New Cobalt-Catalyzed Cycloisomerization of epsilon-Acetylenic beta-Keto Esters. Application to a Powerful Cyclization Reactions Cascade.
The full details of investigations into the cobalt(I)-catalyzed ene type reaction of epsilon-acetylenic beta-keto esters to form highly functionalized methylenecyclopentanes are described. The observed regio-, chemo-, and stereoselectivities support a process of cycloisomerization which controls the relative stereochemistry of two contiguous stereogenic centers. An efficient route to the basic skeleton of the phyllocladane family has been achieved via a one-pot sequence of cyclizations: ene type, [2 + 2 + 2], [4 + 2]. This new cascade created six carbon-carbon bonds and four rings in a totally stereoselective manner from an easily accessible acyclic polyunsaturated precursor.
Cruciani
Paul
P
Université Pierre et Marie Curie, Paris VI, Laboratoire de Chimie Organique de Synthèse, associé au CNRS, tour 44-54, B. 229, 4, Place Jussieu, 75252 - Paris Cedex 05, France.
Stammler
Robert
R
Aubert
Corinne
C
Malacria
Max
M