Synthesis of Enamines via the Cross-coupling of Thioamides and Diarylketones Promoted by the Sm/SmI_(2)Mixed Reagent

Enamines, promoted by the samarium/samarium diiodide mixed reagent, were synthesized via the cross-coupling of thioamides and diarylketones in good yields.

Synthesis Characterization and Biological Activities of an Enamine Derivative and Its Coordination Compounds

The medicinal uses and applications of metal complexes are of increasing clinical and commercial importance;this is as a result of some level of success achieved so far. In this regard, novel enamine free-base ligands were synthesized by the condensation of terephthalaldehyde and 2-(methylamino)ethanol. This afforded a dinegative ONNO donor enamine, free base, characterized using 1H and 13C NMR, Fourier-transformed infrared and UV-vis spectroscopy. Coordination compounds of the enamine were also synthesized using Cu(II), Ni(II), Co(II) and VO(IV) ions. These complexes were characterized by electronic, IR spectrophotometry, mass spectrometry, magnetic susceptibility and EDX. The compounds were thereafter evaluated for their antimicrobial and cytotoxic activities. The data obtained were supportive of an octahedral geometry for the Cu(II) complex, a square-pyramidal geometry for the vanadium complex and a 4-coordinate square-planar geometry for both the cobalt and nickel complexes. The magnetic susceptibility data revealed that the complexes are magnetically dilute and mononuclear with exception of the cobalt complex. The ligands and the complexes did not exhibit significant antimicrobial and cytotoxic assays, indicative of the nontoxicity of the ligand and complexes.

Relative Stability of the Key Enamine,Oxazolidinone,and Imine Intermediates in Some Proline-catalyzed Asymmetric Reactions

Many proline-catalyzed asymmetric addition reactions with ketones as substrates were assumed to involve a key intermediate, an enamine, produced by the condensation of proline and ketone. In this paper, the key intermediate enamines derived from L-proline and cyclohexanone （or acetone） as well as the corresponding oxazolidinone and imine tautomers have been investigated by means of density functional calculations at the B3LYP/6-311＋G^＊＊ level. The predicted order of stability for these tautomers is oxazolidinones 〉 enamines 〉 imines in gas phase and oxazolidinones 〉 imines 〉 enamines in aprotic THF solvent. This prediction explains why enamine intermediate can not be observed experimentally. The predicted energy/enthalpy difference between the formal oxazolidinone structure and the zwitterionic imine structures is very small in THF solvent, suggesting the oxazolidinone-to-imine tautomerization can be readily induced in solvent. ^13C NMR chemical shifts of the oxazolidinone and imine structures have been computed and used to explain the experimental NMR spectra observed in oxazolidinone-to-imine tautomerization induced by protic solvent.

Enamine Configuration of 5-Methyl-2-phenyl-4- [(Z)-3-tolylamino-phenylmethylene]pyrazol-3(2H)-one

Compound 5-methyl-2-phenyl-4-[（Z）-3-tolylamino-phenylmethylene]pyrazol-3（2H）-one （C24H21N3O） crystallizes in the triclinic system, space group P1, with a = 9.267（3）, b = 9.904（4）,c = 12.035（4） A°, α = 97.896（6）, β = 103.865（6）, γ = 107.950（6）°, Mr= 367.44, Z = 2, V = 993.2（6）A°^3,Dc = 1.229 g/cm^3,μ（MoKa） = 0.077 mm^-1 and F（000） = 388. The structure was refined to R =0.0444 and wR = 0.1199 for 2903 observed reflections （I 〉 2σ（I））. The results of ^1H NMR and single-crystal X-ray diffraction studies showed the enamine character of the compound. The strong intramolecular hydrogen bonds in the large conjugate system, together with weak intermolecular C-H……π hydrogen bonding and π……π stacking, lead to the formation of a multi-dimensional supramolecular network.

Efficient preparation of trans-α,β-unsaturated aldehydes from saturated aldehydes by oxidative enamine catalysis

A mild and highly efficient amine-catalyzed, IBX-mediated oxidation of aldehydes to （E） selective a, β-unsamrated aldehydes has been achieved in good yields. The process features a new oxidation of enamines to iminium ions in a catalytic fashion.

An Efficient and Green Approach to Synthesizing Enamines by Intermolecular Hydroamination of Activated Alkynes

An efficient, atom-economic and green approach to synthesizing enamines was developed by intermolecular hydroamination of activated alkynes with high yields under catalyst- and solvent-free conditions. β-Dimethylamino-acrylate derivatives were also obtained with high yields. In the synthetic process of the derivatives, N,N-dimethylformamide（DMF） pretreated with metal Na, was used as reactant instead of dimethylamine gas. The proposed synthetic method can be used for the synthesis of （E）-ethyl-3-（dimethylamino）acrylate（3cl）, and provide a new possible way to the synthesis of Quinolones.

1,3-Dipolar Addition of Methyl α-Diazoacetoacetate to Enamines: A New Synthetic Route to 5-Amino-4,5-dihydrofurans

The reaction of methyl α-diazoacetoacetate with enamines catalyzed by dirhodium and copper complexes un-derwent formal 1,3-dipolar addition to give 5-amino-4,5-dihydrofurans in moderate yields. The reaction was sug-gested to proceed via a nucleophilic addition of enamines to metal-carbenes and a subsequent intramolecular cycli-zation of the resulting zwitterionic intermediates.

Base-catalyzed Formation of Enamines from β,β-Dicyanostyrene Derivatives with N-Bromosaccharin

A new method for the synthesis of functional enamines from β,β-dicyanostyrene derivatives and N-bromosaccharin（NBSA） was developed. In the presence of Na2CO3, the the reaction of β,β-dicyanostyrene derivatives with NBSA can generate the corresponding enamines smoothly in a mixed solvent of dichloromethane and N,N-dimethylformamide（DMF）（volume ratio 1：1） at 50 ℃. The reaction of 14 kinds of β,β-dicyanostyrene derivatives with NBSA was investigated. Screened olefins afforded the corresponding enamines in good to excellent yields（up to 94%）, indicating that the method has a wide adaptability for the substrate. The catalyst used is inexpen- sive and stable for storage. The amino groups of all products in their structures are on the a-position of products, revealing the reaction has an excellent regioselectivity. The possible pathway involving aminobromination of β,βdicyanostyrene derivative with NBSA first and then elimination of HBr process in one pot has been proposed. The structures of all products were confirmed by ^1H NMR, ^13C NMR and HRMS analysis.

Asymmetric catalytic hydrogenation of imines and enamines in natural product synthesis

Asymmetric catalytic hydrogenations of imines and enamines with chiral transition-metal complexes bearing chiral ligands are among the most green and powerful approaches for the elaboration of chiral amine structures in organic synthesis.This review focuses on recent applications of asymmetric hydrogenations of imine and enamine substrates in the total syntheses of natural products.These applications include diverse processes involving asymmetric transfer hydrogenation(ATH)and asymmetric hydrogenation(AH)to form key chiral amine motifs in natural products with good efficiency and high-level enantiocontrol.

Reactions of enamines with fluorinated acyl chlorides----Synthesis of fluorinated 1,3-diketones and 1,3-keto-aldehydes

The reactions of enamines (1a–b, 4, 6) with fluorinated acyl chlorides (2a–d ) produced fluorinated 1,3-diketones (3a–f) and 1,3-keto-aldehydes (7a–c) in good yields as well as byproducts fluorinated acylamides (5a–c). It is proposed that the reactions involve nucleophilic attack by the C-atom and/or N-atom of the enamines on acyl carbon of the fluorinated acyl chlorides.

Formation of Pyrrolidin-1-ylcyclopentadienes via Cyclization of Alkyl 2-Dimethoxyacetyl-and 2-Ethoxalyl-4-oxopentanoates

The cyclizations of alkyl 2-dimethoxyacetyl and 2-ethoxalyl-4-oxopentanoates were only effected by means of pyrrolidine with the formation of appropriately substituted 1-pyrrolidin-1-ylcyclopentadienes.

Synthesis of 4'-Methoxy Flavone

Synthesis of 4'-methoxyflavone, first by the reaction of 4 - methoxy acetophenone enamine with heptanedioyl chloride, then by dehydrogenation, is described.

Crystal Structure of 1-Phenyl-1,3-butandione Benzidine Diketoimine

1-Phenyl-1,3-butandione benzidine diketoimine 2a （C32H28N2O2, Mr = 472.56） was synthesized in high yield by the reaction of 1-phenyl-1,3-butandione with benzidine in absolute ethanol, and determined by X-ray structure analysis. It crystallizes in the orthorhombic system, space group P21/c with a = 7.9839（16）, b = 12.910（3）, c = 12.358（3）A, α = 90.00, β= 93.71（3）,γ = 90.00°, V = 1271.1（4） A3, Z = 2, Dc = 1.235 g/cm^3,/1 = 0.077 mm^-1, F（000） = 500, the final R = 0.0717 and wR = 0.1187. It presents a linear centrosymmetric framework constituted by a linkage of benzidine as a bridge and two terminal 1-phenyl-1,3-butanedione moieties.

Characterizing some gossypol and gossypolone Schiff's bases by studying their fragmentation patterns with electrospray ionization tandem mass spectra

To investigate the structural form of gossypol and gossypolone Schiff＇s bases, seven relevant Schiff＇s bases were synthesized and the electrospray ionization-tandem mass spectrometry （ESI-MS/MS） with low-energy collision-induced dissociation was used to analyze their fragmentations. A common fragmentation pathway with the loss of RNH2 from those schiff＇s bases quasi-molecular ions was observed and proposed on the basis of their MS/MS spectra data. This common pathway indicated that those Schiff＇s bases existed mainly as the enamine form not the imine form previously showed in most reports.

Bio-inspired Small Molecular Catalysis

What is the most favorite and original chemistry developed in your researchgroup?I hope it's always the next one.How do you get into this specific field?Could you please share some experiences with ourreaders?Nature provides many astonishing catalytic machineries for building up molecular complexity and harnessing energy in the most efficient ways.Nature's recipe for catalysis serves as a starting point to develop new catalyst for synthetic and energy chemistry.

Visible Light Promoted β-C-H Alkylation of β-Ketocarbonyls via a β-Enaminyl Radical Intermediate

A 5πe carbonyl activation mode is reported on the basis of photo-induced single-electron-transfer （SET） oxidation of a secondary enamine. The resultant β-enaminyl radical intermediate was trapped by a wide range of Michael acceptors, producing β-alkylation products of β-ketocarbonyls in a highly efficient manner,

Bifunctional catalysis of Morita-Baylis-Hillman (MBH) reaction with chiral primary-tertiary diamine: A non-typical MBH catalytic pathway

A simple primary-tertiary diamine has been explored as a novel catalyst for the Morita-Baylis-Hillman reaction of MVK and aryl aldehydes, and moderate to good chemical yields were obtained. Detailed mechanism study indicated that the diamine acted as a bifunctional cooperation catalyst via a bicyclic enamino-quaternary ammonium intermediate.

Multicomponent Reactions for Diverse Synthesis of N-Substituted and NH 1,4-Dihydropyridines

The multicomponent reactions of aldehydes,electron deficient alkynes and amines have been successfully per-formed to yield a number of symmetrical 2,6-unsubstituted 1,4-dihydropyridines(1,4-DHPs).This method has been found generally applicable for the synthesis of both N-substituted and N-unsubstituted 1,4-DHPs by employing secondary amine to activate the alkyne component via enaminoester intermediates.The present method runs through an enamine type activation,which is different from the known approach employing AcOH as solvent.