Two catalytic benzannulation/1,4-addition cascades of available enynones with indoles
or tetronic acid-derived enamino lactones as C-nucleophiles are reported, producing
53 examples of heterocycle-incorporating diarylmethanes with moderate to excellent
yields. The combination of AgOTf and Sc(OTf)3 permits bimetallic synergistic catalysis of the reaction of enynones with indoles
to access 35 triarylmethanes in generally good yields with ortho-naphthoquinone methides, generated in situ, as the key intermediates. Exchanging
indoles for tetronic acid-derived enamino lactones resulted in 18 diarylmethanes by
the Ag-catalyzed benzannulation/1,4-addition cascade. Both reactions are advantageous
for their high atom utilization and mild reaction conditions, providing intriguing
complementary approaches for the direct syntheses of new heterocycle-containing diarylmethanes.
Key words
triarylmethanes - diarylmethanes - benzannulation - 1,4-addition - cascade reaction
- enamino lactones