Cationic cobalt-catalyzed [1,3]-rearrangement of N-alkoxycarbonyloxyanilines

• Itaru Nakamura,
• Mao Owada,
• Takeru Jo and
• Masahiro Terada

Beilstein J. Org. Chem. 2018, 14, 1972–1979, doi:10.3762/bjoc.14.172

• discussed in our preliminary communication. Results and Discussion At the beginning of this investigation, N,O-di(methoxycarbonyl)hydroxylaniline (1a) was treated with catalytic amounts of several copper salts in 1,2-dichloroethane (DCE) at 60 °C (Table 1, entries 1–7), according to our previous copper

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

• -introduced into the catalytic cycle. Several copper salts (CuCl, CuCl2, CuOAc and Cu(OAc)2) were evaluated as part of optimizing the reaction conditions and they all provided poor yields. 3.3.3 Acetoxysulfenylation of Baylis–Hillman alcohols. Yadav and Aswathi reported a regioselective CuI-imidazole

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• copper salts was found. In an attempt to expedite the LAG reaction, millimol-scale reactions between the p-azobenzene-appended alkyne and 5′-azido-5′-deoxythymidine were attempted in a more capacious copper vessel with a 15 mm diameter zirconia ball (Figure 3). Clean and complete click reactions were

Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• ., wherein simple copper salts were used as catalysts and oxygen as the co-oxidant (Scheme 1) [17]. Alternatively, photocatalytic versions of CDC reactions of glycine derivatives with C-nucleophiles were also developed [18][19]. For example, combining the visible light catalyst Ru(bpy)3Cl2, and the

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

• Elisandra Scapin,
• Paulo R. S. Salbego,
• Caroline R. Bender,
• Alexandre R. Meyer,
• Anderson B. Pagliari,
• Tainára Orlando,
• Geórgia C. Zimmer,
• Clarissa P. Frizzo,
• Helio G. Bonacorso,
• Nilo Zanatta and
• Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 2396–2407, doi:10.3762/bjoc.13.237

• reactions were planned between phenylacetylene and compounds 6a–c. The 1,2,3-triazole synthesis from the 1,3-dipolar cycloaddition reaction between 6a–c and terminal alkynes catalyzed by copper salts (CuAAC) [41][42][43] confirms that the reaction passes through an azide intermediate. In addition to mild

• reaction conditions and short reaction times, the advantage of CuAAC is the formation of 1,2,3-triazoles-1,4-disubstituted in a highly regioselective manner [41]. Recently, Cornec et al. [44] synthesized 4,6-dimethyl-2-(4-aryl-1H-1,2,3-triazol-1-yl)pyrimidines from azides using copper salts. The reaction

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• intermediate R´ which undergoes aromatization to provide the desired 86 (Scheme 31). Yamamoto et al. demonstrated a mild oxidative dehydrogenation of dihydropyrimidinones 88 and dihydropyrimidines 89 via catalytic copper salts and K2CO3 as base along with TBHP as the terminal oxidant (Scheme 32). The desired

Copper-catalyzed asymmetric sp³ C–H arylation of tetrahydroisoquinoline mediated by a visible light photoredox catalyst

• Pierre Querard,
• Inna Perepichka,
• Eli Zysman-Colman and
• Chao-Jun Li

Beilstein J. Org. Chem. 2016, 12, 2636–2643, doi:10.3762/bjoc.12.260

• -catalyst in DME as solvent, we observed a trace amount of the desired product at room temperature. When different copper salts were evaluated, it was found that CuBr was less active (Table 1, entry 1) and copper(II) bromide provided the highest yield for the arylation of THIQ with phenylboronic acid (2

• , Table 1, entry 2). Other copper salts such as Cu(OTf)2 and Cu(OAc)2 were much less effective (Table 1, entries 3 and 4). A significant increase of yield was observed when the stoichiometry of the system was changed to a slight excess of arylboronic acid. When more than 1.6 equivalents of 2 were involved

• for the direct asymmetric arylation of N-arylated tetrahydroisoquinolines (THIQs) with arylboronic acids. Using [Ir(ppy)2(dtbbpy)]PF6 as photoredox catalyst provided a novel facile method to build important arylated compounds in very high yields under very mild conditions. The combination of copper

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• one-pot reaction of 2-bromobenzaldehydes 169, alkynes 170, amines 171, and diethyl phosphonate under multicatalytic conditions including palladium and copper salts (Scheme 37) [75]. This process presumably involves a sequential Sonogashira coupling/cyclization-nucleophilic addition reaction, which is

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• were examined, such as Pd(OAc)2, PdCl2Ln, Pd2(dba)3, in the absence of added acid, but none led to cross-coupling at room temperature. 1,4-Benzoquinone (BQ) was found to be an effective additive in promoting the reaction, while addition of stoichiometric metal salts (e.g., silver or copper salts) was

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• stereogenic center with full retention of the asymmetric carbon configuration (Scheme 2) [33]. The authors demonstrated that an insertion reaction in C(sp3)–H bonds only occurs with considerable yield when small amounts of copper powder or copper salts, such as CuSO4 and CuCN, were employed. Even using the

Copper-mediated arylation with arylboronic acids: Facile and modular synthesis of triarylmethanes

• H. Surya Prakash Rao and
• A. Veera Bhadra Rao

Beilstein J. Org. Chem. 2016, 12, 496–504, doi:10.3762/bjoc.12.49

• of triphenylmethane (11a). Next, we turned our attention to evaluate different copper salts to optimize the yield of triphenylmethane (11a); these efforts have been summarized in Table 1. We screened various Cu(II) catalysts such as Cu(OAc)2 (64%, Table 1, entry 1), Cu(CF3COO)2 (46%, Table 1, entry 2

Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

• Brett N. Hemric and
• Qiu Wang

Beilstein J. Org. Chem. 2016, 12, 22–28, doi:10.3762/bjoc.12.4

• regioselectivity, as 4a was not observed in the absence of a catalyst (Table 1, entry 1). Among a variety of copper salts (Table 1, entries 2–7), Cu(OAc)2 proved superior as a catalyst (Table 1, entry 2). When the stoichiometry of each reactant was examined for this three-component transformation, decreasing the

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

• Yan Li,
• Xue Zhou,
• Guangfan Zheng and
• Qian Zhang

Beilstein J. Org. Chem. 2015, 11, 2721–2726, doi:10.3762/bjoc.11.293

• atmosphere at 70 °C for 10.0 h, the desired aminooxygenation product 3a was obtained in 39% yield (Table 1, entry 1). A variety of copper salts such as CuCl, CuBr, CuI, [(CH3CN)4Cu]PF6, CuCN, Cu(acac)2, Cu(OAc)2, CuBr2 and CuCl2 were examined (Table 1, entries 2–10). We found that CuCl2 was the most

• effective catalyst, affording 3a in 55% yield (Table 1, entry 10). No reaction was observed in the absence of copper salts (Table 1, entry 11). Next, the reaction solvents were scanned. 1,2-Dichloroethane (DCE) and CH3CN were not efficient solvents, providing 3a in 9% and 20% yields, respectively (Table 1

Recent advances in copper-catalyzed asymmetric coupling reactions

• Fengtao Zhou and
• Qian Cai

Beilstein J. Org. Chem. 2015, 11, 2600–2615, doi:10.3762/bjoc.11.280

• requirement of stoichiometric amounts of copper and harsh reaction conditions (high temperatures). The turn of the millennium brought about the revival of the research in this field that was initiated by the use of soluble copper salts and ligand-coordinated Cu complexes as catalysts. This allowed the

• chelating ligands and thus compete with the chiral ligand for binding with the copper salts. Therefore the authors used a mono-aryl halide-substituted malonamide in the presence of a chiral CuI/1,2-diamine catalyst system and obtained the desired products in good yields and moderate enantioselectivities [48

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• chemistry using the catalysis of various copper salts that generate Cu(I) sources in situ [16]. As a brief summary, the copper(I)-promoted click chemistry has the following features: (1) The most preferred methods for the formation of Cu(I) involve the use of CuSO4 and a reducing agent in an aqueous

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• believed to follow a nitroso–ene mechanism. Similar reactions have been reported using copper salts and N-phenylhydroxylamine [39] or N-Boc-hydroxylamine [40][41], presumably via oxidation of the hydroxylamine to a nitroso species which then undergoes the nitroso–ene reaction. Stemming from our interest in

A concise and efficient synthesis of benzimidazo[1,2-c]quinazolines through CuI-catalyzed intramolecular N-arylations

• Xinlong Pang,
• Chao Chen,
• Ming Li and
• Chanjuan Xi

Beilstein J. Org. Chem. 2015, 11, 2365–2369, doi:10.3762/bjoc.11.258

• even at elevated temperatures (Table 1, entries 5–9). Other copper salts such as Cu(OTf)2, CuBr or CuCl were also able to catalyze the reaction, but they were not as efficient as CuI as the catalyst (Table 1, entries 5–9). It is worth mentioning that the imino group (sp2) other than the amino group

Molecular-oxygen-promoted Cu-catalyzed oxidative direct amidation of nonactivated carboxylic acids with azoles

• Wen Ding,
• Shaoyu Mai and
• Qiuling Song

Beilstein J. Org. Chem. 2015, 11, 2158–2165, doi:10.3762/bjoc.11.233

• copper salts demonstrated good activity for this novel transformation (Table 1, entries 1–5) and 85% of the desired product was obtained using 10 mol % of CuBr with pyridine (3 equiv) at 130 °C in p-xylene (1 mL) under O2 in a sealed tube (Table 1, entry 4). Notably, CuBr2 only gave 33% of the desired

Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes

• Artem A. Zemtsov,
• Alexander D. Volodin,
• Vitalij V. Levin,
• Marina I. Struchkova and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2015, 11, 2145–2149, doi:10.3762/bjoc.11.231

• (Table 1, entry 5). The addition of various ligands, as well as the use of other copper salts, did not had a beneficial effect. Under the optimized conditions, a series of organozinc compounds 2 were coupled with bromoalkynes 3 (Table 2). Good yields of coupling products 4 were typically achieved. The

Copper-mediated synthesis of N-alkenyl-α,β-unsaturated nitrones and their conversion to tri- and tetrasubstituted pyridines

• Dimitra Kontokosta,
• Daniel S. Mueller,
• Dong-Liang Mo,
• Wiktoria H. Pace,
• Rachel A. Simpson and
• Laura L. Anderson

Beilstein J. Org. Chem. 2015, 11, 2097–2104, doi:10.3762/bjoc.11.226

• observed and isolated. Decreasing the amount of copper reagent to 1 equiv had little influence on the reaction and a screen of other common copper salts only resulted in diminished yields (Table 1, entries 2–7). Further reduction of the copper loading to 10–30 mol % of Cu(OAc)2 was tolerated without a

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• copper salts, which should be avoided for in vivo applications and, when employed, by sodium ascorbate and/or its byproducts; (iii) side-reactions on the substrates due to the generation of reduced dioxygen-active species and/or reactive oxidized byproducts of ascorbate. In a seminal paper, Finn and

The facile construction of the phthalazin-1(2H)-one scaffold via copper-mediated C–H(sp²)/C–H(sp) coupling under mild conditions

• Wei Zhu,
• Bao Wang,
• Shengbin Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2015, 11, 1624–1631, doi:10.3762/bjoc.11.177

• of copper salts and N,N’-dual coordinated directing groups [18][19][20][21][22]. By the employment of a similar approach, our group reported a straightforward route to the isoquinolinone scaffold via copper-mediated C–H(sp2)/C–H(sp3) coupling [23]. In light of previous works, we envisioned the

• temperature (120 °C) with excessive copper salts (3 equivalents). In addition, failure to remove the directing group partly prevented the practicality and application of the transformation [22]. Herein, we reveal a copper-mediated direct C–H(sp2)-C–H(sp) bond construction and simultaneous annulations under

• milder conditions with less equivalents of copper salts and oxygen atmosphere at a lower temperature (80 °C). Even more important, the resulting products could be smoothly transformed into preconceived 4-benzylphthalazin-1(2H)-one derivatives with the removal of the directing group by treatment with

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

• ]. Importantly in this study, a flow reactor consisting of copper tubing maintained at 110 °C (6.2 minutes residence time) was employed as this would release small amounts of copper salts catalysing the regioselective triazole formation. A cautionary note regarding the potential of generating copper azide within

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• hydrolysates [5]. Conversion of amino acids to their copper salts elegantly masks both amino acid functionalities, thus protecting them during a subsequent alkaline acylation reaction that targets the side-chain functionality selectively. The side-chain-acylated lysine can then be liberated by decomposition of

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• works, the oxidative coupling of alcohols, aldehydes, or formamides with 1,3-dicarbonyl compounds or phenols was accomplished in the presence of tert-butyl hydroperoxide and copper salts (Table 5). In most cases, the range of phenols applicable to the coupling is limited to 2-acylphenols. However, 2