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首页> 外文期刊>Chemistry: A European journal >Experimental and Theoretical Study of Tunable 1,3-Lithium Shift of Propargylic/Allenylic Species, Transmetallation, and Pd-Catalyzed Cross- Coupling Reactions
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Experimental and Theoretical Study of Tunable 1,3-Lithium Shift of Propargylic/Allenylic Species, Transmetallation, and Pd-Catalyzed Cross- Coupling Reactions

机译：炔丙基/丙烯基可调的1，3-锂位移，金属转移和Pd催化的交叉偶联反应的实验和理论研究

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摘要

The highly selective tuning of the isomerization from 1-arylalka- 1,2-dien-1-yllithium to 1-arylalka-1,2- dien-3-yllithium has been realized in the deprotonation of 1-arylalk-1-yne (conditions A and B) and carbolithiation of 1-arylbut-3-en-1-yne with alkyllithium (conditions C and D). Subsequent transmetallation and Pd-catalyzed Negishi coupling reactions afforded 1,1-diaryl or 1,3-diaryl allenes with high selectivity. Deuterium-labeling cross experiments indicated that an intermolecular lithiation process occurred in both 1,3-lithium shift conditions (conditions B and D). 1-Arylalka- 1,2-diene was confirmed experimentally to be the intermediate. A computational study at the B3LYP level for the isomerization indicated that the acidity of H at the 3-position is higher than that of the H at the 1-position of 1- phenyl-1,2-butadiene. Under conditions B, iPr2NH acts as a proton carrier to finish the 1,3-lithium shift. The overall activation barrier for the rate-determining step in the solvated models is 21.0 kcalmol1, indicating that the isomerization is reasonable at room temperature. For the isomerization under conditions D, DFT calculations indicated that the addition of TMEDA (tetramethylethylenediamine) and HMPA (hexamethylphosphoramide) changes the global minimum of the system; among the possible mechanisms (P1–P5) considered, the mechanism catalyzed by dilithiated species (P5) is the most probable one. The overall activation barriers for isomerization in THF and TMEDA solvated models are 22.6 and 19.7 kcalmol1, respectively, proving that the isomerization may proceed at RT in THF or at 78 8C with TMEDA, due to the fact that the solvation of the additives may increase the concentration of 1-phenyl- 1,2-butadienyllithium monomer by a deaggregation effect.
机译：在1-芳基烷基-1-炔的去质子化反应中已经实现了从1-芳基烷基1,2-2-二烯-1-基锂到1-芳基烷基1,2-二烯-3-基锂的异构化的高度选择性调节（条件A和B）和1-芳基丁-3-烯-1-炔与烷基锂的碳环化（条件C和D）。随后的金属转移作用和Pd催化的Negishi偶联反应提供了具有高选择性的1,1-二芳基或1,3-二芳基烯。氘标记的交叉实验表明，分子间的锂化过程发生在两种1,3-锂转移条件下（条件B和D）。实验证实1-芳基-1，2-二烯为中间体。在B3LYP水平进行异构化的计算研究表明，在3位的H的酸度高于在1苯基-1,2-丁二烯的1位的H的酸度。在条件B下，iPr2NH充当质子载体完成1，3-锂的转变。在溶剂化模型中用于速率确定步骤的总活化障碍为21.0 kcalmol1，表明异构化在室温下是合理的。对于条件D下的异构化，DFT计算表明添加TMEDA（四甲基乙二胺）和HMPA（六甲基磷酰胺）会改变系统的整体最小值。在所考虑的可能机制（P1-P5）中，由双金属物种（P5）催化的机制是最可能的机制。在THF和TMEDA溶剂化模型中，异构化的总体活化障碍分别为22.6和19.7 kcalmol1，这证明异构化可能在THF中于RT或在78 8 C下用TMEDA进行，这是由于添加剂的溶剂化可能会增加通过解聚作用使1-苯基-1，2-丁二烯基锂单体的最大浓度。

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