Studies On The Asymmetric Oxidationby Chiral Hypervalent Iodide

The asymmetric oxidation reaction using chiral hypervalent iodide is one of the most important reactions for construction of chiral functional group in asymmetric synthesis. A series of special chiral molecules were prepared with 1ow toxicity and low cost by used chiral hypervalent iodide, which are widely used in the synthesis of chiral natural products and chiral drug molecules. In our work, a series of classical chiral iodobenzenes have been investigated to achieve the enantioselective α-oxytosylation of 2-substituted 1,3-dicarbonyl compound, aiming at finding a synthesis protocol which possessed high enantioselectivityto construct α-oxytosylatedquaternary carbon.We mainly explored the preparation of the chiral iodobenzenes and the enantioselective α-oxytosylation of 2-substituted 1,3-dicarbonyl compound catalyzed by in situ generated chiral hypervalent iodide. In these cases, we have suceessfully synthesize the C2-symmetric iodobenzenes by using ethyl L(-)-lactate as chiral source under Mitsunobu reaction. The eevalues of products were determined by High Performance Liquid Chromatography(HPLC), the optimal reaction conditions were obtained by screening the frames of chiral iodobenzenes, solvents, temperature, additives and the amount of reagents, and the substrate scopes were expanded.The experimental results indicated that the chiral C2-symmetric iodobenzenes performed high enantioselectivity for the α-oxytosylation of 1,3-dicarbonyl compound, and the best results were obtained under the conditions: the chloroform as the solvent, 10 mol% catalyst and 3.0 eq. TFA under-20 oC. Various arylsulfoacids were tolerated and transformed the desired chiral products with good ee value, and the best ee value of 69% was obtainedwhen the 4-chlorobenzenesulfonic acid was used.Our developed the α-oxytosylation of 1,3-dicarbonyl compound has advantages of nonmetal, simple operation and low cost. The α-oxytosylatedproducts are able to be transformedinto functional groups such as hydroxyl, halogen and acetoxyl et al, which have the application prospect in the organic synthesis.