An improved protocol for the Friedel–Crafts alkylation of benzene as well as its methylated and halogenated derivatives with alkyl and benzyl bromides is reported. The reaction is promoted by a counteranion-stabilized silylium ion in the presence of stoichiometric amounts of a simple phenyl-substituted tetraorganosilane. This additive functions as a proton scavenger, regenerating the catalytically active silylium ion through protonation (protodesilylation) by the Wheland intermediate. It is a productive “proton-into-silylium ion” generator. The higher proton affinity of silylated compared with alkylated arenes results in fast proton transfer from the Brønsted acidic Wheland intermediate to the ipso position of that phenylsilane, thereby preventing otherwise competing defunctionalization and isomerization at the stage of the Wheland intermediate. The additive was also found to be crucial for turnover in the alkylation with primary alkyl bromides and for the suppression of transbenzylation in the benzylation with more reactive benzyl bromides.

中文翻译：

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通过 Protodesilylation 的甲硅烷离子再生使 Friedel-Crafts 烷基化具有更少的异构化和无去官能化

报道了苯及其甲基化和卤化衍生物与烷基溴和苄基溴的 Friedel-Crafts 烷基化的改进方案。在化学计量量的简单苯基取代的四有机硅烷存在下，反应由抗衡阴离子稳定的甲硅烷离子促进。这种添加剂起到质子清除剂的作用，通过惠兰中间体的质子化（原脱甲硅烷化）再生具有催化活性的甲硅烷离子。它是一种高效的“质子转化为甲硅烷离子”发生器。与烷基化芳烃相比，甲硅烷基化芳烃具有更高的质子亲和力导致质子从 Brønsted 酸性 Wheland 中间体快速转移到ipso苯基硅烷的位置，从而防止在 Wheland 中间体阶段的其他竞争性去官能化和异构化。还发现该添加剂对于用伯烷基溴化物进行烷基化的转换和抑制用更具反应性的苄基溴化物的苄基化中的转苄基化是至关重要的。