Journal of Molecular Catalysis A: Chemical 259 (2006) 201–204 Short communication Catalytic synthesis of 2,3-dihydro-1H-1,5-benzodiazepines by ferric perchlorate Majid M. Heravi ∗ , Vahideh Zadsirjan, Farahnaz K. Behbahani, Hossien A. Oskooie Department of Chemistry, School of Sciences, Azzahra University, Vanak, Tehran, Iran Received 17 May 2006; received in revised form 6 June 2006; accepted 7 June 2006 Available online 25 July 2006 Abstract 2,3-Dihydro-1H-1,5-benzodiazepines are synthesized by the condensation of o-phenylendiamine and various ketones in the presence of Fe(ClO 4 ) 3 . © 2006 Elsevier B.V. All rights reserved. Keywords: Ferric perchlorate; 1,5-Benzodiazepines; o-Phenylenediamine; Ketones 1. Introduction Benzodiazepines are interesting compounds because they belong to an important class of the pharmacologically pre- eminent 1,5-benzodiazepines which have been extensively used as anticonvulsant, antianxiety, analgesic, sedative, antidepres- sive, hypnotic and anti-inflammatory agents [1–4]. Additionally, they are useful synthons for the synthesis of various fused-ring compounds such as triazolo-, oxazino-, oxadiazolo- and furano- benzodiazepines [5]. Due to their wide range of pharmacological activity, synthetic and industrial applications, the synthesis of these compounds has recently received a great deal of attention for the discovery of improved protocols towards milder and high yielding approaches. A variety of catalysts such as BF 3 ·OEt 2 [6], NaBH 4 [7], PPA-SiO 2 [8], MgO–POCl 3 [9], Yb(OTf) 3 [10], Al 2 O 3 –P 2 O 5 [11], HOAc-microwave [12], SO 4 -2 –ZrO 2 [13], I 2 [14], InBr 3 [15], Ag 3 PW 12 O 40 [16],[l-proline] 2 Zn [17], solid acid [18] and ionic liquids [19,20] have been employed to affect this transformation. However, many of these methods are associated with several drawbacks such as applications of expensive reagents, dras- tic reaction conditions, extended reaction times, occurrence of side products, unsatisfactory yields and complicated experimen- tal procedure. Hence, there is a need to develop a convenient, ∗ Corresponding author. Tel.: +98 9121329147; fax: +98 218047861. E-mail address: mmh1331@yahoo.com (M.M. Heravi). efficient and practically useful process for the synthesis of 1,5- benzodiazepines. Recently we have used ferric perchlorate as a versatile catalyst in organic synthesis [21–24]. Due to inter- esting application of 1,5-benzodiazepines and in continuation of our interest in heterocyclization [25] and catalytic reac- tions [26] in this communication we report our results for the synthesis of 1,5-benzodiazepines using ferric perchlorate as a catalyst. 2. Results and discussion The scope and generality of the above process is illustrated with respect to the reactions of different o-phenylenediamines and a wide range of ketones (Table 1). The reactions were carried out at room temperature for 15–35 min by taking a 1:2.5 mol ratio mixture of o-phenylenediamine and the ketone in the presence of 2 mol% Fe(ClO 4 ) 3 in solvent-free condition to give the desired products (Scheme 1) in excellent yields. Both aromatic and aliphatic ketones equally underwent the conversion well. However, the ketones should contain at least -hydrogen. Cyclic ketones such as cyclohexanone afforded fused-ring 1,5-benzodiazepines (entries: 3, 9). It is noteworthy to mention that by starting from an unsymmetrical ketone such as 2-butanone (entries 2, 3), the ring closure occurs selectively only from one side of carbonyl group yielding a single product. The diamines carrying electron-donating as well as electron-withdrawing groups on the aromatic rings worked 1381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2006.06.013