One-pot Synthesis of 2,3-Benzodiazepines from Arynes and β-Diketones

Novel one-pot synthesis of 2,3-benzodiazepines from aryne precursors was accomplished. Tofisopam, well-known anxiolytics, could be synthesized via C C bond insertion of 4,5-dimethoxybenzyne with 2-ethyl-1-(3,4-dimethoxyphenyl)-butane-1,3-dione, followed by the reaction with hydrazine hydrate in a one-pot operation. This protocol is applicable to the synthesis of other biologically active 2,3-benzodiazepines, such as Girisopam and Nerisopam.