A solvent-free synthesis of five series of coumarin derivatives using microwave assistant is presented herein. The synthesized compounds are fully characterized by UV-VIS, FT-IR, and NMR spectroscopy. 1. Introduction Coumarin (2H-Lbenzopyran-2-one) and its derivatives possess a wide range of various biological and pharmaceutical activities. They have a wide range of applications as antitumor [1, 2], anti-HIV [3, 4], anticoagulant [5, 6], antimicrobial [7, 8], antioxidant [9, 10], and anti-inflammatory [11, 12] agents. The antitumor activities of coumarin compounds have been extensively examined [13–16]. Although most of the existing natural coumarins have been isolated from higher plants, some of them have been discovered in microorganisms, for example, aminocoumarin antibiotics: novobiocin, coumermycin A1, and chlorobiocin (produced by the actinomycete Streptomyces niveus) [17]. Synthetic coumarin derivatives have been obtained by chemical modification of the coumarin ring. Recently, density functional theory (DFT) has been accepted by the quantum chemistry community as a cost-effective approach for the computation of molecular structure, vibration frequencies, and energies of chemical reactions. Many studies have shown that the molecular structures and vibration frequencies calculated by DFT methods are more reliable than MP2 methods [18–26]. While there is sufficient evidence that DFT provides accurate description of the electronic and structural properties of solids, interfaces, and small molecules, relatively little is known about the symmetric performance of DFT applications to their molecular associates. Structure activity relationships of coumarin derivatives have revealed that the presence of substituted amino derivatives is an essential feature of their pharmacological action. Based on these findings, we try to describe the synthesis of some compounds featuring different heterocyclic rings fused onto the coumarin moiety with the aim of obtaining more potent pharmacologically active compounds. 2. Experimental 2.1. General The chemicals used for the synthesis were supplied by Sigma-Aldrich. Purity of the compounds was checked on thin layer chromatography (TLC) plates (Silica Gel G) using the solvent systems benzene-ethyl acetate-methanol (40？:？30？:？30, v/v/v) and toluene-acetone (75？:？25, v/v). The spots were located under UV light (254 and 365？nm). Melting points were determined on GallenKamp (MFB-600) melting point apparatus and were uncorrected. The IR spectra of the compounds were recorded on a shimadzu FT-IR-8300 spectrometer as KBr disk.
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