Vinylethers can be protonated to generate oxocarbenium ions that react with Me3SiCN to form cyanohydrin alkylethers. Reactions that form racemic products proceed efficiently upon conversion of the vinylether to an α-chloro ether prior to cyanide addition in a pathway that proceeds through Brønsted acid-mediated chloride ionization. Enantiomerically enriched products can be accessed by directly protonating
乙烯基醚可以质子化以生成氧代碳正离子,该离子与 Me 3 SiCN反应形成氰醇烷基醚。在通过布朗斯台德酸介导的氯离子电离进行的途径中,在加入氰化物之前将乙烯基醚转化为 α-氯醚后,形成外消旋产物的反应有效进行。可以通过用手性布朗斯台德酸直接质子化乙烯基醚以形成手性离子对来获得对映体富集的产品。Me 3 SiCN 作为亲核试剂,PhOH 在不对称双分子亲核加成到氧碳鎓离子的罕见例子中作为化学计量质子源。计算研究为催化剂和氧代碳正离子之间的相互作用提供了模型。
Diastereoselective Diels−Alder Reactions of <i>N</i>-Sulfonyl-1-aza-1,3-butadienes with Optically Active Enol Ethers: An Asymmetric Variant of the 1-Azadiene Diels−Alder Reaction
作者:Ryan C. Clark、Steven S. Pfeiffer、Dale L. Boger
DOI:10.1021/ja0571646
日期:2006.3.1
room-temperature asymmetricDiels-Alder reaction of N-sulfonyl-1-aza-1,3-butadienes is reported enlisting a series of 19 enol ethers bearing chiralauxiliaries, with many providing highly diastereoselective (endo and facial diastereoselection) reactions, largely the result of an exquisitely organized [4+2] cycloaddition transition state. Three new, readily accessible, and previously unexplored auxiliaries rationally
Stereochemistry and Mechanism of Vinyl-migrating [1,2]-Wittig Rearrangement of<i>α</i>-Lithioalkyl Vinyl Ethers
作者:Katsuhiko Tomooka、Tadashi Inoue、Takeshi Nakai
DOI:10.1246/cl.2000.418
日期:2000.4
Enantiomerically defined α-stannylalkyl or α-methylbenzyl vinyl ethers, when treated with butyllithium, are shown to undergo the 1,2-vinyl migration to afford the allylic alcohols in almost racemic form in low or high yield, respectively, thereby proposing the radical cleavage-recombination pathway.
Enantioselective [4 + 2] Cycloadditions of <i>o</i>-Quinone Methides: Total Synthesis of (+)-Mimosifoliol and Formal Synthesis of (+)-Tolterodine
作者:Carolyn Selenski、Thomas R. R. Pettus
DOI:10.1021/jo048703c
日期:2004.12.1
The first example of an enantioselectivecycloaddition of an o-quinone methide (o-QM) with a chiral enol ether is described along with the total synthesis of (+)-mimosifoliol and the formal synthesis of (+)-tolterodine. These syntheses exemplify a three-component, one-pot benzopyran approach for the construction of chiral benzylic junctions. Cycloadditions of various enol ethers and o-QMs are examined
Asymmetric Access to α-Substituted Functional Aspartic Acid Derivatives by a [3+2] Strategy Employing a Chiral Dienophile
作者:Kawther Ben Ayed、Anne Beauchard、Jean-François Poisson、Sandrine Py、Mathieu Y. Laurent、Arnaud Martel、Houcine Ammar、Souhir Abid、Gilles Dujardin
DOI:10.1002/ejoc.201301739
日期:2014.5
NH-isoxazolidine, the absolute configuration of which was established by X-ray crystallography. N-Protection and N–O cleavage of this isoxazolidine gave enantioenriched quaternary aspartate derivatives bearing functionalized side chains.