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Search for "transesterification" in Full Text gives 100 result(s) in Beilstein Journal of Organic Chemistry.
Phosphonic acid: preparation and applications
Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219
- phosphonate involves trialkyl phosphite, the subsequent dealkylation of dialkyl phosphonate under mild conditions was of a great importance. The group of C. E. McKenna reported in 1977 the use of bromotrimethylsilane as a reagent that permitted an efficient transesterification of dialkyl phosphonate to bis
- was almost quantitative. Other studies indicated that this reaction can be also applied to diisopropyl phosphonate, or di-tert-butyl phosphonate leading to the conclusion that all dialkyl phosphonates can be dealkylated by the transesterification followed by a methanolysis or hydrolysis subsequent
Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds
Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218
- involving Michael addition followed by intramolecular transesterification. Remarkably, the resulting bridged products 12 have reversed regiochemistry as compared to the earlier-described cycloadducts 5 (Scheme 1). It should also be pointed out that all of these products were formed as single 10-endo
- ]. Keeping this in mind we decided to test the reactivity of ketazinones 17 that were obtained via condensation of cyclohexanediones 8 with hydrazone of acetophenone. We anticipated the formation of spirolactones 20 in this process, resulting from intramolecular transesterification involving the enol moiety
Mechanochemical synthesis of small organic molecules
Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186
- ) technique for the synthesis of dialkyl carbonates [90]. Using potassium carbonate, alkyl halide and 2 equiv of phase-transfer catalyst 18-crown-6 yielded dialkyl carbonate in 74%. However, in absence of 18-crown-6 the yield was only 2% at 17 h (Scheme 20). Transesterification is a synthetic approach mostly
- being used for making higher homologous esters from the simpler ones. Ranu and co-workers developed simple method for transesterification under mechanomilling [91]. The mixture of ester and alcohols were adsorbed on the surface of basic alumina and followed by milling of the materials for 2–3 h led to
- dialkyl carbonates [90]. Mechanochemical transesterification reaction using basic Al2O3 [91]. Mechanochemical carbamate synthesis [92]. Mechanochemical bromination reaction using NaBr and oxone [96]. Mechanochemical aryl halogenation reactions using NaX and oxone [97]. Mechanochemical halogenation
The chemistry and biology of mycolactones
Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159
Synthesis of oligonucleotides on a soluble support
Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134
- commercially available building blocks turned out to be too hydrophobic to allow precipitation of the support-bound oligonucleotides from MeOH. The 1-methoxy-1-methylethyl group could be removed quantitatively as a dimethyl acetal of acetone upon acid-catalyzed transesterification in MeOH. The 3'-terminal
An improved preparation of phorbol from croton oil
Beilstein J. Org. Chem. 2017, 13, 1361–1367, doi:10.3762/bjoc.13.133
- crystallization step. A solution for these issues is provided, suggesting that the poor-reproducibility of croton oil-based anti-inflammatory assays are the result of poor quality and/or inconsistent composition of croton oil. Keywords: croton oil; diterpenoids; natural products; phorbol; transesterification
- of phorbol from the transesterification reaction mixture, a viscous oil for the presence of glycerol, that requires extended periods (four weeks according to ref. [6]). Furthermore, the unstable ethanol solvate has to be transformed into a more stable hydrate by recrystallization from hot water, a
- , problematic for the multigram isolation of phorbol due to the extensive handling of the toxic croton oil and the ultra-toxic mixture of phorbol diesters obtained in the acidic transesterification step. Furthermore, the tritylation of the crude mixture of phorbol diesters suffered from interference from
First total synthesis of kipukasin A
Beilstein J. Org. Chem. 2017, 13, 855–862, doi:10.3762/bjoc.13.86
- ’-transesterification is inevitable to occur in nucleosides [19][20][21]. The synthetic route would be lengthy and cumbersome. Therefore, a practical total synthesis is in high demand to facilitate the preparation of other kipukasins and their analogues. The retrosynthetic analysis is shown in Figure 2 (path b
- . Various spectral analyses (NMR, HPLC) showed no evidence that 2,3-O-transesterification occurred during the esterification reaction. After cleavage of the acetonide group with acetic acid/acetic anhydride/H2SO4, the key glycosylation donor 16 was obtained in 74% yield as a mixture of isomers (α/β = 1:8
Cyclodextrins tethered with oligolactides – green synthesis and structural assessment
Beilstein J. Org. Chem. 2017, 13, 779–792, doi:10.3762/bjoc.13.77
- oligomers with odd number of monomer units could be observed as well. These oligomer species with odd number of lactates resulted from intramolecular and/or intermolecular transesterification reactions and are in lower amount, when compared with the oligomers containing even number of monomers. This
- signifies that the predominance of transesterification is rather low in the employed reaction conditions. The presented spectrum was measured directly from the HPLC collected fraction with rather low concentration of products, thus resulting in a poor spectrum quality. The f7 fraction (Figure 1 – LC–ELSD
- number of lactate monomer units. These species could be formed as a result of transesterification reactions (intra- or intermolecular), which may occur in the melt reaction system. The presence of PLA homopolymers was also observed, their corresponding m/z being calculated by the following equation: m/z
Synthesis of structurally diverse 3,4-dihydropyrimidin-2(1H)-ones via sequential Biginelli and Passerini reactions
Beilstein J. Org. Chem. 2017, 13, 54–62, doi:10.3762/bjoc.13.7
- performed first, in order to avoid undesired transesterification reactions (of the Passerini product) due to the acidic conditions of the Biginelli reaction [33]. A general challenge, which has to be faced in this context, is the choice of solvent and the selection of bifunctional components (which can
Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification
Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268
- homogeneous conditions and their subsequent utilization in transesterification and amidation processes by the reaction telescoping approach [12]. Similarly, the group of Brown reported on the oxidative esterification and amidation of aldehydes in undivided microfluidic electrolysis cells mediated by
- reaction setup [22][23][24]. An integrated flow system for the synthesis of biodiesel employing an uninterrupted sequence of two fixed-bed reactors packed with a supported acid for esterification of free fatty acids and with an immobilized imidazolidene catalyst for transesterification has been recently
Synthesis of medronic acid monoesters and their purification by high-performance countercurrent chromatography or by hydroxyapatite
Beilstein J. Org. Chem. 2016, 12, 2145–2149, doi:10.3762/bjoc.12.204
- ] and medronic acid [30] can also be used as the starting material for the synthesis of mixed tetraesters. If the starting point is a tetraester of medronic acid, several routes can be taken, for example transesterification [31]. In addition, after dealkylation, the corresponding triester can be
Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates
Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181
- Maurizio Selva Alvise Perosa Sandro Guidi Lisa Cattelan Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Via Torino, 155 – Venezia Mestre, Italy 10.3762/bjoc.12.181 Abstract The use of ionic liquids (ILs) as organocatalysts is reviewed for transesterification
- reactions, specifically for the conversion of nontoxic compounds such as dialkyl carbonates to both linear mono-transesterification products or alkylene carbonates. An introductory survey compares pros and cons of classic catalysts based on both acidic and basic systems, to ionic liquids. Then, innovative
- green syntheses of task-specific ILs and their representative applications are introduced to detail the efficiency and highly selective outcome of ILs-catalyzed transesterification reactions. A mechanistic hypothesis is discussed by the concept of cooperative catalysis based on the dual (electrophilic
(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers
Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48
- transformation is initiated by a Michael addition of 158 to alkylidene azlactone 159, followed by a Mannich reaction and finally transesterification. The same year, Yuan and co-workers reported the double Michael reaction between 160 and alkylidene azlactone 161 to produce the spiro-fused cyclohexanone/5
Diastereoselective synthesis of new O-alkylated and C-branched inositols and their corresponding fluoro analogues
Beilstein J. Org. Chem. 2016, 12, 353–361, doi:10.3762/bjoc.12.39
- several methods of acetylation were carried out on myo-14, which was used as model. The best results for the acetylation of the tertiary alcohol in good yield was obtained with the transesterification method using isopropenyl acetate as acylating agent and p-toluenesulfonic acid as catalyst at 80 °C for 2
Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation
Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228
- ) stereogenic center by means of a Mitsunobu reaction, followed by transesterification of the ester to give 4 (Scheme 1). (S)-Isopulegone was prepared by Jones oxidation of (−)-isopulegol following a reported procedure [14]; but on a large scale we have observed that a partial loss of the optical purity of the
Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers
Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174
- transesterification reactions, ‘activated’ esters are usually employed in order to make the reactions irreversible thanks to the release of alcohols that are poor nucleophiles (halogenated derivatives of ethanol, vinyl or isopropenyl alcohol) [13][14][15]. This has been also the case with several reports on the use
First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine
Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322
- Lipozyme TL IM were established as optimal biocatalysts for the enantioselective transesterification when suspended in 30 equiv of vinyl acetate as the acyl donor, methyl tert-butyl ether (MTBE) as co-solvent, and carried out at 25 °C, with agitation speed of the magnetic stirrer arranged at 500 rpm, and
- most promising catalyst only on the basis of single random results obtained from the analysis of the reaction mixtures. By virtue of the importance of enzyme selection, and to find the most suitable catalyst for the transesterification of racemic alcohol (±)-3 as well as to provide better insight into
- -activated esters (i.e., ethyl acetate, methyl acetate), and anhydrides (i.e., acetic acid anhydride, succinic acid anhydride) are most commonly used. Unfortunately, there are several drawbacks of incorporating the above-mentioned reagents into transesterification processes, i.e., trifluoroethyl esters are
A green approach to the synthesis of novel phytosphingolipidyl β-cyclodextrin designed to interact with membranes
Beilstein J. Org. Chem. 2014, 10, 2654–2657, doi:10.3762/bjoc.10.278
- with a promising yield. Keywords: fatty ester; green chemistry; lipase; mono-substituted amphiphilic cyclodextrins; peptide Coupling; solvent-free medium; transesterification; Introduction Cyclodextrins (CDs) are sustainable compounds which are particularly interesting in the frame of pharmaceutical
- transesterification with the corresponding fatty ester, which may lead to bicatenar amphiphilic CDs. At the same time, the two remaining secondary alcohols might increase the solubility of the modified CD compounds. The aim of this work is to synthesize new bicatenar CDs using green methods described for the first
- enzymatic transesterification, sphingolipid myelin analogues bearing CD as polar heads were synthesized to interact with ceramids of brain membranes. Results and Discussion Insertion of the spacer A procedure for the preparation of compound 1 has already been described in previous articles [8]. The reaction
Regio- and stereoselective synthesis of new diaminocyclopentanols
Beilstein J. Org. Chem. 2014, 10, 2513–2520, doi:10.3762/bjoc.10.262
- [29]. The treatment of the corresponding acetates 4 with mesyl chloride and subsequent transesterification of mesylated substrates 5 resulted in the formation of 6a,b. Epoxides 3 and 6 were identified by 1H NMR data [28]. Morpholine (7a), 2-methyl-1H-imidazole (7b), N-acetylpiperazine (7c) and 9H
Synthesis and immunological evaluation of protein conjugates of Neisseria meningitidis X capsular polysaccharide fragments
Beilstein J. Org. Chem. 2014, 10, 2367–2376, doi:10.3762/bjoc.10.247
- of the hemiacetal under these reaction conditions. Compound 9 was subjected to Zemplén transesterification with NaOMe in methanol to afford alcohol 10, and the hydrogenolytic removal of the remaining protective groups furnished the spacer-linked monomer 1 in excellent yield (Scheme 2). Chemical
Relay cross metathesis reactions of vinylphosphonates
Beilstein J. Org. Chem. 2014, 10, 1933–1941, doi:10.3762/bjoc.10.201
- ) failed to react at all with methyl acrylate under similar conditions, even with higher catalyst loading and extended reaction times. Initially, the synthesis of the allyl vinylphosphonate esters was achieved using a transesterification reaction catalysed by tetra n-butylammonium iodide (TBAI) (Scheme 5
- diallyl phosphonate esters. Finally, THP-vinylphosphonate 5 was subjected to transesterification by reaction with 20 mol % of TBAI and 5 equivalents of allyl bromide in toluene solution and heating in a microwave reactor for 5.5 hours. The reaction proceeded to 96% conversion and gave 1:1.8 ratio of mono
- salt with 5 equivalents of allyl bromide at room temperature for two days gave the mono-allyl phosphonate in 71% isolated yield (two steps). It is probable that this transesterification reaction can be further optimized to both increase yields and decrease the reaction time. Conclusion The experiments
Clicked and long spaced galactosyl- and lactosylcalix[4]arenes: new multivalent galectin-3 ligands
Beilstein J. Org. Chem. 2014, 10, 1672–1680, doi:10.3762/bjoc.10.175
- dipolarophile-on-the-sugar approach [44]. The deprotection of compounds 9 and 13 from the acetyl groups was carried out by a transesterification reaction in the presence of CH3ONa in CH3OH at room temperature according to the standard Zemplén procedure. Complete deacetylation was achieved in 1 hour, as
Atherton–Todd reaction: mechanism, scope and applications
Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117
cis–trans Isomerization of silybins A and B
Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105
- propose a mechanism for the cis–trans-isomerization processes. Results and Discussion Chemistry In our previous work on the enzymatic kinetic resolution of silybin [4][5], BF3∙OEt2 in EtOAc was found to catalyze the transesterification of silybin to yield not only 23-O-acetylsilybin (2, ca. 90%), but two
- /trans-isomer in the mixture from 1:4 to 1:2. Deacetylation of cis-23-O-acetylsilybins All pure cis-silybins were obtained as their C-23 acetates. The deacetylation proved to be rather difficult, as both acidic and basic hydrolysis as well as mild transesterification (NaOMe, MeOH) failed and/or resulted
Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism
Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70
- , nitrile), acetylacetone, and nitroacetates with trialkyl orthoformate 1 (Scheme 1). Transesterification can be avoided if 1 bears the same alkyl group as 2. The reaction can be carried out with or without Lewis acid catalysis [2]. Pyrazoles constitute a large group of pharmacologically active compounds
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