Transition metal complexes in organic synthesis. Part 47. Organic synthesis via tricarbonyl(eta 4-diene)iron complexes

The protection of conjugated dienes by coordination to the tricarbonyliron fragment offers many potential applications of the resulting complexes to o rganic synthesis. The preparation of tricarbonyl(eta(4)-1,3-diene)iron comp lexes is readily achieved by a 1-azabutadiene-catalyzed complexation of the free ligands, An asymmetric catalytic complexation of prochiral cyclohexa- 1,3-dienes with pentacarbonyliron using chiral 1-azabutadienes affords chir al nonracemic complexes, The chiral tricarbonyliron complexes of acyclic bu tadienes represent versatile starting materials for the synthesis of a broa d range of polyunsaturated natural products. Consecutive carbon-carbon and carbon-nitrogen bond formations of the tricarbonyliron-cyclohexa-1,3-diene complexes and arylamines provide many biologically active carbazole alkaloi ds and a tetracyclic subunit of the discorhabdin alkaloids, The iron-mediat ed [2+2+1] cycloaddition of trimethylsilylacetylenes and carbon monoxide af fords stable 2,5-bis(trimethylsilyl)-substituted cyclopentadienones which a re useful substrates for further cycloadditions.