The Iridium-catalyzed enantioselective couplingreaction of vinyl azides and allylic electrophiles is presented and provides access to β-chiral carbonyl derivatives. Vinyl azide are used as acetamide enolate or acetonitrile carbanion surrogates, leading to γ,δ-unsaturated β-substituted amides as well as nitriles with excellent enantiomeric excess. The products are readily transformed into chiral N-containing
Generation and Application of (Diborylmethyl)zinc(II) Species: Access to Enantioenriched <i>gem</i>
-Diborylalkanes by an Asymmetric Allylic Substitution
作者:Yeosan Lee、Jinyoung Park、Seung Hwan Cho
DOI:10.1002/anie.201805476
日期:2018.9.24
We report the successful generation of (diborylmethyl)zinc(II) species by transmetallation beteween isolable (diborylmethyl)lithium and zinc(II) halide (X=Br, Cl) and their application in the synthesis of enantioenriched gem‐diborylalkanes bearing a stereogenic center at the β‐position of the diboryl groups by an asymmetric allylic substitution reaction. The reaction has a broad substrate scope, and
A Modular Approach to Aryl-<i>C</i>-ribonucleosides via the Allylic Substitution and Ring-Closing Metathesis Sequence. A Stereocontrolled Synthesis of All Four α-/β- and <scp>d</scp>-/<scp>l</scp>-<i>C</i>-Nucleoside Stereoisomers
作者:Jan Štambaský、Vojtěch Kapras、Martin Štefko、Ondřej Kysilka、Michal Hocek、Andrei V. Malkov、Pavel Kočovský
DOI:10.1021/jo201110z
日期:2011.10.7
generated from (S)-5a, with the enantiopure allylic carbonates (R)-9a,b has been developed as the key step in a new approach to C-nucleoside analogues. The anomeric center was thus constructed via a stereocontrolled formation of the C–O rather than C–C bond with retention of configuration. The resulting bisallyl ethers 15a,b (≥90% de and >99% ee) were converted into C-ribosides 29a,b via the Ru-catalyzed
(S)-5a生成的对映纯单保护的铜(I)对映体的铱(I)催化与对映纯烯丙基碳酸酯(R)-9a,b的烯丙基化反应已成为开发C的新方法的关键步骤-核苷类似物。因此,异头物中心是通过立体控制形成的C–O而非C–C键并保留构型而构建的。将所得的双烯丙基醚15a,b(de≥90%,ee≥99 %)转化为C-核苷29a,b通过Ru催化的闭环复分解,然后由OsO 4或RuO 4催化的非对映选择性二羟基化和脱保护。起始片段5a和9a,b的绝对构型的变化允许所有四个α/β- d / l-组合的立体控制合成。
Herein we present a novel strategy based on palladium-catalyzed allylic alkylation by taking advantage of the nucleophilic addition of external fluoride onto gem-difluoroalkenes as the initiation step. The merit of this protocol is highly appealing, as it enables a formal allylation of trifluoroethylarene derivatives through the in situ generation of β-trifluorocarbanions, which otherwise are deemed to