Ligand Relay Catalysis Enables Asymmetric Migratory Reductive Acylation of Olefins or Alkyl Halides.

Design of ligands in transition-metal catalyzed reactions is challenging, especially in asymmetric transformations. With each step in the catalytic cycle promoted by its privileged ligand and different steps well-connected by dynamic ligand exchange, synergistic combination of multiple ligands could potentially enhance the catalytic efficiency and selectivity. Now, this concept has been applied to the NiH-catalyzed asymmetric remote hydroacylation of olefins and migratory acylation of alkyl halides with excellent regio- and enantioselectivity, utilizing two simple ligands, one for chain-walking and the other for asymmetric acylation. Starting from abundant alkenes/alkyl halides and carboxylic acids, a wide range of enantioenriched chiral α-aryl ketones can be efficiently accessed under mild conditions.

Atroposelective Access to Oxindole-Based Axially Chiral Styrenes via the Strategy of Catalytic Kinetic Resolution.

Atroposelective synthesis of axially chiral molecules has attracted substantial attention from chemists because of the importance of such molecules. However, catalytic asymmetric synthesis of axially chiral styrenes or vinyl arenes is underdeveloped and challenging due to the low rotational barrier and weak configurational stability of such molecules. Therefore, the development of powerful strategies for the catalytic atroposelective synthesis of axially chiral styrenes or vinyl arenes is of great importance. In this work, we have accomplished the first atroposelective access to oxindole-based axially chiral styrenes by the strategy of catalytic kinetic resolution, and this strategy offered two kinds of oxindole-based axially chiral styrene derivatives in good diastereoselectivities (up to 94:6 dr) and excellent enantioselectivities (up to 98% ee) with high selectivity factors (S up to 106). This strategy not only provides easy access to oxindole-based axially chiral styrenes but also offers a robust method for synthesizing bisamide derivatives bearing both axial and central chirality. More importantly, this strategy has added a new class of members to the atropisomeric family, especially to the family of axially chiral styrenes.

Organocatalytic C3-functionalization of indolizines: synthesis of biologically important indolizine derivatives.

A Brønsted acid-catalyzed C3-alkylation of indolizines has been established with different electrophiles such as ortho-hydroxybenzyl alcohols, other precursors of para-quinone methides and ortho-quinone methides, and 2-indolylmethanol as well. By using this approach, a series of C3-functionalized indolizines were synthesized in overall good yields (up to 89%). These examples demonstrate that the Brønsted acid-catalyzed C3-alkylation of indolizines has a wide applicability, which can serve as a useful method for synthesizing C3-functionalized indolizine derivatives with structural diversity. This reaction has fulfilled the task of developing organocatalytic C3-functionalization of indolizines for the synthesis of biologically important indolizine derivatives.

Design and Catalytic Asymmetric Construction of Axially Chiral 3,3'-Bisindole Skeletons.

The first catalytic asymmetric construction of 3,3'-bisindole skeletons bearing both axial and central chirality has been established by organocatalytic asymmetric addition reactions of 2-substituted 3,3'-bisindoles with 3-indolylmethanols (up to 98 % yield, all >95:5 d.r., >99 % ee). This reaction also represents the first highly enantioselective construction of axially chiral 3,3'-bisindole skeletons, and utilizes the strategy of introducing a bulky group to the ortho-position of prochiral 3,3'-bisindoles. This reaction not only provides a good example for simultaneously controlling axial and central chirality in one operation, but also serves as a new strategy for catalytic enantioselective construction of axially chiral 3,3'-bisindole backbones from prochiral substrates.