Parallel synthesis of 4,5-dihydro-1H-1,4-benzodiazepine-2,3-diones

An efficient strategy for the parallel solid-phase synthesis of 4,5-dihydro-1H-1,4-benzodiazepine-2,3-diones is described. The reductive alkylation of resin-bound primary amine with different substituted o-nitrobenzaldehydes generated a secondary amine, which was treated further with methyl chlorooxoacetate. The nitro group was reduced with tin(II) chloride. During the overnight reduction, an in situ intramolecular cyclization occurred to provide, following HF cleavage, the desired 4,5-dihydro-1H-1,4-benzodiazepine-2,3-dione.