Transition metal free large-scale synthesis of aromatic vinyl chlorides from aromatic vinyl carboxylic acids using bleach

While continuing our research on Hunsdiecker reaction, we came across an interesting application of bleach, sodium hypochlorite (NaOCl) for decarboxylative chlorination reaction. The reaction is easily scaled up to 10?mmol. The reaction has good tolerance towards wide variety of functional groups. The reaction has mild conditions and gave relatively high chemical yield of the desired product.     

Solvent‐Driven Conformational Exchange for Amide‐Linked Bichromophoric BODIPY Derivatives

The fluorescence lifetime and quantum yield are seen to depend in an unexpected manner on the nature of the solvent for a pair of tripartite molecules composed of two identical boron dipyrromethene (BODIPY) residues attached to a 1,10‐phenanthroline core. A key feature of these molecular architectures concerns the presence of an amide linkage that connects the BODIPY dye to the heterocyclic platform. The secondary amide derivative is more sensitive to environmental change than is the corresponding tertiary amide. In general, increasing solvent polarity, as measured by the static dielectric constant, above a critical threshold tends to reduce fluorescence but certain hydrogen bond accepting solvents exhibit anomolous behaviour. Fluorescence quenching is believed to arise from light‐induced charge transfer between the two BODIPY dyes, but thermodynamic arguments alone do not explain the experimental findings. Molecular modelling is used to argue that the conformation changes in strongly polar media in such a way as to facilitate improved rates of light‐induced charge transfer. These solvent‐induced changes, however, differ remarkably for the two types of amide.     

The Use of Pinner Type Reaction for the Synthesis of New Indeno[2,1‐c]pyridine‐4‐carbonitrile Derivatives

An efficient and convenient route was developed for the synthesis of new pyridinecarbonitrile derivatives by using the Pinner type of reaction. The 2‐((E)‐2‐((dimethylamino)methylene)‐1,2‐dihydro‐5,6‐dimethoxyinden‐3‐ylidene) malononitrile 2 was reacted in the presence of dry HCl gas to yield 3‐chloro‐6,7‐dimethoxy‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitrile ( 3 ) in good yield. The S_NAr reaction on compound 3 with various nucleophiles yielded 3‐substituted pyridinecarbonitriles 4 , 5 , 6 , 7 , 8 , 9 in moderate to good yield.     

新的聚苯乙烯负载锌化合物:高效苯酚氧化催化剂(英文)

The novel recyclable free –ONNO– tetradentate Schiff base ligand N,N′‐bis(2‐hydroxy‐3‐ methox‐ybenzaldehyde)4‐methylbenzene‐1,2‐diamine (3‐MOBdMBn) was synthesized. Complexation of this ligand with zinc(3‐MOBdMBn‐Zn) was performed, and the catalytic activity of the complex was evaluated. The polymer‐supported analog of this complex(P‐3‐MOBdMBn‐Zn) was synthesized, and its catalytic activity was studied. These free and polymer‐anchored zinc complexes were prepared by the reactions of metal solutions with one molar equivalent of unsupported 3‐MOBdMBn or P‐3‐MOBdMBn in methanol under nitrogen. The catalytic activity of 3‐MOBdMBn‐Zn and P‐3‐MOBdMBn‐Zn was evaluated in phenol oxidation. The activity of P‐3‐MOBdMBn‐Zn was signif‐icantly affected by the polymer support, and the rate of phenol conversion was around 50% for polystyrene‐supported 3‐MOBdMBn. The experimental results indicated that the reaction rate was affected by the polymer support, and the rate of phenol conversion was 1.64 μmol/(L·s) in the presence of polystyrene‐supported 3‐MOBdMBn.     

Interfacial polycondensation—Modeling of kinetics and film properties

Interfacial polycondensation (IP) is an important technique used in the encapsulation of a variety of active ingredients and synthesis of thin film composite membranes. The present work seeks to advance our understanding of the mechanisms underlying the reaction, phase separation and film formation in this process, and hence, of how the film properties are influenced by preparation conditions. The model presented here incorporates all the essential physicochemical processes at a fundamental level through simple phenomenologies: ionic equilibria in the aqueous phase, resistances due to external mass transfer, diffusion through polymer film, interfacial reaction, thermodynamics of phase separation, and formation of a coherent film. The model has been tested against the data previously communicated [S.J. Wagh, Studies in interfacial polycondensation. Ph.D. Thesis. IIT Bombay, 2004; S.J. Wagh, S.S. Dhumal, A.K. Suresh, An experimental study of polyurea membrane formation by interfacial polycondensation, Journal of Membrane Science, submitted for publication] on polyurea microcapsules. The influence of the model parameters and preparation conditions, on the properties of the polymer and film and their development during reaction, have been studied. The study provides important insights into the process and should help in designing synthesis methodologies to suit the application.     

Rational approximant pentagonal crystals based on icosa-hedral structures

The generation of periodic quasicrystals by the projection method is considered. The effects of the simulteneous distortion of the projected icosahedron and 6D hyperlattice are presented.     

Diversity oriented synthesis of pyran based polyfunctional stereogenic macrocyles and their conformational studies

A new approach to synthesize a homologous series of 14-, 15-, and 16-membered drug-like, macrocyclic glycoconjugates involving TBAHS promoted azide-propenone intramolecular cycloaddition in designed C-glycopyranosyl butenones from a simple sugar d-glucose and d-mannose is reported.     

Integrators for stiff systems with undamped oscillatory solutions

In this paper, we discuss various A-stable integration methods for stiff ordinary differential equations, suitable for general purpose circuit simulations and device simulation. We point out that some of the popular methods either introduce excessive amounts of numerical damping when applied to a loss-less resonance circuit or fail to sufficiently damp rapidly delaying stiff modes. Furthermore, some of these methods can become unstable when applied with variable steps to stable problems with variable coefficients. Some recently discovered integrators, on the other hand, simultaneously combine the advantages and avoid the disadvantages of the former methods. Furthermore, if implemented properly, these latter methods retain their A-stability when applied with variable steps to the stable variable coefficient test equation.     

Diffraction From 1D quasicrystals

Levine and Steinhardt's expression is generalised for the structure factor of a binary quasicrystal with AτB composition. The atomic model used in this generalisation is based on the embedding of quasiperiodic chains of A and B atoms such that there is a B atom within every long interval of the A-chain. For the proposed embedding scheme, the range of interpenetration length as well as the ratio of long and short intervals in the two chains are shown to affect the diffracted intensities drastically. The effect of order-disorder on the motif, average quasilattice constant and diffracted intensities is also considered. Conditions for the composite chain to become self-similar, which for the most general embedding is not necessary, are obtained. The application of present decoration scheme to vacancy ordered phases is discussed.