One-Pot Triple and Mixed Double Michael Addition of Activated Alkenes to 2-Oxindole and 7-Aza-2-Oxindole: Synthesis of C-3/N-Functionalized Carbon Rich 2-Oxindole and 7-Aza-2-Oxindole Derivatives

A simple, efficient, and atom-economical, one-pot triple Michael Addition of activated alkenes to 2-oxindole, 7-aza-2- indolone, and N-methyl-5-bromo-7-aza-2-indolone has been developed. Significantly, multifunctionalities have also been achieved via one-pot mixed Michael addition using the equimolar amount of two different activated alkenes. The reaction provided C-3 and N-functionalized carbon-rich 7-aza-2-oxindole derivatives. The scope of the reaction using diverse activated alkenes has been tested to provide the title compounds. The structure of the representative compounds has been established by the XRD method. Synthetic transformation of representative compounds is demonstrated to provide the respective 3-spirooctane-2-oxindole derivatives in excellent yield. A plausible mechanism for cyclization is provided.