Published data on the preparation of biscoumarin derivatives is discussed in this review. Biscoumarins are synthesized via the reaction of 4‐hydroxy coumarin and different aldehydes. Many attempts have been made to apply various catalysts and also different reaction conditions to synthesize biscoumarins. The role of the catalyst and the reaction conditions on the reaction time and yield of the products is discussed.

No abstract

New 5-aryl-10-(4-(4-methoxyphenyl)thiazole-2-yl)-9,10-dihydropyrido[2,3-d:5,6-d']dipyrimidinone-2,4,6,8-(1H,3H,5H,7H)-tetraones 6a-d were synthesized through one-pot four-component reaction of aldehydes, barbituric acid, and thiazole using Zn(2+) @KSF under reflux condition. The key features of this reaction are: incorporating four heterocyclic rings, using a heterogeneous and efficient catalyst, high yield, and easy-to-setup reaction. The structure of the products was confirmed by FT-IR, (1)H NMR, and (13)C NMR spectra. The antibacterial activities of compounds 6a-d were screened against Escherichia coli, Micrococcus luteus, Pseudomonas aeruginosa, and Staphylococcus aureus bacterial strains using the zone inhibition method. Also, the 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities of compounds 6a-d were evaluated. All compounds showed good antioxidant capacity in comparison to ascorbic acid. The IC50 values of the antioxidant activity were calculated. The proposed mechanism for antioxidant activity is discussed.

A series of novel bis-thiazoles were synthesized through a one-pot semi-fivecomponent reaction of the prepared α-bisbromo ketones, aldehydes, and thiosemicarbazide in the presence of p-TsOH under reflux condition. Products were obtained in reasonable yields via an efficient, convenient, and simple setup. The inhibitory activity on bacterial growth of the products was studied against Gramnegative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacterial strains (Micrococcus luteus, Staphylococcus aureus) at different concentrations (25, 50, 100, and 200 μg/mL at 600 nm). Most of the products showed inhibitory activity at the concentration of 200 μg/mL. In addition, bis-thiazoles showeed high to moderate antioxidant activity using the diphenylpicrylhydrazyl (DPPH) method. Bis-thiazoles 6i and 6j showed higher antioxidant activity than vitamin C and vitamin E.

A convenient, one-pot multi-component synthesis of new 2,4-disubstituted hydrazinyl-thiazoles was accomplished using different aldehydes/ketones, thiosemicarbazide, and 4-methoxy phenacyl bromide in the presence of a catalytic amount of AcOH in EtOH. Products were obtained in reasonable yields and high purity. The in vitro antioxidant activity of hydrazinyl-thiazoles was evaluated by DPPH radical scavenging activity in comparison to ascorbic acid. Synthesized thiazoles 14c and 14g possessed the lowest IC50 values. Also, hydrazinyl-thiazoles were screened for their in vitro antibacterial activity against six strains of bacteria including S. aureus, M. luteus, E. coli, Ps. aeruginosa, B. subtilis, and A. hydrophila where some products showed good antibacterial activity. Moreover, compound 14a showed anticancer activity against melanoma cancerous cell lines A375 with LC50=0.55 mg/ml, slightly selective versus normal cell lines (Hu-2) with LC50=1.19 mg/ml..