Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• attributed to the increased Brønsted acidity when the strong electron-withdrawing trifluoromethyl group was placed on the benzene ring of the arylboronic acid. Removing the boronic acid from the reaction system leads to a dramatic decrease in both yield and enantiocontrol (Table 1, entry 16). The challenge

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• reagent was involved in several cross-coupling processes, including copper chemistry. In this context, in 2015, the group of Rueping reported an oxidative trifluoromethylselenolation process of terminal alkynes and boronic acid derivatives (Scheme 10) [27]. Using a stoichiometric amount of copper/ligand

• alkynes. The latter was also a key intermediate for the formation of α-trifluoromethylselenylated vinylsulfone. It is worth noting that the strategy for the trifluoromethylselenolation of boronic acid developed in our laboratory was applied in 2019 for the synthesis of the selenylated analog 30 of

• Pretomanid, an antituberculosis drug (Scheme 14) [38]. The key step was the trifluoromethylselenolation of boronic acid 26 under standard conditions (Scheme 13), followed by a mesylation and a reaction with the commercially available alcohol 29 to yield the desired compound 30. Preliminary results indicated

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• homoallylic alcohol derivatives [12][13][14]. Results and Discussion Specifically, the three-component allylic cross-coupling reaction of benzaldehyde (1a, 0.4 mmol), tert-butyl cinnamyl carbonate (2a, 0.2 mmol) and (dimethylphenylsilyl)boronic acid pinacol ester [PhMe2SiB(pin)] (0.4 mmol) occurred in the

An improved, scalable synthesis of Notum inhibitor LP-922056 using 1-chloro-1,2-benziodoxol-3-one as a superior electrophilic chlorinating agent

• Nicky J. Willis,
• Elliott D. Bayle,
• George Papageorgiou,
• David Steadman,
• Benjamin N. Atkinson,
• William Mahy and
• Paul V. Fish

Beilstein J. Org. Chem. 2019, 15, 2790–2797, doi:10.3762/bjoc.15.271

• efficient step in our sequence and justified further optimisation (vide infra). Suzuki–Miyaura cross coupling of bromide 5 with cyclopropylboronic acid (2.5 equiv) produced 6 in good yield (62–89%) but the product required extensive chromatographic purification. We reasoned that switching from the boronic

• acid (c-PrB(OH)2) to the corresponding MIDA-boronate 11 would improve the quality of the reagent and slow release of the active boron species during the course of the reaction would allow us to reduce the number of molar equivalents required to improve conversion [16]. Palladium-mediated cross coupling

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• which was purged with nitrogen, and cooled to 0 °C. Biphenyl-4-boronic acid (0.89 g, 4.5 mmol) was added, followed by 2-bromobiphenyl (0.50 g, 2.2 mmol), DMF (11.5 mL) and Pd(PPh3)4 (0.13 g, 0.1 mmol). The reaction mixture was stirred at 0 °C for 5 h. NaOH (1 M, 10 mL) was added and the product was

• –7.40 (m, 8H), 7.35–7.29 (m, 1H), 7.26–7.17 (m, 7H). Suzuki–Miyaura coupling to form o,m’-Quaterphenyl (16) [35]: 2-Bromobiphenyl (0.20 g, 0.80 mmol), biphenyl-3-boronic acid (0.25 g, 1.3 mmol), and Pd(PPh3)4 (0.02 g, 0.02 mmol) were dissolved in DMF (10 mL). The reaction mixture was cooled to 0 °C and

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range

• electron-transfer phenomena or two-photon absorption [32][33][34][35][36]. As part of our research program we have developed arylisoquinolines that integrate a boronic acid ester [37][38][39] or a BMes2 unit [6][40]. The presence of the boron-substituent confers interesting photophysical properties to

• dye 18 is insensitive to oxygen and was tentatively attributed to the formation of a pyrene-based radical cation, resulting from photoionization [46]. Interaction with fluoride anions The presence of the boronic acid ester moiety does not only contribute to significant changes in the fluorescence

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• (Scheme 3, Table 1). Triflate 21 was obtained without further purification from 12 by addition of triflic anhydride in dry acetonitrile. Boroxine 18b was formed by heating of boronic acid (18a) at 110 °C because it was shown by Calitree and Detty that free boronic acid leads to the destruction of the

• internal salt (protonated pyridine ring and deprotonated boronic acid) and ensuing difficult formation of boroxine 29b (Table 2, entry 10). Switching to the neutral heterocyclic boronic acid 30a, the corresponding thienyl-substituted silicon rhodamine 30c could be obtained in 37% (56% brsm) yield with the

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• , AsOTh2, and SyOTh2 (Figure 1) were obtained using a standard procedure for a Suzuki–Miyaura coupling of iodides 4, 5, 7, and 8 with boronic acid esters 9 and 12 (see Scheme 3). Throughout the text, abbreviations “As” and “Sy” denote asymmetric and symmetric substitution patterns, respectively; “O

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• , promoting the C–F over C–O bond formation via an inner-sphere pathway. Fluorination of arenes, aryl bromides, -alcohols, -triflates, and -boronic acid derivatives: In 2013, Larhed and co-workers [51] established a one-pot, two-step fluorination of aryl alcohols via aryl nonafluorobutylsulfonates. This

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• followed by stirring for 1 h at −10 °C on ice-salt bath under argon gas atmosphere. Then, 0.96 mL (3.58 mmol, 1.5 equiv) of B(OBu)3 was added and the temperature of the mixture was allowed to warm to room temperature and stirred for 1 h. After ascertaining the formation of boronic acid by TLC, 5 mL of H2O

• was added, and solvent was removed in vacuo. To a 200 mL three necked flask, the boronic acid, 0.90 g (6.51 mmol, 2.7 equiv) of K2CO3, 0.72 g (2.37 mmol, 1.0 equiv) of 6-bromo-2-(2’-methoxyphenyl)imidazo[1,2-a]pyridine (4) [25], 0.11 g (0.09 mmol, 0.04 equiv) of Pd(PPh3)4(0), and 80 mL of mixture of

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• available naphthalene-2-ylboronic acid or (3,4-dihydronaphthalen-2-yl)boronic acid (Scheme 1). The latter was synthesized according to a literature procedure [36]. Formation of compounds 2b–h was accomplished through Heck coupling of aryl bromides with the appropriate styrenes (Scheme 2) [37]. Compounds 2b

• ) appropriate boronic acid, Pd(PPh3)4, Na2CO3, DMF, H2O, microwave, 15 min, 150 °C, 43–64%. Reagents and conditions: a) Pd2(dba)3 or Pd(OAc)2, P(o-tol)3, TEA, DMF, 120–140 °C, 0.7–24 h, 11–75%; b) potassium vinyltrifluoroborate, Cs2CO3, PdCl2(PPh3)2, ACN, H2O, 1.5 h, 120 °C, 78% c) tributylvinyltin, Pd(PPh3)4

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

• Juanjuan Feng,
• Tianyu Li,
• Jiaxin Zhang and
• Peng Jiao

Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179

• boronic acid had been widely utilized to disconnect the N–O bond as well as to hydrolyze the resulting imine into a ketone [52]. We applied this method to deprotect the isoxazoline 3. However, the desired β-hydroxy ketone was never obtained. In one instance, the methyl ketone from a retro-aldol reaction

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• %; ii) N-bromosuccinimide, chloroform, 60 °C, yield: 87%; iii) (4-hydroxyphenyl)boronic acid, Pd(PPh3)4, K2CO3, CsF, toluene/THF/H2O, reflux, 8 h, yield: 70%; iv) K2CO3, 1,5-dibromopentane, acetone, 80 °C, yield: 67%; v) NaN3, DMF, yield: 84%; vi) paraformaldehyde, BF3·OEt2, 1,2-dichloroethane, yield

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

• Daniela Imperio,
• Erika Del Grosso,
• Silvia Fallarini,
• Grazia Lombardi and
• Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

• suitable agents for boron neutron capture therapy (BNCT) became a major need. Among many others, sugar boronic acids have recently attracted attention as boron carriers. Herein we report the synthesis and preliminary biological studies of two new sugar analogues containing a boronic acid at the anomeric

• position. The analogues were obtained by hydroboration of proper open-chain terminal alkenes that, after quenching with water, spontaneously afforded cyclic boronic acids with hemiacetal-like structures. Keywords: antitumor agents; boron neutron capture therapy; boronic acid; hydroboration; sugar analogue

• . Galactose and fructose also allow tumor growth in the absence of glucose. Boronic acid derivatives have gained interest in the last years in different fields such as the development of enzyme inhibitors, drug delivery polymers, saccharide sensors and as boron carriers for BNCT, e.g., amino acid derivatives

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides

• Madhu Babu Tatina,
• Xia Mengxin,
• Rao Peilin and
• Zaher M. A. Judeh

Beilstein J. Org. Chem. 2019, 15, 1275–1280, doi:10.3762/bjoc.15.125

• blocks especially for natural product synthesis [36][37][38][39][40]. Therefore, we used the perfluorophenyl boronic acid catalyst in the reaction between 2,3,4,6-tetra-O-acetyl-D-glucal (1a) and benzyl alcohol, n-butyl alcohol, cyclohexyl alcohol and p-toluenethiol (Figure 2). Gratifyingly, the reaction

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• as the conjugation of steroids to amino acids, peptides and carbohydrates. We demonstrate that steroids are available with almost all types of MCR reactive functionalities, e.g., carbonyl, carboxylic acid, alkyne, amine, isocyanide, boronic acid, etc., and that steroids are suitable starting

• or by the N-terminus to the estrone-derived boronic acid 64 using the on-resin Petasis-3CR in the presence of dihydroxyacetone [68]. Peptido-steroids 65 and 67 were obtained in good overall yields after released from the resin using the cocktail TFA/H2O/triisopropylsilane (TIS), albeit the

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• only viable alternative to bipyridine (Table 1, entry 7), with other ligands commonly used in copper-catalyzed reactions such as proline and 2,2,6,6-tetramethyl-3,5-heptanedione giving yields under 15%. Reducing the number of equivalents of boronic acid 25 and sodium carbonate was found to be well

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• asymmetric products 131 is mainly obtained, where the aromatic group coming from the boronic acid partner settles far from the carbonyl group. Methoxy, nitro, chloro and acetoxy groups of the aromatic moiety can be located at the ortho, meta and para positions, although 2-nitro derivatives gave low yields or

• palladium-catalysed reactions (Scheme 38). The first one is a Sonogashira coupling reaction between the terminal alkyne of propiolamide 128 and aryl iodide 129, which is preferred to the Suzuki–Miyaura reaction between aryl iodide 129 and boronic acid 130 present in the reaction mixture. Then, an internal

• , presumably by changing the anionic character of the palladium complex to cationic in intermediate 135. Finally, the Suzuki–Miyaura coupling of palladium salt 135 with boronic acid derivative 130 would provide the final oxindoles 131 or 132. Finally, is worth mentioning an example of a multicomponent

Solid-phase synthesis of biaryl bicyclic peptides containing a 3-aryltyrosine or a 4-arylphenylalanine moiety

• Iteng Ng-Choi,
• Àngel Oliveras,
• Lidia Feliu and
• Marta Planas

Beilstein J. Org. Chem. 2019, 15, 761–768, doi:10.3762/bjoc.15.72

• )/H2O (95:2.5:2.5) for 2 h affording the linear boronopeptide H-Phe(4-B(OH)2)-Ala-Gln-Leu-Gln-Phe(4-I)-βAla-Gln-OpNB in >99% purity, which was characterized by mass spectrometry. The boronic acid function resulted from hydrolysis of the boronic ester during HPLC analysis as shown by mass spectrometry

Synthesis and biological activity of methylated derivatives of the Pseudomonas metabolites HHQ, HQNO and PQS

• Sven Thierbach,
• Max Wienhold,
• Susanne Fetzner and
• Ulrich Hennecke

Beilstein J. Org. Chem. 2019, 15, 187–193, doi:10.3762/bjoc.15.18

• . The strategy to “oxidize” the 3-position of AQs via iodination, lithium–halogen exchange and electrophilic trapping can offer a flexible approach to new 3-substituted AQs starting from an easily available synthetic intermediate. While we decided to oxidize the newly formed boronic acid ester in situ

• , its isolation should be possible and enable further modification, for example by ipso-substitution with heteroatom electrophiles. The application of the boronic acid in Suzuki–Miyaura coupling should also be possible [30][31]. Growth inhibition experiments against S. aureus showed that HQNO

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• -workers [33] demonstrated an efficient route for the construction of the benz[a]anthracene structural unit by employing SM cross coupling followed by RCM sequence. Treatment of the bromonaphthalene derivative 20 with (2-formyl-4-methoxyphenyl)boronic acid (21) in the presence of a palladium catalyst

• respective ring-closure products 62a (98%) and 62b (97%). Finally, SM coupling of 8-halo-7-methoxycoumarins 62a,b with (4-methylfuran-3-yl)boronic acid (63) delivered the cross-coupling product 64 (Scheme 9). In another event, Magnier and co-workers [40] described a simple synthetic route to sulfoximines by

• route to construct the dibenzocyclooctadiene lignan core of the natural product schisandrene via SM coupling and RCM as key steps. In this context, the SM reaction of boronic acid 102 with bromoaldehyde 103 in the presence of Pd2(dba)3 and the S-Phos ligand provided the cross-coupling product 104 (82

Synthesis of indolo[1,2-c]quinazolines from 2-alkynylaniline derivatives through Pd-catalyzed indole formation/cyclization with N,N-dimethylformamide dimethyl acetal

• Antonio Arcadi,
• Sandro Cacchi,
• Giancarlo Fabrizi,
• Francesca Ghirga,
• Antonella Goggiamani,
• Antonia Iazzetti and
• Fabio Marinelli

Beilstein J. Org. Chem. 2018, 14, 2411–2417, doi:10.3762/bjoc.14.218

• atmosphere, resulted in a loss of efficiency (Table 1, entry 2). Good results were also observed with phenyl- and 1-naphthylboronic acids (Table 1, entries 5 and 6). Electron-poor arylboronic acids proved to be effective (Table 1, entries 7–10), and only (4-chlorophenyl)boronic acid gave a moderate yield of

• through cross-coupling reactions. Only in the case of two ortho-substituents on the aryl residue of the boronic acid the reaction afforded the target product 10p in low yield (Table 1, entry 17), and 12-unsubstituted derivative 13p as the major product. Then, with the aim of obtaining 12-unsubstituted

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• between 4 with 5 (Table 1). For this purpose we performed a more detailed study of the sequence of coupling with 3,4,5-tribromo-2,6-lutidine. Therefore, a series of Suzuki–Miyaura cross-coupling reactions under different reaction conditions were performed with an amount of boronic acid being

• )-2,6-dimethylpyridine (6) as a substrate in comparison to 3,4,5-tribromo-2,6-dimethylpyridine as substrate. The variation of temperature, reaction time and amount of boronic acid caused only minute changes in the distribution of atropisomers 1–3 with the same almost quantitative total yield (Table 2

• a boronic acid which cannot coordinate the palladium atom and having an electron withdrawing group (for example ortho-chlorophenylboronic acid). We therefore performed a series of reactions of brominated 2,6-lutidine 4 with 9–12 equiv of ortho-chlorophenylboronic acid 11 in different coupling

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

• conditions by the Pd-catalyzed Suzuki–Miyaura reaction of the aryldiazonium salts 4a–d with benzo[b]quinolizinium-9-trifluoroborate (3b). The latter substrate was obtained as analytically pure product in moderate yield by the reaction of benzo[b]quinolizinium-9-boronic acid (3a) [34] with NaBF4 (Scheme 1

• acids or esters with base-free conditions are known [39][42], in our hands the reaction of benzo[b]quinolizinium-9-boronic acid (3a) with benzenediazonium tetrafluoroborate 4a only resulted in the formation of the benzo[b]quinolizinium-9-trifluoroborate (3b). Consequently, we used the latter substrate

• -arylbenzo[b]quinolizinium derivatives 1a–d were available in yields that are comparable, or even slightly higher, than the ones obtained with the Suzuki–Miyaura reaction of benzo[b]quinolizinium-9-boronic acid (3a) with bromoarenes [34]. In our previous attempts to synthesize the corresponding benzo[b

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• compatible with both electron-donating and electron-withdrawing substituents on the aryl bromides and boronic acid substrates as well as activated aryl chlorides. Depending on the presence or absence of the TBAB additive, the reaction may be fine-tuned to either proceed via steric or electronic control. The