194149-25-2Relevant articles and documents
Enantioselective hydrogenation of α-dehydroamino acid esters catalyzed by rhodium complexes with chiral bisaminophosphine ligands
Sun, Xianfeng,Li, Wei,Zhou, Le,Zhang, Xumu
supporting information; experimental part, p. 1150 - 1154 (2010/06/20)
A highly efficient strategy for the synthesis of a series of chiral bisaminophosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for rhodium-catalyzed asymmetric hydrogenations of α-d
1,4-BIS-DIPHOSPHINES, 1,4-BIS-DIPHOSPHITES AND 1,4-BIS- DIPHOSPHONITES FROM OPTICALLY ACTIVE (Z)-OLEFINES AS CHIRAL LIGANDS
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Page/Page column 21; 23, (2008/06/13)
Chiral diphosphines, diphosphinites, diphosphites and diphosphonites derived from (Z)-2-butenes suitable to act as chiral ligands, complexes between said diphosphines, diphosphinites, diphosphites and diphosphonites and transition metals, and their utilization as chiral catalysts in stereocontrolled reactions, such as diastereo- and enantioselective reduction reactions, diastereo- and enantioselective hydroformylation reactions, diastereo- and enantioselective hydro cyanation reactions. Process for the preparation of said chiral diphosphines, diphosphinites, diphosphites and diphosphonites and process for the preparation of said complexes and for their utilization in stereocontrolled reactions.
Chiral diphosphorus compounds and their transition metal complexes
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Page/Page column 14, (2010/02/11)
The present invention relates to chiral diphosphorus compounds and their transition metal complexes, to a process for preparing chiral diphosphorus compounds and their transition metal complexes and also to their use in asymmetric syntheses.
Stereospecific deoxygenation of phosphine oxides with retention of configuration using triphenylphosphine or triethyl phosphite as an oxygen acceptor
Wu, Hai-Chen,Yu, Jin-Quan,Spencer, Jonathan B.
, p. 4675 - 4678 (2007/10/03)
(Chemical Equation Presented) A new protocol for deoxygenation of various phosphine oxides with retention of configuration is described. The advantage of the new method includes milder conditions and considerably shortened reaction times. Mechanistic studies about the oxygen transfer between the starting phosphine oxide and the sacrificial triphenylphosphine are also presented.
Chiral diphosphorus compounds and transition metal complexes thereof
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Page 23-24, (2010/02/05)
Tetrahydrofuran bisphosphines of formula (I), are new. Tetrahydrofuran bisphosphines of formula (I): X1, X2 = bonds or O; R1, R2 = H, 1-20C alkyl, 1-20C fluoroalkyl, 2-20C alkenyl, 4-24C aryl, 5-25C aralkyl, 6-26C aralkenyl, NR7R8, OR8, AOR8, ANR7R8 or OC
Carbohydrate Phosphinites as Practical Ligands in Asymmetric Catalysis: Electronic Effects and Dependence of Backbone Chirality in Rh-Catalyzed Asymmetric Hydrogenations. Synthesis of R- or S-Amino Acids Using Natural Sugars as Ligand Precursors
RajanBabu,Ayers, Timothy A.,Halliday, Gary A.,You, Kimberly K.,Calabrese, Joseph C.
, p. 6012 - 6025 (2007/10/03)
Vicinal diarylphosphinites derived from carbohydrates are excellent ligands for the Rh(I)-catalyzed enantioselective asymmetric hydrogenation of dehydroamino acid derivatives, producing the highest enantioselectivity of any ligands directly prepared from natural products. The enantioselectivity can be enhanced by the appropriate choice of substituents on the aromatic rings of the phosphinites. For example, the use of phosphinites with electron-donating bis(3,5-dimethylphenyl) groups on phosphorus provides ee's up to 99% for a wide range of amino acids including some with easily removable N-protecting groups. Electron-withdrawing aryl substituents, on the other hand, decrease the enantioselectivity. Sense of chiral induction in the amino acid product depends on the relative juxtaposition of the vicinal diphosphinites on a given sugar backbone. When readily available D-glucopyranosides are used as the starting sugars, 2,3-phosphinites give the S-amino acids and 3,4-phosphinites give the R-amino acids. In the case of aromatic and heteroaromatic amino acids, enantioselectivities > 95% are consistently obtained. Practical considerations such as the ease of ligand synthesis, rates of reactions, catalyst turnover, and scope and limitations in terms of substrates are discussed. A possible explanation for the enhancement of enantioselectivity by electron-rich phosphinites is offered.
Ligand Electronic Effects in Asymmetric Catalysis: Enhanced Enantioselectivity in the Asymmetric Hydrocyanation of Vinylarenes
Casalnuovo, Albert L.,RajanBabu, T. V.,Ayers, Timothy A.,Warren, Timothy H.
, p. 9869 - 9882 (2007/10/02)
The enantioselectivity of the nickel-catalyzed, asymmetric hydrocyanation of vinylarenes using glucosederived, chiral phosphinite ligands, L, increases dramatically when the ligands contain electron-withdrawing P-aryl substituents.The substrate and solvent also strongly influence the enantioselectivity, with the highest ee's (85-91percent for 6-methoxy-2-vinylnaphthalene (MVN)) obtained for the hydrocyanation of electron-rich vinylarenes in a nonpolar solvent such as hexane.Mechanistic studies suggest the catalytic cycle consists of an initial HCN oxidative addition or vinylarene coordination to "NiL", followed by insertion to form an (η3-benzyl)nickel cyanide complex, and irreversible reductive elimination of the nitrile.A kinetic analysis of the NiLa(COD) (La, P-aryl=3,5-(CF3)2C6H3) catalyzed hydrocyanation of MVN indicates that as the HCN concentration is increased the catalyst resting state shifts from NiLa(COD) to a complex containing both MVN and HCN, presumably the (η3-benzyl)nickel cyanide intermediate NiLa(η3-CH3CHC10H6OCH3)CN.A 31P NMR analysis of the intermediate NiLa(MVN) shows little ground state differentiation of the MVN enantiofaces and suggests that the enantioselectivity is determined later in the mechanism.Deuterium labeling studies suggest that electron-withdrawing P-aryl substituents increase the rate of reductive elimination of the product nitrile from the (η3-benzyl)nickel cyanide intermediate and, on this basis, a rationale for the ligand electronic effect is proposed.
