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Search for "in situ" in Full Text gives 1111 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Asymmetric synthesis of a stereopentade fragment toward latrunculins
Beilstein J. Org. Chem. 2023, 19, 428–433, doi:10.3762/bjoc.19.32
- oxidation in presence of DMP. The assembly of aldehyde 8 and methyl ketone 15 was envisaged through a stereoselective aldol reaction. After unsuccessful attempts of Mukaiyama aldol reactions with silyl enol ethers [28], we found that dicyclohexylboron enolate 20, made in situ from ketone 15 and Cy2BCl in
Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities
Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31
- hydroxybenzaldehyde 80 into the corresponding acetal followed by Ullmann-type coupling with 52, led to the formation of diaryl ether 83. Subsequent Corey–Fuchs reaction [49] and in situ alkylation led to formation of the propargylic alcohol 85. Deprotection of the aldehyde followed by chain elongation through the
Group 13 exchange and transborylation in catalysis
Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28
- catalyse the hydroboration of alkynes with HBcat [50]. Hoshi later reported that Cy2BH [51] and in situ generated bis(pentafluorophenyl)borane, Piers’ borane [52], catalysed the hydroboration of alkynes with HBpin, to give alkenyl pinacol boronic esters. Tris(2,4,6-trifluorophenyl)borane [53], tris(3,4,5
- ‒H borylation, with an initial B‒Y/B‒H transborylation activating the precatalyst [62][63][64][65]. Zhang showed that benzoic acid decomposed HBpin to BH3 in situ to catalyse the C2‒H borylation of indoles (Scheme 4b) [66][67]. Gellrich reported the bis(pentafluorophenyl)borane-catalysed dimerisation
- transborylation in catalysis (Scheme 6) [69]. Reactive intermediates were characterised and BH3 was observed to be generated in situ by the decomposition of HBpin. The proposed catalytic cycle involved nucleophile-promoted decomposition of HBpin to various borohydride species 19, which reacted with the BH3
Recommendations for performing measurements of apparent equilibrium constants of enzyme-catalyzed reactions and for reporting the results of these measurements
Beilstein J. Org. Chem. 2023, 19, 303–316, doi:10.3762/bjoc.19.26
- opposite directions of reaction. If the necessary substances are not readily available, it is necessary to prepare them in order to perform a rigorous measurement of the equilibrium constant. Labile or difficult to obtain substances may be prepared in situ [29]. For reactions that proceed without the need
- demonstrate the approach to equilibrium from different directions of reaction. Thus, as mentioned in section 3.9, some investigators have used very small quantities of a substrate that required substantial synthetic efforts [25] or have prepared the needed substrate in situ [27]. 3.14. Importance of careful
Continuous flow synthesis of 6-monoamino-6-monodeoxy-β-cyclodextrin
Beilstein J. Org. Chem. 2023, 19, 294–302, doi:10.3762/bjoc.19.25
- , these two drawbacks are not a problem for large-scale flow synthesis when using an H-Cube system with an incorporated electrolytic cell producing H2 in situ from ultrapure water [47]. The Pd/C catalyst is placed in a stainless steel cartridge, so it is not necessary to separate it from the solution
- prepared in situ in the flow tube reactor, as the aqueous solution containing β-CD (1) and NaOH (1.5 equiv) was introduced into the reactor at twice the flow rate as the solution of TsCl in THF (Scheme 1). In this way, twice as many equivalents of TsCl were required compared to the general 1.3 equivalents
Sequential hydrozirconation/Pd-catalyzed cross coupling of acyl chlorides towards conjugated (2E,4E)-dienones
Beilstein J. Org. Chem. 2023, 19, 176–185, doi:10.3762/bjoc.19.17
- of 20 h at 50 °C led only to 8% yield (Table 2, entry 8). Trapping experiments of the in situ-formed (E)-alkenylzirconocene 24 revealed quantitative conversion of the starting material 25a and only traces of chain walking (less than 4%) (for details see Supporting Information File 1, chapter 2.1). To
- (dba) were catalytically inactive (Table 3, entries 6 and 7). Furthermore, in situ-formed Schwartz reagent was found to be less effective as compared to the use of isolated Cp2Zr(H)Cl and thus further experiments in this direction were abandoned. In order to explore the substrate scope of the
Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry
Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15
- , phosphate leaving groups, etc.) is still an unclear question, even if the latter species proved to have an unambiguous beneficial effect on the cross-coupling yields and selectivities. Several recent literature results which enlighten the role of those additives, either brought by external reagents or by in
- situ-formed intermediates, are gathered in Table 2. The beneficial role of the NMP co-solvent on the alkyl–alkenyl cross-coupling yield reported by Cahiez (Scheme 2b) and considerably used ever since was explained at a molecular level by Neidig in 2018. It was demonstrated that NMP did not act as a
1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures
Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12
- the relative stereochemistry (Scheme 17) [108][109]. 6 Synthetic equivalents of vinyl carbenes in (2 + 1) cycloadditions: Au(I)-catalyzed generation of 1,4-dithiane-fused vinylcarbene species In 2007, Wang and co-workers reported a gold-catalyzed Parham-type 1,2-sulfur migration to generate in situ a
Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles
Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6
- Research Center, Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey 10.3762/bjoc.19.6 Abstract We have developed a catalytic aza-Nazarov reaction of N-acyliminium salts generated in situ from the reaction of a variety of cyclic and acyclic imines with α,β
- acetal group could be used as substrates in an aza-Nazarov cyclization with the intermediacy of in situ-generated N-acyliminium ions (Scheme 1b) [21]. The first catalytic aza-Nazarov reaction was reported by Tius and co-workers in 2010, which involved the kinetic resolution of azirine derivatives via an
- cyclization of an in situ-formed iminium intermediate is not efficient under certain reaction conditions, then its hydrolysis with adventitious water, which might be present in the reaction medium, would lead to the formation of an aldehyde side product. Unfortunately, our attempts to isolate such a side
Total synthesis of grayanane natural products
Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181
- reagent and DMDO could induce an epoxidation on the strained olefin. From intermediate 40, the key reductive epoxide opening/Dowd–Beckwith rearrangement cascade could be performed in the presence of an in situ-generated Ti(III) catalyst. The main side-product of this reaction was due to a simple reductive
Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field
Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179
- instead of corresponding C-nucleophiles or C-electrophiles in redox-neutral organocatalyzed reactions. Organocatalysis by redox-active organic molecules N-Oxyl radical catalysis Reactive N-oxyl radicals generated in situ from the corresponding N-hydroxy compounds have found numerous applications in CH
- improved stability and tunable reactivity by structure modification. Amine-N-oxyl radical/oxoammonium cation catalysis Compared to the N-oxyl radical catalysis discussed above, where reactive N-oxyl radicals represent an active organocatalyst form generated in situ, in oxoammonium cation catalysis [74][76
- be selectively oxidized in the presence of secondary alcohols. In the case of co-catalysts Fe(NO3)3 or NOx species (NaNO2, HNO3, t-BuONO), an aminoxyl is oxidized in situ to an oxoammonium cation, which oxidizes alcohols. Fe and NOx-based methods demonstrate lower functional group compatibility and
Navigating and expanding the roadmap of natural product genome mining tools
Beilstein J. Org. Chem. 2022, 18, 1656–1671, doi:10.3762/bjoc.18.178
- (non-targeted, e.g., modifying culturing conditions) and pathway-specific (e.g., heterologous expression or in situ pathway activation) approaches have been developed to awaken silent biosynthetic pathways [16]. Most importantly, however, genome mining can prevent the time-consuming re-discovery of
A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine
Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172
- . Subsequent reduction with sodium dithionite then afforded triamine 9. Another way comprised the installation of a nitroso group in compound 6 through reaction with in situ-generated nitrous acid giving nitroso compound 8. The subsequent reduction to the corresponding amine with hydrogen sulfide afforded the
One-pot double annulations to confer diastereoselective spirooxindolepyrrolothiazoles
Beilstein J. Org. Chem. 2022, 18, 1607–1616, doi:10.3762/bjoc.18.171
- introduced in this study. Subsequently one equivalent of aldehyde and olefinic oxindole in situ were followed by decarboxylative 1,3-dipolar cycloaddition for diastereoselective synthesis of spirooxindolepyrrolothiazoles with generating 5 new bonds, 5 stereocenters and two heterocycles (Scheme 1C and Scheme
- purification from N,S-acetalation with 1.0:1.15 of 1a/2 at 25 °C for 6 h with EtOH as solvent, in situ followed by addition of 1.1:1.0 of 1a/4a for [3 + 2] cycloaddition at 90 °C for 9 h gave compound 5a with the 81% of LC yield. Next, the stepwise process was also carried out by using the thioproline 3a (1
Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene
Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170
- propargyl-containing compounds, including other CDs, to form a dimer [12]. Usually, such reactions proceed with a Cu(I) catalyst [27]; however, Cu(I) can be generated in situ by the reduction of Cu(II) [12][28] or by the dissolution of metal copper [29]. Moreover, the load of the catalyst varies from
Functionalization of imidazole N-oxide: a recent discovery in organic transformations
Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168
- . The study of the optimization conditions showed that the highest yields of products were obtained when: (I) in case of path A, 1.0 mmol of the 2,2-dimethyl-4-phenyl-2H-imidazole 1-oxide (9a) was reacted with pentafluorophenyllithium (13) (which was formed in situ from pentafluorobenzene (12)] in the
Dissecting Mechanochemistry III
Beilstein J. Org. Chem. 2022, 18, 1454–1456, doi:10.3762/bjoc.18.150
- Margetić used dibrominated polycyclic imides as substrates to generate reactive alkenes, which could be trapped in situ by several dienes through Diels−Alder cycloadditions by ball milling (Scheme 3) [7]. Further, Moores and co-workers synthesized phosphorus-bridged heptazine-based carbon nitrides (g-h-PCN
- . Mechanochemical palladium-catalyzed borylation protocol of aryl halides. 1,2-Debromination of polycyclic imides, followed by in situ trapping of the dienophile by several dienes. Synthesis of g-h-PCN from sodium phosphide and trichloroheptazine mediated by mechanochemistry. Mechanochemical intra- and
Synthesis and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes
Beilstein J. Org. Chem. 2022, 18, 1338–1345, doi:10.3762/bjoc.18.139
- treated with a mixture of sodium polyphosphides of the type NaxPy (obtained in situ from sodium metal and white phosphorus P4), containing mainly NaP5 and Na3P7 [42]), resulting in sodium 3,4,5-tris(chlorophenyl)-1,2-diphosphacyclopentadienides 7 in good yields (60 and 63%, Scheme 3). This reaction
B–N/B–H Transborylation: borane-catalysed nitrile hydroboration
Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138
- adjusted to maximise efficiency for yield or chemoselectivity. Reaction of the turnover reagent, HBpin, in the absence of catalyst gave no observable reduction (see Supporting Information File 1). The optimised conditions were applied to a substrate scope, where the hydroboration products were converted in
- situ to the corresponding amine hydrochloride salt which can be isolated without the use of column chromatography (Scheme 2). The N,N-diborylamines have also been used directly in subsequent transformations [34][35][36][37]. Heptanenitrile was reduced to 1-heptylamine hydrochloride (1a) in good yield
Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells
Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136
- 23% overall yield. First, hydrolysis of 1, in situ conversion to the acyl chloride and subsequent Lewis acid-promoted Friedel–Crafts acylation reaction produced compound 2 (Scheme 1), where the AlCl3 was also responsible for the demethylation. Compound 2 was then subjected to monoalkylation with 1,4
Ferrocenoyl-adenines: substituent effects on regioselective acylation
Beilstein J. Org. Chem. 2022, 18, 1270–1277, doi:10.3762/bjoc.18.133
- )B3LYP/6-31+G(d) method.a Supporting Information Supporting Information File 234: Details on experimental procedures, DFT calculated energies and optimized coordinates for transition state structures and reactants, and the results of in situ 1H NMR monitoring. Acknowledgements All calculations were
Enantioselective total synthesis of putative dihydrorosefuran, a monoterpene with an unique 2,5-dihydrofuran structure
Beilstein J. Org. Chem. 2022, 18, 1264–1269, doi:10.3762/bjoc.18.132
- -bromobut-2-yne in the presence of CpTiIIICl2 (generated in situ by reduction of CpTiCl3 with Mn) afforded α-hydroxyallene 3. We have recently described that this Barbier-type reaction affords α-hydroxyallenes as major products, mixed with smaller amounts of homopropargylic alcohols, either if the reaction
Modular synthesis of 2-furyl carbinols from 3-benzyldimethylsilylfurfural platforms relying on oxygen-assisted C–Si bond functionalization
Beilstein J. Org. Chem. 2022, 18, 1256–1263, doi:10.3762/bjoc.18.131
- sensitive towards silica gel column chromatography, and all of our attempts to isolate it failed. For this reason, we went on to consider C3–Si functionalization strategies of alcohols 4c–7c relying on the formation of cyclic siloxanes and subsequent in situ cross-coupling. We first briefly investigated Pd
A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH4I
Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130
- , the in situ generated α-iodoketone was proposed to be the key active species. Keywords: 2-aminothiazoles; electrosynthesis; indirect electrolysis; halide ion; Introduction Thiazoles are prevalent structural motifs in a wide range of natural products [1] and synthetic molecules possessing various
- well-known method (Scheme 1a) [18]. Since active methylene ketones are able to be in situ α-halogenated, the modified Hantzsch condensation of active methylene ketones with thioureas has attracted increasing attention in thiazoles’ synthesis, thereby saving costs and time needed to prepare the required
- α-halogenated dielectrophiles. Along this line, in situ α-halogenation strategies have been developed, using various halogenating reagents including Br2 [19][20], I2 [21][22], NBS [23][24][25], tribromoisocyanuric acid [26], 1,3-dichloro-5,5-dimethylhydantoin [27], HBr or HI, DMSO [28] etc. (Scheme
Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation
Beilstein J. Org. Chem. 2022, 18, 1217–1224, doi:10.3762/bjoc.18.127
- acid catalyst, namely ethylaluminum dichloride [13]. Furthermore, when carrying out the reaction of compounds 1 (R1 = Me, R2 = COOMe, COOEt, COOCMe3) with DMB in the presence of the catalyst O-menthoxyaluminium dichloride, generated in situ, complete diastereoselectivity was observed. The DA reactions
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