One-pot synthesis of 1,5-benzodiazepine-2,3-dicarboxylates via three-component domino reactions in the presence of γ-Fe2O3@SiO2/Ce(OTf)3
Novel, efficient and environmentally friendly approaches have been developed for the synthesis of 1,5-benzodiazepine-2,3-dicarboxylates by one-pot three-component domino reactions in the presence of a catalytic amount of γ-Fe 2 O 3 @SiO 2 /Ce(OTf) 3 in EtOH at ambient temperature. A total of 32 2,5-dihydro-1 H -1,5-benzodiazepine-2,3-dicarboxylates and 2-methyl-2,3-dihydro-1 H -1,5-benzodiazepine-2,3-dicarboxylates with enamine or imine structure of the heterocycle, respectively, were obtained in good yields by reacting substituted 1,2-phenylenediamine, β-carbonyl esters, and ethyl glyoxylate or ethyl pyruvate. One-pot reactions were successfully realized to form one new cycle and four new bonds (one C–C, two C–N, one C=C or two C–C, one C–N, one C=N). Furthermore, plausible mechanisms for the formation of 1,5-benzodiazepine-2,3-dicarboxylates have been proposed. The salient features of this reaction include short reaction time, mild reaction conditions, moderate to excellent yields, recyclability of the catalyst, and wide substrate scope.
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