1-Naphthylimine

Asymmetric aromatic alkylation binaphthyls. The reaction of 1-naphthyllithium with a naphthylimine (2) catalyzed by 1 provides 3, which is hydrolyzed (H20, CFjCOOH, Na2S04), with recovery of 1, to the aldehyde 4 in 85% ec. The stereochemistry can be improved by use of a bulky R group in 2. 

Recently, the use of a chiral catalysts in the asymmetric biaryl synthesis has received some attention. Unsymmetrical chiral binaphthyls can be obtained in high enantiomeric excess by SnAt reactions of naphthylimines such as 39 with lithium bromide free 1-naphthyllithium catalysed by a chiral ether ligand 40 (ref. 29). Another example is the Ni(0) catalysed cross coupling of naphthyl Grignard reagents and naphthyl bromides in the presence of a chiral ferrocene ligand (ref. 30). 

Stermitz and co-workers (79JOC293), in attempting to overcome the reduced yields associated with the 8,9-substituted compounds, failed to synthesize O-methylfagaronine (5) when using electrochemical techniques to cyclize the bromoamine, yet achieved a 50% yield of the 4-trifluoroacetyl analogue 125 when the naphthylimine 124 was oxidized with VOF3 in trifluoroacetic anhydride (Scheme 17). 

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