Aroyl Isocyanates as 1,4-Dipoles in a Formal [4 + 1]-Cycloaddition Approach toward Oxazolone Construction.
Kaitlyn E EckertBrandon L AshfeldPublished in: Organic letters (2018)
A formal phosphine-mediated [4 + 1]-cycloaddition between a 1,2-dicarbonyl and an aroyl isocyanate to provide oxazolones bearing a disubstituted C5 center is described. By exploiting the carbene-like reactivity of oxyphosphonium enolates as C1 synthons and aroyl isocyanates as formal 1,4-dipoles, oxazolones and spiroooxindole oxazolones are constructed in high yields (39-99%).
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