Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• area have recently culminated in two communicated syntheses of 6,7-dideoxysqualestatin H5 (DDSQ (2), Figure 1) [12][13]. The centrepiece of both of these strategies is a rhodium(II)-catalysed tandem carbon ylide formation from a diazoketone 3 (Scheme 1) and stereoselective [3 + 2] cycloaddition with a

Intramolecular cascade annulation triggered by rhodium(III)-catalyzed sequential C(sp²)–H activation and C(sp³)–H amination

• Liangliang Song,
• Guilong Tian,
• Johan Van der Eycken and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 571–576, doi:10.3762/bjoc.15.52

• Macromolecular Chemistry, Ghent University, Krijgslaan 281 (S.4), B-9000 Ghent, Belgium Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya Street 6, Moscow, Russia 10.3762/bjoc.15.52 Abstract A rhodium(III)-catalyzed intramolecular oxidative annulation of O-substituted N

• activation; rhodium; acrylamide; heterocycles; Introduction Over the last decade, transition metal-catalyzed C(sp2)–H activation has emerged as an efficient strategy to access complex molecules [1][2][3][4][5][6]. Among the methodologies, RhIII-catalyzed oxidative annulation of a C(sp2)–H bond with 2π

• (Scheme 1b) [29][30][31]. Inspired by this work, we envisaged that tricyclic indolizinones could be built through rhodium(III)-catalyzed sequential C(sp2)–H activation and C(sp3)–H amination of O-substituted N-hydroxyacrylamides (Scheme 1c). Results and Discussion We selected N-hydroxyacrylamide 1a as our

Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives

• Wentong Liu,
• Yi Kuang,
• Zhifan Wang,
• Jin Zhu and
• Yuanhua Wang

Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48

• cycloaddition chemistry based on compound 1. Zheng et al. [7] first reported on the [3 + 2] cycloaddition reaction of 1 with an alkene or alkyne mediated by visible light by the aid of the photocatalyst [Ru(bpz)3](PF6)2. Our group reported the metal catalyst itself, particularly the dinuclear rhodium complex

• study the cycloaddition in dichloromethane (DCM) with 1 mol % starting catalyst loading under the previously reported conditions [18]. In the absence of a catalyst, no cycloaddition product 3a formed (Table 1, entry 1). We then studied the effect of common rhodium catalysts on the reactions. When 1 mol

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• ]. Many of these complexes contain rhodium or iridium coordinated with fully (methyl)substituted cyclopentadienyl ligands and bis-coordinating diamino ligands as shown in Figure 7. The reducing agent may be a formate anion as a source of hydride, triethanolamine as an electron donor in the case of

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• (TBS) ether of propargyl alcohol by a rhodium-catalyzed cyclopropanation with an aryldiazoacetate followed by reduction of the ester moiety and protecting group manipulation. Phosphinite 6a, generated from alcohol 5a under standard conditions, did not undergo a [2,3]-sigmatropic rearrangement into the

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• ) and 3,3-dibenzylcyclopropene (1c). Thus, divinylcyclopropane 3b was obtained in reasonable yields with both catalysts (69% Zn and 75% Rh), albeit better selectivity was obtained again with rhodium(II) catalyst (endo/exo = 17:1). In contrast, the reaction with 1c led to the corresponding cyclopropane

• equimolar mixture of cis/trans diastereoisomers (cis refers to both vinyl substituents). Even though the lack of selectivity was already noticed by Uemura and co-workers in related reactions [17], we attempted the reaction with other zinc salts or rhodium(II) carboxylates as catalysts. Unfortunately, these

• compounds, which led again to oxy-Cope rearranged or [4 + 3]-cycloaddition products using rhodium catalysts [14][28][29][30], or to a C2-allylation of furan with gold catalysts [31]. Finally, to compare the reactivity of cyclopropenes and vinyldiazo compounds, we probed the reaction of 1a with 1,4

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• of azide to Rh2(esp)2 complex (bis[rhodium-(α,α,α’,α’-tetramethyl-1,3-benzenedipropionic acid)]) and extrusion of N2. Then, the Rh-nitrene intermediate 65 goes through an intramolecular single electron transfer (SET) to give the nitrogen-centered radical intermediate 66 [87][88][89][90]. Next, the

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• copolymerization of ethylene and ethyl diazoacetate with rhodium-based catalysts (Scheme 2a). Ethyl cyclopropanecarboxylate has been prepared in several ways, alternative to the direct carbene addition to ethylene (Scheme 2b): ring contraction of 2-halocyclobutanone [5], cyclization of alkyl 4-halobutanoates [6

• experiments, we tested several group 11 metal-based catalysts that have been described in our group for the catalytic transfer of the CHCO2Et group from ethyl diazoacetate (N2=CHCO2Et, EDA), as well as a rhodium-based catalyst. The experimental procedure started upon placing the catalyst (0.02 mmol) into a

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• to the syn ligand, as suggested by experimental and theoretical studies on the steric and electronic properties of N-cyclohexyl, N’-isopropylphenyl NHC ligands of 191 and 192 evaluated using the corresponding rhodium complexes [60]. A development of this study, which considered the utilization of

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• introduction of nitrogen in the convenient position (C3) could be performed by a stereopecific nitrene insertion reaction catalyzed by rhodium(II) complexes [24][25]. Herein, we describe our outcomes related to the implementation of this strategy for the synthesis of L-vancosamine derivative 1, as well as its

• data [9]. As an example, the expected protected glycal of L-daunosamine 3 [9][47] was obtained by regioselective rhodium nitrene insertion thus demonstrating the usefulness of this strategy for the synthesis of such compounds. Conclusion We developed an alternative route to 3-aminoglycals through ring

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

• triflates [8], and diazonium salts [9]. Typical metals used are palladium [10][11][12][13], copper [14][15][16][17][18][19][20][21], nickel [22][23][24], iron [25][26][27][28][29], cobalt [30][31][32], and rhodium [33][34]. Aryl sulfides are also synthesized by cross coupling of thiols and aryl Grignard

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

• review, the Co- and Rh-catalyzed transformation of CO2 via carbon–carbon bond-forming reactions is summarized. Combinations of metals (cobalt or rhodium), substrates, and reducing agents realize efficient carboxylation reactions using CO2. The carboxylation of propargyl acetates and alkenyl triflates

• [2 + 2 + 2] cycloaddition of diynes and CO2 proceeds to afford pyrones. Keywords: carbon dioxide; carboxylation; cobalt; homogeneous catalysts; rhodium; Introduction Carbon dioxide (CO2) is one of the most important materials as renewable feedstock [1][2][3][4]. However, the thermodynamic and

• . We also summarize carboxylation reactions catalyzed by rhodium that is a homologous element of cobalt. Carboxylations of arylboronic esters are described. Rh complexes are also effective catalysts in C(sp2)–H carboxylation reactions. Employing Et2Zn or visible light, the Rh-catalyzed

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• ·2BH3 matched those reported above. The 13C{1H} NMR spectra (CDCl3, 100 MHz) of in,out-2·2BH3, (in,in/out,out)-2·2BH3, 6·2BH3, and the crude reaction mixture after hydrogenation from Scheme 5 (top); doublets are marked with an asterisk. Syntheses of gyroscope like platinum and rhodium complexes and

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 of F2 give intermediate F3. Finally, protonolysis provides the desired product 45 and an active Co(III)Cp*. Due to the low activation energy, the thermodynamically less stable Z diastereomer is preferred in the reaction, which is in contrast to the rhodium(III)-catalyzed reaction [82]. Later, Li

• *(C6H6)][B(C6F5)4]2 and LiOAc gave alcohol products 62 with high diastereoselectivity at ambient reaction conditions. The unique nature of cobalt was well presented by its superior reactivity and diastereoselectivity and it outmatched the rhodium catalyst. Different pyrazole derivatives with a wide range

Coordination-driven self-assembly vs dynamic covalent chemistry: versatile methods for the synthesis of molecular metallarectangles

• Li-Li Ma,
• Jia-Qin Han,
• Wei-Guo Jia and
• Ying-Feng Han

Beilstein J. Org. Chem. 2018, 14, 2027–2034, doi:10.3762/bjoc.14.178

• desired tetranuclear metallarectangles were synthesized by using coordination-driven self-assembly of half-sandwich rhodium-based organometallic clip units and organic ligands. The reaction of such an organometallic clip with 4-formylpyridine provided a dinuclear molecular tweezer with pendant aldehyde

• self-assembly; dynamic covalent chemistry; half-sandwich rhodium complex; metallarectangles; one-pot reaction; supramolecular chemistry; Introduction Over the past two decades, supramolecular structures with organometallic half-sandwich fragments have attracted much attention, including

• 3a. The peak was isotopically resolved and agrees well with the theoretical isotopic distribution. In addition, the IR spectrum of the rhodium metallarectangle 3a showed a C=N stretching band at 1618 cm−1. The same self-assembly protocol can also be used for the synthesis of metallarectangle 3b. 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

• auto-amination process enables to address the issue of chemoselectivity in some cases. For example, the Suzuki–Miyaura coupling allows for introducing a pyridinyl or a furyl ring that are not compatible with the rhodium-catalyzed oxidizing amination reactions. In a similar manner, the group of

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• –Hagihara reaction was developed by Dauban and co-workers (Scheme 16) [47]. The first step of this sequence includes an iodine(III)-mediated rhodium-catalysed enantioselective amination of an unactivated C(sp3)–H bond with a chiral sulfonimidamide 31. Afterwards, the iodoarene byproduct of the first step is

• the sulfonimidamide 31 in the presence of the chiral rhodium(II) catalyst A. Hereby, one equivalent of iodoarene 2 is released. The insertion of the nitrene species into the C(sp3)–H bond affords the amination product C, which is the final product of the first reaction step. In the following step, C

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

• heteroarenes was realized using the benziodoxolone hypervalent iodine reagents indoleBXs. Functionalization of the C–H bond in bipyridinones and quinoline N-oxides catalyzed by a rhodium complex allowed to incorporate indole rings into aza-heteroaromatic compounds. These new transformations displayed complete

• regioselectivity for the C-6 position of bipyridinones and the C-8 position of quinoline N-oxides and tolerated a broad range of functionalities, such as halogens, ethers, or trifluoromethyl groups. Keywords: C–H activation; hypervalent iodine; indoleBX; indoles; pyridinones; rhodium catalysis; Introduction

• nitrogen and a transition metal catalyst (reaction 1, Scheme 1A) [11][12][13][14][15][16][17][18][19]. In particular, Li and co-workers have used ethynylbenziodoxolone (EBX) hypervalent iodine reagents to achieve a regiodivergent alkynylation of the pyridinone core employing either a gold(I) or a rhodium

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• successfully developed a rhodium-catalyzed asymmetric arylation process leading to triarylmethanes 25. With the application of mild reaction conditions (40 °C, 15 h), a high enantioselectivity (≥90% ee) was reached with good to excellent yields. (Scheme 2). Starting from 2-naphthol, 2,2-disubstituted 3

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

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• ). However, a full conversion of thioamide 1a in these experiments was not achieved in spite of the 1.2-fold excess of diazomalonate 2a used in the process. Further increasing the amount of diazomalonate 2a (up to 2.1 equiv) in the reaction with rhodium tetrapivalate resulted in the enhancement of the yield

• was established that the main products of diazoesters 2a,b,d in reactions with thioacetamides 1a–e, catalyzed by rhodium complexes, were sulfur-containing heterocycles, 5-amino-3-(alkoxycarbonylamino)thiophene-2-carboxylates 3, 2-(5-amino-2-methoxycarbonylthiophen-3-yl)aminomalonates 4 and (2-cyano-5

• evidence of high reactivity of rhodium complexes in these processes [54][55]. This literature data brought us to the suggestion that low reactivity of diazoesters 2 toward thioamides 1 in the presence of Rh(II)-catalysts is caused by binding the two latter chemicals to furnish the adducts of the type 6

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• latter transformation was a rhodium octanoate-catalyzed intramolecular carbenoid insertion into an ortho CAr–H bond (Scheme 1) [21][22], which proceeded with good yields in most cases. However, with non-equivalent aryl ortho-positions in the starting diazo compounds, mixtures of regioisomers – virtually

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

• -workers have successfully demonstrated rhodium(III)-catalyzed C–H bond functionalization under mechanochemical conditions [182]. Advantageously, the developed method adopted mild reaction conditions, i.e., in solvent-free medium and at room temperature. It required a minimum amount of toxic metal salt of

• the metal catalyst from rhodium to iridium. In 2016, using an Ir(III) catalyst an unprecedented ortho-selective Csp2–H bond amidation of benzamides with sulfonyl azides as the amide source was done under solvent-free ball mill conditions (Scheme 51) [183]. They could also isolate cyclic iridium

• complex H in ball-milling conditions. In 2015, the Bolm group reported the synthesis of [Cp*RhCl2]2 under LAG from rhodium(III) chloride hydrate and pentamethylcyclopentadiene (Cp*H) at lesser reaction time than solution-based protocols. Subsequently, they utilized the [Cp*RhCl2]2 for the solvent-free

Ni nanoparticles on RGO as reusable heterogeneous catalyst: effect of Ni particle size and intermediate composite structures in C–S cross-coupling reaction

• Debasish Sengupta,
• Koushik Bhowmik,
• Goutam De and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 1796–1806, doi:10.3762/bjoc.13.174

• first palladium-catalyzed arylation of thiols was reported by Migita and co-workers in 1980 [5], and soon after Cristau and co-workers developed a nickel-catalyzed route for C–S cross-coupling reactions [6]. Other metals such as copper [7], cobalt [8], iron [9], rhodium [10], manganese [11], indium [12

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159