Silicon-Tether Strategy for the Synthesis of Tetraphenylammonium

A traceless silicon-tether strategy enables the synthesis of tetraphenylammonium (Ph4N⁺) via intramolecular arylative quaternization.The key cyclization step proceeded in 1.2% yield, a 12-fold improvement over the intermolecular approach (0.1%).Subsequent twostep desilylation furnished the target Ph4N⁺.DFT calculations suggest β-silicon stabilization in the cyclization transition state, although competing pathways are kinetically favored.This work highlights the potential of intramolecular designs for accessing sterically hindered organic cations. Main textTetraarylammonium cations (Ar4N⁺)-defined herein as cations bearing four independent aryl groups on a central nitrogen atom (i.e., excluding tethered or fused analogues)-remain challenging to access despite their structural simplicity and emerging importance as organic cation scaffolds.1 We recently reported the first synthesis of tetraphenylammonium (Ph4N⁺, Figure 1a, left), a critical benchmark in this class.2 Due to its high stability under strongly basic conditions, Ph4N⁺ holds promise for phase-transfer catalysts and anion-exchange membranes in fuel cells.Moreover, its S4-symmetric arrangement of phenyl groups makes it a candidate for nonlinear-optical materials.3,4 The original synthesis of Ph4N⁺ relied on radical-based intermolecular arylative quaternization (ArQ), in which a