The Trityl Cation Embedded into a [7]Helicene-Like Backbone: Preparation and Application as a Lewis Acid Catalyst

Abstract

The synthesis of a helically chiral carbenium ion is reported. The new motif is essentially a trityl cation embedded into a [7]helicene-like framework. The key step in its preparation establishes the π-extended fluorenone system in one step by an unprecedented palladium-catalyzed carbonylative annulation of a 4,4′-biphenanthryl-3,3′-diyl precursor. The racemic form of the new carbon Lewis acid was found to catalyze a representative set of reactions typically promoted by the trityl cation.

Key words

carbenium ions - carbonylation - chirality - catalysis - Lewis acids - palladium

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