Development of a C2-Symmetric Chiral aza Spirocyclic Diol

Chemodivergent and Enantioselective Synthesis of Spirobi[dihydrophenalene] Structures

The development and enantioselective synthesis of two types of C2-symmetric spirobi[dihydrophenalene] structures is reported. The reaction proceeds via rhodium-catalyzed 2-fold asymmetric conjugate arylation of dienones followed by BF3·OEt2-promoted spirocyclization to give the enantiopure spiro products. Additive-dependent chemodivergent synthesis of 3,3'-diarylated 2,2',3,3'-tetrahydro-1,1'-spirobi[phenalene]-9,9'-diols (3,3'-Ar2-SPHENOLs) and the corresponding spiro diary ethers from the same intermediate is achieved. The structural properties of 3,3'-Ph2-SPHENOL are analyzed, and its application in asymmetric catalysis has been preliminarily demonstrated.

Organocatalytic Asymmetric Construction and Application of Axially Chiral Spiro-bisindoles

Spiro skeletons have emerged as a privileged class of chiral carriers across various research fields, including asymmetric catalysis and functional materials, due to their remarkable configurational rigidity. However, limited structural diversity of spiro frameworks significantly restricts the expansion of their applications. Here we present a new class of axially chiral spiro-bisindole frameworks and report their first enantioselective construction via a chiral phosphoric acid-catalyzed intramolecular dehydrative cyclization reaction. Unlike the classical SPINOL backbone, incorporation of indole moieties in place of phenol enhances the nucleophilicity of ketone substrates, thereby eliminating the need for a tedious pre-activation process. By leveraging the retained active sites of indole, the resulting highly enantioenriched spiro-bisindoles can be rapidly transformed into other valuable structures. More importantly, axially chiral fluorescent molecules with good asymmetry factors and quantum fluorescence efficiency are readily accessed, opening a new avenue for developing chiral fluorescent materials. Control experiments demonstrate the pivotal role of both unmasked N-H bonds in achieving good efficiency and enantiocontrol.

Development and Application of SPOSiPs: A Class of Diphosphine Ligands Based on SPOSiOL

Here, we report the development and application of a novel class of spirosilacycle-based diphosphine ligands (SPOSiPs). This type of diphosphine ligand could be readily prepared in two steps with high efficiency starting from enantiopure spirobiphenoxasilin-diol (SPOSiOL). According to the structural analysis of SPOSiP and its PdCl2 complex, SPOSiPs possess a flexible chiral pocket and feature a rigid configuration, a large dihedral angle, a long P-P distance, and a large P-M-P bite angle in their metal complexes. The potentials of SPOSiPs in asymmetric catalysis have also been preliminarily disclosed.

Development of a One-Step Synthesis of oxa-Spirocyclic Diphosphine Ligands Driven by Their Application in the Industrial Synthesis of Sacubitril

Herein we have developed a highly practical and efficient one-step coupling protocol for the synthesis of chiral spiro diphosphine ligands, especially for the oxa-spiro diphosphine ligands O-SDP, which showed excellent reactivity and diastereoselectivity in the asymmetric hydrogenation of a key intermediate of Sacubitril. It should be noted that the one-step coupling protocol could be operated on a kilogram scale, and the resulting ruthenium catalyst of O-SDP could hydrogenate the key intermediate of Sacubitril on an industrial scale.

Concise synthesis and applications of enantiopure spirobiphenoxasilin-diol and its related chiral ligands

The development of chiral architectures for chiral ligand and catalyst discovery is essential for asymmetric catalysis. Herein, we report the concise synthesis of a Si-centered spirocyclic skeleton, spirobiphenoxasilin-diol (SPOSiOL), and its derived chiral ligands. Using the chemical resolution method, the optical SPOSiOL could be obtained in high yield on a gram scale. Preliminary studies indicated that this ligand scaffold has great potential in transition metal-catalyzed asymmetric reactions. This finding further highlights that the Si-centered spirocyclic scaffolds are of great value in asymmetric catalysis.

Synthesis of spiro[4.4]thiadiazole derivatives via double 1,3-dipolar cycloaddition of hydrazonyl chlorides with carbon disulfide

An operationally simple and convenient synthesis method toward a series of diverse spiro[4.4]thiadiazole derivatives via double [3 + 2] 1,3-dipolar cycloaddition of nitrilimines generated in situ from hydrazonyl chlorides with carbon disulfide has been achieved under mild reaction conditions.

Design, Synthesis, and Resolution of Spirocyclic Bisoxindole-Based C2-Symmetric Diols

A new type of spirocyclic bisoxindole-based C₂-symmetric diols (SBIDOLs) was designed and synthesized. A series of racemic SBIDOL derivatives (6a-6g) were readily synthesized from commercially available 2-halo-5-methoxyanilines 1 (X = Cl or Br) through N-mono alkylation, acylation, oxidation, double intramolecular Friedel-Crafts reaction, and demethylation reactions. The optical resolution of racemic 6b was achieved via fractional crystallization of their bis-l-menthoxycarboxylates. Further modifications of SBIDOLs were investigated, leading to 5,5'-diaryl SBIDOL derivatives (11a and 11b) through Pd-catalyzed Suzuki coupling and DM-SBIDOL 12 by Pd/C-catalyzed hydrogenative dechlorination reactions.