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Search for "cyclization" in Full Text gives 1054 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis
Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214
- cross-coupling between these two intermediates, followed by intramolecular cyclization and subsequent deprotonation results in the desired product (Scheme 20). Furthermore, Budny and coworkers demonstrated that (±)-triticonazole and related compounds could be cyclized and alkoxylated to the
- proposed mechanism involves the one-electron oxidation of triticonazole to form a radical cation, followed by cyclization to an intermediate. Subsequent anodic oxidation forms a doubly charged cation, which is then captured by methanol and deprotonated to yield the final product (pathway A). Additionally
- cyclization of 2-ethynylanilines has been proven to be one of the most effective strategies for synthesizing indole derivatives. In this regard, Wang and coworkers developed the electrosynthesis of 3-iodoindoles from 2-ethynylanilines under mild and straightforward conditions [31]. The functionalization of
HFIP as a versatile solvent in resorcin[n]arene synthesis
Beilstein J. Org. Chem. 2024, 20, 2469–2475, doi:10.3762/bjoc.20.211
- efficient solvent for synthesizing resorcin[n]arenes in the presence of catalytic amounts of HCl at ambient temperature and within minutes. Remarkably, resorcinols with electron-withdrawing groups and halogens, which are reported in the literature as the most challenging precursors in this cyclization, are
- tolerated. This method leads to a variety of 2-substituted resorcin[n]arenes in a single synthetic step with isolated yields up to 98%. Keywords: cavitand; cyclization; HFIP; hydroxyalkylation; resorcinarenes; Introduction The acid-catalyzed aldehyde-resorcinol condensation has been studied for more than
- limitation, we analyzed the mechanism underlying the formation of resorcin[n]arenes. The first step of the cyclization reaction is a hydroxyalkylation involving various cationic intermediates [69]. Hence, we hypothesized that any factor enhancing the rate of the first step by stabilizing carbocations will
Photoredox-catalyzed intramolecular nucleophilic amidation of alkenes with β-lactams
Beilstein J. Org. Chem. 2024, 20, 2461–2468, doi:10.3762/bjoc.20.210
- reactions limit the utility of this approach. Herein, we report an intramolecular photoredox cyclization of alkenes with β-lactams in the presence of an acridinium photocatalyst. The approach uses an intramolecular nucleophilic addition of the β-lactam nitrogen atom to the radical cation photogenerated in
- intramolecular nucleophilic attack induced by photocatalytic oxidation was reported by Yoon et al. with tosylamide derivatives [29]. Specifically, amides were employed in a photoredox cyclization process using a strong photooxidative acridinium catalyst such as the Fukuzumi catalyst (I, Figure 1B) [30][31
- carboaminations. However, photoredox catalysis could be applied to a suitable β-lactam intermediate decorated with an alkene moiety to achieve N–H addition and cyclization to the fused bicyclic system of clavams (Figure 2A). Clavulanic acid (1, Figure 2B) belongs to the family of clavam β-lactam compounds and is
Hypervalent iodine-mediated cyclization of bishomoallylamides to prolinols
Beilstein J. Org. Chem. 2024, 20, 2455–2460, doi:10.3762/bjoc.20.209
- Pierre Angot, 64053 Pau Cedex 09, France School of Pharmacy and Bioengineering, Keele University, Keele, Staffordshire ST5 5JX, United Kingdom 10.3762/bjoc.20.209 Abstract A change in mechanism was observed in the hypervalent iodine-mediated cyclization of N-alkenylamides when the carbon chain between
- the alkene and the amide increased from two to three atoms. In the latter case, cyclization at the amide nitrogen to form the pyrrolidine ring was favored over cyclization at the amide oxygen. A DFT study was undertaken to rationalize the change in mechanism of this cyclization process. In addition
- , reaction conditions were developed, and the scope of this cyclization studied. Keywords: cyclization; DFT; hypervalent iodine; mechanism; proline; Introduction Proline is one of the 20 DNA-encoded proteinogenic amino acids that are essential to life [1][2]. In addition, the pyrrolidine core is present in
Evaluating the halogen bonding strength of a iodoloisoxazolium(III) salt
Beilstein J. Org. Chem. 2024, 20, 2401–2407, doi:10.3762/bjoc.20.204
- . Finally, the potential as halogen-bonding activator was benchmarked in solution in the gold-catalyzed cyclization of a propargyl amide. Keywords: diaryliodonium; gold catalysis; halogen bonding; hypervalent iodine; non-covalent interactions; Introduction The compound class of diaryliodonium (DAI) salts
- applied as catalyst for the cyclization of propargylic amide 11, a typical benchmark reaction in gold catalysis (Scheme 2) [24][25][26][27], which had previously already been activated by iodine(I) and iodine(III)-based XB donors [15][18]. To evaluate the activity of the new iodoloisoxazolium 7BArF, it
- )AuCl was applied with a catalyst loading of 2 mol %, activated by an equal amount of the DAI salt. Due to solubility issues, the reaction had to be performed in methylene chloride instead of chloroform. The gold-catalyzed cyclization reaction (Scheme 2) was followed via 1H NMR spectroscopy (Figure 3
Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system
Beilstein J. Org. Chem. 2024, 20, 2342–2348, doi:10.3762/bjoc.20.200
Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis
Beilstein J. Org. Chem. 2024, 20, 2280–2304, doi:10.3762/bjoc.20.196
- complement and augment experimental chemistry. In addition to these methods, Corminboeuf and co-workers [134] proposed a genetic algorithm for the de novo design of general catalysts (Figure 14). Considering the Pictet–Spengler cyclization of tryptamine derivatives catalysed by hydrogen-bond donors, the
Heterocycle-guided synthesis of m-hetarylanilines via three-component benzannulation
Beilstein J. Org. Chem. 2024, 20, 2208–2216, doi:10.3762/bjoc.20.188
- interrupted Kröhnke reaction (Scheme 1B) [51][52]. The main step of this process is an intermolecular cyclization of the formed 1,5-diketone followed by aromatization. Previously we have shown that 1,3-diketones bearing an electron-withdrawing group (EWG) adjacent to one of the carbonyls readily react with in
Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis
Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182
- with a variety of heteroatoms. In this Perspective, we review the addition and cyclization reactions of heteroatom radicals with isocyanides and discuss the synthetic prospects of the reaction of isocyanides with heteroatom radicals. Keywords: aza-Bergman cyclization; heteroatom-mixed system; imidoyl
- radical; isocyanide; radical addition; radical cyclization; Introduction Carbon monoxide is a very important C1 resource in both synthetic and industrial chemistry and is not only capable of reacting with a variety of active species such as carbon cations, carbon anions, and carbon radicals (Figure 1
- reaction of carbon radicals with isocyanides generates imidoyl radicals as key active species [12], and addition and cyclization reactions using these radical species are useful in synthetic organic chemistry, especially multicomponent synthesis. If various functional groups can be appropriately attached
Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps
Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178
- is that the reaction with methylhydrazine leads to two different regioisomers. Shen et al. used a concept developed by them for the C-acylation of β-ketoesters for the one-pot synthesis of pyrazoles. SmCl3-catalyzed acylation of these yields the 1,3-diketones 4, and after cyclization with hydrazine
- tolerated in this consecutive four-component reaction, as the 1,3,4-thiadiazine synthesis competes with the thiazole synthesis. Salicylaldehydes 14 and 4-hydroxy-6-methyl-2H-pyran-2-one (16) can also be used to produce 1,3-dicarbonyl compounds 18 by Knoevenagel condensation and subsequent cyclization. This
- acetylacetonate 20. Extension of the sequence by cyclization with hydrazine leads to the pyrazole products 21 (Scheme 5) [53]. The method works best with acetylacetonates, since deprotonation of other diketones with NaOEt leads to deactivation of the isothiocyanates. A limitation of the method is the formation of
Diastereoselective synthesis of highly substituted cyclohexanones and tetrahydrochromene-4-ones via conjugate addition of curcumins to arylidenemalonates
Beilstein J. Org. Chem. 2024, 20, 2016–2023, doi:10.3762/bjoc.20.177
- , curcumin showcases its Michael donor–acceptor ability in different ways, such as simple Michael addition, [4 + 2] annulation, Michael addition followed by cyclization or one-pot multicomponent reactions (MCR), etc. (Scheme 1) [25]. In 2011, our group reported the reactivity of curcumin as a Michael donor
- addition–cyclization of curcumins with chalcones to synthesize functionalized cyclohexanones have been reported [28][29]. On the other hand, diastereoselective cascade Michael addition–cyclization of curcumins with α-bromonitroalkenes and α-halodicyclopentadienones afforded functionalized dihyrofurans [26
- equilibrium with 1,3-dicarbonyl enolate I, but the former would be trapped via cyclization involving a diastereoselective 6-endo-trig intramolecular Michael addition to the enone moiety leading to highly substituted cyclohexanone 3. The formation of triple Michael adduct 4 can be attributed to the enolate 3
Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations
Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175
- versatile reagents in organic synthesis. They have for instance been frequently employed for the construction of azacycles through various cyclization protocols or cycloaddition reactions [6][7][8][9][10]. Early work in this field includes the well-known Fischer indole synthesis [11]. Additionally, they
- for constructing azacycles. Resorting to electrochemical approaches furnishes original compounds. Although the first report dates back to 1974, this tool has only been seriously considered in the last 15 years. Oxidative cyclization of hydrazones In 1974, Tabaković et al. published the oxidative
- cyclization of 2-acetylpyridine-derived N-phenylhydrazone 1a to form triazolopyridinium salt 2a [34]. The process was further applied to various 2-acetylpyridine and 2-benzoylpyridine derivatives (Scheme 1) [35][36]. The corresponding pyridinium salts 2 were obtained in high yields when the electrolysis was
Development of a flow photochemical process for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence: in situ-generated 2-benzopyrylium as photoredox catalyst and reactive intermediate
Beilstein J. Org. Chem. 2024, 20, 1973–1980, doi:10.3762/bjoc.20.173
- Abstract A flow photochemical reaction system for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence was developed, which utilizes in situ-generated 2-benzopyrylium intermediates as the photoredox catalyst and electrophilic substrates. The key 2-benzopyrylium intermediates were
- generated in the flow reaction system through the intramolecular cyclization of ortho-carbonyl alkynylbenzene derivatives by the π-Lewis acidic metal catalyst AgNTf2 and the subsequent proto-demetalation with trifluoroacetic acid. The 2-benzopyrylium intermediates underwent further photoreactions with
- [26][27][28][29] is increased. Thus, the flow photochemical process is crucial and beneficial to product formation. Recently, we reported a sequential transformation consisting of a π-Lewis acidic metal-catalyzed cyclization [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] and
1,2-Difluoroethylene (HFO-1132): synthesis and chemistry
Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171
- converted into polyfluorinated olefins RFCF=CFH by HI elimination. Cyclization reactions Carbocyclizations: A series of articles devoted to structural investigations of 1,2-difluorocyclopropanes was published [96][97][98]. For this purpose, cis- and trans-1,2-difluorocyclopropanes were synthesized by liquid
Solvent-dependent chemoselective synthesis of different isoquinolinones mediated by the hypervalent iodine(III) reagent PISA
Beilstein J. Org. Chem. 2024, 20, 1914–1921, doi:10.3762/bjoc.20.167
- peracetic acid as a terminal oxidant [20]. Recently, Kočovský et al. disclosed a method employing 2-methylbenzamide and benzonitrile to yield 3-aryl-substituted isoquinolinone derivatives in the presence of n-butyllithium [21]. On the other hand, the intramolecular oxidative cyclization is also a viable
- –intramolecular cyclization cascade with excellent chemoselectivity in aqueous CH3CN [25]. Herein, as part of our continuing studies of heterocyclic scaffold synthesis mediated by hypervalent iodine reagents, we present the solvent-dependent chemoselective synthesis of a series of isoquinolinones mediated by PISA
- migration and reductive elimination, along with the release of iodobenzene and sulfamic acid. Cyclization of protonated G takes place to afford the intermediate H. Finally, release of water and β-proton elimination produces the rearranged product 3a (Scheme 8). Conclusion In summary, we reported the
Novel oxidative routes to N-arylpyridoindazolium salts
Beilstein J. Org. Chem. 2024, 20, 1906–1913, doi:10.3762/bjoc.20.166
- -stage functionalization; easily available ortho-pyridyl-substituted diarylamines are used as the precursors. Keywords: anodic oxidation; diarylamines; electrochemical cyclization; pyridoindazolium salts; reversible ring closure; Introduction Aromatic polyfused N-heterocycles are of interest as a
- cyclization of perfluorinated phenylpyrilium salts using arylhydrazine [12]; the process is based on the fluorine nucleophilic substitution thus limiting its applicability to a wider range of substrates. Pyridyl-substituted diarylamines may be considered as the possible precursors for N-arylpyridoindazolium
- intermediate (i.e., the diarylamines’ radical cation) and indicates the dominance of the intramolecular cyclization over the intermolecular C–N coupling process. Oxidation of diarylamines in the presence of an excess of trifluoroacetic acid gave no targeted pyridoindazolium salts, whereas the amount of
Electrochemical radical cation aza-Wacker cyclizations
Beilstein J. Org. Chem. 2024, 20, 1900–1905, doi:10.3762/bjoc.20.165
- aza-Wacker cyclizations under acidic conditions, which are expected to proceed via radical cations generated by single-electron oxidation of alkenes. Keywords: alkene; aza-Wacker cyclization; electrochemistry; radical cation; sulfonamide; Introduction Activating bench-stable substrates is the first
- the difference in such reactivities are intramolecular cyclizations (Scheme 1). A radical cyclization generates a five-membered ring with a less-stable primary radical, while a six-membered ring with a secondary cation is obtained through ionic cyclization. When such intramolecular cyclizations are
- cyclization using the alkene 1 as a model (Table 1). Based on the conditions reported by Yoon and Moeller, the initial screening was carried out using tetrabutylammonium triflate (Bu4NOTf)/1,2-dichloroethane (1,2-DCE) solution. Carbon felt (CF) was used as an anode instead of reticulated vitreous carbon (RVC
Access to 2-oxoazetidine-3-carboxylic acid derivatives via thermal microwave-assisted Wolff rearrangement of 3-diazotetramic acids in the presence of nucleophiles
Beilstein J. Org. Chem. 2024, 20, 1894–1899, doi:10.3762/bjoc.20.164
- cyclization [15][16]. Additionally, the manganese(III)-promoted cyclization of N-alkenyl malonamides [17][18] and the Cu(I)-catalyzed reaction of propiolic acid derivatives with nitrones (Kinugasa reaction) [19][20][21] should also be mentioned, as well as intramolecular C–H insertion using
The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)
Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162
- limited to methanol due to solubility problems, and HClO4 was selected because other Brønsted acids caused amine deprotection. The GBB adducts 58 could be further elaborated through a Buchwald intramolecular nucleophilic substitution/cyclization, as it will be described in section 3.3. 3 Novel scaffolds
- -substituted products 60 underwent TFA-promoted deprotection which triggered the intramolecular cyclization to furnish the indole moiety in the desired products 61. A control experiment showed that the GBB product 60 was obtained as the sole product in the absence of acid catalyst. Another group developed the
- same reaction via a two-step synthesis [58]. Initially, the three starting materials were subjected to the GBB reaction in the presence of a catalytic amount of ZnCl2 to give the fused products 60. Then, the cyclization was carried out using TFA to deliver 61 (14 examples) in yields ranging from 60% to
A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts
Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161
- significant topic. Surprisingly, there has been limited information on 5-deazaalloxazines (dAll) synthesis [20][21][22]. Most known methods employ the cyclization of 6-(arylamino)uracils with one-carbon reagents such as triethyl orthoformate, dimethylformamide dimethylacetal, carbon disulfide, N,N
Discovery of antimicrobial peptides clostrisin and cellulosin from Clostridium: insights into their structures, co-localized biosynthetic gene clusters, and antibiotic activity
Beilstein J. Org. Chem. 2024, 20, 1800–1816, doi:10.3762/bjoc.20.159
- times dehydrated was identified. Cyclization reactions introduced thioether cross-links between dehydrated Thr/Ser residues and specific cysteine thiol groups. However, due to identical masses of dehydrated linear peptides (lacking thioether rings) and cyclic forms (containing Dhb and Dha rings), a
Ugi bisamides based on pyrrolyl-β-chlorovinylaldehyde and their unusual transformations
Beilstein J. Org. Chem. 2024, 20, 1773–1784, doi:10.3762/bjoc.20.156
- component, after the formation of the expected Ugi bisamide products, subsequent post-transformations allow the synthesis of products of intramolecular cyclization [19][20][21][22] and/or products of a tandem combination of several reactions (Scheme 1) [22][23][24][25][26]. At the same time, the use of so
Harnessing unprotected deactivated amines and arylglyoxals in the Ugi reaction for the synthesis of fused complex nitrogen heterocycles
Beilstein J. Org. Chem. 2024, 20, 1758–1766, doi:10.3762/bjoc.20.154
- [11]. Different strategies have been developed to avoid these competitive reactions, the most common ones being the use of protecting groups (Ugi/deprotection/cyclization strategy) [12][13][14] or of surrogates of amines [15]. However, direct incorporation of the second amine without derivatization is
- with a reduced reactivity in the synthesis of 3H-benzo[e][1,4]diazepin-5-ones, heterocycles previously synthesized by our research group through Ugi/Staudinger/aza-Wittig and Ugi/reduction/cyclization sequences, using 2-azidobenzoic [20] and 2-nitrobenzoic [21] acids, respectively. The first
- workup the only product observed was the corresponding benzodiazepinone 5, resulting from a spontaneous cyclization of the Ugi adduct, in a six-center four-component Ugi reaction (U-6C-4CR), which prevents the need of additional steps (Scheme 1, Table 1). Due to the interest of these results and
Syntheses and medicinal chemistry of spiro heterocyclic steroids
Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152
- protecting group yielded the corresponding hydroxyalkynyl derivative 4. Subsequent Lindlar reduction resulted in the (Z)-alkene and a chemoselective tosylation of the primary alcohol led to the formation of tosylate 5. This intermediate underwent a stereospecific 4-exo cyclization upon exposure to iodine
- reported the formation of an α,α-dicyanoalkene from dehydroepiandrosterone (DHEA) and its efficient transformation to dienamides 15 in a single step via a cascade reaction [15][16]. The construction of the β-lactam ring involved a cascade 4-endo N-cyclization/aerobic oxidation sequence in presence of
- sodium hydride, yielding moderate yields (ranging from 23% to 68%). The cyclization initially formed the non-isolated intermediate i, which was oxidized by molecular oxygen from air, introducing the hydroxy group at the α-position of the cyano group. The protocol utilised mild conditions and short
Chemo-enzymatic total synthesis: current approaches toward the integration of chemical and enzymatic transformations
Beilstein J. Org. Chem. 2024, 20, 1693–1712, doi:10.3762/bjoc.20.151
- well as their analogs, is outlined with an emphasis on comparing these chemo-enzymatic syntheses with the corresponding natural biosynthetic pathways. Keywords: chemo-enzymatic synthesis; late-stage modification; reactive biosynthetic intermediate; regio- and stereoselective (macro)cyclization; total
- stereoselective cyclization reactions. This review aims to provide an overview of these approaches and parallel comparisons with original biosynthetic pathways by highlighting five examples of chemo-enzymatic total syntheses of natural products reported since 2017. The examples are the synthesis of cotylenol (1
- , and subsequent reduction of the exomethylene at C11–C18 catalyzed by BscH yield brassicicene O (12). Renata and co-workers successfully accomplished the chemoenzymatic total syntheses of cotylenol (1) and nine brassicicenes (Scheme 3) [19]. In the cyclization phase, a suitably functionalized 5/8/5
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