Scope and Mechanistic Investigations on the Solvent-Controlled Regio- and Stereoselective Formation of Enol Esters from the Ruthenium-Catalyzed Coupling Reaction of Terminal Alkynes and Carboxylic Acids.
Scope and Mechanistic Investigations on the Solvent-Controlled Regio- and Stereoselective Formation of Enol Esters from the Ruthenium-Catalyzed Coupling Reaction of Terminal Alkynes and Carboxylic Acids.
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钌催化末端炔烃和羧酸偶联反应中溶剂控制的区域选择性和立体选择性烯醇酯形成的范围和机理研究。
DOI：
10.1021/om9007357
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发表时间：
2009
期刊：
影响因子：
2.8
通讯作者：
Gao,Ruili
中科院分区：
文献类型：
--
作者：
Yi,ChaeS;Gao,Ruili
研究发现，（PCy_3）_2（CO）RuHCl是一种高效的催化剂，可用于炔-羧酸偶联反应，生成合成有用的烯醇酯产物。钌催化剂对反应的活性和选择性有很强的溶剂效应，在CH 2Cl 2中的偶联反应导致了gem-enol酯产物的区域选择性生成，而在THF中的偶联反应导致了（Z）-烯醇酯的立体选择性生成.偶联反应被发现是强烈抑制PCy 3。PhCO 2 H/PhC β-CD和PhCO 2D/PhC β-CH的偶联反应导致在烯醇酯产物的乙烯基位置上广泛的氘掺入。在CDCl 3（ρ = +0.30）和THF（ρ =-0.68）中，考察一系列对位取代的dp-X-C6 H4 CO2 H（X = OMe，CH 3，H，CF 3，CN）与苯乙炔的相关性时，观察到相反的Hammett值。分离出了催化相关的Ru-羧酸盐和-亚乙烯基-羧酸盐配合物（PCy 3）2（CO）（Cl）Ru（κ2-O2 CC 6 H4-p-OMe）和（PCy 3）2（CO）（Cl）RuC（CH 2CHPh）O2 CC 6 H4-p-OMe，并通过X射线晶体学完全确定了这两种配合物的结构。在这些动力学和结构研究的基础上，提出了涉及限速C−O键形成步骤的偶联反应的详细机制。在CH 2Cl 2中的区域选择性形成的偕烯醇酯产物的合理化的直接迁移插入末端炔通过Ru-羧酸物种，而在THF中的立体选择性形成的（Z）-烯醇酯产物的解释调用Ru-亚乙烯基物种。
The ruthenium-hydride complex (PCy3)2(CO)RuHCl was found to be a highly effective catalyst for the alkyne-to-carboxylic acid coupling reaction to give synthetically useful enol ester products. A strong solvent effect was observed for the ruthenium catalyst in modulating the activity and selectivity; the coupling reaction in CH2Cl2led to the regioselective formation ofgem-enol ester products, while the stereoselective formation of (Z)-enol esters was obtained in THF. The coupling reaction was found to be strongly inhibited by PCy3. The coupling reaction of both PhCO2H/PhCCD and PhCO2D/PhCCH led to extensive deuterium incorporation on the vinyl positions of the enol ester products. An opposite Hammett value was observed when the correlation of a series ofpara-substitutedp-X-C6H4CO2H (X = OMe, CH3, H, CF3, CN) with phenylacetylene was examined in CDCl3(ρ = +0.30) and THF (ρ = −0.68). Catalytically relevant Ru-carboxylate and -vinylidene-carboxylate complexes, (PCy3)2(CO)(Cl)Ru(κ2-O2CC6H4-p-OMe) and (PCy3)2(CO)(Cl)RuC(CHPh)O2CC6H4-p-OMe, were isolated, and the structure of both complexes was completely established by X-ray crystallography. A detailed mechanism of the coupling reaction involving a rate-limiting C−O bond formation step was proposed on the basis of these kinetic and structural studies. The regioselective formation of thegem-enol ester products in CH2Cl2was rationalized by a direct migratory insertion of the terminal alkyne via a Ru-carboxylate species, whereas the stereoselective formation of (Z)-enol ester products in THF was explained by invoking a Ru-vinylidene species.