α-Lithiated (R,R)-TMCDA as an efficient building block for the preparation of Chiral N,N,O ligands by asymmetric 1,2-addition

Abstract

The chiral diamine (1R,2R)-N,N,N′,N′-tetramethylcyclohexane-1, 2-diamine [(R,R)-TMCDA, 3] has been selectively deprotonated at one of its methyl groups by a series of alkyllithium bases. Although the enantiomerically pure compound formed a trimeric structure, direct lithiation of the racemic mixture of the amine (trans-TMCDA) yielded a tetrameric compound. With 2 equiv. of the deprotonation reagent a mixed aggregate of the lithiated amine and tert-butyllithium was formed. The lithiated amine was employed as a building block for the synthesis of novel nitrogen ligands. The asymmetric 1,2-addition of α-lithiated (R,R)-TMCDA onto different ketones and aldehydes yielded a series of novel N,N,O ligands with different substitution patterns. Depending on the carbonyl compound used, a new stereocentre and different substituents can be introduced. The coordination behaviour of these ligands is illustrated by the formation of metal salt complexes. (R,R)-TMCDA and its racemic mixture can be directly deprotonated at its methyl group. With 2 equiv. of the deprotonation reagent a mixed aggregate 8 of the lithiated amine 7 and tBuLi was formed. By addition of α-lithiated (R,R)-TMCDA onto carbonyl compounds a series of novel N,N,O ligands of type 4 with different substituents and a further stereocentre are accessible. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.