A new efficient and selective synthesis of ketones from alkanes or cycloalkanes, CO, and silanes in the presences of aprotic superacids

A new approach to the direct synthesis of ketones from alkanes or cycloalkanes (RH), CO, and silanes is proposed. Ketones were obtained in 50–97% yields from propane, butane, cyclopentane, cyclohexane, and methylcyclopentane on treatment with CO and silanes (Me₄Si, Et₄Si, orm- andp-XC₆H₄SiMe₃, where X=Cl, Me, OMe) in the presence of CX₄·2AlBr₃ (X=Br, Cl) superacids at 0°C. The reactions withm- andp-XC₆H₄SiMe₃ (X=Cl, Me) occur regioselectively to givem-ketones fromm-silanes andp-ketones fromp-silanes. However, the only product,p-MeOC₆H₄COR, is formed both fromm- andp-MeOC₆H₄SiMe₃. The reaction ofcyclo-C₅H₉CO⁺ with BzSiMe₃ results in an organosilicon ketone, Me₃SiCH₂C₆H₄COC₅H₉, while in the presence of an excess of an acylating system (after alcoholysis), Me₂Si(OR′)CH₂C₆H₄COR is formed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 947–952, May, 1998.