CHIRAL AUXILIARIES, LIGANDS AND ARENE CHROMIUM COMPLEXES

Sequential addition of organolithium compounds and allyl- or propargyl bromide to (phenyloxazoline) Cr(CO)(3) gave 1-oxazolyl-5,6-trans-disu bstituted cyclohexadienes. Regioselective radical (SnBu(3)) addition t o the alkyne and cyclization of the vinylic radical to the diene moiet y afforded fused bicyclic ring systems. Depending on whether the react ion was carried out with a terminal or internal alkyne, the reaction g ave either cis-fused tetrahydroindanes or bicyclo[3.2.1]octenes select ively. Asymmetric methodologies for the synthesis of diastereo- or ena ntioenriched cyclohexadienes via temporary complexation of the arene t o the electrophilic Cr(CO)(3) include chiral auxiliaries on the arene (oxazolines, SAMP-hydrazone), chiral ligands at Cr, chiral nucleophile s (organolithium reagents modified by chiral ligands) and planar chira l complexes synthesized via enantioselective lithiation. The article c ontains new developments and examples of the first and third approach of this asymmetric dearomatization methodology.