Chalice-type tridentate silicon Lewis acids of C3 symmetry in a single step starting from hexadehydrotri-benzo[12]annulene.

Tridentate Lewis acids with aligned functions were syn-thesized based on the rigid framework hexadehydrotribenzo[12]annu-lene. The backbone and its fluorinated analogue were synthesised in one-pot syntheses, with alkyne deprotection and Sonogashira cross coupling reaction being carried out in one step. Hydrosilylation of the annulene with chlorohydrosilanes proceeded highly selectively and afforded rigid poly-Lewis acids with three SiCl 3 or SiCl 2 Me substitu-ents perfectly oriented to one side of the molecule in a single step. The progress of hydrosilylation was investigated by time-correlated NMR spectroscopic studies. The crystal structures show that the framework is symme-trically functionalised and the silyl substituents are aligned in one direction. To increase the acidity of the Lewis acids the chlorosilyl substituents were fluorinated with SbF 3 . Further investigation of hydrometallation reactions (M = B, Al, Ga, Sn) did not lead to corresponding structures.