Intermolecular Electrophilic Germylation Using GeCl 4 and Al 2 Cl 6

ABSTRACT Electrophilic aromatic substitution is a textbook transformation for the lighter Group 14 elements. In contrast to acylation, alkylation, and silylation, electrophilic germylation is extremely underdeveloped. Herein we report the first effective intermolecular Germa–Friedel–Crafts reaction. Specifically, combining the key industrial precursor GeCl 4 , with Al 2 Cl 6 and an inexpensive hindered pyridine base enables electrophilic C‐H germylation of a range of arenes. The process can be applied for selective synthesis of either the mono‐ or the di‐aryl germanes, ArGeCl 3 and Ar 2 GeCl 2 , respectively. ArGeCl 3 are versatile intermediates that can be transformed in situ into the synthetically desirable ArGe(alkyl) 3 derivatives. Mechanistic and computational analysis support an S E Ar‐type process where Al 2 Cl 6 is the key halophilic activator that generates a germanium electrophile able to effect C–H germylation in combination with the base. Overall, this work demonstrates that a high‐yielding intermolecular Germa–Friedel–Crafts reaction is possible provided an appropriate Brønsted base is used.