Iridium-catalyzed enantioselective Pauson–Khand-type reaction of 1,6-enynes

Transition metals in organic synthesis: Highlights for the year 2005

“…(202) [1013], Japanese hop ether [1014], toward pactamycin [1015], core structure of asperparaline [1016] and magellanine [1017]. Iridium catalyzed asymmetric intramolecular Pauson-Khand reactions of 1,6-enynes [1018].…”

Asymmetric Catalytic Intramolecular Pauson–Khand Reactions with Ir(phox) Catalysts

“…High enantioselectivities were achieved with substrates 4a and 4c, which were comparable to those reported for Ir catalysts derived from tolbinap. [11,12] With substrates 4b and 6, on the other hand, tolbinap gives higher enantioselectivities. As with (diphosphane)iridium catalysts, relatively long reaction times are required.…”

“…[16] Spectroscopic data and rotation values of products 5a-c and 7 have been reported in the literature. [4][5][6][7][8][9][10][11][12] General Procedure for the Pauson-Khand Reaction: In a glove-box a flame-dried Young tube with a Teflon screw cap was charged with substrate (0.22 mmol), catalyst (2.2-20.0 µmol) and solvent (5 mL). The mixture was degassed with three freeze-pump cycles, the ampule filled with 2.2 bar of CO and sealed.…”

“…More recently, they extended the reaction to a wider range of substrates and also employed aldehydes as CO source. [12] In connection with our work on chiral phosphaneoxazolines (phox ligands) and their use in iridium-catalyzed asymmetric hydrogenation [13] we became interested in evaluating Ir(phox) complexes as catalysts for asymmetric Pauson-Khand reactions. Here we report the results of an initial study, which showed that high enantioselectivities and yields can be obtained in intramolecular reactions of en-ynes using readily available Ir(phox) complexes as catalysts.…”

Unique Metal‐Diyne, ‐Enyne, and ‐Enediyne Complexes: Part of the Remarkably Diverse World of Metal‐Alkyne Chemistry

“…Catalysts, such as CpCo(CO) 2 (366,367) and Fe(CO) 5 (368)(369)(370), have been shown to mediate carbonylative alkynealkyne coupling, but the cyclopentadienones are obtained as Z 4 metal complexes and oxidative demetallation is necessary to obtain uncomplexed cyclopentadienones. The recent development of catalytic transition metal-mediated carbonylative alkyne-alkyne coupling serves as a direct and effective synthesis of cyclopentadienones (371). The IrCl(CO)diphos catalyst promotes carbonylative alkyne-alkyne coupling to form cyclopentadienones in high isolated yields (Scheme 29).…”