Use of Montmorillonitesin organic reactions

(A) Sulfonic acid-functionalized ordered nanoporous Na+-montmorillonite (SANM), is easily prepared by the reaction of Na+-montmorillonite with chlorosulfonic acid. This reagent acts as a highly ef?cient and reusable catalyst for the chemoselective trimethylsilylation of alcohols and phenols anddeprotection of silyl ethers under mild and completely heterogeneous reaction conditions [11]. (B) Primary and secondary benzylic alcohols were oxidized to the corresponding carbonyl compounds in good to high yields by using an environmentally friendly and green oxidant (H2O2) in the presence of Montmorillonite-K10 supported manganese(II) chloride [12].(C) Various indan-1,3-dione derivatives were synthesized from the reaction of different phthalic anhydrides with diethylmalonate using montmorillonite KSF clay as a recyclable heterogeneous acidic catalyst and microwave irradiation in good yields and short reaction times[13]. (D) An e?cient green protocol for the preparation of amidoalkylnaphthols, employing a three-component one-pot condensation reaction of ?-naphthol, aromatic aldehydes and amides or urea in the presence of montmorillonite K10 clay under solvent free conditions has been described [14]. (E) Aryl imines, formed in situ from aldehydes and amines undergo smoothly nucleophilic addition with trimethylsilyl cyanide on the surface of montmorillonite KSF clay under mild reaction conditions to afford the corresponding ?-aminonitriles in excellent yields. The solid acid can be recovered and recycled in subsequent reactions with a gradual decrease of activity[15]. (F) Indoles and carbazoles on treatment with ammonium thiocyanate on montmorillonite K10 clay at 80°C furnished the corresponding 3-thiocyanato derivatives in good to high yields[16].