Ultrasound-assisted 1,3-dipolar cycloaddition and cyclopropanation reactions for the synthesis of bis-indolizine and bis-cyclopropane derivatives.

Ultrasound irradiation can promote the 1,3-dipolar cycloaddition reaction of 2-chloropyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile, to afford the indolizine and bis-indolizine derivatives respectively. While the reaction of pyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile under ultrasound irradiation provided, in an unusual manner, cyclopropane and bis-cyclopropane derivatives, respectively. These cycloaddition and cyclopropanation reactions were carried out in the presence of triethylamine, in acetonitrile, at room temperature.