Benzyltriethylammoniumborohydride-chlorotrimethylsilane reagent system has been found to effect a novel and unusual reaction with cyclic and cyclic enol ethers 1 to give exclusively diols and alcohols 2 respectively in high yields, under very mild reaction conditions.
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
A highly diastereo- and enantioselective [3 + 2] cycloaddition of 2,2′-diester aziridines with 3,4-dihydropyran derivatives and acyclic enolethers has been established. Various optically active octahydropyrano[2,3-c]pyrrole and 3-methoxypyrrolidine derivatives were generated in moderate to high yields (up to 94%) and good stereoselectivities (>19:1 dr, up to 95.5:4.5 er). The methodology was also
已经建立了2,2'-二酯氮丙啶与3,4-二氢吡喃衍生物和非环烯醇醚的高度非对映和对映选择性[3 + 2]环加成反应。以中等至高产率(高达94%)和良好的立体选择性(> 19:1 dr,高达95.5:4.5 er)生成了各种旋光的八氢吡喃并[2,3- c ]吡咯和3-甲氧基吡咯烷衍生物。该方法还用于d-半乳糖衍生物的高度非对映选择性合成中。八氢吡喃并[2,3- c ]吡咯的绝对构型表明,在最后的环化步骤中,使用3,4-二氢吡喃和6-烷基取代的吡咯为底物的反应给出了反向的非对映异构。
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.
Cyclic vinyl ether carbanions I: Synthetic equivalents of β-acylvinyl and substituted acyl anions