Diastereoselective Construction of Tetrahydro-Dispiro[indolinone-3,2′-pyran-5′,4″-pyrazolone] Scaffolds via an Oxa-Michael Cascade [4 + 2] Annulation Reaction
A straightforward metal-free oxa-Michael cascade [4 + 2] annulation reaction was established between isatin-derived Morita–Baylis–Hillman (Is-MBH) alcohols with alkylidene pyrazolones to accessstructuraldiverse tetrahydro-dispiro[indolinone-3,2′-pyran-5′,4″-pyrazolone] scaffolds bearing two tertiary and two quaternary stereocenters. The Is-MBH alcohol was utilized as an oxa-Michael donor for the