Encapsulation Characteristics of Cavitand Type Tetrabromo-Functionalized Resorcin[4]arenes in the Crystal Structure

Single crystal X-ray diffraction analysis of upper rim functionalized tetrabromo-resorcin[4]arenes are presented and their guest encapsulation abilities are discussed. The Br-atoms either attached directly to resorcinarene rim or extended by methylene group (CH₂–Br). The substituents on the upper-rim plays an important role in the guest encapsulation characteristic of the resorcinarene cavity. In the crystal structure the host–guest supramolecular systems were stabilized by C–H?O, C–H?π and C?H···Br nonbonding interactions. The Hirshfeld surfaces analysis and the related 2D fingerprint plots provided qualitative and quantitative account of the various supramolecular non-bonding interactions present within the crystal.

Graphic Abstract

Guest encapsulation characteristic of tetrabromo-functionalized resorcin[4]arenes.

     

A New Synthesis of Some Non-Steroidal Anti-Inflammatory Agents via Cyanophosphates1)

A simple and convenient procedure for the syntheses of some nonsteroidal anti-inflammatory agents, ibuprofen, rac-naproxen, clidanac and loxoprofen, is described.     

Spectrofluorimtric determination of hafnium with 3-hydroxychromone

The fluorescence of the 1:1 hafnium—3-hydroxychromone complex in 4—0.5 M hydrochloric acid is used to determine 0.4—9.0 μg of hafnium in 25 ml of solution; the relative standard deviation is 0.15%. Zirconium does not interfere in 2-fold amounts.     

A novel synthesis of α,β-unsaturated nitriles from aromatic ketones via cyanophosphates

Reaction of aromatic ketones with diethyl phosphorocyanidate in the presence of lithium cyanide gave cyanophosphates, which were converted into α,β-unsaturated nitriles by treatment with boron trifluoride etherate in high yields.     

Reaction of substituted benzylideneacetylacetones with hydroxylamine hydrochloride

The reaction of α,β-unsaturated β-diketones, such as 3-(o-chloro, m-nitro, and o-nitrobenzylidene)acetylacetones (I, II, and III) with hydroxylamine hydrochloride was carried out. Among them, compound I and II in acetonitrile, methanol, and acetic acid afforded 4-(α-hydroxy, methoxy, acetoxy, and chlorobenzyl)-3,5-dimethylisoxazoles (IV-XI) in fairly good yield. On the other hand, III yielded 3-(3′,5′-dimethylpyrazolo)-5-chloroanthranil (XV) under the almost same conditions by the participation of o-nitro group.     

Adsorption Characteristics of Ion-Exchanged ZSM-5 Zeolites for CO(2)/N(2) Mixtures

Adsorption characteristics of alkali metal ion-exchanged ZSM-5 zeolites, M-ZSM-5 (M=Li, Na, K, Rb, and Cs), for CO(2)/N(2) mixtures were investigated by a column method and IR study. It was shown that CO(2) was adsorbed from CO(2)/N(2) mixtures on M-ZSM-5 zeolites by two types of adsorbtion at temperatures below 333 K. One was a weak adsorption due to interaction with the wall of ZSM-5, and the other was a strong adsorption caused by interactions with the cation of ZSM-5. IR-spectra of gases adsorbed at various temperatures revealed that the CO(2) were strongly adsorbed on M-ZSM-5 in several ways, which seemed to be caused by different adsorption sites. At temperatures above 373 K, almost all CO(2) adsorbed were on cation sites, while N(2) coadsorbed with CO(2) was shown to interact with the wall of ZSM-5 under all experimental conditions. Copyright 2000 Academic Press.     

High performance of Rh(Phebox) catalysts in asymmetric reductive aldol reaction: high anti-selectivity

Chiral rhodium(bisoxazolinylphenyl) complexes (1 mol %) efficiently catalyze the asymmetric reductive aldol reaction of aldehydes and alpha,beta-unsaturated esters at 50 degrees C for ca. 0.5-1.0 h with several hydrosilanes to give the corresponding beta-hydroxypropionates with extremely high anti-selectivity (up to 98%) and enantioselectivity (up to 96% ee). The stereochemical outcome is likely due to a chairlike cyclic transition state involving rhodium-(E)-enolate.     

Reaction of ethyl 3-ethoxymethylene-2,4-dioxovalerate and ethyl ethoxymethyleneoxaloacetate with 3-aminopyrazole analogs. Synthesis and chemistry of 3,6,7-trisubstituted pyrazolo[1,5-a]pyrimidine derivatives

The chemical reactivity of a series of 3-substituted-6-acetyl-7-carbethoxypyrazolo[l,5-a]pyrimidines ( 6a,b,c ) and 3-substituted-6,7-dicarbethoxypyrazolo[1,5-a]pyrimidines ( 7a,b,c ), prepared by the condensations of the 3-aminopyrazole analogs ( 3a,b,c ) with ethyl 3-ethoxymethylene-2,4-dioxovalerate ( 1 ) or ethyl 3-ethoxymethyleneoxaloacetate ( 2 ), was investigated. Catalytic hydrogenation of 6 or 7 afforded 4,7-dihydro derivatives ( 8 or 9 ). Treatment of 6a,b with acetic acid and water underwent ring transformation into 6H-pyrazolo[1,5-a][1,3]diazepin-6-ones ( 17a,b ). By treatment with phenylhydrazine compounds of type 6 underwent cyclization to yield 2H-dipyrazolo[1,5-a:4′,3′-e]pyrimidines ( 18a,b,c ). Compounds 6 or 7 were treated with an excess of diazomethane at room temperature to give 5-methyl-6H-cyclopropa[5a,6a]pyrazolo-[1,5-a]pyrimidines ( 24 and 25 ) in excellent yields. However, when this reaction was carried out under ice cooling, only compounds of type 23 were isolated. Reaction of 6a with ethyl diazoacetate is also described.