Carbon-SO3H: a novel and recyclable solid acid catalyst for the synthesis of spiro[4H-pyran-3,3′oxindoles]

A bioglycerol derived carbon-sulfonic acid is found to catalyze efficiently the three-component one-pot condensation of isatin, malononitrile, and 1,3-dicarbonyls to afford a wide range of spirop[4H-pyran-3,3'-oxindole]derivatives in good yields and selectivity. The use of a recyclable solid acid catalyst makes this method simple, convenient, and cost-effective. (C) 2013 Elsevier Ltd. All rights reserved.