Structural and Rate Studies of the Formation of Substituted Benzynes

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• 作者：Jason C. Riggs ; Antonio Ramirez ; Matthew E. Cremeens ; Crystal G. Bashore ; John Candler ; Michael C. Wirtz ; Jotham W. Coe ; David B. Collum
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：March 19, 2008
• 年：2008
• 卷：130
• 期：11
• 页码：3406 - 3412
• 全文大小：143K
• 年卷期：v.130,no.11(March 19, 2008)
• ISSN：1520-5126

文摘

The key elimination step for the formation of 3-substituted and 3,6-disubstituted benzynes from2-haloaryllithiums displays a pronounced solvent-dependent regioselectivity. All 2-haloaryllithiums withelectron withdrawing groups in the 6 position are shown by ⁶Li and ¹³C NMR spectroscopic studies to bemonomers in THF. DFT computational studies implicate trisolvates. Rate studies reveal that LiF eliminatesvia monomer-based pathways requiring THF dissociation whereas LiCl eliminates via nondissociativepathways. Elimination to form 3-chloro- and 3-fluorobenzyne from 2-chloro-6-fluorophenyllithium displaysa pronounced solvent-dependent regioselectivity that is traced to competing solvent-dissociative andnondissociative dissociative pathways for the elimination of LiCl and LiF, respectively.