Asymmetric Phase-Transfer Reactions of Oxindoles

The phase-transfer-catalyzed alkylation strategy was successfully appHed to the asymmetric cyanomethylation of oxindole 92 by the use of catalyst Hi [123]. This reaction allowed a simple and stereoselective synthesis of (—)-esermethole, a precursor to the clinically useful anticholinesterase agent (—)-physostigmine 

In the presence of chiral phosphonium salt 61 and potassium benzoate, the Michael addition reactions between 3-arylindoles 93 and alkylvinyl ketones worked very well with outstanding enantioselectivity [95], whereas chiral bifunctional ammonium bromide (S)-43a delivered high diastereo- and enantioselectivity for the 

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