Volume 23, Issue 6

A mild and efficient method was developed for the preparation of tetrahydrobenzo[ b ]pyrans through a one-pot three-component condensation of aldehydes, malononitrile and dimedone in the presence of silica supported dual acidic ionic liquid (DAIL@SiO 2 ) as a powerful catalyst under solvent-free conditions. This procedure is characterized by mild reaction conditions, simple workup and environmental friendliness. Moreover, the catalyst could be recycled for five times with only a slight loss of catalytic activity.

Trifluoromethyl containing heterocycles are an integral part of many biologically active compounds in the agro and pharmaceutical chemistry. Herein, we report an efficient and concise three-step synthesis of 5-halo-6-trifluoromethylpyridine-3-carbonitriles from a trifluoroacetyl vinylogous enamine starting material. Hydrolysis furnishes the carboxylic acids.

A convenient synthetic approach to derivatives of 2-trichloromethyl and 2-dichlorometylene-2 H -1,3-benzoxazines, based on intramolecular heterocyclization of readily accessible N -(α-aryloxytrichloroethyl)imidoyl chlorides, was developed. Base induced dehydrochlorination of 4-phenyl- or 4-trifluoromethyl-2-trichloromethylbenzoxazines allows preparation of 2-dichloromethylene-1,3-benzoxazines, whereas dehydrochlorination of 4-fluoromethyl analogs under similar conditions is accompanied by formal 1,5- H -shift to afford respective 2-dichloromethyl-4-fluoromethylene-1,3-benzoxazines.

2-Oxoimidazolidine-1,3-disulfonic acid (OImDSA) is a recoverable catalyst for the synthesis of 1,3-thiazolidine-4-ones at room temperature in a one-pot procedure without using any organic solvents. Moreover, the catalyst can be easily recovered and recycled for five runs without significant loss of catalytic activity. The structures of the synthesized 1,3-thiazolidine-4-one compounds were confirmed by 1 H NMR, 13 C NMR and FTIR spectral data and elemental analysis.

New synthetic approach to ( E )-2-aryl/hetarylvinyl-4-phenyl-quinoline-3-carboxylic acids was developed, featuring three different synthetic transformations, namely the Arbuzov reaction, in situ Horner-Emmons olefination and subsequent ester hydrolysis occurring as a one-pot procedure. The molecular structures of newly synthesized products were confirmed by spectral data and elemental analysis.

Ferrocene-containing ionic liquid supported on silica-coated Fe 3 O 4 magnetic nanoparticles (nano Fe 3 O 4 @SiO 2 -IL-Fc), a novel heterogeneous nanocatalyst, was synthesized. The structure of the catalyst was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction patterns (XRD), energy-dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FE-SEM). The novel nanomagnetic catalyst was used in the one-pot synthesis of pyrano[3,2- b ]pyran derivatives by the three-component reaction of various aldehydes, malononitrile and kojic acid or chlorokojic acid at room temperature under ultrasonic irradiation. This new method has many advantages such as simplicity, short reaction times, high yields, easy workup and easy purification. Also, the nanocatalyst can be separated on an external magnet and reused for at least six consecutive runs without any significant loss of its catalytic activity.

An improved and scalable method for the synthesis of zolpidem ( 1 ), a hypnotic drug, was developed. A two-step sequence involving imine formation and subsequent tandem reaction between an imine and propiolamide in the presence of CuI/BINOL, an efficient promoter for the tandem reaction, is described. Zolpidem was efficiently prepared in a 54% isolated yield and the hemitartrate salt of zolpidem was produced in 37% yield by simple crystallization, without tedious column chromatography. The procedure can be scaled up to >10 g. The yield of 1 increased to 83% following isolation of the intermediate imine 5 .

An approach to the synthesis of 7-methyl-4-azaindole, which is a valuable building block for drug discovery programs, is described. The method relies on using a bromine atom as a ‘place holding group’ for one of the carbon atoms of the pyridine ring throughout the reaction sequence, and it is removed only upon the final reductive cyclization leading to the azaindole ring. Exhaustive hydrogenation of the target product proceeds in a diastereoselective manner and leads to a bicyclic conformationally restricted diamine derivative.

Fourteen 1 H -pyrazole-5-carboxylic acid derivatives containing oxazole and thiazole rings were synthesized and characterized by 1 H NMR, mass spectrometry and elemental analysis. Most target compounds were obtained in overall yields in the range of 30–50%. The insecticidal activities of these new compounds against Aphis fabae were evaluated. The bioassays’ results indicate that some of these compounds exhibit good activities, especially compound 7h which shows 85.7% mortality against A. fabae at a concentration of 12.5 mg/L. This activity is comparable to that of the commercial insecticide imidacloprid.