InCl3: A mild Lewis acid but efficient reagent in organic synthesis

Abstract

An efficient, mild and highly chemoselective thioacetalization of carbonyl compounds using InCl3 as the catalyst was developed. Treatment of tri-O-acetyl-D-glucal with various alcohols and phenols in the presence of InCl3/DCM at ambient temperature gave the corresponding alkyl aryl 2,3-unsaturated glycopyranosides in excellent yields with good anomeric selectivity. A simple and efficient procedure for the rearrangement of substituted epoxides catalyzed by InCl3 was developed and selectivity was observed in the case of aryl-substituted epoxides. InCl3 (20 mol%) in nitromethane permits ionic Diels-Alder reaction of a variety of 2,3-olefinic acetals to form the respective cycloadducts in good yields with good endo selectivity. The direct aldol reactions of various ketones with glyoxylic and glyloxylates in the presence of InCl3 afforded the α-hydroxy acid and α-hydroxy esters in good yields with high regioselectivities. The reduction of a wide range of acid chlorides to the corresponding aldehydes was carried out using indium trichloride in the presence of triphenylphosphene. The ring opening of α,β-epoxycarboxylic acids by bromide and iodide ions has been efficiently carried out in water in a high regio-and stereoselective fashion in the presence of indium trichloride as catalyst.