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

作者：De La Torre Pedro^*; Osorio Edison; Alzate Morales Jans H; Caballero Julio; Trilleras Jorge; Astudillo Saavedra Luis; Brito Ivan; Cardenas Alejandro; Quiroga Jairo; Gutierrez Margarita

来源：Ultrasonics Sonochemistry, 2014, 21(5): 1666-1674.

DOI：10.1016/j.ultsonch.2014.02.021

• Knoevenagel reactions
• Phase-transfer catalysis
• Microwave
• Ultrasound
• Density functional theory
• X-ray crystallography

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-ypacetonitrile: 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-FTC 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-H-o center dot center dot center dot N intermolecular interactions (H-o center dot center dot center dot NC = 2.45 angstrom, C-o center dot center dot center dot NC = 3.348(3) angstrom, H-o center dot center dot center dot NC = 162 degrees), forming centrosymmetric ring R-2(2) (20) along the crystallographic a axis.

• 出版日期2014-9
• 单位上海生物信息技术研究中心