Imines sparteine-mediated addition

Scheme 12 (-)-Sparteine-mediated addition of a-amino organometallic reagents to imines...

Several further publications report on the (—)-sparteine-mediated addition of alkyl-or aryllithium onto imines or the C=N bond of isoquinolines . Usually, the achieved enantiomeric excesses are low and, sometimes, other chiral ligands serve better. As reported by Muller and coworkers, the nucleophilic substitution of arenecarbaldehyde dialkyl acetals by o-substituted aryllithium reagents is an alternative . 

Lateral Lithiation. An enantioselective synthesis of tetrahydroisoquinolin-l-ones via a BuLi/(—)-sparteine-mediated lateral metalation-imine addition sequence proceeds with highest yields and induction in toluene/ether mixtures (eq 46). ... 

The ligand 108 has activity as an external controller of stereochemistry in the enantioselective addition of methyllithiiun to imines derived from veratralde-hyde with up to 41% ee [87]. (-)-Sparteine (19)-mediated reaction of organo-hthium reagents afforded isoquinoUne alkaloid 107 directly from 3,4-dihydroi-soquinoline 106 with up to 47% ee (Scheme 32) [88]. 

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