Quinoline‐Based Silylium Ions: Synthesis, Structure and Lewis Acidity

Heteroarylsilyl cations elaborated from a quinoline skeleton have been prepared from the corresponding silanes, and their structures were studied by 1H, 29Si, and 15N NMR. DOSY experiments and DFT calculations were also carried out which showed that the silyl cation center is stabilized intramolecularly by the quinoline nitrogen atom (N1), forming a highly strained and quasi planar 4‐membered ring. Oxygenated and nitrogenated substituents at the C4 position on the quinoline ring were shown to reinforce the Si−N1 interaction through a p‐π conjugation. The Lewis acidity of this class of silylium was finally determined using Müller's nitrilium method. New quinoline silylium cations have been prepared and their structure unambiguously determined through extensive NMR studies supported by DFT calculations. The Lewis acidity of these silyl cations stabilized by internal Lewis basic sites has been estimated.