A regioselective C-H arylation using aryl halides can be achieved through coordination-assisted control. For instance, the weak chemical co-ordination of a directing group to cationic arene π-complex can be pivotal in the determination of regioselectivity and the rate of the C-H activation reaction. In 2016, Nelson and co-workers reported the arylation of sp3 and sp2 C-H bonds with a β-trimethylsillane (TMS) directing group.1 In contrast, C-H activation reaction does not proceed in quantitative yields in the absence of the β-silicon directing group. In order to rationalize such experimental findings, we performed computational analysis on the C-H activated arylation reaction to unravel the substitution effect of TMS group. Specifically, we identified transition state structures and reaction barriers for ortho, meta and para-TMS-AR molecules. Our results suggest that ortho-TMS substituent stabilizes the cationic-arene complex TS more than that of meta-TMS and para-TMS substituents (ortho-TMS-AR: 14 kcal/mol &lt; meta-TMS -AR:18 kcal/mol &lt; para-TMS-AR:23 kcal/mol). Furthermore, absolutely localized molecular orbital-based energy decomposition analysis (ALMO-EDA) was performed to quantify the effect of directing groups during C-H Activation reaction, where the stabilization of the transition state was traced to a most significant charge transfer from the β-TMS group to arene cations.

Mechanistic insights into regioselective CH activation reactions

ACS Spring Meeting 2021

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