Beilstein J. Org. Chem.2011,7, 601–605, doi:10.3762/bjoc.7.70
oxindoles into chiral non-racemic spirooxindoles containing an alkylidenecyclobutene moiety. The enantiomeric excesses were determined by chiral lanthanide shift NMR analysis and the transfer of chiral information from the allene to the spirooxindole was found to be greater than 95%.
Keywords: alkylidene
cyclobutene; allene; allenyloxindole; chiral lanthanide shift reagent; chiral transfer; Introduction
The [2 + 2] cycloaddition reaction of allenes and alkynes provides rapid entry into synthetically challenging alkylidenecyclobutene ring systems. We, along with others, have demonstrated the intramolecular
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Graphical Abstract
Scheme 1:
Conversion of propargyl acetate 1 to spirooxindole 2 containing the core framework of welwitindolin...
Beilstein J. Org. Chem.2010,6, No. 33, doi:10.3762/bjoc.6.33
rearrangement of the propargyl acetate 9a using transition metal catalysis (AuCl3 10 mol %, toluene, 1 h, rt) led to hydrolysis of the allenyl acetate functionality.
This densely functionalized alkylidenecyclobutene 10a is postulated to arise via the [2 + 2] cycloaddition reaction between the alkyne and the
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Graphical Abstract
Figure 1:
Heterocyclic and carbocyclic spirooxindoles.