Asymmetric hydrogenation of activated keto compounds catalyzed by new chiral peralkyl-ampp rhodium complexes

Readily available peralkyl aminophosphinephosphinite ligands (alkyl-AMPP) give neutral rhodium complexes active for the catalytic reduction of some activated ketones under atmospheric hydrogen pressure at ambient temperature (ee = 80 %).     

Asymmetric hydrogenation using chiral phosphinite rhodium complexes

The Cu(I) complex of (1R,3R)-bis(diphenylphosphinoxy)-1,3-diphenylpropane (BDPODP) has been prepared and used for the transfer of the ligand to Rh(I). The Rh(I) complexes of this new phosphinite obtained by this method act as efficient asymmetric homogeneous hydrogenation catalysts for (Z)-α-(acylamino)-cinnamic acids.     

Asymmetric transfer hydrogenation of ketones catalyzed by rhodium and iridium complexes with chiral bidentate Schiff's bases

Rhodium and iridium complexes of Schiff's bases derived from (1R,2R)- and (1S,2S)-diaminocyclohexane catalyze asymmetric transfer hydrogenation of alkyl aryl ketones in PrⁱOH at room temperature to give chiral secondary alcohols (up to 65% ee).     

Asymmetric transfer hydrogenation of ketones catalyzed by chiral phosphineiridium complexes

The complexes formed in situ from Ir(COD)acac and chiral menthylphenylphosphines proved to be active catalysts in the hydrogen transfer reaction from isopropanol to prochiral ketones. When acetophenone was used, optical yields of up to 42% were achieved, the configuration of the carbinols being dependent on the bulkiness of the phosphine employed. Concerning the reaction rate, the activation process and the P/Ir ratio, the two menthyl-substituted phenylphosphines display different behaviour.     

Asymmetric hydrogenation by chiral aminophosphine-phosphinite rhodium compexes

The ligands (S)-$\text{N}$-(diphenylphosphino)-2-diphenylphosphinoxymethylpyrrolidine, (S)-prolophos, and (S)-1-diphenylphosphinoxy-2-$\text{N}$-diphenylphosphinoaminobutane, (S)-butaphos, have been prepared. The Rh(I) complexes of these phosphines act as efficient homogenous hydrogenation catalysts at ambient temperature and pressure for A-N-acetaminoacrylic acid and itaconic acid.     

Asymmetric hydrogenation of 2-substituted N-protected-indoles catalyzed by rhodium complexes of BINOL-derived phosphoramidites

The rhodium-catalyzed asymmetric hydrogenation of 2-substituted N-protected-indoles using monodentate phosphoramidites as ligands was examined. Full conversion and 74% ee, were obtained with a catalyst based on PipPhos. The use of a catalytic amount of base is necessary for activity; best results were obtained with Cs₂CO₃.     

Synthesis of a protected monodehydro Leu-enkephalin and its hydrogenation catalyzed by chiral rhodium complexes

(S,S)-Z-(0)Ts-Tyr-Gly₂-ΔPhe-Leu-OMe was synthesized. Some chiral rhodium complexes catalyze the reduction of the CC bond. The stereochemistry of reduction of the ΔPhe moiety was investigated, 93 % de could be achieved with dipamp as ligand in the catalyst.     

Enantioselective hydrogenation catalyzed by highly active rhodium complexes of chiral phosphites with atropisomeric moieties

Excellent ee's and extremely high activities are obtained in the rhodium-catalyzed hydrogenation of dimethyl itaconate using simple and readily available H₈-BINOL based monodentate phosphites. The hydrogenation proceeds efficiently even at a substrate concentration of 5.263 mol L⁻¹ and at a substrate to catalyst ratio (S/C) of 40,000 to give the product in 95.1% yield with up to 96.9% ee.     

手性钛配合物催化不对称反应研究

手性钛配合物是一类很有用的手性催化剂,在许多反应中显示出了良好的催化活性和高的对映选择性。在我们研究的系列反应中,发现手性钛配合物是一类优良的手性催化剂,其中不对称催化杂Diels-Alder反应制备二氢吡喃酮(99%ee),不对称催化硫醚氧化成亚砜反应(96%ee)和不对称催化硅腈化反应(87%ee),都获得了好的催化活性和高的对映选择性。我们对以上反应中其催化剂的用量、溶剂、催化剂浓度和抗衡离子的Lewis酸碱性、底物的结构与对映选择性的关系、催化循环机理等进行了较系统、深入的研究,发现非共价相互作用和分子识别现象在不对称催化反应中显示出重要的作用,为进一步设计新的手性催化剂,发展不对称催化反应提供了基础数据。     

Asymmetric hydrogenation on chiral cobalt complexes

Conclusions We were the first to effect the enantioselective hydrogenation of a mixture of isomeric 2-phenylbutenes on chiral cobalt catalytic systems of the Ziegler-Natta type in an optical yield of 25%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2621–2622, November, 1981.     

Kinetics of homogeneous hydrogenation of cyclohexene catalyzed by complexes of rhodium and iridium with a terdentate ligand

Complexes of the composition MC1HN (CH₂CH₂AsPh₂)₂ (M= =Rh(I), Ir(I) were used as catalysts for the homogeneous hydrogenation of cyclohexene over the temperature range 20–50 °C and 0.4 to 1 atm hydrogen partial pressure. The dependence of rate of hydrogenation on temperature, hydrogen concentration, catalyst concentration and substrate concentration is reported. The activation parameters of the reaction, H* and S* have been evaluated.

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MC1HN (CH₂CH₂AsPh₂)₂ (M=Rh(I) Ir(I) 20–50°C 0,4 1 atm. , , . H^* S^*.

     

Asymmetric hydrogenation of tryptophan precursors catalyzed by rhodium-DIOP complexes

Z-2-benzamido(acetamido)-3-(3-indolyl)-2-propenoic acids were hydrogenated with neutral and cationic rhodium(I) complexes containing the chiral diphosphine (–) or (+)–2,3-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)-butane [(–) or (+)–DIOP].

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Z-2- ()-3-(3-)-2- () (I), (–) (+)-2,3--2,3--1,4- ()-.

     

Enantioselective hydrogenation of indoles derivatives catalyzed by Walphos/rhodium complexes

The enantioselective hydrogenation of indole esters has been carried out efficiently in the presence of a rhodium catalyst modified by Walphos-type chiral ligands. The addition of a base can be beneficial in some catalytic conditions.     

Asymmetric 1,4-addition of alkenylzirconium reagents to α,β-unsaturated ketones catalyzed by chiral rhodium complexes

Highly enantioselective 1,4-addition of alkenylzirconocene chlorides to α,β-enones was found to be catalyzed by a chiral rhodium complex generated from [Rh(cod)(MeCN)₂]BF₄ and (S)-BINAP. The reaction can be applied to either cyclic or acyclic enones and the optical yield was up to 99% ee. The reaction mechanism would involve the transmetalation between the alkenylzirconocene chloride and the rhodium complex to give the alkenylrhodium species as a key intermediate.