Studies in biomimetic alkaloid syntheses. 8. Total syntheses of the C-14 epimeric hydroxyvincadifformines, tabersonine, a (hydroxymethyl)-D-norvincadifformine and the C-20 epimeric pandolines
Heterocyclic group transfer reactions with I(<scp>iii</scp>) <i>N</i>-HVI reagents: access to <i>N</i>-alkyl(heteroaryl)onium salts <i>via</i> olefin aminolactonization
作者:Anthony F. Tierno、Jennifer C. Walters、Andres Vazquez-Lopez、Xiao Xiao、Sarah E. Wengryniuk
DOI:10.1039/d1sc00187f
日期:——
Pyridinium and related N-alkyl(heteroaryl)onium salts are versatile synthetic intermediates in organic chemistry, with applications ranging from ring functionalizations to provide diverse piperidine scaffolds to their recent emergence as radical precursors in deaminative cross couplings. Despite their ever-expanding applications, methods for their synthesis have seen little innovation, continuing to
吡啶鎓和相关的N-烷基(杂芳基)鎓盐是有机化学中的多功能合成中间体,其应用范围从环官能化以提供多种哌啶支架到最近作为脱氨基交叉偶联中的自由基前体出现。尽管它们的应用不断扩大,但其合成方法几乎没有创新,仍然依赖于有限的数十年历史的转化和有限的偶联伙伴子集。在此,我们利用(双)阳离子氮连接的 I( III ) 高价碘试剂或N -HVI 作为“杂环基团转移试剂”,通过氨基内酯化提供广泛的N -烷基(杂芳基)鎓盐链烯酸的合成,这是与烯烃直接生成这些盐的第一个例子。该反应在温和的条件下以优异的产率进行,并且能够掺入广泛的空间和电子多样化的芳香杂环。 N -HVI 试剂可以原位生成,通过简单的研磨分离产物,随后的衍生化证明了该平台用于以多样性为导向的六元氮杂环合成的能力。
A Flexible, Convergent Approach to Polycyclic Indole Structures: Formal Synthesis of (±)-Mersicarpine
作者:Aurélien Biechy、Samir Z. Zard
DOI:10.1021/ol900996k
日期:2009.7.2
The formal synthesis of (±)-mersicarpine was achieved using an intermolecularradical addition−radical cyclization cascade. This key reaction represents a flexible, convergent route to numerous polycyclic indole derivatives.
featuring a Claisen-Ireland rearrangement to install the two contiguous stereogenic centers, E1cB elimination to form the tetrasubstituted C–C double bond, and a 2,3-Wittig rearrangement to construct the quaternary carbon. Ring-closing metathesis and an intramolecular carbonyl ene reaction were employed for construction of the requisite ring system.
The free‐radical three‐component carbocyanation of electron‐rich olefins was investigated with p‐tosyl cyanide as cyanide source. The scope and limitations of the process were established by varying the nature of the alkene and radical precursor. Carbocyanation of chiral allylsilanes was shown to occur with high diastereocontrol, leading to syn β‐silyl nitriles. The origin of the stereocontrol was
A stereocontrolledtotalsynthesis of (+)-vinblastine was accomplished, featuring preparations of the two indole units by means of a novel indole synthesis via radical cyclization of thioanilide, and a stereoselective coupling of these units.