Stereoselective synthesis of 3-spiro-α-methylene-γ-butyrolactone oxindoles from Morita–Baylis–Hillman adducts of isatin
作者:Ponnusamy Shanmugam、Vadivel Vaithiyanathan
DOI:10.1016/j.tet.2008.02.002
日期:2008.4
concise stereoselective synthesis of 3-spiro-α-methylene-γ-butyrolactone oxindoles from Morita–Baylis–Hillmanadducts of isatin in excellent yield has been achieved following a three-step reaction sequences viz. (1) Isomerisation of the Morita–Baylis–Hillmanadducts of isatin with trimethyl orthoformate and montmorillonite K10 clay catalyst, (2) a second Morita–Baylis–Hillman reaction with formaldehyde
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