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

• expensive metal catalysts or even metal-free reactions. Recently, there has been rapid progress toward the use of C–H bonds as a reactive functional group [6]. While it would be highly desirable to utilize C–H/C–H coupling reactions [7], low reactivity and selectivity are significant obstacles. The use of

• ], and Cu [34][35][36][37]) or an aluminum-based metal-organic framework [38], and there are several reports of metal-free direct arylation reactions in which the reaction is promoted with 2–3 equivalents KO(t-Bu) and (typically) 10–30 mol % of an additive [39][40][41][42][43][44][45][46][47][48]. The

• begin the cycle anew. The mechanism explains the metal-free direct arylation catalysis, but there has been some question about the initiation step. As KO(t-Bu) does not have sufficient reducing power to generate ArI•−, it has been proposed that initiation could arise from the reaction of ArI and KO(t-Bu

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

• Federica Santoro,
• Matteo Mariani,
• Federica Zaccheria,
• Rinaldo Psaro and
• Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

• substrates under mild reaction conditions. Keywords: no solvent; S-alkylation; solid acids; thioethers; transition-metal-free; Introduction The need for more sustainable processes in the fine chemical industry is growing continuously. An optimal use of resources, both energy and starting materials, and a

• consequent waste reduction can be recognized as important factors for environmental protection. In this context organic synthesis over heterogeneous catalysts instead of homogeneous ones or without employing any organic solvents is of paramount interest [1][2]. In particular, metal-free coupling reactions

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• Riccardo Porta Alessandra Puglisi Giacomo Colombo Sergio Rossi Maurizio Benaglia Dipartimento di Chimica, Università di Milano, Via Golgi 19, 20133, Milano, Italy 10.3762/bjoc.12.257 Abstract The metal-free reduction of nitro compounds to amines mediated by trichlorosilane was successfully

• plethora of further synthetic elaborations. Among the different available methodologies for the reduction of nitro compounds [8], we have recently reported a very convenient, mild, metal-free and inexpensive procedure, of wide applicability [9][10]. The simple combination of trichlorosilane (HSiCl3) and a

• transformation safer and more appealing in view of an industrial application and a possible scale-up of the process [18][19][20]. Herein we report a very convenient, metal-free reduction of both aromatic and aliphatic nitro derivatives, including chiral compounds, to amines with HSiCl3 under continuous-flow

Synthesis of three-dimensional porous hyper-crosslinked polymers via thiol–yne reaction

• Mathias Lang,
• Alexandra Schade and
• Stefan Bräse

Beilstein J. Org. Chem. 2016, 12, 2570–2576, doi:10.3762/bjoc.12.252

• metal-free reaction conditions, high yields and easy purification. Results and Discussion The first network shown here was synthesized by crosslinking the two tetrahedral tetraphenylmethane core structures 1 and 2 via the radical-mediated thiol–yne reaction using AIBN as initiator. The second network

•  1 (Figure S8 and S9, respectively). Conclusion Herein we synthesised amorphous porous tetraphenylmethane-based organic hyper-crosslinked polymers (HCPs) through the thiol–yne reaction. The use of this versatile method reveals advantages such as high yields, cost effectiveness and metal-free

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

• Felicia D’Andrea,
• Giorgio Catelani,
• Lorenzo Guazzelli and
• Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

• material but differs from previous work in that it is metal-free. The first application of this approach was described by Kiely [31][32] who obtained a sample of myo-inositol in a mixture with other non characterised stereoisomers by treating D-xylo-hexos-5-ulose [31] and its 6-phosphate [32] with 0.1 N

Robust C–C bonded porous networks with chemically designed functionalities for improved CO₂ capture from flue gas

• Damien Thirion,
• Joo S. Lee,
• Ercan Özdemir and
• Cafer T. Yavuz

Beilstein J. Org. Chem. 2016, 12, 2274–2279, doi:10.3762/bjoc.12.220

• through metal-free Knoevenagel nitrile–aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m2/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• necessarily require transition metal catalysis as did the EniChem and Ube processes. Instead, the reaction can be effectively catalyzed by a combination of supported basic ammonium resins and homogeneous alkaline bases [60], thereby demonstrating the potential of transition metal-free catalytic systems for

• dependence of the catalytic activity on the structure of IL cations and anions for the synthesis of DMC through the transesterification of EC with methanol [73]. They achieved the best results using a halogen and metal-free IL such as 1,3-dimethylimidazolium-2-carboxylate (DMIM-2-CO2), which was easily

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

• ]. The Baeyer–Villiger oxidation of ketones 76 under the action of oxygen to the related esters 77 was performed using metal-free carbon (Ketjen Black) as a solid catalyst and benzaldehyde as the sacrificing agent. This metal-free carbon catalyst showed excellent catalytic activity and can be recycled

One-pot synthesis of 4′-alkyl-4-cyanobiaryls on the basis of the terephthalonitrile dianion and neutral aromatic nitrile cross-coupling

• Roman Yu. Peshkov,
• Elena V. Panteleeva,
• Wang Chunyan,
• Evgeny V. Tretyakov and
• Vitalij D. Shteingarts

Beilstein J. Org. Chem. 2016, 12, 1577–1584, doi:10.3762/bjoc.12.153

• propose a one-pot method of the transition-metal-free biaryl cross-coupling for the preparation of 4'-alkyl-4-cyanobiaryls as potentially valuable building blocks [3][4][5][6][7][8][9][20][44] with a variable structure of aromatic moieties (biphenylic, m-terphenylic or phenylnaphthylic), as well as an

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• isomerization in the metal-free systems E-2 → E-3 and Z-2 → Z-3 (pathways 2a/2b). This suggests that W(CO)5 or W(CO)4 coordination to E-2 or Z-2 kinetically stabilizes the carbene ligand. All pathways 1a/1b, 2a/2b and 3a/3b have large overall Gibbs free energies of activation with ΔG‡total > 200 kJ mol−1. The

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

• -carbon quaternary center at the pseudo benzylic position has been achieved via a ‘transition-metal-free’ intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon–carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N

• efficient manner. However, despite the associated advantages, these methodologies require one or two metal catalysts for efficient reactions, which are sometimes undesirable [17][18][19][20][21]. Therefore, an alternate strategy to carry out these transformations under 'transition-metal-free' conditions has

• engaged in the development of efficient methodologies for the synthesis of 2-oxindoles with intriguing ring systems. To this end, recently, we have reported a transition-metal-free ‘intramolecular-dehydrogenative-coupling' (IDC) strategy to access such 2-oxindole moieties through a C-alkylation followed

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

• described. A range of electronically diverse acetophenones reacted well with several 2-aminobenzenesulfonamides, affording 3-acylbenzothiadiazine 1,1-dioxides in good yields. Keywords: 3-acylbenzothiadiazine 1,1-dioxides; cyclization; metal-free; oxidation; Introduction Benzothiadiazine 1,1-dioxide

• metal catalysts from pharmaceutical chemicals was cumbersome. Therefore, the development of efficient metal-free routes to benzothiadiazine 1,1-dioxides is necessary. On the other hand, despite that so many benzothiadiazine 1,1-dioxide derivatives have been studied extensively, 3-acylbenzothiadiazine

• -acylbenzothiadiazine 1,1-dioxides from readily available aromatic ketones and 2-aminobenzenesulfonamides. Various aryl and heteroaryl ketones reacted well with 2-aminobenzenesulfonamides, affording the corresponding products in moderate to good yields. This metal-free method would provide opportunities to develop new

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

• have organized this review by the catalyst used, with free carbenes first, followed by Cu, Rh, Au, Pt, and then W-catalyzed reactions. Review Metal-free reactions While transition metal catalysis has seen widespread adoption for carbene and nitrene reactions, it is not necessary for a controlled

• reaction in all cases. Chatterjee reported an early example of building bridged-polycyclic intermediates using metal-free carbenes in 1979 (Scheme 2) [20]. Exposing the tosylhydrazone 13 to base and heat generated an alkyl carbene that inserted into the C–H bond of an adjacent ring. Surprisingly, the

Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

• Mamoru Tobisu,
• Takuya Igarashi and
• Naoto Chatani

Beilstein J. Org. Chem. 2016, 12, 654–661, doi:10.3762/bjoc.12.65

• borylation catalysts. We also reported the first use of a Pt catalyst that enables C–H borylation of simple hindered arenes such as mesitylene [10][11]. Metal-free C–H borylation has also been reported [12]. Ligand modification has been used to control the regioselectivity of C–H borylation reactions; for

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• alkanes resulting in alkyl-substituted oxindoles (Scheme 1a) [43]. However, cyclization of N-allylbenzamides initiated by the functionalization of sp3 C–H bonds of simple alkanes remains unexplored. Very recently, our group developed a metal-free hydroxyalkylation-initiated radical six-membered

• substrate, the cyclization reaction proceeded smoothly (Scheme 1c). Herein, we report a metal-free cascade 1,2-alkyarylation of substituted N-allylbenzamides with alkanes affording 4-alkyl-substituted dihydroisoquinoline-1(2H)-ones as the product. Results and Discussion Initially, we selected N-methyl-N-(2

• . Intermediate C proceeds through intramolecular cyclization to give intermediate D. Finally, H-atom abstraction occurs between D and TBPB directly, which gives the product 5aa and regenerates radical A for the next cycle. Conclusion In summary, a metal-free cascade functionalization of unactivated C(sp3)–H

Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

• Brett N. Hemric and
• Qiu Wang

Beilstein J. Org. Chem. 2016, 12, 22–28, doi:10.3762/bjoc.12.4

• -oxazolidinone motifs (Scheme 1D) [16]. Metal-free intermolecular oxyamination reactions have also been accomplished; examples were reported by the Zhu lab with the use of peroxides [17] and by the Studer lab with the use of hypervalent iodo-azide reagents [18]. Furthermore, the intramolecular oxyamination of

Convenient preparation of high molecular weight poly(dimethylsiloxane) using thermally latent NHC-catalysis: a structure-activity correlation

• Stefan Naumann,
• Johannes Klein,
• Dongren Wang and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 2261–2266, doi:10.3762/bjoc.11.246

• ]. Likewise, poly(siloxane)s are attractive and versatile macromolecular materials produced on large scale and thus a rewarding field for the development of new catalysts, the more so if the added benefit of metal-free conditions can be implemented [19][20][21]. In spite of this, few investigations regarding

• -handle metal-free process which is more competitive in comparison with other catalytic systems can be realized [26]. Results and Discussion Several five-, six- and seven-membered NHCs were prepared and reacted with carbon dioxide to receive the corresponding CO2 adducts (Scheme 1, top), following

• near quantitative conversion. Hence, with this catalytic setup it is possible to form one-component, metal-free mixtures which can be activated by mild heating. Polymerization of D4 is entropically driven [21][34] and thus profits from elevated temperature in any case, rendering the implementation of

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

• practical application of these metal-free methods. The application of copper catalysts was found as effective solution to some of these problems. For example, Wu et al. [70] reported the efficient synthesis of α-iodoketals 76 and 77 via CuO-mediated selective mono-iodination of diketones 74 and

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

• Gleb Sorohhov,
• Chenyi Yi,
• Michael Grätzel,
• Silvio Decurtins and
• Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

• ]. Although devices with the most commonly used dyes based on polypyridyl transition-metal complexes show excellent photovoltaic performances with high power conversion efficiencies of over 11% [4], metal-free organic dyes have significant advantages in several aspects. These comprise for example large molar

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

Metal-free one-pot synthesis of 2-substituted and 2,3-disubstituted morpholines from aziridines

• Hongnan Sun,
• Binbin Huang,
• Run Lin,
• Chao Yang and
• Wujiong Xia

Beilstein J. Org. Chem. 2015, 11, 524–529, doi:10.3762/bjoc.11.59

• Hongnan Sun Binbin Huang Run Lin Chao Yang Wujiong Xia State Key Laboratory of Urban Water Resource and Environment, the Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, P. R. China 10.3762/bjoc.11.59 Abstract The metal-free synthesis of 2

• : ammonium persulfate; aziridine; metal free; morpholine; Introduction Morpholines are common structural cores of a broad range of biological and pharmacological natural or synthetically important organic molecules [1]. In particular, a number of 2-substituted and 2,3-disubstituted morpholines are

• haloalkoxy amine intermediate 2a after abstraction of one hydrogen atom from alcohol. Finally, an intramolecular ring closure affords the morpholine product 3a in the presence of KOH [21]. Conclusion In conclusion, we have developed a simple and practicable metal-free protocol for the synthesis of 2

Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)

• Friederike Danneberg,
• Alice Ghidini,
• Plamena Dogandzhiyski,
• Elisabeth Kalden,
• Roger Strömberg and
• Michael W. Göbel

Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55

• experiments [7]. PNA conjugates of both metal-containing and metal-free RNA cleavers have been effectively used as artificial nucleases towards different substrates [8][9][10][11]. Most notable is a copper-based PNAzyme which cleaves RNA site-specifically with substrate half-lifes as low as 30 minutes [12]. A

• PNA-10mer attached to diethylenetriamine showed a higher cleavage activity [13] when compared to the corresponding 22mer DNA conjugate [14]. We therefore decided to investigate the activity of tris(2-aminobenzimidazole) [15] – a metal-free ribonuclease developed by us formerly – as a conjugate with

• [18]. The reaction proceeds at ambient temperature. In contrast to ureas and thioureas formed as byproducts when using carbodiimides, the N-methylpyridine-2(1H)-thione resulting from Mukaiyama's reagent is soluble and can be easily removed by chromatography. As we were searching for a heavy metal-free

Eosin Y-catalyzed visible-light-mediated aerobic oxidative cyclization of N,N-dimethylanilines with maleimides

• Zhongwei Liang,
• Song Xu,
• Wenyan Tian and
• Ronghua Zhang

Beilstein J. Org. Chem. 2015, 11, 425–430, doi:10.3762/bjoc.11.48

• as a photocatalyst has been developed. The metal-free protocol involves aerobic oxidative cyclization via sp3 C–H bond functionalization process to afford good yields in a one-pot procedure under mild conditions. Keywords: aerobic oxidative cyclization; C–H functionalization; Eosin Y; photoredox

• and not sustainable. Similar to the redox properties of these organometallic complexes, some metal-free organic dyes such as Eosin Y, Rose Bengal, Fluorescein, and Methylene Blue, have shown superiority of their applications as photocatalysts, which are easy to handle, environmentally friendly

• light (two 9 W blue LEDs) at room temperature. Gratifyingly, the desired product tetrahydroquinoline 3a was obtained in 82% yield after 18 h (Table 1, entry 1). We screened a number of metal-free organic dyes for photocatalysts. Of the dyes screened, Eosin Y showed the highest efficiency (Table 1, entry

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• -isocyanobiphenyls with CF3SiMe3 under metal-free conditions showed to be a mild and efficient approach to 6-(trifluoromethyl)phenanthridines, characterised by good yields with high regioselectivity at ambient temperature (Scheme 6) [19][20]. Another radical-based route (targeting 6-perfluoroalkylphenanthridines

• . Trying to omit the expensive metal catalysts, several successful attempts of a transition metal-free approach for phenanthridine synthesis were reported. For instance application of a simple diol combined with KOt-Bu resulted in intramolecular C–H arylation to give the respective phenanthridine

Copper-promoted hydration and annulation of 2-fluorophenylacetylene derivatives: from alkynes to benzo[b]furans and benzo[b]thiophenes

• Yibiao Li,
• Liang Cheng,
• Xiaohang Liu,
• Bin Li and
• Ning Sun

Beilstein J. Org. Chem. 2014, 10, 2886–2891, doi:10.3762/bjoc.10.305

• metal-free process for the synthesis of benzo[b]furans from 2-fluorophenylacetylene derivatives. But the reaction requires conditions with a high reaction temperature for satisfactory yields. Unfortunately, only benzo[b]furans were obtained in this reaction [30]. Typically, the aryl halides used in the