Regioselective fries rearrangement and friedel-crafts acylation as efficient routes to novel enantiomerically enriched ortho-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.
The Photo-Fries Rearrangement of 2,5-Disubstituted Phenyl Acetates
In a homogenous solution, the photo-Fries rearrangement of 2,5-disubstituted phenyl acetates gives ortho-hydroxyacetophenones as major photoproducts.The ortho/para ratio can be increased by using a highly viscous medium or restricted spaces such as those in zeolites.On the other hand, micellar solutions have little effect.
Suau, Rafael,Torres, Gregorio,Valpuesta, Maria
p. 1311 - 1314
(2007/10/02)
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