New axially chiral atropos and tropos secondary diamines as ligands for enantioselective intramolecular hydroamination

The highly constrained, axially chiral atropos diamines (R',S,S)-1, (R',R,R)-1 and (R',S,R)-1 and their tropos analogue (R')-2 have been prepared via bis-N,N-dialkylation of (R)-2,2'-diamino-1,1'-binaphthyl, using either (R)- or (S)-2,2'-bis(bromomethyl)-1,1'-binaphthyl and 2,2'-bis(bromomethyl)-1,1'-biphenyl as alkylating agents, followed by selective nickel chloride-catalysed bis(monohydrogenolysis) of the tertiary amino groups of the so-obtained (R',R,R)-4, (R',S,S)4, (R',R,)-4 and (R')-6, respectively, by lithium aluminium hydride in refluxing THF or THF/diglyme. The diamines (R',S,S)-1, (R',R,R)-1, (R',S,R)-1 and (R')-2 have been evaluated as ligands for ytterbium-catalysed intramolecular hydroamination and compared to the ligand 1,1'-binaphthyl-2,2'-bis(benzylamine) (R')-3. They afforded highly active catalysts for the cyclisation of aminopentenes and ammohexenes with up to 58% ee. (c) 2007 Elsevier Ltd. All rights reserved.