Regioselective Fries Rearrangement and Friedel−Crafts Acylation as Efficient Routes to Novel Enantiomerically Enrichedortho-Acylhydroxy[2.2]paracyclophanes

Two useful approaches to ortho-acylhydroxy[2.2]paracyclophanes, starting from 4-hydroxy[2.2]paracyclophane, have been developed. TiCl4-catalyzed Fries rearrangement and direct acylation occur regioselectively (to the ortho position with respect to the hydroxy group), leading to 4-acetyl-5-hydroxy[2.2]paracyclophane (3) and 4-benzoyl-5-hydroxy[2.2]paracyclophane (4) in high to excellent chemical yields. For compound 4, an X-ray investigation has been performed. ortho-Acylhydroxy[2.2]paracyclophanes 3 and 4 have been obtained in enantiomerically enriched forms (ee 92−99%) and the absolute configurations of their enantiomers have been determined.