readily reacts with Br− ions to afford the anionic, zero‐valent atecomplex [L3PdBr]−. In contrast, more‐electron‐rich Pd catalysts display lower tendencies toward the formation of atecomplexes. Combining [L3Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the PdII atecomplex [L2Pd(Ar)I2]−.
Second Comes First: Switching Elementary Steps in Palladium‐Catalyzed Cross‐Coupling Reactions
作者:Marlene Kolter、Konrad Koszinowski
DOI:10.1002/chem.202001041
日期:2020.9.21
cross‐coupling products RR′. This reaction sequence corresponds to a catalytic cycle, in which the order of the elementary steps of transmetalation and oxidative addition is switched relative to that of palladium‐catalyzed cross‐coupling reactions proceeding via neutral intermediates. An attractive feature of the palladate‐based catalytic system is its ability to mediate challenging alkyl–alkyl coupling
贫电子钯(0)配合物L 3 Pd(L=三[3,5-双(三氟甲基)苯基]膦)与格氏试剂RMgX和有机锂化合物RLi通过金属转移反应生成阴离子有机钯酸盐[L 2 PdR] −,如负离子模式电喷雾电离质谱所示。这些钯酸酯经历有机卤化物 R'X 的氧化加成(或相关的 S N 2 型反应),然后进一步进行金属转移。所得杂配钯(II)配合物的气相裂解导致交叉偶联产物RR'的还原消除。该反应序列对应于催化循环,其中金属转移和氧化加成的基本步骤的顺序相对于通过中性中间体进行的钯催化交叉偶联反应的顺序进行转换。基于钯酸酯的催化系统的一个有吸引力的特点是它能够介导具有挑战性的烷基-烷基偶联反应。然而,膦配体L对分解反应的稳定性较差,迄今为止阻碍了其在实际应用中的成功使用。
Radically polymerizable compositions
申请人:Polynt Composites USA, Inc.
公开号:US11518834B2
公开(公告)日:2022-12-06
Polymerizable compositions comprising a radically polymerizable resin can be polymerized in the absence of a peroxide initiator and other undesirable components. The polymerizable compositions and methods employ a manganese- or iron-containing salt or organic complex and a 1,3-dioxo compound with one or more other components. The polymerizable compositions have better storage stability and reduced gel time-drift.