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Ultrasound-enhanced one-pot synthesis of 3-(Het)arylmethyl-4-hydroxycoumarins in water.

Research paper by Giovanni G Palmisano, Francesco F Tibiletti, Andrea A Penoni, Francesca F Colombo, Stefano S Tollari, Davide D Garella, Silvia S Tagliapietra, Giancarlo G Cravotto

Indexed on: 10 Sep '10Published on: 10 Sep '10Published in: Ultrasonics Sonochemistry



Abstract

3-(Aryl)methyl-4-hydroxycoumarins were produced in good to excellent yields by reaction between 4-hydroxycoumarin and (hetero)aromatic aldehydes in the presence of Hantzsch 1,4-dihydropyridine (HEH) which works as an hydride donor (i.e., in a sequential Knoevenagel-reductive Michael addition). The sonochemical-assisted procedure (method B) provides an improved and accelerated conversion when compared to conventional silent reactions (method A). Experiments carried out according to method B showed that the reaction could be more efficiently run in the absence of organic solvents, at 30-40°C in open vessel, without the need of an excess HEH and with simplified work-up and separation procedures.