Benzene and substituted derivatives (toluene, ortho-xylene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, anisole), when applied in large excess, react with 1,4 diols (pentan-1,4-diol, hexan-2,5-diol, and 2,5-dimethylhexan-2,5-diol) or an oxolane (2,2,5,5-tetramethyltetrahydrofuran) in the presence of the Brønsted superacid trifluoromethanesulfonic acid (triflic acid, TFSA) to afford substituted tetralins in excellent yields with high selectivity. Reacting benzene with a small excess of alkylating agents yields octahydroanthracenes. The transformation of naphthalene with oxolane leads to a partially saturated octamethyloctahydrotetracene under similar conditions. Product formation is interpreted by intermolecular Friedel-Crafts alkylation followed by cyclialkylative ring closure.
Alkylation Cyclialkylation Arenes Carbocations Superacid
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Olah GA, Prakash GKS, Sommer J (1985) Superacids. Wiley-Interscience, New YorkGoogle Scholar