Unusual [3+2] Spiroannulation and Creation of Stereogenic Quaternary Center at C‐3 of Oxindole via Addition of (Het)arynes to Isomerized Morita‐Baylis‐Hillman Adduct of Isatin

Abstract A one‐pot synthesis of 1′‐methyl‐2′‐oxospiro [indene‐1, 3′‐indoline] and 3,3‐disubstituted 2‐oxindole derivatives in excellent combined yield by the reaction of methoxy isomerized MBH adducts of isatin with arynes and heteroarynes has been achieved. A plausible mechanism invoking a [3+2]‐spiro‐ annulation reaction and quenching the intermediate with proton is explained. Formation of regioselective products from unsymmetrical arynes is explained based on reactivity profiles of arynes/heteroarynes. Synthetic utility of synthesized compounds have been demonstrated.