Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• experiments, a plausible double selenation mechanism is shown in Scheme 2 and Scheme 3. The first step of the reaction involves the generation of the intermediate B via A by the Cu-mediated electrophilic substitution of 1 with selenium. The oxidative homocoupling of the intermediate B then proceeds to give

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• the product isolation procedure. In addition, it is well-established that the presence of Cu(I) salt can promote the in situ formation of some Cu(I) acetylides, which can readily undergo oxidative homocoupling of alkynes even in their slight excess in the reaction mixture [15][38][39]. Thus, the

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

• high level of functional group compatibility, intramolecular alkylations, inter and intramolecular C–H bond activation and regio/stereoselective homocoupling of alkynes [71][72][73]. Group of Cho and Chang have unprecedentedly reported a Rh catalytic system for facile addition of heteroarenes to both

• this methodology resulted in homocoupling of bromoalkynes. Among the examined Cu(I) and Cu(II) salts, Cu(OTf)2 was proven to be the optimal one. Both EW and EDGs were well tolerated except 2-amino-6-methylpyridine which might be sterically hindered due to methyl group at 6-position. The use of

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• minor amount of homometathesis. Fortunately, the product of homocoupling could be easily separated from the desired CM products. The presence of the carborane clusters was shown to enhance the thermal stability of the materials. Absorption and emission data of carborane–POSS hybrids indicate a large red

Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

• Miriam Schehr,
• Daniel Hugenbusch,
• Tobias Moje,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2018, 14, 2799–2804, doi:10.3762/bjoc.14.257

• challenging because most synthetic approaches involve homocoupling steps for the synthesis of the bridge as well as for the formation of the azo function [9][10][11][12][13][14][15][16]. In Table 1 previous synthesis approaches are compared to the synthesis approach in the present study. Recently, we reported

Synthesis of a tyrosinase inhibitor by consecutive ethenolysis and cross-metathesis of crude cashew nutshell liquid

• Jacqueline Pollini,
• Valentina Bragoni and
• Lukas J. Gooßen

Beilstein J. Org. Chem. 2018, 14, 2737–2744, doi:10.3762/bjoc.14.252

• % (Table 1, entry 2). The yield was further improved by raising the reaction temperature to 60 °C (Table 1, entry 3). Now, only 3% starting material 2 was detected, but unwanted homocoupling of 2 (product 6, see Supporting Information File 1) became a major side reaction. We tested several solvents

• an excess of 7 equivalents was optimal. With a smaller amount the yield was decreased (Table 1, entry 9 and 10), while a higher excess leads to decreased conversion. This can be explained by the undesired homocoupling of 1-hexene as a side reaction, which delivers the less active 5-decene (7, see

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• activation. In 1941, Kharasch and Fields applied a cobalt salt as the catalyst for the homocoupling of Grignard reagents [28]. After 15 years, Murahashi discovered a cobalt-catalyzed chelation-assisted ortho C–H carbonylation of azobenzene and imines as the preliminary example of directing group assisted C–H

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• drugs. The Yadav research group have also published the homocoupling of primary thioamides for the formation of symmetrical 1,2,4-thiadiazoles, using visible light and Eosin Y as the photocatalyst, in air at room temperature (Scheme 19) [64]. The immediately obvious limitation of this reaction is the

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• , stirring the reaction mixture beyond 4 hours did not lead to improved yields. Investigation on the loading of the catalyst indicated that 1 mol % was sufficient to drive the reaction to near completion (93% yield, Table 2, entry 9) considering the minor byproduct formed via homocoupling of the

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• ) or w (weak). NMR spectra were recorded on a Bruker AM 500 instrument operating at 500 or 125 MHz for 1H and 13C nuclei, respectively. All chemical shifts (δ values) are given in parts per million (ppm); all homocoupling patterns (nJH,H values) are given in Hertz. In the NMR descriptions, some

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

• Gernot A. Eller,
• Gytė Vilkauskaitė,
• Algirdas Šačkus,
• Vytas Martynaitis,
• Ashenafi Damtew Mamuye,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

• of unidentified products resulted (Scheme 4). In contrast, with aldehyde 6 a reaction product could be isolated in moderate yield, which can be assigned to structure 7 considering NMR data and mass spectra (Scheme 4). The dehydrogenative homocoupling of 2-pyrazolin-5-ones (or pyrazolidin-5-ones) is

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Keshaba N. Parida,
• Gulab K. Pathe,
• Shimon Maksymenko and
• Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

• intramolecular fashion has the double advantage of avoiding homocoupling as well as helping to overcome low reactivity in hindered systems such as cyclohexanone [12]. To the best of our knowledge there are only five examples of successful intermolecular couplings of dissimilar enolates. Two of these examples

• competing side reaction was the nucleophilic attack by the tosylate on the enolonium species 4. Only in the rare cases mentioned below homocoupling did take place. The enolonium species 4 (R1 = Ph, R2 = H) reacts readily with both electron-rich and electron-poor TMS enol ethers 5 (Scheme 2). Thus, the cross

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• reagent in the reaction, the substrate 1a was converted to 4a in 27% yield (conditions a), while the dehalogenation was exacerbated in the presence of Pd(OAc)2/PPh3 (conditions b). This phenomenon was in agreement with previous reports [14][15][16], that Pd-catalyzed homocoupling of aryl halides under

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• oxide Ce0.99Pd0.01O2–δ showed to be least efficient for the explored Suzuki–Miyaura couplings. Regarding the selectivity of the catalysts in the selected cross-coupling reactions, no bromoarene-deriving side products (dehalogenation product Ar’ and bromoarene homocoupling product Ar’Ar’) could be

• detected. However, both boronic acid homocoupling (ArAr) and boronic acid oxidation (ArOH) occurred to a small extent as indicated by HPLC. As the side product formation mainly occurs when the bromoarene coupling partner gets depleted, highest reaction selectivity (up to 99.5% [37]) can be achieved by

Intramolecular glycosylation

• Xiao G. Jia and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

• ). With primary glycosyl acceptors, such as 66 (Scheme 16), yields were slightly diminished due to the formation of the homocoupling products. Secondary alcohol acceptors were even less efficient showing a high substrate specificity of this approach. Other donor series including 2-azido and 2-deoxy sugars

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

• Josef Jansa,
• Ramona Schmidt,
• Ashenafi Damtew Mamuye,
• Laura Castoldi,
• Alexander Roller,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90

• the main product, but also containing biphenyl, traces of the desired product 6a, the homocoupling dimer 7a as well as a compound 8, obviously resulting from attack of PhLi to the pyridine system attached to pyrazole N-1 (Scheme 4). Negishi cross-couplings with 4-iodopyrazoles 3a–d The Negishi cross

• homocoupling products 7a,b emerged as the predominant reaction products (Scheme 5, middle trace), probably due to preferable halogen–zinc exchange and subsequent homocoupling. Interestingly, such sterically hindered halides provided homocoupling products 7a,b in good yields (66% and 48%, respectively). The

• selectivity towards these compounds increased with the excess of phenylzinc halide. In a model reaction employing 3b and 2 equivalents of PhZnBr, a mixture of 7b (48%), the desired coupling product 6b (27%) and dehalogenation product 2b (25%) was isolated. Such homocoupling and dehalogenation processes have

Direct arylation catalysis with chloro[8-(dimesitylboryl)quinoline-κN]copper(I)

• Sem Raj Tamang and
• James D. Hoefelmeyer

Beilstein J. Org. Chem. 2016, 12, 2757–2762, doi:10.3762/bjoc.12.272

• the absence of catalyst, using 3 or 30 equivalents KO(t-Bu) gave no reaction (Table 1, entries 5 and 6). While the high yield of the direct arylation suggests that the product cannot be exclusively obtained from homocoupling of iodobenzene, we performed additional experiments to demonstrate a

Correction: Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 2124–2124, doi:10.3762/bjoc.12.201

• homocoupling of benzaldehyde at a low loading (4 mol %) to afford benzoin in 90% yield and >99% ee (Scheme 6) [19]” should be read as “Zeitler and Connon reported that it promotes homocoupling of benzaldehyde at a low loading (4 mol %) to afford benzoin in 90% yield and >99% ee (Scheme 6) [19].” The oversight

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

• % yield. When the reaction was conducted under oxygen atmosphere, the yield of 11a fell to 46%. Under these aerobic conditions, we isolated biphenyl (13) generated through homocoupling of phenylboronic acid. Attempts to improve the yield by the use of bases such as Na2CO3 (10 mol %) and K2CO3 (10 mol

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• benzoin condensations [18]. The pentafluorophenyltriazolium catalyst 15 featured in the most efficient asymmetric benzoin reaction reported so far. Inoue and co-workers found that it promotes homocoupling of benzaldehyde at a low loading (4 mol %) to afford benzoin in 90% yield and >99% ee (Scheme 6) [19

Hydroquinone–pyrrole dyads with varied linkers

• Hao Huang,
• Christoffer Karlsson,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 89–96, doi:10.3762/bjoc.12.10

• 3-bromo-1-(triisopropylsilyl)-1H-pyrrole resulted in low yield (20%) and also homocoupling. Considering that desilylation of triisopropylsilyl protected pyrrole might occur at high temperature in DMF, an overnight reaction at room temperature was performed, resulting in a yield for 4d of 50%. In

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

• reaction did not afford 3aa at all (Table 1, entry 2), PyC promoted the reaction with higher yield of 4-arylisoxazole 3aa under these conditions (30%, Table 1, entry 3). In the AuCl(PyC)-catalyzed reaction, 1a was fully consumed, and 4,4’-dibromobiphenyl (4a) derived from the homocoupling of arylsilane 2a

• electrophilic metalation of heteroarene 1 with C with concurrent generation of an acid (HX) produces diarylated gold(III) species D. Finally, the reductive elimination from D releases the coupling product 3 along with the regeneration of gold(I) species A. The side reaction leading to the homocoupling product

Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans

• Emeline Rideau and
• Stephen P. Fletcher

Beilstein J. Org. Chem. 2015, 11, 2435–2443, doi:10.3762/bjoc.11.264

• but low product yields. Presumably 11 arises from the homocoupling of allyl chloride 2a, possibly through a π-allyl-Cu intermediate [39][40][41][42][43]. Although both the conditions and leaving groups differ in the two reactions it is not clear why 2a, but not 2d, dimerizes. 11 can exists as 3

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• homocoupling [15][16]. In this contribution we report the results obtained from a kinetic study carried out with the IPrAuCl complex that allows proposing a plausible inner-sphere mechanism in which the substrate (styrene or methanol) seems to remain coordinated to the gold center, a feature that could be

Efficient synthesis of π-conjugated molecules incorporating fluorinated phenylene units through palladium-catalyzed iterative C(sp²)–H bond arylations

• Fatiha Abdelmalek,
• Fazia Derridj,
• Safia Djebbar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2015, 11, 2012–2020, doi:10.3762/bjoc.11.218

• . We were pleased to find that only one regioisomer was formed, as the arylation exclusively occurred at the C–H bond between fluorine and chlorine atoms. The desired (hetero)aryl triad 31 was isolated in moderate yield, due to the formation of a relatively large amount of homocoupling product of the