Photocatalytic activity of acridines with sterically hindered tetrahedral substituents in the 9 position is studied. A method for the synthesis of 9-silylacridines via lithiation/silylation sequence is described. The reactivity difference between silyl- and aryl-substituted analogs is due to geometric distortions.

A protocol for the synthesis of sterically hindered 9-silylacridines via lithiation/silylation sequence is developed. The photocatalytic efficiency of obtained acridines is tested in a variety of decarboxylative processes and compared with the properties of aryl- and alkyl-substituted analogs. To explain the observations, quantum chemical calculations are carried out, revealing the features of the spatial structures of these molecules.