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Conversion of cellulose to 1-(furan-2-yl)-2-hydroxyethanone has been demonstrated in concentrated zinc chloride solution under microwave irradiation. Compared with the conventional oil-bath heating mode, microwave irradiation significantly reduced the reaction time and increased the yield of 1-(furan-2-yl)-2-hydroxyethanone. A typical degradation reaction with cellulose produced 1-(furan-2-yl)-2-hydroxyethanone in 12.0% molar yield in ZnCl 2 solution (ZnCl2-H2O ratio = 2.25:1, w/w) with microwave irradiation at 600 W for 5 minutes at 135 °C.

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The tertiary amine-catalyzed direct asymmetric aldol reaction of 2-hydroxyacetophenones (2-hydroxy-1-arylethanones) with a variety of aliphatic aldehydes has been demonstrated. By using 20 mol-% of unmodified cinchonine as catalyst, the direct aldol reaction products were isolated in good yields and with remarkably high syn diastereocontrol and good asymmetric induction (40-78 % ee). This newly elaborated tertiary-amine-catalyzed direct asymmetric aldol reaction has extended the scope of organocatalytic processes to aromatic α-hydroxy ketones, which have hitherto been unreactive towards enamine catalysis. Unmodified cinchona alkaloids have been found to promote efficiently the direct aldol reaction of hydroxy ketones and various aldehydes in good yields and with remarkably high syn diastereocontrol and good asymmetric induction (40-78 % ee). Copyright

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Acid-catalysed conversion of biomass, specifically cellulose, holds promise to create value-added, renewable replacements for many petrochemical products. We investigated an unusual acid-catalysed transformation of cellulose and cellobiose in the biphasic solvent system zinc chloride hydrate (ionic liquid)/anisole. Here, furyl hydroxymethyl ketone and furfural are obtained as major products, which are valuable but less commonly formed in high yields in transformations of cellulosic substrates. We explored this chemistry in small-scale model reactions and applied the optimised methods to the conversion of cellulose in bench-scale processes. The optimum reaction system and preferred reaction conditions are defined to select for highly desirable furanoid products in the highest known yields (up to 46 %) directly from cellulose or cellobiose. The method avoids the use of added catalysts: the ionic solvent zinc chloride hydrate possesses the intrinsic acidity required for the hydrolysis and chemical transformation steps. The process involves inexpensive media for the catalytic conversion of cellulose into high-value products under mild processing conditions.

Japanese cedar (Cryptomeria japonica) was treated with 12 ionic liquid (IL)-water mixtures at 120 °C for 1 h. Production of 5-hydroxymethylfurfural, furfural and 2-hydroxyacetylfuran (2-HAF) was observed by HPLC and GC-MS. This is the first report to identify 2-HAF from lignocellulosics using ILs. The optimal IL-water mixture was found to be a 90% pyridinium chloride and 10% water w/w solution, although any IL-water mixture that contained pyridinium or imidazolium salts produced all three compounds in varying yields.

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The naturally occurring antioxidant Ascopyrone P (1,5-anhydro-4-deoxy-d-glycero-hex-1-en-3-ulose, 1) was prepared from the rare sugar 1,5-anhydro-d-fructose (AF, 3) in three steps in an overall yield of 36%. Thus, acetylation of 3 afforded the enolone 3,6-di-O-acetyl-1,5-anhydro-4-deoxy-d-glycero-hex-3-en-2-ulopyranose (4), which could be isomerised to 2,6-di-O-acetyl-1,5-anhydro-4-deoxy-d-glycero-hex-1-ene-3-ulose (6). Deacetylation of 6 under mild conditions gave crystalline Ascopyrone P (1).

An asymmetric [3 + 2] cycloaddition of vinyl ethylenecarbonates (VECs) and (E)-3-arylvinyl substituted benzo[d] isothiazole 1,1-dioxides has been developed using the Pd complex of a bidentate phosphoramidite (Me-BIPAM) as the catalyst, providing a wide variety of chiral multistereogenic vinyltetrahydrofurans in good yields with excellent diastereo- and enantioselectivities (up to >20:1 dr, 99% ee).

α-Imino ketone is a useful building block for the preparation of α-amino ketones and α-amino alcohols. However, its preparation has been seldomly seen. Herein, a metal-free and operationally simple strategy has been developed to generate α-imino ketones with high regioselectivity. Meanwhile, the method allowed for the preparation of various N,O-ketals with high regioselectivities and diastereoselectivities through cascade reactions in one pot.

A flexible, enantioselective route to highly functionalized α,β-unsaturated δ-lactones has been applied to the synthesis of 7-aza-phomopsolide E and its C-4 epimer. This approach relies on the application of the Noyori asymmetric hydrogenation of furyl ketone to produce the secondary furyl alcohol in high enantioexcess, which can be stereoselectively transformed into α,β-unsaturated-δ-lactones by a short, highly diastereoselective oxidation and reduction sequence. DCC and acid chloride couplings were used to introduce the side chains of the two natural product analogues.

The first catalytic asymmetric decarboxylative [3 + 2] cycloaddition reaction of ethynylethylene carbonates with malononitrile has been developed successfully by an organo/copper cooperative system. This strategy led to a series of optically active polysu

Valuable and direct aerobic oxidation reactions of 2-hydroxyacetophenones were explored. The concept was based on the in situ treatment of small quantities of aerobically formed α-keto aldehydes that drove the reactions to the corresponding products. This new strategy was applied for a variety of oxidative reactions of 2-hydroxyacetophenones, and valuable products such as phthalides, quinoxalines, and α-keto amides were obtained in good to high yields.

A method for the copper-catalyzed borylmethylation and borylation of vinyl cyclic carbonates through an SN2′ mechanism is reported. These singular reactions involve selective SN2′ allylic substitutions with concomitant ring opening of the cyclic carbonate and with extrusion of CO2 and formation of a useful hydroxyl functionality in a single step. The stereoselectivity of the homoallylic borylation and allylic borylation processes can be controlled, and synthetically useful unsaturated (E)-pent-2-ene-1,5-diols and (E)-but-2-ene-1,4-diols are accessed.

An efficient and green method for the α-hydroxylation of substituted ketones has been developed. This method includes the in situ conversion of various ketones into the corresponding silyl enol ethers and their oxidation to the corresponding α-hydroxy ketones. Two protocols have been established leading either to protected α-hydroxy carbonyls or free α-hydroxy ketones. Both procedures are easy to follow and lead to good to high yields for a variety of ketones.

In situ generation of the reactive amphoteric α-amino aldehyde with simple α-hydroxy ketones and phenylamine via Heyns rearrangement was proven to be feasible. Metal-free domino reactions based on this reactive intermediate were effectively used to afford important N-heterocycles including polysubstituted pyrroles, indoles, and quinoxalines conveniently. A simple starting material, water as the only byproduct, and diversity of the useful products will make this method greatly attractive for pharmaceutics.

The development of Rh(III)-catalyzed C-H conjugate addition/cyclization reactions that provide access to synthetically useful fused bi- and tricyclic nitrogen heterocycles is reported. A broad scope of C-H functionalization substrates and electrophilic olefin coupling partners is effective, and depending on the nature of the directing group, cyclic imide, amide, or heteroaromatic products are obtained. An efficient synthesis of a pyrrolophenanthridine alkaloid natural product, oxoassoanine, highlights the utility of this method.

Asymmetric hydrogenation of 4-substituted cyclic enamido esters catalyzed by a rhodium-TangPhos complex provides an efficient method for the synthesis of chiral 4-substituted oxazolinones with excellent yields and good enantioselectivities. The products are valuable chiral building blocks and the applications as chiral auxiliaries and pharmaceuticals are well-known.

Significant progress has been observed in recent years in the synthesis of allylic amines, which are important building blocks in synthetic chemistry. Most of these processes are effective toward the preparation of allylic amines, with limited potential to introduce three or four different substituents on the olefinic unit in a stereocontrolled fashion. Therefore, the discovery of a mild and operationally simple protocol allowing such challenging stereoselective synthesis of multisubstituted allylic amines remains an inspiring target. Herein, we report the first general and practical methodology for the stereoselective synthesis of tri- and tetrasubstituted allylic amines based on Pd-catalyzed conversion of allyl surrogates readily obtained from cyclic vinyl carbonates. These rare conversions are characterized by excellent stereoselectivity, operational simplicity, mild reaction conditions, and wide scope in reaction partners. DFT studies were performed to rationalize the stereocontrol in these allylic amine formation reactions, and evidence is provided that the formation of a six-membered palladacyclic intermediate leads toward the formation of (Z)-configured allylic amine products.

Abstract In this work, the catalytic effect of the Bronsted acid hydrochloric acid, the Bronsted base sodium hydroxide and the Lewis acid AlCl3 on the conversion of biomass derived carbohydrates is investigated. On the example of the glycolaldehyde conversion, it is shown that the Lewis acid catalyses the ketol-endiol-tautomerism, the dehydration, the retro-aldol-reaction and the benzilic-acid-rearrangement. The main products are C4- and C6-carbohydrates as well as their secondary products 2-hydroxybut-3-enoic acid 1 and several furans. Under the same reaction conditions hydrochloric acid catalyzes mainly the dehydration and sodium hydroxide the tautomerism and subsequent aldolization.

A highly stereoselective dynamic kinetic isomerization of Achmatowicz rearrangement products was discovered. This new internal redox isomerization provided ready access to key intermediates for the enantio- and diastereoselective synthesis of a series of naturally occurring sugars. The nature of the de novo synthesis also enables the preparation of both enantiomers.

An efficient and mild copper-catalyzed one-pot approach toward ynediones has been established. A variety of ynediones were constructed directly through oxidative coupling of alkyne with α-hydroxy ketone. Oxygen-oxidizing and neutral conditions in one-pot for a wide range of substrates including natural product derivatives make this transformation highly efficient and practical. On the basis of control experiments, in situ IR measurements, and isotopic labeling experiments, a plausible mechanism involving intermediate phenylglyoxal was drawn. Applications by synthesis of various heterocycles were also investigated.

The N-heterocyclic carbene-catalyzed coupling of several aldehydes with paraformaldehyde is reported, directly providing the corresponding valuable hydroxymethyl ketones. Results of first mechanistic experiments for this remarkably selective transformation are also provided.

Lignocellulosic biomass is an attractive resource for producing transportation fuels, and consequently novel approaches are being sought for transforming the lignin and cellulosic constituents of biomass to fuels or fuel additives. Glucose, the monomer of cellulose, is a good starting material for exploring such chemistries. We report here the results of an investigation aimed at identifying catalysts for the dehydration of glucose to 5- hydroxymethylfurfural (HMF) dissolved in ionic liquids and the subsequent conversion of HMF to 2,5-dimethylfuran (DMF), a high-energy content product that could be used as a fuel or fuel additive. Heteropoly acids were found to be exceptionally active and selective catalysts for the dehydration of glucose. Nearly 100% yield of HMF could be achieved using 12-molybdophosphoric acid (12-MPA) in a solution of 1-ethyl-3-methylimidazolium chloride (EMIMCl) and acetonitrile. The addition of acetonitrile to EMIMCl suppressed the formation of humins from glucose. The high HMF selectivity achievable with heteropoly acid catalysts is ascribed to stabilization of 1,2-enediol and other intermediates involved in the dehydration of glucose and the avoidance of forming the 2,3-enediol intermediate leading to furylhydroxymethyl ketone (FHMK). Carbon-supported metals, and in particular Pd/C, were effective in promoting the hydrogenation of HMF dissolved in EMIMCl and acetonitrile to DMF. The following intermediates were observed in the hydrogenation of HMF to DMF: 5-methylfurfural (MF), 5-methylfurfyl alcohol (MFA), and 2,5- dihydroxymethylfuran (DHMF). The relative rate of formation and consumption of these compounds was explored by using each of them as a reactant in order to identify the reaction pathway from HMF to DMF. It was also observed that HMF produced via glucose dehydration could be converted to DMF without isolation, if the dehydration catalyst, 12 MPA, was replaced by the hydrogenation catalyst, Pd/C. This two-step catalytic approach provides the basis for completely converting glucose to HMF and further converting HMF to DMF. The Royal Society of Chemistry 2010.

Paper, cotton, corn stover, straw, and wood are converted into furanic products in high yields (based on their cellulose content) using a simple, inexpensive process involving concurrent hydrolysis, dehydration, and substitution reactions coupled with continuous extraction into an organic phase. In a simultaneous process, the hemicellulose fraction of these substrates is converted into furfural, and together these constitute an efficient means for the total exploitation of the carbohydrate content of biomass.

(Chemical Equation Presented) Fueling up with furans: Cellulose can be converted into furanic biofuels in unprecedented yields using an inexpensive, simple process involving concurrent hydrolysis, dehydration, and chlorine substitution reactions coupled with continuous extraction into an organic phase (see scheme). Furanic ethers, such as those that can be derived from the products above, are known diesel additives.

Poly{[4-(hydroxy)(tosyloxy)iodo]styrene} was efficient in the α-hydroxylation reaction of ketones to afford α-hydroxyketones in dimethyl sulfoxide-water. The polymer reagent could be regenerated and reused.

Dehydrobrominations of benzoylated β-d-fructopyranosyl and α-l-sorbo-pyranosyl bromides have been examined to obtain suitable conditions for effecting the elimination toward the exo- as well as the endo-positions. In the fructose case, exposure to DBU in

Benzaldehyde lyase from the Pseudomonas Fluorescens catalyzed reaction of aromatic aldehydes with formaldehyde providing 2-hydroxy-1-arylethan-1-one in high yields via an acyloin linkage. Kinetic resolution of rac-benzoins with formaldehyde providing (S)-benzoins and 2-hydroxy-1-arylethan-1-one via C-C bond cleavage and a bond formation reaction.

Ketones react with [hydroxy(tosyloxy)iodo]benzene in dimethyl sulfoxide-water to afford α-hydroxyketones under neutral conditions and in good yields.

Toasting wood to be used in barrels for aging wine produces a great number of volatile and odiferous compounds. Three new volatile odorous compounds in toasted oak were identified. Analysis by high-performance gas chromatography of toasted oak extracts, combined with olfactory detection, enabled various chromatographic peaks with these specific aromas to be isolated. These same odors were simultaneously studied by heating glucose both with and without proline and phenylalanine. Aromatic compounds of interest were identified thanks to a combination of gas chromatography and both mass and infrared spectrometry. An analysis RMN was also used. Hydroxymaltol, 2,5-furanedicarbaldehyde, and furylhydroxymethyl ketone have been detected in extract of toasted oak wood. These molecules may be formed by direct pyrolysis of sugar or Maillard reactions. The acetylformoine was not detected in extract of toasted oak wood, whereas it was detected in heated extracts of various sugars and sugars mixtures with amino acids.

[Bis(trifluoroacetoxy)] iodobenzene and trifluoroacetic acid in CH3CN/H2O reacts with aromatic, heteroaromatic, and aliphatic ketones to afford α-hydroxyketones in moderate to good yields.

Hypervalent iodine oxidation of various silyl enol ethers (aromatic, heteroaromatic, and aliphatic) using iodosobenzene-boron trifluoride diethyl ether-water provides a general and direct route for the α-hydroxylation of ketones.The structures of 2-hydroxy- (8) and 3-hydroxy-acetylpyridine (9) are discussed as well as the scope and mechanism of the reaction.

The condensation of formaldehyde with another aldehyde catalyzed by 3-ethylbenzothiazolium bromide in the presence of triethylamine gives selectively 1-hydroxy 2-ones.This selective cross-acyloin condensation indicates an inverse selectivity in the reactions of the conjugate base of thiazolium salt 17 and of the carbanion bound to thiazolium ring 19 toward aldehyde.