Microwave-assisted C-C and C-heteroatom bond formations in aqueous medium

: In recent times, microwave assisted chemistry have gained enormous attraction in organic synthesis owing to its versatile advantages such as avoidance of harsh reaction condition, increase of yield, eliminates of by product, shorter reaction time and removal of wastages. Besides, water as a reaction medium further includes more benefit as it eliminates all the drawbacks of toxic solvent which may cause injuries for our mother earth. Furthermore C-C and C-heteroatom bond formation reactions are very significant as most of the drug as well as bioactive compounds contain heterocycles or C-hetero bond which is a key tool of chemistry. This article demonstrates the advancement on the topic of the microwave assisted C-C and C-heteroatom bond formation reactions in aqueous medium.

Magnetic Recyclable Cu/Znfe2o4 for Catalytic Reduction of Nitroarenes And C-N Bond Formation Reactions

A magnetic recyclable Cu/ZnFe2O4 composite material was successfully prepared with cheap and easy-to-obtain raw materials. This obtained copper composite material could be employed as efficient catalyst for both degradation of aromatic nitro compounds and C-N bond formation reactions without extra ligands. The aromatic nitro compounds were reduced within 2 min with low catalyst dosage. And high catalytic activity, broad substrate scope and low loading were achieved for Ullmann-type C-N bond formation reaction. The morphology of Cu/ZnFe2O4 was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Energy disperse spectroscopy (EDS), Transmission electronic microscopy (TEM) and Scanning electron microscopy (SEM). In addition, this environmentally friendly heterogeneous catalyst could simply be recovered via magnetic decantation and used again for six cycles with no considerable loss in activity. This developed magnetic recyclable Cu/ZnFe2O4 composite had the characteristics of easy availability, high catalytic performance, good reusability good stability and magnetic recovery properties.

Pd@Py2PZ@MSN as a Novel and Efficient Catalyst for C-C Bond Formation Reactions

In this paper, a novel catalyst is introduced based on the immobilization of palladium onto dipyrido[3,2-a:2',3'-c]phenazine modified mesoporous silica nanoparticles. Dipyrido[3,2-a:2',3'-c]phenazine (Py2PZ) ligand is synthesized in a simple method from the reaction of 1,10-phenanthroline-5,6-dione and 3,4-diaminobenzoic acid as starting materials. The ligand is used to functionalize mesoporous silica nanoparticles (MSN) and to modify its surface chemistry for immobilization of palladium. The palladium immobilized dipyrido[3,2-a:2',3'-c]phenazine modified mesoporous silica nanoparticles (Pd@Py2PZ@MSN) are synthesized and characterized by several characterization techniques, including TEM, SEM, FTIR, TGA, ICP, XRD, and EDS analysis. After the careful characterization of Pd@Py2PZ@MSN, the activity and efficiency of this catalyst is examined in carbon-carbon bond formation reactions. The results are advantageous in water and the products are obtained in high isolated yields. In addition, the catalyst shows very good reusability and did not show significant loss in activity after 10 sequential runs.

Correlation Between Reduced Mass and Gibbs Energy Change of Reaction

<p>The correlation between the Gibbs free energy change of reaction and the reduced mass was clarified. In the case of bond formation reactions, the computed Gibbs energy change of reaction increased in the positive direction as the reduced mass increased. In the case of dissociation equilibrium reactions, such as the dissociation of tetrahedral carbonyl addition compound, the computed Gibbs energy change of reaction also increased in the positive direction as the reducing mass increased, but the extent of the change was smaller than in the case of bond formation reactions. The results were in good agreement with those derived from the relationship between yield and reduced mass, indicating that was originated from the correlation between the Gibbs energy change and the reduced mass.</p>

Correlation Between Reduced Mass and Gibbs Energy Change of Reaction

<p>The correlation between the Gibbs free energy change of reaction and the reduced mass was clarified. In the case of bond formation reactions, the computed Gibbs energy change of reaction increased in the positive direction as the reduced mass increased. In the case of dissociation equilibrium reactions, such as the dissociation of tetrahedral carbonyl addition compound, the computed Gibbs energy change of reaction also increased in the positive direction as the reducing mass increased, but the extent of the change was smaller than in the case of bond formation reactions. The results were in good agreement with those derived from the relationship between yield and reduced mass, indicating that was originated from the correlation between the Gibbs energy change and the reduced mass.</p>

Total Biosynthesis of Triacsin Featuring an N-hydroxytriazene Pharmacophore

Triacsins are an intriguing class of specialized metabolites possessing a conserved N-hydroxytriazene moiety not found in any other known natural products. Triacsins are notable as potent acyl-CoA synthetase inhibitors in lipid metabolism, yet their biosynthesis has remained elusive. Through extensive mutagenesis and biochemical studies, we here report all enzymes required to construct and install the N-hydroxytriazene pharmacophore of triacsins. Two distinct ATP-dependent enzymes were revealed to catalyze the two consecutive N-N bond formation reactions, including a glycine-utilizing hydrazine-forming enzyme, Tri28, and a nitrous acid-utilizing N-nitrosating enzyme, Tri17. This study paves the way for future mechanistic interrogation and biocatalytic application of enzymes for N-N bond formation.

1.10 Boron-Centered Radicals

Boryl radicals have emerged as powerful radical intermediates in organic synthesis. This review summarizes recently developed transformations involving boryl radical species, including C—B bond formation reactions, reduction reactions, and radical catalysis.