Cobalt-mediated cyclotrimerization and cycloisomerization reactions. Synthetic applications

Abstract

This article reviews our contribution in the field of the cobalt(I)-mediated cycliza- tions. The use of new unsaturated partners such as allenes extend the scope and the utility of the previously developed intramolecular (2a2a2) cyclotrimerization. The presence of chiral auxiliaries induced high level of diastereoselectivity in the enediynes cyclization. The discovery of cobalt(I) catalyzed ene-type reaction allows to propose an efficient route to the basic skeleton of tetracyclic diterpenes via a one-pot sequence of cyclizations: (ene-type)/ (2a2a2)/(4a2). This cascade created six carbon-carbon bonds, four rings in a totally stereoselective manner. Finally, a new strategy to the taxoids is proposed.