An efficient procedure for protection of carbonyls in Brønsted acidic ionic liquid [Hmim]BF4

Brønsted acidic ionic liquid [HMIm]BF4promoted simple and efficient one-pot green synthesis of isoxazolyl-1,3-benzoxazines at ambient temperature

“…Because of their distinct advantages, ionic liquids can make a great contribution to green chemistry. The potential of ionic liquid (IL) as green solvent has already been established in several chemical transformations (3,4). The dual role of Brønsted acidic ionic liquid [HMIm]BF 4 as green solvent and catalyst was proved in a variety of organic chemical reactions (5Á7).…”

A Fast and Highly Efficient Protocol for Synthesis of Pyrrolo[2,3-d]isoxazoles and a New Series of Novel Benzyl Bis-pyrrolo[2,3-d]isoxazoles Using Task-Specific Ionic Liquids as Catalyst and Green Solvent

“…The ionic liquid, which was remaining in the reaction flask after being washed with ethyl acetate and dried at 80°C under vacuum for 3-4 h was recycled in subsequent runs (four to five times). The structure of the products 3 were confirmed on the basis of IR, 1 H-NMR, 13 C-NMR and MS spectroscopy and finally by comparing with the authentic samples. 26) This reaction, when performed in the presence of ethanol in piperidine base as reported in literature, 26) requires 2-3 h refluxing and the yields are moderate (Entry 1-12, Table 1).…”

“…[10][11][12] Similarly, 1-methyl imidazolium tetrafluoroborates has been exploited as an efficient Bronsted acid promoter ionic liquid in various organic transformations. [13][14][15] As a part of our study on environmentally friendly organic synthesis with isoxazoles, [16][17][18][19] avoiding organic solvent and toxic catalyst in reactions, we demonstrated the use of room temperature ionic liquids as efficient catalysts as well as reaction media for Knoevenagel and Michael reactions and also for conducting reductive cyclization.Looking for a valuable procedure for the conversion of nitro styrylisoxazoles (3) to pyrrolo[2,3-d]isoxazoles (4), several approaches have been investigated. One method for pyrrole ring formation is by de-oxygenative cyclization of nitro styryl compounds using triethyl phosphite (TEP).…”

“…The products were obtained in excellent yields (80-90%) (Entry 1-8, Table 5). The structure of all the new products 5-7 were elucidated by spectroscopic (IR, 1 H-NMR, 13 C-NMR and MS) and micro analytical data.…”

Solvent-free chemoselective protection of aldehydes on the surface of alumina-sulfuric acid

“…Numerous methods for the formation of the corresponding dioxolanes (2) include acidic alumina in dry toluene (3), Ti 4' -exchanged montmorillonite (4), bismuth triflate in refluxing fluorobenzene (5), bismuth nitrate in THF (6), polyaniline-supported sulfuric acid in refluxing anhydrous toluene (7), Bronsted-acidic ionic liquid [Hmim]BF 4 (8), polymer-bound hypervalent iodine reagent under photochemical condition (9), potassium t-butoxide-promoted intramolecular reaction of chlorohydrin anions in DMF or THF (10), mesoporous aluminosilicate (11), indium triflate in refluxing alcohol or benzene (12), a combination of N-chlorosuccinimide with thiourea (13), and many others. Many of them use costly and toxic reagents, involve drastic reaction conditions and organic solvents (sometimes aromatic hydrocarbons) as reaction medium which are not very safe from environmental standpoint.…”