An efficient method for the preparation of 1,3-dithiolanes from aldehydes and ketones with 1,2-ethanedithiol in the presence of a catalytic amount of anhydrous indium(III) chloride is reported. A mild and highly chemoselective thioacetalization of carbonyl compounds using indium(III) chloride as the catalyst is also described. The desired products were obtained in 71–95% yield.
Protection of a variety of carbonyl compounds as thioacetals using indium triflate, a mild Lewis acid catalyst, was achieved at ambient temperature in very good yield. Transthioacetalization of oxyacetals into thioacetals was also achieved in an excellent yield. A mixture of carbonyl compound and its respective oxyacetal was also completely converted into thioacetal in the presence of indium triflate. (C) 2002 Elsevier Science Ltd. All rights reserved.