Nitration of Halterman porphyrin: a new route for fine tuning chiral iron and manganese porphyrins with application in epoxidation and hydroxylation reactions using hydrogen peroxide as oxidant

A methodology is reported for the regioselective nitration of the phenyl groups of Halterman porphyrin, using NaNO₂. These nitro-porphyrins can be reduced to aminoporphyrins and then N-dimethylated to give new optically active porphyrins. Applications to the asymmetric epoxidation of styrene derivatives by H₂O₂ to give optically active epoxides (ee up to 60%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 69%) were carried out in organic solvents (dichloromethane/methanol) using chiral iron and manganese porphyrins as catalysts.     

Enantioselective water-soluble iron–porphyrin-catalyzed epoxidation with aqueous hydrogen peroxide and hydroxylation with iodobenzene diacetate

The asymmetric epoxidation of styrene derivatives by H₂O₂ (or UHP) to give optically active epoxides (ee up to 81%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 78%) were carried out in methanol and water using chiral water-soluble iron porphyrins as catalysts.     

Catalytic asymmetric bromination and chlorination of beta-ketoesters

The first general catalytic asymmetric bromination and chlorination of beta-ketoesters has been developed. The reactions proceed for both acyclic and cyclic beta-ketoesters catalyzed by chiral bisoxazolinecopper(II) complexes giving the corresponding optically active alpha-bromo- and alpha-chloro-beta-ketoesters in high yields and moderate to good enantioselectivities. For the optically active chlorinated products the isolated yields are in the range of 88-99 % and the enantiomeric excesses up to 77 % ee, while the optically active brominated adducts are formed in 70-99 % isolated yield and up to 82 % ee. Based on the absolute configuration of the optically active products, the face selectivity for the catalytic enantioselective halogenation is discussed based on a bidentate coordination of the beta-ketoester to the chiral catalyst and a X-ray structure of chiral alpha,gamma-diketoesterenolatebisoxazolinecopper(II) complex.     

Synthesis of chiral water-soluble metalloporphyrins (Fe, Ru,): new catalysts for asymmetric carbene transfer in water

The reaction of optically active Halterman porphyrin with sulfuric acid (95%) provided the expected water-soluble para-tetrasulfonated porphyrin in 82% yield. The metalloporphyrin complexes were prepared by metal insertion (iron) or direct sulfonation of the chiral ruthenium porphyrin. The asymmetric addition of diazoacetate to styrene to give optically active trans cyclopropyl ester (ee up to 86%) was carried out in water by using chiral iron or ruthenium porphyrins with a possible reuse due to the high solubility and stability in aqueous solution.     

Enantioselective addition of diethylzinc to aldehydes in the presence of chiral aprotic ligands

Optically active amino thiocyanate derivatives of (−)-norephedrine were found to act as effective aprotic ligands for enantioselective addition of diethylzinc to aldehydes. This reaction provided optically active secondary alcohols with ee up to 96%.     

High-efficiency and minimum-waste continuous kinetic resolution of racemic alcohols by using lipase in supercritical carbon dioxide

A novel continuous-flow scCO(2) process for kinetic resolution of racemic alcohols can be performed with an immobilized lipase to lead to a quantitative mixture of the corresponding optically active acetates with up to 99% ee and unreacted alcohols with up to 99% ee, in which the productivity of the optically active compounds was improved by over 400 times compared to the corresponding batch reaction using scCO(2).     

Asymmetric Syntheses XXVI: Catalytic Enantioselective Syntheses of β-Hydroxy Esters via Double Chiral Induction in Asymmetric Reformatsky Reactions

Catalytic asymmetric Reformatsky reactions of benzaldehyde with optically active menthyl bromoacetates in the presence of Zn-Cu couple were performed using 0.25 equiv. of (1R,2S) or (1S,2R)-dimethyl-2-amino-1,2-diphenyl ethanol as chiral ligand to obtain β - hydroxy esters with enantioselectivities up to 60.2%. The obvious double chiral induction effect was observed while chiral ligands matched with optically active substrates.     

Optically active thiophenes via an organocatalytic one-pot methodology

A general methodology for the synthesis of trisubstituted, optically active thiophenes by an organocatalytic one-pot reaction cascade is presented. The target products are synthesized in good yields (up to 92%) and with excellent enantioselectivities (up to 98% ee). Importantly, based on practical and easily available starting materials, the presented methodology can be conducted under mild reaction conditions. To further elucidate the generality, the synthesis of optically active thienoindoles, as well as selenophenes, is also demonstrated.     

Highly enantioselective synthesis of β-hydroxysulfonamides by asymmetric transfer hydrogenation

A series of optically active β-hydroxy sulfonamides were synthesized for the first time by asymmetric transfer hydrogenation of the corresponding β-ketosulfonamides using the Ru-TsDPEN-HCOOH-Et₃N catalytic system, in excellent yields (up to 95%) with excellent diastereo- (up to > 99:1 dr) and enantioselectivities (up to >99% ee).     

Enantioselective Synthesis of N‐Phenyl‐dihydropyrano[2,3‐c]pyrazoles via Cascade Michael Addition/Thorpe‐Ziegler Type Cyclization Catalyzed by a Chiral Squaramide

Enantioselective synthesis of biologically active dihydropyrano[2,3‐c]pyrazoles has been achieved through a squaramide‐catalysed Michael addition/Thorpe‐Ziegler type cyclization cascade reaction between arylidenepyrazolones and malononitrile. A series of optically active dihydropyano[2,3‐c]pyrazoles were obtained in excellent yields (up to 99%) and moderate to good enantioselectivities (up to 79% ee) under mild reaction conditions.     

Asymmetric Reduction of Prochiral Ketones in Aqueous Micelles of Chiral Surfactants (-)-Trialkylmskthylammcnium Bromides

Prochiral Ketones were reduced by NaBH₄ in aqueous micelles formed from chiral surfactants (-)-N-alkyl-N,N-dimethylmenthylammonium bromides, giving optically active alcohols with enantioselectivity up to 17.7%.     

Practical synthesis of optically active styrene oxides via reductive transformation of 2-chloroacetophenones with chiral rhodium catalysts

[reaction: see text] A practical method for the synthesis of optically active styrene oxides has been developed via formation of optically active 2-chloro-1-phenylethanols generated by reductive transformation of ring-substituted 2-chloroacetophenones. The optically active alcohols with up to 98% ee are obtainable from the asymmetric reduction of acetophenones with an S/C = 1000-5000 with a formic acid triethylamine mixture containing a well-defined chiral Rh complex, CpRhCl[(R,R)-Tsdpen].     

Cholesterol vinyl ether in free-radical homo-and copolymerization reactions

Vinyl ether of cholesterol has been polymerized through the free-radical mechanism with a yield of up to 30% to obtain optically active soluble oligomers. By the example of acrylonitrile, N-vinylpyrrolidone, ethylene glycol vinyl glycidyl ether, and N-vinyl-4,5,6,7-tetrahydroindole, it has been established that optically active copolymers of cholesterol may be synthesized.     

Hydrogen-transfer polymerization of acrylamide and methacrylamide with optically active basic catalysts

Hydrogen-transfer polymerization of acrylamide and Methacrylamide with an optically active amyl alcoholate or n-amyl alcoholate (sodium, calcium, magnesium, barium, and aluminum) was investigated to 100°C in toluene. The initiation ability of the metal ion of the initiator increased in the order, sodium > barium > calcium > magnesium > aluminum. The optically active polymer was obtained by the polymerization of methacrylamide with an optically active alcoholate (barium or calcium), but was not obtained by the other alcoholates and by the polymerization of acrylamide with the optically active alcoholate. The specific rotation of the optically active polymer obtained was about +1.1° ～ +1.3°. The hydrolyzed product of the optically active polymer was α-methyl β-alanine having optical activity (+1.0°). The initiation mechanisms of the polymerization were thought to be the dehydrogenation of the monomer of the negative ion and the Michael addition reaction with the monomer of the negative ion and the catalyst, and it was confirmed that the optically active polymer was prepared by intermolecular hydrogen transfer mechanism. In the polymerization of MMA with menthol barium and borneol barium as the optically active catalyst, the optically active polymer was obtained.     

Asymmetric Catalysis by Vitamin B12: The Isomerization of Achiral Aziridines to Optically Active Allylic Amines

Achiral N-acylaziridines are isomerized to optically active N-acyl-allylamines in ee's of up to 95% by catalytic amounts of cob(I)alamin in MeOH.     

Editorial

Abstract

Asymmetric syntheses of optically active polymethacrylate, polyacrylate, polyacrylamide, and polyisocyanate with helical conformation and their chiral recognition abilities are described. 1-Phenyldibenzosuberyl methacrylate (PDBSMA) gave a purely onehanded-helical, optically active polymer ([α]₃₆₅ +1670 ～ +1780º) with almost perfectly isotactic structure by anionic polymerization using optically active initiators. Radical polymerizations of PDBSMA using chiral initiators, chain transfer agents, and additives also afforded optically active polymers with a prevailing onehanded helicity. Triphenylmethyl acrylate yielded an optically active, helical polymer ([α]₃₆₅ +102º) having a dyad isotacticity of 70% using an optically active anionic initiator. Although the polyacrylate demonstrated chiral recognition ability as a chiral stationary phase for HPLC, the ability was low mainly because of the low degree of one-handedness. N-(3-Chlorophenyl)-N-phenylacrylamide gave an optically active, helical polymer ([α]_365–343º) in the asymmetric anionic polymerization; the polymer had a dyad tacticity of 77%. Optically active polyisocyanates with a predominantly one-handed helical conformation were prepared in homo-and co-polymerization of optically active phenyl isocyanate derivative. These polyisocyanates showed the ability to discriminate enantiomers in solution.     

铑-ImiFerroPhos配合物对β-取代-α,β-不饱和磷酸酯的不对称氢化

将手性二茂铁双膦配体ImiFerroPhos应用到β-取代-α,β-不饱和磷酸酯的不对称氢化反应中,在温和的反应条件下,以高收率及较高对映选择性合成了一系列β-取代的手性磷酸酯,最高获得了92%的ee值.     

A one-pot asymmetric organocatalytic tandem reaction for the synthesis of oxazine derivatives

An easy one-pot tandem reaction catalyzed by a chiral secondary amine for the synthesis of optically active oxazine derivatives has been performed and the corresponding substituted benzo[d]pyrido[2,1-b][1,3]oxazine derivatives were afforded in generally high yields (up to 99%) and excellent enantioselectivities (up to >99%).     

Enantioselective chlorination and fluorination of beta-keto phosphonates catalyzed by chiral Lewis acids

The direct chiral Lewis acidic enantioselective chlorination and fluorination of beta-keto phosphonates is presented; the chlorination proceeds in high yields and with up to 94% ee using NCS as the chloro source, while the fluorination with (PhSO2)2NF (NFSI) gives the optically active alpha-fluoro-beta-keto phosphonates in moderate to good yields and with up to 91% ee.     

A practical synthesis of optically active aromatic epoxides via asymmetric transfer hydrogenation of α-chlorinated ketones with chiral rhodium-diamine catalyst

A practical method for the synthesis of optically active aromatic epoxides has been developed via the formation of optically active α-chlorinated alcohols and intramolecular etherification. Optically active alcohols with up to 99% ee can be obtained from the asymmetric reduction of aromatic ketones with a substrate/catalyst ratio of 1000-5000 using a formic acid/triethylamine mixture containing a well-defined chiral Rh complex, Cp*RhCl[(R,R)-Tsdpen]. The asymmetric reduction of α-chlorinated aromatic ketones with a chiral Rh catalyst is characterized by a rapid and carbonyl group-selective transformation because of the coordinatively saturated nature of diamine-based Cp*Rh(III) hydride complexes. The outcome of the reduction is significantly influenced by the structures of the ketonic substrates as well as the hydrogen source such as formic acid or 2-propanol. Commercially available reagents and solvents can be used in this reaction without special purification. This epoxide synthetic process in either a one- or two-pot procedure is practical and particularly useful for the large-scale production of optically active styrene oxides from α-chlorinated ketones.