Garcia Yeimy, Schoenebeck Franziska, Legault Claude Y, Merlic Craig A, Houk K N
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
J Am Chem Soc. 2009 May 13;131(18):6632-9. doi: 10.1021/ja9004927.
Selectivity of the palladium-catalyzed cross-coupling reactions of heterocycles bearing multiple identical halogens is mainly determined by the relative ease of oxidative addition. This is related to both the energy to distort the carbon halogen bond to the transition-state geometry (related to the CX bond-dissociation energy) and to the interaction between the heterocycle pi* (LUMO) and PdL(2) HOMO (J. Am. Chem. Soc. 2007, 129, 12664). The computed bond dissociation energies of a larger series of halo-heterocycles have been explored with B3LYP and higher accuracy G3B3 calculations. Quantitative trends in bond dissociation energies have been identified for five- and six-membered chloro and bromo substituted heterocycles with N, O, and S heteroatoms.
含多个相同卤素的杂环钯催化交叉偶联反应的选择性主要由氧化加成的相对难易程度决定。这既与将碳卤键扭曲成过渡态几何形状所需的能量（与CX键解离能有关）有关，也与杂环π*（最低未占分子轨道）和PdL(2) 最高已占分子轨道之间的相互作用有关（《美国化学会志》，2007年，第129卷，第12664页）。已通过B3LYP和更高精度的G3B3计算研究了一系列更大的卤代杂环的计算键解离能。已确定了含N、O和S杂原子的五元及六元氯代和溴代取代杂环在键解离能方面的定量趋势。
