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DOI: 10.1055/s-0029-1220134
Synthesis of Isochromans by Palladium-Catalyzed C-H Olefination
Y. Lu, D.-H. Wang, K. M. Engle, J.-Q. Yu*
The Scripps Research Institute, La Jolla, USA
Publikationsverlauf
Publikationsdatum:
22. Juni 2010 (online)
Significance
The synthesis of isochromans 3 from tertiary alcohols 1 and alkenes 2 via a palladium-catalyzed hydroxyl-directed C-H olefination-intramolecular oxidative cyclization sequence is described. Optimization of the reaction conditions showed that the amino acid ligand shown is critical for high conversion. Instructively, hexafluorobenzene is preferred to toluene to avoid competing olefination of the solvent. In general, yields were higher with electron-rich arenes (R¹ = Me, OMe) compared to electron-poor ones (R¹ = Hal, CF3). The EWG on the alkene is required since only the uncyclized olefins 4 were isolated with electron-neutral alkenes (R4 = alkyl, aryl). The methodology was extended to secondary and primary alcohols (5-8), although the yields were somewhat low due to competing decomposition of the starting materials.