Amine- and Ether-Chelated Aryllithium Reagents-Structure and Dynamics

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• 作者：Hans J. Reich ; Wayne S. Goldenberg ; Aaron W. Sanders ; Kevin L. Jantzi ; and C. Christoph Tzschucke
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：March 26, 2003
• 年：2003
• 卷：125
• 期：12
• 页码：3509 - 3521
• 全文大小：405K
• 年卷期：v.125,no.12(March 26, 2003)
• ISSN：1520-5126

文摘

Chelation and aggregation in phenyllithium reagents with potential 6- and 7-ring chelating amine(2, 3) and 5-, 6-, and 7-ring chelating ether (4, 5, 6) ortho substituents have been examined utilizing variabletemperature ⁶Li and ¹³C NMR spectroscopy, ⁶Li and ¹⁵N isotope labeling, and the effects of solvent additives.The 5- and 6-ring ether chelates (4, 5) compete well with THF, but the 6-ring amine chelate (2) barelydoes, and 7-ring amine chelate (3) does not. Compared to model compounds (e.g., 2-ethylphenyllithium7), which are largely monomeric in THF, the chelated compounds all show enhanced dimerization (asmeasured by K = [D]/[M]²) by factors ranging from 40 (for 6) to more than 200 000 (for 4 and 5). Chelationisomers are seen for the dimers of 5 and 6, but a chelate structure could be assigned only for2-(2-dimethylaminoethyl)phenyllithium (2), which has an A-type structure (both amino groups chelated tothe same lithium in the dimer) based on NMR coupling in the ¹⁵N, ⁶Li labeled compound. Unlike the dimer,the monomer of 2 is not detectably chelated. With the exception of 2-(methoxymethyl)phenyllithium (4),which forms an open dimer (12) and a pentacoordinate monomer (13), the lithium reagents all formmonomeric nonchelated adducts with PMDTA.