摘要:
An efficient microwave-assisted Pictet-Spengler protocol employing boric acid/acetic acid as a catalytic system was elaborated for the synthesis of 1-aryl-beta-carbolines. Under the novel conditions tryptamine and 2-formylbenzoic acid furnished a pentacyclic skeleton in a single step, whereas using o-phthalaldehyde as a coupling partner led to the formation of an isoindolone derivative. Three beta-carbolines primarily resulted from the reactions involving carboxy-substituted heteroaryl aldehydes and avoided cyclisation to polycondensed skeletons with enhanced ring strain, as was evidenced by density functional theory (DFT) modelling.