Air-stable, highly abundant, and cost-effective Co(III)-catalyzed redox-neutral [4 + 2]-annulation of aromatic sulfoxonium ylides with 1,3-diynes providing useful substituted 1-naphthol derivatives in a regioselective manner is described. Further, the prepared 1-naphthols having internal alkyne were converted into useful polycarbocyclic molecules and spiro-dienone derivatives in good-to-excellent yields. A possible reaction mechanism involving ortho C−H activation as a key step was proposed and supported by deuterium labeling and kinetic isotope labeling studies.
A Co(III)-catalyzed
redox-neutral [4 + 2] annulation of N-chlorobenzamides/acrylamides
with substituted alkenes
at ambient temperature is demonstrated. Using this protocol, pharmaceutically
important 3,4-dihydroisoquinolinone derivatives were synthesized in
good yields. Intriguingly, the synthetically useful functional group
of allylic coupling partners such as sulfonyl, carbonate, acetate,
phosphate, amide, nitrile, and silane were retained in the final cyclized
product. The present annulation reaction was compatible with various
substituted benzamides and allylic coupling partners. To support the
proposed reaction mechanism, competition experiments, deuterium labeling
studies, and kinetic isotope effect studies were performed.
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