Asymmetric transformations of achiral 2,5-cyclohexadienones

Rh-Catalyzed diastereoselective desymmetrization of enone tethered-cyclohexadienones via tandem arylative cyclization

The rhodium-catalyzed arylative cyclization of enone tethered-cyclohexadienones has been developed with high efficiency, thus providing cis-fused bicyclic enones in good yields and with excellent diastereoselectivities.

Enantioselective synthesis of 3-amino-hydrobenzofuran-2,5-diones via Cu(i)-catalyzed intramolecular conjugate addition of imino esters

The copper-catalyzed enantioselective intramolecular conjugate addition of imino esters for desymmetrization of cyclohexadienones was described, providing access to enantioenriched 3-amino-hydrobenzofuran-2,5-diones.

Asymmetric construction of dihydrobenzofuran-2,5-dione derivatives via desymmetrization of p-quinols with azlactones

3-Amino-benzofuran-2,5-diones containing a chiral amino acid residue were achieved through BG-1·HBPh₄ catalyzed enantioselective Michael addition/lactonization cascade reaction of p-quinols with azlactones.

New Strategy To Access Enantioenriched Cyclohexadienones: Kinetic Resolution of para-Quinols by Organocatalytic Thiol-Michael Addition Reactions

Existing stereoselective routes to 2,5-cyclohexadienones involve either desymmetrization of an achiral substrate or have attempted to perform an asymmetric dearomatization of a phenol. Herein, we report proof-of-principle experiments aimed at developing a kinetic resolution as an alternative method for accessing enantioenriched 2,5-cyclohexadienones. More specifically, chiral bifunctional thiourea catalysts were used to promote the addition of 2-thionapthalene into unsymmetric para-quinols. The selectivity of the kinetic resolution was found to be quite sensitive to substitution around the substrate.

Asymmetric synthesis of functionalized tetrahydrofluorenones via an NHC-catalyzed homoenolate Michael addition

The first example of an N-heterocyclic carbene-catalyzed asymmetric desymmetrization of enal-tethered cyclohexadienones via an intramolecular homoenolate Michael addition/esterification reaction is described.

N-Heterocyclic carbene promoted enantioselective desymmetrization reaction of diarylalkane-bisphenols

An enantioselective NHC-catalyzed desymmetrization reaction of diarylalkane-bisphenols with aldehydes was reported under the guidance of linear free energy relationships (LFERs).

A desymmetrization-based approach to morphinans: application in the total synthesis of oxycodone

Here we report a total synthesis of the pharmacologically significant morphinan alkaloid, oxycodone.

Enantioselective nickel-catalyzed arylative intramolecular 1,4-allylations

The enantioselective desymmetrization of allenyl cyclohexa-2,5-dienones by nickel-catalyzed arylative intramolecular 1,4-allylations is described.

Iridium-Catalyzed Asymmetric Allylic Dearomatization by a Desymmetrization Strategy

A desymmetrization strategy was developed involving iridium-catalyzed allylic dearomatization of indoles. The six-membered-ring spiroindolenines contain three contiguous stereogenic centers, including an all-carbon quaternary center, and were obtained in up to 99 % yield with 99 % ee and >95:5 d.r. When treated with a catalytic amount of tosylic acid, six-membered spiroindolenine undergoes an unprecedented six-to-seven-membered ring expansion, affording the corresponding hexahydroazepino[4,5-b]indole.

Total Synthesis of (+)-Gracilamine Based on an Oxidative Phenolic Coupling Reaction and Determination of Its Absolute Configuration

The enantioselective total synthesis of (+)-gracilamine (1) is described. The strategy features a diastereoselective phenolic coupling reaction followed by a regioselective intramolecular aza-Michael reaction to construct the ABCE ring system. The configuration at C3a in 1 was controlled by the stereocenter at C9a, which was selectively generated (91 % ee) by an organocatalytic enantioselective aza-Friedel-Crafts reaction developed by our research group. This synthesis revealed that the absolute configuration of (+)-gracilamine is 3aR, 4S, 5S, 6R, 7aS, 8R, 9aS.

Two-step synthesis of chiral fused tricyclic scaffolds from phenols via desymmetrization on nickel

Tricyclic furan derivatives with multiple chiral centers are ubiquitous in natural products. Construction of such tricyclic scaffolds in a stereocontrolled, step-economic, and atom-economic manner is a key challenge. Here we show a nickel-catalyzed highly enantioselective synthesis of hydronaphtho[1,8-bc]furans with five contiguous chiral centers via desymmetrization of alkynyl-cyclohexadienone by oxidative cyclization and following formal [4 + 2] cycloaddition processes. Alkynyl-cyclohexadienone was synthesized in one step from easily accessible phenols. This reaction represents excellent chemo-selectivity, regio-selectivity, diastereo-selectivity, and enantio-selectivity (single diastereomer, up to 99% ee). An extraordinary regioselectivity in the formal [4 + 2] cycloaddition step with enones revealed the diverse reactivity of the nickelacycle intermediate. Desymmetrization of alkynyl-cyclohexadienones via oxidative cyclization on nickel was supported by the isolation of a nickelacycle from a stoichiometric reaction. Enantioenriched tricyclic products contain various functional groups such as C=O and C=C. The synthetic utility of these products was demonstrated by derivatization of these functional groups.

Tricyclic furanic compounds with multiple chiral centers are found in a variety of natural products. Here, the authors show a highly enantioselective nickel-catalyzed procedure to access tricyclic oxygen-containing scaffolds with five contiguous chiral centers.

Enantioselective desymmetrization of cyclohexadienones via an intramolecular Rauhut-Currier reaction of allenoates

The Rauhut–Currier (RC) reaction represents an efficient method for the construction of carbon–carbon bond in organic synthesis. However, the RC reactions involving allenoate substrates are very rare, and in particular, asymmetric intramolecular RC reaction of allenoates is yet to be discovered. Here, we show that the intramolecular RC reaction proceeds smoothly in the presence of 1 mol% β-ICD, and bicyclic lactones are obtained in high yields and with excellent enantiomeric excesses. With the employment of γ-substituted allenoates as racemic precursors, a novel dynamic kinetic resolution of allenes via RC reaction is observed, which allows for facile synthesis of highly enantiomerically enriched allenes.

The Rauhut-Currier reaction is a powerful method to form carbon-carbon bonds. Here, the authors report an enantioselective intramolecular variant between alkenes and allenoates, giving access to highly functionalised bicyclic lactones in excellent enantiomeric excess.

Mechanism, chemoselectivity and enantioselectivity for the rhodium-catalyzed desymmetric synthesis of hydrobenzofurans: a theoretical study

A theoretical study of Rhodium-catalyzed desymmetrization of cyclohexadienones.

Catalytic stereoselective cascade reactions of quinols with trifluoromethyl ketones: direct access to CF3-containing 1,3-dioxolanes

A general and efficient synthesis of CF₃-containing 1,3-dioxolanes using Et₃N-catalyzed ketalization/oxa-Michael cascade of quinols with trifluoromethyl ketones is described. The desired products were obtained in 68%–95% yields with acceptable diastereoselectivities.

Organocatalytic asymmetric desymmetrization of 4,4-disubstituted cyclohexadienones via an intermolecular Diels–Alder reaction

Asymmetric desymmetrization of 4,4-disubstituted cyclohexadienones via a chiral phosphoric acid-catalyzed enantioselective intermolecular Diels–Alder reaction is developed.

A short synthesis of (±)-antroquinonol in an unusual scaffold of 4-hydroxy-2-cyclohexenone

A short synthesis of the anticancer agent antroquinonol having an unusual core structure of 2,3-dimethoxy-4-hydroxycyclohex-2-enone with substituents at three contiguous stereocenters.