Dipolar cycloaddition strategy for three-component synthesis of chromeno[3',4':3,4]pyrido[2,1-a]isoquinoline derivatives

A rapid and efficient protocol to fused pentacyclic compounds, the chromeno[3',4':3,4]pyrido[2,1-a]isoquinolines, via a diastereoselective 1,4-dipolar cycloaddition reaction of isoquinoline, dialkyl acetylenedicarboxylates, and 3-acetyl coumarins, is described.

A novel protocol for catalyst-free synthesis of fused six-member rings to triazole and pyrazole

Herein, an effectual, quick and novel method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine derivatives. This series of fused six-member rings to triazole and pyrazole was prepared via the catalyst-free reaction of dialkyl acetylenedicarboxylates and 3-substituted 1H-1,2,4-triazole or 3-amino-1H-pyrazole-4-carbonitrile. The structures of the prepared products were deduced from their Fourier-transform infrared, elemental analysis and proton and carbon-13 nuclear magnetic resonance spectral data. A novel and green method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine derivatives.

One-pot synthesis of γ -spiroiminolactones and γ -dispiroiminolactones using N,N'-disubstituted parabanic acid and thioparabanic acid derivatives

A direct entry and simple process for the synthesis of [Formula: see text]-spiroiminolactones present in a large number of natural products has been developed. In the first step, the synthesis of parabanic acid derivatives was commenced from the reaction of [Formula: see text]-disubstituted urea and thiourea with oxalyl chloride, then a three-component reaction was carried out with isocyanides, acetylenic esters, and [Formula: see text]-disubstituted parabanic acid derivatives. The method allows the construction of a variety of [Formula: see text]-spiroiminolactone structures in good to high yields starting from readily available precursors. It was found that in the case of [Formula: see text]-diphenyl thioparabanic acid, additional products of [Formula: see text]-dispiroiminolactones have been formed due to the higher electrophilicity of [Formula: see text]-dicarbonyl groups. The structures were fully established using spectroscopic analysis NMR, IR, and Mass spectrometry. The crystal structure of [Formula: see text]-dispiroiminolactone was confirmed from single-crystal X-ray diffraction study.