Rhodium‐Catalyzed 1,4‐Addition of Lithium 2‐Furyltriolborates to Unsaturated Ketones and Esters for Enantioselective Synthesis of γ‐Oxo‐Carboxylic Acids By Oxidation of the Furyl Ring with Ozone

摘要: Rhodium-catalyzed 1,4-addition of lithium 5-methyl-2-furyltriolborate ([ArB(OCH(2))(3)CCH(3)]Li, Ar = 5-methyl-2-furyl) to unsaturated ketones give β-furyl was followed by ozonolysis the furyl ring for enantioselective synthesis γ-oxo-carboxylic acids. [Rh(nbd)(2)]BF(4) (nbd 2,5-norbornadiene) chelated with 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap) or 2,3-bis(diphenylphosphino)butane (chiraphos) gave high yields and selectivities in a range 91-99% ee at 30 °C basic dioxane/water solution. The corresponding reaction esters, such as methyl crotonate, had strong resistance under analogous conditions, but 1,4-adduct obtained 70% yield 94% ee when more electron-deficient phenyl crotonate used substrate.