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

Solvent-Free Syntheses of 1,5-Benzodiazepines Using HY Zeolite as a Green Solid Acid Catalyst

“…Moreover, 1,5-benzodiazepines are key synthons for the synthesis of various fused ring systems such as triazolo-, oxadiazolo-, oxazino-, or furano-benzodiazepines. − Over the past several years, considerable studies have been reported for the synthesis of 1,5-benzodiazepines utilizing ytterbium triflate, gallium­(III)­triflate, erbium­(III)­triflate, scandium­(III)­triflate, ytterbium perfluorooctanesulfonate, BF 3 -etherate, p -toulenesulfonic acid, NaBH 4 , MgO/POCl 3 , polyphosphoric acid, CeCl 3 -NaI/SiO 2 , Al 2 O 3 /P 2 O 5 , sulfated zirconia, 1,3- n -dibutylimidazolium bromide, SbCl 3 -Al 2 O 3 , iodine, magnesium perchlorate, sodium dodecyl sulfate, Ag 3 PW 12 O 40 , zinc chloride, dodecyl sulfonic acid, piperidine acetic acid, La­(NO 3 ) 3 , SmI 2 , sulfamic acid, organic acid, HClO 4 -silica, YbCl 3 , ceric ammonium nitrate, N -bromosuccinimide, acetic acid/MW, (NH 4 )­H 2 PW 12 O 40 , SnCl 2 , K10-montmorillonite, Zn-montmorillonite heterogeneous catalysts borax/phosphorus oxychloride, amberlyst-15, InBr 3 , InCl 3 , NbCl 5 , and RuCl 3 · x H 2 O as catalysts. In addition, a solvent-free procedure has been reported for the synthesis of 1,5-benzodiazepines using iodine, silver nitrate, and HBF 4 -SiO 2 as catalysts at room temperature. However, in most homogeneous catalytic systems, the main problem is to remove the catalyst after the reaction, and therefore, reusability becomes impossible.…”

Porous Silica-Based Organic-Inorganic Hybrid Catalysts: A Review

“…Nevertheless, the small pore size limits their application to certain reactions, while others require catalysts in which the active sites are accessible to bulkier molecules. To overcome the pore size limitations, inorganic acids such as polyphosphoric acid [38], perchloric acid [39], fluoroboric acid [40] and sulfuric acid [41] have been supported onto silica. Although effective in overcoming some of the limitations of microporous acid catalysts, these purely inorganic materials present little margin for modifications and fine tuning of their properties for a specific catalyzed reaction.…”

Green Synthetic Approaches for Medium Ring-Sized Heterocycles of Biological Interest

“…Several solid acid catalysts [108] such as Amberlyst [109], solid-supported fluoroboric acid [110], polyaniline sulfate [111], polystyrenesupported sulfonic acids [112], sulfated zirconia [113], and silica [114] in conjunction with other greener techniques such as MW, US, environmentally benign solvents, solvent-free conditions, and so on have been screened, evaluated, and compared with respect to yields, reaction time, reaction temperature, ease of purification, reusability, toxicity, and other hazards for sustained applications. Several solid acid catalysts [108] such as Amberlyst [109], solid-supported fluoroboric acid [110], polyaniline sulfate [111], polystyrenesupported sulfonic acids [112], sulfated zirconia [113], and silica [114] in conjunction with other greener techniques such as MW, US, environmentally benign solvents, solvent-free conditions, and so on have been screened, evaluated, and compared with respect to yields, reaction time, reaction temperature, ease of purification, reusability, toxicity, and other hazards for sustained applications.…”