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MaxPHOS Ligand: PH/NH Tautomerism and Rhodium‐ Catalyzed Asymmetric Hydrogenations
Author(s) -
CristóbalLecina Edgar,
Etayo Pablo,
Doran Séan,
Revés Marc,
MartínGago Pablo,
Grabulosa Arnald,
Costantino Andrea R.,
VidalFerran Anton,
Riera Antoni,
Verdaguer Xavier
Publication year - 2014
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201300662
Subject(s) - chemistry , rhodium , protonation , tautomer , ligand (biochemistry) , stereocenter , catalysis , salt (chemistry) , medicinal chemistry , stereochemistry , photochemistry , organic chemistry , enantioselective synthesis , ion , biochemistry , receptor
MaxPHOS is an active and robust P‐stereogenic ligand for asymmetric catalysis. The presence of an NH bridge between the two phosphine moieties allows the NH/PH tautomerism to take place. The neutral ligand, in which the NH form predominates, is an air‐sensitive compound. However, protonation of MaxPHOS leads to the stable PH form of the ligand, in which the overall positive charge is distributed on both P centers. This protonation turns the MaxPHOS⋅HBF 4 salt 3 into an air‐stable compound both in the solid state and in solution. The salt 3 is also a convenient precursor for the preparation of rhodium(I) complexes by direct ligand exchange with the complex [Rh(acac)(cod)]. Finally, the corresponding rhodium(I)‐MaxPHOS complex was tested in the asymmetric hydrogenation of a wide range of substrates. The complex proved to be a highly selective and robust system in these reactions.