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5737753 
Journal Article 
Synthesis of the chiral diphosphine ligand 2,3-bis(diphenylphosphino)butane (CHIRAPHOS) 
Matteoli, U; Beghetto, V; Schiavon, C; Scrivanti, A; Menchi, G 
1997 
1 
Tetrahedron: Asymmetry
ISSN: 0957-4166 
8 
9 
1403-1409 
WOS:A1997WZ96400009 
A new synthesis of CHIRAPHOS starting from readily available 2,3-bis(diphenylphosphinyl)-1,3-butadiene has been devised. The key step of the synthesis is the hydrogenation of the diene to rac-2,3-bis(diphenylphosphinyl)butane. This reduction can be conveniently performed by treating 2,3-bis(diphenylphosphinyl)-1,3-butadiene with NaBH4 in THF/CH2Cl2 mixtures. The racemic diphosphine oxides are subsequently resolved using (2S,3S)-(+)- and (2R,3R)-(−)-2,3-O-dibenzoyltartaric acid [(+)- and (−)-DBTA]. Reduction of the resolved phosphine oxides is carried out using trichlorosilane.