Water-acetic acid mediated an efficient one-pot eco-friendly synthesis of novel bis-isoxazolopyrroloquinoline derivatives

An efficient, cost-effective and environmentally benign synthesis of novel tetracyclic bis-isoxazolopyrroloquinoline derivatives has been developed via one-pot four-component reaction of 4-amino-3-methyl-5-styrylisoxazoles, dimedone, aryl glyoxal monohydrates and 5-amino-3-methylisoxazole by employing water as a reaction medium and acetic acid (AcOH) as a green promoter. The advantages of this protocol are environmentally friendly, metal-free, less reaction time, operational simplicity, high yields, broad substrate scope and easy purification. Most significant of all, this method is green.     

A mild and efficient synthesis of chiral tetrahydroquinolino pyranose derivatives catalyzed by lanthanum(iii) nitrate hexahydrate

A mild and highly efficient synthesis of chiral tetrahydroquinolino pyranose derivatives is described. The reaction of a chiral α,β‐unsaturated aldehyde containing a hydroxyl group with different aryl amines using lanthanum(III) nitrate hexahydrate as a catalyst afforded corresponding chiral tetrahydroquinolinated pyranosides in excellent yields. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:429–433, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20441     

Palladium‐catalysed room‐temperature Suzuki–Miyaura coupling in water extract of pomegranate ash,a bio‐derived sustainable and renewable medium

An agro waste‐derived, ‘water extract of pomegranate ash’ (WEPA), has been utilized for the first time as a renewable medium for Pd(OAc)₂‐catalysed Suzuki–Miyaura cross‐coupling at room temperature. This method offers a simple and sustainable synthesis of biaryls from aryl halides and arylboronic acids under ligand‐ and external base‐free aerobic and ambient conditions. This method has been found effective for both activated and unactivated aryl halides in the production of biaryls with moderate to nearly quantitative yields. The protocol shows high chemoselectivity over identical/similar reactive sites in aryl halides (i.e. selectivity over identical halogens or different halogens of aryl halides). This method exhibits high regioselectivity, i.e. the selective reactivity of a halogen over other identical halogens at different positions on the aromatic nucleus. Therefore, we disclose here a clean, benign, substantial chemo‐ and regioselective and highly economic alternative method for the palladium‐assisted synthesis of biaryls using an agro waste‐derived medium.     

Asymmetric synthesis of a sex pheromone (3S,5R,6S)-3,5-dimethyl-6-isopropyl-3,4,5,6-tetrahydropyran-2-one

An Oppolzer anti-aldol approach for the synthesis of the sex pheromone (3S,5R,6S)-3,5-dimethyl-6-isopropyl-3,4,5,6-tetrahydropyran-2-one is reported.     

Facile synthesis of tin oxide nanoparticles stabilized by dendritic polymers

Tin(IV) oxide nanoparticles were synthesized via the reaction of carbon dioxide with stannate ions immobilized by dendritic polymers. For PAMAM and PPI dendrimer hosts, resultant nanoparticle diameters were 2.5-3 nm; 3-3.5 nm nanoparticles resulted from use of a poly(ethyleneimine) hyperbranched polymer. Our conditions represent the only precedent for SnO2 nanoparticulate growth using dendritic architectures, as well as a novel application for CO2 as a reactive gas for the controlled growth of metal oxide nanoparticles.     

Molecular dynamics simulations of multilayer films of polyelectrolytes and nanoparticles

We performed molecular dynamics simulations of multilayer assemblies of flexible polyelectrolytes and nanoparticles. The film was constructed by sequential adsorption of oppositely charged polymers and nanoparticles in layer-by-layer fashion from dilute solutions. We have studied multilayer films assembled from oppositely charged polyelectrolytes, oppositely charged nanoparticles, and mixed films containing both nanoparticles and polyelectrolytes. For all studied systems, the multilayer assembly proceeds through surface overcharging after completion of each deposition step. There is almost linear growth in the surface coverage and film thickness. The multilayer films assembled from nanoparticles show better layer stratification but at the same time have higher film roughness than those assembled from flexible polyelectrolytes.     

Porphyrin N-Pincer Pd(II)-Complexes in Water: A Base-Free and Nature-Inspired Protocol for the Oxidative Self-Coupling of Potassium Aryltrifluoroborates in Open-Air

Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.     

Enhanced permeation, leaf retention, and plant protease inhibitor activity with bicontinuous microemulsions

Bicontinuous microemulsions (BCMEs) have excellent solubulizing properties along with low interfacial tension and aqueous content that can be controlled. In this work, water soluble plant protease inhibitor (PI), well characterized for its activity against insect pests, was incorporated into a BCME system and explored for permeation on hydrophobic leaf surfaces and protease inhibition activity. The bicontinuous nature of the microemulsion containing water:2-propanol:1-butanol (55:35:10 w/w) was characterized using conductivity and self-diffusion coefficient measurements. The PI was soluble in the water-rich bicontinuous domains, stable in the microemulsions, and protease inhibition activity was retained for a prolonged duration. The microemulsions ensured greater wettability and a wider spread of the PI on hydrophobic leaf surfaces as revealed by contact angle measurements. Significantly, trypsin inhibition activity assays of the PI recovered from the leaves after delivery from the microemulsion indicated a significant increase in the PI retention on the leaf. This BCME enabled greater leaf permeation and retention of the PI can be attributed to a temporary disruption of the waxy leaf surface followed by self-repair without causing any long term damage to the plant.     

Cyclisation of 2-(2-aminophenyl)quinazolin-4(3H)-one reexamined: formation of isomeric angular fused quinazolinoquinazolinones and their spectroscopic identification

Cyclisation of 2-(2-aminophenyl)quinazolin-4(3H)-ones on to N₃ and on to N₁ leading to 6-alkyl-(8H)-quinazolino[4,3-b]quinazolin-8-one and 6-alkyl-(13H)-quinazolino[3,4-a]quinazolin-13-one, respectively was described for the first time. The differences in the IR and carbon NMR data of these isomeric fused quinazolinoquinazolinones afford a useful method for distinguishing between the two series.