Triphenylphosphine-Catalyzed Dehydrogenative Coupling Reaction of Carboxylic Acids with Silanes – A Convenient Method for the Preparation of Silyl Esters
作者:Guo-Bin Liu、Hong-Yun Zhao、Thies Thiemann
DOI:10.1002/adsc.200600338
日期:2007.4.2
Triphenylphosphine has been found to be an efficient catalyst for the dehydrosilylation of carboxylic acids with silanes. In the presence of 4 mol % of triphenylphosphine (PPh3), dehydrosilylation reactions in DMF afforded the corresponding silyl esters at 120 °C in good yield.
EFFECTIVE SILYLATION OF CARBOXYLIC ACIDS UNDER SOLVENT-FREE CONDITIONS WITH <i>tert</i>-BUTYLDIMETHYLSILYL CHLORIDE (TBDMSCL) AND TRIISOPROPYLSILYL CHLORIDE (TIPSCL)
Various types of carboxylic acids can be converted effectively to their corresponding TBDMS and TIPS esters using TBDMSCI and TIPSCI in the presence of imidazole under solvent-free conditions. The advantage of this modified method in comparison with that reported by Corey is the elimination of DMF, which eliminates aqueous work-up. The method is not a time-consuming process and the reactions proceed spontaneously. By this method, absolute chemoselectivity for the protection of carboxylic acid functions in the presence of 2 degrees, 3 degrees hydroxyl groups are observed.