A chiral N-heterocyclic carbene (NHC)-catalyzed [3 + 3] cycloaddition reaction of imines and oxindole-derived enals was developed for rapid access to spirocylic oxindoles. In most cases, the desired spirocylic oxindole products were obtained in high yields and excellent enantioselectivities with less than 1 h of reaction time.

A chiral cooperative catalysis of NHC and Brønsted acid for a formal [4+2] reaction of unprotected isatins and enals was developed for the direct synthesis of unprotected spiro[indoline-3,2'-pyran]-2,6'(3'H)-diones in good to excellent yields (up to 95%) with high enantioselectivities (up to >93% ee).

Cooperative Catalysis of N-Heterocyclic Carbene and Broensted Acid for a Highly Enantioselective Route to Unprotected Spiro-indoline-pyrans. -(LIN, Y.; YANG*, L.; DENG, Y.; ZHONG, G.; Chem. Commun. (Cambridge) 51 (2015) 39, 8330-8333, http://dx.doi.org/10.1039/C5CC02096D ; Coll. Mater., Chem. Chem. Eng, Hangzhou Norm. Univ., Hangzhou 310036, Peop. Rep. China; Eng.) -M. Tismer 39-132

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