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Search for "intramolecular" in Full Text gives 1316 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series
Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23
- relied on an intramolecular RCM reaction on compound 74 between the two terminal olefins, that could lead to the formation of a trisubstituted double bond (compound 75), and further access to the required α-methyl ketone. However, despite many attempts, no cyclization occurred. Indeed, the disubstituted
- was not controlled, yielding a mixture of stereoisomers. Recent developments were undertaken to propose an asymmetric version [56][57]. In its intramolecular version, the NHK reaction was successfully applied by Kishi in 1989 to forge the cyclooctane ring of ophiobolin C (30) [5-8-5] framework, thus
- ., compound 122 for further derivatization and structure–activity relationship (SAR) studies [59]. In this case, an intramolecular NHK was carried out on compound 120 prepared from 3-allylcyclopent-2-enone (119) to give the tricyclic compound 121 possessing the eight-membered ring in 73% yield as the major
An accelerated Rauhut–Currier dimerization enabled the synthesis of (±)-incarvilleatone and anticancer studies
Beilstein J. Org. Chem. 2023, 19, 204–211, doi:10.3762/bjoc.19.19
- intermolecular fashion to form a C–C bond between the two Michael acceptors. This whole process involves two intermolecular conjugate additions, which leads to low reactivity. In case of intramolecular RC reactions, a high reactivity is observed. This is due to one intermolecular and one intramolecular conjugate
- addition reaction involved. The low reactivity of intermolecular RC reactions can be improved by incorporating the nucleophilic functionality within a molecule like I (Scheme 1). This nucleophilic functionality present within the enone system first undergoes an intramolecular conjugate addition and is
- followed by an intermolecular conjugate addition to form a C–C bond (path A). In an alternative approach (path B) first I undergoes a nucleophilic conjugate addition in intermolecular fashion to give intermediate III and followed by an intramolecular addition to give compound IV. In both paths, the
Germacrene B – a central intermediate in sesquiterpene biosynthesis
Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18
- this multistep process is initiated by the abstraction of diphosphate to produce an allyl cation that subsequently undergoes typical cation reactions such as cyclisations by intramolecular attack of an olefin to the cationic centre, Wagner–Meerwein rearrangements, hydride or proton shifts. The process
Identification and determination of the absolute configuration of amorph-4-en-10β-ol, a cadinol-type sesquiterpene from the scent glands of the African reed frog Hyperolius cinnamomeoventris
Beilstein J. Org. Chem. 2023, 19, 167–175, doi:10.3762/bjoc.19.16
- amorph-4-ene-10β-ol known from plants. A short synthesis using an organocatalytic approach through a tandem Mannich/intramolecular Diels–Alder reaction led to a mixture of cadinols, which was used for the assignment of the natural cadinol structures and their stereoisomers. Keywords: Anura; chiral gas
- triene system for an intramolecular Diels–Alder reaction. Oxidation of 8 with IBX changed the electronic properties of the system implementing an electron-deficient double bond suitable for a heat-induced intramolecular Diels–Alder reaction. The higher reaction temperature compared to the original
- using diethyl (2-methylallyl)phosphonate gave diene ketone S-18 [13]. Here, we envisioned that a Mannich reaction would introduce the required α,β-unsaturated carbonyl system needed for the following intramolecular Diels–Alder reaction, that likely would proceed directly under these conditions. This
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
- cations in cycloadditions. Harmata has briefly investigated the use of oxathiin-stabilized allyl cations with some success in intramolecular (4 + 3) cycloadditions (viz 88 → 89, Scheme 14a) [101][102]. Later, our group found that dihydrodithiinmethanol 90 acts as a very useful precursor for a range of
Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade
Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10
- activation/annulation cascade of readily available enaminones with iodonium ylides towards the convenient synthesis of isocoumarins. This coupling system proceeds in useful chemical yields (up to 93%) via a cascade C–H activation, Rh-carbenoid migratory insertion and acid-promoted intramolecular annulation
- for the synthesis of isocoumarin scaffolds. Traditional synthetic strategies including 1) intramolecular cyclization of 2-alkenyl benzoic acids or o‑alkynylbenzoates (Scheme 1b, I) [6][7][8][9][10], 2) oxidation of isochromans (Scheme 1b, II) [11][12], or 3) metal-catalyzed cross-coupling/cyclization
- , which undergoes an intramolecular annulation to give 1-F. The final isocoumarin product 3ba can be generated from 1-F by elimination of imine 1-G [39]. Finally, the rapid hydrolysis of the resulting 1-G gives rise to acetaldehyde and dimethylamine as byproducts. Conclusion In summary, an efficient Rh
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
- on the success of the catalytic aza-Nazarov reaction. Keywords: α-methylene-γ-lactam; aza-Nazarov reaction; β-silicon effect; heterocycles; intramolecular cyclization; Introduction The rapid construction of aliphatic heterocycles from acyclic building blocks via cyclization or cycloaddition
Combining the best of both worlds: radical-based divergent total synthesis
Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1
- [16]. Based on their reactivity, major contributions in carbon-centered radical formation followed, consequently unlocking highly predictable intramolecular reactions, deoxygenation protocols (Barton–McCombie reaction) [17], etc. Other reagents that majorly contributed were samarium diiodide for the
- and the aromatic moieties present in these natural products and provided the common synthetic intermediate 70 (Scheme 6). The diverse tetracycles were accessed either via an intramolecular radical cyclization of the reduced congener 73 or through a Heck reaction of intermediate 71. Reaction of 73 with
- asymmetric conjugate reaction of commercially available 81 and 82 using Fletcher’s protocol (94% ee) [44]. A subsequent intramolecular arylation in the α-position of the ketone of 83, catalyzed by a Pd(II)–NHC [45], followed by methylation, provided cis-decalin 84 (Scheme 7). Appropriate redox modifications
Total synthesis of grayanane natural products
Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181
- synthesis started from 3-hydroxy-2-methoxybenzaldehyde (34), which was converted into Grignard reagent 35 and added onto 3-methylbut-2-enal (Scheme 6). A sequence involving Claisen rearrangement, Roskamp homologation, diazo transfer and intramolecular cyclopropanation led to intermediate 37. The hydroxy
- synthetic route based on a convergent strategy to accomplish the synthesis of principinol E, grayanotoxin III and rhodomollein XX [34]. The key steps include i) a tandem reaction combining organocatalytic Mukaiyama aldol and intramolecular Hosomi–Sakurai reactions in a one-pot manner; ii) a 7-membered
- transformations include the removal of the ketone on the C ring, epoxide reductive opening, formation of the B ring exo-olefin, and glycosylation. In 2021, Hong et al. presented a synthetic effort focused on the synthesis of rhodojaponin III B–C rings [40]. The authors employed a Mn(III)-mediated intramolecular
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
- substrates. DDQ is a popular mediator for oxidation reactions. It has been used for intramolecular dehydrogenative C–C bond formation between aromatic groups [127]. Using this method, the formation of polyaromatic systems was achieved in good yields (Scheme 26). The cross-dehydrogenative C–N coupling of
- of a hydroperoxide (terminal oxidant) on a ketone or imine, respectively, is followed by intramolecular cyclization with O–O bond cleavage and the formation of a strained 3-membered ring, an electrophilic oxygen atom donor for oxidative processes (Scheme 30). It should be noted that in the ketone
- oxidative organocatalysis. Electrochemical DDQ-catalyzed intramolecular dehydrogenative aryl–aryl coupling. DDQ-mediated cross-dehydrogenative C–N coupling of benzylic substrates with azoles. Biomimetic o-quinone-catalyzed benzylic alcohol oxidation. Electrochemical synthesis of secondary amines by
A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition
Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177
- insertion of carbenes derived from diazo arylidene succinimides (DAS) into the O–H bond of phenols is described. The initial adducts underwent a thermally promoted Claisen rearrangement followed by DABCO-catalyzed intramolecular 5-exo-trig oxa-Michael addition. Keywords: Claisen rearrangement; diazo
- arylidene succinimides; intramolecular oxa-Michael addition; rhodium(II) carbene O–H insertion; spirocycles; Introduction Spirocycles undoubtedly occupy a special place in drug design [1] and, in general, spirocyclic compounds intended for the interrogation of biological targets have been associated with
- ) would again have a reactive phenolic hydroxy group which could potentially be involved in post-condensational transformations such as intramolecular oxa-Michael addition (Scheme 1). Herein, we report our findings obtained in the course of investigating the viability of this strategy. Results and
Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone
Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176
- , Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan, Faculty of Pharmaceutical Sciences, Hiroshima International University, 5-1-1 Hirokoshingai, Kure, Hiroshima 737-0112, Japan 10.3762/bjoc.18.176 Abstract A rhodium-catalyzed intramolecular reductive aldol-type cyclization is
- structural component of the pyrrolizidine alkaloid monocrotaline. Keywords: β-hydroxylactone; intramolecular reductive aldol cyclization; necic acid lactone; rhodium catalyst; Introduction Carbon–carbon bond-forming reactions are among the most important reactions in the synthetic chemistry toolbox and the
- aldol reaction is one of the most powerful tools to achieve this transformation [1][2][3][4][5][6][7][8]. In particular, the intramolecular aldol condensation is an important approach to the formation of ring systems such as cyclic β-hydroxy carbonyl products or cyclic α,β-unsaturated carbonyl products
A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction
Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175
- proceeded further, in uncatalyzed fashion at room temperature and yielded, after intramolecular azide–alkyne click reaction novel, structurally intriguing bistriazoles. Keywords: α-acetyl-α-diazomethane sulfonamide; intramolecular click reaction; uncatalyzed; room temperature; 1,2,3-triazoles
- ) [6]. Indeed, if an alkyne and an azido group were strategically positioned within the structure of the amine and the aldehyde components for the reaction with 1, subsequent intramolecular azide–alkyne cycloaddition would be a feasible event which would create a polycyclic bis-1,2,3-triazole framework
- ]bis([1,2,3]triazolo)[1,5-a:1',5'-d][1,4]diazepine (5a), i.e., the product of the tandem three-component 1,2,3-triazole synthesis followed by intramolecular azide–alkyne click reaction which, apparently, proceeded at room temperature. Product 5a was isolated in respectable 78% yield; therefore, the
Synthesis of (−)-halichonic acid and (−)-halichonic acid B
Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174
- (−)-α-bisabolol. The optimized synthetic route includes a new purification method for isolating (−)-7-amino-7,8-dihydrobisabolene in enantiomerically pure form via recrystallization of its benzamide derivative. The key intramolecular aza-Prins reaction forms the characteristic 3-azabicyclo[3.3.1]nonane
- derived from a common biosynthetic pathway starting from farnesyl pyrophosphate and glycine [5]. This prompted us to investigate a biomimetic synthesis in which the halichonic acids could be prepared from a common imine intermediate via divergent intramolecular aza-Prins cyclizations [8]. Herein, we
- configuration was not rigorously established, we have assigned it as the (E)-isomer, as is commonly observed in aldimine formation. The stage was now set for the key intramolecular aza-Prins reaction that would form the bicyclic structures of the halichonic acids (Scheme 2). When a solution of imine 7 in
Synthetic study toward the diterpenoid aberrarone
Beilstein J. Org. Chem. 2022, 18, 1625–1628, doi:10.3762/bjoc.18.173
- were reported [30][31] and more recently, Carreira and co-workers reported [32] the first total synthesis of aberrarone through an impressive cascade reaction including a gold-catalyzed Nazarov cyclization, a cyclopropanation followed by intramolecular aldol reaction to forge the A, B and D rings
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
- substituted rims are partially methylated CDs. Methylation reduces the formation of intramolecular hydrogen bonds, enhancing CDs water solubility, and also extends the hydrophobic cavity, thus improving its binding potential. A substantial increase of binding constant (K) for per-6-methylated CD compared to
- bonding. The presence of tetracene in the solution enhances inter- or intramolecular associations of CD rings in dimers. The CD dimer 5, linked with urea, demonstrated stoichiometry close to unity. Still, dimers 4 and 10, linked with triazole-based spacer, exhibited strong exothermic interaction at an
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 authors revealed the product 4a as E-isomer due to the strong intramolecular H-bonding. It was also observed that the labile acetal group in the product 4g remained unaffected during the reaction process under the standard conditions. Imidazole N-oxides reacted with ethyl cyanoacetate to produce
- perfluoroaryl-substituted 2H-imidazole products, a push–pull fluorophore system was discovered, which can be useful for the preparation of fluorometric sensor materials because of the solvent-dependent intramolecular charge transfer effect (ICT). Here, two reaction pathways were designed: (A) addition
A study of the DIBAL-promoted selective debenzylation of α-cyclodextrin protected with two different benzyl groups
Beilstein J. Org. Chem. 2022, 18, 1553–1559, doi:10.3762/bjoc.18.165
- debenzylated almost similarly other than the DCB removal at the primary rim is somewhat slower. Debenzylation on the secondary rim does not occur before DCB groups have been removed on the primary side supporting the hypothesis that the debenzylation on the secondary side is intramolecular or at least directed
A facile approach to spiro[dihydrofuran-2,3'-oxindoles] via formal [4 + 1] annulation reaction of fused 1H-pyrrole-2,3-diones with diazooxindoles
Beilstein J. Org. Chem. 2022, 18, 1532–1538, doi:10.3762/bjoc.18.162
- negatively charged [38] C(3) atom of diazooxindoles 2 at the C(3a) atom of FPDs 1 (Scheme 5), and (b) further intramolecular SN2 attack by the oxygen of the aroyl group with ensuing elimination of a nitrogen molecule. To verify our assumption, 3-bromooxindole (4) was involved in the reaction with FPD 1i in
- the presence of 1.1 equiv of TEA. In this case, the base-promoted deprotonation of 3-bromooxindole (4) affords a highly nucleophilic intermediate, which undergoes Michael addition to FPD 1i, followed by intramolecular SN2 attack [39][40][41][42][43] by the oxygen of the aroyl group (Scheme 5) to give
Comparison of crystal structure and DFT calculations of triferrocenyl trithiophosphite’s conformance
Beilstein J. Org. Chem. 2022, 18, 1499–1504, doi:10.3762/bjoc.18.157
- conformer is obviously related to the absence of stabilizing intramolecular CH···π (like in the gtt and cgt cases) or CH···Fe (like in the ttt case) interactions between neighboring fragments in the structure. The latter plays an important role from the electrostatic point of view; the NBO analysis predict
One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides
Beilstein J. Org. Chem. 2022, 18, 1479–1487, doi:10.3762/bjoc.18.155
- conventional methods; a notable alternative is the cyclodesulfurization, where intramolecular cyclization is combined with desulfurization from thioamide analogs such as thioureas, thiosemicarbazides, and dithiocarbamate salts under mild reaction conditions [10]. These synthesis methods are effective for
- constructing azoles with an amine functional group at the 2-position, such as benzoxazole or benzoimidazole, but are unsuitable for the syntheses of 2-arylated or 2-alkylated benzoxazoles and benzimidazoles. In fact, only two reports cover the subject. Jackson et al. carried out the intramolecular ring-closure
1,4,6,10-Tetraazaadamantanes (TAADs) with N-amino groups: synthesis and formation of boron chelates and host–guest complexes
Beilstein J. Org. Chem. 2022, 18, 1424–1434, doi:10.3762/bjoc.18.148
- has been developed via intramolecular cyclotrimerization of C=N units in the corresponding tris(hydrazonoalkyl)amines. In a similar fashion, unsymmetrically substituted TAADs having both amino and hydroxy groups at the bridge N-atoms were prepared via a hitherto unknown co-trimerization of oxime and
- of the obtained TAAD derivatives were performed, and the formation of boron chelates and host–guest complexes having an unusual intramolecular H-bonded network was showcased in this work. Results and Discussion Synthesis of 3N-TAADs, 2N,1O-TAADs and 1N,2O-TAADs Our strategy to construct TAAD
- derivatives involves the intramolecular cyclotrimerization of C=N bonds in a suitable trisimine precursor (Scheme 1). Previously, 3O-TAADs 2 were prepared by cyclization of corresponding trisoximes 1 [21]. However, this reaction is slow and reversible (upon heating adamantane structure 2 reverts to the tris
Characterization of a new fusicoccane-type diterpene synthase and an associated P450 enzyme
Beilstein J. Org. Chem. 2022, 18, 1396–1402, doi:10.3762/bjoc.18.144
- employs an intramolecular proton transfer. We recently showed that a water-mediated concerted deprotonation–protonation is required for the MgMS-mediated cyclization [20]. In order to probe the mechanism underlying the cyclization of 1, we used His6-tagged TadA to carry out in vitro enzymatic reactions
Synthesis of C6-modified mannose 1-phosphates and evaluation of derived sugar nucleotides against GDP-mannose dehydrogenase
Beilstein J. Org. Chem. 2022, 18, 1379–1384, doi:10.3762/bjoc.18.142
- conformation has recently been shown to be an important factor contributing to anomeric reactivity of canonical pyranoses [12]). One phenyl ring of the phosphate ester group occupied a position folded underneath the pyranose ring and engaged in an intramolecular C–H···π interaction with the axial C5 proton
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
- decided to perform its total synthesis. Results and Discussion Our synthetic strategy is based on two metal-mediated steps (Scheme 1). In this way, we thought that the 2,5-dihydrofuran structural motif that is found in the target molecule 1 could be prepared through a Ag(I)-induced intramolecular addition
- some contamination of the product with lactone 5 can arise at low pH values, which goes in detriment of the yield. The 2,5-dihydrofuran ring in target compound 1 was obtained through a Ag(I)-mediated intramolecular addition of the hydroxy to the allene group, a process that transformed allene 3 into
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