The synthesis of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudo benzylic position has been achieved via a 'transition-metal-free' intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon-carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction.
Kumar, N., Ghosh, S., Bhunia, S., & Bisai, A. (2016). Synthesis of 2-oxindoles via “transition-metal-free” intramolecular dehydrogenative coupling (IDC) of sp2 C-H and sp3 C-H bonds. Beilstein Journal of Organic Chemistry, 12, 1153–1169. https://doi.org/10.3762/bjoc.12.111