Both enantiomers of 2,3-bis(tert-butylmethylphosphino)quinoxaline (QuinoxP*), 1,2-bis(tert-butylmethylphosphino)benzene (BenzP*), and 1,2-bis(tert-butylmethylphosphino)-4,5-(methylenedioxy)benzene (DioxyBenzP*) were prepared in short steps from enantiopure (S)- (R)-tert-butylmethylphosphine-boranes as the key intermediates. All these ligands crystalline solids not readily oxidized on exposure to air. Their rhodium complexes exhibited excellent enantioselectivities high catalytic activities...

This account brings together the recent experimental and computational data on mechanism of Rh-catalyzed asymmetric hydrogenation activated double bonds. Two alternative reaction pathways (unsaturated dihydride) are compared. It is suggested that differences in these mechanisms not primarily important for stereoselection, since they join a single pathway before stereoselection occurs. approach was used to rationalize present discrepancies prediction sense enantioselection P-stereogenic...

The asymmetric hydrogenation of aryl- and alkyl-substituted enamides catalyzed by Rh-BisP complex affords optically active amides with very high ee values. Rh-MiniPHOS catalyst gives somewhat less satisfactory results. Hydrogenation the aryl-substituted (S,S)-BisP-Rh R-amides, whereas t-Bu- 1-adamantyl-substituted give S-products 99% ee. Reaction [Rh(BisP)(CD(3)OD)(2)]BF(4) (11) CH(2)=C(C(6)H(5))NHCOCH(3) (5) two diastereomers catalyst-substrate (12a,b), which interconvert reversibly both...

Abstract An efficient nickel‐catalyzed asymmetric hydrogenation of N ‐ t Bu sulfonyl imines was developed with excellent yields and enantioselectivities using ( R , )‐QuinoxP* as a chiral ligand. The use much lower catalyst loading (0.0095 mol %, S/C=10500) represents the highest catalytic activity for Ni‐catalyzed hydrogenations reported so far. Mechanistic studies suggest that coordination equilibrium exists between nickel salt its complex, excess promotes formation active Ni‐complex,...

The mechanism of the asymmetric hydrogenation exocyclic α,β-unsaturated carbonyl compounds with (aS)-Ir/iPr-BiphPhox catalyst was studied by NMR experiments and DFT computational analyses. Computed optical yields proceeding an iridium(I)/iridium(III) involving a transition state stabilized through two intramolecular hydrogen bonds are in good accordance experimental ee values.

An efficient cobalt-catalyzed asymmetric hydrogenation of C=N bonds has been realized. Chiral hydrazines were obtained in high yields and with excellent enantioselectivities (95-98 % ee). The went smoothly at up to 2000 substrate/catalyst on a gram scale. success this reaction relies the presence an NHBz group substrates, reactivity enantioselectivity improved by assisted coordination cobalt atom nonbonding interaction ligand. Furthermore, practical applications for synthesis several useful...

Abstract Chiral α-aryl glycines play a key role in the preparation of some bioactive products, however, their catalytic asymmetric synthesis is far from being satisfactory. Herein, we report an efficient nickel-catalyzed hydrogenation N -aryl imino esters, affording chiral high yields and enantioselectivities (up to 98% ee). The can be conducted on gram scale with substrate/catalyst ratio up 2000. obtained - p -methoxyphenyl glycine derivatives are not only directly useful secondary amino...

Earth-abundant nickel, coordinated with a suitable chiral bisphosphine ligand, was found to be an efficient catalyst for the asymmetric hydrogenation of 2-amidoacrylates, affording α-amino acid esters in quantitative yields and excellent enantioselectivity (up 96 % ee). The active component studied by NMR HRMS, which helped us realize high catalytic efficiency on gram scale low loading (S/C=2000). hydrogenated products could simply converted into acids, β-amino alcohols, their bioactive...

Asymmetric hydrogenation of sterically hindered substrates still constitutes a long-standing challenge in the area asymmetric catalysis. Herein, an efficient palladium acetate (an inexpensive Pd salt with low toxicity) catalyzed N-tosylimines is realized high catalytic activities (S/C up to 5000) and excellent enantioselectivities (ee 99.9%). Quantum chemical calculations suggest that uniformly are observed due structurally different S- R-reaction pathways.

The mechanism of asymmetric hydrogenation catalyzed by a new effective catalyst, viz., rhodium complex (S,S)-1,2-bis(tert-butylmethylphosphino)ethane (BisP*), has been studied multinuclear NMR. Hydrogenation the precatalyst [Rh(BisP*)(nbd)]BF4 (8) at −20 °C in deuteriomethanol affords solvate [Rh(BisP*)(CD3OD)2]BF4 (9), which is, turn, hydrogenated −90 producing equilibrium amounts (20% −95 °C) [RhH2(BisP*)(CD3OD)2] (10)the first observable dihydride Rh(I) with diphosphine ligand. Dihydride...

A new class of chiral C2-symmetric bis(trialkyl)phosphine ligands has been prepared and used in Rh(I)-catalyzed asymmetric hydrogenation reactions. The ligands, 1,2-bis(alkylmethylphosphino)ethanes 1a-g(abbreviated as BisP*, alkyl = t-butyl, 1-adamantyl, 1-methylcyclohexyl, 1,1-diethylpropyl, cyclopentyl, cyclohexyl, isopropyl) 1,2-bis(alkylmethylphosphino)methanes 2a-d(abbreviated MiniPHOS, isopropyl, phenyl) are by a simple synthetic approach based on the air-stable phosphine–boranes....

A conceptually novel approach for asymmetric intramolecular hydroamination, hydroalkoxylation and hydrocarbonation of alkynes using chiral palladium catalysts are described. The reactions the aminoalkynes 5, alkynols 7, alkynylmethines 9 in presence Pd2(dba)3·CHCl3/PhCOOH/renorphos 4 benzene (or benzene−hexane) at 100 °C gave corresponding cyclization products (nitrogen heterocycles 6, oxygen 8, carbocycles 10) good yields with enantioselectivities. origins enantioselectivities...

The rhodium complex of (R)-(tert-butylmethylphosphino)(di-tert-butylphosphino)methane used in Rh-catalyzed asymmetric hydrogenation representative substrates 3−14 demonstrated high catalytic activity coupled with wide scope and nearly perfect enantioselectivity. Mechanistic studies (NMR DFT computations) were carried out order to investigate the mechanism enantioselection (Z)-α-acetamidocinnamate (3). Although catalyst−substrate complexes 15a,b double bond coordinated near non-"chiral"...

This article describes recent developments in the understanding of mechanism enantioselection one most efficient artificial catalytic reactions--Rh-catalyzed asymmetric hydrogenation. Numerous experimental and computational data are consistent with idea that takes place through reversible coordination double bond octahedral dihydride complexes, which can happen only if resulting chelate cycle is formed less hindered quadrant. In its main features, this generating chirality resembles recently...

A highly efficient palladium-catalyzed asymmetric arylation of cyclic ketimine esters is developed, which provides the desired product in up to 99% yield with ee. The mechanism enantioselection studied using DFT calculation.

Chiral allylic amines are not only present in many bioactive compounds, but can also be readily transformed to other chiral amines. Therefore, the asymmetric synthesis of is highly desired. Herein, we report two types Ni(II)-catalyzed alkenylation cyclic ketimines for preparation When bear alkyl or alkoxycarbonyl groups, gives five- and six-membered α-tertiary amine products with excellent yields enantioselectivities under mild reaction conditions. A variety used method tolerates some...

An efficient copper-catalyzed reductive defluorination of β-trifluoromethylated enones via an oxidative homocoupling Grignard reagents is reported. The reaction proceeded smoothly with a wide range substrates, including the ones bearing aromatic heterocycles, such as furyl and thienyl ring systems in high yields (80–92%, except one example) under mild conditions. This provides practical method for synthesis gem-difluoroolefin ketones. It also worth noting that this process using "oxidizing...

Chiral α-substituted ethylphosphonate and ethylphosphine oxide compounds are widely used in drugs, pesticides, ligands. However, their catalytic asymmetric synthesis is still rare. Of the only hydrogenation methods available at present, all cases use rare metal catalysts. Herein, we report an efficient earth-abundant transition-metal nickel catalyzed affording corresponding chiral products with up to 99 % yield, 96 ee (enantiomeric excess) (99 ee, after recrystallization) 1000 S/C...

Excellent enantioselectivities up to 99.7% were achieved in the hydrogenation of (E)-β-(acylamino)acrylates by use Rh(I)-complexes electron-rich diphosphines, t-Bu-BisP* and t-Bu-MiniPHOS. Low-temperature NMR experiments testify that monohydrides with β-carbon atom substrate bound rhodium are involved catalytic cycle.

The PtBr2-catalyzed reaction of 1-ethynyl-2-(1-alkoxybut-3-enyl)benzenes at 120 degrees C in CH3CN gave functionalized indenes good to allowable yields. Most probably, the hydrogen terminal alkyne is transferred adjacent internal beta-carbon form an (eta2-vinylidene)platinum carbene intermediate, which activates sp3 C-H bond benzylic carbon. This pathway supported by DFT calculations suggest that formation Pt-vinylidene complex rate-limiting stage for whole transformation.

A general protocol for the synthesis of functionalized indenes from o-alkynylbenzaldehyde acetals and thioacetals has been elaborated. Acetals uniformly give cyclization products having alkyl group starting acetylene migrated to alpha-position, whereas corresponding proceeds without migration. Optimization catalytic system revealed an unknown activation effect: PtCl(2) was found be a better catalyst in presence olefins than without. similar (PtCl(2)/benzoquinone) appropriate cyclic acetals,...

Chiral complexes of [Pd(S,S-chiraphos)(PhCN)2](SbF6)2 (2b) and [Pd(S,S-dipamp)(PhCN)2](SbF6)2 (2c) catalyzed the highly enantioselective 1,4-additions Ar3Bi, [ArBF3]K, ArSiF3 to cyclic acyclic enones in aqueous methanol. The reactions Ar3Bi at 0−5 °C presence Cu(BF4)2 or ZnF2, whereas they smoothly prompted addition [ArBF3]K −15 without further activation catalysts. highest enantioselectivities giving β-aryl ketones up 99% ee were attained when using 2b for 2-cyclopentenone (E)-enones, 2c...

The bifunctional chiral amido Ir complex catalyzed asymmetric electrophilic direct amination of α-substituted α-cyanoacetates using azodicarboxylates proceeds rapidly to provide the corresponding hydrazine adducts in high yields and with excellent ee values.