Synthesis and Reactivity of Cross-Conjugated Polyenones with a Planar Chirality

Abstract

The complexes 6 are the first examples of a novel class of cross conjugated polyenones bearing a planar chirality introduced by an organometallic moiety. Their synthesis is described using, as a key intermediate, the easily accessible new phosphorane 9. The free double bond of the selectively protected polyenes 6 reacts efficiently, although with low diastereoselectivities, in Diels−Alder or 1,3 dipolar cycloaddition reactions or with nucleophiles. Cyclopentyl radical also adds to 6, and this is the first example of a radical reaction in the presence of carbonyliron complexes. Decomplexation of the various adducts leads, in good yields, to the corresponding polyfunctionalized free dienes, which can be of further synthetic use.