Synthesis of chiral aminophosphines from chiral aminoalcohols via cyclic sulfamidates.

Protic aminophosphines with multiple chiral centers were synthesized in good yields and high purity by the nucleophilic ring-opening of N-protected cyclic sulfamidates with metal phosphides, followed by hydrolysis and deprotection. This synthetic approach is clean, scalable, and high yielding. The method provides an efficient alternative route for the synthesis of chiral aminophosphines.

Aminophosphine ligands R(2)P(CH(2))(n)NH(2) and ruthenium hydrogenation catalysts RuCl(2)(R(2)P(CH(2))(n)NH(2))(2).

The aminophosphine ligands R(2)P(CH(2))(2)NH(2) and R(2)P(CH(2))(3)NH(2) (R = Ph, (i)Pr, (t)Bu) were isolated in good to excellent yields from the reaction of LiPR(2) with Cl(CH(2))(2)N(TMS)(2) and Cl(CH(2))(3)N(TMS)(2), respectively, followed by hydrolysis. This approach allows fine tuning of the ligands' stereoelectronic properties through the variation of the substituents on the phosphine. The aminophosphine ligands were used to prepare the ruthenium complexes RuCl(2)(R(2)P(CH(2))(2)NH(2))(2) and RuCl(2)(R(2)P(CH(2))(3)NH(2))(2) by reacting a 2:1 mixture of the respective ligand and [RuCl(2)(cod)](n) in an appropriate solvent. The resulting complexes were found to be excellent catalysts for the hydrogenation of ketones and imines.

Highly active iridium catalysts for the hydrogenation of ketones and aldehydes.

The pressure hydrogenation capabilities of the iridium pincer complexes IrH2Cl[((i)Pr2PC2H4)2NH] (1) and IrH3[((i)Pr2PC2H4)2NH] (2) are described and compared to related results obtained previously in transfer hydrogenation. Complex 1 was shown to act as a convenient air-stable entry point to the active catalyst 2, in the presence of base and hydrogen gas. The catalysts are active in a range of solvents, including CH2Cl2 and CHCl3, in contrast to related ruthenium systems. This class of iridium complexes is very effective for the direct hydrogenation of a wide range of carbonyl compounds including ketones, diketones, alpha,beta-unsaturated ketones and aldehydes. A catalytic cycle is proposed for this system which involves an ionic heterolytic bifunctional hydrogenation mechanism.

A new class of versatile chiral-bridged atropisomeric diphosphine ligands: remarkably efficient ligand syntheses and their applications in highly enantioselective hydrogenation reactions.

A series of chiral diphosphine ligands denoted as PQ-Phos was prepared by atropdiastereoselective Ullmann coupling and ring-closure reactions. The Ullmann coupling reaction of the biaryl diphosphine dioxides is featured by highly efficient central-to-axial chirality transfer with diastereomeric excess >99%. This substrate-directed diastereomeric biaryl coupling reaction is unprecedented for the preparation of chiral diphosphine dioxides, and our method precludes the tedious resolution procedures usually required for preparing enantiomerically pure diphosphine ligands. The effect of chiral recognition was also revealed in a relevant asymmetric ring-closure reaction. The chiral tether bridging the two aryl units creates a conformationally rigid scaffold essential for enantiofacial differentiation; fine-tuning of the ligand scaffold (e.g., dihedral angles) can be achieved by varying the chain length of the chiral tether. The enantiomerically pure Ru- and Ir-PQ-Phos complexes have been prepared and applied to the catalytic enantioselective hydrogenations of alpha- and beta-ketoesters (C=O bond reduction), 2-(6'-methoxy-2'-naphthyl)propenoic acid, alkyl-substituted beta-dehydroamino acids (C=C bond reduction), and N-heteroaromatic compounds (C=N bond reduction). An excellent level of enantioselection (up to 99.9% ee) has been attained for the catalytic reactions. In addition, the significant ligand dihedral angle effects on the Ir-catalyzed asymmetric hydrogenation of N-heteroaromatic compounds were also revealed.

A modular design of ruthenium catalysts with diamine and BINOL-derived phosphinite ligands that are enantiomerically-matched for the effective asymmetric transfer hydrogenation of simple ketones.

A method is reported for making a potentially very wide series of ruthenium hydrido chloro complexes with diamine and readily-prepared diphosphinite ligand modules as precatalysts for the asymmetric transfer hydrogenation of simple ketones to give chiral alcohols in good yield and enantioselectivity.

Applications of ruthenium hydride borohydride complexes containing phosphinite and diamine ligands to asymmetric catalytic reactions.

[reaction: see text] A series of novel trans-ruthenium hydride borohydride complexes with chiral phosphinite and diamine ligands were synthesized. They can be used in the asymmetric transfer hydrogenation of aryl ketones, including base-sensitive ones, to give chiral alcohols in moderate to good enantioselectivities (up to 94% ee). They are also efficient catalysts for the Michael addition of malonates to enones with enantioselectivities of up to 90%. This kind of catalyst allows a one-pot tandem Michael addition/H(2) hydrogenation protocol to build structures with multiple chiral centers.

Enantioselective tandem michael addition/H2-hydrogenation catalyzed by ruthenium hydride borohydride complexes containing beta-aminophosphine ligands.

A variety of ruthenium(II) catalyst precursors containing beta-aminophosphine ligands and a borohydride ligand were found to be active for a one-pot, tandem asymmetric Michael addition/H2-hydrogenation reaction to give the chiral alcohol in excellent diastereomeric excess. The most effective catalyst is 4b, containing the (S)-binap ligand and (R,R)-Pnor ligand, derived from (1S,2R)-norephedrine.

Remarkably diastereoselective synthesis of a chiral biphenyl diphosphine ligand and its application in asymmetric hydrogenation.

Essentially complete atropdiastereoselectivity was realized in the preparation of biaryl diphosphine dioxide by asymmetric intramolecular Ullmann coupling and oxidative coupling with central-to-axial chirality transfer. A bridged C(2)-symmetric biphenyl phosphine ligand possessing additional chiral centers on the linking unit of the biphenyl groups was synthesized. No resolution step was required for the preparation of the enantiomerically pure chiral ligand. These findings offer a general and practical tool for the development of previously uninvestigated atropdiastereomeric biaryl phosphine ligands. The diphosphine ligand was found to be highly effective in the asymmetric hydrogenation of alpha- and beta-ketoesters, 2-(6'-methoxy-2'-naphthyl)propenoic acid, beta-(acylamino)acrylates, and enol acetates.

Identifying parameter by identical synchronization between different systems.

In this paper, parameters of a given (chaotic) dynamical system are estimated from time series by using identical synchronization between two different systems. This technique is based on the invariance principle of differential equations, i.e., a dynamical Lyapunov function involving synchronization error and the estimation error of parameters. The control used in this synchronization consists of feedback and adaptive control loop associated with the update law of estimation parameters. Our estimation process indicates that one may identify dynamically all unknown parameters of a given (chaotic) system as long as time series of the system are available. Lorenz and Rossler systems are used to illustrate the validity of this technique. The corresponding numerical results and analysis on the effect of noise are also given.

Ru-catalyzed highly enantioselective hydrogenation of beta-alkyl-substituted beta-(acylamino)acrylates.

Highly enantioselective hydrogenation of beta-alkyl-substituted (E)-beta-(acylamino)-acrylates catalyzed by Ru((R)-Xyl-P-Phos)(C(6)H(6))Cl(2) complex (cat. 1c) was achieved in up to 99.7% ee. Moderate to good enantioselectivities in the hydrogenation of corresponding (Z)-isomers in the presence of [Rh((R)-Xyl-P-Phos)(COD)]BF(4) (cat. 2c) were also obtained. The results demonstrated that the electronic and steric properties of the dipyridylphosphine ligands as well as the different transition metal ions have significant influences on the catalytic properties in the hydrogenation of beta-(acylamino)acrylates.

Air-stable catalysts for highly efficient and enantioselective hydrogenation of aromatic ketones.

A series of chiral trans-[RuCl(2)(dipyridylphosphine)(1,2-diamine)] complexes have been synthesized and characterized by NMR and single-crystal X-ray diffraction studies. These Ru complexes combined with (CH(3))(3)COK in 2-propanol formed a very effective catalyst system for the hydrogenation of a diverse range of simple aromatic ketones with high activity (substrate-to-catalyst ratio up to 100 000) and excellent enantioselectivity (up to >99.9%). The catalyst system was also found to be stable in solution even under a normal atmosphere.