A diastereoselective Co2(CO)8-mediated Pauson−Khand reaction (PKR) of siloxy-tethered 1,7-enynes for the synthesis of cyclopentaoxasilinones has been developed. Oxidation of the resulting cyclopentaoxasilinones delivers stereoenriched β-alkylated cyclopentenones, which are inaccessible by intermolecular PKRs. Since its initial discovery in 1973, the intra- and intermolecular PKRs have been exemplified as a convergent, atom-economical, and fundamental reaction for the [2+2+1] synthesis of cyclopentenones. However, the intermolecular PKR has generally been limited to strained or symmetrical alkenes due to the difficulty controlling the alkene regio- and stereoselectivity. Therefore, a general stereoselective PKR strategy to access highly functionalized monocyclic cyclopentenones remains an unsolved challenge. Herein, we describe the use of 1,7- enynes bearing a removable silicon tether, that upon oxidation of the Si-C bond, gives rise to highly functionalized and stereoenriched monocyclic cyclopentenones bearing functionalizable handles, allowing the rapid introduction of stereochemical complexity and structural diversity. We are currently developing a catalytic variation of the above method that invokes the ex-situ formation of carbon monoxide, as well as exploring the use of the more labile tethers to access monocyclic cyclopentenones in milder reaction conditions.

Access to highly functionalized cyclopentenones via diastereoselective pauson-khand reaction of siloxy-tethered 1,7-enynes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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