Synthesis 2009(19): 3339-3349  
DOI: 10.1055/s-0029-1217006
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Enantiomerically Pure Allenes with Central and Axial Chirality Mediated by a Remote Sulfinyl Group

José Luis García Ruano*, Vanesa Marcos, José Alemán*
Departamento de Química Orgánica (C-I), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
Fax: +34(914)973966; e-Mail: joseluis.garcia.ruano@uam.es; e-Mail: jose.aleman@uam.es;
Further Information

Publication History

Received 1 July 2009
Publication Date:
14 September 2009 (online)

Abstract

Enantiomerically pure 2-(p-tolylsulfinyl)benzylcopper reagents react with propargyl bromides and mesylates, affording enantiomerically pure allenes with central and axial chirality. Both regioselectivity (SN2′ processes) and configuration at the chiral axis are completely controlled by the sulfinyl group. The stereoselectivity at the benzylic position is very high. Complete kinetic resolution and moderate dynamic resolution of racemic propargylic mesylates can be achieved. This stereochemical behavior can be explained by assuming the stabilization of the benzylcopper by the sulfinyl oxygen and the association of the triple bond to the metal as a previous step of the intramolecular SN2′ nucleophilic attack.

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The copper between brackets, [Cu], indicates that the stoichiometric ligand/copper ratio is not known.