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Enantioselective Intramolecular α-Arylation of Benzylamine Derivatives: Synthesis of a Precursor to Levocetirizine

Rakesh K. Saunthwal, M. Schwarz, Rajendra K. Mallick, William Terry-Wright, J. Clayden

Angewandte Chemie, 2023

14 citations

Abstract

A practical, transition metal-free method allows the enantioselective synthesis of α,α-diarylmethylamines by asymmetric α-arylation of benzylamines. Enantioselective lithiation of N'-aryl-N-benzyl-N-isopropyl ureas using a chiral lithium amide base generates a benzyllithium that undergoes an unactivated stereospecific intramolecular nucleophilic aromatic substitution to generate an α,α-diarylmethylamine in the form of its urea derivative, in up to >99% ee. Treatment with acid induces an 'azatropic shift' with retention of configuration, the product of which may be hydrolysed to the target amine.

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