDH. This paves the way for an in situ reaction between the cations of the host LDH and the borate guest. The in situ reaction directly leads to the formation of an oxide with a spinel structure.     

InCl3 catalyzed C-C coupling of aryl alcohols and TosMIC

The InCl₃ mediated C-C coupling reaction between aryl alcohols and TosMIC gives the corresponding amides in good to high yields.     

A new synthetic route to oxazole and pyrrole 2-deoxy-C-ribosides

The synthesis of oxazole and pyrrole 3-carbethoxy/3-arylsulfonyl d and l-2-deoxyribosides by TosMIC addition/cyclization on d and l-2-deoxyribo-1-carboxaldehyde and unsaturated esters in moderate to good yields is reported.     

Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids (−)-halosaline and (−)-8-epi-halosaline via iterative asymmetric allylation/RCM strategy

Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids, (?)-halosaline and (?)-8-epi-halosaline is reported from n-butyraldehyde using iterative asymmetric allylation, nucleophilic substitution with an azide and ring-closing metathesis as the key reactions.     

A validated rapid stability-indicating method for the determination of related substances in solifenacin succinate by ultra-fast liquid chromatography

A rapid, sensitive, and accurate ultra-fast liquid chromatographic method is developed for the determination of related substances and degradants of Solifenacin Succinate, an active pharmaceutical ingredient used in the treatment of overactive bladder. Chromatographic separation of Solifenacin Succinate, its related substances, and degradants was achieved using a Shimpack XR-ODS-II column and mobile phase system containing 10 mM potassium dihydrogen orthophosphate in water. The pH of the buffer was adjusted to 7.0 using triethyl amine (mobile phase A). LC-grade acetonitrile was used as mobile phase B, employing a binary-gradient program at a flow rate 0.5 mL/min. The resolution between the critical pair of peaks (Impurity A and analyte) was found to be greater than 3.5. The limits of detection and quantification (LOQ) of Impurity A, Impurity B, and the analyte were 0.2 and 0.6 μg/mL, respectively for a 5-μL injection volume. The percentage recovery of impurities in the presence of sample matrix ranged from 95 to 104 w/w. The test solution and mobile phase was observed to be stable up to 24 h after the preparation. The validated method yielded good results of precision, linearity, accuracy, robustness, and ruggedness. The proposed method is found to be rapid, accurate, and suitable for the quantitative determination of related substances and degradants during quality control of Solifenacin Succinate active pharmaceutical ingredient.     

A minimalist NMR approach for the structural revision of mucoxin

In an attempt to revise the structural assignment of mucoxin, and faced with 64 diastereomeric possibilities, we resorted to the synthesis of truncated structures that contained the core stereochemical sites. Twelve stereochemical analogues were synthesized, their (1)H and (13)C NMR spectra were analyzed and four recurring stereochemical trends were distilled from the data. Applying the observed trends to the diastereomeric population pared the possible choices for the correct structure of mucoxin from 64 to 4. Synthesis of these analogues led to the identification of the correct structure of mucoxin.     

Molecular structure of thiocyanatotris (2,2′-iminodiethanoldithiocarbamato) tellurium(IV) monohydrate

The synthesis, properties, and structural characterization of the title compound, C₁₆H₃₀N₄O₄S₇Te(IV)·H₂O, are reported. The crystals are monoclinic, space groupP2₁/n, withZ=4 in a unit cell of dimensionsa=13.291(5),b=21.306(6),c=10.450(1) Å, 0=104.25(2)° and,V _c=2868 ų. The structure was solved by the heavy atom method and refined by full-matrix least squares toR=0.025 andR _w =0.027 for 2894 reflections. The dithiocarbamate groups are linked in an unequal bidentate manner with Te-S average distance 2.695(1) Å. The thiocyanate group is bonded through the sulfur atom with much larger Te-S length [2.964(2) Å].     

Equivalences for blocks of the Weyl groups

We describe the source algebras of the blocks of the Weyl groups of type B and type D in terms of the source algebras of the blocks of the symmetric groups. As a consequence, we show that Puig's conjecture on the finiteness of the number of isomorphism classes of source algebras for blocks of finite groups with a fixed defect group holds for these classes of groups. We also show how certain isomorphisms between subalgebras of block algebras of the symmetric groups can be lifted to block algebras of the Weyl groups of type B.