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Search for "nitronate" in Full Text gives 21 result(s) in Beilstein Journal of Organic Chemistry.
Activity assays of NnlA homologs suggest the natural product N-nitroglycine is degraded by diverse bacteria
Beilstein J. Org. Chem. 2024, 20, 830–840, doi:10.3762/bjoc.20.75
- formation of propionate 3-nitronate (P3N) as a conjugate base (Scheme 2) [39]. It is P3N that directly reacts with a cysteine in the ICL1 active site, forming a thiohydroxamate adduct that inhibits ICL1 turnover [40]. Additionally, the nitronate form of nitro acids has been proposed to behave as a
- transition analog of carboxylate groups, resulting in nitro compounds also acting as tight-binding reversible inhibitors [42]. Deprotonation of NNG also results in formation of the corresponding nitronate, albeit with a pKa of 6.6 [24], far lower than that for 3-NP (Scheme 2). Therefore, a much larger
- portion of NNG would be expected to exist as the inhibitory nitronate form at physiological pH, suggesting another potential role for nitramine groups as potent warheads in antibiotics. This antibiotic activity may also require further modification of NNG or its incorporation into a larger natural product
Anion–π catalysis on carbon allotropes
Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140
- ] are deprotonated, and tautomers I and II add to an enolate acceptor. For anion–π catalysis, nitroolefins like 5 [60] were convenient acceptors because they are compatible with asymmetric catalysis, and because stabilization of intermediate III by privileged nitronate-π interactions drives the reaction
- International License, https://creativecommons.org/licenses/by/4.0). Bioinspired enolate addition chemistry to benchmark anion–π catalysts: Stabilization of “enol” intermediate II over “keto” intermediate I and nitronate transition state III by anion–π interactions (blue) selectively catalyzes the formation of
Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal
Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92
- nitronate to the α,β-unsaturated iminium ion, should be tackled to improve the diastereocontrol. All efforts to discriminate the two faces of the nitroenolate during the addition proved unproductive during the optimization, therefore, a potential epimerization was envisaged during the course of the reaction
Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles
Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44
- azetidines 19 were also synthesized using this methodology (Scheme 5b). Nitronate anions were also found suitable for Mannich-type trapping reactions [28][29]. Anderson and co-workers accomplished several Cu-catalyzed conjugate additions of R2Zn to nitroolefins 20, followed by subsequent reaction with p
Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes
Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239
- ], benzimidazoles 6 [40][41], diazines 7 [42][43], or imidazolines 8 (Scheme 1) [44]. We have also shown that a nucleophilic attack on the phosphorylated nitronate species 2 can be carried out with the participation of N-acylhydrazides or thiosemicarbazides to afford the 1,3,4-oxadiazoles 9 [45] and the 1,3,4
- highly important imidazo[1,5-a]pyridines. It was imagined that the initial nucleophilic attack of the 2-(aminomethyl)pyridine (12) on the nitronate 2 would provide an amidinium species 13, which is very well suited for a 5-exo-trig cyclization involving the masked imine moiety of the pyridine ring
- group in 12 attenuates the nucleophilicity of the molecule, rendering the attack on the relatively bulky phosphorylated nitronate 2 inefficient. To prove this, we decided to moderate the basicity of the amine function by protection with a sulfonyl group. Gratifyingly, the N-tosylamine 17 [48] reacted
Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs
Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179
- Juanjuan Feng Tianyu Li Jiaxin Zhang Peng Jiao Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing 100875, P.R. China 10.3762/bjoc.15.179 Abstract The asymmetric cycloaddition of TIPS nitronate catalyzed by “Cu(II)-bisoxazoline” gave the 2-isoxazoline
- product in 95% yield, which was converted into tert-butyl (3S,5R)-6-hydroxy-3,5-O-isopropylidene-3,5-dihydroxyhexanoate in 14 steps through a β-hydroxy ketone. Keywords: β-hydroxy ketone; cycloaddition; 1,3-diol; isoxazoline; silyl nitronate; Introduction The chiral 1,3-diol structure is widespread in a
- our continuous efforts in asymmetric syntheses and applications of chiral 2-isoxazolines [49][50][51]. Results and Discussion Our synthesis commenced with a chiral 3,5-disubstituted-2-isoxazoline 3 or 4, which were prepared from silyl nitronate through an asymmetric 1,3-dipolar cycloaddition developed
Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)
Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14
- indolylmethyl carbanion of the sulfone and 4-substituted nitrobenzenes is shown in Scheme 5. The formed σH-adduct A undergoes O-silylation and the formed silyl nitronate B is deprotonated to form intermediate C, that, after elimination of silanol, forms nitroso intermediate D. Consecutive silylation of D leads
Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective
Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220
- (silyloxy)enamines 3 under these conditions. Nitronate anions also react as C-nucleophiles with N,N-bis(silyloxy)enamines 3 producing β-nitrooximes 7 in good yields (Scheme 4) [20][25]. Efficient coupling of DBU-nitronate salts derived from primary nitro compounds with enamines 3 was achieved at –78 °C upon
- organolithium reagent silyl nitronate 58 is deprotonated to give anion 60, which eliminates the silyloxy anion to form nitrosoalkene NSA12. Conjugate addition of the second equivalent of the organolithium compound furnishes oximes 59. However, oximes 59 are produced in rather poor yields. In 1996, Trost
- nitrosoalkenes. Precursors of nitrosoalkenes NSA. Reactions of cyclic α-chlorooximes 1 with 1,3-dicarbonyl compounds. C-C-coupling of N,N-bis(silyloxy)enamines 3 with 1,3-dicarbonyl compounds. Reaction of N,N-bis(silyloxy)enamines 3 with nitronate anions. Reaction of α-chlorooximes TBS ethers 2 with ester
Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions
Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131
- -catalyzed Michael addition/intramolecular silyl nitronate-olefin cycloaddition (ISOC)/fragmentation sequence to produce highly enantioenriched spirocyclopentaneoxindoles containing an oxime functional group from easily accessible 3-allyl-substituted oxindoles and nitroolefins, which has received wide
Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes
Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184
- treatment of a nitronate anion with oxalyl chloride were recently published [61][62] (Scheme 6). Acylnitroso compounds are generally prepared and used in situ due to their extremely reactive nature and the conditions have been summarized previously [16]. These include the oxidation of nitrile oxides [63] or
- ) and an acylnitroso dienophile 5. Synthesis of arylnitroso species by substitution of a trifluoroborate group [36]. Synthesis of arylnitroso compounds by amine oxidation. Synthesis of arylnitroso compounds by hydroxylamine oxidation. Synthesis of chloronitroso compounds by the treatment of a nitronate
Conjugate addition–enantioselective protonation reactions
Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116
- nitroalkenes Organocatalysts In the first reported example of the enantioselective protonation of a nitronate, Ellman and co-workers demonstrated that an N-sulfinylurea organocatalyst could be used to catalyze the addition of α-substituted Meldrum’s acids to terminally unsubstituted nitroalkenes (Scheme 37
- was raised to −25 °C. After the submission of this review, Ellman and co-workers published an additional example of enantioselective nitronate protonation, which was accomplished using an N-sulfinylurea organocatalyst to catalyze the addition of a pyrazol-5-one nucleophile to a trisubstituted
(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
- nitronate, which reacts with the electrophilic nitroolefin via a Michael addition. The resulting nitro compound is again deprotonated by the organocatalyst and reacts with the α,β-unsaturated ester to yield the desired product. Cascade/domino/tandem reactions producing six-membered rings Cascade and tandem
- Michael addition of the enol of the α-keto-amide 78 to nitroalkene 79, subsequent Michael addition of nitronates to the second equivalent of nitroalkene 79 and finally a Henry-type reaction between nitronate and the highly electrophilic carbonyl of the α-keto-amide, resulting in the final product 76. In
- ]. Initially nitromethane adds to the chalcone moiety, followed by a nitronate addition to the α,β-unsaturated ester. The substrate scope was widely expanded, including the aromatic moieties containing halogens, alkyl and alkoxy groups. Also, ketones bearing aryl, heteroaryl and alkyl groups, provided the
Organocatalytic and enantioselective Michael reaction between α-nitroesters and nitroalkenes. Syn/anti-selectivity control using catalysts with the same absolute backbone chirality
Beilstein J. Org. Chem. 2015, 11, 2577–2583, doi:10.3762/bjoc.11.277
- , in which the nitronate moiety exposes a different reactive prochiral face. These results are in good agreement with our previously reported work in which DFT calculations also showed that the difference in the steric bulk of the nitrogen substituents of the Brønsted basic site of the catalysts (the
Recent developments in copper-catalyzed radical alkylations of electron-rich π-systems
Beilstein J. Org. Chem. 2015, 11, 2278–2288, doi:10.3762/bjoc.11.248
- processes are generally thought to be related to long established atom-transfer radical reactions. However, unlike classical reactions, these new transformations lead to simple alkylation products. This short review will highlight recent advances in alkylations of nitronate anions, alkenes and alkynes, as
- recent examples from this emergent area, including copper-catalyzed alkylation reactions of nitroalkanes, alkenes and alkynes. Results and Discussion Additions to nitronate anions The selective C-alkylation of nitroalkanes with alkyl halide electrophiles is a long-standing challenge in organic synthesis
- (Scheme 1). This is mainly because of the propensity of nitronate anions to undergo alkylation at oxygen rather than carbon, a process that has been known for more than 60 years [15]. Recently, our group has developed a copper/diketimine catalyst system to selectively C-alkylate nitroalkanes [16]. While
New aryloxybenzylidene ruthenium chelates – synthesis, reactivity and catalytic performance in ROMP
Beilstein J. Org. Chem. 2015, 11, 1910–1916, doi:10.3762/bjoc.11.206
- benzylidenecarboxylate (Figure 2a) [6] and nitronate complexes (Figure 2b) [7] as well as amidobenzylidene ruthenium chelates (Figure 2c–e) that we have disclosed in cooperation with the Grela group [8]. Recently we have reported a study on aryloxybenzylidene ruthenium chelates (1a–d Figure 3) [9]. Similar complexes
Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene
Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251
- initial assessment of substituent effects on the rearrangement process is presented. Keywords: cycloaddition; diene; nitro; nitronate; rearrangement; Introduction We have previously reported examples of a general new [3,3]-sigmatropic rearrangement, the conversion of O-allyl nitronic esters (nitronates
- nitroalkene Diels–Alder reactions have been proposed. Denmark et al. favor a stepwise process proceeding via a zwitterion intermediate [11][14]. Alkene stereointegrity is normally retained, presumably owing to a cyclic conformation dictated by charge interaction between the cation center and tin nitronate
- center. A more rapid change of the face presented to the nitronate-O atom would be expected to occur for cyclo zwitterion 17 because top-to-bottom passage past an H-atom should be more rapid than passage past a methyl group as required for the cyclo zwitterions 14 and 15. [3,3]-Sigmatropic rearrangement
Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step
Beilstein J. Org. Chem. 2013, 9, 1737–1744, doi:10.3762/bjoc.9.200
- available from a Henry reaction [50], imine 14 from the condensation of p-anisidine and isobutyraldehyde, and the process can easily be made asymmetric [45]. Conjugate addition of hydride to 13 and subsequent trapping of the nitronate anion with freshly prepared imine 14 in THF gave β-nitroamine 15 in 64
Simple synthesis of pyrrolo[3,2-e]indole-1-carbonitriles
Beilstein J. Org. Chem. 2013, 9, 934–941, doi:10.3762/bjoc.9.107
- carbanion is silylated with trimethylchlorosilane to form trimethylsilyl nitronate A. Then a consecutive deprotonation forms another carbanion B at the β-position to the ring. The attack of this carbanion on the trimethylsilylnitronate results in the substitution of trimethoxysiloxyl and formation of C in
Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO4
Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96
- furnish cyclic nitronate derivatives of type 3 [1][3]. In particular, the reactivity of nitroalkenes with unactivated olefins has been extensively investigated by Denmark and co-workers in [4 + 2] hetero-Diels–Alder (HDA) cycloadditions [1][3] and, in some instances, the resulting cyclic nitronates such
- the second step, the TS involved in [3 + 2] nitronate cycloadditions shows lower charge transference and degree of asynchronicity, and therefore, it is expected that a lower stabilizing effect is caused by polar solvents [9][30][31]. Furthermore, when a fraction of water is present in the medium, the
- resulting from the endo approach of the smaller dipolarophile MVK by the Re face of the nitronate. It is worthwhile to mention that, depending of the nitroso acetal structure, an opening of the six-membered ring is caused due to a greater sensitivity to the reaction medium, leading to generation of the
A versatile and efficient approach for the synthesis of chiral 1,3-nitroamines and 1,3-diamines via conjugate addition to new (S,E)-γ-aminated nitroalkenes derived from L-α-amino acids
Beilstein J. Org. Chem. 2013, 9, 832–837, doi:10.3762/bjoc.9.95
- yields of 68–88%. The conjugate addition of hydride, methoxide, nitronate and azide nucleophiles to 2a–c led to the corresponding chiral 1,3-nitroamines in 74–90% yield. The conjugate addition of cyanide anion to 2a,b was followed by HNO2 elimination affording chiral aminated acrylonitriles (73–98%). On
- , chiral nitroamines [55][56] are important intermediates directly transformed, via reduction of the nitro group, into diamines [57] or via a Nef reaction in amino acids [58]. Specifically, chiral 1,2-nitroamines have been mainly accessed by direct nucleophilic addition of nitronate anions to imine
- analysis showed that the stereochemical integrity of 2 was preserved throughout the synthetic process. Next, the reactivity of the new chiral nitroalkenes was investigated with respect to the conjugate addition of hydride, nitronate, methoxide, cyanide, and azide anions in addition to benzylamine aiming to
A convenient synthesis of γ-functionalized cyclopentenones
Beilstein J. Org. Chem. 2005, 1, No. 11, doi:10.1186/1860-5397-1-11
- carbonyls by the formation of the nitronate anion in the presence of sodium methoxide followed by its addition to concentrated sulfuric acid at -50°C, allowed the formation of the 1,4-diketones 3 in fair to good yields (Table 1). During recent years, some cyclopentenones derivatives were known to exhibit
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