Tetrafluoroboric Acid Adsorbed on Silica Gel as a Reusable Heterogeneous Dual-Purpose Catalyst for Conversion of Aldehydes/Ketones into Acetals/Ketals and Back Again
作者:Asit Chakraborti、Dinesh Kumar、Raj Kumar
DOI:10.1055/s-2008-1042940
日期:2008.4
hydes/ketones are regenerated from the corresponding acetals/ ketals in high yields by the treatment with water-alcohol in the pres- ence of HBF4-SiO2 at room temperature for short times. Excellent selectivity was observed during inter- and intramolecular competi- tion studies involving carbonyl substrates with varying electronic and steric environments. Selective acetalformation of benzalde- hyde takes
Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for acetal formation
作者:Raj Kumar、Asit K. Chakraborti
DOI:10.1016/j.tetlet.2005.09.168
日期:2005.11
Commercially available copper(II) tetrafluoroborate hydrate has been found to be a highly efficient catalyst for dimethyl/diethyl acetal formation in high yields from aldehydes and ketones by reaction with trimethyl/triethyl orthoformate at room temperature and in short period. Acetalisation was carried out under solvent-free conditions with electrophilic aldehydes/ketones. For weakly electrophilic
A mesoporous aluminosilicate (Al-MCM-41) was found to be an effective heterogeneous catalyst for the reaction of both aldehydes and acetals with silylenolethers or ketene silylacetals to give the corresponding aldol adducts in moderate to high yields. The remarkable high catalytic activity of Al-MCM-41 over amorphous silica-alumina and aluminum-free mesoporous silicate was observed in the reaction
Perchloric Acid Adsorbed on Silica Gel (HClO<sub>4</sub>-SiO<sub>2</sub>) as an Inexpensive, Extremely Efficient, and Reusable Dual Catalyst System for Acetal/Ketal Formation and Their Deprotection to Aldehydes/Ketones
作者:Asit Chakraborti、Raj Kumar、Dinesh Kumar
DOI:10.1055/s-2006-958948
日期:2007.1
Perchloric acid adsorbed on silicagel (HClO 4 -SiO 2 ) is reported as extremely efficient, inexpensive, and reusable catalyst for dual role for protection of aldehydes/ketones (with trialkyl orthoformates) as acetals/ketals and deprotection (with water-alcohol) to regenerate the carbonyl compounds in high yields at room temperature and in short times. Acetalization/ketalization of electrophilic aldehydes/ketones
A new generation of aprotic yet Brønsted acidic imidazolium salts: low toxicity, high recyclability and greatly improved activity
作者:Lauren Myles、Rohitkumar G. Gore、Nicholas Gathergood、Stephen J. Connon
DOI:10.1039/c3gc40975a
日期:——
Catalysts which have low antimicrobial toxicity and are aprotic, yet which can act as Brønsted acidic catalysts in the presence of protic additives have been developed. The catalysts are recyclable, considerably more active (i.e. can be used at 10–50 times lower loadings) and of broader scope than their antecedent generation.