Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• [(6-NHC)CuMes] with t-BuOH. It was found that the diaminocarbene derivative was more thermally stable whereas the diamido derivative underwent both thermal and hydrolytic ring-opening reactions (Scheme 13). Demir Atli and co-worker, in 2018, synthesized a cationic (NHC)2Cu(I) complex 39 in very good

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• starting from both cyclic and acyclic alkyl bromides. The findings of the reaction’s stereochemistry and observations made during some cyclization or ring-opening reactions indicated that the C–H alkylation may proceed through a radical-type mechanism. Next, in 2013, Wang and co-workers [52] reported a

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• obtained by the deoxofluorination of the corresponding dicarboxylic acids with sulfur tetrafluoride, thiophilic ring-opening reactions with nucleophiles or reactions of donor-substituted furans with bis(trifluoromethyl)-substituted ethylenes (Scheme 1D) [41][42][43]. The lack of application of highly

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

• -stereocontrolled ring-opening reactions of oxa- and azabicyclic olefins with dialkylzinc reagents catalyzed by a nickel compound (Scheme 1) [60]. The reaction was entirely stereoselective; however, unsymmetrical OBDs 5 produced mixtures of regioisomers 6 and 7. In the same year, Hill and co-workers published a

• reported metal-catalyzed reactions of heterobicyclic alkenes and applications towards the synthesis of biologically active compounds (top). Representative examples of regioselectivity in different metal-catalyzed ring-opening reactions of C1-substituted oxabenzonorbornadiene derivatives (bottom left

• -opening reactions of heterobicyclic alkenes are of particular interest [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], as they provide access to a broad family of synthetic building blocks bearing multiple stereocenters in a single step 2 [54]. Application of these functionalized

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

• -valerolactone 6. Ring-opening reactions of lactones with Br2 in the presence of a substoichiometric amount of PBr3a. Optimizing the intramolecular cyclization of 2a in a two-phase systema. Optimizing the base for the intramolecular cyclization of 2a to 3aa. Reaction scope for the the intramolecular cyclization

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• makes asymmetric ring-opening reactions a powerful tool for the synthesis of highly complex target molecules. With this concept in mind, anion-binding catalysis has successfully been employed for asymmetric ring-opening reactions, implying halide anions as both mere counter-anions in the ion-pair

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

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

• . It will examine the role of the fluorine substituents in both ring-forming and ring-opening reactions, as well as methods for obtaining difluorocyclopropanes as single enantiomers. Several examples are provided to highlight the biological importance of this class of compounds. Keywords: biological

• -difluorocyclopropanes. First, we discuss the synthetic routes to gem-fluorocyclopropane derivatives. Then, we review the chemical transformations, emphasizing ring-opening reactions. Finally, we survey the biological activity of significant molecules that possess the 1,1-difluorocyclopropane fragment in the structure

• selection of the reagents and catalysts. These have an influence on the mechanism and regioselectivity of the C–C bond cleavage. Although there are several different mechanisms for ring-opening reactions, in most cases there is a cleavage of the most weakened C–C bond due to the fluorine effect. This C–C

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• -opening reactions (Scheme 11) [58]. The synthesis commenced with the smooth ring opening of the methyl-substituted lactone 90 using lithium bromide, which gave a single trans-cyclobutenyl bromide 91. Then, the bromocyclobutene 91 was submitted to further amide coupling and 4π electrocyclic ring opening to

• contradictions regarding the specific rotation values of inthomycin C and securely assigned the (3R)‑configuration for inthomycin C ((−)-3) [57]. In the synthetic studies towards racemic inthomycin C ((rac)-3), Maulide and co-workers investigated the stereoselective synthesis of halocyclobutenes and their ring

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

• through an olefination reaction with benzothiazoyl sulfones (Scheme 1) [22]. With these fluoroalkylidene-oxetanes in hands, we studied the selectivity of ring-opening reactions with heteroatom nucleophiles in order to access tetrasubstituted fluoroalkenes. A control of the geometry of these reactions

• , where the β-hydroxymethyl-γ-lactone 14 was obtained, confirmed an electronic influence of the fluorine atom on these ring-opening reactions (Table 3, entries 1 and 2). In the case of fluoroalkylidene-oxetane 12 and, in contrast with 16, when subjected to HBr/AcOH, the electronic repulsion induced

• was achieved but also with impurities. This route was not investigated further, and instead functionalization of alkene E-1d was explored. Direct ring-opening reactions of fluoroalkylidene-oxetane 1 with heteronucleophiles were previously explored and success was only possible with thiols, such as

Recent synthesis of thietanes

• Jiaxi Xu

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

• thiiranes 419 from the least substituted ring carbon atom generated the zwitterionic intermediates 427, with a good regioselectivity following the general regioselectivity rule in nucleophilic ring opening reactions of aliphatic three-membered heterocycles [124][125][126][127][128][129][130][131][132]. The

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

• catalyst for the Brønsted acid-catalyzed ring opening reactions of epoxides with alcohols and water, with the latter reaction occurring in a three-phase medium. In addition, a Diels–Alder reaction was promoted by F-1 in heptane. Results and Discussion Mixing together aqueous solutions of two equivalents of

• ). Both the pH of the medium (specific acid catalysis) and general acid catalysis by the ammonium groups of F-1 were potentially important for the ring opening reactions. The ring openings were conducted in three different media: neat methanol, a mixture of methanol and dichloromethane, and a mixture of

• “breathing”. The material served as a new type of Brønsted acid catalyst in a series of reactions, including epoxide ring opening reactions and a Diels–Alder reaction. A second role for NDS was that one of its sulfonate oxygen atoms could form hydrogen bonds with water whilst leaving the other two oxygen

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

• reaction, two seven-membered heterocyclic bisphosphates (O- and N-containing, respectively,) underwent Cu/L15-catalysed AAAs and provided the corresponding chiral products with good yield and high enantioselectivity (92–93% ee) [40]. Ring opening reactions where carbon–carbon bonds are formed upon the

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• PhMe2Si group could also be prepared in moderate yield (276). The regiocontrolled ring opening reactions of the same aryl-substituted aziridines 277 have also been shown by Minakata and Takeda et al. to be susceptible to dual Pd/Cu catalysis. Depending upon the ligand on each metal, either the 2 or 3

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• and a mixture of petroleum ether/ethyl acetate as eluent. Comparison of different ring-opening reactions of 2-oxazolines and thiazolidinones synthesis. KOt-Bu-promoted selective ring-opening N-alkylation of 2-methyl-2-oxazoline with benzyl bromides. Conditions: KOt-Bu (0.5 mmol), 2-methyl-2-oxazoline

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• lithium halogen elimination, halide migration, and ring-opening reactions [56][57]. Butylphosphines are also formed alongside the main product, and in most cases pure phosphine pyridines are obtained using column chromatography followed by extractions adding to the number of synthesis steps. This method

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

• order to access glycans in a pure form. In line with this, various C-5-substituted 2,7-anhydrosialic acid derivatives bearing both electron-donating and -withdrawing protecting groups were synthesized and subjected to different Lewis acid-catalyzed solvent-free ring-opening reactions at room temperature

• the hydroxymethyl group in 10 to furnish 11 in 82% yield. After having obtained the 2,7-anhydrosialic acid derivatives 5–11, they were subjected to various Lewis acid-catalyzed ring-opening reactions. In line with this, Sc(OTf)3-, copper(II) triflate-, and SnCl4-catalyzed acetolysis of diacetylamino

• 8 only affording an unidentifiable mixture of compounds. Similarly, the 2,7-anhydro backbone of 11 was not cleaved under the above conditions and results in either recovered starting material or unidentifiable mixtures. Differently, ring-opening reactions of 6 with BF3⋅OEt2, TMSOTf, and Sc(OTf)3 in

An improved, scalable synthesis of Notum inhibitor LP-922056 using 1-chloro-1,2-benziodoxol-3-one as a superior electrophilic chlorinating agent

• Nicky J. Willis,
• Elliott D. Bayle,
• George Papageorgiou,
• David Steadman,
• Benjamin N. Atkinson,
• William Mahy and
• Paul V. Fish

Beilstein J. Org. Chem. 2019, 15, 2790–2797, doi:10.3762/bjoc.15.271

• yields of the desired product 7 (ca. 15–32%) due to competing ring opening reactions of the 7-cyclopropyl group (Scheme 2). Clearly, a better procedure was required. A large number of electrophilic chlorinating reagents for the direct chlorination of aromatic rings have been reported [17]. Recently, Xue

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• -opening reactions; see Table 2). Second, a bithiophene residue induces a red-shift of 30–35 nm in the absorption of the OF with respect to a mono-thiophene ring. The oxidized DAEs (OF) absorbed at higher wavelengths than the corresponding nonoxidized analogs (by ca. 20–30 nm), and a splitting of the band

• that in the OF each benzothiophene unit (with aligning thiophene group(s)) contributes into absorption independently. It was confirmed that asymmetric compounds with “compact” structures can be transformed to the closed form with the same light as bulkier analogs (the latter featuring slower ring

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• –C bond formations, and ring opening reactions [83][84][85][86][87]. Along with these nickel and vanadium were also well known to catalyze a number of organic reactions. Recent reviews published on the catalytic applications of these metals in various forms have underlined the indispensable

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

• -opening reaction of 2 with stearic acid (3a) was evaluated (Scheme 3a). Specifically, we focused on the use of Jacobsen cobalt(II)-salen complex (S,S)-cat (Scheme 3b), since similar salen complexes had originally been reported to facilitate epoxide ring-opening reactions with carboxylic acids as

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• can take part in ring-opening reactions under certain conditions. Cyclopropane derivatives, with their three-membered carbocyclic frameworks, have spurred considerable attention especially in the domain of organic and pharmaceutical synthesis because of their highly strained three-membered carbocyclic

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

• (synthesized from 1,3-cyclohexadiene (7) through lactam (±)-8) [26] was subjected to ring-opening reactions with all four catalysts. It should be noted again, that based on our earlier findings [15], bicyclic lactam (±)-8 did not provide any ring-opened product, while bicyclic lactone (±)-9 could be opened

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• of 75–96% (Scheme 18). The reaction showed a broad substrate scope in terms of epoxides and aromatic thiols. Most recently, Kumar et al. synthesized Eu3+- and Tb3+-based coordination polymers (CPs) which function as reusable heterogeneous catalysts for ring-opening reactions utilizing amines

• aromatic thiols. Ring-opening reactions of cyclohexene oxide with thiols by using CPs 1-Eu and 2-Tb. CBS-oxazaborolidine-catalyzed borane reduction of β-keto sulfides. Preparation of β-hydroxy sulfides via connectivity. Baker’s yeast-catalyzed reduction of sulfenylated β-ketoesters. Sodium-mediated ring

Diels–Alder cycloadditions of N-arylpyrroles via aryne intermediates using diaryliodonium salts

• Huangguan Chen,
• Jianwei Han and
• Limin Wang

Beilstein J. Org. Chem. 2018, 14, 354–363, doi:10.3762/bjoc.14.23

• of this transformation are underway in our laboratory. Arylations of pyrrole derivatives with diaryliodonium salts. Formation of N-phenylamine derivatives 4 and 5 via ring opening reactions. Preparation of product 6 by hydrogenation. Optimization of reaction conditions.a Scope of diaryliodonium salts