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

• Published in: Tetrahedron: asymmetry 2008-01, Vol.19 (1), p.82-92
• Main Authors: Aillaud, Isabelle, Wright, Karen, Collin, Jacqueline, Schulz, Emmanuelle, Mazaleyrat, Jean-Paul
• Format: Article
• Language: English
• ISSN: 0957-4166; 1362-511X
• DOI: 10.1016/j.tetasy.2007.11.029

The highly constrained, axially chiral atropos diamines ( R i , S, S)- 1, ( R i , R, R)- 1 and ( R i , S, R)- 1 and their tropos analogue ( R i )- 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(mono-hydrogenolysis) of the tertiary amino groups of the so-obtained ( R i , R, R)- 4, ( R i , S, S)- 4, ( R i , R, S)- 4 and ( R i )- 6, respectively, by lithium aluminium hydride in refluxing THF or THF/diglyme. The diamines ( R i , S, S)- 1, ( R i , R, R)- 1, ( R i , S, R)- 1 and ( R i )- 2 have been evaluated as ligands for ytterbium-catalysed intramolecular hydroamination and compared to the ligand 1,1′-binaphthyl-2,2′-bis(benzylamine) ( R i )- 3. They afforded highly active catalysts for the cyclisation of aminopentenes and aminohexenes with up to 58% ee.