An efficient and eco-friendly synthesis of 2-pyridones and functionalized azaxanthone frameworks via indium triflate catalyzed domino reaction
A green and efficient one-pot method has been developed for the synthesis of 2-pyridone and functionalized azaxanthone frameworks using indium triflate as an environmentally friendly, reusable catalyst. In this one-pot reaction, 3-formylchromones display a diverse pattern of reactivity upon reaction with different classes of alkenes. An indium triflate-promoted reaction with (Z)-N-methyl-1-(methylthio)-2-nitroethenamine leads to 3-formylchromone annulations to 2-pyridone and analogues via a remarkably facile chromone ring opening. The analogous reaction with N,N’-dimethyl-2-nitro-ethene-1,1-diamine results in the formation of synthetically useful functionalized azaxanthones via a 6π-electrocyclization reaction.