Arylglyoxals three-component reaction

An indium trichloride-catalyzed three-component reaction of substituted phenols, an arylglyoxal monohydrate, and /)-toluenesulfonamide has been shown to furnish 2-aryl-3-aminobenzofurans (Equation 121) <2005SL2047>. 

Recently, Eftekhari-Sis and Vahdati-Khajeh (2013) developed a green and effective method for the preparation of 5-aryl-4-hydroxy-2-methyl-lFf-pyrrole-3-carboxylates (18) via a three-component reaction of arylglyoxal hydrates (16) with P-dicarbonyl compounds (17) in the presence of ammonium acetate using water as a solvent under ultrasonic irradiation (Scheme 8.6). The reactions proceeded rapidly and afforded the corresponding pyrroles in good to high yields in very short reaction times. 

Wang and Chen et al. developed the three-component reaction of arylglyoxals, phenols and p-toluenesulfonamide for the synthesis of highly substituted benzo-furans, and InCls was found to be better than Hf(OTf)3, their previous catalyst of choice, for this reaction [223] (Figure 8.102). 

Eftekhari-Sis, B. and Vahdati-Khajeh, S. 2013. Ultrasound-assisted green synthesis of pyrroles and pyridazines in water via three-component condensation reactions of arylglyoxals. Curr. Chem. Lett. 2 85-92. 

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