Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• intermediate. Subsequently, following the production of an oxide ion through the ring-opening reaction of the 2,5-dihydrofuran ring, the oxide ion attacks another TCNEO molecule. This sequence culminates in the elimination of the tetracyanodioxetane moiety (either as dioxetane or carbonyl dicyanide molecules

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• activation of anilides 114 (Scheme 20) [63]. When the optimized conditions were applied to azabenzonorbornadiene derivatives, the dehydrative naphthylation sequence did not occur with the reaction being exclusive for exo-ring-opened products, similar to that observed in a typical Rh-catalyzed ring-opening

• reaction (vide infra). The reaction seems to be sensitive to the steric bulk of the amide functionality with n-propyl and isopropylamides having diminished yields. While the scope of anilides was quite extensive, electron-deficient substrates resulted in lowered yields. In 2022, the Jeganmohan group

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• ones. Substitution In 2008, the Rebek group reported a very intriguing site-selective ring-opening reaction of epoxides mediated by cavitand host I, which possessed an inwardly directed carboxylic acid module (Figure 11) [72]. The ring-opening of substituted epoxides results in regioisomeric products

• exclusively (Figure 11c). However, a control experiment using the model acid 38 afforded a mixture of 5- and 6-membered products. The introduced acid module facilitated the ring-opening reaction, and the CH–π interactions between the aromatic walls of the host and the alkyl backbone of the substrate induced

• . Site-selective monoepoxidation of α,ω-dienes mediated by the water-soluble cavitand host E. Site-selective ring-opening reaction of epoxides mediated by cavitand I with an inwardly directed carboxylic acid module. Site-selective nucleophilic substitution reaction of allylic chlorides mediated by cage

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• (EDGs) led to naphthol compounds 9, while electron-withdrawing groups (EWGs) led to the anticipated ring-opened 1,1,2-trisubstituted naphthalene framework 10 [61]. On the other hand, Edmunds and co-workers described a ring-opening reaction of C1-substituted OBDs 5 with arylboronic acids that was

Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives

• İlknur Polat,
• Selçuk Eşsiz,
• Uğur Bozkaya and
• Emine Salamci

Beilstein J. Org. Chem. 2022, 18, 77–85, doi:10.3762/bjoc.18.7

• material in the synthesis of the other isomer of β-amino acid 6. The ring-opening reaction of 7 with HCl(g) in MeOH resulted in a mixture of products 8 and 9 in a 9:1 ratio (1H NMR). The product 8 in the reaction mixture was purified by recrystallization from ethanol/ether, but all attempts to purify the

• the epoxide-ring-opening reaction of 7 with sodium azide, to introduce an extra amino group in position 4 on the cyclooctane skeleton. For this, epoxide 7 was treated with NaN3 in the presence of NH4Cl/DMF and this formed lactone 13 as the sole product in 80% yield (Scheme 4). The epoxide 7 was

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

• Yuki Yamamoto,
• Akihiro Tabuchi,
• Kazumi Hosono,
• Takanori Ochi,
• Kento Yamazaki,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

• –Volhard–Zelinsky-type ring-opening reaction of 1a (Table 1). In this reaction, the corresponding acid bromide is formed in situ by heating with Br2 and a substoichiometric amount of PBr3; the acid bromide is then converted into 2,5-dibromopentanoic acid (2a) via hydrolysis during the workup under open-air

• -ECX400 (100 MHz) FT NMR or JEOL JNM-ECS400 (100 MHz) FT NMR system in CDCl3. Ring-opening reaction of δ-valerolactone (1a) with Br2 in the presence of a catalytic amount of PBr3 (entry 1, Table 1). To a 50 mL three-neck flask were added δ-valerolactone (1a, 5 mmol) and PBr3 (5 mol %), then Br2 (1.0 equiv

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• byproducts were detected which supports the absence of an initial oxidative addition between the alkyl iodide and the active Fe catalyst. The possibility of a radical process rather than ionic cross-coupling is supported by the tandem cyclization/cyclopropyl ring-opening reaction, similar to previous reports

Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation

• Lukáš Ďurina,
• Anna Ďurinová,
• František Trejtnar,
• Ľuboš Janotka,
• Lucia Messingerová,
• Jana Doháňošová,
• Ján Moncol and
• Róbert Fischer

Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188

• terminal alkenes bearing both an allylic and homoallylic-type hydroxy group, yielding a sole threo isomer, are rare [36]. The cyclization of 5 through an epoxide ring-opening reaction with boron trifluoride etherate in dichloromethane at 0 °C yielded pyrrolidine derivative 12 in 69% isolated yield [37

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• thioglycosides prepared from deoxyfluorinated 1,6-anhydro-2-azido-β-ᴅ-hexopyranose precursors by ring-opening reaction with phenyl trimethylsilyl sulfide. Nucleophilic deoxyfluorination at C4 and C6 by reaction with DAST, thioglycoside hydrolysis and azide/acetamide transformation completed the synthesis

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• the observed product. Only diarylimines were utilized in this study, largely because of their ease of preparation and stability. Ring-opening reaction of gem-difluorocyclopropylstannanes: Konno and co-workers reported the conversion of cyclopropylstannanes 117 into monofluoro derivatives of allylic

• Nazarov cyclization with the strong silylating agent Me3Si+ B(OTf)4− to afford the corresponding 2-fluorocyclopentenone derivatives, e.g., compound 124 (Scheme 54) [37][90]. Radical-mediated ring-opening reaction: The photochemical iodine atom-transfer ring opening of 1,1-difluoro-2-(1-iodoalkyl

• -difluorocyclopentenes 131 in good to excellent yields [106]. A convenient route to 2,2-difluoro-homoallylic alcohols 133 occurred by photo-irradiative aerobic oxidation (Scheme 57) [107]. The reaction proceeded by the light-mediated ring-opening reaction of gem-difluorocyclopropane 132 in the presence of an organic dye

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• Z-oct-4-ene in toluene was found to be a more effective alkene source for the ring-opening reaction in comparison to the gaseous ethylene, as it increases solubility and also improve the lifetime of the catalyst. 2.1 Derivatization at benzylic position As can be inferred from the architecture of

• dimethyldioxirane (DMDO) gave the triepoxy compound 104 in decent yield. Next, the methoxymethyl groups were installed by means of ring-opening reaction of 104 with LDA followed by protection of thus-created hydroxy groups in the presence of NaH/MeI to afford compound 105. Compound 105 was then transformed into 106

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• -opening reaction with bromide ions, even in the presence of bulky substituents. Keywords: acyclonucleotide; fluorine; monofluoroalkene; oxetane; selective ring-opening reaction; tetrasubstituted alkene; Introduction The introduction of fluorine atoms into organic compounds is known to modify their

• envisioned an alternative approach starting from fluoroalkylidene-oxetane derivatives and to the end we have studied the selectivity of the oxetane ring-opening reaction (Figure 3). Results and Discussion The preparation of a series of fluoroalkylidene-oxetanes 1–3 was previously reported from 3-oxetanone

• % conversion was reached after 24 h. An improved E/Z ratio of 25:75 was determined for this reaction and compound 1c was isolated in 65% yield (Table 1, entry 3). In this case the nucleophilic ring-opening reaction appeared to be controlled by steric repulsions between the bulky benzothiazolyl and

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• performed. Formation of oxazolidinone 9f There are two possible channels for the cyclization reaction of epoxide 7f with CSI to form oxazolidinone intermediates 10 and 11 as shown in Figure 1. In both transition states it is found that the ring-opening reaction of the epoxide, a nucleophilic attack of N4

Synthesis of Streptococcus pneumoniae serotype 9V oligosaccharide antigens

• Sharavathi G. Parameswarappa,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2020, 16, 1693–1699, doi:10.3762/bjoc.16.140

• the β-disaccharide 16 (Scheme 2). A ring-opening reaction followed by subsequent glycosylation of 19 with orthogonally protected thioglucoside 10 gave trisaccharide 21 in moderate yield. To improve the yield, the nucleophilicity of the disaccharide acceptor 19 (Scheme 2) was altered by replacing the

• benzoate esters in 16 by a benzyl ether leading to compound 17. The latter then was converted into the more reactive acceptor 20 via a ring-opening reaction. Glycosylation of 20 with thioglucoside 10 resulted in the desired trisaccharide 22 in almost twice the yield when compared to trisaccharide 21

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

• Kazuyuki Sato,
• Akira Kawasaki,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2020, 16, 1411–1417, doi:10.3762/bjoc.16.117

• or from isoxazoles 2 through a ring-opening reaction (Scheme 3). Based on the above observations, we attempted to introduce a fluorine atom into BKIs to access the corresponding α-fluorinated boron ketoiminates (F-BKIs, 9). First, we started from 1,3-diketones 1 and reacted them with ammonium formate

• diketone (Scheme 5). As an alternative method to synthesize F-BKIs 9, we turned our attention to the ring-opening reaction of isoxazoles. The reductive cleavage of the N–O bond in isoxazoles can be achieved by transition metals or their complexes to give the corresponding enaminoketones [35][37

• 8 and their conversion to BKIs (yields refer to isolated yields; aboron complexation of 8a to 9a was not attempted). Attempted selective fluorination of BKI 6b. Ring-opening reaction of 4-fluoroisoxazoles 3 and their conversion into F-BKIs 9 (yields refer to isolated yields). UV–vis absorption and

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• underwent a ring-opening reaction to afford pyrrolizinones 342. In case of N-but-3-enyl-5-thiopyrrolidin-2-one (338a, R = H) the reaction afforded the product 7-mercaptomethyl-1,2,5,6-tetrahydropyrrolizin-3-one (340) directly in 68% yield under photo irradiation. However, N-(3-methylbut-3-enyl)-5

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• heterogeneous species, the CAHOF F-1 and methanol were mixed together and stirred for 15 minutes. Then, the remaining solid F-1 was removed by filtration, and the filtrate was tested as a catalyst for the ring opening reaction. The alcohol 3 was obtained in 67% yield (Table 1, run 4), proving that some soluble

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• derivatives by HF/Py The ring opening reaction of aziridines 138a,b by treatment with hydrogen fluoride in pyridine afforded 3-fluorophenylalanine esters 139a,b. The subsequent enzymatic hydrolysis of esters 139a,b gave the threo-isomer 136 in an enantiomerically pure form [68][69] (Scheme 31). On the other

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• access various derivatives, such as 12 and 13, derived from the trapping and Baeyer–Villiger oxidation of 11, respectively, or compound 16, obtained via the ring opening reaction of 15 with an amine (Scheme 5). Taking the enolate intermediate derived from the addition of EtMgBr to coumarin as an example

• co-workers elaborated the copper-catalysed ring opening reaction of oxabicyclic alkene substrates using organolithium reagents, finding excellent anti selectivities and enantioselectivity (Scheme 12) [42]. During the optimisation studies, they discovered that when the Lewis acid BF3·OEt2 was employed

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• a certain extent Hg2+) initially induced a ring-opening reaction that was irreversibly followed by a fast ring closure–deprotonation–oxidation sequence to give styryl-substituted naphthoxazole derivatives as the products quantitatively. For the quinolizinium-substituted spirooxazine derivative, the

• ., 1aSO: λabs = 317 nm, 1aMC: λabs = 602 nm, in MeCN) [16]. In some instances, the ring-opening reaction may also be induced in the dark through the addition of particular metal cations that are able to coordinate to the phenolate oxygen atom and/or other additional coordinating atoms and substituents

• that have been introduced into the structure of the spirooxazine and spiropyran derivatives [17][18][19][20][21][22][23][24][25][26]. Regardless of whether the ring-opening reaction is induced by cations or irradiation, the coordination of metal ions to the substrate usually results in a negative

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• 25 was suppressed under the same conditions (Table 2, entry 3). The SnCl4-catalyzed acetolysis of tribenzylated 25 offered the acetolysis product 26 in a low yield (27%) and occurred faster than with 6 and 21. The fast ring-opening reaction of 25 might have been attributed to the presence of three

• , SnCl4 and Sn(OTf)2 might have formed a coordination bond with the carbonyl oxygen atom of the C-5 NHAc group and the O-6 position of the glucose glucopyranosyl ring. In turn, this retarded the ring-opening reaction. The anchimeric participation of the NHAc group in stabilizing the axial conformation of

• . R = Me, Bn, PG = electron-donating protecting groups, electron-withdrawing protecting groups. Synthesis and acetolysis of 2,7-anhydro derivatives 21 and 25. Attempted acetolysis of 2,7-anhydro-NeuN3-based disaccharides 29, 33, and 37. Optimization of the ring-opening reaction of 6. Substantiation of

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• used to give a reasonable quantitative estimation of the upconversion phenomenon. In particular, we will exploit the ring-opening reaction since only the closed form 1-c presents a good spectral overlap with the visible emissions of the Er-UCNPs. In order to achieve a “user friendly” quantitative

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• hands, a selective epoxide ring-opening reaction with fatty acids 3 leading to the formation of the corresponding sn-1,3-protected monoacylglycerols (MAGs 4) was attempted (Scheme 3). Initially, commonly used solution-based protocols were tested in the ball mill [33]. For example, 2 was reacted with

• stearic acid (3a) in the presence of amines such as pyridine or tributylamine. However, the analysis of the reaction mixture only showed unreacted starting materials. In previous work, an acceleration of the oxirane ring-opening reaction with carboxylic acids [34] or alcohols [35] by using Lewis acid

• a promising one to mechanochemically access MAGs by ball milling. Experimentally, we attempted the cobalt-catalyzed epoxide ring-opening reaction by milling 2 with stearic acid (3a) in the presence of (S,S)-cat (2.5 mol %) and N,N-diisopropylethylamine (DIPEA; 1.0 equiv, Scheme 3a). Mechanistically

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• NMR analysis of the crude reaction mixture. Indeed, a slow ring-opening reaction took place upon standing in solution to mainly give the isoxazole isomer 28 along with much less of the target oxazole-bearing α-hydroximino ester 29. Extensive trials to alter the selectivity of the ring opening using

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• cyclooctene-fused isoxazoline (±)-16. ROM and transformations of lactam (±)-18. Isolated yields for compound (±)-5 formed in the ring-opening reaction of lactone (±)-3 with ethylene in ROM reactions with various catalysts. Isolated yields for compound (±)-6 formed in the ring-opening reaction of lactone (±)-4

• with ethylene in ROM reactions with various catalysts. Isolated yields for compound (±)-10 formed in the ring-opening reaction of lactone (±)-9 with ethylene in ROM reactions with various catalysts. Isolated yields for compounds formed in the ring-opening reaction of lactone (±)-14 and isoxazoline

• (±)-16 with ethylene in ROM reactions with various catalysts. Isolated yields for compound (±)-19 formed in the ring-opening reaction of lactam (±)-18 with ethylene in ROM reactions with various catalysts. Isolated yields for compound (±)-20 formed in the reaction of lactam (±)-19 in CM reactions with