Ruthenium-catalyzed intramolecular cyclization of diazo-β-ketoanilides for the synthesis of 3-alkylideneoxindoles

With [Ru(p-cymene)Cl-2](2) as catalyst, diazo-beta-ketoanilides would undergo intramolecular carbenoid arene C-H bond functionalization to afford 3-alkylideneoxindoles in up to 92% yields. The reaction occurs under mild conditions and exhibits excellent chemoselectivity. The lack of primary KIE (k(H)/k(D) similar to 1) suggests that the reaction should not proceed by rate-limiting C-H bond cleavage; a mechanism involving cyclopropanation of the arene is proposed.