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| PAPER | Synthesis 2007: 299-303
DOI: 10.1055/s-2006-958948 |
© Georg Thieme Verlag Stuttgart · New York
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Perchloric Acid Adsorbed on Silica Gel (HClO4-SiO2) as an Inexpensive, Extremely Efficient, and Reusable Dual Catalyst System for Acetal/Ketal Formation and Their Deprotection to Aldehydes/Ketones
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| Raj Kumar, Dinesh Kumar, Asit K. Chakraborti* |
National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar, Punjab 160062, India
Fax: +91(172)2214692; e-Mail: akchakraborti@niper.ac.in;
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Received
6 October 2006 |
Abstract
Perchloric acid adsorbed on silica gel (HClO4-SiO2) 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 was carried out under solvent-free conditions. Weakly electrophilic aldehydes/ketones and aldehydes having a substituent that can coordinate with the catalyst, required the corresponding alcohol as solvent. Key words
acetals - ketals - aldehydes - ketones - trimethyl orthoformate (TMOF) - triethyl orthoformate (TEOF) - protection/deprotection - HClO4-SiO2 - dual catalyst
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