Lewis-acid catalyzed dehydrative [3+2] cycloaddition reaction: A facile synthetic approach to spiro-benzoindoline oxindoles

Modular synthesis of spirocyclic carbonates: unravelling the synergistic interplay of electronic and electrostatic sites on phenolic catalyst

“…36,37 Alternatively, the ring expansion routed through cycloaddition and annulation reactions helps to retain the spirocyclic scaffold with the advantage of reactivity and atom economy. 22,38,39 Intrigued by these later advancements and inspired by the catalytic power of our recently reported phenolbased organocatalyst in an aprotic polar solvent, 34 we envisioned exploring its activity towards the installation of CO 2 in spiro-fused oxirane 1a (Fig. 2).…”

Selective C3-Allylation and Formal [3 + 2]-Annulation of Spiro-Aziridine Oxindoles: Synthesis of 5′-Substituted Spiro[pyrrolidine-3,3′-oxindoles] and Coerulescine

“…Spiroaziridine oxindole 1 is the smallest spiro-aza-cycle of oxindoles, and a new subgroup of aziridine has recently been developed and explored by our group as a brilliant building block to access several 3,3-disubstituted- and spiro-oxindole compounds and attracted the attention of others too . The unprecedented reactivity of spiroaziridines toward various carbon/hetero nucleophiles is due to its ingrained ring strain and unique position of the oxindole nitrogen toward anchimeric assistance ( A ) and extended conjugation through a benzene-ring-generating indol-2-one intermediate ( B ) (Scheme ).…”