Search results for "FUNCTIONAL"
showing 10 items of 4822 documents
A Molecular Electron Density Theory Study of the Role of the Copper Metalation of Azomethine Ylides in [3 + 2] Cycloaddition Reactions.
2018
The copper metalation of azomethine ylides (AYs) in [3 + 2] cycloaddition (32CA) reactions with electron-deficient ethylenes has been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) level, in order to shed light on the electronic effect of the metalation in the course of the reaction. Analysis of the Conceptual Density Functional Theory reactivity indices indicates that the metalation of AYs markedly enhances the nucleophilicity of these species given the anionic character of the AY framework. These 32CA reactions take place through stepwise mechanisms characterized by the formation of a molecular complex. Both nonmetalated and metalated 32CA reactions …
Diels–Alder reaction on perylenediimides: synthesis and theoretical study of core-expanded diimides
2019
A one-step reaction for the fusion of aromatic rings to one or both bay areas of perylenediimides using benzynes is presented. Yields as high as 70% for naphthoperylenendiimide 2 and 80% for dibenzocoronenediimide 3 are obtained. The reaction is also carried out using substituted benzynes, heteroaromatic benzynes and substituted perylenediimides. A combined experimental/theoretical approach, based on measuring redox and absorption/emission properties and performing density functional theory calculations, indicates that increasing the π-skeleton of PDIs transversally leads to significant and unexpected changes in the electronic, redox and optical properties. The observed trends are rationali…
Cycloaddition of Strained Cyclic Alkenes and Ortho-Quinones : A Distortion/Interaction Analysis
2020
The chemistry of strained unsaturated cyclic compounds has experienced remarkable growth in recent years via the development of metal–free click reactions. Among these reactions, the cycloaddition of cyclopropenes and their analogues to ortho-quinones has been established as a highly promising click reaction. The present work investigates the mechanism involved in the cycloaddition of strained dienes to ortho-quinones and structural factors that would influence this reaction. For this purpose, we use B97D density functional theory calculations throughout, and for relevant cases, we use spin component–scaled MP2 calculations and single–point domain-based local pair natural orbital coupled cl…
A Combined Experimental and Theoretical Study of the Ammonium Bifluoride Catalyzed Regioselective Synthesis of Quinoxalines and Pyrido[2,3-b]pyrazines
2015
International audience; Ammonium bifluoride was efficiently used (at a 0.5 mol % loading) to catalyze the cyclocondensation between 1,2-arylenediamines and 1,2-dicarbonyl compounds at room temperature in methanol-water, affording quinoxalines and pyrido[2,3-b]pyrazines in excellent yields. Importantly, 2,8-disubstituted quinoxalines and 3-substituted pyrido[2,3-b]pyrazines were regioselectively formed by reacting aryl glyoxals with 3-methyl-1,2-phenylenediamine and 2,3-diaminopyridine, respectively. Analysis of the DFT reactivity indices allowed to explain the catalytic role of ammonium bifluoride.
Theoretical Investigation of the Low-Energy States of CpMoCl(PMe 3 ) 2 and Their Role in the Spin-Forbidden Addition of N 2 and CO
2003
International audience; A recent computational investigation of Jahn−Teller effects in unsaturated 16-electron d4d6 [CpMLn] complexes (Abu-Hasanayn, F.; Cheong, P.; Oliff, M. Angew. Chem.2002, 41, 2120) highlighted the typical presence of two spin-triplet and two singlet states of competing stability in these complexes and pointed out the necessity to account for more than one electronic state in studies thereof. Consequently, we have reinvestigated the addition of N2 to all the four low-energy states of CpMoCl(PH3)2, a reaction for which previously only one singlet and one triplet state have been considered (Keogh, D. W.; Poli, R. J. Am. Chem. Soc.1997, 119, 2516). The present study was pe…
Copper(I)-catalysed regioselective synthesis of pyrazolo[5,1-c]-1,2,4-triazoles: A DFT mechanistic study
2017
Abstract Formation of pyrazolo[5,1-c]-1,2,4-triazoles by means of Cu(I)-catalysed [3+2] cycloaddition (32CA) reactions of C,N-cyclic azomethine imines with phenylacetylene, experimentally reported by Katritzky et al. (JOC 2012, 77, 5813), was studied using the density functional theory (DFT) method. Comparison with the uncatalysed 32CA reaction indicates that the Cu(I) catalyst provides new reaction pathways with lower electronic energy barriers in dichloromethane as solvent. The mechanism proposed by Katritzky for the Cu(I) catalysed reaction is compared with that proposed by Sharpless et al. (JACS 127, 2005, 210). The major difference between these two mechanisms lies in the coordination …
Half-sandwich complexes of molybdenum-(III), -(IV) and -(V) with P–O and P–N bifunctional ligands Ph2PCH2X (X = 2-oxazolinyl, or C(O)NPh2)
2000
International audience; The reaction of the ligands Ph2PCH2X (X = 2-oxazolinyl, I; or C(O)NPh2, II) with the half-sandwich molybdenum(III) precursors [Mo(η-C5R5)(μ-Cl)2]2 (R = H or Me) has been investigated. Ligand I reacts with both complexes to form the corresponding adducts [Mo(η-C5R5)Cl2(Ph2PCH2C3H4NO)] (R = H, 1; or Me, 2). The reaction between I and [MoCp*Cl4] (Cp* = η-C5Me5) affords [MoCp*Cl4(Ph2PCH2C3H4NO-κ1P)] as a kinetic isomer, which then transforms quantitatively to [MoCp*Cl3(Ph2PCH2C3H4NO-κ2P,N)]+Cl−, 3. Ligand II reacts with [MoCp(μ-Cl)2]2 (Cp = η-C5H5) to afford the adduct [CpMoCl2{Ph2PCH2C(O)NPh2-κ2P,O}], 4, as an equilibrium mixture of two isomers. Longer reaction times in…
Towards the synthesis of substituted porphyrins by a pyridyl group bearing a reactive functionality
2010
Pyridyl-substituted porphyrins bearing a reactive functionality were prepared via Suzuki cross-coupling reactions and resulted in very good yields. These compounds are precursors of new porphyrin architectures able to coordinate two metals: one in the porphyrin core and the second around the pyridyl moiety. During the coupling reactions, a higher reactivity of a chloro picolyl group was evidenced compared to a bromo function on the same reacting molecule.
Squaramide-Catalyzed Asymmetric aza-Friedel-Crafts/N,O-Acetalization Domino Reactions Between 2-Naphthols and Pyrazolinone Ketimines
2017
N-Boc ketimines derived from pyrazolin-5-ones were explored to develop an unprecedented domino aza-Friedel-Crafts/N,O-acetalization reaction with 2-naphthols. The novel method requires a catalyst loading of only 0.5 mol % of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra-substituted stereogenic centers in excellent yields (95-98 %) and stereoselectivity (>99:1 d.r. and 97-98 % ee). A different reactivity was observed in the case of 1-naphthols and other electron-rich phenols, which led to the aza-Friedel-Crafts adducts in 70-98 % yield and 47-98 % ee.
2-Methyltetrahydrofuran: A Green Solvent for Iron-Catalyzed Cross-Coupling Reactions
2018
Iron‐catalyzed cross‐coupling reactions allow sustainable formation of C−C bonds using cost‐effective, earth‐abundant base‐metal catalysis for complex syntheses of pharmaceuticals, natural products, and fine chemicals. The major challenge to maintain full sustainability of the process is the identification of green and renewable solvents that can be harnessed to replace the conventional solvents for this highly attractive reaction. Herein, iron‐catalyzed cross‐coupling of aryl chlorides and tosylates with challenging organometallic reagents possessing β‐hydrogens is found to proceed in good to excellent yields with the green, sustainable, and eco‐friendly 2‐methyltetrahydrofuran (2‐MeTHF) a…