Beilstein J. Org. Chem.2011,7, 601–605, doi:10.3762/bjoc.7.70
cyclobutene; allene; allenyloxindole; chiral lanthanide shift reagent; chiraltransfer; Introduction
The [2 + 2] cycloaddition reaction of allenes and alkynes provides rapid entry into synthetically challenging alkylidene cyclobutene ring systems. We, along with others, have demonstrated the intramolecular
resembling compound 2, gave the racemic spirooxindole product. This finding will be discussed in detail in a full account of this work.
To examine the chiraltransfer from the propargylic acetate 7 to the allenyloxindole 8, a chiral 1H NMR shift analysis was performed using (+)-Eu(hfc)3. The NMR spectra of
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Graphical Abstract
Scheme 1:
Conversion of propargyl acetate 1 to spirooxindole 2 containing the core framework of welwitindolin...