Synthesis, crystal structures, spectral investigations, conformational analysis and DFT studies of N- heterocyclic carbene precursors

Three new 2-hydroxyethyl substituted N-heterocyclic carbene (NHC) precursors were synthesized in this study. These NHC precursors were prepared from 1-(alkyl/aryl)benzimidazole and alkyl halides. Their structural characterizations were performed by elemental analysis, H-1 NMR, C-13 NMR, FT-IR and UV-Vis spectroscopy and single-crystal X-ray diffraction. The spectral features were also characterized by Density Functional Theory (DFT) at B3LYP/Lanl2dz//6-31G++(d,p) basis set. Two most stable conformers belonging to the compounds were found by potential energy surface (PES) scan, and the theoretical ground-state geometries were investigated. Among these conformers, the geometry of the conformer-I for all compounds matches almost well with the experimental results. H-1 and C-13 NMR chemical shifts were calculated with GLAD approach and compared to the observed ones. Detailed vibrational assignments of the wavenumbers of the conformers were carried out based on the potential energy distribution (PED). Natural bond orbital (NBO) analysis was used to analyze the stability of the molecules arising from hyperconjugative interactions and charge delocalization. The HOMO-LUMO energy gap of the stable conformers was calculated for comparing their chemical reactivity behavior. Molecular electrostatic potential (MEP) diagrams were used to get information about ?the size, shape, charge density distribution and site of chemical reactivity of each stable conformer. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots were also carried out to obtain an insight into the behavior of the interactions in the compounds. (C) 2019 Elsevier B.V. All rights reserved

2-hydroxyethyl-substituted (NHC)PdI2(pyridine) (Pd-PEPPSI) Complexes: Synthesis, Characterization and the Catalytic Activity in the Sonogashira Cross-coupling Reaction

Here, new series of the 2-hydroxyethyl-substituted (NHC)PdI2(pyridine) (Pd-PEPPSI) complexes have been synthesized. These complexes have been prepared from the 2-hydroxyethyl-substituted N-heterocyclic carbene (NHC) precursors, palladium chloride and pyridine. The synthesized Pd-PEPPSI complexes have been characterized by using H-1 NMR, C-13 NMR, FTIR spectroscopy and elemental analysis techniques. The catalytic activity of the 2-hydroxyethyl-substituted Pd-PEPPSI complexes has been examined in the Sonogashira cross-coupling reaction by using phenylacetylene and aryl bromide. The Pd-PEPPSI complexes have demonstrated great activity in the Sonogashira cross-coupling reaction. The molecular and crystal structures of the three of the Pd-PEPPSI complexes were determined by single-crystal X-ray diffraction method. X-ray studies show that all the molecular structures adopt slightly distorted square-planar geometry around the palladium (II) center

New (NHC)Pd(II)(PPh3) complexes: synthesis, characterization, crystal structure and its application on Sonogashira and Mizoroki-Heck cross-coupling reactions

In this study, new six Pd-based complexes containing mixture N-heterocyclic carbene (NHC) and triphenylphosphine-(PPh3) ligands were synthesized from the reaction of the (NHC)PdI2(pyridine) with-PPh3. The new (NHC)PdI2(PPh3) complexes were characterized using FTIR, H-1-NMR, C-13-NMR, and P-31-NMR spectroscopy and elemental analyses techniques. These spectra are consistent with the proposed formula. Molecular and crystal structure of two complexes was obtained using single-crystal X-ray diffraction method. Based on the crystal results, a cis geometry was assigned to all the complexes. These new complexes have been examined as the catalyst in the Sonogashira cross-coupling reaction. The catalytic conversions of the complexes were obtained between 71 and 99% from the reaction of phenylacetylene and aryl bromides. Also, these new complexes have been examined as the catalyst in the Mizoroki-Heck cross-coupling reaction. The catalytic conversions of the complexes were obtained between 80 and 100% from the reaction of styrene and aryl bromides

Mixed phosphine/N-heterocyclic carbene-palladium complexes: synthesis, characterization, crystal structure and application in the Sonogashira reaction in aqueous media

A series of 2-hydroxyethyl-substituted N-heterocyclic carbene-(NHC)PdX2PPh3 complexes have been synthesized by substitution of the pyridine or 3-chloropyridine ligand in (NHC)PdX2(pyridine/3-chloropyridine) complexes with triphenylphosphine. The new complexes were characterized by H-1, C-13 {H-1}, P-31 {H-1}NMR, FTIR spectroscopy and elemental analysis. Also, the molecular and crystal structures of 1c and 1d have been obtained by single-crystal X-ray diffraction. The 2-hydroxyethyl-substituted (NHC)PdX2PPh3 complexes have been examined as catalysts for the Sonogashira cross-coupling reaction in water/DMF solvent mixtures

New 2-hydroxyethyl substituted N-Heterocyclic carbene precursors: Synthesis, characterization, crystal structure and inhibitory properties against carbonic anhydrase and xanthine oxidase

Here, the synthesis, spectral and the structural studies of 2-hydroxyethyl substituted N-heterocyclic carbene (NHC) precursors and the enzyme inhibition activities of the NHC precursors were investigated against the cytosolic carbonic anhydrase I and II isoenzymes (hCA I and hCA II), and xanthine oxidase (XO). The IC50 values of NHC precursors against these enzymes were determined by spectrophotometric method. The spectra of new NHC precursors have been obtained by using H-1 NMR, C-13 NMR, FTIR spectroscopy and elemental analysis techniques. The structure of a new NHC precursor was established by using single-crystal X-ray diffraction method. The results of inhibition experiment indicated that all 2-hydroxyethyl substituted NHC derivatives showed remarkable inhibition activity toward hCA I, hCA II and XO. The range of IC50 values for hCA I, hCA II and XO inhibition was determined as 0.1565-0.5127, 0.1524-0.5368 and 1.253-5.342 mu M. Especially, trimethylbenzyl derivative of 2-hydroxyethyl substituted NHC precursor has demonstrated high inhibition effect on all studied enzymes due to steric bulk of this substituent. (C) 2019 Elsevier B.V. All rights reserved

2-Hydroxyethyl substituted NHC precursors: Synthesis, characterization, crystal structure and carbonic anhydrase, alpha-glycosidase, butyrylcholinesterase, and acetylcholinesterase inhibitory properties

This study contains novel a serie synthesis of N-heterocyclic carbene (NHC) precursors that 2-hydroxyethyl substituted. The NHC precursors have been prepared from 1-(2-hydroxyethyl)benzimidazole and alkyl halides. The novel NHC precursors have been characterized by using H-1 NMR, C-13 NMR, FTIR spectroscopy and elemental analysis techniques. Molecular and crystal structures of 2a, 2d, 2e, 2f and 2g were obtained with single-crystal X-ray diffraction studies. These novel NHC precursor's derivatives effectively inhibited the a-glycosidase, cytosolic carbonic anhydrase I and II isoforms (hCA I and II), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE). Inhibition constant (K-i) were found in the range of 0.30-9.22 nM for alpha-glycosidase, 13.90-41.46 nM for hCA I, 12.82-49.95 nM for hCA II, 145.82-882.01 nM for BChE, and 280.92-1370.01 nM for AChE, respectively. (C) 2017 Elsevier B.V. All rights reserved

2-Hydroxyethyl substituted NHC precursors: Synthesis, characterization, crystal structure and carbonic anhydrase, alpha-glycosidase, butyrylcholinesterase, and acetylcholinesterase inhibitory properties

This study contains novel a serie synthesis of N-heterocyclic carbene (NHC) precursors that 2-hydroxyethyl substituted. The NHC precursors have been prepared from 1-(2-hydroxyethyl)benzimidazole and alkyl halides. The novel NHC precursors have been characterized by using H-1 NMR, C-13 NMR, FTIR spectroscopy and elemental analysis techniques. Molecular and crystal structures of 2a, 2d, 2e, 2f and 2g were obtained with single-crystal X-ray diffraction studies. These novel NHC precursor's derivatives effectively inhibited the a-glycosidase, cytosolic carbonic anhydrase I and II isoforms (hCA I and II), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE). Inhibition constant (K-i) were found in the range of 0.30-9.22 nM for alpha-glycosidase, 13.90-41.46 nM for hCA I, 12.82-49.95 nM for hCA II, 145.82-882.01 nM for BChE, and 280.92-1370.01 nM for AChE, respectively. (C) 2017 Elsevier B.V. All rights reserved