Microwave irradiation has been used to enhance the reaction yields and selectivities for organic transformation. In this paper, microwave irradiation (MW) was investigated for the environmentally benign synthesis of benzoxazoles through the cyclization of 2-aminophenols and benzaldehydes using deep eutectic solvent (DES) as a catalyst. The [CholineCl][oxalic acid] was easily synthesized from choline chloride with oxalic acid and used without further purification. [CholineCl][oxalic acid] catalyzed the synthesis of benzoxazoles to produce the desired product in a good to excellent conversion and selectivity under MW irradiation. The presence of [CholineCl][oxalic acid] helps to promote the rapid heating transfer from microwave irradiation into the reaction mixture. The [CholineCl][oxalic acid] can be recovered and reused several times without a considerable degradation in catalytic activity.
Montmorillonite is a "green" solid catalyst and support used in many organic reactions. In this paper, we have prepared some acid-activated montmorillonites from Cu Chi clay. Then, we determinated physical-chemical properties such as specific surface area, cation exchange capacity, X-ray diffraction, chemical composition and acidity of these samples. Finally, we chose the best from these montmorillonites and used as catalyst in the one-pot conversion of benzaldehyde into benzonitrile under solvent-free and microwave irradiation.
KF supported on montmorillonite K10 catalyzed three-component cyclocondensation of aromatic aldehyde, cyclohexan-1,3-dione and malononitrile under ultrasound irradiation and solvent-free condition to give the corresponding 4H-pyrans in high yields. This method provides several advantages such as short time, mild condition and the catalyst can be recycled easily.
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