Application of Indium Chloride as Catalyst in Organic Synthesis Reactions
Datta M. ChemistrySelect, 2021, 6(2), 187-216.
Indium chloride (InCl3) plays an important role as a catalyst in various organic synthesis reactions, including multicomponent C-C and C-N bond formation reactions, activation of C-C multiple bonds, carbocation formation, Aza-Diels-Alder reaction, dehydration reaction, coupling reaction, 1,3-dipolar cycloaddition reaction, etc. Here are just a few examples:
· Multicomponent C-C and C-N bond forming reactions: Sridharan et al. invented one pot three-component strategy for the synthesis of bicyclic compounds containing nitrogen atom such as bridged tetrahydroquinolines derivatives 4 bearing a 2,6-methanobenzo[d][1,3]diazocine fragment by the reaction between a primary amines 1, β-ketoesters 2 and ortho-amino α,β-unsaturated aldehydes 3 in the presence of 10 mol% InCl3 in methanol at 65°C with 65-87% yield.
· InCl3 Catalyzed activation of C C triple bond: Nitrogen containing heterocycles such as quinoxalines 61 which are basically 1,4-diazines and quinolin-8-amine derivatives 62 were synthesized from ortho-amino N-propargylaniline compounds 60 catalyzed by InCl3 via intramolecular cyclization under aerobic condition in isopropanol at room temperature was observed.
Indium(III) Chloride As A Highly Chemoselective Thioacetalization Catalyst
Muthusamy S, et al. Tetrahedron Letters, 2001, 42(2), 359-362.
Indium (III) chloride (InCl3) can be used as a catalyst for the synthesis of 1,3-dithiolanane with effectiveness and high selectivity. Furthermore, indium (III) chloride serves as a catalyst for the mild and highly chemoselective thioacetalization of carbonyl compounds.
· When a solution of p-methoxybenzaldehyde, 1.1 equivalents of 1,2-ethanedithiol and 0.3 equivalents of anhydrous indium(III) chloride in dry dichloromethane was stirred at 25°C under an argon atmosphere for 15 min, thioacetal 1 was produced12 and isolated in 92% yield.
· Enolizable ketones like ethyl acetoacetate under the same reaction conditions with indium(III) chloride as the catalyst for 5 hours were converted to the corresponding thioacetal, e.g. 4, in 74% yield.
· Even an oxa-bridged compound was converted into the corresponding 1,3-dithiolane derivative 5 in good yield.
· Alicyclic ketones like 2-carbethoxy2-methylcyclohexanone, ethyl 2-(2-oxocyclohexane)- acetate; a,b-unsaturated ketones like benzylidene tetralone and (E)-4-phenyl-3-buten-2-one in the presence of 1,2-ethanedithiol with indium(III) chloride as a catalyst were converted to the corresponding dithiolanes 6-9 in good yields, respectively.
Synthesis of 5-Substituted 1H-Tetrazoles Catalyzed by Indium (III) Chloride from Oximes and Sodium Azide
Guggilapu S D, et al. Synlett, 2016, 27(08), 1241-1244.
Indium (III) chloride (InCl3), as a Lewis acid catalyst, can catalyze the synthesis of 5-substituted 1H-tetrazole derivatives from various oximes and sodium azide. This method has significant advantages such as cheap catalyst, low catalyst loading, mild reaction conditions, and simple experimental steps.
General procedure based on indium chloride catalysis
· InCl3 (3 mol%) was added to a stirred solution of the appropriate aldoxime (1 mmol) and NaN3 (1.5 mmol) in DMF (5 mL), and the mixture was heated to 120 °C.
· When the reaction was complete (TLC), the mixture was cooled to r.t., H2O (5 mL), 2 M aq HCl (10 mL), and EtOAc (10 mL) were successively added, and the mixture was stirred vigorously for 15 min.
· The organic layer was separated, and the aqueous layer was extracted with EtOAc (3 × 15 mL). The combined organic extracts were washed with H2O, dried (Na2SO4), and filtered.
· The solvent was evaporated under reduced pressure, and the crude product was purified by column chromatography [silica gel, EtOAc-hexane (9:1)].
Download
