Substrate control of diastereoselectivity in zirconium (II) mediated enyne cyclizations
作者:Brian L. Pagenkopf、Eric C. Lund、Tom Livinghouse
DOI:10.1016/0040-4020(94)01130-r
日期:1995.4
The reductive cyclization of an extensive series of chiral enynes by Cp2Zr(II) complexes has been examined. In most instances excellent substrate control of cyclization stereochemistry was observed.
Starting from methyl 2-siloxycyclopropanecarboxylates simple and efficient one-pot procedures are described that lead to beta-cyanoesters and methoxycarbonyl-substituted terminal alkynes. The prepared functionalized alkynes were subjected to typical transformations such as [3+2] cycloaddition providing triazole derivatives, Sonogashira coupling, Au-catalyzed hydrophosphorylation or a copper-catalyzed coupling of methyl diazoacetate furnishing alkyne 14 and allene derivative 15. The Pauson-Khand reaction of the enyne 4c afforded a diastereomeric mixture of methyl 5-oxohexahydropentalen-2-carboxylate 16 in moderate yield.