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All total 132 Articles be found
All total 132 Articles be foundMild Selective Deoxygenation of Amine Oxides by Tin-Tin Bonded Derivatives
Jousseaume, Bernard,Chanson, Evelyne
, p. 55 - 56 (1987)
A new method of deoxygenation of amine oxides with tin reagent is proposed.It utilizes the reductive properties of the tin-tin bond in hexabutyldistannane or 1,2-dichlorotetrabutyldistannane.Oxides of tertiary amines are reduced into amines by hexabutyldistannane in high yields, whereas pyridine N-oxides react cleanly with 1,2-dichlorotetrabutyldistannane to give the corresponding pyridines.These reactions occur under mild conditions and are very selective.
Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions
Neyt, Nicole C.,Riley, Darren L.
, p. 1529 - 1536 (2018)
We recently reported a novel hybrid batch-flow synthesis of the antipsychotic drug clozapine in which the reduction of a nitroaryl group is described under flow conditions using sodium dithionite. We now report the expansion of this method to include the reduction of aldehydes. The method developed affords yields which are comparable to those under batch conditions, has a reduced reaction time and improved space-time productivity. Furthermore, the approach allows the selective reduction of aldehydes in the presence of ketones and has been demonstrated as a continuous process.
REDUCTION WITH POLYMER-BOUND NADH MODELS.
Dupas, G.,Bourguignon, J.,Ruffin, C.,Queguiner, G.
, p. 5141 - 5144 (1982)
We have performed numerous reductions with a NADH model grafted on a Merrifield resin.The yields are generally excellent and in all cases always superior to those obtained with "free" models.
Partial photocatalytic oxidations of 3-pyridinemethanol and 3-picoline by TiO2 prepared in HCl, HNO3 and H2SO4 at different temperatures
?etinkaya, S?d?ka,Yurdakal, Sedat
, p. 237 - 247 (2021)
Home prepared TiO2 photocatalysts were prepared from TiCl4 precursor in the absence and presence of HCl (1?6 M), HNO3 (1 M) or H2SO4 (1 M) at room temperature (RT), 60 or 100 °C. The TiO2 catalysts were characterised by XRD, BET, SEM and TGA techniques. TiO2 catalyst could not form at low temperature (up to 60 °C) in the presence of H2SO4. Just rutile phase was obtained for all TiO2 samples prepared at RT and 60 °C in HCl or HNO3. At 100 °C mainly both brookite and rutile phases were obtained in the presence of HCl or HNO3, whilst mainly anatase phase appeared in the presence of H2SO4. Nanorod structured TiO2 was formed in the presence of 1 M HCl or HNO3 at RT and 60 °C. The prepared TiO2 catalysts were used for partial oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 in water under UVA irradiation. Moreover, photocatalytic oxidation of 3-picoline, precursor of 3-pyridinemethanol, was also performed, but much lower product selectivity values were obtained with respect to 3-pyridinemethanol oxidation. However, selective 3-picoline oxidation could be performed at pH 2 with low activity. Degussa P25 was used for comparison and almost all home prepared catalysts showed a higher selectivity, but they showed to be less active than Degussa P25. The high selectivity of the home prepared samples was not due to the type of TiO2 phase, but mainly to the hydrophilicity of the TiO2 surface which allowed desorption of valuable products instead of their over-oxidation.
Silver-catalyzed hydrogenation of aldehydes in water
Jia, Zhenhua,Zhou, Feng,Liu, Mingxin,Li, Xingshu,Chan, Albert S. C.,Li, Chao-Jun
, p. 11871 - 11874 (2013)
Silver bullet: The first silver-catalyzed hydrogenation in water was developed. A silver complex containing a bulky monodentate phosphine ligand was used to generate alcohols from a broad range of aldehydes, including aliphatic, aromatic, and heterocyclic aldehydes. This method provides a direct and efficient route to alcohols from aldehydes and opens a new avenue in silver catalysis. Copyright
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Mosher,Tessieri
, p. 4925 (1951)
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4-Aza-N-benzyl bicyclo[2,2,2]octyl ammonium borohydride a highly chemoselective reagent for the reduction of aldehydes in the presence of ketones
Firouzabadi,Afsharifar
, p. 497 - 507 (1992)
The title compound reduces aldehydes in the presence of ketones with high chemoselectivity in t-butanol under reflux condition in high yields.
BIOMIMETIC REDUCTION WITH NON WATER-SENSITIVE NADH MODELS
Cazin, J.,Dupas, G.,Bourguignon, J.,Queguiner, G.
, p. 2375 - 2378 (1986)
Two NADH models were synthesized which are considerably less water-sensitive than classical-1,4 dihydronicotinamide derivatives such as N-benzyl-1,4 dihydronicotinamide (BNAH): these two models are reactive and more stable in the presence of water than previously reported models.
High-throughput synthesis and analysis of acylated cyanohydrins
Hamberg, Anders,Lundgren, Stina,Wingstrand, Erica,Moberg, Christina,Hult, Karl
, p. 4334 - 4341 (2007)
The yields and optical purities of products obtained from chiral Lewis acid/Lewis base-catalysed additions of ct-ketonitriles to prochiral aldehydes could be accurately determined by an enzymatic method. The amount of remaining aldehyde was determined after its reduction to an alcohol, whilst the two product enantiomers were analysed after subsequent hydrolysis first by the (S)-selective Candida antarctica lipase B and then by the unselective pig liver esterase. The method could be used for analysis of products obtained from a number of aromatic aldehydes and aliphatic ketonitriles. Microreactor technology was successfully combined with high-throughput analysis for efficient catalyst optimization.
Purification and characterization of an NADH-dependent alcohol dehydrogenase from Candida maris for the synthesis of optically active 1-(pyridyl)ethanol derivatives
Kawano, Shigeru,Yano, Miho,Hasegawa, Junzo,Yasohara, Yoshihiko
, p. 1055 - 1060 (2011)
A novel (R)-specific alcohol dehydrogenase (AFPDH) produced by Candida maris IFO10003 was purified to homogeneity by ammonium sulfate fractionation, DEAE-Toyopearl, and Phenyl-Toyopearl, and characterized. The relative molecular mass of the native enzyme was found to be 59,900 by gel filtration, and that of the subunit was estimated to be 28,900 on SDS-polyacrylamide gel electrophoresis. These results suggest that the enzyme is a homodimer. It required NADH as a cofactor and reduced various kinds of carbonyl compounds, including ketones and aldehydes. AFPDH reduced acetylpyridine derivatives, β-keto esters, and some ketone compounds with high enantioselectivity. This is the first report of an NADH-dependent, highly enantioselective (R)-specific alcohol dehydrogenase isolated from a yeast. AFPDH is a very useful enzyme for the preparation of various kinds of chiral alcohols.
CALCIUM ALKOXYALANATES. III. REDUCTION OF ORGANIC FUNCTIONAL GROUPS BY CALCIUM TETRAKIS(ALKOXY)ALANATES
Cucinella, S.,Dozzi, G.,Bruzzone, M.
, p. 21 - 28 (1982)
Calcium tetrakis(alkoxy)alanates obtained from different alcohols reduce aldehydes, ketones, acids, esters, acid chlorides and anhydrides to alcohols in high yields.Good results are achieved in the reduction of amides to amines.The reductions of nitrile and oxime groups and dehalogenation reactions are more difficult.Selectivity is possible in the reduction of organic epoxides.
Microwave-heated γ-Alumina Applied to the Reduction of Aldehydes to Alcohols
Dhokale, Bhausaheb,Susarrey-Arce, Arturo,Pekkari, Anna,Runemark, August,Moth-Poulsen, Kasper,Langhammer, Christoph,H?relind, Hanna,Busch, Michael,Vandichel, Matthias,Sundén, Henrik
, p. 6344 - 6355 (2020)
The development of cheap and robust heterogeneous catalysts for the Meerwein-Ponndorf-Verley (MPV) reduction is desirable due to the difficulties in product isolation and catalyst recovery associated with the traditional use of homogeneous catalysts for MPV. Herein, we show that microwave heated γ-Al2O3 can be used for the reduction of aldehydes to alcohols. The reaction is efficient and has a broad substrates scope (19 entries). The products can be isolated by simple filtration, and the catalyst can be regenerated. With the use of microwave heating, we can direct the heating to the catalyst rather than to the whole reaction medium. Furthermore, DFT was used to study the reaction mechanism, and we can conclude that a dual-site mechanism is operative where the aldehyde and 2-propoxide are situated on two adjacent Al sites during the reduction. Additionally, volcano plots were used to rationalize the reactivity of Al2O3 in comparison to other metal oxides.
Uncatalyzed Meerwein-Ponndorf-Oppenauer-Verley Reduction of Aldehydes and Ketones under Supercritical Conditions
Sominsky, Lena,Rozental, Esther,Gottlieb, Hugo,Gedanken, Aharon,Hoz, Shmaryahu
, p. 1492 - 1496 (2004)
When a solution of a carbonyl compound in alcohol (primary or secondary) is heated to ca. 300 °C, a disproportionation reaction, in which a carbonyl compound is reduced to the corresponding alcohol and the alcohol is oxidized to the corresponding ketone, takes place. This uncatalyzed variation of the Meerwein-Ponndorf-Oppenauer-Verley reaction gives, in certain cases, e.g., reduction of acetophenone or benzaldehyde by i-PrOH, almost quantitative yields. Yields are higher with secondary alcohols such as i-PrOH than with a primary alcohol such as EtOH. The reactions were also performed in a flow system by passing at a slow rate the same solutions through a glass or a metal coil heated to elevated temperatures. Ab initio calculations performed at the B3LYP/6-31G* level show that thermodynamically i-PrOH is a more potent reducing agent than EtOH by ca. 4 kcal/mol. The computations also show that in cases of aromatic carbonyl compounds, part of the deriving force is obtained from the entropy change of the reaction. The major contributor to the high yield, however, is the excess alcohol used, which shifts the equilibrium to the right. Calculated entropy of activation as well as isotopic H/D labeling suggest a cyclic transition state.
Disproportionation of aliphatic and aromatic aldehydes through Cannizzaro, Tishchenko, and Meerwein–Ponndorf–Verley reactions
Sharifi, Sina,Sharifi, Hannah,Koza, Darrell,Aminkhani, Ali
, p. 803 - 808 (2021/07/20)
Disproportionation of aldehydes through Cannizzaro, Tishchenko, and Meerwein–Ponndorf–Verley reactions often requires the application of high temperatures, equimolar or excess quantities of strong bases, and is mostly limited to the aldehydes with no CH2 or CH3 adjacent to the carbonyl group. Herein, we developed an efficient, mild, and multifunctional catalytic system consisting AlCl3/Et3N in CH2Cl2, that can selectively convert a wide range of not only aliphatic, but also aromatic aldehydes to the corresponding alcohols, acids, and dimerized esters at room temperature, and in high yields, without formation of the side products that are generally observed. We have also shown that higher AlCl3 content favors the reaction towards Cannizzaro reaction, yet lower content favors Tishchenko reaction. Moreover, the presence of hydride donor alcohols in the reaction mixture completely directs the reaction towards the Meerwein–Ponndorf–Verley reaction. Graphic abstract: [Figure not available: see fulltext.].
Iron-catalyzed chemoselective hydride transfer reactions
Coufourier, Sébastien,Ndiaye, Daouda,Gaillard, Quentin Gaignard,Bettoni, Léo,Joly, Nicolas,Mbaye, Mbaye Diagne,Poater, Albert,Gaillard, Sylvain,Renaud, Jean-Luc
supporting information, (2021/06/07)
A Diaminocyclopentadienone iron tricarbonyl complex has been applied in chemoselective hydrogen transfer reductions. This bifunctional iron complex demonstrated a broad applicability in mild conditions in various reactions, such as reduction of aldehydes over ketones, reductive alkylation of various functionalized amines with functionalized aldehydes and reduction of α,β-unsaturated ketones into the corresponding saturated ketones. A broad range of functionalized substrates has been isolated in excellent yields with this practical procedure.
