Friedel–Crafts acetylation and benzoylation of benzylsilanes and xanthenes

The synthesis of p-acetyl and p-benzoyl derivatives of various benzylsilanes (p-R1CO–C6H4–CR2R3–SiMe3: R1, R2, R3=Me, H, H; Me, H, Ph; Me, H, Me; Me, Me, Me; Ph, H, H; Ph, H, Ph; Ph, H, Me; Ph, Me, Me), xanthenes (3-benzoyl and 3,6-dibenzoyl), and 9-Me3Si-xanthenes (3-benzoyl, 3,6-dibenzoyl, 3-acetyl and 3,6-diacetyl) using Friedel–Crafts reactions and typical Lewis acid catalysts (AlCl3, FeCl3, ZnCl2) is described. Desilylation side reactions caused by AlCl3 become significant in substrates with weak carbon–silicon bonds (e.g. Ph2CH–SiMe3), and in the case of Ph3C–SiMe3 only the desilylation product Ph3CH was isolated.