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Search for "microwave irradiation" in Full Text gives 242 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Experimental and theoretical investigations into the stability of cyclic aminals
Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221
- structures with various applications in medicinal chemistry [20][21]. The syntheses of tetrahydroquinazolines are well described using different approaches: the majority relies on the direct α-amination of o-aminobenzaldehydes with heating or microwave irradiation [22][23][24], by condensation of diamines
Stereoselective synthesis of fused tetrahydroquinazolines through one-pot double [3 + 2] dipolar cycloadditions followed by [5 + 1] annulation
Beilstein J. Org. Chem. 2016, 12, 2204–2210, doi:10.3762/bjoc.12.211
- microwave irradiation at 115 °C for 25 min. Upon the completion of the reaction as monitored by LC–MS, maleimide 6 (1.0 mmol) was added to the reaction mixture and then heated by microwave irradiation at 125 °C for 25 min. The concentrated reaction mixture was isolated on a semi-preparative HPLC with a C18
Microwave-assisted cyclizations promoted by polyphosphoric acid esters: a general method for 1-aryl-2-iminoazacycloalkanes
Beilstein J. Org. Chem. 2016, 12, 2026–2031, doi:10.3762/bjoc.12.190
- sensitive substrates. Results and Discussion The ω-arylaminonitrile precursors were obtained by reaction of the corresponding ω-halonitrile and arylamines, as previously reported by our group [44]. We examined first the cyclization of 4-(p-tolylamino)butyronitrile (1a) with PPE under microwave irradiation
Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines
Beilstein J. Org. Chem. 2016, 12, 1812–1825, doi:10.3762/bjoc.12.171
- high temperature and pressure, they decompose very rapidly. Alternatively, the chalcones 2 can be isolated following the conventional synthetic route, namely the reaction of equimolar amounts of the azulene-carbaldehyde with 2-acetylpyridine in ethanol, at room temperature or, by microwave irradiation
- reacted with excess ammonium acetate in acetic acid under microwave irradiation at 160 °C for 5 minutes. The target terpyridines are isolated in satisfactory yields varying from 42% in the case of compound 4a to 35% for 4b, respectively. If the reaction is performed under refluxing conditions for 4–6
Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction
Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158
- chemical transformations under microwave irradiation [17], affording the cycloadducts 3a,b in very good yields (76–81%) after irradiating a THF solution of 1 and 2 at 150 °C during 4 hours. The reduction of the ketone group in 3 with NaBH4 produced alcohols 4 and 5 in excellent yields and a ratio of about
Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates
Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121
- afforded the desired isoindolin-1-one-3-phosphonates 60 in only 14% yields after five days. Noteworthy, the treatment of the same reaction mixture under microwave irradiation at 90 °C gave the expected product 60 in 77% yields after several minutes. Subsequently, the isoindolin-1-one-3-phosphonates 60 were
- phosphorylated quinazoline 203 through reductive elimination. A silver-catalyzed three-component reaction of α-isocyanophosphonates 206, ketones 205 and amines 204 under microwave irradiation to afford (2-imidazolin-4-yl)phosphonates 210 has recently been reported (Scheme 43) [81]. The yields of the products
- corresponding products 271 and 272 were isolated in 52–61% yields and their nOe analysis revealed the geometry of the alkene bonds to be E . A tandem 1,4–1,2 addition of dimethyl trimethylsilyl phosphite (DMPTMS, 273) to diazaheterocyclic compounds under microwave irradiation in acidic medium led to
Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups
Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118
- sample of 5b afforded compound 15b in 45% yield as a single isomer. These results were obtained employing microwave irradiation (400 W) that allowed considerably shorter reaction times, however, the yields were not strongly influenced by this modification. From both product diastereomers crystals
Enabling technologies and green processes in cyclodextrin chemistry
Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30
- CD derivatives. Several examples of sonochemical selective modification of native α-, β- and γ-CDs have been reported including heterogeneous phase Pd- and Cu-catalysed hydrogenations and couplings. Microwave irradiation has emerged as the technique of choice for the production of highly substituted
Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study
Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28
- to isolate the benz[f]indenes 5a and 6a, in a relative 2:1 ratio and a poor global yield (34%). We next tested the same and similar processes in a microwave apparatus. As presumed, conversions of a series of acetal-fulvenes 3a–f under 120 W microwave irradiation at 120 °C in DMSO required much
- present cases with the formal β-elimination of a methanol or ethanol molecule. These results show that non-cyclic acetalic units are as effective as the cyclic ones on achieving the conversion of acetal-fulvenes into the corresponding benz[f]indenes under microwave irradiation. Computational study With
Efficient synthetic protocols for the preparation of common N-heterocyclic carbene precursors
Beilstein J. Org. Chem. 2015, 11, 2318–2325, doi:10.3762/bjoc.11.252
- derivatives, whereas the use of triethyl orthoformate under microwave irradiation was most appropriate for the fast and efficient synthesis of imidazolinium salts. This strategy was applied to the synthesis of six common N-heterocyclic carbene precursors, namely, 1,3-dimesitylimidazolium chloride (IMes·HCl
- toward completion. In 2006, we found that microwave irradiation allowed to dramatically reduce the reaction time from hours to minutes, while affording very high yields of pure products [66]. We have applied this procedure to the synthesis of a wide range of cyclic amidinium salts differing by their ring
- under microwave irradiation was most appropriate for the fast and efficient synthesis of imidazolinium salts. With the possible exception of a monomodal microwave reactor, all the equipment and glassware needed to carry out the syntheses outlined in this report are widely available in chemical
Easy access to heterobimetallic complexes for medical imaging applications via microwave-enhanced cycloaddition
Beilstein J. Org. Chem. 2015, 11, 2202–2208, doi:10.3762/bjoc.11.239
- ” reaction, has been applied to the synthesis of a range of triazole-linked porphyrin/corrole to DOTA/NOTA derivatives. Microwave irradiation significantly accelerates the reaction. The synthesis of heterobimetallic complexes was easily achieved in up to 60% isolated yield. Heterobimetallic complexes were
- future use of radioactive isotopes possessing short life times (e.g. Cu2+ and In3+). Microwave irradiation, known to accelerate the polarization of the starting materials to promote the reactions, was investigated. A mixture of azidocorrole 8a, Gd propargyl DOTA 10a, CuI, DIPEA and DMF were irradiated in
Half-sandwich nickel(II) complexes bearing 1,3-di(cycloalkyl)imidazol-2-ylidene ligands
Beilstein J. Org. Chem. 2015, 11, 2171–2178, doi:10.3762/bjoc.11.235
- using a convenient procedure where nickelocene, the NHC·HBF4 salts, and [Et4N]Cl were heated in THF using microwave irradiation. The resulting [NiCl(Cp)(NHC)] complexes are air- and moisture stable in the solid state, and represent two new members of this valuable and practical class of nickel catalysts
- obtained from Sigma-Aldrich and sparged with argon before use. [Et4N]Cl was purchased from Alfa Aesar and dried by heating under vacuum. Reactions under microwave irradiation were carried out using a Biotage apparatus in crimp-cap microwave vials equipped with magnetic stirrer bars. NMR spectra were
Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles
Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219
- Abstract The reaction of α-azidochalcones with carboxylic acids has been investigated resulting in the formation of α-amido-1,3-diketones under microwave irradiation via in situ formation of 2H-azirine intermediates. An interesting reaction is described wherein, with trifluoroacetic acid at lower
- (34%) was noticed with undesirable side products. Due to operational simplicity and efficiency, microwave irradiation in organic synthesis has become more popular as an environmental friendly way [30][31][32]. Thus, to increase the product yield, the investigation was continued by treatment of α
- microwave oven. The vial was sealed with a pressure cap and subjected to microwave irradiation. The irradiation was programmed between 100–200 °C, 120 W, 5 bar, for 5 min depending on the boiling point/melting point of the respective carboxylic acids. The reaction was monitored by TLC using petroleum ether
Synthesis of constrained analogues of tryptophan
Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216
- -acetamidoacrylate (2) and its congeners with cyclic/acyclic dienes and azadienes occur under conventional heating or microwave irradiation [24]. Moreover, the use of titanium tetrachloride as Lewis acidic promoter has been reported [25]. Finally, simple functionalization reactions of indoles with 2 are reported in
Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis
Beilstein J. Org. Chem. 2015, 11, 1809–1814, doi:10.3762/bjoc.11.196
- influence of the ITent ligands in the hydration of nitriles promoted by monogold species. The reactions were conducted in a 1:1 mixture THF/water and heated at 140 °C under microwave irradiation [60]. Low catalyst loadings were employed in order to observe the differences between the four catalysts studied
The facile construction of the phthalazin-1(2H)-one scaffold via copper-mediated C–H(sp2)/C–H(sp) coupling under mild conditions
Beilstein J. Org. Chem. 2015, 11, 1624–1631, doi:10.3762/bjoc.11.177
- quinolin-8-amine was easily removed and recycled by treatment of 3a with hydrazine hydrate and NaOH in EtOH at 120 °C under microwave irradiation (Scheme 4). Both electron-rich and electron-deficient 4-benzylphthalazin-1(2H)-one derivatives were obtained in good yields (4b, 4k). The halo-substituted phenyl
- mmol) and 2 mL EtOH. The resulting mixture was stirred at 120 °C for 1 h under microwave irradiation. The solution was diluted with dichloromethane (30 mL) and washed with 1 M HCl (20 mL, three times). The combined organic layer was washed with NaHCO3 aqueous solution (15 mL) and brine (15 mL). The
Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes
Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150
- irradiation [26][28][29][30] gave rise to α-4a in 33% isolated yield (Table 1, entry 4). A similar result (36% yield) was obtained with a 1:1 octafluorotoluene/ClCH2CH2Cl mixture (Table 1, entry 5). Although microwave irradiation had a positive effect on the cross-metathesis reaction, see examples above
- , carrying out the reaction in a mixture of 1:1 octafluorotoluene/ClCH2CH2Cl under irradiation provided α-4a in only 3% (Table 1, entry 6). Finally, carrying out the reaction in pure ClCH2CH2Cl under reflux furnished the product in a nice 70% isolated yield (Table 1, entry 7), while microwave irradiation
- resulted in decreased yield of 58% (Table 1, entry 8). According to the obtained data in some cases microwave irradiation had a positive effect on the course of the reaction (Table 1, entry 4), whereas as in some cases it had a detrimental effect (Table 1, entries 6 and 8). Currently we do not know how to
A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones
Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137
- method for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones (13 and 21–25) in high yields, from the sequential reaction of readily available 1,3,5-triazinanes 14–19 with 2-hydroxy-1,4-naphthoquinone (20, or lawsone) under microwave irradiation (Scheme 2). The 1,3,5-triazinanes have several
- equivalents of alkyl- or aryl-formimines in situ. The latter compounds may serve as electrophilic agents for aminoalkylation reactions. Our research group also investigated the aminoalkylation of 2-amino-1,4-naphthoquinone with formaldehyde under microwave irradiation to produce two series of N,O-acetals and
- were observed. By elevating the temperature and or changing the solvent some product is formed but the yields were very low. On the other hand, when the reactions were conducted in an equimolar ratio under microwave irradiation (300 Monowave model brand Aanton Paar) in chloroform for 15 minutes at a
New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes
Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132
- amino acids). (S)-4-Isopropyl-2-(naphthalen-1-yl)oxazoline (2) was isolated in a moderate yield from the condensation of the L-valinol with naphthonitrile under microwave irradiation, while the second ligand 1,2-bis[(S)-4-phenyloxazoline]benzene (7) was synthesized from L-(α)-(+)-phenylglycinol under
Matsuda–Heck reaction with arenediazonium tosylates in water
Beilstein J. Org. Chem. 2015, 11, 358–362, doi:10.3762/bjoc.11.41
- ]. In this work, we present a fast, environmentally friendly, low palladium loading method of the Matsuda–Heck arylation of the different alkenes with ADT in water under microwave irradiation. Results and Discussion Our preliminary study was dedicated to the optimization of the alkene arylation
- increase of the reaction temperature to 75 °C (Table 1, entry 2) which gave the desired compound in comparable yield in 20 min. It is well-known that microwave irradiation can significantly reduce the reaction time for a wide range of transformations, including Heck reactions, when compared with standard
- heating [13]. Thus, the aim of our next experiment was the reduction of the reaction time by using microwave irradiation (Table 1, entry 3). By means of this protocol 3aa was obtained with an almost quantitative yield with a reaction time of only 1 min. Carrying out the reaction with 1 mol % of Pd(OAc)2
Cross-dehydrogenative coupling for the intermolecular C–O bond formation
Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13
- synthesized also from aromatic aldehydes, α,β-unsaturated aldehydes, or allylic alcohols in the presence of the DDQ (2,3-dichloro-5,6-dicyanobenzoquinone)/amberlyst-15 system in a methanol/toluene mixture under microwave irradiation [171]. Methyl, ethyl, and isopropyl benzoates were prepared from benzaldehyde
Inclusion of trans-resveratrol in methylated cyclodextrins: synthesis and solid-state structures
Beilstein J. Org. Chem. 2014, 10, 3136–3151, doi:10.3762/bjoc.10.331
- , prepared by either the suspension method or using microwave irradiation, yielded highly amorphous products, evident from their PXRD traces [9]; in this case, the absence of characteristic peaks for RSV and the reduction in the degree of crystallinity of the product were considered as indirect proof of
- , although cellulose acetate was not tested in the present study. Conclusion A variety of methods (physical mixing, kneading, microwave irradiation) of effecting interaction between RSV and three CD hosts (TMA, DMB and TMB) was tested and a combination of thermal analysis and FTIR spectroscopy subsequently
- irradiation products (MP) were prepared by dissolving each PM in the minimum amount of ethanol/water 4:1 (v/v) to obtain a clear solution in a glass container, followed by microwave irradiation at 425 W (Pabish CM-Aquatronic) for a time sufficient to remove the solvent. The dried residue was gently ground in
Synthesis of divalent ligands of β-thio- and β-N-galactopyranosides and related lactosides and their evaluation as substrates and inhibitors of Trypanosoma cruzi trans-sialidase
Beilstein J. Org. Chem. 2014, 10, 3073–3086, doi:10.3762/bjoc.10.324
- , or S-linked lactoside 8 (0.20 mmol per mol of reacting azide) were dissolved in 2.5 mL of a dioxane/H2O mixture (8:2). Copper sulfate (0.05 mmol per mol of reacting azide) and sodium ascorbate (0.10 mmol per mol of azide reacting group) were added, and the mixture was stirred at 70 °C under microwave
- irradiation during 50 min. The mixture was then poured into a 1:1 H2O/NH4Cl solution (20 mL) and extracted with EtOAc (4 × 15 mL). The organic layer was dried (Na2SO4), filtered, and the solvent was removed under reduced pressure. The residue was purified by flash chromatography, using the solvent system
The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde
Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320
- under microwave irradiation the substituted oxygen-bridged triazolo[1,5-c][1,3,5]benzoxadiazocine was formed (Scheme 2). Interesting results were also described by Světlik and Kettmann [19]. In the case of a three-component interaction of aminoazole, salicylaldehyde, and methyl acetoacetate in refluxing
- and microwave heating did not produce any positive results. Thus, refluxing of the reactants in water, ethanol, dioxane, or application of microwave irradiation at temperatures up to 140 °C only gave rise to the formation of imine 8 (Scheme 3). The reaction time in these cases reached 3 h. On the
- other hand, refluxing in high boiling solvents (n-butanol, DMF, DMSO), as well as microwave irradiation at temperatures above 140 °C, resulted in resinification of the reaction mixture. The reaction times were varied from a minute (for microwave irradiation) to 40 min (for conventional heating). Inter
Come-back of phenanthridine and phenanthridinium derivatives in the 21st century
Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312
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