Expedient Synthesis of High-Value Organoboronates Through Catalytic Enantioselective Alkene Functionalization

Abstract

Chapter 1 Mechanism-Based Enhancement of Scope and Enantioselectivity for Reactions Involving a Copper-Substituted Stereogenic Carbon Center: Organoborons are important building blocks of complex natural products, functional materials, and pharmaceutically relevant compounds due to their prevalent utility in C–C and C–hetero atom bond transformations. Using a readily accessible copper catalyst, we have developed highly site- and enantioselective allylic substitution by way of a threecomponent, single-vessel, and sustainable catalytic protocol. Detailed mechanistic studies revealed valuable insights which led us to develop copper–boron and copper–hydride additions to olefins with broader substrate scope, higher efficiency, and higher enantioselectivity. In addition, the method can be applied to the synthesis of biologically active molecules such as preclamol and heliespirone A and C. Chapter 2 Versatile Homoallylic Boronates by Chemo-, SN2’-, Diastereo- and Enantioselective Catalytic Sequence of Cu–H Addition to Vinyl-B(pin)/Allylic Substitution: To achieve an efficient multicomponent reaction, high chemoselectivity between a starting material and a reagent must be accomplished during the first catalytic transformation to generate an intermediate which then selectively reacts with another substrate to furnish the product in a site-, and/or stereoselective fashion. Development and application of efficient multicomponent reactions involving allylic substitution can provide alternative solutions for difficult synthetic problems in organic chemistry. Our group has developed a sulfonate-containing chiral NHC–Cu catalyzed chemo-, SN2’-, diastereo-, and enantioselective multicomponent reaction through Cu–H addition to readily available vinyl–B(pin) followed by allylic substitution to deliver homoallylic boronates. The derived homoallylic alcohols can be used as building blocks of biologically active molecules. Chapter 3 Enantioenriched Halogen-Substituted Alkenes through NHC–Cu-Catalyzed Borylation/Dehalogenation and Their Applications: Because of their unique properties, mono- and difluoroalkenes have received attention as an important class of compounds as building blocks for fluorine-containing monomers for functional polymers and biologically active molecules in medicine and agriculture. However, reported methods to prepare enantioenriched difluoroalkenes are scarce and often require undesirable amounts of precious transition metals and very high/low temperatures. To solve these challenges, we have developed a highly efficient, regio-, and enantioselective boron allylic substitution to CF3-alkenes and other halogen-substituted olefins by using an abundant copper-based catalyst.