Synthesis of N-alkyl-N′-aryl-piperazines via copper-catalyzed C–N bond formation

An efficient copper-catalyzed tandem synthesis of N-alkyl-N′-aryl-piperazines from 1,4-diaza-bicyclo[2.2.2]octane, alkyl halides, and aryl halides in the presence of copper(I) iodide and potassium tert-butoxide in DMSO is described.     

Lewis acid-catalyzed [3+3] cycloadditions of donor‒acceptor aziridines with N,N-dialkyl-3-vinylanilines via carbon-carbon bond cleavage

A Lewis acid-catalyzed [3 + 3] cycloaddition reaction of donor?acceptor aziridines with N,N-dialkyl-3-vinylanilines has been developed for the stereoselective synthesis of tetrahydroisoquinolines (THIQs). The reaction performed using Gd(OTf)₃ as the Lewis acid catalyst was tolerant to various N-tosylaziridine and N,N-dialkyl-3-vinylaniline substrates and provided access to highly functionalized THIQs in typically high yields with moderate-to-excellent diastereoselectivities.     

Chiral N,N′-dioxide-iron(II) complexes catalyzed enantioselective oxa-Michael addition of α,β-unsaturated aldehydes

The enantioselective oxa-Michael addition reaction of 1-(4-methoxyphenyl) ethanone oxime to various α,β-unsaturated aldehydes was accomplished by using chiral N,N′-dioxide-FeSO₄·7H₂O (1:1) complex. Aromatic acid was employed as additive to increase the yield of the reaction. The corresponding adducts were obtained in moderate yields with up to 76% ee under mild conditions.     

Three-component reaction of N′-(2-alkynylbenzylidene)hydrazide, α,β-unsaturated carbonyl compound, with bromine

Different outcomes were generated under different conditions for the three-component reaction of N′-(2-alkynylbenzylidene)hydrazide, α,β-unsaturated carbonyl compound, with bromine. 6-BromoH-pyrazolo[5,1-a]isoquinoline was obtained when the reaction was performed in NMP at 70 °C in the presence of DABCO as base, while 6-bromo-1,2,3,10b-tetrahydropyrazolo[5,1-a]isoquinoline was afforded when the reaction occurred in DMAc at 10 °C in the presence of K₃PO₄ as the base.     

Visible-light photo-catalytic C–C bond cleavages: preparations of N,N-dialkylformamides from 1,2-vicinal diamines

A range of 1,2-vicinal diamines were smoothly converted into N,N-dialkylformamides under the synergistic actions of Ru(bpy)₃Cl₂ photo-catalyst, 45 W household lighting bulb, and Cs₂CO₃ basic additive under very mild reaction conditions. The process involves visible light-enabled photo-catalytic cleavage of C–C bond as the strategic event.     

Unexpected C-C bond cleavage of α-nitroketone in the presence of TsNBr2: A new pathway for C-N bond formation

A new catalyst-free protocol for C-N bond formation via the cleavage of α-nitroketone has been developed. When α -nitroketones are treated with TsNBr₂ in the presence of potassium carbonate, unexpected cleavage of C(O)-CHNO₂ bond of α -nitroketone was observed followed by the formation of corresponding amide. Various nitroketones could be converted to corresponding amide using this procedure.     

Diastereoselective carbonyl phosphonylation using chiral N,N′-bis-[(S)-α-phenylethyl]-bicyclic phosphorous acid diamides

Addition of aldehydes to the P-anion derivatives of chiral phosphorous acid diamides (1S,2S,1′S,1″S)-2 and (1R, 2R,1′S,1″S)-2 in THF gave α-hydroxyphosphonamides in good yield (64-100%) and moderate diastereoselectivities.     

In vitro and in vivo studies of N,N′-bis[2(2-pyridyl)-methyl]pyridine-2,6-dicarboxamide–copper(II) and rheumatoid arthritis

The thermodynamic equilibria of copper(II), zinc(II) and calcium(II) with N,N′-bis[2(2-pyridyl)-methyl]pyridine-2,6-dicarboxamide (L1) have been studied at 25 °C and an ionic strength of 0.15 mol dm⁻³. Spectroscopic studies suggest metal ion complexation promotes deprotonation and coordination of the amide nitrogens resulting in overall tetragonal coordination of Cu²⁺. Blood–plasma modelling predicts that Cu(II) competes effectively against Zn(II) and Ca(II) for L1 in vivo. Octanol–water partition coefficient studies show that Cu(II)–L1 complexes are reasonably lipophilic. However, the CuL1H₋₂ species which predominates at the physiological pH of 7.4 has poor superoxide dismutase activity. Bio-distribution experiments showed activity accumulation and retention in the body of about 50% of the injected dose for the [⁶⁴Cu]Cu(II)–L1 complex after 24 h.     

Vinylation of trialkylamines with acyl- and cyanoacetylenes via C–N bond cleavage in the presence of water

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Cu(OAc)2 promoted Chan–Evans–Lam C–N cross coupling reactions on the N- and N′-nitrogen atoms of sulfonimidamides with aryl boronic acids

We report a highly efficient and mild protocol for Chan–Evans–Lam C–N cross coupling of sulfonimidamides and aryl boronic acids using Cu(OAc)₂ as mediator, triethylamine (TEA) as base and acetonitrile as solvent. The reaction proceeds at room temperature and provides high to excellent yields for a variety of boronic acids, allowing N-arylation of both N-protected (N-amine nitrogen) and N-deprotected (N′-imine nitrogen) sulfonimidamides.     

XPS,single crystal X-ray diffraction and cyclic voltammetric studies on 1,10-phenanthroline and 2,2′-bipyridine adducts of bis(piperidinecarbodithioato-S,S′)cadmium(II) with CdS4N2 environment – A stereochemical and electronic distribution investigation

(1,10-Phenanthroline)bis(piperidinecarbodithioato-S,S^′)cadmium(II), [Cd(pipdtc)₂(1,10-phen)] (1) and (2,2′-bipyridine)bis(piperidinecarbodithioato-S,S′)cadmium(II), [Cd(pipdtc)₂(bipy)] (2) adducts were prepared and the crystal structures are reported. Cd–S and Cd–N distances and the angles subtended at cadmium are almost the same in both complexes but the Cd–S distances in the adducts are longer than those in Cd(pipdtc)₂ (3) complexes due to the presence of an additional neutral ligand. Thioureide C–N distance in 1 and 2 are supported by νC–N bands observed at 1471 and 1470 cm⁻¹, respectively. S2p binding energies for the adducts show a significant reduction in value compared to the parent dithiocarbamate indicating the weakening of the Cd–S bond on adduct formation. The observed reduction in binding energy is due to the increased electron density on the metal in the adducts. The cyclic voltammetric study on the complexes also show an increase of electron density on cadmium in the adducts compared to Cd(pipdtc)₂.     

Investigation of the reaction of α-thioamides, α-esters and α-nitriles with N-halosuccinimides

Investigation of the reaction of α-thioamides, α-esters and α-nitriles with NBS and NCS is described. The scope of this stereoselective oxidative transformation to the β-haloacrylamides, β-acrylates and β-acrylonitriles has been determined. A mechanistic rationale to explain the observed differences in reactivity between the amide, ester and nitrile series is proposed.     

A simple and fast liquid–liquid extraction method for the determination of 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p′-DDE) from human serum for epidemiological studies on type 2 diabetes

A simple and fast method is presented to be used for example in studies on the relationship between serum levels of persistent organic pollutants and type 2 diabetes mellitus. Method is based on liquid–liquid extraction and gas chromatography coupled with high-resolution mass spectrometry. In the sample pre-treatment special attention was paid to minimize the number of sample manipulation steps and the amounts of organic solvents needed. Compounds analyzed were 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p′-DDE), the major metabolite of DDT. The method included extraction and cleanup of 0.2 ml of serum in a single test tube and subsequent analysis of the extract from 0.2 ml final volume. Validation was conducted to explore the performance of the method. The limits of detection for p,p′-DDE and PCB-153 based on the standard deviation of the blank samples were 4.3 and 3.1 pg/ml, respectively. Repeatability was less than 2.5% at three concentration levels tested and recovery from Certified Reference Material SRM 1589a was 84% for p,p′-DDE and 87% for PCB-153 of the certified values, respectively. Serum samples from the AMAP intercalibration round 2008-2 were also analyzed, and results were 101–116% of the assigned values. The presented method was used for an epidemiological study with more than 700 serum samples from a type 2 diabetes cohort from Sweden.     

Synthesis,structure and spectroelectrochemical property of (2,2′-bipyridine)–metal (M = Pt,Pd) dichloride with 4,4′-bis(fluorous-ponytail) on bipyridine

The 4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy ligands [R_f = n-C₃F₇ (1a), HCF₂(CF₂)₃ (1b)] were prepared and then treated with [MCl₂(CH₃CN)₂] (M = Pt or Pd) to result in the corresponding metal complexes, [MCl₂(4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy)] (M = Pt 2a–b; Pd 3a–b). Both ligands and metal complexes were fully characterized by multi-nuclei NMR (¹H, ¹⁹F and ¹³C), FTIR, and mass (GC/MS or HR-FAB) methods. The X-ray structures of 2a–b and 3a–b were studied. With terminal CF₃, the structures of 2a and 3a exhibit disordered polyfluorinated regions in solid state. With terminal HCF₂, the structures of 2b and 3b show a π–π stacking of the bpy planes, five-membered C–H···O hydrogen bond and an unusual intramolecular blue-shifting C–H···F–C hydrogen bond system, whereas without terminal HCF₂, the structures of 2a and 3a show the similar π–π stacking, five-membered C–H···O hydrogen bond and typical orientation of polyfluorinated ponytails, but not the C–H···F–C hydrogen bond system. The CV and UV/Vis studies were also carried out.     

Acuminatanol, the first 2′,2?-bis-dihydrobiflavonol from the aqueous extract of Trichoscypha acuminata

One new 3′,4′,5′,5,7-pentahydroxy-2′,2?-bis-dihydrobiflavonol, acuminatanol (1), was obtained from the aqueous extract of Trichoscypha acuminata. The structure elucidation process was performed primarily utilizing a capillary scale NMR probe. Acuminatanol (1) is the first example of a bis-dihydroflavonol linked exclusively via the B-rings at C-2′ and C-2? positions. To date, it is the first naturally-occurring compound reported from the genus Trichoscypha, and the first new natural product published from our compound libraries generated from the aqueous extracts of American and African plants.     

Stereoselective anti-SN2′ Mitsunobu reaction of α-hydroxy-α-alkenylsilanes

A novel silyl group-directed anti-S_N2′ reaction of allylic alcohols under Mitsunobu reaction conditions is described. The Mitsunobu reaction of α-hydroxy-α-alkenylsilanes with a TBS or TIPS group gave the anti-S_N2′ product, in which regio- and stereochemical outcomes of the reaction depended on the steric bulkiness of the silyl group.     

Role of cyanide in reaction with cis-dichlorobis(2,2′-bipyridine)Co(III) chloride in water

Although cyanide does not substitute chloride in the cis-dichlorobis (ethylenediamine)Co(III) cation in water, it does so in the analogous 2,2′-bipyridine-containing complex.     

Electron transfer reaction of 4,4′-bipyridine with triethylamine in acetonitrile: effect of water addition on the reaction dynamics

The photo-induced electron-transfer reaction of 4,4-bipyridine (BPY) with triethylamine (TEA) in acetonitrile is studied by laser flash photolysis. The reaction mechanism and kinetics are found very sensitive to the presence of a small amount of water. At low water concentrations (i.e. <0.003 M), an extremely fast-rising metastable product is detected for the first time. A triplet charge transfer complex (³ECT) is found to be the primary intermediate preceding the electron transfer process. Up to about 0.1 M, water facilitates the electron transfer rate, whereas higher water concentrations retard the rate of electron transfer. The Stern-Volmer plot of the triplet decay rate versus the TEA concentration is consistent with the presence of ³ECT in equilibrium with the free excited triplet state of BPY.     

Oligomerization of α-olefins by the dimeric nickel bisamido complex [Ni{1-N(PMes2)-2-N(μ-PMes2)C6H4-κN,N′,P,-κP′}]2 activated by methylalumoxane (MAO)

The reaction of Li₂[1,2-{N(PMes₂)}₂C₆H₄], formed in situ from n-BuLi and the corresponding amines, with 1 equiv. of [NiBr₂(DME)] gives [Ni{1-N(PMes₂)-2-N(μ-PMes₂)C₆H₄-κ³N,N′,P-κ¹P′}]₂ (1). After activation by methylalumoxane (MAO), 1 is a highly active catalyst in the oligomerization and isomerization of α-olefins such as ethene, propene, isobutene, 1-hexene and 1,5-hexadiene. For ethene oligomerization turnover frequencies (TOFs) range from 3000 to 79015 h⁻¹, depending on the reaction conditions. The TOF for propene oligomerization reaches 1 190 730 h⁻¹. To our knowledge, catalyst 1, activated by MAO, is the most active catalyst for the oligomerization of propene and outperforms the best known complexes for this reaction. In the reactions with 1-hexene, 1,5-hexadiene and isobutene dimerization and isomerization products were observed.