Two-step syntheses of fused quinoxaline-benzodiazepines and bis-benzodiazepines

Novel two-step solution phase protocols for the synthesis of fused 6,7,6,6-quinoxalinone-benzodiazepines 1 and 6,7,7,6-bis-benzodiazepines 2 are reported. Optimization of the methodology to produce these tetracyclic scaffolds was enabled by microwave irradiation and the use of the convertible isocyanide, 4-tert-butyl cyclohexen-1-yl isocyanide. The methodology employs the Ugi reaction to assemble the desired diversity and acid treatment enables sequential ring-closing transformations.