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首页> 外文期刊>Chemistry: A European journal >Mechanism and origins of regio- and enantioselectivities in Rh ~I-catalyzed hydrogenative couplings of 1,3-diynes and activated carbonyl partners: Intervention of a cumulene intermediate
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Mechanism and origins of regio- and enantioselectivities in Rh ~I-catalyzed hydrogenative couplings of 1,3-diynes and activated carbonyl partners: Intervention of a cumulene intermediate

机译：Rh〜I催化的1,3-二炔与活化羰基伙伴的加氢偶合中区域和对映选择性的机理和起源：对异丙苯中间体的干预

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摘要

The mechanism of the rhodium-catalyzed reductive coupling of 1,3-diynes and vicinal dicarbonyl compounds employing H_2 as reductant was investigated by density functional theory. Oxidative coupling through 1,4-addition of the Rh~I-bound dicarbonyl to the conjugated diyne via a seven-membered cyclic cumulene transition state leads to exclusive formation of linear adducts. Diyne 1,4-addition is much faster than the 1,2-addition to simple alkynes. The 1,2-dicarbonyl compound is bound to rhodium in a bidentate fashion during the oxidative coupling event. The chemo-, regio-, and enantioselectivities of this reaction were investigated and are attributed to this unique 1,4-addition pathway. The close proximity of the ligand and the alkyne substituent distal to the forming C-C bond controls the regio- and enantioselectivity: coupling occurs at the sterically more demanding alkyne terminus, which minimizes nonbonded interaction with the ligand. A stereochemical model is proposed that accounts for preferential formation of the (R)-configurated coupling product when (R)-biaryl phosphine ligands are used.
机译：通过密度泛函理论研究了铑以H_2为还原剂催化的1，3-二炔与邻二羰基化合物的铑催化的还原偶联机理。通过Rh_I-键合的二羰基经由七元环状枯烯过渡态的1，4-加成至共轭二炔的氧化偶联导致线性加合物的排他形成。 Diyne 1,4-加成比简单炔烃的1,2-加成快得多。 1，2-二羰基化合物在氧化偶联过程中以二齿形式与铑结合。研究了该反应的化学，区域和对映选择性，并将其归因于这种独特的1，4-加成途径。配体和远离形成C-C键的炔烃取代基非常接近，控制区域和对映选择性：偶合发生在对空间要求更高的炔烃末端，从而使与配体的非键相互作用最小化。提出了立体化学模型，其解释了当使用（R）-联芳基膦配体时优先形成（R）-构型的偶联产物。

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