1351376-57-2Relevant academic research and scientific papers
New P-chirogenic tert.-butyl-xantphos ligands and their application in asymmetric hydrogenation and alkylation
B?rner, Armin,Gandelman, Mark,Holz, Jens,Spannenberg, Anke,Wenzel, Gudrun
, (2020/03/25)
The synthesis of a broad library of new P-chirogenic Xantphos ligands is reported. A special feature is 2,7-di-tert.-butyl substituents in the backbone which requires the modification of the original synthetic approach. In comparison to related ligands reported formerly the substitution has a considerable influence on the results (yield and % e.e.) of metal catalyzed reactions, e.g. asymmetric rhodium catalyzed hydrogenation of isophorone and the palladium catalyzed alkylation, respectively.
P-Chirogenic Xantphos Ligands and Related Ether Diphosphines: Synthesis and Application in Rhodium-Catalyzed Asymmetric Hydrogenation
Holz, Jens,Rumpel, Katharina,Spannenberg, Anke,Paciello, Rocco,Jiao, Haijun,B?rner, Armin
, p. 6162 - 6169 (2017/09/15)
A series of P-chirogenic Xantphos ligands and related diaryl ether diphosphines have been synthesized by a modification of the well-established Jugé method. The approach consists of the in situ deboranation of the chiral ephedrine-based phosphinite before the P-C coupling takes place. The stereochemical integrity of the stereocenters of the diphosphines during synthesis, long-time storage, and catalytic application was evaluated. In the rhodium-catalyzed asymmetric hydrogenation of isophorone as a model substrate for industrially relevant prostereogenic enones with some of the diphosphines, almost complete conversion, high chemoselectivity, and 96% ee were achieved.
Neutral p-cymene ruthenium complexes with P-stereogenic monophosphines. New catalytic precursors in enantioselective transfer hydrogenation and cyclopropanation
Grabulosa, Arnald,Mannu, Alberto,Mezzetti, Antonio,Muller, Guillermo
experimental part, p. 4221 - 4228 (2012/01/13)
A family of eight neutral, pseudotetrahedral piano-stool ruthenium complexes C, of the type [RuCl2(p-cymene)(PArPhR)] (Ar = 1-naphthyl, 9-phenanthryl and 2-biphenylyl; R = Me, i-Pr, OMe, -CH2SiMe 3 and -CH2SiPh3) have been prepared and characterised, including the X-ray crystal structure for C6 (Ar = 2-biphenylyl; R = i-Pr). These complexes catalyse the asymmetric hydrogen transfer reaction of acetophenone in refluxing 2-propanol in the presence of potassium tert-butoxyde, reaching full conversions and up to 45% ee after 24 h towards the S enantiomer of 1-phenylethanol. Cationic complexes formed upon treatment of C with one equivalent of AgSbF6 or (Et3O)PF6 are active in the cyclopropanation reaction of styrene and α-methylstyrene by ethyl diazoacetate. Low to moderate conversions (up to 58%), diastereoselectivities (up to 40% de), and moderate enantioselectivities (up to 69% ee) have been found. For both reactions, bulky complexes and C6 in particular lead to the best results.
