Xing-Feng Bai

Aromatic Amide‐Derived Non‐Biaryl Atropisomers as Highly Efficient Ligands in Silver‐Catalyzed Asymmetric Cycloaddition Reactions

The synthesis of a series of aromatic amide-derived non-biaryl atropisomers with a phosphine group and multiple stereogenic centers is reported. The novel phosphine ligands exhibit high diastereo- and enantioselectivities (up to >99:1 d.r., 95-99u2009% ee) as well as yields in the silver-catalyzed asymmetric [3+2] cycloaddition of aldiminoesters with nitroalkenes, which provides a highly enantioselective strategy for the synthesis of optically pure nitro-substituted pyrrolidines. In addition, the experimental results with regard to the carbon stereogenic center as well as the amide stereochemistry confirmed the potential of hemilabile atropisomers as chiral ligand in catalytic asymmetric [3+2] cycloaddition reaction.

Fei-Phos ligand-controlled asymmetric palladium-catalyzed allylic substitutions with structurally diverse nucleophiles: scope and limitations

To shed light on the scope and limitations of palladium-catalyzed allylic alkylation in the presence of chiral trans-1,2-diaminocyclohexane-derived Fei-Phos as an effective phosphine ligand, the asymmetric palladium-catalysed alkylation of structurally diverse hard/soft nucleophiles, including allylic etherification of alcohols and the allylic alkylation of activated methylene compounds, indoles, and aromatic amines were investigated in this study; the corresponding products with various functional groups were achieved in good yield and with high enantioselectivity (up to 99% ee).

A d‐Camphor‐Based Schiff Base as a Highly Efficient N,P Ligand for Enantioselective Palladium‐Catalyzed Allylic Substitutions

New Schiff bases derived from chiral d‐camphor were determined to be effective phosphine ligands for the asymmetric palladium‐catalyzed allylic alkylation of activated methylene compounds, the allylic etherification of alcohols, and the allylic amination of primary amines or secondary amines, in which the corresponding products with various functional groups were achieved in good yields with excellent enantioselectivities (up to >99u2009%u2009ee). Remarkably, the palladium catalyst derived from Schiff base L2 afforded the highest level of enantioselectivity reported to date for allylic substitution reactions, including allylic etherification and allylic amination, which revealed the privileged role of d‐camphor‐derived Schiff bases in palladium‐catalyzed allylic substitution reactions.

Asymmetric Michael Addition of Aldimino Esters with Chalcones Catalyzed by Silver/Xing-Phos: Mechanism-Oriented Divergent Synthesis of Chiral Pyrrolines

The mechanism-oriented reaction design for the divergent synthesis of chiral molecules from simple starting materials is highly desirable. In this work, aromatic amide-derived nonbiarylatropisomer/silver (silver/Xing-Phos) complex was used to catalyze the Michael addition of glycine aldimino esters to chalcones and successfully applied to the subsequent cyclocondensation to afford substituted cis-Δ(1)-pyrroline derivatives with up to 98u2009%u2005ee. Besides the inherent performance of the chiral Ag/Xing-Phos catalyst system, it was found that the workup of such reactions played an important role for the stereoselective construction of stereodivergent Δ(1)-pyrrolines, in which an epimerization of the cis-Δ(1)-pyrrolines to the trans-isomers during was revealed.

Enantioselective conjugate addition of cyanide to chalcones catalyzed by a magnesium-Py-BINMOL complex

An enantioselective magnesium-catalyzed conjugate addition of trimethylsilyl cyanide to chalcones in the presence of Py-BINMOL with multiple stereogenic centers, through dual activation of substrates, has been successfully developed with moderate to good enantioselectivities and in good yields.

Silicon‐Based Bulky Group‐Induced Remote Control and Conformational Preference in the Synthesis and Application of Isolable Atropisomeric Amides with Secondary Alcohol or Amine Moieties

Remote stereocontrol through conformational transmission along a carbon chain is highly important in synthetic systems and molecular architectures. In this work, the interactional reactivity between a remote silicon-based bulky group and an O-/N-containing functional group has been revealed and determined by lateral lithiation-substitution, desilylation, as well as desilylation-olefination with benzaldehyde. The results suggest considerable information transmission and steric hindrance that can be exploited for the controllable synthesis of atropisomeric molecules. Based on the remote steric effect of a functional group across the aromatic ring of an amide, the construction of isolable atropisomeric amides with functional groups, such as alcohol, amine, and olefin was successfully achieved. All these new atropisomers were obtained in reasonable yield in pure diastereomeric form, and the specific configuration of representative products was confirmed by X-ray crystallography.

Asymmetric Synthesis of Glutamic Acid Derivatives by Silver-Catalyzed Conjugate Addition–Elimination Reactions

The enantioselective construction of a family of chiral glycine-derived aldimino esters is described. The asymmetric tandem conjugate addition-elimination procedure is characterized by its exceptional mild reaction conditions and features with an exquisite enantioselectivity profile using commercially available silver/DTBM-SegPhos catalyst, allowing for the facile preparation of a variety of substituted and chiral glutamic acid derivatives (up to 99% ee) bearing Schiff base in a straightforward manner.

Lewis‐Base‐Mediated Diastereoselective Silylations of Alcohols: Synthesis of Silicon‐Stereogenic Dialkoxysilanes Controlled by Chiral Aryl BINMOLs

In the past years, stereoselective functionalizations of hydroxyl groups of alcohol substrates with chlorosilanes leading to silyl ether formation have evolved from a functional-group protection to an enantioselective synthetic strategy. This work comprises a controlled desymmetrization of dichlorosilanes by using a family of structurally specific chiral diols, chiral 1,1-binaphthalene-2-α-arylmethanol-2-ol (Ar-BINMOL). This process led to the facile construction of silicon-stereogenic organosilicon compounds with high yields and good diastereoselectivities. In addition, the diasteroselective silylation of chiral diols might not only be of interest for the development of highly stereoselective nucleophilic silylation, but also shed light on the construction of novel chiral phosphine ligands bearing a silicon-stereogenic center.

Ligand-Controlled Inversion of Diastereo- and Enantioselectivity in Silver-Catalyzed Azomethine Ylide–Imine Cycloaddition of Glycine Aldimino Esters with Imines

A highly diastereo- and enantioselective silver-catalyzed azomethine ylide-imine (AYI) cycloaddition reaction of glycine aldimino esters with imines was developed in which the Xing-Phos-controlled syn-selective or DTBM-Segphos-induced anti-selective AYI cycloaddition reaction could be applied to the synthesis of a variety of stereodivergent 1-alkyl-2,5-substituted imidazolidines with high yields and excellent enantioselectivities (up to 99% ee) as well as good diastereoselectivities (up to 99:1 dr) under mild reaction conditions.

A mechanistic study on multifunctional Fei-Phos ligand-controlled asymmetric palladium-catalyzed allylic substitutions

To shield light on the mechanism of palladium-catalyzed allylic substitutions with structurally diverse nucleophiles (up to 99% ee) in the presence of Fei-Phos ligand (chiral trans-1,2-diaminocyclohexane-derived biphosphine, CycloN2P2-Phos) as an effective chiral P-ligand, mechanistic studies were performed for clarification of the role of multifunctional Fei-Phos in this reaction. The cooperative action of nitrogen and phosphorous atoms in the present Pd-catalyzed allylic alkylation is proved to be a diphosphine-based catalyst system but not a nitrogen-controlled or monophosphine-involved transition state.