Band 24, Heft 6

Antimony(III) trichloride (SbCl 3 ) is an effective catalyst (1 mol%) for the condensation of anthranilic amide with various aldehydes or ketones to quinazolin-4(3 H )-one derivatives in good to excellent yields under microwave irradiation. The process is carried out within several minutes under solvent-free conditions. This general methodology has the advantages of simplicity, mild reaction conditions and high yields of products.

An improved synthesis of 2-ethyl-5-(2-hydroxy-4-oxoquinolin-3(4 H )-ylidene)-6-aryl-5,6-dihydroimidazo[2,1- b ][1,3,4]thiadiazol-7-ium hydroxide derivatives 4a–k via the reaction of aryl glyoxal monohydrates 1a–k , quinoline-2,4-diol 2 and 2-amino-[1,3,4]thiadiazole (3) in the presence of Et 3 N/sulfamic acid in H 2 O is described. This green protocol is characterized by the use of the readily available catalyst and reactants, short reaction times, operational simplicity and high yields of products. The structures of all compounds were characterized by 1 H NMR, 13 C NMR and Fourier-transform infrared (FT-IR) spectral data and microanalyses.

Ring closure reactions of diaminomaleonitrile (DAMN) with electrophilic aryl isocyanates and aryl isothiocyanates lead to the formation of the target 5,5′-diimino-1,1′-diaryl-4,4′-biimidazolidinylidene-2,2′-diones 2a,b and 2,2′-diarylimino-4,4′-bithiazolidinylidenes 4a–e , respectively. The protocol provides a new strategy for the synthesis of a wide range of alkenes with two electron-donating and two withdrawing substituents of DAMN in moderate to good yields.

An efficient, green and environmentally friendly grindstone method for the synthesis of 2-arylbenzothiazole derivatives in the presence of urea nitrate as the catalyst under solvent-free conditions was developed. All products were characterized by elemental analysis and spectral methods.

X 2 C=Sn: compounds (X=H, Me, F, Cl, Br, Ph, Ar) are new species. The cycloaddition reactions of X 2 C=Sn: are also a new study field of unsaturated stannylene chemistry. The mechanism of cycloaddition reaction between singlet Me 2 C=Sn: and ethene was investigated for the first time using the MP2/GENECP (C, H in 6-311++G**; Sn in LanL2dz) method. From the potential energy profile, it was predicted that the reaction has one dominant channel in which the 5p unoccupied orbital of Sn: in Me 2 C=Sn: and the π orbital of ethene form a π→p donor-acceptor bond in an intermediate product. Instability of the intermediate product results in its isomerization to a four-membered ring of stannylene. The four-membered stannylene further combines with ethene to form another intermediate product that further isomerizes to a spiro-Sn-heterocyclic ring compound.

Norfloxacin-azole hybrids 3 and 6a,b were synthesized starting from norfloxacin. The treatment of these compounds with amines as a one-pot three-component reaction produced the corresponding amino derivatives 4a,b , 7a–g and 8a,b in good yields. The conventional and microwave-assisted methods were used with the latter method being more efficient. The structures of the synthesized compounds were characterized by elemental analysis, IR, 1 H NMR, 13 C NMR and MS. All compounds were screened for their antimicrobial activities. Most of them exhibit excellent antibacterial activity but are not active against selected fungi.

Ten 5-bromoindole-2-carboxamides were synthesized, characterized and evaluated for antibacterial activity against pathogenic Gram-negative bacteria Klebsiella pneumoniae , Escherichia coli , Pseudomonas aeruginosa and Salmonella Typhi using gentamicin and ciprofloxacin as internal standards. Compounds 7a–c , 7g and 7h exhibit high antibacterial activity with a minimum inhibitory concentration (MIC) of 0.35–1.25 μg/mL. Compounds 7a–c exhibit antibacterial activities that are higher than those of the standards against E. coli and P. aeruginosa .

A series of glycosyl-substituted 1,3,4-oxadiazoles were synthesized by cyclization of glycosyl-acylthiosemicarbazides via a base-catalyzed reaction. The starting glycosyl-acylthiosemicarbazide derivatives were obtained by the reaction of glycosyl isothiocyanate with various hydrazides. The acetylcholinesterase (AChE) inhibitory activities of the products were tested by Ellman’s method. The most active compounds were subsequently evaluated for the 50% inhibitory concentration (IC 50 ) values. N -(1,3,4,6-tetra- O -benzyl-2-deoxy- β -D-glucopyranosyl)-5-(4-fluorophenyl)-1,3,4-oxadiazole-2-amine ( 6i ) possesses the best AChE -inhibition activity with an IC 50 of 1.61±0.34 μ m .

In order to find new compounds with high fungicidal activity, acetamide derivatives 4a–x were rationally designed, synthesized, characterized and tested against various fungi in vivo . The bioassay results indicate that compounds 4k,m,o,r exhibit an 80% inhibition rate against Rhizoctonia solani at 500 mg/L, and compound 4j shows an 80% inhibition rate against Blumeria graminis at 500 mg/L. Therefore, compounds of 4 are promising fungicidal candidates worthy of further development.