Synthesis of Polyfunctional Diorganomagnesium and Diorganozinc Reagents through In Situ Trapping Halogen–Lithium Exchange of Highly Functionalized (Hetero)aryl Halides in Continuous Flow
作者:Marthe Ketels、Maximilian A. Ganiek、Niels Weidmann、Paul Knochel
DOI:10.1002/anie.201706609
日期:2017.10.2
Go with the flow: A halogen–lithium exchange using BuLi or PhLi was performed in the presence of various metal salts (ZnCl2, MgCl2⋅LiCl) on a broad range of sensitive bromo- or iodo(hetero)arenes using a commercially available continuous-flow setup. The resulting diarylmagnesium or diarylzinc species were trapped with various electrophiles to give polyfunctional (hetero)arenes in high yields and with
Asymmetric Cα-Alkylation of Proline via Chirality Transfers of Conformationally Restricted Proline Derivative: Application to the Total Synthesis of (−)-Amathaspiramide F
作者:Hyunkyung Cho、Jae Eui Shin、Seokwoo Lee、Hongjun Jeon、Soojun Park、Sanghee Kim
DOI:10.1021/acs.orglett.8b02568
日期:2018.10.5
An efficient strategy for the asymmetricsynthesis of Cα-tetrasubstituted proline derivatives from proline has been established. A nitrogen-fused bicyclic system was devised to control the stereodynamics of proline. Through N-quaternizations with allylic electrophiles followed by [2,3]-rearrangements, the bicyclic proline system delivered enantioenriched Cα-tetrasubstituted prolines. This strategy
Allylic and Allenic Halide Synthesis via NbCl<sub>5</sub>- and NbBr<sub>5</sub>-Mediated Alkoxide Rearrangements
作者:P. C. Ravikumar、Lihua Yao、Fraser F. Fleming
DOI:10.1021/jo901287f
日期:2009.10.2
Addition of NbCl5 or NbBr5 to a series of magnesium, lithium, or potassium allylic or propargylic alkoxides directly provides allylic or allenic halides. Halogenation formally occurs through a metalla-halo-[3,3] rearrangement, although concerted, ionic, and direct displacement mechanisms appear to operate competitively. Transposition of the olefin is equally effective for allylic alkoxides prepared
将NbCl 5或 NbBr 5 添加到一系列镁、锂或钾的烯丙基或炔丙基醇盐中直接提供烯丙基或烯丙基卤化物。卤化通过金属-卤-[3,3] 重排正式发生,尽管协同、离子和直接置换机制似乎具有竞争性。烯烃的转位对于通过亲核加成、去质子化或还原制备的烯丙基醇盐同样有效。实验上,五卤化铌卤化反应迅速,萃取后可提供基本纯的 ( E )-烯丙基或烯丙基卤化物,适用于一系列脂肪族和芳香族醇、醛和酮。
Entry to β-Alkoxyacrylates via Gold-Catalyzed Intermolecular Coupling of Alkynoates and Allylic Ethers
作者:Sae Rom Park、Cheoljae Kim、Dong-gil Kim、Neetipalli Thrimurtulu、Hyun-Suk Yeom、Jungho Jun、Seunghoon Shin、Young Ho Rhee
DOI:10.1021/ol4001087
日期:2013.3.15
The first gold-catalyzed intermolecular coupling of alkynoates and allylicethers invoking alkoxy addition and [3,3]-sigmatropic rearrangement as the key mechanism has been developed. Remarkably, the reaction showed complete chemoselectivity toward the pathway initiated by the alkoxy addition to alkynes. This unprecedented reactivity led to a new access to diversely substituted β-alkoxyacrylates in
作者:Mario Ellwart、Ilya S. Makarov、Florian Achrainer、Hendrik Zipse、Paul Knochel
DOI:10.1002/anie.201603923
日期:2016.8.22
Readily prepared allylic zinc halides undergo SN2‐type substitutions with allylic bromides in a 1:1 mixture of THF and DMPU providing 1,5‐dienes regioselectively. The allylic zinc species reacts at the most branched end (γ‐position) of the allylic system furnishing exclusively γ,α′‐allyl–allyl cross‐coupling products. Remarkably, the double bond stereochemistry of the allylic halide is maintained during
现成的烯丙基卤化锌在THF和DMPU的1:1混合物中用烯丙基溴进行S N 2型取代,可选择性地提供1,5二烯。烯丙基锌物种在烯丙基体系的最分支末端(γ位置)反应,专门提供γ,α'-烯丙基-烯丙基交叉偶联产物。值得注意的是,烯丙基卤的双键立体化学在交叉偶联过程中得以保持。还可以耐受几个官能团(酯,腈)。烯丙基锌试剂的这种交叉偶联可以扩展到炔丙基和苄基卤化物。DFT计算显示了氯化锂在该替代中的重要性。