Enantioselective Construction of Vicinal Diaxial Styrenes and Multiaxis System via Organocatalysis

Enantioselective Construction of Axially Chiral Amino Sulfide Vinyl Arenes by Chiral Sulfide-Catalyzed Electrophilic Carbothiolation of Alkynes

The enantioselective construction of axially chiral compounds by electrophilic carbothiolation of alkynes is disclosed for the first time. This enantioselective transformation is enabled by the use of a Ts-protected bifunctional sulfide catalyst and Ms-protected ortho-alkynylaryl amines (Ts=tosyl; Ms=mesyl). Both electrophilic arylthiolating and electrophilic trifluoromethylthiolating reagents are suitable for this reaction. The obtained products of axially chiral vinyl-aryl amino sulfides can be easily converted into biaryl amino sulfides, biaryl amino sulfoxides, biaryl amines, vinyl-aryl amines, and other valuable difunctionalized compounds.

Origin and stabilization of axial chirality in the construction of naphthyl-C2-indoles: a DFT study

A novel method for predicting the stabilization of axial chirality in the construction of naphthyl-C2-indoles has been suggested for the first time.

Silver-Catalyzed Nitration/Annulation of α-Alkynyl Arylols toward 3-Nitrated Benzofurans

A silver-catalyzed nitration/annulation of α-alkynyl arylols is reported by using tert-butyl nitrite (TBN) as a NO₂ radical precursor, from which a set of 3-nitrated benzofurans were synthesized with moderate to good yields. This transformation initiated by an in situ generated NO₂ radical proceeds efficiently under mild and neutral redox conditions, which provides a new pathway toward the 3-nitrobenzofuran framework via catalytic difunctionalization of internal alkynes.

Bidirectional enantioselective synthesis of bis-benzofuran atropisomeric oligoarenes featuring two distal C-C stereogenic axes

We report the bidirectional enantioselective synthesis of bis-benzofuran atropisomeric oligoarenes featuring two distal C–C stereogenic axes. These are controlled by a two-fold central-to-axial chirality conversion upon oxidative aromatization.

We report the bidirectional enantioselective synthesis of bis-benzofuran atropisomeric oligoarenes featuring two distal C–C stereogenic axes obtained by a two-fold central-to-axial chirality conversion upon oxidative aromatization. The key enantioenriched centrally chiral bis-dihydrobenzofuran precursors were synthesized via a bidirectional diastereo- and enantio-selective organocatalyzed domino reaction between simple achiral and easily accessible dihydroxylated aromatics and chloronitroalkenes. Moreover, the stereodivergent nature of the methodology was established by synthesizing both diastereomers of a non-symmetrically functionalized bis-axially chiral oligoarene.

Enantioselective Control of Both Helical and Axial Stereogenic Elements though an Organocatalytic Approach

A highly diastereo- and enantio-selective method for the asymmetric synthesis of molecules containing helicenes and stereogenic axes was developed based on organocatalysis. Various compounds bearing both helical and axial stereogenic elements were obtained in excellent enantioselectivities. The mechanism study revealed that the reaction proceeded through two stages: 1) The first cyclization produces a reaction intermediate containing a stereogenic axis. 2) The dynamic kinetic resolution of helix reaction intermediate following with cyclization generates a helix and another stereogenic axis.

Enantioselective organocatalytic activation of vinylidene-quinone methides (VQMs)

Vinylidene-quinone methides (VQMs) are highly electrophilic chiral reagents that can be generated in situ from 2-(phenylethynyl)phenols. They were characterized for the first time in 2012 but their enantioselective organocatalytic activation was addressed only very recently. Their specific reactivity has revealed innovative strategies notably for the control of axial chirality.

Conversion of two stereocenters to one or two chiral axes: atroposelective synthesis of 2,3-diarylbenzoindoles

Central-to-axial chirality conversion provides efficient access to axially chiral compounds, and several examples regarding the conversion of one, two or four stereocenters to one axis have been reported. Herein, we report the conversion of two stereocenters to one or two chiral axes for the first time. In this study, a new class of enantiomerically enriched 2,3-diarylbenzoindoles was efficiently synthesized using a chiral phosphoric acid-catalyzed [3 + 2] formal cycloaddition and a mild DDQ oxidation strategy. Moreover, a speculative model of the central-to-axial chirality conversion outcome was proposed based on preliminary mechanistic studies and DFT calculations. Potentially, using this strategy, useful chiral phosphine ligand can be synthesized smoothly (99% ee).

An Atropo-enantioselective Synthesis of Benzo-Linked Axially Chiral Indoles via Hydrogen-Bond Catalysis

A variety of axially chiral biaryldiols were synthesized in good yields with excellent atropo-enantioselectivities through construction of axially chiral indoles catalyzed by asymmetric hydrogen-bond donors. In addition, the new axially chiral compounds were proved to be efficient and practical catalysts for asymmetric catalysis. The strategy not only provides a novel method to synthesize axially chiral compounds but also extends the scope of chiral catalysts.

Crystal structure of bis(μ-{2-[(5-bromo-2-oxido-benzyl-idene)amino]-eth-yl}sulfanido-κ3 N,O,S){2,2'-[(3,4-di-thia-hexane-1,6-di-yl)bis-(nitrilo-methanylyl-idene)]bis-(4-bromo-phenolato)-κ4 O,N,N',O'}dicobalt(III) di-methyl-formamide monosolvate

The title binuclear CoIII complex, [Co2(C9H8BrNOS)2(C18H16Br2N2O2S2)]·C3H7NO, with a Schiff base ligand formed in situ from cyste-amine (2-amino-ethane-thiol) and 5-bromo-salicyl-aldehyde crystallizes in the space group P21. It was found that during the synthesis the ligand undergoes spontaneous oxidation, forming the new ligand H2 L' having an S-S bond. Thus, the asymmetric unit consists of one Co2(L)2(L') mol-ecule and one DMF solvent mol-ecule. Each CoIII ion has a slightly distorted octa-hedral S2N2O2 coordination geometry. In the crystal, the components are linked into a three-dimensional network by several S⋯ Br, C⋯ Br, C-H⋯Br, short S⋯C (essentially shorter than the sum of the van der Waals radii for the atoms involved) contacts as well by weak C-H⋯O hydrogen bonds. The crystal studied was refined as an inversion twin.

Direct Access to Alkylideneoxindoles via Axially Enantioselective Knoevenagel Condensation

The organocatalytic axially enantioselective Knoevenagel condensation between prochiral cyclohexanones and oxindoles is presented. The reaction, promoted by a primary amine, proceeded smoothly and furnished unprecedented examples of novel cyclohexylidene oxindoles displaying axial chirality.

Completely regioselective insertion of unsymmetrical alkynes into electron-deficient alkenes for the synthesis of new pentacyclic indoles

A Lewis acid catalyzed insertion of unsymmetrical alkynes into electron-deficient alkenes has been reported for the first time, leading to 34 examples of hitherto unreported pentacyclic benzo[5,6]chromeno[2,3-b]indoles.

Enantioselective aryl–aryl coupling facilitated by chiral binuclear gold complexes

The first example of highly enantioselective aryl–aryl coupling mediated by chiral gold complexes is reported.