A Versatile Enantioselective Catalytic Cyclopropanation‐Rearrangement Approach to the Divergent Construction of Chiral Spiroaminals and Fused Bicyclic Acetals
A highly enantioselective synthesis of various chiral heterobicyclic molecules including spiroaminals and fused bicyclic acetals has been developed via a chiral copper catalyzed cyclopropanation‐rearrangement (CP‐RA) approach under mild reaction conditions. Remarkably, the asymmetric CP‐RA for exocyclic vinyl substrates without a pro‐stereogenic carbon at the β‐position has been realized for the first
Sequential Cyclosulfonylation and Alkylation as a Versatile Strategy for Dihydropyran Synthesis
作者:Gavin L. Edwards、David J. Sinclair
DOI:10.1055/s-2005-918498
日期:——
Deprotonation of 3,4-dihydro-6-(p-toluenesulfonylmethyl)-2H-pyran (2) with n-BuLi and alkylation of the lithiated allyl sulfone gives good to excellent yields of monoalkylated products 3. No γ-substitution is observed in the monoalkylated products. A second deprotonation allows for the introduction of a second alkyl group. Desulfonylation can be effected with either sodium amalgam or sodium/ethanol in THF.
Chiral Phosphoric Acid Catalyzed Addition of Dihydropyrans to <i>N</i>-Acyl Imines: Stereocontrolled Access to Enantioenriched Spirocyclic Oxazoletetrahydropyrans with Three Contiguous Stereocenters
作者:Guilong Li、Matthew J. Kaplan、Lukasz Wojtas、Jon C. Antilla
DOI:10.1021/ol100378t
日期:2010.5.7
Dihydropyran derivatives readily undergo addition to N-acyl imines in the presence of chiral phosphoric acids. This addition process yields an attractive product that is capable of a tandem oxidative-cyclization via an epoxide intermediate.
A stereoselective synthesis of trisubstituted alkenes. Part 2. The nickel-catalysed coupling of Grignard reagents with 6-alkyl-3,4-dihydro-2H-pyrans and acyclic enol ethers
作者:Philip A. Ashworth、Nicholas J. Dixon、Philip J. Kocieński、Sjoerd N. Wadman
DOI:10.1039/p19920003431
日期:——
The Ni0-catalysed coupling of Grignard reagents devoid of beta-hydrogens with 6-alkyl-3,4-dihydro-2H-pyrans and acyclic enol ethers is highly stereoselective and gives trisubstituted alkenes with retention of configuration. The reaction was applied to syntheses of the aggregation pheromone of the square-necked grain beetle, a fragment of Premonensin B, and the polyketide fragment of Jaspamide.