Electronic structure and absorption spectra of acetylacetone and its analogs

The molecules of acetylacetone, benzoylacetone, dibenzoylmethane, and thiodibenzoylmethane have been calculated by the simple MO LCAO method and their absorption spectra recorded. The chelation of acetylacetone with a hydrogen atom does not affect the energy of the first allowed transition ¹A₁-¹B₁. Calculations correctly predict the change in the energy for this transition in the -diketone series: acetylacetone > benzoylacetone > dibenzoylmethane > thiodibenzoylmethane; the intensity reaches a maximum value for dibenzoylmethane and dropping sharply for thiodibenzoylmethane. The secondary absorption bands for benzoylacetone and dibenzoylmethane are examined experimentally and interpreted theoretically.     

A novel access to pyrido[4,3-d]pyrimidine scaffold via Staudinger/intramolecular aza-Wittig reaction of 5-acyl-4-(β-azidoalkyl)-1,2,3,4-tetrahydropyrimidin-2-ones

A general four-step approach to 1,2,3,7,8,8a-hexahydropyrido[4,3-d]pyrimidin-2-ones via Staudinger/intramolecular aza-Wittig reaction of 5-acyl-4-(β-azidoalkyl)-1,2,3,4-tetrahydropyrimidin-2-ones promoted by PPh₃ was developed. Synthesis of the starting pyrimidinones included preparation of 3-azidoaldehydes by the addition of hydrazoic acid to α,β-unsaturated aldehydes, transformation of 3-azidoaldehydes into N-[(3-azido-1-tosyl)alkyl]ureas followed by the reaction with enolates of dibenzoylmethane, benzoylacetone, acetylacetone, or ethyl 2,4-dioxo-4-phenylbutanoate and dehydration of the resulting products under acidic conditions.     

Nano-sized, ternary oxovanadium(IV) complexes containing electron-rich oxygen-based ligands

Some mononuclear mixed-carboxylato ??-diketonato oxovanadium(IV) complexes of the general formula [VO(??-dike)(RCOO)] (where H??-dike?=?acetylacetone; benzoylacetone or dibenzoylmethane, R?=?C₁₅H₃₁ or C₁₇H₃₅) have been synthesized from VO(acac)₂ by stepwise substitutions of acetylacetonate ion with straight chain fatty acids (RCOOH) and ??-diketones in p-xylene under reflux. The substituted acetylacetone could be fractionated out with p-xylene as an azeotrope. These were characterized by elemental analyses, molecular weight determinations, spectral (electronic, infrared, ¹H NMR, EPR and powder XRD) studies, magnetic susceptibility measurements and cyclic voltammetry. Molar conductance values indicated the complexes to be non-electrolytes in nitrobenzene. Bidentate chelating nature of ??-diketonate and carboxylate ligands in the complexes was established by infrared and NMR spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. The EPR spectra illustrated coupling of the unpaired electron with ⁵¹V nucleus (I?=?7/2). Cyclic voltammograms of all the complexes displayed one-step oxidation processes. The oxidation peak potential corresponded to the quasireversible one-electron oxidation process of the metal center, yielding V(V) species. Powder XRD and transmission electron microscopy (TEM) studies indicated the particles of these were lying in the nano-size range. The synthesized complexes are a new type of mixed-ligand complexes in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes.     

Optisch aktive O-silyl-β-dicarbonylverbindungen : II. Reaktionen

Nucleophilic substitution reactions at the silicon atom of optically active O-silyl-β-dicarbonyl compounds are investigated. The solvolyses with water or methanol probably lead to inversion of configuration, which is masked in most cases by racemisation. Reactions with acid chlorides in all cases result in inversion of configuration. The silyl derivatives of ethyl acetoacetate or ethyl butyroacetate and LiAlH₄ react with inversion, but those of acetylacetone, diethyl malonate, ethyl benzoacetate or benzoylacetone with retention of configuration at the silicon atom.     

Synthesis,rearrangements, and fragmentation of ketene mercaptals derived from ketones or β-diketones and carbon disulphide

By use of the ion pair extraction technique, tetrabutylammonium salts of acetylacetone, benzoylacetone, and dibenzoylmethane were reacted with carbon disulphide to give salts of dithioacids. Alkylation gave dithioesters and ketene mercaptals. A simple procedure for the preparation of 2-diacylmethylene-1,3-dithietanes

was found. Cyclisation reactions of some acetylacetone derivatives gave a 1,3-dithiolane, a mercaptothiophene, and a [2.3-b] thienothiophene. Allylic ketene mercaptals derived from acetone, cyclohexanone, acetylacetone, benzoylacetone, and dibenzoylmethane rearranged to α-allyl-dithioesters. Inversion of the migrating allyl group was observed when the ketene mercaptal had a vinylic hydrogen; otherwise retention was found. 3-[(Crotylthio-, methylthio-)methylene] acetylacetone underwent decomposition at 170° to methyl, 1-methyl-allyl sulphide and the “desaurin”: 2,4-bis-(diacetyl-methylene)-1, 3-dithietane. By-products in syntheses of the dithioesters and ketene mercaptals included trithiocarbonates, alkylated β-diketones, and compounds formed by reactions of the solvent (CH₂Cl₂) with β-diketones or their carbon disulphide adducts (1,3-di-thietanes).     

Synthesis,characterization and catalytic studies of iron(III), cobalt(II), nickel(II) and copper(II) complexes containing triphenylphosphine and β-diketones

A series of new β-diketonato complexes have been synthesized from the reactions of iron(III), cobalt(II), nickel(II) and copper(II) Ph₃P complexes with β-diketones (acetylacetone, benzoylacetone and dibenzoylmethane). All the complexes have been characterized by elemental analyses, spectral studies (i.r., electronic., magnetic., e.p.r., ¹H-n.m.r.) and cyclic voltammetry. The new complexes have been used as catalysts for aromatic coupling and oxidation reactions. Higher catalytic activity has been observed for the nickel(II) complexes compared to the other complexes.     

Xanthate anions in salts of biscyclopentadienylzirconium(IV) chelates

A series of [Cp ₂ZrL]⁺[ROCS₂]^? complexes whereL is the conjugate base of acetylacetone, benzoylacetone or 8-hydroxyquinoline andR=Me,Et ori-Pr have been synthesised in aqueous medium by the reaction of [Cp ₂ZrL]⁺Cl^? withROCS ₂ ^? K⁺. Various physico-chemical studies carried out for these complexes indicate that all the complexes are 1:1 electrolytes in which the ligandL is bidentate, consequently there is a tetrahedral coordination about the zirconium atom.     

Heterocyclic rearrangements. Synthesis of 1,2,4-oxadiazolo[2,3-a]pyrimidinium systems and their ring opening into pyrimidine N-oxides

The reaction of 3-amino-5-phenyl-(methyl-)-1,2,4-oxadiazole with acetylacetone or benzoylacetone in the presence of perchloric acid has been studied. Synthesis of 1,2,4-oxadiazolo[2,3-α]pyrimidinium perchlorates and their ring opening reaction into aminopyrimidine N-oxides is reported.     

Aliphatic acid dihydrazide derivatives of dicyclopentadienylzirconium(IV) dichloride and their reactions with β-diketones. Formation of cyclic compounds

The reactions of dicyclopentadienylzirconium(IV) dichloride with bidentate aliphatic acid dihydrazide (LH₂) derived from oxalic, succinic, and adipic acids (metal to ligand molar ratios 1 : 1 and 1 : 2, respectively) in anhydrous tetrahydrofuran in the presence of base led to the formation of the [Cp₂Zr(L)] and [CpZr(LH)₂Cl] complexes. The complexes were characterized by elemental analyses, electrical conductance, magnetic measurements and spectroscopic studies. These ligands appear to behave as bidentate chelate agents. All the complexes contain terminal amino or terminal hydrazinc nitrogen atoms with an unshared electron pair, enabling nucleophilic condensations. Therefore, the reactions of these complexes with β-diketones (acetylacetone, benzoylacetone, dibenzoylmethane, thenoyltrifluoroacetone) in the presence of glacial acetic acid have been studied viz., ring closure and formation of macrocyclic ligand (mac) complexes. Two types of cyclic products viz., [Cp₂Zr(mac)] and [CpZr(Mac)Cl] were isolated. The spectral studies of these cyclic products are reported.     

Synthesis of 6-acylpyrido[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine derivatives from 5-acetyl-4-aminopyrimidine hydrochlorides

Reaction of 2,6-disubstituted 5-acetyl-4-aminopyrimidine hydrochlorides with acetylacetone or benzoylacetone afforded new substituted 6-acylpyrido[2,3-d]pyrimidines. The reaction of these hydrochlorides with ethyl acetoacetate also proceeds according to the classical version of the Friedländer condensation to form the corresponding pyrido[2,3-d]pyrimidine-6-carboxylic acid esters.     

Reactions of pentafluorophenyltrimethylsilane and cyanomethyltrimethylsilane with carbonyl compounds catalyzed by cyanide anions

Treatment of pentafluorophenyltrimethylsilane (I) and cyanomethyltrimethylsilane (II) with enolizable ketones in the presence of a catalytic amount of potassium cyanide-18-crown-6 complex gave the corresponding trimethylsilyl enol ethers. The same dehydrogenative silylation of acetylacetone and benzoylacetone with silane I was extended to the preparation of 2,4-bis(trimethylsiloxy)-1,3-pentadiene and 1-phenyl-1,3 -bis(trimethylsiloxy)-1,3-butadiene, respectively. The dehydrogenative silylation of acetylacetone and benzoylacetone with dimethylbis(pentafluorophenyl)silane under the same conditions affords novel heterocyles 5-methylene-2,6-dioxa-1-silacylohex-3-enes. In the reaction studied the silylating ability of the silanes increases in the order Me₃SiCN ? Me₂Si(CN)₂ < Me₃SiCH₂CN < Me₃SiC₆F₅ ? Me₂Si(C₆F₅)₂. On the other hand, potassium cyanide-18-crown-6 complex catalyzed the addition of silane I or II to a carbonyl group of non-enolizable compounds such as benzaldehyde, crotonaldehyde, and methyl(triethylgermyl)ketene.     

Generation of the m/z 69 ion C3HO 2 + by electron ionization of some aryl-substituted β-diketones

The m/z 69 ion, prominent in the electron ionization (EI) mass spectra of some aryl-substituted β-diketones, has been shown to have the composition C₃HO ₂ ⁺ by accurate mass determination, identification of its precursor ions, and of its decomposition product ions. In contrast, it is a minor ion in the EI mass spectrum of acetylacetone, which lacks an aryl substituent but otherwise has the correct structural features to produce this ion. Until recently, this species appears to have attracted little experimental or theoretical attention. The proposed structure, OCCHCO⁺, is supported by its collisionally activated dissociation to m/z 41, HCCO⁺, and by ab initio quantum chemical calculations. Available thermochemical data predict the thermo-chemistry to be unfavorable for its production in the EI mass spectrum of benzoylacetone, but favorable in the case of acetylacetone, contrary to the experimental observations. Even in the case of aryl-substituted β-diketones also containing a CF₃ substituent (isobaric with OCCHCO) the m/z 69 ion is predominantly OCCHCO⁺. Since this ion is an inherently stable species it is evident that its ready formation requires precursors having suitable structural features; a mechanistic pathway to its formation from aryl-substituted β-diketones is suggested.     

Optisch aktive O-silyl-β-dicarbonylverbindungen : I.Darstellung und struktur

The reaction of optically active methylphenyl-α-naphthylchlorosilane with acetylacetone, ethyl acetoacetate, diethyl malonate, ethyl butyroacetate, ethyl benzo-acetate, and benzoylacetone in the presence of sodium or triethylamine leads to the formation of optically active O-silyl-β-dicarbonyl compounds(I)–(VI) with inversion of configuration. The compounds (I)–(VI) are obtained as cis-trans mixtures, the cis-trans-ratio depending on the preparative conditions. At room temperature, the cis-isomer of (I) exhibits rapid intramolecular silyl group migration from one O-atom to the other with retention of configuration. The trans-isomers of (I)–(VI) are also able to exchange silyl groups, but by intermolecular transfer and obviously with inversion of configuration. On standing for a longer time or on heating to ca. 190° a cis-trans-rearrangement, which leads to racemisation, can be observed for all compounds.     

Ruthenium(III) mono (2,2′-bipyridine) complexes containing O,O-donor ligands and their oxidation properties for organic compounds

The new complexes [Ru^IIIbpyL₂](PF₆) and [Ru^IIIbpyLCl₂] [bpy = 2,2-bipyridine; HL = acetylacetone, trifluoroacetylacetone, benzoylacetone (Hbac), tropolone or maltol; HL = Hbac or dibenzoylmethane) have been prepared and characterized by spectroscopy. Their redox behaviour was studied by cyclic voltammetry. They effectively catalyze the oxidation of alcohols, alkanes and primary aromatic amines.     

Enolic Schiff-base aluminum complexes and their application in lactide polymerization

A series of NNOO-tetradentate enolic Schiff-base ligands were prepared where ligand L₁ = bis(benzoylacetone)propane-1,2-diimine, L₂ = bis(acetylacetone)-propane-1,2-diimine, L₃ = bis-(acetylacetone)cyclohexane-1,2-diimine. Their further reaction with aluminum tris(ethyl) formed complexes LAlEt (1a, 2a and 3a). The solid structure of complexes 1a, 2a and 3a confirmed by X-ray single crystal analysis manifested that these complexes were all monomeric and five-coordinated with an aluminum atom in the center. The configurations of these complexes varied from trigonal bipyramidal geometry (tbp) to square pyramidal geometry (sqp) due to their different auxiliary ligand architectures. ¹H NMR spectra indicated that all these complexes retained their configuration in solution states. Their catalytic properties to polymerize racemic-lactide (rac-LA) in the presence of 2-propanol were also studied. The diimine bridging parts as well as the diketone segment substituents had very close relationship with their performance upon the polymerization process. All these complexes gave moderately isotactic polylactides with controlled molecular weight and very narrow molecular weight distributions.     

LAMMA mass spectra of β-diketone,bis(benzoylacetone)ethylenediimine and bis(salicylidene)ethylenediimine complexes of some transition metals

Complexes of 2,4-pentanedione (acetylacetone, acac), [Cu(acac)₂], [VO(acac)₂] and [CO(acac)₃], and the chromium(III) derivative of 3-methyl-2,4-pentanedione (methylacetylacetone, meac), [Cr(meac)₃], the ligands bis(benzoylacetone)ethylenediimine and bis(salicylidene)ethylenediimine, and their cobalt(II), nickel(II) and copper(II) chelates were analysed by laser desorption mass spectrometry (LAMMA) and compared to electron impact (EI) results. The positive ion LAMMA spectra generally reveal mostly small fragments, although metal cationization peaks are seen for most complexes. Negative ion LAMMA produce carbon clusters and some structurally important fragments.     

Cationic Ruthenium(II) Carbonyl Complexes with Nitrile Ligands

Stable cationic complexes of the type [RuCO(PPh₃)₂(L)(RCN)]⁺[ClO₄]^? derived from acetonitrile and acrylonitrile have been synthesized. The bidentate ligands (LH) used are acetylacetone, benzoylacetone, dibenzoylmethane, trifluorothenoyl acetone and 8-hydroxyquinoline. The complexes have been characterized by elemental analysis, IR, conductivity, ¹H and ³¹P NMR and ESCA studies, and possible stereochemistry has been established.     

Nitriles in organic synthesis: The reaction of trichloroacetonitrile with active methylene reagents

The reaction of trichloroacetonitrile with active methylene reagents such as acetylacetone, benzoylacetone, cyanoacetamide and cyanoacethydrazide is reported. A new simple route for the synthesis of polysubstituted phenols, pyrazoles and pyrroles is also described.

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Nitrile bei organischen Synthesen: Die Reaktion von Trichloracetonitril mit aktiven Methylen-Reagentien

Zusammenfassung Es wird über die Reaktionen von Trichloracetonitril mit aktiven Methylen-Reagentien wie Acetylaceton, Benzoylaceton, Cyanacetamid und Cyanacethydrazid berichtet. Ein neuer einfacher Weg für die Synthese polysubstituierter Phenole, Pyrazole und Pyrrole wird beschrieben.

     

Isolation of dithiocarbamate anions as salts of biscyclopentadienyl titanium(IV) chelates

A series of [Cp₂TiL]⁺[RR′NCS₂]^? complexes, where L is the conjugate base of acetylacetone, benzoylacetone or 8-hydroxyquinoline and R = CH₃, R′ = C₆H₅CH₂; R = C₂H₅, R′ = C₆H₄CH₃; R = H, R′ = C₅H₉; RR′ = C₆H₁₂, have been synthesised in aqueous medium by the reaction of [Cp₂TiL]⁺Cl^? with RR′NCS^?₂Na⁺. Conductivity measurements in nitrobenzene solution indicate that these complexes are electrolytes. Both the IR and NMR studies demonstrate that the ligand L is chelating in all these complexes. Consequently, tetrahedral coordination about the titanium atom is proposed. In addition to these studies, elemental analyses and magnetic susceptibility have been carried out for these complexes.     

Synergistic mechanisms of β-diketone derivatives and zinc-calcium soaps in PVC stabilisation

It has been possible to explain the mechanisms of stabilisation and of the synergistic effects of the β-diketone derivatives claimed in a patent as new stabilisers for improving the efficiency of those recipes based upon zinc and calcium soaps in the prevention of the initial discoloration of poly(vinyl chloride).Using chlorohexene as a model compound for allylic chloride structures and benzoylacetone as a model compound for enolised β-diketone derivatives, it has been shown that the benzoylacetone can substitute allylic chlorine atoms through a C-alkylation reaction which takes place only in the presence of ZnCl₂ as catalyst. This reaction drastically changes the percentage of the enol and causes the appearance of two bands at 1720 cm^?1 and 1680 cm^?1 in the infra-red spectrum due to the ketonic structures During the processing of the PVC on a rolling mill at 180°C in the presence of zinc and calcium stearates and benzoylacetone there is grafting of the ketone derivative through a C-alkylation reaction. There is a closed parallelism between the influence of the benzoylacetone on the dehydrochlorination of the chlorohexene and on the accumulation of chloride ions in the polymer matrix in the presence of zinc and calcium stearate. The synergistic effect of the benzoylacetone in the prevention of the initial discoloration is related to the substitution reaction through a C-alkylation which takes place only in the presence of zinc stearate which generates ZnCl₂ which, in turn, acts as a catalyst for both the C-alkylation and dehydrochlorination.