Atom‐economical Approaches to 1,5‐Benzodiazepines Containing Indole Ring via Fe₃O₄@SiO₂‐PTSA‐catalyzed Multi‐component Domino Reactions

Abstract

Four novel atom-economical approaches for synthesis of 1,5dihydrospiro[benzo[b][1,4]diazepine-2,3'-indole] compounds via three-component or four-component domino reactions have been developed in the presence of a catalytic amount of magnetic nanoparticles (Fe 3 O 4 @SiO 2-PTSA) in ethanol, which provide an efficient one-pot synthesis of 1,5-benzodiazepines with multi-ring system and functional groups containing indole, aryl, ester, acyl and alkyl groups in excellent yields. In a one-pot operation, two new nitrogen heterocycle (indole and diazepine) rings and four new chemical bonds (one CÀ C, two CÀ N and one C=C) were constructed by series of domino reactions. Furthermore, plausible catalytic synthesis reaction mechanisms have been proposed. The advantages of these methods are the green reaction process, the recyclable magnetic catalyst, mild reaction conditions, short reaction time and high yields of products.

Decade Advance of Isatin in Three‐component Reactions

“…Imine intermediates would be activated by the chiral phosphoric acids via hydrogen bonds. The Wang group [16c] described a similar reaction by using Fe 3 O 4 @SiO 2 ‐PTSA as the catalyst. Pardasani group [16d] reported the solvent‐free synthesis of spiro‐benzimidazoquinazolinones from reactions of 2‐aminobenzimidazole.…”

Synthetic aspects of 1,4- and 1,5-benzodiazepines usingo-phenylenediamine: a study of past quinquennial

“…Zhang et al 89 reported three different three-component reactions for the synthesis of 1,5-BZDs ( 33 ) containing a indole ring introduced by Fe 3 O 4 @SiO 2 -PTSA as a magnetic nanocatalyst in EtOH. All reactions involved two common components, namely, OPD ( 1 ) and isatin ( 30 ), but the third component was ethyl acetoacetate ( 31 ) or 3-butyne-2-one ( 32 ) or benzoylacetone ( 14 ) and gave product ( 33 ).…”

“…Zhang and colleges 89 developed an efficient method for the synthesis of BZDs ( 33 ) using substituted OPD ( 1 ), N , N -dimethylformamide dimethylacetal ( 44 ), aromatic acetone ( 10 ) and isatin ( 30 ) in ethanol at reflux to RT. The authors obtained 10 new compounds ( 33 ) in 5–12 h in 79–90% yield using various aromatic ketones and substituted OPD.…”

NiFe2O4@SiO2@PrNH2–DPA–CeCl3: a cerium-based magnetic nano dual-acid catalyst with high efficacy and recyclability for domino sequential synthesis of lactam ring-fused 1,5-benzodiazepines

“…This step is generally realized in the presence of a catalyst. A large number of synthetic methodologies for 1,5-benzodiazepines in the existence of distinct single-acid catalysts, such as trifluoroacetic acid, 29,30 p -toluenesulfonic acid, 31–33 polyphosphoric acid, 34 heteropoly acids, 35,36 Ce(OTf) 3 (ref. 37) and Cu(OAc) 2 (ref.…”