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Four-Component Ugi Approach to Benzodiazepines
M. Sañudo, M. García-Valverde*, S. Marcaccini, J. J. Delgado, J. Rojo, T. Torroba*
Universidad de Burgos, Spain and Universitá di Firenze, Sesto Fiorentino, Italy
25 May 2009 (online)
A synthesis of β-turn mimetic 5-oxobenzo[e][1,4]diazepine-3-carboxamides is initiated by an Ugi reaction between arylglyoxals, para-substituted benzylamines, cyclohexyl isocyanide, and 2-azidobenzoic acid. The Ugi products undergo a Ph3P-mediated Staudinger-aza-Wittig cyclization to afford the benzodiazepines. The Ugi reaction proceeds in mediocre to good yields and the cyclization in good to excellent yields. The substrate scope was well studied with regard to the arylglyoxals and benzylamines, but not with respect to the isocyanide and azido benzoic acid.