Design, Synthesis, and Applications of Potential Substitutes of <i>t</i>-Bu-Phosphinooxazoline in Pd-Catalyzed Asymmetric Transformations and Their Use for the Improvement of the Enantioselectivity in the Pd-Catalyzed Allylation Reaction of Fluorinated Allyl Enol Carbonates
substitutes of t-Bu-PHOX in asymmetric catalysis is reported. The design relies on the incorporation of geminal substituents at C5 in combination with a substituent at C4 other than t-butyl (i-Pr, i-Bu, or s-Bu). Most of these new members of the PHOX ligand family behave similarly in terms of stereoinduction to t-Bu-PHOX in three palladium-catalyzed asymmetric transformations. Electronically modified ligands
challenges remain for the asymmetric synthesis of tertiary α-fluoroketones, which are potentially useful molecules for the development of drugs, agrochemicals, and functional materials. Herein, we describe the development of a method for the catalytic enantioselective synthesis of tertiary α-fluoroketones via the Tsuji–Trost reaction of racemic acyclic α-fluorinated ketones. Enantioenriched acyclic α-cabonyl
Palladium-Catalyzed Enantioselective C<sub>sp<sup>3</sup></sub>–C<sub>sp<sup>3</sup></sub> Cross-Coupling for the Synthesis of (Poly)fluorinated Chiral Building Blocks
作者:Yanhui Lu、Elizabeth L. Goldstein、Brian M. Stoltz
DOI:10.1021/acs.orglett.8b02369
日期:2018.9.21
method for the enantioselective synthesis of carbo- and heterocyclic carbonyl compounds bearing fluorinated α-tetrasubstituted stereocenters using palladium-catalyzed decarboxylative allylic alkylation is described. The stereoselective Csp3–Csp3 cross-coupling reaction delivers five- and six-membered ketone and lactam products bearing (poly)fluorinated tetrasubstituted chiral centers in high yields and
描述了使用钯催化的脱羧烯丙基烷基化对映选择性合成带有氟化α-四取代立构中心的碳环和杂环羰基化合物的一般方法。立体选择性 C sp 3 –C sp 3交叉偶联反应以高产率和对映选择性产生带有(多)氟化四取代手性中心的五元和六元酮和内酰胺产物。这些氟化的、立体化学丰富的结构单元在药物化学中具有潜在价值,与传统方法相比,使用正交和对映选择性方法制备此类手性部分,通常不使用亲电子氟化试剂。
Enantioselective Pd-Catalyzed Allylation Reaction of Fluorinated Silyl Enol Ethers
An enantioselective Pd-catalyzed allylation reaction of fluorinated silyl enol ethers is reported. This reaction provides a stereoselective and efficient approach to allylated tertiary α-fluoroketones from achiral fluorinated precursors. A variety of cyclic silyl enol ether can be used, and the yields of the desired products range from 52 to 93%, and the enantiomeric excesses range from 83 to 95% ee
Unexpected effect of the fluorine atom on the optimal ligand-to-palladium ratio in the enantioselective Pd-catalyzed allylation reaction of fluorinated enol carbonates
The enantioselective Pd-catalyzed allylation reaction of fluorinated allyl enol carbonates is presented; a key feature of this transformation is the important effect of the ligand-to-palladium ratio on the enantioselectivity of the α-fluoroketones, since using a ligand excess (L/Pd ratio = 1.25 : 1) led to moderate results (30–76% ee), while using a L/Pd ratio <1 : 1.67 (to as low as 1 : 4) allowed the desired products to be obtained with high enantiopurity (up to 94% ee).