Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• above); however, with lower yield (Scheme 3). Interestingly, to the best of our knowledge, there is only one report in the literature about the explicit use of NaBF4 as fluorinating reagent for boronic acids [54], and we have not investigated the general applicability of this reaction so far

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

• ligands based on the same chiral scaffold. It was concluded that free hydroxy groups on the lower rim of the calixarene ligands do not have a beneficial catalytic effect due to the formation of hydrogen bonds with the incoming boronic acids. In the same study, diphosphine ligand (S,S)-29 was used in the

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• , alkyl or alkenyl group via Suzuki coupling reaction with boronic acids to give otherwise rarely available 1,4,5-trisubstituted pyrazoles [119]. The second limitation is that the CuSAC reaction proceeds only with terminal alkynes. The latter fact clearly indicates some kind of participation of the

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

• ), which ends up on the pyridinone ring. As alternative, a Suzuki–Miyaura coupling between 3-halogenoindoles and (2-methoxypyridyl)boronic acids followed by a deprotection of the methoxy group [7][8] or transition-metal-catalyzed annulation methods [9] have also been reported. In contrast, several

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• modular synthesis of carbocyclic C-nucleosides [53]. The boronic acids/boronates (inset, Figure 13) of several (hetero)aryls were conducive to Suzuki coupling with the best result obtained when the C2', C3' and C5'–OHs were protected with TIPS and pivaloyl groups, respectively [53]. The cross-coupling

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• antitumour agents [10]. Advantages of the Suzuki–Miyaura coupling are mild reaction conditions, commercial availability of a large number of boronic acids and simple product purification [7]. Concerning the transition metal source for C–C cross-coupling reactions, homogeneous and heterogeneous Pd catalysts

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• corresponding N1-alkyl-3-iodopyrazolo[3,4-d]pyrimidine derivatives 225. The iodinated pyrazolo[3,4-d]pyrimidines were alkylated at C3 with boronic acids (R2-B(OH)2) using Suzuki coupling conditions to give 4-amino-N1,C3-dialkylpyrazolo[3,4-d]pyrimidines 226 (Scheme 61). Synthesis of pyrazolo[3,4-b]pyrazines

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• acids [29][30]. In 2012, the group of Gooßen [31] designed a new protocol replacing the boronic acids with the corresponding pinacol esters to minimize side reaction (Scheme 16). This reaction proceeded smoothly to form the corresponding analogues in moderate to high yields using the shelf-stable, and

• accomplished under base-free conditions by using Togni’s reagent 1f as the trifluoromethylation reagent at room temperature. Organotrifluoroborates were attractive alternatives to boronic acids for its superior characteristic, such as ease of handling, storability, and robustness under harsh reaction

• merger of photoredox and Cu catalysis (Scheme 21). In this protocol, the CF3 radical was generated by visible light photoredox, then Cu aryl species were generated through Cu catalysis. Aromatic boronic acids bearing either electron-donating or electron-withdrawing substituents underwent

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• oxidant. The substrate scope was evaluated on 24 aryl and heteroaryl boronic acids. The process was compatible with various functional groups. Arenes bearing electron-donating groups reacted in excellent yields under the CuCl-mediated conditions. However, arenes with electron-withdrawing substituents

• , Molander, Rombouts and co-workers simply applied the reaction conditions described by Sanford for boronic acids to a series of unsaturated potassium organotrifluoroborates (Scheme 55) [80]. In the case of aryl- and heteroaryltrifluoroborates, electron-rich substrates were efficiently trifluoromethylated

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

• of their low reactivity. Recently, Li and Su with co-workers have developed a liquid-assisted grinding (LAG) method for the Suzuki–Miyaura coupling between aryl chlorides and boronic acids to synthesize the biaryls in nearly quantitative yield. Under optimized conditions 2 mol % Pd(OAc)2 and 4 mol

• triazole moiety (Scheme 37a) using benzyl halides, sodium azide and a terminal alkyne via an alumina-supported copper catalyst. Using 10 mol % of Cu/Al2O3, differently substituted phenyl acetylenes and aliphatic alkynes led to 70–96% yield of triazoles [152]. Phenyl boronic acids were also used to

Development of a method for the synthesis of 2,4,5-trisubstituted oxazoles composed of carboxylic acid, amino acid, and boronic acid

• Kohei Yamada,
• Naoto Kamimura and
• Munetaka Kunishima

Beilstein J. Org. Chem. 2017, 13, 1478–1485, doi:10.3762/bjoc.13.146

• one-pot oxazole synthesis/Suzuki–Miyaura coupling sequence has been developed. One-pot formation of 5-(triazinyloxy)oxazoles using carboxylic acids, amino acids and a dehydrative condensing reagent, DMT-MM, followed by Ni-catalyzed Suzuki–Miyaura coupling with boronic acids provided the corresponding

• )oxazole would provide trisubstituted oxazoles (Scheme 1b). Since many kinds of carboxylic acids, amino acids and boronic acids, which are corresponding to 2-, 4-, and 5-substituents of the oxazole, respectively, are commercially available, this method is suitable for the synthesis of a diverse variety of

• reaction conditions). A number of trisubstituted oxazoles were synthesized using 5-(triazinyloxy)oxazoles 3 and various boronic acids 4 (Table 3). To our disappointment, the reaction of 3aa with the arylboronic acid possessing an electron-withdrawing group 4b decreased the yield of 5aab (25%, Table 3

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• reactants such as amines, alcohols or aldehydes led to a wide range of products as reported in Scheme 17. Ley's group developed several continuous-flow approaches for generating diazo species from hydrazones [84][85]. Under flow conditions, diazo compounds were reacted with boronic acids in order to

• generate reactive allylic and benzylic boronic acids further employed for iterative C–C bond forming reactions [86]. The generation of unstable diazo species was possible using a cheap, recyclable and less toxic oxidant, MnO2. The flow stream was accurately monitored by in-line FTIR spectroscopy in order

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

• Yi Lai,
• Zhijian Zong,
• Yujie Tang,
• Weimin Mo,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen,
• Liqun Jin,
• Wen-hua Sun and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 213–221, doi:10.3762/bjoc.13.24

• , entries 13). Different arylboronic acids were also examined to react with 4-chloroacetophenone in this system. No matter what kind of boronic acids were used: electron-deficient (Table 4, entry 14), electron-rich (Table 4, entries 15 and 16) or sterically hindered (Table 4, entry 17) arylboronic acids

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

• were tolerated and yielded the desired product in 80% yield (3f). Aromatic boronic acids possessing both electron-withdrawing and electron-donating substituents were evaluated under our reaction conditions and all resulted in good yields. While aromatic boronic acids substituted with electron

• -withdrawing groups (e.g., acyl, F or CF3) were likewise tolerated well (3g–j). Aromatic boronic acids substituted with electron-donating groups resulted in the formation of the corresponding arylated products with higher yields (3k–n). Enantioselective arylation reaction Subsequently, we explored the

Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs

• Arne Klinkebiel,
• Ole Beyer,
• Barbara Malawko and
• Ulrich Lüning

Beilstein J. Org. Chem. 2016, 12, 2267–2273, doi:10.3762/bjoc.12.219

• the Suzuki–Miyaura coupling [11]. A retrosynthetic analysis (Figure 3) of extended mono-functionalized triazinetricarboxylic acids 2 calls for tris(4-bromoaryl)-1,3,5-triazines 3 and boronic acids 4 with an additional carboxylic acid functionality. The respective methyl carboxylate of boronic acid 4

• 5c. The resulting triazines 3b and 3c can then be coupled to boronic acids or boronates to give substituted and elongated triazine-based linkers. Furthermore, the reduction of the nitro group or cleavage of the methoxy group will give additional substituted linkers, amino and hydroxy-substituted ones

• boronic acids 4. Synthesis of unsymmetrically substituted 2,4,6-tris(bromoaryl)-1,3,5-triazines 3 from one equivalent of a substituted benzoyl chloride 5 and two equivalents of benzonitrile 6. As intermediates, oxadiazinium salts 7 are formed. The reaction with ammonia yields the desired triazines 3

Rapid regio- and multi-coupling reactivity of 2,3-dibromobenzofurans with atom-economic triarylbismuths under palladium catalysis

• Maddali L. N. Rao,
• Jalindar B. Talode and
• Venneti N. Murty

Beilstein J. Org. Chem. 2016, 12, 2065–2076, doi:10.3762/bjoc.12.195

• stage that in comparison to similar cross-couplings carried out with aryl boronic acids [29], the present method with triarylbismuth reagents showed appreciable reactivity with threefold coupling advantage and extended substrate scope. The overall resulted regio- and chemo-selective couplings encouraged

Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

• Carl J. Mallia,
• Paul M. Burton,
• Alexander M. R. Smith,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1598–1607, doi:10.3762/bjoc.12.156

• for C(aryl)–N and C(aryl)–O coupling reactions. Their methods made use of stoichiometric amounts of copper(II) acetate as the catalyst and boronic acids as the aryl donors. In the presence of a base, the coupling could be performed at room temperature. These reactions were subsequently shown to work

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

• , whereupon it reacts with another equivalent of arylurea (Scheme 17) [231]. Similarly, BQ’s role in C–H coupling of boronic acids would likely be to oxidize Pd(0) to Pd(II) after the product forming step (Scheme 18). Transmetallation between the palladacycle and arylboronic acid followed by reductive

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction

• Dariusz Błachut,
• Joanna Szawkało and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82

• construction of unsymmetrically arylated pyrroles, thiophenes and 2,6- and 3,5-diarylpyridines. In order to test the utility of the above mentioned approach, a series of trial cross couplings were performed on a microscale according to route 3 with a variety of electron-poor and electron-rich boronic acids

• (Table 2). The steric hindrance introduced by ortho-substituted boronic acids was also investigated. In order to check how the electronic and steric factors affect the distribution of homo- and heteroarylated products, various combinations of arylboronic acids (32–41) were applied as partners for the

• coupling of 3,5-, 2,6-dibromopyridines and dibromobenzenes with various arylboronic partners of different electronic properties. We then investigated a one-pot, double cross-coupling strategy with mixtures of more sterically demanding boronic acids containing ortho-substituents. The cross coupling of 1

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

• lower than that of the corresponding boronic acids. Because of this lower reactivity, several transformations require deprotection of a pinacol ester under oxidative conditions (e.g., NaIO4) [16]. Hartwig reported that the Ir/dtbpy system is also able to introduce more reactive neopentyl and hexylene

Copper-mediated arylation with arylboronic acids: Facile and modular synthesis of triarylmethanes

• H. Surya Prakash Rao and
• A. Veera Bhadra Rao

Beilstein J. Org. Chem. 2016, 12, 496–504, doi:10.3762/bjoc.12.49

• . Recently, we reported a copper-catalyzed C–C bond formation by substitution of the labile C(4)SMe group in 4H-chromenes or C(3)–OH in isoindolinones with aryl/alkenyl groups by employing the corresponding boronic acids [51][52]. Continuing these efforts, we designed a copper-catalyzed synthesis of a

• further step with a variety of aryl boronic acids), it should be possible to provide a unique opportunity for the modular synthesis of unsymmetrical triarylmethanes. If successful, the method could provide an opportunity for the synthesis of a combinatorial library of the coveted molecules. Herein, we

• towards electronic effects, the copper-mediated cross-coupling reaction is not very sensitive to steric crowding in the neighborhood of the reaction center. Next, we employed heteroaromatic boronic acids, such as furan-2-ylboronic acid (10i; Table 2, entry 8), thiophen-2-ylboronic acid (10j; Table 2

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• Prize in 2013 and I was recently rewarded for developing networks with China with an Inaugural CASE Prize in 2015. Keywords: boronic acids; fluorescence; glucose sensor; self and directed assembly; supramolecular; Review Beginnings When at school I became distracted very easily and while this may not

Art, auto-mechanics, and supramolecular chemistry. A merging of hobbies and career

• Eric V. Anslyn

Beilstein J. Org. Chem. 2016, 12, 362–376, doi:10.3762/bjoc.12.40

• 1992, and looking back at the polyol receptors (such as 3) shows how far this field progressed. The use of boronic acids of Shinkai/James (7) [43][44][45] and the large cavities reported by Davis (8) [46] for binding saccharides has advanced the field far beyond our primitive designs (Figure 6). The

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• , Aβ peptide pentapeptide boronic acids 1 and 2 were synthesized by solid-phase peptide synthesis and studied in esterification experiments with polyhydroxylated templates. The bis-hydroxylated dipeptide Hot=Tap serves as a template of adjustable degree of oligomerization which spontaneously forms

• avoided only when two different reactive groups are employed; that is why the reversible esterification between boronic acids and diols appeared an attractive solution to us. In a first approach, we planned to condense short peptide boronic acids with polyol templates for the assembly of an Aβ-dimer. The

• -terminal boronic acid 2. Peptide boronic acids of type 1 were synthesized on polymer-bound diethanolamine (PS-DEAM resin), according to the protocol in Supporting Information File 1, Figure S1 [21]. The electron-poor boronic acid 2, which was expected to be more reactive in boronic ester formation, was

Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities

• Carmen Mejuto,
• Beatriz Royo,
• Gregorio Guisado-Barrios and
• Eduardo Peris

Beilstein J. Org. Chem. 2015, 11, 2584–2590, doi:10.3762/bjoc.11.278

• 2 is lower than that shown by complex 6, both in terms of conversion and selectivity. For all reactions carried out in the presence of catalyst 2, deborylation of the boronic acids took place. This side reaction explains the differences found between conversions and yields for all reactions