Subscribe to RSS
DOI: 10.1055/s-0028-108433
Coupling of Acetylene and Aldehydes Applied to l-Hexoses Synthesis
Contributor(s):Mark Lautens, Frédéric MénardUniversity of Texas at Austin, USA
Catalyst-Directed Diastereoselectivity in Hydrogenative Couplings of Acetylene to α-Chiral Aldehydes: Formal Synthesis of All Eight l-Hexoses
Org. Lett. 2008, 10: 4133-4135
Publication History
Publication Date:
23 October 2008 (online)
Key words
rhodium - acetylene - hydrogenative coupling - l-hexoses
Significance
A ligand-controlled stereoselective formal butadiene addition to α-branched aldehydes is reported. By simply using enantiomeric MeO-BIPHEPs, diastereomeric allylic alcohols can be obtained with good to high selectivity. The substrate chirality can be overridden by the catalyst even in mismatched cases. The synthetic utility of the method was demonstrated by intercepting four intermediates that have been used in the synthesis of all eight l-monosaccharides by Sasaki and Ermolenko (J. Org. Chem. 2006, 71, 693).
Comment
The atom-economical coupling reported follows a communication from the same group which employed a racemic BIPHEP ligand and showed no substrate control (J. Am. Chem. Soc. 2006, 128, 16040). The catalytic cycle involves first an oxidative cyclometalation between two acetylene molecules and a hydridorhodium species. The metallacycle then adds stereoselectively to the aldehyde. Formation of a metallacycle is crucial to control the Z-geometry of the alkene in the final products.
Review
E. Skucas, M.-Y. Ngai, V. Komandury, M. J. Krische Acc. Chem. Res. 2007, 40, 1394-1401.