Tandem Knoevenagel–Michael reactions in aqueous diethylamine medium: A greener and efficient approach toward bis-dimedone derivatives

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 (15–60min). 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)Å, b=18.0995(15)Å, c=15.8615(13)Å, α=90°, β=107.975(2)°, γ=90°, V=2809.8(4)Å3, and Z=4. Compound 3c crystallizes in the monoclinic space group P 21/n with a=10.2816(16)Å, b=18.080(3)Å, c=15.637(2)Å, α=90°, β=107.076(4)°, γ=90°, V=2778.6(7)Å3, 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.