Ion-pair immobilization of l-prolinate anion onto cationic polymer support and a study of its catalytic activity as an efficient heterogeneous catalyst for the synthesis of 2-amino-4H-chromene derivatives

Research on Chemical Intermediates - A novel clean and simple technique for the heterogenization of l-proline organocatalyst has been introduced. This procedure is based on non-covalent...     

离子对负载L-脯氨酸阴离子催化下的不对称Aldol反应

在水相中,通过阴阳离子结合使L-脯氨酸阴离子负载在基于Merrifield树脂的季铵根阳离子上,制备出功能性高分子离子液体.将该体系作为一种高效、可回收的催化剂用于催化醛与酮的不对称Aldol反应.结果表明:该催化体系在微量水中有很好的催化活性和立体选择性,相应的Aldol反应产物获得了6∶94的dr值以及高达98%的ee值,且该催化体系有较好的重复使用性能.     

One-pot solvothermal synthesis of hypercrosslinked porous ionic polymer and its catalytic activity

The hypercrosslinked porous ionic polymer has been synthesized via one-pot polymerization and quaternization of vinyl pyridine and chloromethyl styrene under solvothermal condition. The effects of solvents and synthetic process on the polymer structure were investigated. Polymer from n-butanol showed the highest BET surface area of 555.6 m²/g. The catalytic activities were investigated though the aza-Michael addition and the results showed that the polymer owned even higher activity than homogenous ionic liquid. The high BET surface area, high catalytic activity and high stability made the polymer hold great potential for green chemical processes.     

Facile one-pot synthesis of a photo patternable anthracene polymer

A polycyclic aromatic compound, anthracene, was covalently connected through a methylene bridge via Friedel-Crafts alkylation reaction. Thus, a highly fluorescent anthracene polymer (PMAn) linked by a methylene unit was prepared in one step to produce a conjugated-nonconjugated spacer-type polymer through its reaction with chloromethyl methyl ether (CME) and FeCl₃ at 0 °C. The resultant polymer was soluble in organic solvents and showed significantly higher fluorescence (quantum yield = 0.80) compared to monomeric anthracene, 9-methylanthracene, in chloroform solution. Fluorescent thin films of PMAn as solid media were prepared with high film uniformity. The emission of the film was extinguished when the film was exposed to a UV source, due to the photodimerization of anthracene unit. A fluorescent gap electrode pattern was formed on the polymer film-forming average step depth of 8 nm and 14 nm, after 30 and 60 min irradiation with a UV light, respectively. The photo patternable fluorescent polymer afforded a convenient method of image formation and patterning.     

Two-Step covalent immobilization of enzymes as a way for study of effects influencing catalytic activity

Isothiocyanatopropyl derivatives of trypsin and pepsin obtained by treatment with 3isothiocyanato-1-propyl isocyanate (in the first step) can be covalently bound to carriers having amino groups. Besides all the general principles valid for reactions of isothiocyanates with amines, prerequisite for the satisfactory coupling properties of isothiocyanatopropyl derivatives are (a) a sufficiently high modification degree with isothiocyanate, and (b) a concentration excess of NH₂ carrier groups. With respect to the coupling properties, nonspecific sorptions and the catalytic properties of the immobilized trypsin isothiocyanatopropy l derivatives, the better carrier appears to be the cross-linked polyethy leneimine. Isothiocyanatopropyl, 3-isothiocyanato-bromopropyl, and isothiocyanatopenty l derivatives of leucine, insulin, and albumin also have good coupling properties. The mode in which the amidolytic and caseinolytic activity of isothiocyanatopropyl derivatives of trypsin was influenced after its immobilization on polyethyleneimine clearly indicated that the functional groups of the enzyme did not participate in the coupling to the carrier. Moreover, no intermolecular reactions were observed during the immobilization process. On the other hand, the conformational changes of the protein molecule are important, since they probably influence the changes in the catalytic properties of modified enzymes after their immobilization.     

Novel immobilization method of enzymes using a hydrophilic polymer support

A novel immobilization of an enzyme with a hydrophilic polymer support in organic solvents has been developed utilizing the "polymer-incarcerated (PI) method", which has been used to immobilize metal catalysts; the kinetic resolution of secondary alcohols was found to proceed more smoothly using immobilized lipases (CALB) than free lipases.     

The synthesis of oligodeoxyprimidines on a polymer support

A polymer supported method for synthesizing deoxypolynucleotides is described. Two non-anucleotides were synthesized. Yields exceeding 90% were obtained for each condensation. The time per nucleotide addition was four hours.     

Novel ways of Mn-Salen complex immobilization on modified silica support and their catalytic activity in cyclooctene epoxidation

The covalent immobilization of Mn(III)-Salen complexes on an amorphous mesoporous silica support is reported. Both (3-aminopropyl)trimethoxysilane (APTMS) and (3-iodopropyl)trimethoxysilane (IPTMS) were used in a post-synthesis grafting method to prepare organosilane-modified porous materials. Peptide and ester interactions were employed to anchor the Salen complex to the silica framework. The catalytic activity of the immobilized Salen catalyst was studied by epoxidation of cyclooctene. The comparison of the homogeneous and the immobilized catalyst shows that there was no significant loss of catalytic activity for epoxidation by immobilization. In the current study, the effects of reaction temperatures, solvents, and amount of catalyst on the catalytic activity were investigated. The optimal yield of cyclooctene oxide was obtained at 45°C using toluene as the solvent. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 1, pp. 185–191. This article was submitted by the authors in English.     

Controllable immobilization of polyacrylamide onto glass slide: synthesis and characterization

A novel route was introduced to synthesize dense polyacrylamide (PAM) onto the glass slide surface. To investigate the surface chemistry of the PAM on the glass slides, X-ray photoelectron spectroscopy (XPS) was utilized to obtain detailed chemical state information on the PAM layer constituents. The XPS peak data were consistent with the presented model of the PAM on the glass slide surface. Scanning electron microscopy and atomic force microscope data indicated the presence of PAM on the glass slides, which consist of nodules. The results showed that PAM was successfully immobilized onto glass slides with a two-tier structure under aqueous condition and a monolayer structure under anhydrous condition. Compared with those under aqueous condition, the controllability of the molecular layer on glass slides and the reproducibility under anhydrous condition were much better, which makes anhydrous condition an advisable condition for the study of the reaction mechanisms of glass slides modified by PAM.     

High-yield immobilization of a puromycin analogue for the solid support synthesis of aminoacyl-tRNA fragments

[reaction: see text] An efficient procedure for the immobilization of 3'-deoxy-3'-(O-methyltyrosyl)aminoadenosine was developed. A poly(ethylene glycol)-derived diacid linker/spacer was attached to aminomethyl polystyrene. Coupling of the 2'-hydroxy instead of the 2'-O-succinylated ribonucleoside resulted in high immobilization yields (over 80%) and allowed for the recovery of valuable unreacted material. This specific procedure should be applicable to other ribonucleosides containing a bulky modification at the 3'-position and can be used for the stepwise construction of 3'-aminoacyl- or 3'-peptidyl-RNA conjugates.     

Reactivity and catalytic activity of cationic lonomers for the nucleophilic substitution reactions

Polystyrene-based crosslinked cationic ionomers containing ammonium or phosphonium chlorides (AxRCI and PxBuCI) were reacted with decyl methanesulfonate. The kinetic data were correlated with the swelling behavior of the ionomers and the solution viscosity of the corresponding linear ionomers. The reactivity of the ionomers was independent of the particle size of the ionomer beads, indicating no diffusion control of the reaction. The solvent and the ion content of the ionomers greatly affect the reactivity. In nonpolar solvents with a low acceptor number, A_N, such as toluene, the aggregation of ionic groups with an increasing ion content reduces the reactivity. A solvent with a high value of A_N, such as chloroform, led a very low reactivity independent of the ion content. Aprotic polar solvent, such as acetonitrila, promoted the dissociation of the ionic groups and furnished a relatively high reactivity independent of the ion content. Several catalytic substitution reactions were carried out under liquid-solid-solid triphase conditions. The kinetic results were accounted for in terms of slow nucleophile transport and fast chemical reaction within the ionomer particles. © 1994 John Wiley & Sons, Inc.     

Enzyme immobilization on a pH-responsive porous polymer membrane for enzymatic kinetics study

Immobilization of enzymes onto carriers is a rapidly growing research area aimed at increasing the stability, reusability and enzymolysis efficiency of free enzymes. In this work, the role of phase-separation and a pH-responsive “hairy” brush, which greatly affected the topography of porous polymer membrane enzyme reactors (PMER), was explored. The porous polymer membrane was fabricated by phase-separation of poly(styrene-co-maleic anhydride-acrylic acid) and poly(styrene-ethylene glycol). Notably, the topography and pores size of the PMER could be controlled by phase-separation and a pH-responsive “hairy” brush. For evaluating the enzymolysis efficiency of d-amino acid oxidase (DAAO) immobilized carrier (DAAO@PMER), a chiral ligand exchange capillary electrophoresis method was developed with d-methionine as the substrate. The DAAO@PMER showed good reusability and stability after five continuous runs. Notably, comparing with free DAAO in solution, the DAAO@PMER exhibited a 17.7-folds increase in catalytic velocity, which was attributed to its tailorable topography and pH-responsive property. The poly(acrylic acid) moiety of poly(styrene-co-maleic anhydride-acrylic acid) as the pH-responsive “hairy” brush generated topography changing domains upon adjusting the buffer pH, which enable the enzymolysis efficiency of DAAO@PMER to be tuned based upon the well-defined architectures of the PMER. This approach demonstrated that the topographical changes formed by phase-separation and the pH-responsive “hairy” brush indeed made the proposed porous polymer membrane as suitable supports for enzyme immobilization and fitting for enzymolysis applications, achieving high catalytic performance.     

Diastereoselective synthesis of highly substituted polycyclic scaffolds via a one-pot four-step tandem catalytic process

A rapid and diastereoselective synthesis of highly substituted aminobicyclo[4.3.0]nonanes and bicyclo[4.4.0]decanes from alkyne derived allylic alcohols has been developed using a one-pot multi-bond forming tandem catalytic process. Overman rearrangement of the allylic trichloroacetimidates was followed by a ring closing enyne metathesis/cross metathesis sequence of reactions, in which both steps were catalysed by Grubbs second generation catalyst. The resulting exo-diene was then subjected to a hydrogen bonding directed Diels–Alder reaction forming an endo-adduct as a single diastereomer. Variation of the cross metathesis partner and dienophile allowed examination of the scope of this one-pot process and the preparation of a diverse series of highly substituted polycyclic scaffolds.     

Parallel synthesis of novel benzimidazoles on a soluble polymer support

Liquid phase combinatorial synthesis using a soluble polyethylene glycol (PEG) polymer support and commercially available 3-nitro-4-fluoro benzoic acid is carried out in order to create a molecular library of trisubstituted benzimidazoles. The PEG-ester conjugate of 3-nitro-4-fluoro benzoic acid is subjected to ipso-fluoro displacement by various primary amines. The nitro group is reduced under neutral conditions using excess zinc and ammonium chloride, producing the polymer-boundo-phenylene diamines. Reaction of the diamines with different aldehydes results in cyclisation to benzimidazoles. The polymer support is cleaved releasing the desired products in high yields and purity. All reactions are performed at room temperature.      

An efficient synthesis of sialoglycoconjugates on a peptidase-sensitive polymer support

A novel method for the enzymatic synthesis of oligosaccharide derivatives on a -chymotrypsin-sensitive polymer support is described. The primer polymer having N-acetyl-D-glucosamine (GlcNAc) residue through a phenylalanine-containing spacer moiety was successfully elongated with galactosyl and sialyltransferases to give a glycopolymer bearing sialyl (2→6) N-acetyllactosamine branches in high yield. Subsequent hydrolysis with -chymotrypsin proceeded smoothly and afforded a versatile sialotrisaccharide derivative having a terminal amino group which can be used for creating neoglycoconjugates.     

A novel catalytic one-pot synthesis of carbazoles via consecutive amination and C-H activation

Sequential palladium catalysed amination and C-H activation reactions occur between 2-chloro-N-alkylated anilines and aryl bromides to give carbazoles in one pot.