ARTICLE Green synthesis of bis-coumarin derivatives using Fe(SD) 3 as a catalyst and investigation of their biological activities Nosrat O. Mahmoodi 1 | Zeinab Jalalifard 2 | Ghanbari Pirbasti Fathanbari 1 1 Department of Chemistry, Faculty of Sciences, University of Guilan, Rasht, Iran 2 Department of Chemistry, Ghadr Institute of Higher Education, Kuchesfahan, Rasht, Iran Correspondence Nosrat O. Mahmoodi, Department of Chemistry, Faculty of Sciences, University of Guilan, P.O. Box 41335-1914, Rasht, Iran. Email: mahmoodi@guilan.ac.ir Abstract A convenient, practical, green, and environmentally friendly method was devel- oped for the synthesis of biscoumarins and corresponding tetrakis products from the reaction of 4-hydroxycoumarin and various aldehydes. The bis-coumarins were synthesized in high yield under mild reaction conditions. Products were obtained in the presence of in situ prepared Fe(SD) 3 [Iron(III) dodecyl sulfate] as a combined Lewis acidsurfactant catalyst (LASC) in water in short reaction times. Also, the antibacterial activity of compounds was screened against Pseudomonas aeruginosa and Escherichia coli as Gram-negative bacteria and Micrococcus luteus and Staph- ylococcus aureus as Gram-positive bacterial strains. Products 3g, 3kl were most active than cefotaxime against E. coli and also compounds 3c and 3g were most active than cefotaxime against S. aureus. KEYWORDS 4-Hydroxycoumarin, bis-coumarins, green synthesis, terephthaldehyde, tetrakis-coumarins 1 | INTRODUCTION Coumarin derivatives are an important class of heterocyclic compounds and their biological activities make them inter- esting targets for multicomponent reactions (MCRs). More- over, their biological activities involve HIV inhibitory, [1] antibacterial, [2] anticancer, [3] anticoagulant, [4] antihepatitis C virus, [5] vasorelaxants, [6] enzymatic inhibitors, [7] antitumor, [8] and spasmolytic [9] activities. Also, coumarins are used as food and cosmetic additives and as brightening agents. [10,11] Synthetic routes to coumarins include Pechmann condensation, Perkin, Knoevenagel, and Reformatsky reactions as well as flash vacuum pyrolysis. [12] Among these, the Knoevenagel reaction is the most com- monly applied one, in which different types of acid catalysts such as H 2 SO 4 , P 2 O 5 , AlCl 3 , I 2 , and F 3 CCO 2 H are employed. [13,14] Many of the reactions are undesirable for industrial purposes due to difficult conditions, longer reac- tion times and corrosive reagents. Therefore, finding mild and economical synthetic methods is necessary to overcome the previous procedures. In 2009, Sangshetti et al. reported the use of MnCl 2 .4H 2 O for condensation of 4-hydroxycoumarin and aldehydes in H 2 O at 100 C in mod- erate to good yields (99%). [15] Other procedures that used microwaves [16] and ultrasound irradiation [17] have been car- ried out using catalysts such as molecular I 2 , [18] [bmim] [BF4], [19] (Bu) 4 NBr (TBAB), [20] sodium dodecyl sulfate (NaOSO 2 OC 12 H 25 ) (SDS), [21] P 4 VPyCuO-NPs, [22] RuCl 3 . nH 2 O, [23] sulfated titania [TiO 2 /SO 4 2- ], [24] Melamine trisulfonic acid (MTSA), [25] tetrabutylammonium hexa- tungstate [TBA] 2 [W 6 O 19 ], [26] Ni-NPs, [27] POCl 3 in dry dimethylformamide (DMF), [28] TiO 2 @KSF, [29] ZnO nanocomposite, [30] diethyl aluminum chloride (Et 2 AlCl), [31] LiClO 4 , [32] Piperidine, [33] nano-Fe 3 O 4 , [34] kit-6-mesoporous silica-coated magnetic nanoparticles, [35] amino glucose- functionalized silica-coated NiFe 2 O 4 nanoparticles, [36] Fe 3 O 4 @SiO 2 @KIT-6, [37] [BDBDMIm]Br-CAN, [38] citric acid, [39] and SBPDSA. [40] More catalysts and different Received: 19 November 2018 Revised: 22 April 2019 Accepted: 26 May 2019 DOI: 10.1002/jccs.201800444 © 2019 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim J Chin Chem Soc. 2019;111. http://www.jccs.wiley-vch.de 1