A one-pot four-component synthesis of 3-[(2-amino-4-arylthiazolium-5-yl)(aryl)methyl]-2-oxo-2H-1-benzopyran-4-olates

An efficient method has been developed for the synthesis of 3-[(2-amino-4-arylthiazolium-5-yl)(aryl)methyl]-2-oxo-2H-1-benzopyran-4-olates via a tandem reaction involving 4-hydroxycoumarin, benzaldehydes, thiourea, and 2-bromo-1-arylethan-1-ones, using p-toluenesulfonic acid as catalyst in glacial acetic acid under reflux. The identity of the parent product was confirmed by X-ray analyses while the other similar derivatives were identified by NMR. The good yields of the products, regioselectivity, and lack of metal promoters are the main advantages of this protocol.