Syntheses of 2‑Aroyl Benzofurans through Cascade Annulation on Arynes

The highly efficient
and expedient route for the syntheses of 2-aroyl
benzofurans has been developed via the cascade [2+2] followed by a
[4+1] annulation on arynes. The overall transformation proceeded through
the formation of ortho-quinone methide by the insertion
of transient aryne into N,N-dimethylformamide
and subsequent trapping with sulfur ylide. Moreover, this transformation
has a broad range of substrate scope with a high functional-group
tolerance. This new reaction was successfully utilized in the synthesis
of the potent CYP19 aromatase inhibitor and late-stage functionalization
on the bioactive complex estrone.