Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• presence of 1 in methanol/n-Bu4NClO4 to form Co(III)–RF complexes with deiodination. These complexes released RF radicals on the Co(III)-bond cleavage through visible-light irradiation. The resultant radicals reacted with aromatic reagents to form the target products through direct C–H functionalization

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• /arylzinc reagents [35][36]. However, most of these methods require harsh reaction conditions, external additives and high temperatures. The reactions need prefunctionalized arenes, while a direct C–S sulfenylation by C–H functionalization would be more desirable and cost effective. So far, only a few

• reports on direct C–H functionalization using transition metals or metal free [37][38][39] conditions and different sources of sulfur, for example arylsulfonyl chlorides, sodium arylsulfinates, sulfinic acids and arylsulfonyl hydrazides have been reported (Scheme 1). However, the protocols require

• charge transfer using Cs2CO3 as base [41]. Two recent reports showed the synthesis of C-3 sulfenylated indoles and 3-sulfenylimidazopyridine via C–H functionalization using Rose Bengal as photocatalyst [42][43]. In general, the arylation reactions use the reductive cycle of the photocatalyst and for this

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

• synthesis owing to the necessity of green chemistry for the modern universe [1][2][3]. In this context, catalytic C–H functionalization has been acknowledged as an atom- and step-economical process [4][5][6]. A wide range of transition metal-catalyzed non-directed or directing group assisted C–H activation

• activation reactions (Scheme 1) [29][30]. Following to these pioneering works, the groups of Kochi [31], Kisch [32], Klein [33][34], and Brookhart [35] have made their crucial contributions in the cobalt-mediated/catalyzed C–H functionalization. In recent years, Yoshikai [36], Kanai/Matsunaga [37], and

• -valent cobalt system for C–H functionalization [16][36]. Thus, the reaction of 2-aryl pyridines 3 with internal alkynes in the presence of 10 mol % CoBr2, 20 mol % PMePh2, and 1 equiv of MeMgCl as a reductant yielded ortho alkenated products 4 with high regio- and stereoselectivities (Scheme 5) [36]. The

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• of aryl iodide. The latter is then used for a sequential ruthenium-catalyzed ortho-C–H functionalization directed by the pyrazole group (Scheme 37) [76]. Starting from non-symmetrical diaryl-λ3-iodanes, the electron-poorest or more sterically hindered aromatic group is first transferred to the 3,5

Rhodium-catalyzed C–H functionalization of heteroarenes using indoleBX hypervalent iodine reagents

• Erwann Grenet,
• Ashis Das,
• Paola Caramenti and
• Jérôme Waser

Beilstein J. Org. Chem. 2018, 14, 1208–1214, doi:10.3762/bjoc.14.102

• procedures have been described for the modification of pyridinones to introduce other substituents, especially based on highly efficient C–H functionalization methods [10]. Very recently, several research groups have selectively functionalized the C-6 C–H bond by using a 2-pyridyl directing group on the

• -methylindole and 2-iodobenzoic acid [24]. While the reaction conditions previously developed in our group for the C–H functionalization of 2-phenylpyridine [24] failed for the coupling of 5a with 6a (Table 1, entry 1), we were pleased to see that addition of 0.15 equiv Zn(OTf)2 allowed a full conversion to the

• compounds with pyridinone, quinolone and indole cores. C–H functionalization of pyridinones and quinoline N-oxides. Scope and limitations of the Rh-catalyzed C–H activation of [1,2'-bipyridin]-2-one. Scope of the Rh-catalyzed peri C–H activation of quinoline N-oxides. Product modifications. Optimization of

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

• ), phenyliodine(III) bis(trifluoroacetate) (PIFA), and iodosobenzene, has since become a popular choice for benzylic oxidations, which further expanded the scope and availability of methods for direct C–H functionalization and several coupling reactions [42][43][44][45][46][47][48][49][50]. As such, we reported

• /ethyl acetate) to give the benzylic C–H carboxylation product in the indicated yield; the physical and spectral data of the carboxylation products (3h, 4h, 5h, 6h) matched those previously reported (see Supporting Information File 1). Hypervalent iodine(III)-induced benzylic C–H functionalization for

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• ) from ketones [13][14][15][16][17]. Over the last several years, we and others have developed a series of directed arene C–H functionalization reactions with organic electrophiles under low-valent cobalt catalysis [18][19][20][21]. In particular, our group and the Ackermann group have independently

• demonstrated that the combination of a cobalt–N-heterocyclic carbene (NHC) catalyst and a Grignard reagent allows for the arene C–H functionalization with organic halides and pseudohalides under the assistance of nitrogen directing groups [17][22][23][24][25][26][27]. In this connection, Ackermann developed a

• -directed arene C–H alkenylation reaction with alkenyl phosphates using a different cobalt–NHC catalyst (Scheme 1b) [28]. Meanwhile, we have also demonstrated that pivaloyl N–H imine serves as a powerful directing group for cobalt-catalyzed arene C–H functionalization reactions such as the hydroarylation of

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

• electrochemical C–H bond functionalization, leading to the formation of new C–C, C–N, C–O and C–S bonds [28][29][30][31]. Herein, we report the electrochemical α-C–H functionalization of N-arylglycine esters with C–H nucleophiles using n-Bu4NI as redox catalyst (Scheme 1). The chemistry was performed in an

Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline

• Benedikt C. Melzer,
• Jan G. Felber and
• Franz Bracher

Beilstein J. Org. Chem. 2018, 14, 130–134, doi:10.3762/bjoc.14.8

• methods have been published over the decades for the construction of highly substituted isoquinolines [4]. Alternatively, subsequent functionalization of isoquinolines is feasible, e.g., via Pd-catalyzed C–H functionalization [5] or regioselective direct ring metalation (at C1) [6][7][8]. General aspects

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

• ]. Advantageously this methodology was applicable for both solid and liquid olefins. Mechanochemical C–H functionalization Transition-metal-catalyzed activation and functionalization of inert C–H bonds of organic molecules provides a broad avenue in the synthesis of wide range of compounds. In 2015, Bolm and co

• Rh, Cu(OAc)2 as a redox modulator and dioxygen as a terminal oxidant (Scheme 50). This efficient technique was turned out to be a greener alternative to the common and mechanistically similar solution based method. They have also extended mechanochemical C–H functionalization methodology by varying

• developed a mechanochemical synthesis of an indole moiety via a Rh-catalyzed C–H functionalization strategy under planetary ball mill [187]. Using acetanilide and diphenylacetylene as the alkyne component in presence of 5 mol % Rh catalyst and 2.5 mol % Cu(OAc)2 and 1 atm O2 as terminal oxidant they could

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• the chlorination and other C–H functionalization of (2-pyridyl)arenes. Together with this work, some other work on C–H acyloxylation provided an indirect pathway for the synthesis of phenols from arenes [54]. In 2014, Shi and co-workers designed a removable bidentate functional group, which could

Green chemistry

• Luigi Vaccaro

Beilstein J. Org. Chem. 2016, 12, 2763–2765, doi:10.3762/bjoc.12.273

• , including “Strategies in asymmetric catalysis” by Tehshik P. Yoon [6], “Organometallic chemistry” by Bernd F. Straub and Lutz H. Gade [7], “C–H functionalization/activation in organic synthesis” by Richmond Sarpong [8], “Bifunctional catalysis” by Darren J. Dixon [9], “Sustainable catalysis” by Nicholas J

C–H Functionalization/activation in organic synthesis

• Richmond Sarpong

Beilstein J. Org. Chem. 2016, 12, 2315–2316, doi:10.3762/bjoc.12.224

• Richmond Sarpong Department of Chemistry, University of California, Berkeley, 841A Latimer Hall, Berkeley, CA 94720, USA 10.3762/bjoc.12.224 Keywords: C–H activation; C–H functionalization; The last decade has seen an explosion in research reports in the area of C–H functionalization/activation

• therefore highly desirable to be able to take advantage of the myriad of C–H groups in organic molecules as functional handles for bond formation, and in some cases, bond-breaking processes. “Modern” C–H functionalization/activation can trace its roots to the “clarion call” by Bergman and co-workers [1] in

• C–H functionalization/activation reactions. The growth in popularity of C–H functionalization/activation in organic synthesis can be attributed to the desire to implement more sustainable methods for synthesis and to achieve novel reactivity and selectivity in building molecules. A lot of exciting

On the cause of low thermal stability of ethyl halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

• organic chemists ever since Theodor Curtius synthesized ethyl diazoacetate (EDA, 1) for the first time in 1883 [1]. Even today, after more than a century of research, diazo compounds still play an important role in state-of-the-art organic chemistry in areas such as for example C–H functionalization [2

Palladium-catalyzed picolinamide-directed iodination of remote ortho-C−H bonds of arenes: Synthesis of tetrahydroquinolines

• William A. Nack,
• Xinmou Wang,
• Bo Wang,
• Gang He and
• Gong Chen

Beilstein J. Org. Chem. 2016, 12, 1243–1249, doi:10.3762/bjoc.12.119

• diverse substitution patterns from readily accessible starting materials. New synthetic strategy for THQs via PA-directed C−H functionalization. Preparation of iodo-substituted THQs via PA-directed C−H functionalization strategy. a) ArI (2 equiv), Pd(OAc)2 (10 mol %), (BnO)2PO2H (20 mol %), Ag2CO3 (1.5

• −H functionalization reactions starting from readily accessible aryl iodide and alkylamine precursors (Scheme 1) [8]. Alkylpicolinamides were first subjected to Pd-catalyzed γ-C(sp3)−H arylation with aryl iodides to form γ-arylpropylpicolinamides [9][10][11][12][13][14][15][16][17][18][19][20]. These

• many natural products and pharmaceutical agents [1][2]. Efficient and generally applicable methods for the synthesis of THQs with complex substitution patterns are still in great demand [3][4][5][6][7]. Recently, we reported a synthetic strategy for THQs based on picolinamide (PA)-directed sequential C

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

• -arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction. Keywords: C−H functionalization; intramolecular dehydrogenative coupling (IDC); iodine; N-iodosuccinimide; oxidants; 2-oxindoles; Introduction The

• C−H functionalization is an attractive synthetic strategy used in organic synthesis for the development of atom- and step-economical routes [1][2][3][4][5][6][7][8][9][10]. In recent years it was witnessed a mushrooming growth in the number of reports in the literature owing to the efficiency of the

Synthesis of β-arylated alkylamides via Pd-catalyzed one-pot installation of a directing group and C(sp³)–H arylation

• Yunyun Liu,
• Yi Zhang,
• Xiaoji Cao and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2016, 12, 1122–1126, doi:10.3762/bjoc.12.108

• ][27]. As a representative protocol for the synthesis of C–H elaborated alkyl/arylamides, the AQ-assisted C–H functionalization reactions have been broadly investigated and applied [28][29][30][31][32][33][34]. Since the prior preparation and purification of N-AQ amides have been required in all these

• functionalization chemistry [35][36][37][38][39][40], we have executed efforts to the AQ-assisted β-C–H functionalization reactions of alkylamides via activation of the C(sp3)–H bond, a classical protocol toward β-arylamide synthesis. While the known examples, including C(sp3)–H alkylation, arylation or oxygenation

• known syntheses, a domino process by which the AQ can be linked directly to the raw substrates to enable the subsequent arylation transformation in one pot would be highly favorable for enhancing step economy. Upon this assumption as well as our interest in both domino reactions and C–H

Iodine-mediated synthesis of 3-acylbenzothiadiazine 1,1-dioxides

• Long-Yi Xi,
• Ruo-Yi Zhang,
• Lei Shi,
• Shan-Yong Chen and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2016, 12, 1072–1078, doi:10.3762/bjoc.12.101

• -acylbenzothiadiazine 1,1-dioxides from 2-aminobenzenesulfonamides and acetophenones via iodine-mediated sp3 C–H functionalization. Results and Discussion We commenced our studies by heating acetophenone (1a), 2-aminobenzenesulfonamide (2a) and I2 in DMSO for 12 h. To our delight, the desired product was isolated in 60

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

• intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied. Keywords: arylation; cationic palladium; C–H functionalization; green chemistry; olefination; Introduction Transition metal-catalyzed, direct functionalization of aryl C–H bonds has made

• –H bonds. High temperatures are frequently required to realize aromatic C–H functionalization (>120 °C), increasing the potential for side reactions and functional group compatibility issues. Indeed, C–H activation transformations until recently have rarely proceeded at ambient temperature due to the

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• 53. A subsequent transannular C–H functionalization at the site of a weakly acidic proton then produces the bridged product 54. While an innovative transformation, it should be noted that a full equivalent of Wilkinson’s catalyst is needed as there is no catalytic turnover observed. Bridged

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

• into the C(sp3)–H bond catalyzed by a new bulky cyclopropylcarboxylate-based chiral dirhodium complex. 2,2,2-Trichloroethyl (TCE) aryldiazoacetates to improve the scope, regio- and enantioselective of the carbenoid insertion into primary C(sp3)–Hs bond by (R)-74. Sequential C–H functionalization

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• the late-stage C–H functionalization of complex alkaloids and drug molecules (Scheme 3) [25]. C–H bond insertions at the allylic and benzylic positions Metal–carbene C–H insertion is also favored for allylic and benzylic sites. In 2014, Davies and co-workers reported an enantioselective C–H insertion

• and Etienne reported a perfluorinated F21-tris(pyrazoly)borate (F21-Tp) scorpionate ligand, which enhanced alkane C–H functionalization by carbene insertion with (F21-Tp)Cu and (F21-Tp)Ag catalysts (Figure 1) [38]. In particular, with silver catalyst remarkably low catalyst loading (ca. 0.5%), and

• (sp3)–H bonds. Rh(II)-catalyzed site-selective and enantioselective C–H functionalization of methyl ether. Late-stage C–H functionalization with Rh(II)-catalyzed carbene C(sp3)–H insertion. The Rh(II)-catalyzed selective carbene insertion into benzylic C–H bonds. The structure–selectivity relationship

Gold-catalyzed direct alkynylation of tryptophan in peptides using TIPS-EBX

• Gergely L. Tolnai,
• Jonathan P. Brand and
• Jerome Waser

Beilstein J. Org. Chem. 2016, 12, 745–749, doi:10.3762/bjoc.12.74

• under mild conditions and could be applied to peptides containing other nucleophilic and aromatic amino acids, such as serine, phenylalanine or tyrosine. Keywords: alkynes; C–H functionalization; gold catalysis; hypervalent iodine; peptides; Introduction Alkynes have always been important building

• and unfolding, or protein engineering to install more accessible cysteines, are usually required. For these reasons, it is important to develop selective alkynylation methods in order to functionalize other amino acids. The direct C–H functionalization of aromatic compounds is an attractive method for

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

• pharmaceuticals. Herein we summarize the current synthetic methods available to perform C–H functionalization on piperazines in order to lend structural diversity to this privileged drug scaffold. Multiple approaches such as those involving α-lithiation trapping, transition-metal-catalyzed α-C–H

• functionalizations, and photoredox catalysis are discussed. We also highlight the difficulties experienced when successful methods for α-C–H functionalization of acyclic amines and saturated mono-nitrogen heterocyclic compounds (such as piperidines and pyrrolidines) were applied to piperazine substrates. Keywords

• : α-lithiation; C–H functionalization; heterocycle; photoredox catalysis; piperazine; Introduction Piperazine is one of the most important saturated N-heterocycles frequently found in life-saving small-molecule pharmaceuticals [1]. In a recent statistical study done by Njardarson and co-workers

Copper catalysis in organic synthesis

• Sherry R. Chemler

Beilstein J. Org. Chem. 2015, 11, 2252–2253, doi:10.3762/bjoc.11.244

• field of copper-catalysis from 7 countries make up this Thematic Series, “Copper catalysis in organic synthesis”. Contributions include authoritative reviews on the latest developments in copper-catalyzed Click applications, C–N cross-coupling, C–H functionalization, trifluoromethylations, asymmetric