A diastereoselective
Co2(CO)8-mediated Pauson–Khand reaction
(PKR) of siloxy-tethered 1,7-enynes for the synthesis of cyclopentaoxasilinones
has been developed. This transformation can be performed on a multigram
scale and is characterized by a broad substrate scope, functional
group compatibility, and high chemo- and diastereoselectivity. Oxidation
of the resulting cyclopentaoxasilinones delivers stereoenriched
β-alkylated cyclopentenones, which are inaccessible by intermolecular
PKRs. This research provides a practical solution to the challenges
associated with the classical intermolecular PKR.
A diastereoselective Co<sub>2</sub>(CO)<sub>8</sub>-mediated
Pauson-Khand reaction (PKR) of siloxy-tethered 1,7-enynes for the synthesis of
cyclopentaoxasilinones has been developed. This transformation can be performed
on a multi-gram scale and is characterized by broad substrate scope, functional
group compatibility, and high chemo- and diastereoselectivity. Oxidation of the
resulting cyclopentaoxasilinones delivers stereoenriched β-alkylated
cyclopentenones, which are inaccessible by intermolecular PKRs. This research
provides a practical solution to the challenges associated with the classical
intermolecular PKR.
(E)- and (Z)-isocyanoalkenes
were selectively synthesized via the sequential cross coupling of
vinyl iodides with formamide, followed by dehydration. The optimal
catalyst, generated in situ from CuII and trans-N,N′-dimethyl-1,2-cyclohexanediamine, rapidly coupled (E)- or (Z)-vinyl iodides with formamide, which minimized
the isomerization of the resultant vinyl formamide. The method efficiently
provided a range of acyclic, carbocyclic, and heterocyclic isocyanoalkenes;
the versatility is illustrated with the selective, stereodivergent
syntheses of the diastereomeric isocyanoalkene antibiotics, B371 and E-B371.
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