Me-AnilaPhos: a new chiral phosphine-phosphoramidite ligand for a highly efficient Rh-catalyzed asymmetric olefin hydrogenation

A cationic rhodium(I) complex with a novel chiral phosphine-phosphoramidite ligand based on 2-diphenylphosphino-N-methylaniline and R-BINOL moieties has been synthesized. The complex provided remarkably high activity and enantioselectivity in the asymmetric hydrogenation of methyl (Z)-α-acetamidocinnamate (100% conversion after 10 min, 98% ee) and dimethyl itaconate (100% conversion after 26 min, 96% ee) under ambient conditions (1 bar hydrogen pressure, room temperature) using 1 mol % of the catalyst in dichloromethane as solvent. On the other hand, when hydrogenation was performed in methanol, both conversion and enantioselectivity were significantly diminished, due to the partial decomposition of the rhodium/phosphine-phosphoramidite complex.     

1,2-Bis(2,5-diphenylphospholano)methane, a new ligand for asymmetric hydrogenation

1,2-Bis(2,5-diphenylphospholano)methane (Ph-BPM) has been prepared in good yield from 2,5-trans-diphenylphospholane-borane adduct. Rhodium and ruthenium complexes of this ligand have been prepared and their usefulness in asymmetric hydrogenation has been investigated. [Ph-BPM Rh(COD)]BF₄ showed high activity and selectivity for itaconate and dehydroamino acid hydrogenation. Ph-BPM RuCl₂(DPEN) was effective for imine hydrogenation.     

Organocatalysis using protonated 1,2-diamino-1,2-diphenylethane for asymmetric Diels-Alder reaction

Bisammonium salts of mono-N-alkylated chiral 1,2-diamino-1,2-diphenylethane (DPEN) were employed in the catalytic and asymmetric Diels-Alder reaction between cyclopentadiene and crotonaldehyde. The N-3-pentyl diamine·2HCl catalyst shows high endo/exo selectivity and endo-enantioselectivity for the cycloaddition, and this organocatalysis is the first example of the use of a chiral 1,2-diamine to generate an imine intermediate which is activated by an internal ammonium Brønsted acid for the cycloaddition in a wet solvent.     

Optically active 1-Alkoxy-2,2-bis(trifluoromethyl)aziridines

1-Alkoxy-2,2-bis(trifluoromethyl)aziridines containing an ester group in the position of the alkoxy substituent undergo nucleophilic substitution (ammonolysis and hydrolysis) with retention of the aziridine ring. The corresponding carboxylic acids, which were separated to give the antipodes with an optical purity of 95% through the diastereomeric salts with R- and S--phenylethylamine, were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1495–1500, November, 1980.     

A new chiral sulfinyl-NH-pyridine ligand for Ir-catalyzed asymmetric transfer hydrogenation reaction

A new flexible C₁-symmetric tridentate ligand (S)-N-(2-(tert-butylsulfinyl)benzyl)-1-(pyridin-2-yl)methanamine sulfoxide (L1) was successfully prepared and utilized as a chiral ligand for Ir(I)-catalyzed ATH (asymmetric transfer hydrogenation) reactions. Without any cooperation of other chiral center, encouraging ee and conversion values have been achieved, which provide us a better understanding on these types of ligands and a new strategy to develop new high-efficiency chiral catalysts for asymmetric reaction.     

Copper(II)-bis(oxazoline) catalyzed asymmetric Diels-Alder reaction with alpha'-arylsulfonyl enones as dienophiles

Alpha'-arylsulfonyl enones are efficient bidentate dienophiles for the Cu(II)-bis(oxazoline) catalyzed enantioselective Diels-Alder reaction with a number of dienes, affording the corresponding products with good to high enantiomeric excesses. The resulting products can be alkylated and the sulfone removed, so alpha'-arylsulfonyl enones can be regarded as surrogates of simple monodentate enones, which are poor dienophiles with this catalytic system.     

Synthesis of phellanphos,an efficient chiral 1,2-diphosphine for asymmetric catalysis

A chiral 1,2-diphosphine was prepared in two steps from ()-α-phellandrene. This phosphine phellanphos gives a cationic rhodium complex (phellanphos-cyclooctadienerhodium hexafluorophosphate) which catalyses asymmetric reductions. N-Acetylphenylalanine and N-acetylalanine have been prepared in 94–95% enantiomeric excess.     

2-alkenoyl pyridine N-oxides, highly efficient dienophiles for the enantioselective Cu(II)-bis(oxazoline) catalyzed Diels-Alder reaction

2-Alkenoyl pyridine N-oxides are introduced as a new kind of efficient dienophiles for the Cu(II)-bis(oxazoline) (BOX) catalyzed enantioselective Diels-Alder reaction affording higher reactivity and enantioselectivity (ee's up to 96%) than the corresponding nonoxidized 2-alkenoyl pyridines.     

Synthesis of a new chiral amino phosphine ligand and its application in the asymmetric allylic alkylation (AAA) reaction

This article describes the synthesis of a new chiral amino phosphine ligand based on an amino naphthol starting material, which is resolved efficiently by using l-tartaric acid. The asymmetric induction of the ligand in the Pd(0)-catalyzed allylic substitution of 1,3-diphenylprop-2-en-1-yl acetate with dimethyl malonate was investigated. Good yields and enantiomeric excesses up to 78% of the product were obtained.     

Design of a new and highly effective chiral auxiliary for Diels-Alder reaction of 1-aminodiene

A theoretical investigation of the facial selectivity of optically active oxazolidin-2-one-substituted dienes has been realized. This analysis enabled the development of (R)-4-phenyloxazolidin-2-thione as a very effective chiral auxiliary for cycloaddition of 1-aminodiene.     

Assembly of a new Keggin polyoxometalate-templated complex using flexible 1,2-bis(imidazol-1′-yl)ethane ligand

A new compound, [{Cu^I(bim)}₄{SiW₁₂O₄₀}] (1) (bim?=?1,2-bis(imidazol-1′-yl)ethane), was hydrothermally synthesized and characterized by elemental analyses, IR, TG, and single-crystal X-ray diffraction. Compound 1 is an infinite 1-D chain composed of Cu-bim coordination polymers and [α-SiW₁₂O₄₀]^4? polyanions. The electrochemical and electrocatalytic behaviors of 1-modified carbon paste electrode (1-CPE) have been studied.     

Asymmetric synthesis of 1,2-bis(diphenylphosphino)-1-phenylethane via a chiral palladium template promoted hydrophosphination reaction

An organopalladium(II) complex derived from (S)-N,N-dimethyl-1-(1-naphthyl)-ethylamine was employed as the chiral auxiliary to promote the asymmetric hydrophosphination reactions between diphenylphosphine and (E) or (Z)-diphenylphosphinostyrene in high regio- and stereoselectivities at low temperature with triethyl amine as external base. Optically active free ligand (R)-1,2-bis(diphenylphosphino)-1-phenylethane was obtained in high yield subsequently. Mechanistic pathways explaining the stereoselectivity of the chiral organopalladium template promoted hydrophosphination reactions are also proposed.     

Poly(methylhydrosiloxane)-supported chiral imidazolinones: new versatile, highly efficient and recyclable organocatalysts for stereoselective Diels-Alder cycloaddition reactions

Poly(methylhydrosiloxane) (PMHS) supported organic catalysts promoted the Diels-Alder reaction of dienes with α,β-unsaturated aldehydes, also in pure water, in yields and enantiomeric excesses comparable to those observed with the non-supported catalysts (up to 93% ee). Recycling of the catalysts was performed with no loss of enantioselectivity for at least five reaction cycles.     

Preparation of new bis(oxazoline) ligand bearing non-covalent interaction sites and an application in the highly asymmetric Diels-Alder reaction

New asymmetric bis(oxazoline) (Box) ligand bearing amide group at the oxazoline 4-position, (S,S)-2,2′-methylenebis(4-tert-butylcarbamoyl-2-oxazoline) (1S), was designed and synthesized for selective catalytic reaction. The crystal structure of the ternary copper complex, consisting of 1S and N-benzoyl-N-phenyl-hydroxylamine, demonstrated interligand interactions, such as hydrogen bonding and CH-π interaction. Catalytic performance of the copper complex with 1S was investigated for an asymmetric Diels-Alder reaction using benzylidene-2-acetylpyridine and 1,3-cyclohexadiene (CHD). The reaction product was enantio-pure endo-(pyridin-2-yl)(3-phenylbicyclo[2,2,2]oct-5-ene-2-yl)methanone (BPCD), of which crystal structure was analyzed by the X-ray method. No stereo- and enantio-isomer of BPCD was detected by chiral HPLC analysis. Introduction of hydrogen bonding site into 1S can promote the Diels-Alder reaction even though using poor reactive CHD. Without 1S, this reaction did not give any product. Addition of 2-propanol to this reaction system inhibited the formation of BPCD, indicating that the designed interligand interaction sites, especially hydrogen bonding, play an important role for catalytic performance.     

Catalytic enantioselective Diels-Alder reaction via a chiral indium(III) complex

[reaction: see text] A chiral indium complex has been developed to effect high enantioselectivities in catalyzing enantioselective Diels-Alder reaction. The cycloaddition of a variety of cyclic and open-chained dienes to 2-methacrolein and 2-bromoacrolein resulted in good yields and excellent enantioselectivities (up to 98% ee).     

Optically active beta-ketoiminato cationic cobalt(III) complexes: efficient catalysts for enantioselective carbonyl-ene reaction of glyoxal derivatives

[see reaction]. Optically active beta-ketoiminato cationic cobalt(III) complexes were synthesized as effective Lewis acid catalysts for the enantioselective carbonyl-ene reaction. In the presence of a catalytic amount of cobalt(III) hexafluoroantimonate derived from the optically active 1,2-diphenyl-1,2-ethanediamine, the carbonyl-ene reaction with a variety of alkenes and glyoxal derivatives smoothly proceeded to afford the corresponding homoallylic alcohols in good-to-high yields with high enantioselectivities.     

Stereoselective pinacol coupling of chiral formylferrocene using divalent samarium triflate: preparation of a new chiral bisferrocenyl oxazoline ligand and its application to asymmetric Diels-Alder reactions

[reaction: see text] The pinacol coupling reaction of planar chiral ortho-oxazoline-substituted formylferrocene was smoothly mediated by SmI2 or Sm(OTf)3 to give the (R,R) isomer selectivity (up to 76% diastereomeric excess). The combination of Yb(OTf)3 and the (R,R)-ferrocenyl diol was revealed to be a good catalyst for the asymmetric Diels-Alder reaction of 3-acyloxazolidinone with cyclopentadiene, and the endo adduct was produced in up to 80% enantiomeric excess.     

A new chiral iminophosphine ligand derived from (1S,4S)-fenchone in palladium-catalyzed asymmetric allylic alkylations

A new chiral iminophosphine ligand derived from (1S,4S)-fenchone has been developed, and its usefulness as a chiral ligand in asymmetric synthesis was demonstrated in palladium-catalyzed allylic alkylations.