Organocatalytic Enantioselective Synthesis of Chiral Spiro‐indoline‐pyrazolones through a formal [4+1] Annulation Reaction of 4‐Bromopyrazolones and aza‐ortho‐Quinone Methides

2024/03/06 by Laura Carceller‐Ferrer, Carlos Rodríguez‐Arias, Marc Montesinos‐Magraner +6
Chemistry · #Synthesis of Indole Derivatives #Axial and Atropisomeric Chirality Synthesis #Asymmetric Synthesis and Catalysis

paper · doi:10.1002/hlca.202400029

Abstract

Abstract In this communication, a straighforward asymmetric synthesis of spiro‐indoline‐pyrazolone compounds is described. This methodology consists in a formal [4+1] cycloaddition reaction of 4‐bromopyrazolones and aza‐ ortho ‐quinone methides generated in situ catalyzed by a bisquinine‐derived squaramide in CHCl 3 under basic conditions. A variety of chiral spirocyclic compounds bearing a pyrazolone and an indoline moieties were obtained in moderate to good yields (up to 68 %) and moderate to excellent enantioselectivities (up to 93 % ee).

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