- N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading
-
We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
- Berkessel, Albrecht,Biswas, Animesh,Harnying, Wacharee,Sudkaow, Panyapon
-
supporting information
p. 19631 - 19636
(2021/08/09)
-
- METHOD FOR PREPARING HYDROXY OXIME
-
The present invention relates to a process for the preparation of hydroxy oximes. More particularly, the present invention relates to a method for preparing a hydroxy oxime capable of improving the yield of each process step and reducing the generation of ketoxime by-products which reduce the metal extractability of the hydroxy oxime as an extractant.
- -
-
Paragraph 0090-0098
(2021/05/11)
-
- FLOW CHEMISTRY SYNTHESIS OF ISOCYANATES
-
The disclosure provides, inter alia, safe and environmentally-friendly methods, such as flow chemistry, to synthesize isocyanates, such as methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate.
- -
-
Paragraph 0175; 0186-0187; 0281-0283
(2021/06/22)
-
- SYNTHESIS OF TRIETHYLENE GLYCOL BIS(2-ETHYLHEXANOATE)
-
A process for the transesterification of methyl-2- ethylhexanoate with triethylene glycol to produce triethylene glycol di-2-ethylhexanoate is provided. In the process, methyl-2- ethylhexanoate is combined with triethylene glycol to form a first mixture. The first mixture is heated in the presence of a catalyst to form a second mixture comprising methanol and triethylene glycol di-2-ethylhexanoate. Methanol is separated from the second mixture to yield triethylene glycol di-2-ethylhexanoate. Na2CO3, CS2CO3, K2CO3, Rb2CO3, sodium methoxide or titanium isopropoxide are suitable catalysts.
- -
-
Paragraph 0033
(2020/06/05)
-
- ESTER SYNTHESIS USING HETEROGENEOUS AU/TIO2 CATALYST
-
A process for direct esterification of an alkyl aldehyde with an alkyl alcohol to produce an alkyl ester is disclosed. The process comprises reacting an alkyl aldehyde with an alkyl alcohol in the presence of an Au/TiOa catalyst, a base and an enal or oxygen to form an ester and an aldehyde. The process avoids liberation of water and avoids the step of oxidation of the alkyl aldehyde to an alkyl acid.
- -
-
Paragraph 0023; 0028-0033
(2020/06/05)
-
- Iron-catalyzed selective production of methyl esters from aldehydes
-
A process for making methyl esters in high yields is provided. The process comprises contacting aliphatic or aromatic aldehydes and methanol with an iron catalyst, to catalyze the dehydrogenative coupling between aliphatic or aromatic aldehydes and methanol. The reaction is highly selective (99.9%) toward the formation of methyl esters over homoesters and alcohols and operates at temperatures of less than 100° C. for 2-8 hours.
- -
-
Page/Page column 4-6
(2020/04/01)
-
- Process for the production of esters
-
A process for making methyl esters in high yields. The process comprises contacting aliphatic or aromatic aldehydes and methanol with a homogeneous dimeric ruthenium catalyst, to catalyze the dehydrogenative coupling between aliphatic or aromatic aldehydes and methanol. The reaction is highly selective (99.9%) toward the formation of methyl esters over homoesters and alcohols and operates at temperatures of less than 100° C. for 2-8 hours.
- -
-
Page/Page column 7
(2020/03/18)
-
- Palladium/IzQO-Catalyzed coordination-insertion copolymerization of ethylene and 1,1-disubstituted ethylenes bearing a polar functional group
-
Coordination-insertion copolymerization of ethylene with 1,1-disubstituted ethylenes bearing a polar functional group, such as methyl methacrylate (MMA), is a long-standing challenge in catalytic polymerization. The major obstacle for this process is the huge difference in reactivity of ethylene versus 1,1-disubstituted ethylenes toward both coordination and insertion. Herein we report the copolymerization of ethylene and 1,1-disubstituted ethylenes by using an imidazo[1,5-a]quinolin-9-olate-1-ylidene-supported palladium catalyst. Various types of 1,1-disubstituted ethylenes were successfully incorporated into the polyethylene chain. In-depth characterization of the obtained copolymers and mechanistic inferences drawn from stoichiometric reactions of alkylpalladium complexes with methyl methacrylate and ethylene indicate that the copolymerization proceeds by the same coordination-insertion mechanism that has been postulated for ethylene.
- Yasuda, Hina,Nakano, Ryo,Ito, Shingo,Nozaki, Kyoko
-
supporting information
p. 1876 - 1883
(2018/02/17)
-
- The Pd-catalysed hydromethoxycarbonylation of aliphatic internal alkenes with minimal double bond isomerisation
-
The methoxycarbonylation of internal alkenes by a palladium(II)complex comprising PdCl2, bis(2-methoxyphenyl)phenylphosphine (2) and HCl has been investigated. The results presented herein demonstrate a non-isomerizing Pd-complex for the effective production of internal esters from the corresponding internal aliphatic alkenes. Selectivities of >70% were obtained for the desired internal esters with no signs of catalyst decomposition. The high selectivity for the internal esters is rationalized on the basis of the hemi-lability of the o-methoxy moiety which may assist in ligand dissociation. To the best of our knowledge this is one of the first reported hydromethoxycarbonylation routes to internal esters from their corresponding internal aliphatic alkenes.
- Bredenkamp, Tyler,Holzapfel, Cedric
-
-
- Efficient flow fischer esterification of carboxylic acids with alcohols using sulfonic acid-functionalized silica as supported catalyst
-
Flow Fischer esterification of carboxylic acids using hydroxy-substituted sulfonic acid-functionalized silica (HOSAS) packed into a stainless steel column reactor was investigated. HO-SAS well catalyzed flow esterification of long chain carboxylic acids with methanol within 3min of residence time at 110°C, and the methyl esters were quantitatively obtained. The flow esterification protocol was applied to the synthesis of a variety of esters (19 examples) and scalable synthesis was also successful.
- Furuta, Akihiro,Fukuyama, Takahide,Ryu, Ilhyong
-
p. 607 - 612
(2017/06/19)
-
- Efficient and simple approaches towards direct oxidative esterification of alcohols
-
The present article describes novel oxidative protocols for direct esterification of alcohols. The protocols involve successful demonstrations of both "cross" and "self" esterification of a wide variety of alcohols. The cross-esterification proceeds under a simple transition-metal-free condition, containing catalytic amounts of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)/TBAB (tetra-n-butylammonium bromide) in combination with oxone (potassium peroxo monosulfate) as the oxidant, whereas the self-esterification is achieved through simple induction of Fe(OAc)2/dipic (dipic=2,6-pyridinedicarboxylic acid) as the active catalyst under an identical oxidizing environment. One-pot oxidative esterification: A wide variety of alcohols undergo transition-metal-free (in the presence of oxone/2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)/tetra-n-butylammonium bromide (TBAB)) selective "cross" esterification in moderate to excellent yields (see Figure). The "self" esterification process has however been achieved in the presence of Fe(OAc)2/2,6-pyridinedicarboxylic acid (dipic) as the active catalytic species under a similar oxidizing environment.
- Ray, Ritwika,Jana, Rahul Dev,Bhadra, Mayukh,Maiti, Debabrata,Lahiri, Goutam Kumar
-
supporting information
p. 15618 - 15624
(2016/02/18)
-
- Iridium-catalyzed oxidative methyl esterification of primary alcohols and diols with methanol
-
Oxidative methyl esterification of primary alcohols and diols with methanol was successfully achieved, using acetone as a hydrogen acceptor, under the influence of an iridium complex combined with 2-(methylamino)ethanol (MAE) as catalyst.
- Yamamoto, Nobuyuki,Obora, Yasushi,Ishii, Yasutaka
-
experimental part
p. 2937 - 2941
(2011/05/30)
-
- Carbonic anhydrase inhibitors. Inhibition of the β-class enzymes from the fungal pathogens Candida albicans and Cryptococcus neoformans with branched aliphatic/aromatic carboxylates and their derivatives
-
The inhibition of the β-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic fungi Cryptococcus neoformans (Can2) and Candida albicans (Nce103) with a series of 25 branched aliphatic and aromatic carboxylates has been investigated. Human isoforms hCA I and II were also included in the study for comparison. Aliphatic carboxylates were generally millimolar hCA I and II inhibitors and low micromolar/submicromolar β-CA inhibitors. Aromatic carboxylates were micromolar inhibitors of the four enzymes but some of them showed low nanomolar activity against the fungal pathogenic enzymes. 4-Hydroxy- and 4-methoxy-benzoate inhibited Can2 with KIs of 9.5-9.9 nM. The methyl esters, hydroxamates, hydrazides and carboxamides of some of these derivatives were also effective inhibitors of the α- and β-CAs investigated here.
- Carta, Fabrizio,Innocenti, Alessio,Hall, Rebecca A.,Mühlschlegel, Fritz A.,Scozzafava, Andrea,Supuran, Claudiu T.
-
body text
p. 2521 - 2526
(2011/05/15)
-
- A Simple, efficient, green, cost effective and chemoselective process for the esterification of carboxylic acids
-
Carboxylic acids have been esterified under mild and solvent-free conditions in high yield and purity using the green reagents, dimethyl carbonate and diethyl carbonate, under acid catalysis. The present methodology is free of the disadvantages of base catalysis described earlier, such as high temperatures, use of autoclaves, use of the expensive DBU as base in stoichiometric amounts and the carbonate as solvent. High chemoselectivity is observed in the case of hydroxybenzoic acids.
- Rekha,Ramani, Modukuri V.,Ratnamala,Rupakalpana, Vempati,Subbaraju, Gottumukkala V.,Satyanarayana, Chava,Rao, C. Someswara
-
experimental part
p. 769 - 773
(2010/04/22)
-
- Oils with heterogenous chain lengths
-
Oils containing a triacylglycerol polyol ester and a non-glycerol polyol ester are described, as well as methods of making such oils. Methods for improving lubrication properties of a vegetable oil also are described.
- -
-
Page/Page column 5-6
(2008/06/13)
-
- Novel Preparation of α,β-Unsaturated Aldehydes. Benzeneselenolate Promotes Elimination of HBr from α-Bromoacetals
-
Acetalization, α-bromination, nucleophilic phenylselenenylation, oxidative elimination/hydrolysis was investigated as a novel protocol for the α,β-dehydrogenation of aldehydes. Treatment of acetals with bromine in methylene chloride afforded the corresponding α-bromoacetals in 80-90% yields. Nucleophilic phenylselenenylation was then conveniently effected by treatment with benzenese-lenolate generated in situ in dimethyl sulfoxide from diphenyl diselenide, hydrazine and potassium carbonate. Unbranched α-bromoacetals cleanly afforded substitution products whereas β- and γ-branched ones gave substantial amounts of α,β-unsaturated acetals via formal loss of hydrogen bromide. Oxidative elimination/hydrolysis of these mixtures afforded α,β-unsaturated aldehydes in 50-80% overall yields. In the case of tertiary α-bromoacetals, treatment with benzeneselenolate afforded only dehydrobromination products as mixtures of isomers. The presence of at least a catalytic amount of the organoselenium reagent was found to be crucial for olefin formation. A SET-mechanism, involving benzeneselenolate-induced electron transfer to the halide, loss of bromide ion, and hydrogen atom or proton/electron was proposed for the benzenselenolate-promoted elimination reaction. Experiments designed to trap carbon-centered radicals in intramolecular cyclization or ring-opening reactions failed to provide any evidence for free-radical intermediates.
- Vasil'ev, Andrei,Engman, Lars
-
p. 2151 - 2162
(2007/10/03)
-
- Enantioselectivity of the transfer of hydrogen atoms to acyclic prochiral carbon-centred radicals using chiral tin hydrides
-
Racemic α-bromo esters 2 have been reduced via prochiral radicals 5 with low to moderate enantioselectivities using chiral tin hydrides 1 with a stereogenic tin atom containing chiral 2-[(1-dimethylaminoalkyl)phenyl] ligands. The tin hydrides 1 were mixtures of diastereomers. It could be shown that the minor diastereomer of tin hydrides 1a and 1b reacts with good enantioselectivity whereas the major diastereomer reacts almost unselectively. The observed enantioselectivities are also strongly influenced by steric effects of the substituents attached to the radical centre.
- Schwarzkopf, Kay,Blumenstein, Michael,Hayen, Ahlke,Metzger, Jürgen O.
-
p. 177 - 181
(2007/10/03)
-
- Process for the preparation of carboxylic acid methyl esters
-
A process for the preparation of methyl carboxylates by the reaction of mono or dicarboxylic acids having more than 5 carbon atoms and methanol in the presence of acidic catalysts at temperatures from 100° to 150° C. and below the boiling point of the carboxylates being produced.
- -
-
-