Regioselective Cu(I)-catalyzed tandem A3-coupling/decarboxylative coupling to 3-amino-1,4-enynes

An efficient and novel copper-mediated protocol for the synthesis of 3-amino-1,4-enynes from glyoxylic acid, an amine, and an alkyne was developed. This new reaction involving two sequential C-C bond formations is air and moisture tolerant and proceeds via a tandem A(3)-coupling and a selective decarboxylative coupling.     

Green synthesis of quinolines via A3-coupling by using graphene oxide-supported Brønsted acidic ionic liquid

Research on Chemical Intermediates - Graphene oxide-supported Bronsted acidic ionic liquid ([GrBenzImi]SO3H) has been prepared by covalent grafting of benzimidazole unit in the matrix of graphene...     

1D Fe_3O_4@CuSiO_3 composites catalyzed decarboxylative A~3-coupling for propargylamine synthesis

Highly active and stable magnetic copper catalysts were successfully achieved by magnetic induced Stober method and subsequent hydrothermal reaction with copper ions in alkaline condition.The high content of Cu~(2+) as well as the unique structures of hierarchical copper silicate in the as-prepared catalysts endowed their outstanding catalytic performance.Efficient decarboxylative A~3-coupling of a-keto acid,amine and alkyne was realized with the low Fe_3 O_4@CuSiO_3 loading.A range of propargylamines were produced in good to excellent yields under solvent-free condition.Moreover,the catalyst can be easily separated from the final organic product with an external magnet.Also,this kind of catalyst could be recycled up to six times while maintaining its activity.     

Ag2CO3-catalyzed efficient synthesis of internal or terminal propargylicamines and chalcones via A3-coupling under solvent-free condition

Several simple, fast and practical protocols have been developed to synthesize internal or terminal propargylamines and chalcones via A³-coupling reaction of aldehydes, amines, and alkynes catalyzed by an easily available catalyst Ag₂CO₃ under solvent-free condition. The reaction proceeded smoothly to deliver various products in good-to-excellent yields with good functional group tolerance. Gram-scale preparation, bioactive molecule synthesis and asymmetric substrates have been demonstrated. Furthermore, plausible mechanisms for the synthesis of different products have been proposed.     

A growth walk model for estimating the canonical partition function of interacting self-avoiding walk

We have explained in detail why the canonical partition function of interacting self-avoiding walk (ISAW) is exactly equivalent to the configurational average of the weights associated with growth walks, such as the interacting growth walk (IGW), if the average is taken over the entire genealogical tree of the walk. In this context, we have shown that it is not always possible to factor the density of states out of the canonical partition function if the local growth rule is temperature dependent. We have presented Monte Carlo results for IGWs on a diamond lattice in order to demonstrate that the actual set of IGW configurations available for study is temperature dependent even though the weighted averages lead to the expected thermodynamic behavior of ISAW.     

Thioether-based copper(I) Schiff base complex as a catalyst for a direct and asymmetric A3-coupling reaction

A novel thiosalen ligand based on a thioether has been prepared and readily coordinated with copper(I) salts (CuCl, CuBr, CuI, and CuCN). The new organometallic catalyst was used for the direct and enantioselective alkynylations of imines in an A³-coupling reaction. In this reaction, the corresponding propargylamines were obtained as single products in excellent yields and with good enantioselectivities.     

Single and double A3-coupling (aldehyde-amine-alkyne) reaction catalyzed by an air stable copper(I)-phosphole complex

An air stable copper(I)-phosphole complex, [CuCl{2,5-bis(2-thienyl)-1-phenylphosphole}₂] (1), was utilized as a catalyst in single and double A³-coupling reactions for preparing mono- and bi-propargylamines. A variety of aldehydes, amines and terminal alkynes were tested. Most of these reactions led to formation of the expected propargylamines in good yields using low amounts catalyst and obviating both the use of purified reagents as employ of a glovebox.     

New 1,2-dithioether based 2D copper(I) coordination polymer: from synthesis to catalytic application in A3-coupling reaction

Abstract

A new 2D copper(I) coordination polymeric complex has been synthesized from CuI and 1-(1-{4-chlorophenylthio}propan-2-ylthio)-4-chlorobenzene ([(CuI)₂{ArSCH₂CH(CH₃)SAr}₂]_n, Ar = 4-ClC₆H₄) and characterized by high resolution mass spectrometry (HRMS) and single crystal X-ray diffraction techniques. The complex has been employed as a suitable catalyst for a solvent-free, one-pot, three-component A³-coupling reaction. A variety of aromatic and aliphatic aldehydes, terminal alkynes and aliphatic cyclic secondary amines have been used to prepare a library of propargylamines using the 2D-Cu complex at significantly low concentration (0.2?mol%).     

A mathematical theory of the random walk model in chromatography

An exact mathematical treatment of the random walk model in chromatography is given in this paper. Various factors which can cause broadening of peaks, such as equilibium fluctuation, diffusion, size and structure of fixed phase particles, fluid velocity, flow around the particles, distribution ratio, column temperature and nonuniformity, etc., are all considered with a unified theory. Formulas of mean retention time and height of theoretical plate, containing all of the factors, are presented.     

A random walk through the dynamics of homogeneous vapor-liquid nucleation

A method of calculating rates of homogeneous vapor-liquid nucleation based on Langevin dynamics of a few relevant degrees of freedom on a free-energy surface is proposed. The surface is obtained here from simulation and from a semi empirical expression. The mass and friction coefficients are derived from atomistic umbrella-sampling molecular-dynamics simulations. The calculated nucleation rate agrees with atomistic simulations for one particular state point of the Lennard-Jones fluid. The present method is about four orders of magnitude more computationally efficient than the direct atomistic simulation of the transmission coefficient.     

Silver chloride supported on Vitamin B1 -Organometallic magnetic catalyst: synthesis,density functional theory study and application in A3-coupling reactions

A highly efficient Fe₃O₄@VitB₁–Ag(I) magnetic catalyst has been obtained using surface modification of Fe₃O₄. To this end, silver chloride was immobilized on Fe₃O₄ nanoparticles via vitamin B₁ biomolecules. The synthesized biocompatible magnetic catalyst was applied in an A³-coupling reaction in the presence of aldehyde, amine and phenyl acetylene under solvent-free conditions and afforded the desired products in excellent yields. Also, interactions between metal and ligand in the Fe₃O₄@VitB₁–Ag(I) were studied using theoretical calculations.     

A random walk simulation of flow injection analysis

Dispersion and chemical reaction in a single-channel flow-injection system are modelled by a random walk (stochastic, Markovian chain) method using a microcomputer. The effects of various simulated physical variables are investigated. The model provides valuable insight into the mixing process in flow injection analysis.     

A comparison between the bond-strength-coordination number fluctuation model and the random walk model of viscosity

We have studied the temperature dependence of the viscosity of some polymeric materials by using both, the bond-strength-coordination number fluctuation model and the random walk model. The results reveal that both models show an excellent agreement with the experimental data. For the random walk model, two equations corresponding to two temperature regimes (low-T and high-T) separated by the critical temperature T _c, which is difficult to determine, are needed to describe the temperature dependence of the viscosity of a fragile system, whereas for the bond-strength-coordination number fluctuation model, a single equation with clear physical meaning describes the temperature dependence of the viscosity of both, the fragile and strong systems. We have also studied the relationship between the normalized temperature range of cooperativity and the fragility index. A theoretical expression for the relationship has been derived based on the bond-strength-coordination number fluctuation model. The comparison with the experimental data shows a good agreement, leading to the conclusion that the kinetic properties of glass forming liquids and the cooperativity of molecular relaxations are correlated.     

Growing self avoiding walk trees

The Growing self avoiding walk model (GSAW) was proposed to explain statistical mechanics of the growth process in polymerization. Close examination of the model reveals that it is suited only for addition polymerization where only one monomer unit is added to the growing polymer chain. In this paper we propose a model for step growth or condensation polymerisation, where all of the monomer is converted first to dimer, all dimers are converted to tetramer etc. In the calculation of probabilities of the walker taking a step in a specified direction in the GSAW model the probability is the reciprocal of the number of steps available if the walker looks one step ahead. It is seen that our model for condensation polymerization GSAW can be generalized to the walker looking a finite number of steps ahead (instead of one only) for the purpose of calculation of probabilities. This is explained in detail in the first section of the paper. In the second section of the paper we explain the use of the Depth first search (DFS) algorithm in the calculation of probabilities and moments for the generalized growing self avoiding walk model. In the third section of the paper we report the exact values of the mean square end to end distances and relevant survival probabilities for the model. When GSAW was first proposed there was a controversy over whether it belonged to the same universality class as the True self avoiding walk $\left( \upsilon =\frac{2}{d+1}\right) $ or that of the self avoiding walk $\left( \upsilon =\frac{3}{d+2}\right) $ . At that time it was conclusively shown that the GSAW model cannot belong to the same universality class as the true self avoiding walk model. However it was never conclusively shown that $\upsilon =\frac{3}{d+2}$ for GSAW. In this paper we propose two methods of studying this problem. One method is rigorous analysis of the DFS algorithm. We explain how this algorithm can be used to study restricted random walks with finite memory and self avoiding walks. The second method proposed by us is a detailed analysis of the generalised GSAW model proposed by us. This paper is to be viewed as an introductory paper on a new model that should be of interest to both chemists and mathematicians.     

Open access capillary electrophoresis. A walk up capillary electrophoresis service for the synthetic chemist

A capillary electrophoresis (CE) system has been developed to provide routine purity information to support synthetic organic chemists. A single micellar electrokinetic chromatography system that produces good selectivity with short run times was developed. The instrument operating software has been modified to run separations in a custom open access mode. No expert knowledge of CE is required to run separations.     

SmI2-coupling reaction of chiral non-racemic α-bromo-α′-sulfinyl ketones with imines: synthesis of enantiomerically pure 2-methyl-3-amino-1-ol moieties

Chiral non-racemic α-bromo-α′-sulfinyl ketones were shown to react with imines in the presence of SmI₂ to give the corresponding 1,3-aminoketo derivatives with good syn-diastereoselectivity. Further reduction of these adducts either with DIBAL-H only or with DIBAL-H in the presence of Yb(OTf)₃ afforded syn- and anti-2-methyl-3-amino-1-ol moieties, respectively, in good yields and diastereoselectivities.     

Synthesis of symmetric 1,4-diamino-2-butynes via a Cu(I)-catalyzed one-pot A3-coupling/decarboxylative coupling of a propiolic acid, an aldehyde, and an amine

A novel microwave-assisted approach for the one-pot Cu(I)-catalyzed A(3)-coupling/decarboxylative coupling (PA(2)-coupling) of a propiolic acid, an aldehyde, and an amine, resulting in the formation of diversely substituted 1,4-diamino-2-butynes,is described. It is noteworthy that this new multicomponent coupling provides an efficient access to introduce alkyl and aryl group at the 1,4-position of the 1,4-diamino-2-butynes.     

Atomic walk counts of negative order

Atomic walk counts (awc's) of order k (k > or = 1) are the number of all possible walks of length k which start at a specified vertex (atom) i and end at any vertex j separated by m (0 < or = m < or = k) edges from vertex i. The sum of atomic walk counts of order k is the molecular walk count (mwc) of order k. The concept of atomic and molecular walk counts was extended to zero and negative orders by using a backward algorithm based on the usual procedure used to obtain the values of mwc's. The procedure can also be used in cases in which the adjacency matrix A related to the actual structure is singular and therefore A(-1) does not exist. awc's and mwc's of negative order may assume noninteger and even negative values. If matrix A is singular, atomic walk counts of zero order may not be equal to one.