95456-31-8Relevant articles and documents
Enantioselective hydrogenation of itaconate using rhodium bihelicenol phosphite complex. Matched/mismatched phenomena between helical and axial chirality
Nakano, Daisuke,Yamaguchi, Masahiko
, p. 4969 - 4971 (2003)
Phosphites prepared from bihelicenol, menthol (or 1-phenylethanol), and PCl3 are effective ligands for the rhodium-catalyzed enantioselective hydrogenation of dimethyl itaconate. Stereochemistry of the helicene moiety plays an important role in
Bulky, optically active P-stereogenic phosphine-boranes from pure H-menthylphosphinates
Gatineau, David,Giordano, Laurent,Buono, Gerard
supporting information; experimental part, p. 10728 - 10731 (2011/09/14)
The transformation of readily available pure-H-menthylphosphinates into chiral phosphinous acid-boranes permits the elaboration of bulky P-stereogenic secondary phosphine-boranes. Taking advantage of the synthetic potential of these compounds, a broad range of hindered P-chiral tertiary phosphine-boranes has been prepared with excellent enantiomeric excesses. The utility of bulky o-tolylphosphines was illustrated by the synthesis of a rare enantiopure phosphapalladacycle (SP,SP)-12.
Rh-catalyzed enantioselective conjugate addition of arylboronic acids with a dynamic library of chiral tropos phosphorus ligands
Monti, Chiara,Gennari, Cesare,Piarulli, Umberto
, p. 1547 - 1558 (2008/02/03)
A library of 19 chiral tropos phosphorus ligands, based on a free-to-rotate (tropos) biphenol unit and a chiral P-bonded alcohol (11 phosphites, 1-P(O)2O to 11-P(O)2O) or secondary amine (8 phosphoramidites, 12-P(O)2N to 19-P(O)2N). were screened, individually and in combinations of two, in the rhodium-catalyzed asymmetric conjugate addition of arylboronic acids to enones and enoates. High enantioselectivities (up to 99% ee) and excellent yields were obtained in the addition to either cyclic or acyclic substrates. The flexible biphenolic P ligands outperformed the analogous rigid binaphtholic P ligands. Variable-temperature 31P NMR studies revealed that the biphenolic ligands are tropos even at low temperature. Only below 190 K was a coalescence observed: upon further cooling, two atropisomers were detected. The Rh homocomplexes ([Rh(La)2]+) were also studied: in general, a single doublet (P-Rh coupling) was observed in the case of the biphenolic phosphite ligands, over the temperature range 380-230 K, demonstrating their tropos nature in the rhodium complexes even at low temperatures. On the other hand, the phosphoramidites showed different behaviors depending on the structure of the ligand and on the nature of the rhodium source. The spectrum at 230 K of the mixture of [Rh(acac)(eth)2] (eth = C2H4) with phosphite 6-P(O)2O and phosphoramidite 19-P(O)2N (the most enantioselective ligand combination in the conjugate addition reaction) revealed the presence of four homocomplexes (total approximately 40%: [Rh(6-P(O)2}2], [Rh{(aR)-19-P(O)2N}2], [Rh((aS)-19-P(O)2N) 2], [Rh((aR)-19-P(O)2N}((aS)-19-P(O)2N}]) and one heterocomplex, [Rh{6-P(O)2O){(aR)-19-P(O)2NJ] (approximately 60%) In the heterocomplex, the biphenol-derived phosphite is free to rotate (tropos) while the biphenol-derived phosphoramidite shows a temperature-dependent tropos/atropos behavior (coalescence temperature = 310 K).
Enantioselective conjugate addition of phenylboronic acid to enones catalysed by a chiral tropos/atropos rhodium complex at the coalescence temperature
Monti, Chiara,Gennari, Cesare,Piarulli, Umberto
, p. 5281 - 5283 (2007/10/03)
A highly enantioselective rhodium-catalysed conjugate addition of phenylboronic acid to cyclic enones has been achieved using a dynamic library of chiral phosphorus ligands; the tropos/atropos nature of the ligands in the rhodium complex has been characterised via 31P-NMR. The Royal Society of Chemistry 2005.
