3,4,5-Trimethylphenol and Lewis Acid Dual-Catalyzed Cascade Ring-Opening/Cyclization: Direct Synthesis of Naphthalenes.

A 3,4,5-trimethylphenol and Lewis acid dual-catalyzed cascade reaction of donor-acceptor (D-A) cyclopropanes via ring-opening and cyclization is developed. In this reaction, a phenolic compound was used as a covalent catalyst for the first time. Additionally, control experiments proved that 3,4,5-trimethylphenol completed the catalytic cycle by accomplishing the C-C bond cleavage. Using this strategy, a wide variety of substituted naphthalenes has been synthesized from D-A cyclopropanes in moderate to high yields under mild conditions.