Platinum‐Catalyzed Formation of Cyclic‐Ketone‐Fused Indoles from N‐(2‐Alkynylphenyl)lactams

An oxygen atmosphere aids the efficient formation of highly substituted ring-fused indoles by the versatile title reaction through an initial cyclization followed by the sequential migration of two groups. The cycloisomerization can be viewed as a net intramolecular insertion of one end of the alkyne into the lactam amide bond with concurrent migration of the substituent at the alkyne terminus (see scheme; n=0–2; R=alkyl, alkenyl, aryl, H; R′=OMe, Br, CO2Et).