TCT as a Rapid and Efficient Catalyst for the Synthesis of 1,5-Benzodiazepines

Abstract

compared with DMF, DMSO, MeOH, CH2Cl2, CHCl3 and toluene based on reaction time and yield. Then, the ability of o-phenylenediamines and different ketones as precursors in one-pot 1,5-benzodiazepines synthesis was considered and the results were summarized in Table 1. Cyclic ketone as well as acyclic ketones took part in this condensation reaction in good yields at room temperature. These reactions were carried out within 15-30 min. The reaction in the absence of TCT under similar conditions proceeded sluggishly. The proposed mechanism of this reaction has been shown in Scheme 2. The amine of o-phenylenediamine is first activated by TCT and then attacks the carbonyl group of the ketone, giving intermediate diimine. A 1,3-shift of the hydrogen attached to the methyl group then occurs to form enamine which cyclized to afford the seven member ring. 1,5-Benzodiazepines were efficiently and conveniently synthesized from o-phenylenediamines and different ketones in the presence of catalytic amounts of TCT in acetonitrile at room temperature. Short reaction time, high yields, mild reaction conditions, use of inexpensive and stable catalyst are other advantages. Experimental