A continuous reaction network that produces RNA precursors.

Continuous reaction networks, which do not rely on purification or timely additions of reagents, serve as models for chemical evolution and have been demonstrated for compounds thought to have played important roles for the origins of life such as amino acids, hydroxy acids, and sugars. Step-by-step chemical protocols for ribonucleotide synthesis are known, but demonstrating their synthesis in the context of continuous reaction networks remains a major challenge. Herein, compounds proposed to be important for prebiotic RNA synthesis, including glycolaldehyde, cyanamide, 2-aminooxazole, and 2-aminoimidazole, are generated from a continuous reaction network, starting from an aqueous mixture of NaCl, NH4Cl, phosphate, and HCN as the only carbon source. No well-timed addition of any other reagents is required. The reaction network is driven by a combination of γ radiolysis and dry-down. γ Radiolysis results in a complex mixture of organics, including the glycolaldehyde-derived glyceronitrile and cyanamide. This mixture is then dried down, generating free glycolaldehyde that then reacts with cyanamide/NH3 to furnish a combination of 2-aminooxazole and 2-aminoimidazole. This continuous reaction network models how precursors for generating RNA and other classes of compounds may arise spontaneously from a complex mixture that originates from simple reagents.

Mechanism of ozonation enhanced formation of haloacetaldehydes during subsequent chlorination.

Haloacetaldehydes (HAs) are the third prevalent group of disinfection by-products of great health concern. A bench-scale study was performed to investigate the formation and speciation of HAs in raw and treated waters after chlorination and ozonation-chlorination. Pre-ozonation resulted in enhanced HA formation during subsequent chlorination, and the HA yields from ozonation-chlorination were 1.66 and 1.63 times higher than that from chlorination of raw and treated waters. The mechanism about the increase of HA formation during ozonation-chlorination was systematically investigated in this study. The results showed that acetaldehyde formed after ozonation was the dominant precursor for the enhanced HA formation during subsequent chlorination. Increase in pH and chlorine dose increased HA formation during acetaldehyde chlorination. Based on the kinetic studies on the HA formation during acetaldehyde chlorination and the HA stabilities with and without free chlorine, it was found that chlorine was incorporated into the α-hydrogen in acetaldehyde to form a sequence of mono-, di- and tri-chloroacetaldehyde. During this process, these three chlorinated acetaldehydes would also undergo base-catalyzed hydrolysis through decarburization and dehalogenation pathways. This study elucidated that acetaldehyde formed after ozonation resulted in the increase of HA formation during subsequent chlorination. This study also revealed the formation pathway of HA during chlorination of acetaldehyde, which would help to minimize HA formation at drinking water plants.

Pt-Based Catalysts for Electrochemical Oxidation of Ethanol.

Despite its attractive features as a power source for direct alcohol fuel cells, utilization of ethanol is still hampered by both fundamental and technical challenges. The rationale behind the slow and incomplete ethanol oxidation reaction (EOR) with low selectivity towards CO2 on most Pt-based catalysts is still far from being understood, and a number of practical problems need to be addressed before an efficient and low-cost catalyst is designed. Some recent achievements towards solving these problems are presented. Pt film electrodes and Pt monolayer (PtML) electrodes on various single crystal substrates showed that EOR follows the partial oxidation pathway without C-C bond cleavage, with acetic acid and acetaldehyde as the final products. The role of the substrate lattice on the catalytic properties of PtML was proven by the choice of appropriate M(111) structure (M = Pd, Ir, Rh, Ru and Au) showing enhanced kinetics when PtML is under tensile strain on Au(111) electrode. Nanostructured electrocatalysts containing Pt-Rh solid solution on SnO2 and Pt monolayer on non-noble metals are shown, optimized, and characterized by in situ methods. Electrochemical, in situ Fourier transform infrared (FTIR) and X-ray absorption spectroscopy (XAS) techniques highlighted the effect of Rh in facilitating C-C bond splitting in the ternary PtRh/SnO2 catalyst. In situ FTIR proved quantitatively the enhancement in the total oxidation pathway to CO2, and in situ XAS confirmed that Pt and Rh form a solid solution that remains in metallic form through a wide range of potentials due to the presence of SnO2. Combination of these findings with density functional theory calculations revealed the EOR reaction pathway and the role of each constituent of the ternary PtRh/SnO2 catalyst. The optimal Pt:Rh:Sn atomic ratio was found by the two in situ techniques. Attempts to replace Rh with cost-effective alternatives for commercially viable catalysts has shown that Ir can also split the C-C bond in ethanol, but the performance of optimized Pt-Rh-SnO2 is still higher than that of the Pt-Ir-SnO2 catalyst.

Effect of Calcination Temperature on Mg-Al Layered Double Hydroxides (LDH) as Promising Catalysts in Oxidative Dehydrogenation of Ethanol to Acetaldehyde.

Oxidative dehydrogenation of ethanol to acetaldehyde over Mg-Al layered double hydroxides (LDH) and their differently calcined derivative catalysts was investigated in this study. The Mg-Al catalysts were synthesized via co-precipitation method and calcined at different temperatures at 450°C, 600°C and 900°C. It revealed that the calcination temperature affected the physicochemical properties and the catalytic activity of these catalysts toward the oxidative dehydrogenation of ethanol. It was found that ethanol conversion increased with increasing reaction temperature from 200 to 400°C, whereas acetaldehyde selectivity decreased. At low reaction temperature (200-300°C), the non-calcined catalyst (Mg-Al-000) showed the highest ethanol conversion, which can be attributed to the hydroxyl groups on surface having acetaldehyde as a major product. The calcination process led to formation of mixed oxide phase in Mg-Al catalysts as proven by the XRD and FT-IR results. The catalyst calcined at 450°C (Mg-Al-450) exhibited the highest basicity as measured by the CO2-TPD with ethanol conversion of 45.8% and acetaldehyde yield of 29.7% at 350°C.

Characterization of Aldehyde Dehydrogenases Applying an Enzyme Assay with In Situ Formation of Phenylacetaldehydes.

Herein, different dehydrogenases (DH) were characterized by applying a novel two-step enzyme assay. We focused on the NAD(P)+-dependent phenylacetaldehyde dehydrogenases because they produce industrially relevant phenylacetic acids, but they are not well studied due to limited substrate availability. The first assay step comprises a styrene oxide isomerase (440 U mg-1protein) which allows the production of pure phenylacetaldehydes (>70 mmol L-1) from commercially available styrene oxides. Thereafter, a DH of interest can be added to convert phenylacetaldehydes in a broad concentration range (0.05 to 1.25 mmol L-1). DH activity can be determined spectrophotometrically by following cofactor reduction or alternatively by RP-HPLC. This assay allowed the comparison of four aldehyde dehydrogenases and even of an alcohol dehydrogenase with respect to the production of phenylacetic acids (up to 8.4 U mg-1protein). FeaB derived from Escherichia coli K-12 was characterized in more detail, and for the first time, substituted phenylacetaldehydes had been converted. With this enzyme assay, characterization of dehydrogenases is possible although the substrates are not commercially available in sufficient quality but enzymatically producible. The advantages of this assay in comparison to the former one are discussed.

Spectroscopic evidence for origins of size and support effects on selectivity of Cu nanoparticle dehydrogenation catalysts.

Selective dehydrogenation catalysts that produce acetaldehyde from bio-derived ethanol can increase the efficiency of subsequent processes such as C-C coupling over metal oxides to produce 1-butanol or 1,3-butadiene or oxidation to acetic acid. Here, we use in situ X-ray absorption spectroscopy and steady state kinetics experiments to identify Cuδ+ at the perimeter of supported Cu clusters as the active site for esterification and Cu0 surface sites as sites for dehydrogenation. Correlation of dehydrogenation and esterification selectivities to in situ measures of Cu oxidation states show that this relationship holds for Cu clusters over a wide-range of diameters (2-35 nm) and catalyst supports and reveals that dehydrogenation selectivities may be controlled by manipulating either.

Efficient One-Pot Synthesis of Thiazol-2-imine Derivatives through Regioselective Reaction Between Primary Amines, Phenylisothiocyanate, and α-Chloroacetaldehyde.

AIM AND OBJECTIVE: Thiazol-2-imine derivatives are interested for their pharmaceutical and biologic activities. A literature survey reveals that there have been no any reports on the synthesis of thiazol-2-imine derivatives without substituents in position C-4 and C-5 via one-pot reaction. Herein we report an efficient one-pot route for synthesis of these compounds in good to high yields. MATERIALS AND METHOD: To a stirred mixture of amine (1 mmol) and phenylisothiocyanate (1 mmol) in EtOH (2 ml), KI (0.1 mmol) and DABCO (0.2 mmol) were added under reflux condition. Then α- chloroacetaldehyde (2 mmol) was added drop wise to the reaction mixture. After completion of the reaction, the product was purified over a silica gel short column (EtOAc/n-Hexane, 1:9). RESULTS: One pot reaction of primary amine, phenylisocyanate, and α-chloroacetaldehyde was carried out in the presence of various base and KI in different solvents. It was found that the maximum yield was obtained when the temperature reaches to the boiling point of EtOH. Comparing the reaction results in EtOH, CH3CN, THF, CH2Cl2, and H2O at reflux in the presence of various base, demonstrate that the yield of reaction in EtOH in the presence of DABCO was the most effective. When the reaction runs at the 20 mol% of the DABCO and 10 mol% of the KI, the yield and the time of the reaction were excellent. CONCLUSION: One-pot procedure can be used for the synthesis of thiazol-2-imine derivatives via the reaction of primary amines, α-chloroacetaldehyde, and phenylisothiocyanate in the presence of a catalytic amount of DABCO and potassium iodide in ethanol.

Automation of [(18) F]fluoroacetaldehyde synthesis: application to a recombinant human interleukin-1 receptor antagonist (rhIL-1RA).

[(18) F]Fluoroacetaldehyde is a biocompatible prosthetic group that has been implemented pre-clinically using a semi-automated remotely controlled system. Automation of radiosyntheses permits use of higher levels of [(18) F]fluoride whilst minimising radiochemist exposure and enhancing reproducibility. In order to achieve full-automation of [(18) F]fluoroacetaldehyde peptide radiolabelling, a customised GE Tracerlab FX-FN with fully programmed automated synthesis was developed. The automated synthesis of [(18) F]fluoroacetaldehyde is carried out using a commercially available precursor, with reproducible yields of 26% ± 3 (decay-corrected, n = 10) within 45 min. Fully automated radiolabelling of a protein, recombinant human interleukin-1 receptor antagonist (rhIL-1RA), with [(18) F]fluoroacetaldehyde was achieved within 2 h. Radiolabelling efficiency of rhIL-1RA with [(18) F]fluoroacetaldehyde was confirmed using HPLC and reached 20% ± 10 (n = 5). Overall RCY of [(18) F]rhIL-1RA was 5% ± 2 (decay-corrected, n = 5) within 2 h starting from 35 to 40 GBq of [(18) F]fluoride. Specific activity measurements of 8.11-13.5 GBq/µmol were attained (n = 5), a near three-fold improvement of those achieved using the semi-automated approach. The strategy can be applied to radiolabelling a range of peptides and proteins with [(18) F]fluoroacetaldehyde analogous to other aldehyde-bearing prosthetic groups, yet automation of the method provides reproducibility thereby aiding translation to Good Manufacturing Practice manufacture and the transformation from pre-clinical to clinical production.

Reaching Back to Jump Forward: Recent Efforts towards a Systems-Level Hypothesis for an Early RNA World.

In the spring of the world: Reductive homologation of cyanidic precursors creates the carbon scaffold for multiple classes of biologically relevant compounds. This chemistry underpins a scenario for the formation of a protometabolism on the way to an RNA world.

Low-energy electron-induced chemistry of condensed methanol: implications for the interstellar synthesis of prebiotic molecules.

In the interstellar medium, UV photolysis of condensed methanol (CH3OH), contained in ice mantles surrounding dust grains, is thought to be the mechanism that drives the formation of "complex" molecules, such as methyl formate (HCOOCH3), dimethyl ether (CH3OCH3), acetic acid (CH3COOH), and glycolaldehyde (HOCH2CHO). The source of this reaction-initiating UV light is assumed to be local because externally sourced UV radiation cannot penetrate the ice-containing dark, dense molecular clouds. Specifically, exceedingly penetrative high-energy cosmic rays generate secondary electrons within the clouds through molecular ionizations. Hydrogen molecules, present within these dense molecular clouds, are excited in collisions with these secondary electrons. It is the UV light, emitted by these electronically excited hydrogen molecules, that is generally thought to photoprocess interstellar icy grain mantles to generate "complex" molecules. In addition to producing UV light, the large numbers of low-energy (< 20 eV) secondary electrons, produced by cosmic rays, can also directly initiate radiolysis reactions in the condensed phase. The goal of our studies is to understand the low-energy, electron-induced processes that occur when high-energy cosmic rays interact with interstellar ices, in which methanol, a precursor of several prebiotic species, is the most abundant organic species. Using post-irradiation temperature-programmed desorption, we have investigated the radiolysis initiated by low-energy (7 eV and 20 eV) electrons in condensed methanol at - 85 K under ultrahigh vacuum (5 x 10(-10) Torr) conditions. We have identified eleven electron-induced methanol radiolysis products, which include many that have been previously identified as being formed by methanol UV photolysis in the interstellar medium. These experimental results suggest that low-energy, electron-induced condensed phase reactions may contribute to the interstellar synthesis of "complex" molecules previously thought to form exclusively via UV photons.

Infrared and reflectron time-of-flight mass spectroscopic study on the synthesis of glycolaldehyde in methanol (CH3OH) and methanol-carbon monoxide (CH3OH-CO) ices exposed to ionization radiation.

We present conclusive evidence on the formation of glycolaldehyde (HOCH2CHO) synthesized within astrophysically relevant ices of methanol (CH3OH) and methanol-carbon monoxide (CH3OH-CO) upon exposure to ionizing radiation at 5.5 K. The radiation induced chemical processes of the ices were monitored on line and in situ via infrared spectroscopy which was complimented by temperature programmed desorption studies post irradiation, utilizing highly sensitive reflectron time-of-flight mass spectrometry coupled with single photon fragment free photoionization (ReTOF-PI) at 10.49 eV. Specifically, glycolaldehyde was observed via the v14 band and further enhanced with the associated frequency shifts of the carbonyl stretching mode observed in irradiated isotopologue ice mixtures. Furthermore, experiments conducted with mixed isotopic ices of methanol-carbon monoxide (13CH3OH-CO, CH3(18)OH-CO, CD3OD-13CO and CH3OH-C18O) provide solid evidence of at least three competing reaction pathways involved in the formation of glycolaldehyde via non-equilibrium chemistry, which were identified as follows: (i) radical-radical recombination of HCO and CH2OH formed via decomposition of methanol--the "two methanol pathway"; (ii) via the reaction of one methanol unit (CH2OH from the decomposition of CH3OH) with one carbon monoxide unit (HCO from the hydrogenation of CO)--the "one methanol, one carbon monoxide pathway"; and (iii) formation via hydrogenation of carbon monoxide resulting in radicals of HCO and CH2OH--the "two carbon monoxide pathway". In addition, temperature programmed desorption studies revealed an increase in the amount of glycolaldehyde formed, suggesting further thermal chemistry of trapped radicals within the ice matrix. Sublimation of glycolaldehyde during the warm up was also monitored via ReTOF-PI and validated via the mutual agreement of the associated isotopic frequency shifts within the infrared band positions and the identical sublimation profiles obtained from the ReTOF spectra and infrared spectroscopy of the corresponding isotopes. In addition, an isomer of glycolaldehyde (ethene-1,2-diol) was tentatively assigned. Confirmation of the identified pathways based on infrared spectroscopy was also obtained from the observed ion signals corresponding to isotopomers of glycolaldehyde. These coupled techniques provide clear, concise evidence of the formation of a complex and astrobiologically important organic, glycolaldehyde, relevant to the icy mantles observed in the interstellar medium.

Continuous-flow synthesis of monoarylated acetaldehydes using aryldiazonium salts.

Anilines and ethyl vinyl ether can be used as precursors for a process that is the synthetic equivalent of the α-arylation of acetaldehyde enolate. The reaction manifests a high level of functional group compatibility, allowing the ready preparation of a number of synthetically valuable compounds.

Role of surface-bound intermediates in the oxygen-assisted synthesis of amides by metallic silver and gold.

A general mechanism for the oxygen-assisted synthesis of amides over metallic gold and silver surfaces has been derived from the study of acetaldehyde and dimethylamine in combination with previous work, allowing detailed comparison of the two surfaces' reactivities. Facile acetylation of dimethylamine by acetaldehyde occurs with high selectivity on oxygen-covered silver and gold (111) crystals via a common overall mechanism with different rate-limiting steps on the two metals. Adsorbed atomic oxygen activates the N-H bond of the amine leading to the formation of an adsorbed amide, which attacks the carbonyl carbon of the aldehyde, forming an adsorbed hemiaminal. Because aldehydes are known to form readily from partial oxidation of alcohols, our mechanism also provides insight into the related catalytic coupling of alcohols and amines. The hemiaminal ß-H eliminates to form the coupled amide product. On silver, ß-H elimination from the hemiaminal is rate-limiting, whereas on gold desorption of the amide is the slow step. Silver exhibits high selectivity for the coupling reaction for adsorbed oxygen concentrations between 0.01 and 0.1 monolayer, whereas gold exhibits selectivity more strongly dependent on oxygen coverage, approaching 100% at 0.03 monolayer. The selectivity trends and difference in rate-limiting steps are likely due to the influence of the relative stability of the adsorbed hydroxyl groups on the two surfaces. Low surface coverages of oxygen lead to the highest selectivity. This study provides a general framework for the oxygen-assisted coupling of alcohols and aldehydes with amines over gold- and silver-based catalysts in either the vapor or the liquid phase.

Stereocontrolled synthesis of vicinal diamines by organocatalytic asymmetric Mannich reaction of N-protected aminoacetaldehydes: formal synthesis of (-)-agelastatin A.

The 1,2-diamine (vicinal diamine) motif is present in a number of natural products with interesting biological activity and in many chiral molecular catalysts. The efficient and stereocontrolled synthesis of enantioenriched vicinal diamines is still a challenge to modern chemical methodology. We report here both syn- and anti-selective asymmetric direct Mannich reactions of N-protected aminoacetaldehydes with N-Boc-protected imines catalyzed by proline and the axially chiral amino sulfonamide (S)-3. This organocatalytic process represents the first example of a Mannich reaction using Z- or Boc-protected aminoacetaldehyde as a new entry of α-nitrogen functionalized aldehyde nucleophile in enamine catalysis. The obtained optically active vicinal diamines are useful chiral synthons as exemplified by the formal synthesis of (-)-agelastatin A.

Rotational spectrum and conformational composition of cyanoacetaldehyde, a compound of potential prebiotic and astrochemical interest.

The rotational spectrum of cyanoacetaldehyde (NCCH(2)CHO) has been investigated in the 19.5-80.5 and 150-500 GHz spectral regions. It is found that cyanoacetaldehyde is strongly preferred over its tautomer cyanovinylalcohol (NCCH═CHOH) in the gas phase. The spectra of two rotameric forms of cyanoacetaldehyde produced by rotation about the central C-C bond have been assigned. The C-C-C-O dihedral angle has an unusual value of 151(3)° from the synperiplanar (0°) position in one of the conformers denoted I, while this dihedral angle is exactly synperiplanar in the second rotamer called II, which therefore has C(s) symmetry. Conformer I is found to be preferred over II by 2.9(8) kJ/mol from relative intensity measurements. A double minimum potential for rotation about the central C-C bond with a small barrier maximum at the exact antiperiplanar (180°) position leads to Coriolis perturbations in the rotational spectrum of conformer I. Selected transitions of I were fitted to a Hamiltonian allowing for this sort of interaction, and the separation between the two lowest vibrational states was determined to be 58794(14) MHz [1.96112(5) cm(-1)]. Attempts to include additional transitions in the fits using this Hamiltonian failed, and it is concluded that it lacks interaction terms to account satisfactorily for all the observed transitions. The situation was different for II. More than 2000 transitions were assigned and fitted to the usual Watson Hamiltonian, which allowed very accurate values to be determined not only for the rotational constants, but for many centrifugal distortion constants as well. Two vibrationally excited states were also assigned for this form. Theoretical calculations were performed at the B3LYP, MP2, and CCSD levels of theory using large basis sets to augment the experimental work. The predictions of these calculations turned out to be in good agreement with most experimental results.

Biochemical evaluation of a parsley tyrosine decarboxylase results in a novel 4-hydroxyphenylacetaldehyde synthase enzyme.

Plant aromatic amino acid decarboxylases (AAADs) are effectively indistinguishable from plant aromatic acetaldehyde syntheses (AASs) through primary sequence comparison. Spectroscopic analyses of several characterized AASs and AAADs were performed to look for absorbance spectral identifiers. Although this limited survey proved inconclusive, the resulting work enabled the reevaluation of several characterized plant AAS and AAAD enzymes. Upon completion, a previously reported parsley AAAD protein was demonstrated to have AAS activity. Substrate specificity tests demonstrate that this novel AAS enzyme has a unique substrate specificity towards tyrosine (km 0.46mM) and dopa (km 1.40mM). Metabolite analysis established the abundance of tyrosine and absence of dopa in parsley extracts. Such analysis indicates that tyrosine is likely to be the sole physiological substrate. The resulting information suggests that this gene is responsible for the in vivo production of 4-hydroxyphenylacetaldehyde (4-HPAA). This is the first reported case of an AAS enzyme utilizing tyrosine as a primary substrate and the first report of a single enzyme capable of producing 4-HPAA from tyrosine.

Rapid, one-pot synthesis of ß-siloxy-α-haloaldehydes.

The Mukaiyama cross-aldol reaction of α-fluoro-, α-chloro-, and α-bromoacetaldehyde-derived (Z)-tris(trimethylsilyl)silyl enol ethers is described, furnishing anti-ß-siloxy-α-haloaldehydes. A highly diastereoselective, one-pot, sequential double-aldol process is developed, affording novel ß,δ-bissiloxy-α,γ-bishaloaldehydes. Reactions are catalyzed by C(6)F(5)CHTf(2) and C(6)F(5)CTf(2)AlMe(2) (0.5-1.5 mol %) and provide access to halogenated polyketide fragments.

Acetaldehyde production from ethanol and glucose by non-Candida albicans yeasts in vitro.

BACKGROUND: Major environmental risk factors for upper digestive tract cancers are tobacco smoking, alcohol intake and poor oral hygiene. They all result in increased acetaldehyde (ACH) levels in saliva which has been shown to be carcinogenic. During alcohol challenge the oral microbiota is the main determinant of the local ACH concentration. Many bacteria and Candida albicans have been shown to be capable of ACH production. Moreover, chronic candidal mucositis can be carcinogenic. The ability of non-C. albicans Candida to produce ACH has not been studied. AIM: The aim of this study was to explore the ability of non-C. albicans Candida species to produce ACH in vitro during ethanol and glucose incubation. METHODS: A total of 30 non-C. albicans Candida isolates and one C. albicans reference strain were used. The cells were exposed to 11 mM of ethanol and to 100mM glucose in vitro. ACH was measured by gas chromatography. RESULTS: All Candida isolates produced significant amounts of ACH in ethanol incubation. C. tropicalis isolates were the highest (252.3 microM) and C. krusei isolates were the lowest (54.6 microM) producers of ACH from ethanol. Only C.glabrata produced significant amounts of ACH by fermentation from glucose. CONCLUSION: Colonization of oral mucosa with a non-C.albicans species such as C. glabrata, capable of producing carcinogenic amounts of ACH from both ethanol and glucose, may contribute to the development of oral cancer.

Catalytic processing of lactic acid over Pt/Nb(2)O(5).

Dilute aqueous solutions of lactic acid (30 %wt.) can be catalytically processed at 573 K and 57 bar over a low-metal-content Pt(0.1 %)/Nb(2)O(5) catalyst in a spontaneously separating organic phase rich in valuable products such as C(4)-C(7) ketones. An increase in the lactic acid concentration to 60 wt % allows conversion of approximately 50 % of the carbon feed in this organic layer, while maintaining good stability of the catalyst. Experiments at low conversion showed that lactic acid reacts first over Pt(0.1 %)/Nb(2)O(5) to produce acetaldehyde and propanoic acid (along with CO and CO(2) in the gas phase). These compounds (less oxygenated than lactic acid but still reactive) are the key intermediates in the overall process, and they react differently depending on the nature of the catalyst support. In particular, reaction kinetics studies with propanoic acid as feed showed that Pt(0.1 %)/Nb(2)O(5) favored the formation of pentanones by ketonization reactions, whereas a monofunctional Pt(0.1 %)/carbon catalyst produced ethane and CO(x) by decomposition reactions. In the same manner, acetaldehyde was preferentially hydrogenated to ethanol over Pt(0.1 %)/carbon, whereas the presence of niobia allowed this intermediate to react (by successive aldol condensations) to form C(4)-C(7) condensation products stored in the organic phase. Finally, reaction pathways are proposed to explain the catalytic processing of lactic acid over bifunctional Pt(0.1 %)/Nb(2)O(5). In this scheme, metal sites catalyze hydrogenation reactions and niobia promotes C--C coupling processes (ketonization and aldol condensation), in contrast to C--C cleavage reactions which take place preferentially over Pt(0.1 %)/carbon and lead to loss of carbon in the gas effluent as CO, CO(2), and methane.

Novel defluorinative alkylation of trifluoroacetaldehyde N,O-acetal derivatives and its application to multi-component reaction.

The reaction of trifluoroacetaldehyde N,O-acetal derivatives with 2 molar equivalents of alkyllithium reagents proceeded viabeta-elimination of fluoride followed by alkyl transfer from excess alkyllithium to the generated ketene N,O-acetal intermediate at the beta-carbon of fluorine groups.