Formylation and acylation reactions catalysed by trifluoromethanesulphonic acid

Abstract

Regioselective formylation of toluene, m- and p-xylene, and mesitylene has been achieved by carbonylation in trifluoromethanesulphonic acid at CO pressures of 90–125 atm. In the case of cumene, the formylation reaction is in competition with disproportionation to form di- and tri-isopropylbenzenes, leading to a complex product mixture. Slow addition of cyclohexene or cyclopentene to a mixture of benzene and CF₃SO₃H under a high CO pressure affords 4-cyclohexylbenzaldehyde and 4-cyclopentylbenzaldehyde in 34% and 33% yields, respectively, while 2-methylbut-1-ene gives 2,2,3-trimethylindanone (39%) under similar conditions. When cyclohexene is mixed with the acid under carbon monoxide (120 atm) before addition of benzene the major products are cyclohexyl phenyl ketone and cyclohexenyl cyclohexyl ketones.