Liquid phase tandem Knoevenagel–Michael condensation of various aromatic and heteroaromatic aldehydes with barbituric acid or 2-thiobarbituric acid and malononitrile was studied in a one-pot three-component reaction. For the first time, TMDP was employed as a safe and efficient solvent and/or catalyst in the liquid and aqueous ethanol medium, respectively, for the practical and eco-friendly Knoevenagel–Michael condensation. The reactions were carried out by using greener procedures, including a) the use of TMDP as an N-heterocycle organocatalyst in a green medium including water and ethanol (1:1 v/v) at reflux temperature, and b) the use of TMDP as a dual solvent-catalyst at 65 °C in the absence of any solvent. | Turkish Journal of Chemistry Turk J Chem 2021 45 261-268 http chem TÜBİTAK Research Article doi kim-2010-41 4 4 -trimethylenedipiperidine as a nitrogen heterocycle solvent and or catalyst Liquid phase tandem Knoevenagel Michael condensation 1 1 2 1 Lia ZAHARANI Nader GHAFFARI KHALIGH Hayede GORJIAN Mohd RAFIE JOHAN 1 Nanotechnology and Catalysis Research Centre Institute for Advanced Studies University of Malaya Kuala Lumpur Malaysia 2 Department of Food Science and Technology Sari Agricultural Sciences and Natural Resources University Sari Iran Received Accepted Published Online Final Version Abstract Liquid phase tandem Knoevenagel Michael condensation of various aromatic and heteroaromatic aldehydes with barbituric acid or 2-thiobarbituric acid and malononitrile was studied in a one-pot three-component reaction. For the first time TMDP was employed as a safe and efficient solvent and or catalyst in the liquid and aqueous ethanol medium respectively for the practical and eco-friendly Knoevenagel Michael condensation. The reactions were carried out by using greener procedures including a the use of TMDP as an N-heterocycle organocatalyst in a green medium including water and ethanol 1 1 v v at reflux temperature and b the use of TMDP as a dual solvent-catalyst at 65 C in the absence of any solvent. High to excellent yields of the desired pyrano 2 3-d pyrimidinones were obtained under the two earlier mentioned conditions. The current methodologies have advantages including a avoiding hazardous toxic volatile and flammable materials and solvents b avoiding tedious processes harsh conditions and multiple steps for the preparation of catalysts c using a less toxic and noncorrosive catalyst d minimizing hazardous waste generation and simple workup process and e high recyclability of TMDP. Another important result of this work is that the TMDP can be a promising alternative for toxic volatile and .
