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

• transition metal catalyst Cu(OTf)2, Wu and co-workers achieved aerobic oxidative coupling of secondary amines with β-keto esters to form C(sp3)–C(sp3) bonds (Scheme 1) [18]. Although much advance has been made for the functionalization of glycine derivatives, most of these strategies mentioned above require

• catalyst, the yield of 3aa increased to 81% (Table 1, entries 16–19). On the basis of the screening of reaction conditions, we could conclude that the electrocatalytic oxidative coupling should be performed in a mixed solution of CH3CN and CH2Cl2 (v/v = 1:2), in the presence of n-Bu4NI (30 mol %) as the

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• , Lebanon Université de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226, Avenue du Général Leclerc, 35042 Rennes Cedex, France 10.3762/bjoc.13.208 Abstract Using an aerobic oxidative coupling, different new imidazo[1,2-a]-N-heterocycles with gem-difluroroalkyl side chains have been

• coupling reactions as well as nucleophilic substitutions have been performed successfully in order to increase the molecular diversity. Keywords: aerobic oxidative coupling; imidazo[1,2-a]-N-heterocycles; gem-difluoroalkyl derivatives; propargylic fluorides; Introduction Nitrogen-containing heterocyclic

• (II) acetate-catalyzed aerobic oxidative amination and it proceeds through a tandem Michael addition followed by an intramolecular oxidative amination. Therefore, our target molecules A could be synthesized by the oxidative coupling of 2-aminopyridines with α,β-unsaturated ketones B, themselves easily

Transition-metal-free synthesis of 3-sulfenylated chromones via KIO₃-catalyzed radical C(sp²)–H sulfenylation

• Yanhui Guo,
• Shanshan Zhong,
• Li Wei and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2017, 13, 2017–2022, doi:10.3762/bjoc.13.199

• transition-metal-free oxidative coupling has emerged as a powerful complementary tactic in C(sp2)–S bond forming reactions [16][17][18][19][20][21][22][23][24][25][26][27]. As a beneficial and sustainable approach, such transition-metal-free cross coupling transformations have been successfully employed in

Synthesis of oligonucleotides on a soluble support

• Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

• oligonucleotides and most of these attempts have concerned the preparation of phosphorothioate ODNs, as discussed below. The only successful synthesis of unmodified ODNs was based on oxidative coupling of alkyl H-phosphonates on a PEG support [65]. The 3´-terminal nucleoside was immobilized to a PEG support via a

α-Acetoxyarone synthesis via iodine-catalyzed and tert-butyl hydroperoxide-mediateded self-intermolecular oxidative coupling of aryl ketones

• Liquan Tan,
• Cui Chen and
• Weibing Liu

Beilstein J. Org. Chem. 2017, 13, 1079–1084, doi:10.3762/bjoc.13.107

• self-intermolecular oxidative coupling of aryl ketones using I2−tert-butyl hydroperoxide (TBHP). Under the optimum conditions, various aryl ketones gave the corresponding products in moderate to excellent yields. A series of control experiments were performed; the results suggest the involvement of

• H2O in the TBHP solvent. Keywords: aryl ketones; iodine; self-intermolecular oxidative coupling; self-sequential assembly; TBHP; Introduction In recent years, α-acetoxyaryl ketones have attracted considerable interest because this structural motif is found in a variety of biologically active natural

• transition-metal-catalyzed direct oxidative coupling reactions of carbonyl compounds with carboxylic acids (or their surrogates) [8][9]. Recently, robust approaches using organohypervalent iodine reagents and peroxide-mediated oxidative coupling have been developed [10][11]. Although impressive progress has

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• reported a metal-free photocatalytic aerobic oxidation of thiols to disulfides under continuous-flow conditions [64]. Disulfides are useful molecules employed as drugs, anti-oxidants or pesticides as well as rubber vulcanizating agents [65]. Symmetric disulfides are generally obtained by oxidative coupling

A versatile route to polythiophenes with functional pendant groups using alkyne chemistry

• Xiao Huang,
• Li Yang,
• Rikard Emanuelsson,
• Jonas Bergquist,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 2682–2688, doi:10.3762/bjoc.12.265

• quinone moieties are vulnerable in nucleophilic and acidic environments. Furthermore, the viologen moiety, available from 4,4’-bipyridine (BP) has potential for energy storage and electrochromic applications [35][36], but it has previously been anchored to a polymer backbone only by oxidative coupling via

TBHP-mediated highly efficient dehydrogenative cross-oxidative coupling of methylarenes with acetanilides

• Cui Chen,
• Weibing Liu and
• Peng Zhou

Beilstein J. Org. Chem. 2016, 12, 2250–2255, doi:10.3762/bjoc.12.217

• Cui Chen Weibing Liu Peng Zhou College of Chemical Engineering, Guangdong University of Petrochemical Technology, 2 Guandu Road, Maoming 525000, P. R. China. Fax: +86-668-2923575; Tel: +86-668-2923444 10.3762/bjoc.12.217 Abstract A TBHP-mediated dehydrogenative cross-oxidative-coupling approach

• C–N bonds. Besides, this conversion is an important complement to the conventional C–N forming strategies. Keywords: dehydrogenative cross oxidative coupling; methyl arenes; N-arylbenzamides; TBHP; Introduction Recently, amides have attracted more and more attention due to their extensive

• ketoximes [13], the C–N cross coupling between aromatic amides or amines and aryl(pseudo)halides [14][15] or aldehydes [16][17][18][19][20]. However, to the best of our knowledge, the studies of dehydrogenative cross-oxidative-coupling reactions between methylarenes and amines for the formation of amides

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• ][109][110][111][112][113]. Organic peroxides are widely used as oxidants in oxidative coupling processes [114][115][116][117][118][119][120]. Industrial-scale production of readily available and efficient initiators of free radical polymerization and effective biologically active compounds promotes the

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• oxidative coupling of acetylacetone 1a employing iodosylbenzene in the presence of boron trifluoride in methanol [41] followed by the standard amination procedure indeed furnished β-enaminoketone 2i in moderate yield (Scheme 3). This intermediate could be N-acylated via its potassium salt with activated

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• oxidative coupling of two C–H bonds [also termed as cross-dehydrogenative-coupling (CDC)] in the formation of C–C bonds [11][12][13][14][15][16]. This was facilitated by the introduction of transition metals in organic synthesis providing an amazing tool to explore these oxidative coupling reactions in an

• to the phenyl ring. The α-carbonylalkyl radicals were formed by Cu(II)-mediated oxidation of the respective enolate precursors. In 2010, Yu and co-workers have reported the synthesis of 3-acetyloxindoles via Ag2O-mediated intramolecular oxidative coupling [45]. For the past few years, our group is

• article, we disclose the scope and limitations of 'transition-metal-free' IDC of Csp2-H and Csp3-H using iodine and N-iodosuccinimide (NIS) as oxidants. In addition, we have also demonstrated the synthetic utility of oxidative coupling products in the syntheses of 3-substituted-2-oxindoles, via a

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• ] and PCy3 formed the ruthenium(0) complex, which then mediated the oxidative coupling of N-benzyl-protected isatin and styrene to form oxametallacycle I. The ruthenium alkoxide III was formed through two possible pathways: (a) the direct transfer hydrogenolytic cleavage of I (slow); (b) the

• oxidative coupling sequence (Scheme 48). Similarly, the tricyclic N-heterocyclic core in natural (+)-asperazine and idiospermuline was also efficiently synthesized in 71% overall yield. The oxindole was reduced to the lactol by NaBH4, which was then subjected to a camphorsulfonic acid (CSA)-promoted

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• processes Asymmetric oxidative coupling All carbon quaternary centers are prevalent in both natural and pharmaceutical compounds, but rank amongst the hardest to synthesize in a stereoselective manner. Dixon and co-workers have addressed this through the development of an asymmetric organocatalytic

• oxidative coupling – initially between 3-methoxycatechol (100) and tert-butyl 1-oxoindan-2-carboxylate (101) using an adamantane derivative of cupreidine CPD-102 to give the corresponding adduct 103 in 84% yield and 81% ee (Scheme 24a) [69]. An attempt to develop this methodology towards an asymmetric total

• ) Dixon’s 6’-OH cinchona alkaloid catalyzed oxidative coupling. (b) An asymmetric oxidative coupling en route to the attempted total synthesis of some amaryllidaceae alkaloids. Acknowledgements The University of Reading (to RF) and GW Pharmaceuticals, along with the BBSRC (BB/L015714/1 to LAB) are

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• represented by oxidative coupling that is expected to proceed through a gold(I)/gold(III) catalytic cycle [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]. In particular, the

• column chromatography on silica gel. Thus we envisioned that a gold complex with strongly electron-donating PyC would promote the gold(I)-to-gold(III) oxidation process, facilitating oxidative coupling reactions. Herein we report that the PyC ligand facilitates gold-catalyzed oxidative C–H arylation of

• the gold(I)-to-gold(III) oxidation and stabilizes the gold(III) species, thereby facilitating the oxidative coupling reactions. Experimental Preparation of triarylpyridylidene-gold(I) chloride [AuCl(PyC)]: A 10 mL Schlenk tube containing a stir bar was dried under vacuum and filled with N2 after

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

• the CuAAC reaction, the 5,5'-bitriazoles were usually considered as an undesired side product or impurity in the Huisgen cycloaddition. In general, they are the oxidative coupling product of the triazole-copper species. The 5,5'-bitriazoles were usually formed as the major product by the facilitation

• of the reaction conditions or controlled by the starting substrate. In 2007, Burgess and Angell successfully developed an oxidative coupling method for the preparation of 5,5’-bitriazole [21]. In this work, they were able to perform this reaction of azides and terminal alkynes with moderate to high

• acetonitrile to perform the reaction, the sequential, CuAAC oxidative coupling gave the cyclic 5,5’-bitriazoles 14 as the major product (44–74%). They demonstrated that both the reaction conditions and the conformational effect are beneficial for the formation of the 5,5'-bitriazoles. Similarly, Urbano and co

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

• agent. For instance, it has been previously shown that the alkynes could favor the Cu(II) to Cu(I) reduction, most probably through the well-known Glaser-type oxidative coupling [30][31]. We thus tested the reduction in the presence of the water-soluble alkynes 5–7. In marked contrast with experiments

• generation of copper(I) through Glaser-type oxidative coupling. The catalytic system was found to be very sensitive to light. By simply leaving the tube exposed to ambient laboratory light after degassing, 70% conversion was reached in 4 h, the full conversion being attained in 7 h. Interestingly, from a

• , ≈35% of 1 being reduced after 250 s of irradiation. It is important to note that no reduction was observed in the absence of light, showing that the reduction is a photoinduced process. It also shows that if light-independent reduction is occurring, most probably through a Glaser-type oxidative

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• ), sonic hedgehog (Shh) and Notch. The results suggested that ellagic acid effectively inhibited human pancreatic cancer growth by suppressing the Akt, Shh and Notch pathways. The preparation of ellagic acid (7) can be achieved by the oxidative coupling of gallic acid (Scheme 3) [33]. In the presence of

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

• Taiki Kojima,
• Rika Obata,
• Tsuyoshi Saito,
• Yasuaki Einaga and
• Shigeru Nishiyama

Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21

• investigations. Several synthetic approaches, including electrochemical oxidative coupling reactions mimicking biosynthetic pathways, were reported to construct the backbones of these molecules [5]. Recently, boron-doped diamond (BDD) electrodes have attracted a great deal of attention for their wide potential

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

• as the second stage in a two-step cross-dehydrogenative C–O coupling. The formation of a new C–O bond generally takes place with the involvement of an O-nucleophile, an O-radical, or an O-electrophile. In the oxidative coupling with O-reagents as nucleophiles, electrophilic intermediates that are

• equivalent amount of alcohol. 2.2 Oxidative systems based on noble metals and oxygen The oxidative coupling of benzyl alcohols with aliphatic alcohols in the presence of Pd(II) salt/Ag(I) salt/base/oxygen system was proposed [96][97]. In the study [97], phosphine ligands were additionally employed. It is

• suggested that the coupling occurs through oxidation of benzyl alcohol to benzaldehyde. Alcohols (OH-reagents) are taken in a twofold molar excess [96] or are used as solvents [96][97]; the reaction time is 20–40 h at 45–80 °C. The aerobic oxidative coupling of aldehydes or primary alcohols as CH-reagents

Trogopterins A–C: Three new neolignans from feces of Trogopterus xanthipes

• Soyoon Baek,
• Xuikui Xia,
• Byung Sun Min,
• Chanil Park and
• Sang Hee Shim

Beilstein J. Org. Chem. 2014, 10, 2955–2962, doi:10.3762/bjoc.10.313

• findings (Table 1 and Table 2), compound 1 was hypothesized to have a lignan skeleton formed through oxidative coupling of two phenylpropanoids units. This compound was also presumed to have three rings in its structure based on the unsaturation degree since it contained two aromatic moieties and an ester

Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light “on water”

• Julio Benites,
• Juan Meléndez,
• Cynthia Estela,
• David Ríos,
• Luis Espinoza,
• Iván Brito and
• Jaime A. Valderrama

Beilstein J. Org. Chem. 2014, 10, 2448–2452, doi:10.3762/bjoc.10.255

• conventional oxidative phenylamination procedures, this novel synthetic method offers the advantage of aerobic conditions “on water” instead of hazardous oxidant reagents currently employed in aqueous alcoholic media. Keywords: 1,4-naphthoquinone monoimines; on water; oxidative coupling; rose bengal; solar

• green route for the preparation of N-phenyl-1,4-naphthoquinone monoimines by on-water oxidative coupling reaction of 1-hydroxynaphthalene derivatives with oxygen-substituted phenylamines under solar light or green LEDs radiation, rose bengal as singlet oxygen sensitizer and aerobic conditions. Results

• histidine, compound 6 was obtained in 69 and 62% yield, respectively. By comparing these results to that observed in the absence of histidine, it may be suggested that singlet oxygen is involved in the oxidative coupling reaction to produce compound 6. In addition, experiments on the oxidative coupling

Oligomerization of optically active N-(4-hydroxyphenyl)mandelamide in the presence of β-cyclodextrin and the minor role of chirality

• Helmut Ritter,
• Antonia Stöhr and
• Philippe Favresse

Beilstein J. Org. Chem. 2014, 10, 2361–2366, doi:10.3762/bjoc.10.246

• ; enzyme; oxidative coupling; phenol oligomer; Introduction Lignin consists of mechanical stabilizing polyphenols and thus plays an important role in many plants [1][2]. For the in vitro synthesis of polyphenols via oxidative coupling reactions, laccases and peroxidases are suitable enzymes to catalyze

• the oligomerization of substituted electron-rich phenols in the presence of oxidizing agents [3][4]. In addition to that, N,N'-bis(salicylidene)ethylenediamine-iron(II) (iron(II)-salen) represents an alternative catalyst for oxidative coupling reactions of phenol derivatives [5]. The use of β

• -cyclodextrin (CD) allows the oxidative coupling of poor water soluble phenol derivatives via complexation without using of organic solvents [6][7][8]. However, to the best of our knowledge, there were no studies published dealing with the potential enantioselective control of enzyme catalyzed oligomerization

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• configuration is known [1][2] and their separation was accomplished recently [3][4][5]. Both silybin isomers as well as other flavonolignans from silymarin (crude defatted extract from the fruits of S. marianum) are products of a phenolic oxidative coupling of the flavonoid taxifolin and the lignan coniferyl

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• -dioxanes Modern approaches to the synthesis of 1,2-dioxanes are based on reactions with singlet oxygen, the oxidative coupling of carbonyl compounds and alkenes in the presence of manganese and cerium salts, the co-oxidation of alkenes and thiols with oxygen, the Isayama–Mukaiyama peroxidation, the

• -dioxan-3-ol (202) and 6-(prop-1-en-2-yl)-1,2-dioxane-3-imine (204), containing the hydroxy and imine groups, respectively (Scheme 56) [304]. 3.2. Oxidative coupling of carbonyl compounds and alkenes in the presence of manganese or cerium salts The synthesis of 1,2-dioxanes 207 is based on the addition of