Construction of Distant Stereocenters by Enantioselective Desymmetrizing Carbonyl-Ene Reaction

Silver-Catalyzed Asymmetric Double Desymmetrization via Vinylogous Michael Addition of Prochiral α,α-Dicyanoalkenes to Cyclopentendiones

An asymmetric double desymmetrization methodology has been developed for synthesizing densely functionalized chiral cyclopentylcyclohexane scaffolds. We have constructed four chiral centers, including an all-carbon quaternary stereocenter in a single C-C bond formation event. The methodology has high functional-group tolerance and delivers a broad range of enantioenriched products. This vinylogous Michael addition reaction of prochiral α,α-dicyanocyclohexane to 2,2-disubstituted cyclopentene-1,3-dione is catalyzed by a chiral Ag-(R)-DTBM-SEGPHOS catalyst.

Organocatalyzed enantio- and diastereoselective isomerization of prochiral 1,3-cyclohexanediones into nonalactones bearing distant stereocenters

The lactonization of 2-(2-nitrophenyl)-1,3-cyclohexanediones containing an alcohol side chain and up to three distant prochiral elements is reported by isomerization under the mediation of simple organocatalysts such as quinidine. Through a process of ring expansion, strained nonalactones and decalactone are produced with up to three stereocenters in high er and dr (up to 99 : 1). Distant groups, including alkyl, aryl, carboxylate and carboxamide moieties, were examined.

Enantioselective Total Synthesis of [3]-Ladderanol through Late-Stage Organocatalytic Desymmetrization

Ladderane phospholipids, with their unusual ladder-like arrangement of concatenated cyclobutane rings, represent an architecturally unique class of natural products. However, despite their fascinating structure and other necessary impetus, only a few synthetic studies of these molecules have been reported so far. We have now devised a concise total synthesis of [3]-ladderanol, a component of natural ladderane phospholipids, using an organocatalytic enantioselective desymmetrizing formal C(sp² )-H alkylation. Our synthetic strategy rests on the late-stage introduction of chirality, thus allowing facile access to both enantiomers of [3]-ladderanol as well as an analogue. This is the first time a desymmetrization strategy is applied to the synthesis of [3]-ladderanol. The scope of this desymmetrizing C(sp² )-H alkylation of meso-cyclobutane-fused cyclohexenediones is also presented.

Desymmetrizing Isomerization of Alkene via Thiazolinyl Iminoquinoline Cobalt Catalysis

We report a cobalt-catalyzed desymmetrizing isomerization of exo-cyclic alkenes to generate chiral 1-methylcyclohexene derivatives with good yields and enantioselectivities. A novel chiral thiazolinyl iminoquinoline ligand and its cobalt complex were designed and synthesized to control the establishment of tertiary or quaternary carbon centers at a remote position. This protocol is operationally simple, and a model for the stereochemical outcome has been proposed.

Catalytic Enantioselective Desymmetrizing Fischer Indolization through Dynamic Kinetic Resolution

The first catalytic enantioselective Fischer indolization of prochiral diketones containing enantiotopic carbonyl groups is developed and shown to proceed through dynamic kinetic resolution (DKR). Catalyzed by the combination of a spirocyclic chiral phosphoric acid and ZnCl₂ (Lewis acid assisted Brønsted acid), this direct approach combines 2,2-disubstituted cyclopentane-1,3-diones with N-protected phenylhydrazines to furnish cyclopenta[b]indole derivatives containing an all-carbon quaternary stereocenter with good to excellent enantioselectivities.

Asymmetric Synthesis of α,β-Epoxy-γ-lactams through Tandem Darzens/Hemiaminalization Reaction

A catalytic asymmetric tandem Darzens/hemiaminalization reaction of glyoxals with α-bromo-β-esteramides or α-bromo-β-ketoamide was accomplished in the presence of a chiral N,N'-dioxide/Yb(III) complex. Various chiral α,β-epoxy-γ-lactams were obtained in moderate to good yields with excellent diastereo- and enantioselectivities. The versatility of the transformation is illustrated in the formal synthesis of berkeleyamide D.

A nickel(ii)-catalyzed asymmetric intramolecular Alder-ene reaction of 1,7-dienes

A highly diastereo- and enantioselective intramolecular Alder-ene reaction with an alkene as the enophile has been developed by using a chiral N,N'-dioxide/nickel(ii) complex as the catalyst. This protocol provides a facile route towards the synthesis of diverse 3,4-disubstituted chroman, tetrahydroquinoline, piperidine and thiochroman derivatives in high yields with good to excellent diastereo- and enantioselectivities.

Dynamic kinetic asymmetric transformations of β-halo-α-keto esters byN,N′-dioxide/Ni(ii)-catalyzed carbonyl-ene reaction

An effective dynamic kinetic asymmetric transformation of racemic β-halo-α-keto esters through carbonyl-ene reaction was realised.