Substituent Effects in Benz[<i>a</i>]anthracene Carbocations: A Stable Ion, Electrophilic Substitution (Nitration, Bromination), and DFT Study
作者:Kenneth K. Laali、Maria A. Arrica、Takao Okazaki、Ronald G. Harvey
DOI:10.1021/jo070936r
日期:2007.8.31
computed relative energies by DFT. Charge delocalization paths in the resulting carbocations were deduced based on the magnitude of Δδ13C values. For the thermodynamically more stable C-12 protonated carbocations, the charge delocalization path is analogous to those derived based on computed NPA charges for the benzylic carbocations formed by 1,2-epoxide (bay-region) and 5,6-epoxide (K-region) ring opening
在FSO 3 H / SO 2 ClF中通过低温质子化作用,由异构的单烷基化和二烷基化的苯并[ a ]蒽(BAs)生成了一系列新型的碳正离子化反应。C-7具有单烷基衍生物(5-甲基,6-甲基,7-甲基和7-乙基)以及D环甲基化类似物(9-甲基,10-甲基和11-甲基),或在所有情况下均观察到C-12质子化的碳正离子(作为唯一或主要的碳正离子)。12-甲基衍生物的质子化(9)得到C-7质子化的碳正离子(9H +)作为动能种类和本位-protonated碳阳离子(9AH +)作为热力学阳离子。与12-乙基衍生物(10),在箱式区域空间张力的浮雕大大有利于本位-protonation(10AH +)。具有3,9-二甲基(14),C-7质子化(14H +)(C-12质子化<10%)受到强烈青睐,在1,12-二甲基(15)的情况下,观察到的唯一物质是C-7质子化的碳正离子化(15H +)。对于7-甲