Structural and Rate Studies of the 1,2-Additions of Lithium Phenylacetylide to Lithiated Quinazolinones: Influence of Mixed Aggregates on the Reaction Mechanism

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• 作者：Timothy F. Briggs ; Mark D. Winemiller ; David B. Collum ; Rodney L. Parsons ; Jr. ; Akin H. Davulcu ; Gregory D. Harris ; Joseph M. Fortunak ; and Pat N. Confalone
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：May 5, 2004
• 年：2004
• 卷：126
• 期：17
• 页码：5427 - 5435
• 全文大小：183K
• 年卷期：v.126,no.17(May 5, 2004)
• ISSN：1520-5126

文摘

The 1,2-addition of lithium phenylacetylide (PhCCLi) to quinazolinones was investigated usinga combination of structural and rate studies. ⁶Li, ¹³C, and ¹⁹F NMR spectroscopies show that deprotonationof quinazolinones and phenylacetylene in THF/pentane solutions with lithium hexamethyldisilazide affordsa mixture of lithium quinazolinide/PhCCLi mixed dimer and mixed tetramer along with PhCCLi dimer.Although the mixed tetramer dominates at high mixed aggregate concentrations and low temperaturesused for the structural studies, the mixed dimer is the dominant form at the low total mixed aggregateconcentrations, high THF concentrations, and ambient temperatures used to investigate the 1,2-addition.Monitoring the reaction rates using ¹⁹F NMR spectroscopy revealed a first-order dependence on mixeddimer, a zeroth-order dependence on THF, and a half-order dependence on the PhCCLi concentration.The rate law is consistent with the addition of a disolvated PhCCLi monomer to the mixed dimer. Investigationof the 1,2-addition of PhCCLi to an O-protected quinazolinone implicates reaction via trisolvated PhCCLimonomers.