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

• preservance of the sensitive aldehyde group in the product structure, which can act as a precursor for the synthesis of some new motifs (Scheme 29) [117]. The reaction was carried out between 2-APs 3 and cinnamaldehyde derivatives 88 under aerobic conditions. ZnCl2 and pyridine act as additives, where ZnCl2

Mechanochemical Friedel–Crafts acylations

• Mateja Đud,
• Anamarija Briš,
• Iva Jušinski,
• Davor Gracin and
• Davor Margetić

Beilstein J. Org. Chem. 2019, 15, 1313–1320, doi:10.3762/bjoc.15.130

• grinding additives to improve mass transfer and prevent pasting of the reaction mixture [26][27][28] (Table 1, entries 5–8) was detrimental to reaction yields. The addition of a small amount of solvents which was reported to facilitate several ball milling reactions (liquid assisted grinding, LAG) [29][30

Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

• Maryam Khalesi,
• Azim Ziyaei Halimehjani and
• Jürgen Martens

Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

• by acid catalysis from renewable resources, such as sugars, lignocellulosic biomass and waste materials [18]. It can be used as a bifunctional precursor for the synthesis of pharmaceuticals, plasticizers, and different additives [19]. Furthermore, it is recognized as an excellent starting material

An improved synthesis of adefovir and related analogues

• David J. Jones,
• Eileen M. O’Leary and
• Timothy P. O’Sullivan

Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

• significantly lower conversion to 6 than when tosylate 5 was employed. Optimisation of other aspects of this reaction (e.g., choice of base, solvent, temperature and the role of additives) has already been investigated by Brown Ripin [37][40] and Riley [38] which suggested that further investigation had limited

Catalyst-free assembly of giant tris(heteroaryl)methanes: synthesis of novel pharmacophoric triads and model sterically crowded tris(heteroaryl/aryl)methyl cation salts

• Rodrigo Abonia,
• Luisa F. Gutiérrez,
• Braulio Insuasty,
• Jairo Quiroga,
• Kenneth K. Laali,
• Chunqing Zhao,
• Gabriela L. Borosky,
• Samantha M. Horwitz and
• Scott D. Bunge

Beilstein J. Org. Chem. 2019, 15, 642–654, doi:10.3762/bjoc.15.60

• State University, Kent, OH 44242, USA 10.3762/bjoc.15.60 Abstract A series of giant tris(heteroaryl)methanes are easily assembled by one-pot three-component synthesis by simple reflux in ethanol without catalyst or additives. Diversely substituted indoles (Ar1) react with quinoline aldehydes, quinolone

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• in water including the development of specially designed water-soluble catalysts [21][22][23][24][25][26][27][28], addition of organic solvents [29][30][31], or use of additives such as for example calixarenes or cyclodextrins [32][33], chloride salts [34], vitamin E-based amphiphiles [35

• structure of the tailored catalysts and thus difficulties associated with their synthesis, or the need to use additives or co-solvents to improve the solubility of reacting species, still remain. Therefore, further development of catalytic systems would provide a complimentary extension to the scope of this

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

• additives [11], alkylating reagent in the Friedel–Crafts synthesis of indanones [12] or as synthon toward the introduction of cyclopropyl moieties in compounds with medicinal or biological interest [13][14]. In view of the lack of examples of direct conversions of ethylene into cyclopropanecarboxylates, and

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• only in stationary low concentrations. In the past, we used electron mediators as additives (triethylamine) [19][26] or peptides with substrate-binding sites [31][32] to overcome this problem. For the current work, we propose a radical ion pair in a solvent cage that undergoes an extremely fast proton

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

• (Scheme 11). More recently, Olivier-Bourbigou and Mauduit demonstrated the ability of unsymmetrical N-cycloalkyl Ru–indenylidene catalysts for the selective self metathesis of linear α-olefins to longer internal linear olefins in the absence of additives to prevent isomerization [35]. Catalyst 91 with a

• [55] (Table 6). The size of the ring formed was found to have a crucial influence on the enantioselectivity of the reaction with the enantiomeric excesses decreasing when passing from five to six and seven-membered rings (Table 6, entries 1, 4 and 7). The use of halide additives such as NaBr and NaI

• employment of halide additives had always a beneficial effect on the enantioselectivity [55]. The product ring size dependence observed in the desymmetrization of 166, 168 and 170 with 164 was explained considering that an NHC rotation is possible during the catalytic cycle and that 166, 168 and 170 should

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• excited state energy and redox potentials to interact with additives [13]. Parallel to this, the environmental issues impose the use of new polymerization methods that are safer for the manipulator, contribute to lower the amount of released volatile organic compounds and can reduce the energy consumption

• absorbing compound and suitable additives under light to induce a catalytical cycle. As light is an inexhaustible and renewable energy, photochemistry has dealt a great interest into organic chemistry and green chemistry since the early 20th century [15]. By absorbing light, the compound reaches an

• and redox reactions are possible. This process is called photoinduced electron transfer (PET). In this context, photoredox catalysis was developed. Light is used to excite the photoredox catalyst which allows electron transfer processes with additives. Both oxidation and reduction reactions can be

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

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

• incorporation ratio (94%) at the β-position. Although Zn(OAc)2 and Et4NI were not indispensable for the reaction to proceed, these two additives caused an increased product yield. In contrast, the reaction did not occur in the absence of the catalyst. The use of the dppf ligand also proved to be essential

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

• Ken Tamamoto,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213

• , entry 3). Catalyst optimization (Table 2, entries 4–6) showed that Cu2O led to the highest product yield (46%, Table 2, entry 6) [37]. After further exploring the reaction conditions (Table 2, entries 7–13) including catalyst loading, equivalents of 3a, additives, and reaction temperature, the best

• ). To further improve the reaction efficiency, three different additives (TMEDA, phen, and 2,2’-bipyridyl (bpy)) were tested. The first two additives were found to be ineffective for the present reaction (Table 3, entries 5 and 6), whereas bpy led to the quantitative formation of 6a (Table 3, entry 7

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

• desired alkene 10 and regenerates the active cobalt catalyst for the next cycle. In 2015, Petit’s group developed a hydroarylation reaction of internal alkynes with imines using a low-valent cobalt catalyst without reductant or additives (Scheme 10) [52]. The reaction afforded alkenes 13 in excellent

• catalytic systems. Similarly, imines 9 were employed for the hydroarylation reaction to form linear or branched addition products by tuning ligands and additives. Thus, the reaction of imines 9 with vinylsilanes as well as alkyl alkenes gave linear addition products 27a,b under mild reaction conditions

Bi-mediated allylation of aldehydes in [bmim][Br]: a mechanistic investigation

• Mrunesh Koli,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2018, 14, 2198–2203, doi:10.3762/bjoc.14.193

• activators (chemical additives and ultrasonication) for the Bi-mediated allylation of benzaldehyde (1a), as the model substrate with commercially available and inexpensive allyl bromide (Scheme 1) at room temperature (25 °C) [39][40][41][42]. The results are shown in Table 1. As reported earlier [30], the

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• stimuli such as acids/bases, ions, additives, or solvent changes [14]. However, the latter class of stimuli bears the disadvantage to produce chemical “waste” which creates the challenging task to constantly add and remove material to and from the system, if a repetitive operation is desired. Therefore, a

• electrically operated without the need of chemical additives, if conducting solid supports are used. This also opens pathways towards the integration of switchable AMMs into the world of silicon-based chips and electronic circuits. A landmark in the field of molecular-scale electronic devices is the rotaxane

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

• in the catalytic cycle, which itself can be classed either as reductively or oxidatively quenched. Net redox neutral processes see the substrate remain at the same oxidation state overall. These transformations are generally more complex, and the additives required as well as their mode of action

• vary in each case. 1.5 Scope, aim and selection criteria for presented publications Unless otherwise stated, control experiments were completed to prove the necessity of the light source, photocatalyst and all additives in the reported reactions. In addition, unless otherwise stated, optimisation of

Functionalization of graphene: does the organic chemistry matter?

• Artur Kasprzak,
• Agnieszka Zuchowska and
• Magdalena Poplawska

Beilstein J. Org. Chem. 2018, 14, 2018–2026, doi:10.3762/bjoc.14.177

• conjugation protocols do not uphold with the basic organic chemistry principles discussed above. Despite the interesting applications presented in these studies, important questions remain regarding the structure of the obtained materials. One common inaccuracy is a lack of the additives in the conjugation

Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• , Figure 6; CCDC 1834012, Figure 7). Conclusion We have developed a facile synthesis of pyrimido[1,6-a]quinoxaline derivatives via the intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases. The reaction proceeds under solvent-free conditions without any additives and

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

• cyanotrifluoromethylation reaction. The mechanistic study of the oxy-trifluoromethylation of phenylacetylene has then led to demonstrate that the reaction is accelerated in the presence of additives such as B2pin2 [35]. A mechanism involving an initial step of transmetallation of B2pin2 with the Cu(I) catalyst was proposed

• than its O-tautomer 88, the rearrangement step seems to be much faster. The use of the radical scavenger TEMPO had no effect on the reaction outcome suggesting that the initial hypothesis is correct. By screening additives, it was shown that the hypervalent iodine could be quickly generated in situ by

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• analogue 68 bearing the same bifunctional pattern was also prepared from p-tert-butylphenol and used for comparison (Scheme 19). When monomeric analog 68 was used as a catalyst alone or in the presence of p-tert-butylphenol/phenol as acidic additives, lower yield and enantioselectivity were observed. These

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

• partner) are taken into account. Other additives, such as additional bases, acids or catalysts were neglected. Review 1. Diaryliodonium salts 1.1. Acyclic diaryliodonium salts Acyclic diaryliodonium salts 1 find widespread application in numerous metal-free and transition metal-mediated electrophilic

Hypervalent iodine-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• (see Supporting Information File 1, Table S1). Upon optimization with various oxidants and additives screened, it was found that a Lewis acid additive can promote the olefin heterofunctionalization via a Ritter-type amidation using acetonitrile as both the solvent and the amine source. Interestingly

Electrochemically modified Corey–Fuchs reaction for the synthesis of arylalkynes. The case of 2-(2,2-dibromovinyl)naphthalene

• Fabiana Pandolfi,
• Isabella Chiarotto and
• Marta Feroci

Beilstein J. Org. Chem. 2018, 14, 891–899, doi:10.3762/bjoc.14.76

• (Scheme 9). Conclusion The electrochemical methodology is shown to be a useful tool in organic synthesis. The possibility to direct the reaction towards different products simply by changing the electrolysis parameters (potential, solvent, supporting electrolyte, amount of charge, additives, etc.) and

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

• replacing TEA by 1,4-diazabicyclo[2.2.2]octane (DABCO) (Table 1, entry 11). Besides, other organic or inorganic bases gave poor results (Table 1, entries 12–18). Next, the additives were investigated in the coupling reactions (Figure 1, see detailed results in Supporting Information File 1, Table S1

• , TBAI or tetrabutylammonium chloride (TBAC) did not provide a satisfactory result (Table S1, entries 3 and 4). It was interesting to find that using bromide salts (LiBr, NaBr, KBr and TBAB) as additives, not only the conversion rate of 1a was increased, but also the side-product 4a was suppressed

• protocol was conducted in a total mechanosynthesis of axitinib in short reaction time and high efficiency. With this system, we hope to expand the pharmaceutical synthetic toolbox in mechanochemistry. Investigation of additives in the Heck reaction: 1a (1.5 mmol), 2a (2.25 mmol), Pd(OAc)2 (5 mol %), PPh3