The Mizoroki-Heck reaction between in situ generated alkenes and aryl halides: cross-coupling route to substituted olefins.

This review covers palladium-catalyzed typical Mizoroki-Heck cross-coupling reactions of aryl halides with in situ generated alkenes, by following a typical Heck coupling mechanism to form substituted olefins unlike direct cross-coupling of alkenes with aryl halides in Heck olefination. These reactions solve the issue of alkenes undergoing polymerization at high temperatures and increase reaction efficiency by reducing the reaction time and purification steps.

Metal catalyzed C-H functionalization on triazole rings.

The present review covers advancement in the area of C-H functionalization on triazole rings, by utilizing various substrates with palladium or copper as catalysts, and resulting in the development of various substituted 1,2,3- and 1,2,4-triazoles. Synthesis of these substituted compounds is necessary from the perspective of pharmaceutical, medicinal, and materials chemistry.

Synthesis, structural characterization, and bonding analysis of two-coordinate copper(I) and silver(I) complexes of pyrrole-based bis(phosphinimine): new metal-pyrrole ring π-interactions.

The reaction between 2,5-bis(diphenylphosphinomethyl)pyrrole and Me3SiN3 gave the new pyrrole-based bis(phosphinimine) L1H in an excellent yield. L1H reacts with [CuCl(COD)]2, AgBF4, or AgOTf to give the corresponding two-coordinate mononuclear ionic complex formulated as [M{(L1H)-κ2N,N}]+[X]- where M = Cu and Ag; X = [CuCl2], BF4 or OTf. Their single crystal X-ray diffraction studies confirmed the two-coordinate geometry formed by the chelate bonding mode of L1H. These 10-membered metalacycles exhibit planar chirality and were also characterized by spectroscopic methods. In addition, in all three structures, there exists a hitherto unknown π-interaction between the pyrrole ring atoms and metal, represented as η2-(Cα-N) in the copper(i) complex, and η3-(Cα-N-Cα') in the silver(i) complexes. These weak interactions were supported by DFT calculations in terms of their electron densities, non-covalent interaction plots and the decrease in the aromaticity of the pyrrole ring.

The pyrrole ring η2-hapticity bridged binuclear tricarbonyl Mo(0) and W(0) complexes: catalysis of regioselective hydroamination reactions and DFT calculations.

Following the report of the ferrocene structure, metal complexes containing the heteroatom-substituted cyclopentadienyl (Cp) analogue, that is the η5 pyrrolyl ligand, have been reported. While the Cp ligand continues to be a favorite ligand in organometallics, the transition metal chemistry of the pyrrolyl ligand is still in the developing stage. In view of this, we carried out the reaction between the multidentate ligand 2,3,4,5-tetrakis(3,5-dimethylpyrazolylmethyl)pyrrole (LH) and Mo(CO)6 or [W(CO)3(CH3CN)3] and isolated two new binuclear tricarbonyl Mo(0) and W(0) complexes, [Mo2(CO)6(µ-η2:η2-LH-κ4N)] (1) and [W2(CO)6(µ-η2:η2-LH-κ4N)] (2). Their X-ray structural analyses showed that the metal centers are bridged by the double bonds of the central pyrrole ring (µ-η2:η2), a rarely observed coordination mode. Interestingly, complex 1 is a catalyst precursor for the hydroamination reactions of phenylacetylene with a series of secondary amines at room temperature offering the regioselectively formed anti-Markovnikov product in excellent yields. In addition, DFT calculations were performed to understand the bonding nature of the pyrrole ring in 1 and 2 and to estimate the energy of six different conformations of LH.

The syn and anti isomers of the porphyrinogen-like precursor of calix[4]phyrin: isolation, X-ray structure, anion binding and fluoride-ion-mediated proton-deuterium exchange studies.

Porphyrinogen-like precursors of calix[4]phyrins are presumed to be unstable owing to their auto-oxidation. In contrast to this, the syn and the anti isomers of a calix[4]pyrrole molecule containing pyridine moieties at the meso positions were isolated and their structures were determined by single crystal X-ray diffraction studies. Both the isomers gave the same calix[4]phyrin molecule upon oxidation. The anion binding properties of both the isomers were studied in DMSO-d6 by the EQNMR method, which showed that they have a preference of binding with the F(-) ion over the other large sized halide and oxo anions. In addition, the F(-) ion mediated H/D exchange process was monitored by the (19)F NMR method. The solution state structures of the 1 : 1 F(-) ion complexes containing deuterium atoms formed by a random but sequential substitution of NH protons by deuterium atoms were identified from their multiplicity patterns observed in the proton coupled (19)F NMR spectrum, which are supported by the proton decoupled (19)F NMR spectrum showing one singlet for each type of F(-) ion complex in solution for both the syn and anti isomers, correlating with their solid state structures.