Studies on isocyanides: synthesis of tetrazolyl-isoindolinones via tandem Ugi four-component condensation/intramolecular amidation

The Ugi four-component condensation between methyl o-formylbenzoates 1, anilines 2a–c, isocyanides 3, and trimethylsilyl azide (4) afforded the expected Ugi adducts 5a–d, which were cyclized to the title compounds 6a–d upon treatment with sodium ethoxide in ethanol. Starting from aralkyl- or alkylamines 2d–g the Ugi adducts underwent a spontaneous cyclization to tetrazolyl-isoindolinones 6e–j.