title: Ultrasound-assisted phase-transfer catalysis method in an aqueous medium to promote the Knoevenagel reaction: advantages over the conventional and microwave-assisted solvent-free/catalyst-free method.
abstract: Given the broad spectrum of uses of acrylonitrile derivatives as fluorescent probes, AChE inhibitors, and others, it is necessary to find easy, efficient and simple methods to synthesize and diversify these compounds. We report the results of a comparative study of the effects of three techniques on the reactions between heterocyclic aldehydes and 2-(benzo[d]thiazol-2-yl)acetonitrile: stirring; ultrasound coupled to PTC conditions (US-PTC); and MW irradiation (MWI) under solvent and catalyst-free conditions. The effects of conditions on reaction parameters were evaluated and compared in terms of reaction time, yield, purity and outcomes. The US-PTC method is more efficient than the MWI and conventional methods. The reaction times were considerably shorter, with high yields (>90%) and good levels of purity. In addition, X-ray diffraction analysis and quantum mechanical calculations, at the level of density functional theory (DFT), ratify obtaining acrylonitrile isomers with E configurations. The crystal structure of 3c is stabilized by weak C-Ho⋯N intermolecular interactions (Ho⋯NC=2.45 Å, Co⋯NC=3.348(3) Å, Ho⋯NC=162°), forming centrosymmetric ring R2(2) (20) along the crystallographic a axis.
authors.affiliation: Organic Synthesis Laboratory and Biological Activity (LSO-Act-Bio), Institute of Chemistry of Natural Resources, Universidad de Talca, Casilla 747, Talca, Chile; Center for Bioinformatics and Molecular Simulation, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile. Electronic address: pdelatorre@utalca.cl.
authors.forename: Pedro
authors.initials: P
authors.lastname: De-la-Torre
authors.affiliation: Center for Bioinformatics and Molecular Simulation, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile. Electronic address: eosorio@utalca.cl.
authors.forename: Edison
authors.initials: E
authors.lastname: Osorio
authors.affiliation: Center for Bioinformatics and Molecular Simulation, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile. Electronic address: jalzate@utalca.cl.
authors.forename: Jans H
authors.initials: JH
authors.lastname: Alzate-Morales
authors.affiliation: Center for Bioinformatics and Molecular Simulation, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile. Electronic address: jcaballero@utalca.cl.
authors.forename: Julio
authors.initials: J
authors.lastname: Caballero
authors.affiliation: Research Group Heterocyclic Compounds, Chemistry Program, Universidad del Atlántico, Km 7 vía Puerto Colombia, Barranquilla, Colombia. Electronic address: jorgetrilleras@mail.uniatlantico.edu.co.
authors.forename: Jorge
authors.initials: J
authors.lastname: Trilleras
authors.affiliation: Organic Synthesis Laboratory and Biological Activity (LSO-Act-Bio), Institute of Chemistry of Natural Resources, Universidad de Talca, Casilla 747, Talca, Chile. Electronic address: lastudi@utalca.cl.
authors.forename: Luis
authors.initials: L
authors.lastname: Astudillo-Saavedra
authors.affiliation: Department of Chemistry, Universidad de Antofagasta, Av. Angamos 601, Casilla 170, Antofagasta, Chile. Electronic address: ibrito@uantof.cl.
authors.forename: Iván
authors.initials: I
authors.lastname: Brito
authors.affiliation: Department of Physics, Universidad de Antofagasta, Av. Angamos 601, Casilla 170, Antofagasta, Chile. Electronic address: acardenas@uantof.cl.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Cárdenas
authors.affiliation: Heterocyclic Compounds Research Group, Department of Chemistry, Universidad del Valle, A. A. 25360 Cali, Colombia. Electronic address: jairo.quiroga@correounivalle.edu.co.
authors.forename: Jairo
authors.initials: J
authors.lastname: Quiroga
authors.affiliation: Organic Synthesis Laboratory and Biological Activity (LSO-Act-Bio), Institute of Chemistry of Natural Resources, Universidad de Talca, Casilla 747, Talca, Chile. Electronic address: mgutierrez@utalca.cl.
authors.forename: Margarita
authors.initials: M
authors.lastname: Gutiérrez
mesh_terms: D000447:Aldehydes / Q000737:chemistry / Q000528:radiation effects; D002384:Catalysis; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D008872:Microwaves; D009570:Nitriles / Q000737:chemistry* / Q000528:radiation effects*; D012997:Solvents; D014465:Ultrasonics / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D000447:Aldehydes; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D009570:Nitriles; D012997:Solvents
keywords: Density functional theory; Knoevenagel reactions; Microwave; Phase-transfer catalysis; Ultrasound; X-ray crystallography