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The catalyzed luminol chemiluminescent reaction has received a great amount of attention because of its high sensitivity and low background signal which make the reaction an attractive analytical chemistry tool. The present study, introduces the beneficial catalytic effects of dinuclear Cu(II) complex [Cu 2L2(TAE)]X2, where TAE = tetraacetylethane; L = N,N'-dibenzylethylenediamine and X = ClO4 on the luminol chemiluminescent reaction as a novel probe for the determination of glutathione (GSH) and L-cysteine (CySH) in human serum and urine. The [Cu2L 2(TAE)]X2 has exhibited highly efficient catalytic activity of luminol CL as an artificial peroxidase model at pH as low as 7.5 in water in the presence of H2O2×GSH and CySH can induce a sharp decrease in CL intensity from the [Cu2L 2(TAE)]X2-catalyzed luminol system. Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentrations of GSH and CySH in the range of 1.0 × 10-7-1.0 × 10-4 M, with detection limits (S/N = 3) of 2.7 × 10-8 and 6.8 × 10-8 M and RSD 4.2% (n = 7) for GSH and CySH, respectively.

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The reactions of zinc(II) with three 1,3-diketones have been investigated in aqueous solution at 25 deg C and an ionic strength of 0.5 mol dm-3 NaClO4.The catalytic effect of cacodylic acid on the reactions of zinc(II) with pentane-2,4-dione has been demonstrated.In addition, the effect of cacodylic acid on the hydrolysis of the nickel(II) and copper(II) triglycine complexes has been investigated.

[Figure not available: see fulltext.] A multicomponent reaction of arylglyoxal hydrates, acetylacetone or acetoacetic ester, aniline or its 3(4)-substituted analogs in 1:1:2 ratio occurred upon stirring in methanol, giving 4-arylamino-5-hydroxypyrroline derivatives containing 4,5-dihydroxypyrrolines as impurities.

The adsorption of isopropyl alcohol and acetone on zinc oxide was studied by an infrared technique which revealed that isopropyl alcohol is dissociatively adsorbed at room temperature to form zinc alcoholate and hydroxyl group on the surface, while the adsorption of acetone takes place in its enolic form.When adsorbed isopropyl alcohol was heated to 363 K, the zinc alcoholate species changed gradually to acetone adsorbed in its enolic form, which further desorbed at higher temperatures as acetone, being replaced by the attacking isopropyl alcohol.The behaviour of the adsorbed species during decomposition of isopropyl alcohol on zinc oxide was studied in more detail, leading to the overall reaction mechanism described by eqn (V).

The high temperature thermal rearrangement of the title dienol ester is reported.Its reactions entail a acyl shift followed by intramolecular Diels-Alder cycloaddition of the resulting β-diketone.

Biscyclometalated iridium(III) complexes with an ancillary acetylacetone ligand, Ir(L)2(acac), (L = 2-(benzo[b]thiophen-2-yl)pyridine (btp), 1-phenylisoquinoline (piq), 2-phenylbenzothiazole (bt), 2-phenylpyridine (ppy), acac = deprotonated acetylacetone), demonstrate spectroscopic changes in their UV-Vis absorption and luminescent emission under acidic conditions. Such changes were found to be the same as those observed when certain mercury salts exist in the systems. Because some iridium(III) complexes have sulfur-containing ligands (i.e., btp and bt), a question was then raised as for whether or not the spectroscopic changes are associated with the specific affinity of Hg 2+ to the sulfur atom. Extensive studies performed in this work unambiguously proved that the observed spectroscopic changes were solely the results of the acid induced departure of acac and the follow-up coordination of solvent acetonitrile to the iridium(III) center and that the generally anticipated Hg2+-S affinity and its effect on the photophysical properties of iridium(III) luminophores did not play a role. The Royal Society of Chemistry 2012.

Acetylacetone (2,4-pentanedione, 1) is a molecule whose tautomeric forms are in dynamic equilibrium. Concentrated salt solutions in nonaqueous solvents exert a remarkable influence on the keto-enol ratio of this β-diketone. The keto content of 1 increases from 5% in pure diethyl ether to 84.5% in a 4.14 M lithium perchlorate-diethyl ether (LPDE) solution, a nearly 17-fold increase. The equilibrium expression, K = [keto]/[enol] = kf/kr, exhibits a linear dependence on [LiCIO4], with the formal order of participation of lithium ion in the equilibrium being 1.0. A kinetic analysis reveals that kf is independent of LPDE concentration, whereas kr displays an inverse dependence on salt concentration, indicating preferential coordination of the keto tautomer with Li+. Although 1 exits as the enol in water only to the extent of 16%, the addition of lithium perchlorate further reduces this figure. In an aqueous 4.02 M LiCIO4 solution, acetylacetone enol accounts for only 4.6% of the total amount of 2,4-pentanedione present. It has also been found that acetylacetone itself is an excellent solvent for LiCIO4 as well as for NaCIO4 with solutions containing up to 7.5 M LiCIO4 attainable. The enol content of 1 decreases dramatically from 81% to 7.4% on going from the neat liquid to a solution of 6.39 M LiCIO4 in acetylacetone.

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The keto-enol tautomeric equilibrium for pentane-2,4-diode has been explored in several ionic liquids and these data have been used to give an indication of their polarities in the ground state. The results suggest higher apparent polarities than have been previously indicated by the use of solvatochromatic dyes.

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The activity of the catalytic system based on palladium bisacetylacetonate and phenylphosphine in hydrogenation catalysis was studied.

Rates of hydrolysis of acetylacetone complexes of oxovanadium(IV) and beryllium(II) have been measured using a stopped-flow technique. In aqueous solution at 25° VO(acac)2 decomposes in two steps with the second ring being removed 150 times slower than the first. Both rings were removed from Be(acac)2 at the same rate. The hydrogen ion dependence of the rates indicates that the special chelate mechanism, in which H+ traps a half-bonded intermediate, is a general one for hydrolysis of acetylacetonates. The behavior of hydrolysis rates upon addition of nucleophilic reagents is consistent with the interpretation that direct nucleophilic attack on the metal ion does not occur. The vanadyl complex, however, can add a sixth group which influences the rate of dissociation.

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Geotrichum sp. WF9101 isolated from a poly(vinyl alcohol)-degrading mixed culture could utilized vinyl alcohol oligomers, but not the polymers. This strain is proposed to have utilized degradation products of poly(vinyl alcohol) in the mixed culture. Biodegradation of vinyl alcohol oligomers by this strain was discussed using 2,4-pentanediol as a model substrate.

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Rates of some substitution reactions of nickel(II) acetylacetonato complexes in aqueous solution at 25° have been measured using a stopped-flow technique. Hydrolysis of the bis complex occurs in two steps, the second about 200 times slower than the first. Rates of hydrolysis depend on (H+), suggesting that hydrogen ion traps a half-bonded chelate, causing the reaction to go to completion. When nucleophilic reagents are added, rates of hydrolysis are increased. This effect is attributed to rapid replacement of a water molecule in the first coordination sphere of the nickel by the anion prior to hydrolysis, and not to a direct nucleophilic attack on the metal. The results are rather similar to those found earlier for Pd(acac)2, with which they are compared.

In depth headspace analysis of the slow degradation of β-alkylthioalkanones in ambient air led to the discovery of a novel δ-cleavage pathway, by which β-mercaptoketones are released. Since β-mercaptoketones are potent natural aroma compounds occurring in many fruits, herbs and flowers, the discovery of an enzyme-independent molecular precursor for this class of high-impact molecules is of practical importance. Moreover, the formation of β-diketones and aldehydes by concomitant oxidation at the α-sulfur-position enhances the versatility of this class of aroma precursors. A mechanistic model is proposed which suggests that the oxidative degradation occurs through a novel Pummerer-type rearrangement of initially formed persulfoxides.

The hydrogen/halogen exchange of phosphines has been exploited to establish a truly useable substrate scope and straightforward methodology for the formation of cyclopolyphosphines. Starting from a single dichlorophosphine, a sacrificial proton "donor phosphine"makes the rapid, mild synthesis of cyclopolyphosphines possible: reactions are complete within 10 min at room temperature. Novel (aryl)cyclopentaphosphines (ArP)5 have been formed in good conversion, with the crystal structures presented. The use of catalytic quantities of iron(III) acetylacetonate provides significant improvements in conversion in the context of diphosphine (Ar2P)2 and alkyl-substituted cyclotetra- or cyclopentaphosphine ((AlkylP)n, where n = 4 or 5) formation. Both iron-free and iron-mediated reactions show high levels of selectivity for one specific ring size. Finally, investigations into the reactivity of Fe(acac)3 suggest that the iron species is acting as a sink for the hydrochloric acid byproduct of the reaction.

Hydration of alkynes to ketones is one of the most atom economical and universal methods for the synthesis of carbonyl compounds. However, the basic reaction usually requires organic ligand catalysts or harsh reaction conditions to insert oxygen into the C≡C bond. Here, we report an inorganic ligand supported cobalt (III) catalyst, (NH4)3[CoMo6O18(OH)6], which is supported by a central cobalt (III) mononucleus and a ring-shaped pure inorganic ligand composed of six MoVIO6 octahedrons to avoid the disadvantages of expensive and unrecyclable organic ligand catalysts or noble metal catalysts. Under mild conditions, the cobalt (III) catalyst can be used for the hydration of alkynes to ketones. The catalyst is non-toxic, green, and environment friendly. The catalyst can be recycled at least six times with high activity. According to control experiments, a reasonable mechanism is provided.

4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.

A compound according to Formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, wherein X1 and X2 are each independently 18F or 19F; R1 and R2 are each independently alkyl, amine, perfluoroalkyl, alkenyl, alkynyl, aryl, or aralkenyl; and R3 is H, halo, alkyl, alkyl ester, alkenyl, alkynyl, aryl, or aralkenyl; or wherein: R1 and R3 or R2 and R3 join to form a 6-membered cycloalkyl or heterocyclyl; or R1 and R3, R2 and R3, or R1, R2, and R3 join to form a substituted or unsubstituted polycyclic ring, wherein the polycyclic ring comprises fused cycloalkyl, heterocycloalkyl, aryl, or heteroaryl rings.

A visible light mediated De Mayo reaction between 1,3-diketones and styrenes following a [2+2] cycloaddition pathway via a photosensitization mechanism gives access to 1,5-diketones. The reaction has been applied to substituted styrenes and aryl- and alkyl-substituted ketones. Moreover, the method converts β-ketoesters, β-amido esters, and β-cyano ketones. Seven membered rings, a frequent structural motif of natural products, are also accessible using this methodology.

Trimethylchlorosilane was used as chlorine source for the α-chlorination of 1,3-dicarbonyl compounds with phenyliodonium diacetate as oxidant at room temperature. The reaction allows the selective synthesis of α-monochlorinated products from different kinds of 1,3-dicarbonyl compounds in good yield. The potential possibility of this conversion for bromination has also been investigated.

A routine thioketal protecting group reacts rapidly and selectively with singlet oxygen to reveal ketone products in good (aryl 1,3-dithiolane) to excellent (aryl 1,3-oxathiolane) yields. Arylthiolanes are stable to biologically relevant reactive oxygen species and can be used as a light-activated gating mechanism for activating fluorescent sensors or small molecule prodrugs.

C-Allyl cleavage has been developed using the inexpensive and mild reagent iodine in dimethylsulfoxide. A variety of compounds with active methylene groups were C-deallylated using this reagent. This method is efficient and operationally simple in comparison to the methods using transition-metal complexes. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.

The present invention relates to a crosslinkable composition comprising at least one crosslinkable component crosslinkable by a latent base crosslinking catalyst comprising a substituted carbonate salt according to formula 1 wherein X+ represents a cation and wherein R is hydrogen, alkyl, aryl or aralkyl group, and wherein the crosslinkable composition comprises 0.1-10 wt %, preferably 0.1-5, more preferably 0.2-3 and most preferably 0.5-1.5 wt % water (relative to total weight of the crosslinkable composition). The invention further relates to a coating composition comprising the crosslinkable composition according to the invention, a novel catalyst composition and to the use of said catalyst composition according to the invention as a latent base crosslinking catalyst in coating compositions, preferably in RMA crosslinkable compositions.

2-Pyrones, such as triacetic acid lactone, are a promising class of biorenewable platform chemicals that provide access to an array of chemical products and intermediates. We illustrate through the combination of results from experimental studies and first-principle density functional theory calculations that key structural features dictate the mechanisms underlying ring-opening and decarboxylation of 2-pyrones, including the degree of ring saturation, the presence of C=C bonds at the C4=C5 or C5=C6 positions within the ring, as well as the presence of a β-keto group at the C4 position. Our results demonstrate that 2-pyrones undergo a range of reactions unique to their structure, such as retro-Diels-Alder reactions and nucleophilic addition of water. In addition, the reactivity of 2-pyrones and the final products formed is shown to depend on the solvent used and the acidity of the reaction environment. The mechanistic insights obtained here provide guidance for the selective conversion of 2-pyrones to targeted chemicals.

A direct β-acyloxylation of enamine compounds has been achieved by using iodosobenzene (PhIO) as an oxidant to realize the intermolecular oxidative C(sp2)-O bond formation between enamines and various carboxylic acids, including N-protected amino acids. The transformation tolerates a wide range of functional groups and furnishes a variety of β-acyloxy enamines that can be conveniently converted to oxazole compounds via cyclodehydration.

A direct β-acyloxylation of enamine compounds has been achieved by using iodosobenzene (PhIO) as an oxidant to realize the intermolecular oxidative C(sp2)-O bond formation between enamines and various carboxylic acids, including N-protected amino acids. The transformation tolerates a wide range of functional groups and furnishes a variety of β-acyloxy enamines that can be conveniently converted to oxazole compounds via cyclodehydration.

Described is a method of making 2,4-diones via acid catalyzed or thermally induced ring-opening of a 4-hydroxy-6-substituted-2-pyrone to yield a 2,4-dione.

A series of optically pure β-amino ketones have been synthesized in high enantioselectivities (ee > 99%) by Rh-DuanPhos-catalyzed asymmetric hydrogenation of readily prepared β-keto enamides. Further reduction of these β-amino ketones with hydrogen and Pd/C leads to the formation of a variety of protected enantiomerically pure γ-aryl amines (ee > 99%), which are key building blocks in many bioactive molecules.

A mild, efficient, general, and green method for the regeneration of carbonyl compounds from their corresponding oximes is described. Cupric salts promoted hydrolysis of oximes was studied, and the best reaction conditions for the hydrolysis have been found. Carbonyl compounds were obtained in 85-98% yields after the treatment of oximes with 2 molar equivalent of CuCl 22H2O at reflux (around 75 C) in a mixed solvent of acetonitrile and water (4:1). In addition, cupric salt was readily recovered in an almost quantitative yield via the complete precipitation of Cu(OH) 22H2O. Georg Thieme Verlag Stuttgart · New York.

Reflux of isopropenyl acetate with an excess of AlCl3 in 1,2-dichloroethane affords 3,5-diacetyl-2,6-dimethyl-4H-pyran-4-one in 17% yield. The mild acidic cleavage of the latter (2% HCl, 20°C, 16 h) gives 3-acetyl-2,6-dimethyl-4H-pyran-4-one in 87% yield, whereas this reaction under more drastic conditions (17% HCl, reflux, 3 h) gives 2,6-dimethyl-4H-pyran-4-one in 61% yield.

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Reaction of vanadyl acetylacetonate with tert-butyl hydroperoxide (benzene, 20°C) at any molar ratio leads to the elimination of ligand and its oxidation mainly to CO2 and acetic acid. At the (acac)2VO: t-BuOOH ratio above 1:10 liberation of oxygen partially in the singlet state takes place.

The bimolecular rate constant of script k signNO3+ β-ionone (9.4 ± 2.4 × 10-12 cm3 molecule-1 s-1 was measured using the relative rate technique for the reaction of the nitrate radical (NO3

Structure-activity relationships have been investigated for inhibition of DNA-dependent protein kinase (DNA-PK) and ATM kinase by a series of pyran-2-ones, pyran-4-ones, thiopyran-4-ones, and pyridin-4-ones. A wide range of IC50 values were observed for pyranones and thiopyranones substituted at the 6-position, with the 3- and 5-positions proving intolerant to substitution. Related pyran-2-ones, pyran-4-ones, and thiopyran-4-ones showed similar IC50 values against DNA-PK, whereas the pyridin-4-one system proved, in general, ineffective at inhibiting DNA-PK. Extended libraries exploring the 6-position of 2-morpholinopyran-4-ones and 2-morpholino- thiopyrano-4-ones identified the first highly potent and selective ATM inhibitor 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one (151C; ATM; IC50 = 13 nM) and revealed constrained SARs for ATM inhibition compared with DNA-PK. One of the most potent DNA-PK inhibitors identified, 2-(4-methoxyphenyl)-6- (morpholin-4-yl)pyran-4-one (16; DNA-PK; IC50 = 220 nM) effectively sensitized HeLa cells to the topoisomerase II inhibitor etoposide in vitro.

New developments in the reduction of β,δ-diketo-sulfoxides, a reaction that affords important key intermediates for total synthesis, are described. We showed without ambiguity using NMR experiments, that the β-carbonyl group is totally enolised. This result is inconsistent with the previous hypothesis, which supposed the other tautomer (enolisation at the δ-position) as the major one. We propose a rationale to explain the side reactions occurring during the reduction of unprotected β,δ-diketo-sulfoxides and showed that judicious protection of the δ-carbonyl group gave all diastereoisomers of β-hydroxy-δ-ketosulfoxides.

The invention concerns a method for preparing a compound of formula (1) wherein: A represents naphthyl or phenyl optionally substituted; and Ar1, Ar2independently represent a saturated or aromatic carbocyclic group, optionally substituted.

Conventional and stopped-flow spectrophotometry was used to study the kinetics of ligand substitution in a number of tris β-diketone iron(III) complexes, Fe(O∩O)3, by 8-hydroxyquinoline (=HO∩N) in alcohol media (O∩O-=anion of the β-diketones pentane-2,4-dione, 2,6-dimethylheptane-3,5-dione, 2,2,6,6-tetramethylheptane-3,5-dione, 1-phenylbutane-1,3-dione, 1,3-diphenylpropane-2,3-dione, and 1-(2-thienyl)-4,4,4-trifluorobutane-1,3-dione). As shown by spectrophotometry, the solutions of complexes Fe(O∩O)3 in alcohols ROH are subject to solvolytic dissociation, leading to solvento species Fe(O∩O)2S2 and to binuclear complexes [Fe(O∩O)2(RO)]2 (S=ROH and RO-, respectively). The reaction of complexes Fe(O∩O)3 with HO∩N in alcohol media, leading to Fe(O∩N)3, is triphasic. The corresponding first-order rate constants k1, k2, and k3 are independent of the concentration of the entering ligand HO∩N and follow the order k1>k2>k3, with k1/k2≈10 and k1/k3≈102. For a given system Fe(O∩O)3/HO∩N/ROH, the size of k1, k2, and k3 correlates with the solvent polarity parameter ET(30). Rate constant k1 describes the solvolytic dissociation of the complexes Fe(O∩O)3 and rate constant k3 the solvent-initiated splitting of the binuclear complexes [Fe(O∩O)2(RO)]2. Rate constant k2 is assigned to the solvolytic dissociation of the intermediate complex Fe(O∩O)2(O∩N). Depending on the nature of the coordinated β-diketone and solvent ROH, k1 ranges from 0.04 to 2 s-1, k2 from 0.007 to 0.2 s-1, and k3 from 0.002 to 0.01 s-1 at 298 K. The mechanism of the ligand substitution processes is discussed.

The present invention relates to methods for preparing collagen, especially type I collagen. In particular, the present invention provides methods for the preparation of collagen suitable for biomedical and veterinary applications. The collagen prepared according to the present invention provides numerous desirable characteristics for applications such as implantation, transplantation, and grafting.

A method for the preparation of 1,3-diketones is disclosed wherein the method comprises the steps of:(A) mixing an alkali metal base with a hindered alcohol in an aromatic hydrocarbon solvent;(B) boiling the mixture and azeotropically distilling water formed by the reaction between the base and the alcohol, whereby a solution of a hindered alkali metal alkoxide is formed in situ in the solvent;(C) mixing an ester with the solution of the hindered alkali metal alkoxide in the aromatic hydrocarbon solvent; and then(D) adding a ketone to the mixture.

Treatment of 1,2,4,5-tetramethyl-1,4-cyclohexadiene (1) on polyethylene and in pentane with excess ozone afforded mixtures of the oxydehydrogenation product 2 and of the oxidative cleavage product 4 in ratios of 0.5:1 and 19:1, respectively. Epoxidation o

PCT No. PCT/GB94/02547 Sec. 371 Date Feb. 21, 1997 Sec. 102(e) Date Feb. 21, 1997 PCT Filed Nov. 18, 1994 PCT Pub. No. WO95/14646 PCT Pub. Date Jun. 1, 1995A method for the fluorination of 1,3-diketones and 1,3-ketoesters is disclosed.

The present invention relates to a process for the asymmetric hydrogenation of a ketonic compound and derivative. The invention relates to the use of optically active metal complexes as catalysts for the asymmetric hydrogenation of a ketonic compound and derivative. The process for the asymmetric hydrogenation of a ketonic compound and derivative is characterized in that the asymmetric hydrogenation of said compound is carried out in the presence of an effective amount of a metal complex comprising as ligand an optically active diphosphine corresponding to one of the following formulae: STR1

Microwave irradiation of ketosemicarbazones with wet antimony trichloride under solvent-free condition provides a fast, efficient and simple method for the regeneration of ketones in good yields.

2-Pentanone and 2-heptanone are available for commercial use, which will lead to their possible release into the atmosphere where they are expected to primarily react with the hydroxyl (OH) radical and contribute to the formation of photochemical air pollution in urban and regional areas. We have studied the kinetics and products of the gas-phase reactions of the OH radical with 2-pentanone and 2-heptanone at 298 ± 2 K and atmospheric pressure of air. Using a relative rate method, rate constants for the reactions of the OH radical with 2-pentanone and 2-heptanone of (4.56 ± 0.30) x 10-12 and (1.17 ± 0.11) x 10-11 cm3 molecule-1 s-1, respectively, were obtained, where the indicated errors are two least-squares standard deviations and do not include the ~10-15% uncertainties associated with the rate constant for the reference compound cyclohexane. Reaction products were analyzed by gas chromatography, in situ Fourier transform infrared spectroscopy, and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS). The products identified and quantified were (with their molar yields) as follows: from 2-pentanone, formaldehyde, 1.03 ± 0.10; acetaldehyde, 0.51 ± 0.11; propanal, 0.19 ± 0.03; 2,4-pentanedione, 0.12 ± 0.03; and molecular weight 147 organic nitrates, 0.12 ± 0.04; and from 2- heptanone, formaldehyde, 0.38 ± 0.08; acetaldehyde, ~0.05; propanal, ~0.05; butanal, 0.07 ± 0.01; pentanal, 0.09 ± 0.01; and molecular weight 175 organic nitrates, 0.18 ± 0.05. API-MS analyses also showed the formation of products of molecular weight 128 and 144 from 2-heptanone, anticipated to be C7-dicarbonyl(s) and C7-hydroxydicarbonyl(s), respectively. While 94 ± 13% of the reaction pathways of the 2-pentanone reaction are accounted for, it appears that a substantial fraction (>50%) of the initially formed alkoxy radicals from 2-heptanone undergo isomerization to form products which could not be quantified. 2-Pentanone and 2-heptanone are available for commercial use, which will lead to their possible release into the atmosphere where they are expected to primarily react with the hydroxyl (OH) radical and contribute to the formation of photochemical air pollution in urban and regional areas. We have studied the kinetics and products of the gas-phase reactions of the OH radical with 2-pentanone and 2-heptanone at 298±2 K and atmospheric pressure of air. Using a relative rate method, rate constants for the reactions of the OH radical with 2-pentanone and 2-heptanone of (4.56±0.30)×10-12 and (1.17±0.11)×10-11 cm3 molecule-1 s-1, respectively, were obtained, where the indicated errors are two least-squares standard deviations and do not include the approximately 10-15% uncertainties associated with the rate constant for the reference compound cyclohexane. Reaction products were analyzed by gas chromatography, in situ Fourier transform infrared spectroscopy, and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS). The products identified and quantified were (with their molar yields) as follows: from 2-pentanone, formaldehyde, 1.03±0.10; acetaldehyde, 0.51±0.11; propanal, 0.19±0.03; 2,4-pentanedione, 0.12±0.03; and molecular weight 147 organic nitrates, 0.12±0.04; and from 2-heptanone, formaldehyde, 0.38±0.08; acetaldehyde, approximately 0.05; propanal, approximately 0.05; butanal, 0.07±0.01; pentanal, 0.09±0.01; and molecular weight 175 organic nitrates, 0.18±0.05. API-MS analyses also showed the formation of products of molecular weight 128 and 144 from 2-heptanone, anticipated to be C7-dicarbonyl(s) and C7-hydroxydicarbonyl(s), respectively. While 94±13% of the reaction pathways of the 2-pentanone reaction are accounted for, it appears that a substantial fraction (>50%) of the initially formed alkoxy radicals from 2-heptanone undergo isomerization to form products which could not be quantified.

Microwave irradiation of ketoximes on wet silica supported sodium bismuthate under environmentally friendly solvent-free condition provides a fast, efficient and simple method for regeneration of ketones in high yields.

1,1,1-Tris(4-hydroxyphenyl)ethane, a branching agent for polycarbonates, is prepared by the reaction of phenol with 2,4-pentanedione in the presence of sulfuric acid and at least one mercapto sulfonic acid such as 3-mercaptopropanesulfonic acid as promoter. By employing specific proportions of the promoter and sulfuric acid, high product yields can be obtained in relatively short times.

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The keno-enol equilibrium constants of acetylacetone, ethyl acetoacetate and ethyl benzoylacetate in water at 25°C are determined by studying the influence of surfactants on their UV-VIS spectra, following the method applied to benzoylacetone published recently. These measured equilibrium constants are used to obtain the reactivity of the ketones towards several nitrosating agents. For this end, the nitrosation reaction of benzoylacetone, acetylacetone, ethyl acetoacetate and ethyl benzoylacetate are studied in aqueous acidic solution in the presence and absence of Cl-, Br- or SCN-. Analysis of the kinetic data indicates that the rate-limiting step is, in every case, the reaction of the enol.

Highly stereoselective N-acyliminium ion coupling reactions of β-ketoester derived silyl enol ethers with enantiopure lactams derived from (S)-malic acid are reported. This reaction type is applied in the synthesis of the enantiopure C-2 substituted lactam 27, a plausible intermediate in a projected synthesis of ptilomycalin A.

α'- and γ-Dianions of β-(monoalkylamino) α,β-unsaturated ketones react with trialkylchlorosilanes leading to α'- and γ-trialkylsilylenaminones. Conversely from trimethylchlorosilane, the reaction between dianions of 3-(N-isopropylamino)-1-arylbut-2-en-1-ones and t-butyldimethylchlorosilane or triisopropylchlorosilane leads to the corresponding 4-trialkylsilyl derivatives. An explanation of these findings is reported. Hydrolysis of these compounds affords the until now unknown α' silylated β-diketones.

The geminal interactions of the two carbonyl groups in seven β-diketones of the type 8-9 and 11-13 were estimated from their enthalpies of formation, which were deduced from their heats of combustion and enthalpies of vaporization.The radical stabilisation enthalpies RSE of the α,α'-diketoalkyl radicals 9-13 were obtained from the enthalpies of activation ΔH(excit.) of thermal CC bond cleavage of eight model compounds of the type 9-13 by their comparison with ΔH(excit.) of comparable hydrocarbons of similar strain.For non-cyclic α,α'-diacylalkyl radicals and six-membered cyclic ones RSE = 54.8 +/- 1.3 kJ mol-1 was determined, which indicates an additive stabilisation by two carbonyl groups. - Key Words: Enthalpies of formation/ Geminal substituents, energetic interaction of/ Bond cleavage, C-C, kinetics of/ Radicals, stability of/ Increments, thermochemical/ Bond strength, substituent effects on

The crystal structure and characterization in solution are described for a very regioselective hydroformylation catalyst, RhH(CO)2(diphosphite) with as the diphosphite.The complex is formed under CO-H2 pressure from Rh(CO)2Acac and has a distorted TBP geometry with both phosphorus atoms in equatorial positions.Keywords: Rhodium; Diphosphite; Hydroformylation; Catalysis; Crystal structure

The reaction of 2-acyl 1,3-dicarbonyl compounds with hydrazine and phenylhydrazine was studied by 1H NMR spectroscopy.It was shown that the formation of functionally 4-substituted pyrazoles is promoted if the reaction is conducted in protic solvents at reduced temperature.The presence of the benzoyl groups in the 2-acyl 1,3-dicarbonyl compounds leads to the preferential formation of the cleavage products, i.e., the corresponding acylhydrazines and 1,3-dicarbonyl compounds.It was established that the initial reaction product is consumed in two directions, i.e., cyclization with the formation of functionally 4-substituted pyyrazoles and cleavage with the formation of acetylhydrazines and the corresponding 1,3-dicarbonyl compounds.

The hydrolysis of the title compound occurs by the four-step mechanism typical for the hydrolysis of olefins PhCH=CXY where X and/or Y are electron-withdrawing groups.These steps are nucleophilic attack by OH(-) or water on the olefin to form PhCH(OH)C(-)(COMe)2 (T-OH); carbon protonation of T-OH to form PhCH(OH)CH(COMe)2 (T0OH); oxygen deprotonation of T0OH to form PhCH(O(-))CH(COMe)2 (T-O); and collapse of T-O to PhCH=O and acetylacetonate anion.In strongly basic solution two kinetic processes were observed.To a good approximation the fast one can be assigned to reversible OH(-) addition to the substrate (kOH1, kH2O-1) to form T-OH and the slow one to irreversible conversion of T-OH to final products with rate-limiting carbon protonation of T-OH by water (kH2O2).This latter interpretation is at variance with one offered earlier by Calmon and Calmon.In acidic solution only one kinetic process was observed; it corresponds to rate-limiting water addition to the substrate (kH2O1).Rate constants for hydronium ion catalyzed reversion of T-OH to reactants (kH-1) and for carbon protonation of T-OH by H3O(+) (kH2), acetic acid, and DABCOH(+) (kBH2) were also obtained from pH-jump experiments on T-OH.Approximate intrinsic rate constants for water and OH(-) addition to benzylideneacetylacetone were calculated from kH2O2 and kOH1, respectively, and compared with those for the corresponding reactions of benzylidenemalondialdehyde and benzylidene Meldrum's acid as well as other olefins.This comparison indicates that the intrinsic reactivity of benzylideneacetylacetone toward OH(-) and water is "normal", and sheds more light on its "abnormal" intrinsic reactivity toward secondary alicyclic amines reported earlier.

A quantitative analysis is described for solvent effects on homogenous chemical equilibria in dilute aqueous solutions in terms of pairwise solute-solute interactions.Solvent effects of a series of monohydric alcohols on the keto-enol tautomeric equilibrium of pentane-2,4-dione (PD) have been measured in order to test the applicability of the new method.Observed medium effects could be successfully accounted for on the basis of contribktions of methylene and hydroxy groups.In addition, the dependence of the equilibrium quotient on the concentration of PD has been analysed in terms of cosolvent effects.