Catalytic, Highly Enantio- and Diastereoselective Pinacol Coupling Reaction with a New Tethered Bis(8-quinolinolato) Ligand

A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is developed. Its chromium complex, TBOxCrCl (3 mol %), effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diastereoselectivity (up to dl:meso = 98:2), and high enantioselectivity (up to 98%). The scope of the present method turns out not to be limited to aromatic aldehyde derivatives, as cyclohexanecarboxaldehyde undergoes pinacolization as well (44% yield, dl:meso = 93:7, 84% ee). The method provides an efficient access to enantioenriched 1,2-diols

Helical Chiral 2,2′-Bipyridine <i>N-</i> Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane

A highly enantioselective synthesis of homopropargylic alcohols is achieved by using the new helical chiral 2,2′-bipyridine N-monoxide catalyst and allenyltrichlorosilane. This method can be further extended to the enantio- and regioselective propargylation of N-acylhydrazones

Asymmetric Crotylation Reactions in Synthesis of Polypropionate-Derived Macrolides: Application to Total Synthesis of Oleandolide

Complete details of a convergent asymmetric synthesis of oleandolide (1), the aglycon of the macrolide antibiotic oleandomycin, is described. The synthesis has been achieved through the assembly and coupling of the left- and right-hand subunits 12 and 38, respectively. These subunits were prepared from chiral silane-based asymmetric crotylation reactions to control the stereochemical relationships. The left- and right-hand subunits (C1−C7 and C8−C14) were brought together through a Pd(0)-catalyzed sp3−sp2 cross-coupling reaction between the zinc intermediate 40 and vinyl triflate 38 to give 27. This product was converted to seco acid 42a and cyclized to lactone 35 under Yamaguchi conditions. This material was then epoxidized with m-chloroperbenzoic acid (m-CPBA) to install the correct C8 epoxide as a single diastereomer, which after a short deprotection sequence completed the synthesis of oleandolide

Total Synthesis of Oleandolide

Total Synthesis of Oleandolid

Asymmetric Conjugate Addition of Silyl Enol Ethers Catalyzed by Tethered Bis(8-quinolinolato) Aluminum Complexes

New chiral tethered bis(8-quinolinolato) (TBOx) aluminum(III) complexes effectively catalyze the highly enantioselective Mukaiyama−Michael reaction of silyl enol ethers, including tetrasubstituted enolates that give rise to enantioenriched α-carbonyl all-carbon-substituted quaternary stereocenters. The present catalyst also promotes the conjugate addition of N-benzylindole to α,β-unsaturated acylphosphonates with high enantioselectivity (indole Friedel−Crafts alkylation reaction)

Asymmetric Conjugate Addition of Silyl Enol Ethers Catalyzed by Tethered Bis(8-quinolinolato) Aluminum Complexes

New chiral tethered bis(8-quinolinolato) (TBOx) aluminum(III) complexes effectively catalyze the highly enantioselective Mukaiyama−Michael reaction of silyl enol ethers, including tetrasubstituted enolates that give rise to enantioenriched α-carbonyl all-carbon-substituted quaternary stereocenters. The present catalyst also promotes the conjugate addition of N-benzylindole to α,β-unsaturated acylphosphonates with high enantioselectivity (indole Friedel−Crafts alkylation reaction)

Helical Chiral 2,2′-Bipyridine <i>N-</i> Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane

A highly enantioselective synthesis of homopropargylic alcohols is achieved by using the new helical chiral 2,2′-bipyridine N-monoxide catalyst and allenyltrichlorosilane. This method can be further extended to the enantio- and regioselective propargylation of N-acylhydrazones

Catalytic, Highly Enantio- and Diastereoselective Pinacol Coupling Reaction with a New Tethered Bis(8-quinolinolato) Ligand

A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is developed. Its chromium complex, TBOxCrCl (3 mol %), effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diastereoselectivity (up to dl:meso = 98:2), and high enantioselectivity (up to 98%). The scope of the present method turns out not to be limited to aromatic aldehyde derivatives, as cyclohexanecarboxaldehyde undergoes pinacolization as well (44% yield, dl:meso = 93:7, 84% ee). The method provides an efficient access to enantioenriched 1,2-diols

Catalytic, Highly Enantio- and Diastereoselective Pinacol Coupling Reaction with a New Tethered Bis(8-quinolinolato) Ligand

A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is developed. Its chromium complex, TBOxCrCl (3 mol %), effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diastereoselectivity (up to dl:meso = 98:2), and high enantioselectivity (up to 98%). The scope of the present method turns out not to be limited to aromatic aldehyde derivatives, as cyclohexanecarboxaldehyde undergoes pinacolization as well (44% yield, dl:meso = 93:7, 84% ee). The method provides an efficient access to enantioenriched 1,2-diols

Asymmetric Conjugate Addition of Silyl Enol Ethers Catalyzed by Tethered Bis(8-quinolinolato) Aluminum Complexes

New chiral tethered bis(8-quinolinolato) (TBOx) aluminum(III) complexes effectively catalyze the highly enantioselective Mukaiyama−Michael reaction of silyl enol ethers, including tetrasubstituted enolates that give rise to enantioenriched α-carbonyl all-carbon-substituted quaternary stereocenters. The present catalyst also promotes the conjugate addition of N-benzylindole to α,β-unsaturated acylphosphonates with high enantioselectivity (indole Friedel−Crafts alkylation reaction)