Abstract
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°, 3° hydroxyl groups are observed.