Mechanistic evidence suggests that the Lewis acid-promoted allylic rearrangement of alpha-silyloxy allylic silanes proceeds along an ionic reaction pathway involving a contact ion pair. The driving force for this transformation is alleviation of steric congestion at the allylic position of the alpha-silyloxy allylic silane and stabilization of pi cc by hyperconjugation.
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http://dx.doi.org/10.1021/jo070634p | DOI Listing |
J Org Chem
August 2014
Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON M5S 3H6, Canada.
The stereoselective synthesis of (+)-antimycin A1b has been accomplished in 12 linear steps and 18% overall yield from (-)-ethyl lactate. A robust, scalable, and highly diastereoselective montmorillonite K10-promoted allylation reaction between an α-silyloxy aldehyde and a substituted potassium allyltrifluoroborate salt provides a general approach to the core stereochemical triad of the antimycin A family. The requisite (Z)-substituted potassium allyltrifluoroborate salt was synthesized using a syn-selective hydroboration/protodeboration of an alkynylboronate ester, followed by a Matteson homologation reaction.
View Article and Find Full Text PDFOrg Lett
March 2010
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
Organozinc, -magnesium, and -lithium nucleophiles initiate a Brook/Ireland-Claisen rearrangement sequence of allylic silyl glyoxylates resulting in the formation of gamma,delta-unsaturated alpha-silyloxy acids.
View Article and Find Full Text PDFJ Org Chem
August 2007
Department of Chemistry, University of California, Irvine, California 92696-2025, USA.
Mechanistic evidence suggests that the Lewis acid-promoted allylic rearrangement of alpha-silyloxy allylic silanes proceeds along an ionic reaction pathway involving a contact ion pair. The driving force for this transformation is alleviation of steric congestion at the allylic position of the alpha-silyloxy allylic silane and stabilization of pi cc by hyperconjugation.
View Article and Find Full Text PDFJ Org Chem
March 1999
Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901.
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