Modern Friedel-Crafts Chemistry. Part 38. Facile Synthesis of Acenaphthenes via Direct and Rearranged Intramolecular Friedel-Crafts Cyclialkylations of Intermediate Carbinols

Abstract

A novel one-pot synthesis of six di-, tri-, and tetra-substituted acenaphthenes 18a-f via direct and/or rearranged Friedel-Crafts cyclialkylations of seven novel carbinols 1a-g is described. The methodology involves treatment of alkanols 1a-g in the presence of both Brønsted (PPA, H₂SO₄) and Lewis (AlCl₃/CH₃NO₂) acid catalysts. The method offers several advantages such as high yields, high selectivities, and easily accessible starting materials. A plausible mechanism for this type of Friedel-Crafts cyclialkylation is proposed.

Key Words:

• α-Naphthylalkanols
• acenaphthenes
• Brønsted and Lewis acid catalysts
• Friedel-Crafts cyclialkylations
• Grignard reagents