Carbonylation of Methylcyclopentane and Cyclohexane Initiated by the Aprotic Organic Superacid CBr4·2AlBr3

The aprotic organic superacid CBr₄·2AlBr₃ initiates carbonylation of methylcyclopentane 1 and cyclohexane 2 with CO at atmospheric pressure with formation (after EtOH treatment) of various products in high yields depending on the conditions. The products are esters of 1-methylcyclopentanecarbonic (1a; at –45 °C) and cyclohexanecarbonic (2a; at 0 °C) acids and 2-methylcyclohexanone (3; at –23 °C); the reaction mechanism is discussed.