Conjugate Addition with Intramolecular Nucleophilic Capture

8 Conjugate Addition with Intramolecular Nucleophilic Capture 

As with other electrophilic substitutions, conjugate addition can be used in conjunction with nucleophilic capture of an indolenine intermediate. Marko and coworkers used such a reaction to synthesize a versatile intermediate in alkaloid synthesis [298]. The amide 106-A cyclized to 106-B, when exposed to Si02 in CH2CI2. The nucleophilic addition was then conducted in a separate step. The 

Iminium ion catalysts have been used to achieve enantioselective alkylation combined with cycUzation. Protected tryptamines react with acrolein under the influence of catalysts 1A7-C [299], Various acroleins with electron-withdrawing substituents at C-3 are also reactive. 

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