Indium(III) Bromide: A Novel and Efficient Reagent for the Rapid Synthesis of 1,5-Benzodiazepines under Solvent-Free Conditions

Abstract

o-Phenylenediamines (OPDA) undergo rapid condensation with ketones having hydrogens at the a-position in the presence of 10 mol% indium(III) bromide under extremely mild reaction conditions to afford the corresponding 1,5-benzodiazepines in excellent yields with high selectivity. The remarkable features of this new procedure are high conversions, short reaction times, cleaner reaction profiles, high regioselectivity in the case of unsymmetrical ketones, solvent-free conditions, and simple experimental and work-up procedures. This method works well for both electron-rich as well as electron-deficient o-phenylenediamines.

Hydrated ferric perchlorate, Fe(ClO4)3.XH2O in organic synthesis. A short review

“…A variety of catalysts such as BF 3 .OEt 2 [101], NaBH 4 [102], PPA-SiO 2 [103], MgO-POCl 3 [104], Yb(OTf) 3 [105], Al 2 O 3 -P 2 O 5 [106], HOAc-microwave [101][102][103][104][105][106][107], SO 4 2--ZrO 2 [108], I 2 [109], InBr 3 [110], Ag 3 PW 12 O 40 [111], [L-proline] 2 Zn [112], Solid acid [113] and ionic liquids [114,115] have been employed to affect this transformation. Due to interesting application of 1,5-benzodiazepines, we have recently reported a novel and efficient solvent-free process demonstrated for the synthesis of 1,5-benzodiazepines using ferric perchlorate as a catalyst (Scheme 17).…”

Synthesis of Condensed Benzo[N,N]-Heterocycles by Microwave-Assisted Solid Acid Catalysis

“…Several catalytic methods were developed for the synthesis of benzodiazepines. Catalysts include zeolites [4], InBr 3 [5], Sc(OTf) 3 [6], Yb(OTf) 3 [7], CeCl 3 /NaI [8], ionic liquids [9], and heteropoly acids [10]. In contrast, similar green catalytic methods are sporadic or nonexistent for the synthesis of benzimidazoles [11].…”

Silica supported fluoroboric acid as a novel, efficient and reusable catalyst for the synthesis of 1,5-benzodiazepines under solvent-free conditions

“…This indicates the superiority of present protocol in terms of catalyst loading and reaction time. Moreover, the triflet [21] and indium halides [22] as catalysts are expensive and economic point of view less useful for industrial applications. In addition, in case of molecular iodine [23] catalyzed synthesis of 1,5-benzodiazepine derivatives, recycling of the catalyst is not possible.…”