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Enhanced diastereoselectivity in asymmetric crotylation reactions using propargylic dicobalt hexacarbonyl complexes
1Department of Chemistry, Metcalf Center for Science and Engineering, 590 Commonwealth Avenue, Boston University, Boston, MA 02215, USA.
Organic Letters
|August 3, 2001
Abstract:
[reaction: see text] Hexacarbonyl dicobalt complexes of propargylic acetals undergo Lewis acid catalyzed crotylation reactions with enhanced levels of diastereoselectivity (dr 6 to >20:1, syn/anti) while efficiently producing stereochemically well-defined homoallylic ethers. These results are in contrast to uncomplexed propargylic acetals, which undergo the crotylation reactions with low selectivity (dr < 2:1, syn/anti). After removal of the cobalt complex, the reactions afford propargylic ethers in high yields.