Asymmetric Intermolecular Pauson−Khand Reaction of Symmetrically Substituted Alkynes
作者:Yining Ji、Antoni Riera、Xavier Verdaguer
DOI:10.1021/ol901728r
日期:2009.10.1
The asymmetric intermolecularPauson−Khandreaction of symmetric alkynes has been accomplished for the first time. N-Phosphino-p-tolylsulfinamide (PNSO) ligands have been indentified as efficient ligands in this process. The chirality of the cobalt S-bonded sulfinyl moiety was found to direct olefin insertion into one of the two possible cobalt−carbon bonds in the alkyne complex. Reaction of symmetric
An efficient protocol for the generation of acylcobalt species from alkyne–[Co2(CO)6] complexes is realized by treatment of the complexes with AcOH and pyridine. The generated acylcobalt species smoothly underwent addition reactions with various alkenes to give alkyl alkenyl ketones in good yield (see scheme).
Medium sized trans-cycloalkenes are unusually reactive in the intermolecular Pauson-Khand reaction (PKR) with regard to typical monocyclic alkenes. This is due to the ring strain imparted by the E stereochemistry. The PKR of these alkenes offers a modular, regioselective and straightforward entry to trans fused [n.3.0] bicyclic scaffolds (n = 6-8).