Abstract
Diethylamine catalyzed tandem Knoevenagel-Michael reactions have been carried out in aqueous medium as an efficient, greener and cost effective process for the simple one-pot synthesis of bis-dimedone derivatives. Reaction of substituted aromatic aldehyde (1 equiv.) and dimedone (2 equiv.), in the presence of aqueous diethylamine medium at room temperature provides bis-dimedone derivatives 3a-n in excellent yields (87-95%) within a very short reaction time (15-60 min). All the bis-dimedone derivatives were obtained in high purity and the products were fully characterized by physical and spectroscopic data. The structures of compounds 3b, c were elucidated by single crystal X-ray diffraction technique. Compound 3b crystallizes in the monoclinic space group P 21/n with a= 10.2895(9) angstrom, b= 18.0995(15) angstrom, c = 15.8615(13) angstrom, alpha = 90 degrees, beta = 107.975(2)degrees, gamma = 90 degrees, V = 2809.8(4) angstrom(3), and Z = 4. Compound 3c crystallizes in the monoclinic space group P 21/n with a = 10.2816(16)angstrom, b = 18.080(3) angstrom, c = 15.637(2) angstrom, alpha= 90 degrees, beta = 107.076(4)degrees, gamma = 90 degrees, V = 2778.6(7) angstrom(3), and Z = 4.
The use of inexpensive, eco-friendly and readily available reagents, easy work-up, and high purity products makes the procedure a convenient and robust method for the synthesis of tandem Knoevenagel-Michael adducts. (C) 2014 King Saud University. Production and hosting by Elsevier B.V.