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The metal complex (5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin-iron (III) chloride (FeTSPP) was new employed in an environmentally benign protocol as an efficient catalyst for a “click” chemistry approach for the synthesis of tetrazole and guanindinyltetrazole derivatives via [2?+?3] cycloaddition reaction of nitriles and azide derivatives in aqueous medium. The synthesized compounds were obtained in excellent yield, short reaction times and a recoverable catalyst.

A series of 3,6-bis(4-triazolyl)pyridazines equipped with terminal phenyl substituents with varying degree of fluorination were synthesized by using the facile copper-catalyzed azide–alkyne cycloaddition and their structures were thoroughly investigated i

Urea structures, of which N,N-diethylurea (DEU) proved to be the most efficient, were discovered to catalyze amidation reactions between electron-deficient aryl azides and phenylacetaldehydes. Experimental data support 1,3-dipolar cycloaddition between DEU-activated enols and electrophilic phenyl azides, especially perfluoroaryl azides, followed by rearrangement of the triazoline intermediate. The activation of the aldehyde under near-neutral conditions was of special importance in inhibiting dehydration/aromatization of the triazoline intermediate, thus promoting the rearrangement to form aryl amides.

The synthesis and catalytic activity of a new class of 1,2,3-triazolyl N-heterocyclic carbene organocatalysts is described. These new catalysts chemoselectively facilitate the oxidative esterification of aldehydes. NMR acidity studies show an inverse correlation between triazolium acidity and reactivity. Kinetic studies show that the resting state of the catalyst involves a NHC-aldehyde adduct. A catalytically active intermediate was synthesized and characterized by X-ray diffraction as the initial carbene-aldehyde adduct.

The CoII complex of a D2-symmetric chiral porphyrin ([Co(D2-Por*)], see scheme) is a highly effective catalyst for the enantioselective aziridination of alkenes with fluoroaryl azides. The reaction can be performed at RT w

A new player on the field! "Click" bis-triazoles have been introduced as a highly efficient new class of neutral C-H?anion-binding organocatalysts (see scheme). DFT and NMR studies were used to confirm this activation modus and identify the optimal catalyst. Copyright

[3+2]-cycloaddition reactions of aromatic azides and silylated alkynes in aqueous media yield 1,5-disubstituted-4-(trimethyl-silyl)-1H-1,2,3-triazoles. The formation of the 1,5-isomer is highly favored in this metal-free cycloaddition, which could be proven by 1D selective NOESY and X-ray investigations. Additionally, DFT calculations corroborate the outstanding favoritism regarding the 1,5-isomer. The described method provides a simple alternative protocol to metal-catalyzed "click chemistry" procedures, widening the scope for regioselective heavy-metal-free synthetic applications.

The chemistry and kinetics of singlet (pentafluorophenyl)nitrene were studied by chemical trapping and laser flash photolysis techniques. Photolysis of pentafluorophenyt azide in cyclohexane, benzene, diethylamine, pyridine, tetramethylethylene, tetrahydrofuran, dimethyl sutfoxide, and dimethyl sulfide forms adducts in fair to good yields. At ambient temperature singlet (pentafluorophenyl)nitrene is intercepted, and intersystem crossing to the lower energy triplet state is unimportant. Triplet nitrene chemistry can be achieved by benzoylbiphenyl photosensitization, the presence of methanol or ethyl iodide, or by lowering the reaction temperature below 0 °C. The singlet nitrenc adduct formed in pyridine is an ylide whose structure has been determined by X-ray crystallography. The ylide has an intense absorption maximum at 390 nm which varies only slightly with solvent. The pyridine ylicle is a useful probe for monitoring the absolute kinetics of singlet (pentafluorophenyl)nitrene by laser flash photolysis techniques.

Nitrosation reactions with sodium nitrite can be accomplished cleanly in anhydrous trifluoroacetic acid as solvent, which permits the use of both deactivated and insoluble primary amines and amides as starting materials.