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1,4-Rhodium-Silicon Shift in an Enantioselective Synthesis of IndanolsContributor(s):Mark Lautens, Jane Panteleev
ETH Zürich, Switzerland
Rhodium(I)-Catalyzed 1,4-Silicon Shift of Unactivated Silanes from Aryl to Alkyl: Enantioselective Synthesis of Indanol Derivatives
Angew. Chem. Int. Ed. 2010, 49: 10163-10167
16 February 2011 (online)
1,4-silicone shift - indanols - rhodium
The tendency of rhodium and palladium catalysts to undergo 1,4-shifts from alkyl or vinyl to aryl positions is a well-documented phenomenon (see Review). In contrast to their earlier work (Angew. Chem. Int. Ed. 2009, 48, 6320), the authors describe a 1,4-rhodium-silicon shift. This strategy is superior to the rhodium-hydrogen shift in the sense that functionality is introduced at the alkyl position, which can be easily further modified.
Review: F. Shi, R. C. Larock Top. Curr. Chem. 2010, 292, 123-164.
Several selectivity issues were addressed by this work. High enantioselectivity in β-carbon cleavage could be achieved for the trans products using Difluorphos or Dolefin ligands. The trans/cis selectivity of the ketone addition could be modulated by the solvent and the ligand used. Olefin ligands were selective for silicon versus hydrogen migrations, with phosphine ligands favoring hydrogen shifts. Tricyclic products could also be formed, possibly from a rhodium-catalyzed Si-alkyl insertion. The silicon group could easily be converted into an alcohol, and vinyl or allyl silyl groups could also participate in the migration.