Alkylidene-indolinone

The stereocontroiied total synthesis of (+)-gelsemine was accomplished by T. Fukuyama and co-workers using the Knoevenagel condensation to prepare a precursor for the key divinylcyclopropane-cycloheptadiene rearrangement. The use of 4-iodooxindole as the active methylene component allowed the preparation of the (Z)-alkylidene indolinone product as a single stereoisomer. 

Scheme 20.28 Chiral phosphine-catalyzed [3+2] cyclization of alkylidene-indolinone.

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