Stereoselective Barbier-Type Allylations and Propargylations Mediated by CpTiCl<sub>3</sub>
作者:Josefa L. López-Martínez、Irene Torres-García、Ignacio Rodríguez-García、Manuel Muñoz-Dorado、Miriam Álvarez-Corral
DOI:10.1021/acs.joc.8b02643
日期:2019.1.18
CpTiCl2, prepared in situ by manganese reduction of CpTiCl3, is an excellent new system for the Barbier-typeallylation and propargylation of carbonyl compounds. It can be used in catalytic amounts when combined with Et3N·HBr/TMSBr, which acts as a regenerating system. The high regio- and stereoselectivity shown by this system makes it useful for prenylation and crotylation processes in the synthesis
Cyclization by Catalytic Ruthenium Carbene Insertion into C sp 3H Bonds
作者:Fermín Cambeiro、Susana López、Jesús A. Varela、Carlos Saá
DOI:10.1002/anie.201107344
日期:2012.1.16
A novel tandem Ru‐catalyzed carbene addition to terminal alkynes/insertion into CHbonds in alkynyl acetals, ethers, and amines has been accomplished under mild reaction conditions (see scheme; TMS=trimethylsilyl). This cascade provides an efficient approach to form complex spiro and fused bicyclic structures by 1,5‐ and 1,6‐hydride shift/cyclization sequences from vinylcarbene Ru intermediates.
Oxygenated Cyclopentenones via the Pauson–Khand Reaction of Silyl Enol Ether Substrates
作者:Paul Shaw、Storm J. Hassell-Hart、Gayle E. Douglas、Andrew G. Malcolm、Alan R. Kennedy、Gemma V. White、Laura C. Paterson、William J. Kerr
DOI:10.1021/acs.orglett.2c00856
日期:2022.4.15
We report here the application of silylenolether moieties as efficient alkene coupling partners within cobalt-mediated intramolecular Pauson–Khand reactions. This cyclization strategy delivers synthetically valuable oxygenated cyclopentenone products in yields of ≤93% from both ketone- and aldehyde-derived silylenolethers, incorporates both terminal and internal alkyne partners, and delivers a
Asymmetric Total Synthesis of Twin Bufogargarizins A and B
作者:Li-Ping Zhong、Rui Feng、Jing-Jing Wang、Chuang-Chuang Li
DOI:10.1021/jacs.2c13494
日期:2023.2.1
The first and asymmetric total synthesis of bufogargarizins A and B, two unusual and highly oxygenated twin steroids with rearranged A/B rings, was achieved. The synthetically challenging [7–5–6–5] tetracyclic ring system of bufogargarizin A was efficiently constructed by the first intramolecular Ru-catalyzed [5 + 2] cycloaddition reaction of a vinyl ether cyclopropane-yne. Notably, the interesting
bufogargarizins A 和 B 是两种不寻常且高度氧化的双类固醇,具有重排的 A/B 环,首次实现了不对称全合成。通过乙烯基醚环丙烷炔的第一个分子内 Ru 催化的 [5 + 2] 环加成反应,有效地构建了具有合成挑战性的 bufogargarizin A [7-5-6-5] 四环系统。值得注意的是,有趣的 [5-7-6-5] 蟾蜍加利津 B 四环骨架通过来自 [7-5-6-5] 四环框架的独特逆醛醇/跨环醛醇级联反应非对映选择性地重新组装。
Brønsted Acid-Promoted Intramolecular Carbocyclization of Alkynals Leading to Cyclic Enones
作者:Carlos González-Rodríguez、Luz Escalante、Jesús A. Varela、Luis Castedo、Carlos Saá
DOI:10.1021/ol900142r
日期:2009.4.2
TFA-promoted exo carbocyclizations of nonterminal 7-alkynals gave good to excellent yields of seven-membered cycloalkenones, a medium-sized functionalized ring present in natural products with relevant pharmacological properties. Nonterminal 5- and 6-alkynals also gave very good yields of the corresponding exo cyclopentenones and cyclohexenones. On the other hand, terminal 5-alkynals gave endo carbocyclizations to cyclohexenones. These carbocyclizations can be considered as tandem alkyne hydration/aldol condensation processes.