The conjugate addition of carbon nucleophiles to acceptor activated olefins is one of the most important reactions for carbon-carbon bond formation. With optically active metal complexes this transformation can be catalyzed enantioselectively. This review is a collection of the newer literature (since 2001) on this topic. The metal salts and complexes applied are in a broad range, starting from solely Lewis acidic M(II) and M(III) compounds, such as magnesium, zinc, boron, aluminum and the lanthanoids. Transitionmetal catalysts suitable for asymmetric conjugate additions are compounds of ruthenium, iridium, nickel, and palladium. The most flourishing fields are, however, the catalysis with rhodium and copper complexes. Rhodium catalysts often have a chiral diphosphane like BINAP, or an optically active olefin as the ligand, the latter being a newer development. The privileged ligand structures for copper catalysts are monodentate phosphoramidites with axially chiral BINOL or other biphenol units.

Convenient and direct: 1,4‐Dicarbonyl compounds are readily obtained through a one‐pot cerium‐catalyzed oxidative CC coupling in the presence of oxygen and subsequent fragmentation. The products are suitable precursors for heterocycles.

Three α‐cyclopropyl β‐dicarbonyl compounds have been used as probes for α‐radicals as electrophilic reaction intermediates in a cerium‐catalyzed α‐hydroxylation reaction with molecular oxygen. Since the cyclopropyl group did not ring‐open to products with a butenyl moiety, but was retained in the products, a localized unpaired electron at the α position can be excluded during the course of the reaction. The α‐cyclopropyl‐substituted substrates were prepared by aldol or Claisen reactions. Other substrates with α‐methyl, α‐isopropyl, and α‐tert‐butyl substituents were prepared and converted under the α‐hydroxylation conditions in order to estimate steric influences on the yield of the reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

1,4‐Diketones were prepared by cerium‐catalyzed oxidative coupling of styrene with molecular oxygen and 1,3‐dicarbonyl compounds. This two‐step sequence was performed as a one‐pot procedure without isolation of the intermediate products. The first step is a metal‐catalyzed radical reaction yielding 3‐hydroxy‐1,2‐dioxane derivatives being the cyclotautomers of initially formed 4‐hydroperoxy ketones. In the second step of this sequence, these endoperoxides are converted with AcCl–pyridine by Kornblum–DeLaMare fragmentation into the 1,4‐dicarbonyl motif. Several intermediate 1,2‐dioxane derivatives could be isolated and structurally characterized by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

A synthetic approach to the C17-benzene ansamycins via metal catalyzed C-C coupling is described. Key bond formations include direct iridium catalyzed carbonyl crotylation from the alcohol oxidation level followed by chelation-controlled Sakurai-Seyferth dienylation to form the stereotriad, which is attached to the arene via Suzuki cross-coupling. The diene-containing carboxylic acid is prepared using rhodium catalyzed acetylene-aldehyde reductive C-C coupling mediated by gaseous hydrogen. Finally, RCM delivers the cytotrienin core.Beginning with the discovery of the antibacterial rifamycin B, ansamycin antibiotics continue to evoke interest as antibiotic and antineoplastic agents. 1 An important ansamycin subclass is represented by the ansatrienins, which are classified as triene-containing C17-benzene ansamycins. Members of this subclass, which are produced from various Steptomyces and Bacillus species, include the mycotrienins and mycotrienols, 2 the trienomycins 3 and the cytotrienins (Figure 1).4 Whereas the mycotrienins exhibit potent anti-fungal activity,2d,e the trienomycins and cytotrienins display antineoplastic properties. 3a ,5 For example, cytotrienin A induces apoptosis in human acute promyelocytic leukemia HL-60 cells (ED50 = 7.7 nM). 5c Following their stereochemical assignment,6 total syntheses of trienomycins A and F and thiazinotrienomycin E were reported by Smith, 7a-c total syntheses of mycotrienol I and mycotrienin I were reported by Panek7d,e and a total synthesis of cytotrienin A was reported by Hayashi. 7f Finally, Kirschning and Panek reported syntheses of the ansatrienol and cytotrienin cores, respectively. 8 Here, we report initial efforts toward the development of a synthetic approach to triene-containing C17-benzene ansamycins featuring C-C bond forming hydrogenations and transfer hydrogenations developed in our laboratory. 9 Retrosynthetically, it was envisioned that diverse C17-benzene ansamycins may be accessed through modular assembly of fragments A-D. Specifically, Suzuki cross-coupling of vinyl bromide A and the organoboron building block B would deliver an arene-containing C11-C17 substructure. Chelation-controlled pentadienylation of the latent C11-aldehyde employing reagent C followed by reduction of the nitroarene and amidation of the resulting mkrische@mail.utexas.edu. Supporting Information Available. Characterization data for all new compounds ( 1 H NMR, 13 C NMR, IR, HRMS, [α]). This material is available free of charge via the internet at http://pubs.acs.org. High levels of anti-diastereo-and enantioselectivity are obtained using the isolated orthocyclometallated iridium C,O-benzoate precatalyst modified by (S)-SEGPHOS. As efforts toward corresponding syn-diastereoselective processes are underway, 11d the present firstgeneration synthesis requires conversion of the anti-adduct to the syn-diastereomer via Mitsunobu inversion employing p-nitrobenzoic acid 12 to deliver the crystalline pnitrobenzoate 3. Saponification of 3 followed by Williamson ether synthesis p...

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Eight-membered-ring lactams were prepared by the Bi-catalyzed reaction of 1,4-diketones with primary amines. These lactams define a new type of non-planar molecular scaffold with three points allowing for diversification, which were evaluated as the basis for combinatorial library synthesis. For this reason, reaction conditions were optimized, and the scope and limitations were investigated. After the Bi-catalyzed reaction, further diversification was achieved by ester

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