4,4’-trimethylenedipiperidine as a nitrogen heterocycle solvent and/or catalyst: Liquid phase tandem Knoevenagel–Michael condensation

Authors : Lia ZAHARANI, Nader GHAFFARI KHALIGH, Hayede GORJIAN, Mohd RAFIE JOHAN

Pages : 261-268

View : 17 | Download : 12

Publication Date : 0000-00-00

Article Type : Research Paper

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 insert ignore into journalissuearticles values(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 insert ignore into journalissuearticles values(a); avoiding hazardous, toxic, volatile, and flammable materials and solvents, insert ignore into journalissuearticles values(b); avoiding tedious processes, harsh conditions, and multiple steps for the preparation of catalysts, insert ignore into journalissuearticles values(c); using a less toxic and noncorrosive catalyst, insert ignore into journalissuearticles values(d); minimizing hazardous waste generation and simple workup process, and insert ignore into journalissuearticles values(e); high recyclability of TMDP. Another important result of this work is that the TMDP can be a promising alternative for toxic, volatile, and flammable base reagents such as piperidine and triethylamine in liquid phase organic syntheses owing to its unique properties such as being less toxic, nonflammable, and nonvolatile, and having a low melting point, broad liquid range temperature, high thermal stability, and safe handling and storage.
Keywords : Homogeneous catalysis, heterocycles, multicomponent reactions, waste prevention