Catalytic Asymmetric Cyclocarbonylation of Nitrogen-Containing Enynes.
The asymmetric Pauson-Khand type cyclization of nitrogen-containing enynes using carbon monoxide and a catalytic amount of (EBTHI)TiMe(2) was examined. The influence of the nitrogen substituent and the concentration of the catalyst on the enantioselectivity of this cyclization was explored, and it has been found that enynes with an octyl-, benzyl-, or allylamino group, positioned beta to the alkyne and the olefin, are cyclized with a high degree of enantioselectivity. Substrates with either bulky and/or electron-withdrawing nitrogen substituents are converted to products in low to moderate enantioselectivity.
Sturla
Shana J.
SJ
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
Buchwald
Stephen L.
SL