Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• , Figure 4b). Contrastingly, in solution the same synthesis took 4 h at 70 °C to isolate complex 9 in 56% yield. Ćurić and co-workers prepared cyclopalladated complexes such as 10 by a grinding method and were the first to confirm a mechanochemical C–H bond activation of an unsymmetrically substituted

• salen-type ligand followed by metal-complex formation in the same pot [55]. Otera’s solvent-free approach by which the formation of self-assembled supramolecules could be accelerated [56]. Synthesis of a Pd-based metalla-supramolecular assembly through mechanochemical activation for C–H-bond activation

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• Rh complex B (step a). Then, chelation-assisted C–H bond activation proceeds to generate a rhodacycle C (step b). The reaction of C with CO2 affords an eight-membered rhodacycle intermediate D (step c). Next, D is converted to the corresponding rhodium complex E by ligand exchange with KOAc (step d

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• oxidation forming aryl ketones [52]. Note that the successful coupling of a range of secondary and tertiary carboxylic acids now supports the direct and selective C–H bond activation at the benzyl position by avoiding the formation of carbonyloxy radicals, which are susceptible to decarboxylation. In

• known to readily abstract hydrogen atoms at the tertiary carbon centers [79], the results suggest a predominant participation of the iodanyl radical as the hydrogen atom abstractor for the selective secondary benzylic C–H bond activation in our reaction. It seems that the iodanyl radical is more

Palladium-catalyzed ortho-halogenations of acetanilides with N-halosuccinimides via direct sp² C–H bond activation in ball mills

• Zi Liu,
• Hui Xu and
• Guan-Wu Wang

Beilstein J. Org. Chem. 2018, 14, 430–435, doi:10.3762/bjoc.14.31

• ][24][25][26][27][28]. A few mechanochemical ortho-C–H bond activation reactions under the catalysis of rhodium and palladium salts have been reported [29][30][31][32][33][34][35][36][37][38]. Hernández and Bolm reported the rhodium-catalyzed bromination and iodination of 2-phenylpyridine using N

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

• Aymen Skhiri,
• Ridha Ben Salem,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2017, 13, 2862–2868, doi:10.3762/bjoc.13.278

• synthesis of unsymmetrical 2,5-di(hetero)arylated selenophene derivatives in three steps from selenophene. Keywords: C–H bond activation; catalysis; heteroarenes; palladium; selenophene; Introduction (Hetero)aryl-substituted selenophenes represent a class of molecules which exhibit useful physical

• recent years, the Pd-catalyzed arylation, via a C–H bond activation, of a broad range of heteroaromatics using aryl halides as reaction partners was demonstrated to be particularly effective for the preparation of bi(hetero)aryls [22][23][24][25][26][27][28][29][30][31]. Among the reported results, a few

• examples of Pd-catalyzed direct arylations via the C–H bond activation of selenophenes using aryl halides as coupling partners have been reported [32][33][34][35]. Conversely, C–H bond activation methodology was employed in only in one case for the preparation of a heteroarylated selenophene from a

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

• . Presently, the most popular approaches in constructing a C(sp2)–S bond are the transition-metal-catalyzed Ullmann C–S coupling reaction [4][5][6][7][8], Chan–Lam cross-coupling reaction [9][10][11][12] as well as the transition-metal-catalyzed C–H bond activation [13][14][15]. Recently, as a new trend, the

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• Aleksanyan and co-workers reported the first gram-scale synthesis of a PdII organometallic pincer complex under mechanomilling via C–H bond activation. After successful isolation of the PdII pincer complex by grinding of bis(thiocarbamate) and PdCl2(NCPh)2 they could scale up the reaction up to 1.76 mmol

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

• M. Fernanda N. N. Carvalho,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122

• all atoms of the starting material are found in the product, and thus fulfil an important requirement of “green chemistry” [31]. However, a different Pt(II)-catalysed reaction cascade was observed for 4c, with adamantyl groups at the alkynes. Here, the annulation step is followed by a C–H bond

• -activation process, to establish an additional bond to one of the adamantyl groups (8 in Scheme 3b) [32]. The simplest diyne 4d with R = H, in contrast, gave a ring enlargement from six to seven members together with a 1,2-oxygen shift instead (9 in Scheme 3c) [33]. This clearly demonstrates that the

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• removal of a beneficial functional group. The electron-withdrawing properties of the nitrile functional group appear beneficial in a variety of reactions [1][2]. This group coordinates metal complexes and can be used as a directing group for C–H bond activation reactions catalyzed by transition metals [3

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

• addition/reductive elimination. The scope of reactivity, including functional group tolerance on the reactants, types of C–H bonds that can be activated, selectivity of C–H bond activation, further optimization studies, and new catalyst design will be topics for further study. The initial results are very

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

• process despite the advances that have been made in this field [1]. The directing group strategies are widely used and developed to achieve enantioselective metal-catalyzed C–H bond functionalizations in recent years. Unactivated alkyl C–H bond activation (i.e., without any directing group) is of great

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• , including hydrolysis reactions [10][11][12][13][14][15], C–H bond activation [34][35][36], olefin epoxidation [37][38][39], Diels–Alder reactions [40][41][42], 1,3-dipole cycloadditions [43][44], and polymerizations [45][46][47], among others. Selective substrate recognition and activation are essential

Regiocontroled Pd-catalysed C5-arylation of 3-substituted thiophene derivatives using a bromo-substituent as blocking group

• Mariem Brahim,
• Hamed Ben Ammar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2016, 12, 2197–2203, doi:10.3762/bjoc.12.210

• “green” access to arylated thiophene derivatives as it reduces the number of steps to prepare these compounds and also the formation of wastes. Keywords: aryl bromides; C–H bond activation; catalysis; direct arylation; palladium; thiophenes; Introduction Thiophene derivatives bearing aryl substituents

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

• Although aromatic C–H bond activation through palladacycle [214] generation is a critical step in the ortho-directed, activation/cross-coupling sequence, many of its specific mechanistic features are still controversial. Previous studies with arylureas [73][206][215] have formulated a palladacycle as the

Opportunities and challenges for direct C–H functionalization of piperazines

• Zhishi Ye,
• Kristen E. Gettys and
• Mingji Dai

Beilstein J. Org. Chem. 2016, 12, 702–715, doi:10.3762/bjoc.12.70

• , path b). Although there have been major advancements made in the field of direct sp3 C–H bond activation and functionalization adjacent to nitrogen in saturated N-heterocycles and acyclic amines [25][26][27], C–H functionalization of piperazines has been a daunting challenge. In comparison to the well

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• Pd-catalyzed Suzuki–Miyaura reaction. The C–H bond activation process was believed to be initiated by the oxidation effect of the Cu(II) catalyst to give intermediate 54 which was further oxidized to provide cation intermediate 55. The deprotection of 55 gave finally the halogenated products 52

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

• coupling partners. On the other hand, benzenesulfonyl chlorides were recently introduced as powerful arylating agents, through metal-catalyzed C–H bond activation [47][48][49][50][51][52][53][54][55]. Such desulfitative direct arylations sometimes offered different regioselectivities, e.g., thiophenes were

Sequential decarboxylative azide–alkyne cycloaddition and dehydrogenative coupling reactions: one-pot synthesis of polycyclic fused triazoles

• Kuppusamy Bharathimohan,
• Thanasekaran Ponpandian,
• A. Jafar Ahamed and
• Nattamai Bhuvanesh

Beilstein J. Org. Chem. 2014, 10, 3031–3037, doi:10.3762/bjoc.10.321

• organic azides. This kind of decarboxylative CuAAC reaction has not been further investigated. Transition metal-mediated C–H bond activation has become a hot topic in recent years [7][8][9][10][11]. Formally, it requires insertion of a transition metal (usually Pd, Ru, Rh or Ir) across a strong C–H bond

Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives

• Fatma Belkessam,
• Aidene Mohand,
• Jean-François Soulé,
• Abdelhamid Elias and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309

• -diheteroarylated thiophenes bearing two different heteroaryl units. Keywords: aryl halides; catalysis; C–H bond activation; direct arylation; heteroarenes; palladium; Introduction 2,2':5',2"-Terthiophene (or 2,5-di(2-thienyl)thiophene) (Figure 1) and many of its derivatives are important structures due to their

• ][9][10][11][12][13][14][15][16]. However, an organometallic derivative must be prepared to perform such reactions. In 1990, Ohta and co-workers reported the Pd-catalyzed direct arylation of heteroaromatics using aryl halides as coupling partners via a C–H bond activation [17][18]. Since then Pd

Hindered aryl bromides for regioselective palladium-catalysed direct arylation at less favourable C5-carbon of 3-substituted thiophenes

• Rongwei Jin,
• Charles Beromeo Bheeter and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 1239–1245, doi:10.3762/bjoc.10.123

• different aryl units. Keywords: aryl bromides; atom economy; C–H bond activation; palladium; regioselectivity; thiophenes; Introduction As thiophenes bearing aryl substituents are known to be present in several bioactive molecules and are used as precursors of materials, the regioselective introduction of

• aryls on thiophenes is an important research area in organic synthesis. The coupling of thiophene derivatives with aryl halides via a C–H bond activation/functionalisation [1][2][3][4][5][6][7][8][9][10][11][12] provides an environmentally attractive and cost-effective procedure for the preparation of a

• organometallics reducing the number of steps to prepare these arylthiophenes. The regioselective arylation via a Pd-catalysed C–H bond activation at carbon C5 of 2-substituted thiophenes has been largely described in recent years [13][14][15][16][17][18][19][20][21][22]. On the other hand, the Pd-catalysed direct

An easy direct arylation of 5-pyrazolones

• Hao Gong,
• Yiwen Yang,
• Zechao Wang and
• Chunxiang Kuang

Beilstein J. Org. Chem. 2013, 9, 2033–2039, doi:10.3762/bjoc.9.240

• Education, Shanghai 200092, China 10.3762/bjoc.9.240 Abstract A mild, efficient and catalytic ligand-free method for the direct arylation of 5-pyrazolones by Pd-catalyzed C–H bond activation is reported. The process smoothly proceeds and yields are moderate to excellent. Keywords: arylation; aryl halide

• ; C–H bond activation; Pd(OAc)2; pyrazolone; Introduction 5-Pyrazolones are attracting considerable research interest because of their unique chemical properties and their structures that facilitate their application as biological and pharmaceutical intermediates and products [1][2][3]. Over the

• have been described [15]. In this paper, we report a convenient and catalytic ligand-free synthesis of a series of 4-aryl-5-pyrazolones 3 from 5-pyrazolones 1 and aryl halides 2 (Scheme 1). The direct arylation of 5-pyrazolones by Pd-catalyzed C–H bond activation was utilized. Results and Discussion We

AgOTf-catalyzed one-pot reactions of 2-alkynylbenzaldoximes with α,β-unsaturated carbonyl compounds

• Qiuping Ding,
• Dan Wang,
• Puying Luo,
• Meiling Liu,
• Shouzhi Pu and
• Liyun Zhou

Beilstein J. Org. Chem. 2013, 9, 1949–1956, doi:10.3762/bjoc.9.231

• -alkenylated isoquinoline 4 was synthesized via a Pd-mediated C–H bond activation approach in a one-pot reaction. The intermediate isoquinoline N-oxide A was produced in situ from 2-alkynylbenzaldoximes and reacted with the α,β-unsaturated carbonyl compound 2e to yield 1-alkenylated isoquinoline 4 (Scheme 3

• . Procedure for the synthesis of 1-alkenylated isoquinoline 4 by a Pd-mediated C–H bond activation approach: A solution of 2-alkynylbenzaldoxime 1a (0.3 mmol) and AgOTf (0.015 mmol, 5 mol %) in CH2Cl2 (2 mL) was stirred at rt for 2 h. Then, the solvent was removed under reduced pressure. Subsequently, a

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• . Moreover, recent experimental and theoretical reports are analyzed, which suggest the involvement of such intermediates in reaction mechanisms, particularly C–H bond-activation processes. Keywords: C–H bond activation; intermediate; platinum(II); reactive intermediates; three-coordinate; T-shaped; Review

• of olefins into M–H bonds, electrophilic attack at Pt–C bonds, and ligand cycloplatination [2]. Likewise, related Pd(II) complexes [3][4] are relevant in cross-coupling reactions and C–H bond-activation processes. The accessibility of three-coordinate Pd(II) species have been recently discussed [5

• complexes in solution will be discussed. Finally, participation of three-coordinate Pt(II) intermediates in reactions, mainly C–H bond-activation processes and ligand exchanges, will be analyzed. A thorough review on the bonding and stereochemistry of three-coordinate transition-metal compounds was

Complete σ* intramolecular aromatic hydroxylation mechanism through O₂ activation by a Schiff base macrocyclic dicopper(I) complex

• Albert Poater and
• Miquel Solà

Beilstein J. Org. Chem. 2013, 9, 585–593, doi:10.3762/bjoc.9.63

• and C–O bond formation, followed finally by a proton transfer to an alpha aromatic carbon that immediately yields the product [CuII2(bsH2m-O)(μ-OH)]2+. Keywords: aromatic hydroxylation; C–H bond activation; C–H functionalization; copper; DFT calculations; mechanism; Schiff base; Introduction Bearing

N-Heterocyclic carbene–palladium catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

• Ismail Özdemir,
• Nevin Gürbüz,
• Nazan Kaloğlu,
• Öznur Doğan,
• Murat Kaloğlu,
• Christian Bruneau and
• Henri Doucet

Beilstein J. Org. Chem. 2013, 9, 303–312, doi:10.3762/bjoc.9.35

• with heteroarenes. Keywords: aryl chlorides; atom-economy; C–H bond activation; C–H functionalization; carbenes; palladium; pyrroles; Introduction N-Heterocyclic carbenes (NHC) have emerged as an important class of ligands in the development of homogeneous catalysis [1][2][3][4][5][6][7][8][9]. Such

• palladium-catalyzed direct arylation of various heteroaromatics including pyrroles by a C–H bond activation using aryl halides has met great success in recent years, allowing the synthesis of a wide variety of arylated heteroaromatics in only one step [20][21][22][23][24][25]. However, there are still

• the palladium-catalyzed coupling of heteroarenes with aryl halides through a C–H bond activation has been largely explored. On the other hand, the influence of carbene ligands for such couplings remains largely unexplored [40][41][42][43][44][45][46][47]. Quite congested N-heterocyclic carbene