StePHOX, a new family of optically active, tunable phosphine-oxazoline ligands: syntheses and applications

A new class of optically active phosphine-oxazoline ligands has been synthesized wherein backbone chirality of these new ligands is installed by a Sharpless asymmetric dihydroxylation. Different backbone protecting groups as well as different substitution patterns on the oxazoline ring were studied. These ligands were tested in allylic substitution (with ee's up to 97%) and asymmetric Tsuji allylation.     

From allylic alcohols to chiral tertiary homoallylic alcohol: palladium-catalyzed asymmetric allylation of isatins

A palladium-catalyzed asymmetric allylation of isatins with allylic alcohols as an allyl donor was developed by using chiral spiro phosphoramidite ligands. A variety of chiral tertiary homoallylic alcohols 3-allyl-3-hydroxy-2-oxindoles were prepared directly from allylic alcohols in one step with excellent yields and moderate enantioselectivities. This represents the first catalytic asymmetric allylation of ketones with allylic alcohol as the allylating agent.     

The first catalytic asymmetric allylation of imines with the tetraallylsilane-TBAF-MeOH system, using the chiral bis-pi-allylpalladium complex

The asymmetric allylation of imines with use of catalytic transition metals with chiral ligands should be a new frontier of the enantioselective C-C bond formation. So far allyltrimethylsilane, allyltrichlorosilane, and allyltrimethoxysilane have been commonly employed with use of either silane activators or dual silane-imine activators. However, tetraallylsilane is untouched in the allylation of aldimines. The first allylation of aldimines with the tetraallylsilane-TBAF-MeOH system with use of the bis-pi-allylpalladium catalyst under catalytic, non-Lewis acid, essentially neutral and very mild reaction conditions has been achieved. The reaction is triggered by dual activation/promotion by TBAF and MeOH in which the fluoride anion activates the C-Si bond cleavage and MeOH promotes the facile protonation of intermediate palladium amide. Thus, the synthesis of chiral homoallylamines is achieved in a shorter reaction time and higher yields and enantioselectivities through an efficient, general, and reproducible allylation protocol for imines.     

Synthesis of new bicyclic P-N ligands and their application in asymmetric Pd-catalyzed pi-allyl alkylation and Heck reaction

[structure: see text] The synthesis of phosphine oxazoline ligands based on P-chiral 1-phosphanorbornadienes is reported. The use of these ligands in palladium catalyzed asymmetric allylation and Heck reaction is described.     

Synthesis of non-symmetric bis(oxazoline)-containing ligands and their application in the catalytic enantioselective Nozaki-Hiyama-Kishi allylation of benzaldehyde

We report the good to high-yielding three-step synthesis of non-symmetrical bis(oxazoline)-containing ligands possessing an N-thienylaniline unit. The convergent synthesis employed a palladium-catalysed aryl amination of 2-(2'-bromothiophene)nitrile as the key step, with sixteen ligands prepared in total. These ligands were subsequently applied in the chromium-catalysed enantioselective Nozaki-Hiyama-Kishi allylation of benzaldehyde with an optimal enantioselectivity of 73%.     

Chiral palladium bis(phosphite)PCP-pincer complexes via ligand C-H activation

The synthesis of a range of chiral palladium bis(phosphite) pincer complexes has been achieved via C-H activation of the parent ligands and one of the complexes formed shows good activity in the catalytic allylation of aldehydes.     

The influence of the phosphine ligand nature on palladium catalysts in the norbornadiene allylation with allyl formate

Russian Chemical Bulletin - The effect of the electronic and steric characteristics of phosphine ligands on the catalytic properties of palladium catalysts in the allylation of norbornadiene with...     

Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates in water

The activation of C-O bonds in allylic acetates in water as a suspension medium has been accelerated by carrying out the reactions in the presence of platinum complexes associated with ligands. The platinum-catalyzed allylation of aminonaphthalenes using allylic acetates gave the corresponding N-allylic aminonaphthalenes in good yields.     

New catalytic cycle for couplings of aldehydes with organochromium reagents

[reaction: see text] A new catalytic cycle has been developed to effect all three subgroups of Cr-mediated couplings, i.e., (1) Ni/Cr-mediated alkenylation, alkynylation, and arylation, (2) Co/Cr-mediated 2-haloallylation, alkylation, and propargylation, and (3) Cr-mediated allylation. In the presence of chiral sulfonamide ligands, good asymmetric inductions can be achieved for some of the Ni/Cr-mediated alkenylation, Co/Cr-mediated 2-haloallylation and propargylation, and Cr-mediated allylation.     

Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates

The activation of C-O bonds in allylic acetates has been accelerated by carrying out the reactions in the presence of platinum complexes associated with ligands. Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates leads to N-allylic aminonaphthalenes in good yields.     

Palladium‐Catalyzed Asymmetric C(sp3)−H Allylation of 2‐Alkylpyridines

The palladium‐catalyzed asymmetric side‐chain C(α)‐allylation of 2‐alkylpyridines, without using an external base, was developed. The high linear selectivities and enantioselectivities were achieved using new chiral diamidophosphite monodentate ligands. Given that the reaction conditions do not require an external base, this catalyst system enabled chemoselective C(α)‐allylation of 2‐alkylpyridines containing α‐carbonyl C?H bonds, which are more acidic than α‐pyridyl C?H bonds.     

手性钯络合物催化下2-硝基环酮的不对称烯丙基化反应

在用氮杂冠醚改良的手性二茂铁膦与钯的络合物催化下, 2-硝基环酮可进行不对称烯丙基化反应. 讨论了配位基的形状, 反应物的构造, 碱的类型以及反应时间对反应速率和立体选择性的影响. 通过增加反应的空间位阻改进了反应的立体选择性 .     

Allylation of N-heterocycles with allylic alcohols employing self-assembling palladium phosphane catalysts

The first palladium catalyst system that allows the direct allylation of indoles with allylic alcohols as substrates with water being the only byproduct is presented. The application of self-assembling ligands based on complementary hydrogen bonding was the key to success.     

P-stereogenic P/N hybrid ligands: a remarkable switch in enantioselectivity in palladium-catalyzed asymmetric allylation

Optically active P-stereogenic phosphine/oxazoline bidentate ligands (1) were prepared and applied to palladium-catalyzed allylic substitution of 1,3-diphenyl-1-acetoxy-2-propene with dimethyl malonate. The absolute configuration of the allylation product was remarkably switched by changing a palladium/ligand ratio between 1/1 and 1/2.     

Pd-catalyzed allylation of CH acids under phase-transfer conditions

The composition of the products obtained by Pd-catalyzed allylation of diethyl (alkyl)-malonates and ethyl cyanoacetate with allylic acetates under phase-transfer conditions using potassium carbonate or phosphate as bases depended strongly on the nature of the reactants and the ligands used. The highest yields and the fraction of the “linear” regioisomers were achieved in the reactions of prenyl or 3-methylbut-1-en-3-yl acetates in the presence of phosphordiamidite ligands.     

Derivatives of phosphorous acid as a new class of ligands for Pd-catalyzed allylation

Amido- and aminophosphites and hydrospirophosphoranes can be used as ligands in the Pd-catalyzed allylation of ethyl malonate with ethyl (3-phenylprop-2-enyl) carbonate. Bidentate ligands (RO)₂P--O(CH₂)_n--NR"₂ (n = 2 and 3) were found to be the most effective ligands.     

Chiral palladacycles based on resorcinol monophosphite ligands: the role of the meta-hydroxyl in ligand C-H activation and catalysis

The reactions of a range of chiral resorcinol monophosphite ligands with [PdCl(2)(NCMe)(2)] was investigated in order to establish whether the meta-hydroxyl function was involved in the orthometallation processes. These ligands underwent facile orthopalladation at room temperature in the presence of Et(3)N, whilst the equivalent hydroxyl-free analogues needed more forcing conditions to induce orthometallation. When the hydroxyl function was replaced by a similar sized methyl group no orthometallation occurred, even on heating. Furthermore the hydroxyl group influences both the structure and isomerism in the resultant palladacycles via hydrogen bonding to adjacent chloride ligands. Similarly, the hydroxyl function leads to higher enantiocontrol in the asymmetric allylation of benzaldehyde with allyl tributyltin. Representative examples of the ligands and the palladium complexes obtained were characterised by single crystal X-ray diffraction.     

Influence of Achiral Phosphine Ligands on a Synergistic Organo- and Palladium-Catalyzed Asymmetric Allylic Alkylation

An unusual diastereodivergent stereoselective allylation reaction is presented. It consists of a palladium-catalyzed allylation reaction of an organocatalytically generated amino isobenzofulvene, where the diastereoselectivity is controlled by the electronic properties of a monodentate, achiral ligand on palladium. One major diastereoisomer is formed using triarylphosphines substituted with neutral or electron-donating substituents of the aryl group, while those with electron-withdrawing substituents favor the other diastereoisomer. The diastereoselectivity correlates with the Taft inductive parameter of substituents on the triarylphosphine ligand on palladium. The synergistic reaction involves both a catalytic secondary amine catalyst for the indene-aldehyde activation and the monodentate phosphine ligands on palladium, affording a highly enantioselective reaction with up to 98 % enantiomeric excess. Based on computational investigations, the role of the monodentate phosphine ligand on the diastereoselectivity is discussed.     

Highly enantioselective Pd-catalyzed allylic alkylation of indoles using Sulfur-MOP ligand

The preparation of various (R)-Sulfur-MOP ligands with aryl and alkyl substituents on sulfur, and the application of these ligands to Pd-catalyzed asymmetric allylic alkylation of indoles is reported. The sulfur substituent served as an effective stereocontrol element, and in the case of the 2-i-PrPh substituent on sulfur, the allylation products from an array of simple and substituted indoles were obtained with high enantioselectivity (up to 95% ee).     

Chiral (S)‐(+) 1‐Substituted Aryl‐4‐(1‐phenyl) Ethylformamido‐5‐amino‐1,2,3‐triazole: A New Class of Chiral Ligands for the Silver(I)‐Promoted Enantioselective Allylation of Aldehydes

Some novel chiral ligands, (S)‐(+) 1‐substituted aryl‐4‐(1‐phenyl) ethylformamido‐5‐amino‐1,2,3‐triazoles, were prepared starting from 1‐substituted aryl‐4‐ethoxycarbonyl‐5‐amino‐1,2,3‐triazoles and other reagents. They were used as catalytic chiral ligands in the silver (I)‐promoted enantioselective allylation reaction of aldehydes with allyltributyltin.