Oxidative Iodohydroxylation of Olefins with DMSO

Halohydrins bearing a hydroxyl and halide functional group, are privileged building blocks in organic synthesis and could be conveniently converted to other significant organic intermediates such as azidoalcohols, aminoalcohols, and epoxides, all of which are widely used in the synthesis of highly value-added chemicals. Among the approaches to halohydrins, the halohydroxylation of olefins provides a direct and efficient approach. The synthesis of bromohydrins has achieved great progress in recent years. However, the approaches to iodohydrins are still very limited. Our previous studies revealed that DMSO could oxidize halo anions to halo cations under acidic conditions. As our continuous development DMSO-based reactions, we report the iodohydroxylation of olefins by using DMSO and HI generated in situ. In this transformation, DMSO performed versatile roles as an oxidant, a solvent and an oxygen source. This reaction featured with simple operation, mild reaction condition, and wild substrate scope, and provided an efficient method to synthesize iodohydrins. Furthermore, the iodoetheration of olefins was also realized by using DMSO and alcohol as the solvent. A representative procedure for this reaction is as following: The mixture of alkene (0.5 mmol), NaI (0.6 mmol), conc. H2SO4 (1.0 mmol), DMSO (1 mL) and DCE (1 mL) were stirred at 60 degrees C under air. TCL monitor the reaction, and the product had a clear spot in phosphomolybdic acid chromogenic agent. After the reaction was completed, saturated solution of Na2S2O3 (0.5 mL) was added into the system to consume the extra I-2. After cooling down to room temperature, the mixture was diluted with water (10 mL) and extracted with ethyl acetate (10 mLx3). The combined organic extract was washed with saturated solution of NaCl (15 mL), dried over MgSO4, and evaporated in vacuo. The residue was purified by chromatography on silica gel (petroleum ether/ethyl acetate) to afford the desired product.