Highly Enantioselective Cobalt‐Catalyzed (3+2) Cycloadditions of Alkynylidenecyclopropanes
作者:Eduardo Da Concepción、Israel Fernández、José L. Mascareñas、Fernando López
DOI:10.1002/anie.202015202
日期:2021.4.6
Low‐valent cobalt complexes equipped with chiral ligands can efficiently promote highly enantioselective (3+2) cycloadditions of alkyne‐tethered alkylidenecyclopropanes. The annulation allows to assemble bicyclic systems containing five‐membered rings in good yields and with excellent enantiomeric ratios. We also present a mechanistic discussion based on experimental and computational data, which support
配备手性配体的低价钴络合物可以有效地促进炔烃系链的亚烷基环丙烷的高对映选择性(3 + 2)环加成反应。该环状结构可以以高收率和出色的对映体比率组装包含五元环的双环系统。我们还提出了基于实验和计算数据的机制讨论,这些讨论支持Co I / Co III催化循环的参与。
When cobalt-mediated [2 + 2 + 2] cycloaddition reaction dares go astray: synthesis of unprecedented cobalt(<scp>iii</scp>)-complexes
In sharp contrast with the standard [2 + 2 + 2] cycloadditionreaction of diyne/ene, cobalt-mediated cycloadditions with γ-alkylidenebutenolide led to unprecedented cobalt(III) polycyclic complexes. A plausible mechanism supported by a computational study based on an unusual fragmentation of the butenolide moiety was postulated to account for this original reaction.
Herein, we describe unprecedented access to all-carbon or heterocyclic seven-membered ring frameworks from 1,8-ene-ynes promoted by inexpensive low-valent titanium(II) species, readily available from Ti(OiPr)4 and Grignard reagent. A broad range of cycloheptane, azepane or oxepane derivatives has been obtained (19 examples) with moderate to good yields and an excellent selectivity (up to 95/5 d.r.)
A Rhodium(I)-Catalyzed Formal Allenic Alder Ene Reaction for the Rapid and Stereoselective Assembly of Cross-Conjugated Trienes
作者:Kay M. Brummond、Hongfeng Chen、Peter Sill、Lingfeng You
DOI:10.1021/ja027588p
日期:2002.12.1
A rhodium(I)-catalyzed allenic Alderenereaction to prepare cross-conjugated trienes has been discovered. The scope and limitations are currently being investigated, and the results obtained to date are reported on. This method shows enticing functional group compatibility by tolerating terminal and internal alkynes, hydroxyl, sulfonamide, ether, and diester groups. Progress has been made to increase
Synthesis of Substituted Piperidines via Cationic Palladium(II)-Catalyzed Reductive Coupling of N-Tosyl-Tethered Alkynones
作者:Xiaojuan Zhang、Xiuling Han、Zhiyong Hu、Xiyan Lu
DOI:10.1055/s-0036-1588803
日期:2017.10
the Special Topic Modern Strategies for Heterocycles Synthesis Abstract A cationic palladium(II) complex catalyzed reductivecoupling of N-tosyl-tethered alkynones for the synthesis of functionalized piperidines was successfully developed. This reaction was initiated by hydropalladation of the alkyne and quenched by addition to the intramolecular carbonyl group. The substituent on the alkyne is key