A Functional-Group-Tolerant Catalytictrans Hydrogenation of Alkynes
摘要:
Against the rules: during the hundred years following Sabatier's groundbreaking work on catalytic hydrogenation, syn delivery of the H atoms to the π system of a substrate remained the governing stereochemical rule. An exception has now be found with the use of cationic [Cp*Ru] templates, which accounts for the first practical, functional-group-tolerant, broadly applicable and highly E-selective semihydrogenation method for alkynes.
<sup>183</sup>
W NMR Spectroscopy Guides the Search for Tungsten Alkylidyne Catalysts for Alkyne Metathesis
作者:Julius Hillenbrand、Markus Leutzsch、Christopher P. Gordon、Christophe Copéret、Alois Fürstner
DOI:10.1002/anie.202009975
日期:2020.11.23
Triarylsilanolates are privileged ancillary ligands for molybdenum alkylidyne catalysts for alkynemetathesis but lead to disappointing results and poor stability in the tungsten series. 1H,183W heteronuclear multiple bond correlation spectroscopy, exploiting a favorable 5J‐coupling between the 183W center and the peripheral protons on the alkylidyne cap, revealed that these ligands upregulate the Lewis acidity
三芳基硅烷醇盐是用于炔复分解的钼亚烷基催化剂的优先辅助配体,但在钨系列中导致令人失望的结果和较差的稳定性。1 H, 183 W 异核多重键相关光谱,利用183 W 中心与烷叉帽上的外围质子之间有利的5 J耦合,揭示了这些配体将路易斯酸度上调到一定程度,使得环丁二烯钨在最初形成[2+2]环加成步骤过度稳定并且催化周转停止。以183 W NMR 位移作为中心原子路易斯酸度的代表,并通过烷叉单元的化学位移张量分析,重新审视了配体设计,并制备了更强的 π 供体全醇盐配体。新的膨胀螯合物具有缓和的路易斯酸度,并且在速率和官能团相容性方面优于带有单齿叔丁氧基配体的经典Schrock催化剂。
Alkyne Metathesis: Development of a Novel Molybdenum-Based Catalyst System and Its Application to the Total Synthesis of Epothilone A and C
作者:Alois Fürstner、Christian Mathes、Christian W. Lehmann
as 15, 16 and 20 which themselves were shown to be catalytically active. Numerous applications illustrate the performance of the catalytic system 1/CH2Cl2 which operates under mild conditions and tolerates an array of polar functional groups. The wide scope allows the method to be implemented into the totalsynthesis of sensitive and polyfunctional natural products. Most notable among them is a concise
adaptation of the established synthesis routes leading to Schrock alkylidynes or can be generated in situ from the molybdenum nitride complex 11, which itself is readily accessible in large quantity from inexpensive sodium molybdate. Complexation of the active silanolate complexes 12 and 24 with 1,10-phenanthroline affords complexes 15 and 25, respectively, which are stable in air for extended periods
A new type of molybdenum alkylidyne catalysts for alkynemetathesis is described, which is distinguished by an unconventional podand topology. These structurally well-definedcomplexes are easy to make on scale and proved to be tolerant toward numerous functional groups; even certain protic substituents were found to be compatible. The new catalysts were characterized by X-ray crystallography and by
描述了一种用于炔复分解的新型钼亚烷基催化剂,其特点是非常规的荚状拓扑结构。这些结构明确的复合物很容易大规模制造,并且被证明对多种官能团具有耐受性;甚至发现某些质子取代基是相容的。新催化剂通过 X 射线晶体学和光谱手段(包括 95 Mo NMR)进行了表征。
A Functional-Group-Tolerant Catalytic<i>trans</i> Hydrogenation of Alkynes
Against the rules: during the hundred years following Sabatier's groundbreaking work on catalytic hydrogenation, syn delivery of the H atoms to the π system of a substrate remained the governing stereochemical rule. An exception has now be found with the use of cationic [Cp*Ru] templates, which accounts for the first practical, functional-group-tolerant, broadly applicable and highly E-selective semihydrogenation method for alkynes.