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

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

• Katrina Tait,
• Alysia Horvath,
• Nicolas Blanchard and
• William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

• Becquerel, 67087 Strasbourg, France 10.3762/bjoc.13.281 Abstract The acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicylic alkene using alcohol nucleophiles were investigated. Although this acid-catalyzed ring-opening reaction did not cleave the cyclopropane unit as planned, this

• ; alcohol nucleophiles; cyclopropanation; heterobicyclic compounds; ring-opening reactions; Introduction Heterobicyclic alkenes are useful templates to generate complex cyclic and acyclic systems [1][2]. 3-Aza-2-oxabicyclic alkenes are particularly interesting due to their asymmetric nature and the ability

• most cases, the starting material was completely consumed, the yields of these ring-opening reactions were only moderate (26–61%). This may be due to the decomposition or polymerization of the cyclopropanated 3-aza-2-oxabicyclic alkene under the reaction conditions. Through X-ray crystallography [20

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

• Tetiana Bykova,
• Nawaf Al-Maharik,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

• building blocks for discovery chemistry programmes. The synthesis starts from a Birch reduction of benzonitrile, followed by an in situ methyl iodide quench. The resultant 2,5-cyclohexadiene was progressed via double epoxidations and then hydrofluorination ring opening reactions. The resultant fluorohydrin

Palladium-catalyzed ring-opening reactions of cyclopropanated 7-oxabenzonorbornadiene with alcohols

• Katrina Tait,
• Oday Alrifai,
• Rebecca Boutin,
• Jamie Haner and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 2189–2196, doi:10.3762/bjoc.12.209

• Katrina Tait Oday Alrifai Rebecca Boutin Jamie Haner William Tam Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Chemistry, University of Guelph, Guelph, Ontario, N1G 2W1, Canada 10.3762/bjoc.12.209 Abstract Palladium-catalyzed ring-opening reactions of

• oxabenzonorbornadiene; palladium catalysis; ring-opening reactions; Introduction Heterobicyclic alkenes undergo important chemical transformations to provide highly substituted cyclic and acyclic systems [1][2]. Oxabicyclic alkene 1 specifically can undergo a variety of chemical transformations to generate highly

• conclusion, we have demonstrated the first examples of palladium-catalyzed type 2 ring-opening reactions of cyclopropanated oxabenzonorbornadienes with alcohols. The optimized conditions include PdCl2(CH3CN)2 with the alcohol nucleophile as the solvent at 60 °C or with toluene added at 90 °C to produce 2

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

• Madhuri Vangala and
• Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

• ] and the synthesis of carbamate-linked compounds using p-nitrophenyl carbonates, we herein report our results from nucleophilic ring opening reactions of DBU and DBN using p-nitrophenyl carbonates. Results and Discussion In the course of this study, we observed that in the absence of a nucleophile the

From N-vinylpyrrolidone anions to modified paraffin-like oligomers via double alkylation with 1,8-dibromooctane: access to covalent networks and oligomeric amines for dye attachment

• Daniela Obels,
• Melanie Lievenbrück and
• Helmut Ritter

Beilstein J. Org. Chem. 2016, 12, 1395–1400, doi:10.3762/bjoc.12.133

• thermo- [18] or/and pH [19] responsive polymers. Besides classical alkylation reactions, Reinecke et al. performed ring-opening reactions to insert functional groups and aromatic side chains [20][21]. Furthermore, they investigated the formation of homogeneous [22] and amphiphilic [23] N-VP networks

Regioselective palladium-catalyzed ring-opening reactions of C1-substituted oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylates

• Michael Edmunds,
• Mohammed Abdul Raheem,
• Rebecca Boutin,
• Katrina Tait and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 239–244, doi:10.3762/bjoc.12.25

• ring-opening reactions of C1 substituted 7-oxanorbornadiene derivatives with aryl iodides were investigated. The optimal conditions for this reaction were found to be PdCl2(PPh3)2, ZnCl2, Et3N and Zn in THF. Both steric and electronic factors played a role in the outcome of the reaction as increasing

• ; oxabenzonorbornadiene; palladium catalysis; regioselectivity; ring-opening reactions; Introduction Palladium-catalyzed ring-opening reactions of 7-oxanorbornadiene with aryl iodides produce unsymmetrical, highly-substituted biphenyl derivatives making this reaction a very useful tool in organic synthesis [1][2][3][4

• materials [8]. Although there are several examples of palladium-catalyzed ring-opening reactions of oxabenzonorbornadiene (Scheme 1), there is relatively little literature regarding reactions of non-aromatic 7-oxanorbornadiene systems [9][10][11][12][13]. To our knowledge, there has only been one example of

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles

• Kandasamy Rajaguru,
• Arumugam Mariappan,
• Rajendran Suresh,
• Periasamy Manivannan and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219

• character of the C(2)–N double bond is higher than a normal imine (Figure 1) [10][26][27]. The generated substituted aziridines A2 may undergo further ring opening reactions. The α-azidochalcones 1 are suitable as precursors for the generation of 2H-azirines A1, though several other methods are available

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• enormous strain and is therefore susceptible to ring-opening reactions with a variety of nucleophiles [3][4]. Such transformations lead to 1,2-heteroatom structures which are often found in pharmaceuticals and natural products. Yudin et al. described an electrochemical aziridination process where an

Regio- and stereoselective synthesis of new diaminocyclopentanols

• Evgeni A. Larin,
• Valeri S. Kochubei and
• Yuri M. Atroshchenko

Beilstein J. Org. Chem. 2014, 10, 2513–2520, doi:10.3762/bjoc.10.262

• case of 3d bearing two phenyl groups no epoxide ring opening was observed (Table 3, entries 3 and 4). Ring opening reactions for epoxides 6a,b Ring opening of epoxides 6a,b was investigated by the reaction with 9H-purin-6-amine (7d) and morpholine (7a) as the nucleophiles under the above conditions

• ring opening reactions of epoxides 3a,b, and this may be explained by the formation of 14a,b via the aziridimium intermediate 17. Based on earlier results [44], a mechanism of this transformation was hypothesized as shown in Scheme 2. The intermediate 17 is formed after the intramolecular rearrangement

• adduct due to the steric hindrance. Application of Lewis acid as a catalyst for the ring opening reactions of 6a,b provides an alternative mechanism that involves the formation of aziridinium intermediate 17. As a result, regioisomers 14a,b were obtained as the major products. Amine-based nucleophiles

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• excellent ee (up to 96%). In subsequent transformations, the β-lactone products underwent various ring opening reactions to provide very useful derivatives, such as 1,3-diketones and enol esters, with good diastereoselectivity. 2.12 Annulations through domino aza-MBH/Michael reactions Because

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• . Nucleophilic ring opening reactions were performed on the crude cyclic sulfate mixtures because avoiding column chromatography at this stage led to a vast improvement in the overall yields. After ring opening, sulfate ester cleavage was achieved by stirring the concentrated residue in acid (20% H2SO4) and

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• led to a total decomposition – most probably due to ring-opening reactions with bromosilanes [37]. Further, we investigated the influence of the amount of bromine on the reaction and concluded that stoichiometric quantities entirely fulfill the demands of the bromination (Table 1, entries 7 and 8

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• Eietsu Hasegawa Minami Tateyama Ryosuke Nagumo Eiji Tayama Hajime Iwamoto Department of Chemistry, Faculty of Science, Niigata University, Ikarashi-2 8050, Niigata 950-2181, Japan 10.3762/bjoc.9.156 Abstract Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol

• (II)-salt-promoted oxidative ring-opening reactions of selected bicyclic cyclopropanol derivatives. Results and Discussion In the initial phase of this effort, we examined the reaction of cyclopropyl silyl ether 1a (0.40 mmol) with copper(II) acetate, Cu(OAc)2 , (1.1 equiv) for 1 h at room temperature

• previous observation that ether is a better solvent than MeCN and DMF in Cu(BF4)2-promoted ring-opening reactions of cyclopropylsilyl ethers [39]. When CH2Cl2 is employed as solvent, formation of 2 becomes more efficient while the yield of 3 remains moderate (Table 1, entry 7). Although the effect of the