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Search for "transesterification" in Full Text gives 105 result(s) in Beilstein Journal of Organic Chemistry.
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
Phosphinate-containing heterocycles: A mini-review
Beilstein J. Org. Chem. 2014, 10, 732–740, doi:10.3762/bjoc.10.67
- developed by Pirat and coworkers. Scheme 24 shows the synthesis of a H-phosphinate intermediate 59 in 65% yield via the reaction between the imine 57 of the racemic 1,2-diphenylethanolamine with benzaldehyde and methyl phosphinate (58) followed by the cyclization through a base catalyzed transesterification
- synthesized in two steps at room temperature, first, by a nucleophilic attack of methyl hypophosphite on oxazolidine 60 followed by an intramolecular cyclization, this time without base catalyzed transesterification. The authors explained this difference of reactivity by the Thorpe–Ingold effect [38]. Indeed
- (trimethylsiloxy)phosphine. Diastereoselective ring-closing metathesis. 2-Ketophosphonate/benzene annulation. Tandem Kabachnik–Fields/transesterification reaction. Tandem Kabachnik–Fields/transesterification reaction with oxazolidine. Acknowledgements This material is based in part upon work supported by the
Synthesis of complex intermediates for the study of a dehydratase from borrelidin biosynthesis
Beilstein J. Org. Chem. 2014, 10, 634–640, doi:10.3762/bjoc.10.55
- conditions. As the presence of a methyl ester would prevent the selective introduction of one thioester into 5a by saponification–thioesterification, we planned transesterification from a suitably activated carboxylic acid derivative 8. Alternatively, direct introduction into 11 with appropriate SNAc
- thioester building blocks was planned for the synthesis of 6a and 6b. Starting from aldehyde 11, a common precursor for all molecules required in this study, aldol reaction and following transesterification should lead to thioester 8. The bismethyl esters 7a and 7b as well as the SNAc thioesters 6a and 6b
- 17a and 17b with HSNAc and triethylamine in DMF, they underwent clean transesterification furnishing SNAc thioesters 18a and 18b in 70% combined yield [20] (Scheme 3). With the mixture of 18a and 18b in hand, we turned to the mild removal of the protection groups. For TBS cleavage, we focused on
The regulation and biosynthesis of antimycins
Beilstein J. Org. Chem. 2013, 9, 2556–2563, doi:10.3762/bjoc.9.290
- acyltransferase, which catalyses a transesterification reaction resulting in the formation of a C-8 acyloxyl moiety and is responsible for generating the chemical diversity at R1 (Figure 1). AntB likely performs this reaction after assembly of the dilactone core, as wild-type levels of biosynthetic intermediates
Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water
Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196
- the mutifunctionalized product 19 as a single isomer. The stereochemistry of 19 could be presumably assigned by considering the 1,5-hydrogen shift mechanism (entry 5) [17]. The reaction of alkene 10 bearing a methyl ester moiety gave γ-lactone 20 by intramolecular transesterification with a tertiary
A reductive coupling strategy towards ripostatin A
Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175
- the TBS group were removed first, the free hydroxy group would undergo elimination, it seemed likely that both deprotections would proceed at ambient temperature, which might circumvent this issue. Transesterification of methyl ester 45 to TMSE ester 64 proceeded in good yield, and following an
1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions
Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73
- carbon dioxide transfer in the formation of ketoacetates [46][47] and carboxylation of epoxides [48]. Some of us have recently reported a green application of BMIM-2-CO2, highlighting its efficiency for the conversion of raw glycerol to glycerol carbonate by transesterification [49]. More recently, this
- concept was extended to the synthesis of aliphatic polycarbonates, involving the transesterification of DMC with linear alkane diols under solvent-free conditions, and based on a two-step polymerization process [50]. The high reactivity of imidazolium-2-carboxylates can be explained by their facile
- theoretical and experimental values of Mn, despite a complete conversion. These deviations, which are significant in some cases, can be explained by a backbiting process and the involvement of redistribution reactions (inter- and intra-transesterification reactions) [55]. In all cases, the values of both
Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids
Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56
- -propylene oxide with imidazole or 1,2,4-triazole. Lipase-catalyzed transesterification of alcohols with vinyl acetate resulted in kinetic enantiomers resolution. Separated (S)-enantiomers of (+)-1-(1H-imidazol-1-yl)propan-2-ol and (+)-1-(1H-1,2,4-triazol-1-yl)propan-2-ol were quaternized with alkyl bromides
- ). Next, these compounds were used as a new type of substrate in lipase-catalyzed transesterification, yielding both enantiomers with good optical purity. The syntheses of the secondary alcohols (±)-3a and (±)-3b were accomplished by the addition of imidazole (2a) or 1,2,4-triazole (2b) to 1,2-propylene
- ) and two immobilized enzymes (Novozym SP 435, Amano PS-IM), were chosen for the transesterification studies. The screenings were performed with a 5-fold molar excess of vinyl acetate as an irreversible acyl donor at ambient temperature. The selection of a proper solvent is a significant factor in
From bead to flask: Synthesis of a complex β-amido-amide for probe-development studies
Beilstein J. Org. Chem. 2013, 9, 260–264, doi:10.3762/bjoc.9.31
- this reaction was significantly lower, less than 50%, compared to the reaction to produce 14, and we observed some transesterification of the methyl ester with butanol to produce a mixture of 27 and the butyl ester of 27 as the major products (not shown). We thus turned to using Oxone, and
Alternaric acid: formal synthesis and related studies
Beilstein J. Org. Chem. 2013, 9, 166–172, doi:10.3762/bjoc.9.19
- selectivity in 65% yield (Scheme 3). Ichihara’s aldehyde intermediate could be intercepted in three additional steps, in high overall yield. Simultaneous cleavage of the silyl ether and transesterification from the tert-butyl to the methyl ester in 6 was effected by warming in acidic methanol. Subsequent
Organocatalytic asymmetric allylic amination of Morita–Baylis–Hillman carbonates of isatins
Beilstein J. Org. Chem. 2012, 8, 1241–1245, doi:10.3762/bjoc.8.139
- realized with Zn powder in acetic acid to produce compound 5, albeit in modest yield [34][35], whose absolute configuration has been determined by X-ray analysis [36]. The removal of the O-TBS unit proceeded efficiently in the presence of hydrofluoric acid, and an intramolecular transesterification process
An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines
Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93
- of the triazine ring, thereby preventing the desired cycloaddition. In addition to the amide linkage of the alkyne dienophiles, transesterification of 8a with alkynyl alcohols led to tethered alkynyl esters as cycloaddition precursors 17a and 17b in good yields (Scheme 9). Various catalysts for the
- transesterification reaction were screened. Boronic acid [91] and indium(III) iodide [92] yielded no transesterification product with propargyl alcohol, while Ti(OiPr)4 [93] gave only a trace of the desired product, with mostly detosylation resulting. Otera’s catalyst [94] proved to be optimal, giving cycloaddition
- triazines. One-pot amidation/cycloaddition of triazine ester 8a. Amidation/cycloaddition forming α-carbolines 14. Intramolecular hydrogen bonding prevents IEDDA cycloaddition of 14b. Preparation of unprotected triazine 15, and its lack of reactivity in cycloadditions. Transesterification and subsequent
Synthesis and antiviral activities of spacer-linked 1-thioglucuronide analogues of glycyrrhizin
Beilstein J. Org. Chem. 2012, 8, 705–711, doi:10.3762/bjoc.8.79
- diphenylmethyl ester group with TFA/anisole (as carbocation scavenger), giving the monoacid derivatives 10 and 11 in 75% and 89% yield, respectively. Subsequent transesterification of 10 and 11 with methanolic NaOMe afforded the deacetylated methyl ester glucuronide derivatives 12 and 14, respectively, which
Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols
Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139
- confirms the allylic SN1 mechanism for the present methodology [44]. The high chemoselectivity guaranteed by the gold catalysts is worthy of note, as it channels the reaction toward the allylic alkylation mechanism without any contamination deriving from transesterification reactions. This evidence is
Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan
Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47
- outcome was obtained using NIS/TfOH activation of thioglycoside donor 17 to furnish disaccharide 26 in 72% yield. Selective deacetylation of 26 was achieved by acidic transesterification using 3% AcCl in MeOH/CH2Cl2 to give the secondary alcohol 27 in 73% yield. Mannosylation of 27 using donor 21 under
About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations
Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131
- ADMET polymerizations were studied in detail. The isomerization reactions were investigated by degradation of the prepared polyesters via transesterification with methanol, yielding diesters. These diesters, representing the repeat units of the polyesters, were then quantified by GC-MS. Keywords: ADMET
- room temperature. The crude product was purified by precipitation into cold methanol. Final polymer molecular weights were determined after precipitation with the above mentioned GPC system. Transesterification of the obtained polymers (P1-P26) and GC-MS analysis The respective polymer (30 mg), excess
Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine
Beilstein J. Org. Chem. 2010, 6, 823–829, doi:10.3762/bjoc.6.97
- reaction was observed (Table 2, entries 2 and 3, respectively) indicating that the racemization was slower than the transesterification at these catalyst loadings. An increase in the selectivity was observed when the amount of acyl donor was decreased, however this also coincided with deceleration of the
Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride
Beilstein J. Org. Chem. 2010, 6, 748–755, doi:10.3762/bjoc.6.94
- chemoselective reduction of the oxo-group, occasionally with subsequent transesterification and the formation of the alkoxy-modified β-hydroxyesters. γ-Oxoesters react chemoselectively with sodium borohydride to produce the corresponding γ-hydroxyesters [1][2][17][23][24][25][26][27] (sometimes in the form of γ
Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length
Beilstein J. Org. Chem. 2010, 6, No. 67, doi:10.3762/bjoc.6.67
- range of 1.3–1.7 for the series of star polymers prepared, which is moderate. These values can be explained by the non-monodisperse multifunctional initiator (PDI: 1.9–2.0), although transesterification/cyclization reactions during the synthesis cannot be completely excluded. A detailed account of the
Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al2O3 under inspection
Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7
- stoichiometric or catalytic reagent: transesterification of vegetable oils [27], hydrolysis reactions [29], O-methylation of phenol [62], and Michael reactions [63]. In conclusion, it appears that a KF content of 30–40 wt % is sufficient for a mechanochemically initiated conversion of 1 and 2 yielding 3
N-acylation of ethanolamine using lipase: a chemoselective catalyst
Beilstein J. Org. Chem. 2009, 5, No. 10, doi:10.3762/bjoc.5.10
- (triacyl glycerol hydrolases EC 3.1.1.3) catalyze hydrolysis, esterification, transesterification, thioesterification, amidation, epoxidation etc. [5][6][7][8][9][10]. The use of immobilized lipases is on the rise, as these work well with non-aqueous media [11]. Apart from the convenient handling, these
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