Formation of N-cyclopropylhydrazones by azo coupling of cyclopropyldiazonium with aliphatic CH acids

Decomposition of N-cyclopropyl-N-nitrosourea under the action of K₂CO₃ or KOH containing 15—20% of H₂O at 0—7 °C gives rise to cyclopropyldiazonium, which reacts with some -diketones, methyl cyanoacetate, or malonodinitrile to form the corresponding cyclopropylhydrazones. The latter compounds are analogous to products of azo coupling and isomerization of aryldiazonium ions with the above-mentioned substrates. These transformations provide the first example of azo coupling of the cyclopropyldiazonium ion in the series of activated aliphatic CH acids.     

Knoevenagel缩合反应研究的新进展

综述了近年来Knoevenagel缩合反应研究的新进展, 包括微波、超声波、固相合成、离子液体等新技术新试剂在该反应中的应用.     

Electro-catazone treatment of an ozone-resistant drug: Effect of sintering temperature on TiO2 nanoflower catalyst on porous Ti gas diffuser anodes

Electrochemical heterogeneous catalytic ozonation (E-catazone) is a promising and advanced oxidation technology that uses a titanium dioxide nanoflower (TiO_2-NF)-coated porous Ti gas diffuser as an anode material. Our previous study has highlighted that the importance of the TiO_2-NF coating layer in enhancing OH production and rapidly degrading O₃-resistant drugs. It is well known that the properties of TiO_2-NF are closely related to its sintering temperature. However, to date, related research has not been conducted in E-catazone systems. Thus, this study evaluated the effect of the sintering temperature on the degradation of the O₃-resistant drug para-chlorobenzoic acid (p-CBA) using both experimental and kinetic modeling and revealed its influence mechanism. The results indicated that the TiO_2-NF sintering temperature could influence p-CBA degradation and OH production. TiO_2-NF prepared at 450 °C showcased the highest p-CBA removal efficiency (98.5% in 5 min) at a rate of 0.82 min⁻¹, and an OH exposure of 8.41 × 10⁻¹⁰ mol L⁻¹ s. Kinetic modeling results and interface characterization data revealed that the sintering temperature could alter the TiO₂ crystallized phase and the content of surface-adsorbed oxygen, thus affecting the two key limiting reactions in the E-catazone process. That is, ≡TiO₂ surface reacted with H₂O to form TiO₂-(OH)₂, which then heterogeneously catalyzed O₃ to form OH. Consequently, E-catazone with a TiO_2-NF anode prepared at 450 °C generated the highest surface reaction rate (5.00 × 10⁻¹ s⁻¹ and 4.00 × 10^-3 L mol^-1 s⁻¹, respectively), owing to its higher anatase content and adsorbed oxygen. Thus, a rapid O₃-TiO₂ reaction was achieved, resulting in an enhanced OH formation and a highly effective p-CBA degradation. Overall, this study provides novel baseline data to improve the application of E-catazone technology.     

Microwave assisted synthesis of an unusual dinitro phytochemical

A novel dinitro secondary metabolite, 2-nitro-4-(2^′-nitroethenyl)phenol from a marine source, has been prepared via highly accelerated, microwave assisted, nitration reactions using mild reagents. ipso-Substitution of a carboxy group by a nitro group is discussed.     

Bifurcations and transition states

Bifurcations of reaction channels are related to valley-ridge inflection points and it is examined what happens when these do not coincide with transition states. Under such conditions there result bifurcating regions. There exist a number of different prototypes for such regions which are discussed explicitly on the basis of the pertinent Taylor expansions. When bifurcations occur close enough to transition states then there result bifurcating transition regions. An example for a bifurcating transition region is exhibited which is obtained from a quantum mechanical ab initio calculation for the ring opening of cyclopropylidene to aliene. In general there exist no orthogonal trajectory patterns which could serve as simplified models for channel bifurcations.Operated for the U.S. Department of Energy by Iowa State University under Contract No. W-7405-ENG-82. This work was supported by the Office of Basic Energy Sciences     

Triazole: the Keystone in Glycosylated Molecular Architectures Constructed by a Click Reaction

The copper(I)‐catalyzed modern version of the Huisgen‐type azide–alkyne cycloaddition to give a 1,4‐disubstituted 1,2,3‐triazole unit is introduced as a powerful ligation method for glycoconjugation. Owing to its high chemoselectivity and tolerance of a variety of reaction conditions, this highly atom‐economic and efficient coupling reaction is especially useful for the effective construction of complex glycosylated structures such as clusters, dendrimers, polymers, peptides, and macrocycles. In all cases the triazole ring plays a key role by locking into position the various parts of these molecular architectures. The examples reported and briefly discussed in this short review highlight the use of this reaction in carbohydrate chemistry and pave the way to further developments and applications.     

Stereoselective effects in the solid-phase hydrogenation of unsaturatedl-hydroxyproline derivatives

The solid-phase catalytic hydrogenation of (R-4tert-butoxy-Δ¹-pyrroline-2-carboxylic) acid under the action of hydrogen spillover was studied. The reaction proceeds stereoselectively with the predominant formation of thel-amino acid. The configuration of the asymmetric center formed is determined by that of the asymmetric C(4) atom. The major portion of the isotope label is incorporated into the allylic C(3) and C(5) positions, and the β-H atoms are more mobile. Using quantum-chemical calculations, the geometric structure of thel-hydroxyproline molecule was calculated, and the spin-spin coupling constants for this tritium-labeled amino acid were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1820–1823, October, 1997.     

Regio- and Stereocontrolled Nucleophilic Addition Reactions of An Unsymmetrically Disbustituted Butadiene η4-Molybdenum Cationic Complex

The reactions of a new cationic complex, [Cp(CO)₂Mo(η⁴-2-methyl-3-SPh-C₄H₄)]⁺ PF^?₆ (3), with carbon, hydride, and nitrogen nucleophiles were found to give only the C-1 addition products in good yield. The X-ray crystal structures of two of the addition products 4a and 4e confirm the regio- and stereochemistry of the nucleophilic additions.     

Fluorous Synthesis of Biaryl-Substituted Proline Analogs by 1,3-Dipolar Cycloaddition and Suzuki Coupling Reactions

A solution-phase synthesis of bicyclic prolines containing four points of diversity has been developed by a two-step synthesis involving 1,3-dipolar cycloaddition of perfluoroalkylsulfonyl-protected hydroxybenzaldehydes followed by Pd-catalyzed Suzuki coupling reaction of fluorous sulfonates with boronic acids. Both reactions are conducted under microwave irradiation and reaction mixtures are purified by solid-phase extractions without performing chromatography.     

Development of resin-to-resin transfer reactions (RRTR) using Sonogashira chemistry

Sonogashira chemistry can be used according to the ‘resin-to-resin transfer reaction’ (RRTR) concept. Two fragments, one containing the halide moiety and the second one incorporating the alkyne functionality, are anchored on different solid supports using allyl and/or Wang-type linkages. Treatment with Pd(0) cleaves the allyl-linked fragment(s) which subsequently undergo Sonogashira coupling under the same conditions.