Diminished Reactivity of Ortho-Substituted Phenacyl Bromides toward Nucleophilic Displacement
作者:Diane M. Kalendra、Barry R. Sickles
DOI:10.1021/jo011042o
日期:2003.2.1
with increasing electron-withdrawing ability (k x 10(3) L M(-1) min(-1) = 12.7 (p-CH(3)), 15.7 (o-F), 20.5 (H), 20.0 (p-Cl), 23.6 (m-Cl), 27.3 (p-CF(3))). Within an ortho-substituted series, the reactivities decrease (k x 10(3) L M(-1) min(-1) = 7.64 (o-OCH(3)), 5.31 (o-CH(3)), 2.85 (o-Cl), 2.40 ( o-CF(3))). Ortho-substitution results occur from rotational barrier effects and an Adelta(sigma)+ Bdelta(sigma)+
观察到叔丁基胺对α-溴苯甲酮的取代率的系统提高,其中间或对取代基的吸电子能力增强(kx 10(3)LM(-1)min(-1)= 12.7(p-CH( 3)),15.7(oF),20.5(H),20.0(p-Cl),23.6(m-Cl),27.3(p-CF(3)))。在邻位取代系列中,反应性降低(kx 10(3)LM(-1)min(-1)= 7.64(o-OCH(3)),5.31(o-CH(3)),2.85(o -Cl),2.40(o-CF(3)))。邻位取代的结果来自旋转势垒效应和Adeltaσ+Bdeltaσ+排斥力。反应和α-取代中心(AB)之间的主要键作用只是sigma键。当在A和B之间允许π键键合(元/对位取代)时,发生反应中心的离域和稳定化。