Isolation of Ugi Four-Component Condensation Primary Adducts: A Straightforward Route to Isocoumarins

Ugi four-component condensation (Ugi-4CC) between 2-formylbenzoic acid, phenacylamine dimethyl acetal, and isocyanides afforded 1H-isochromen-1-ones (isocoumarins). These products, where structure corresponds to the tautomeric enediamine form of the Ugi-4CC primary adducts, were stable enough to allow their isolation and characterization. Stable isocoumarins were also obtained by employing anilines as the amino component in the Ugi four-component condensation.