Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

• Kan Tang,
• Megan R. Brown,
• Chad Risko,
• Melissa K. Gish,
• Garry Rumbles,
• Phuc H. Pham,
• Oana R. Luca,
• Stephen Barlow and
• Seth R. Marder

Beilstein J. Org. Chem. 2023, 19, 1912–1922, doi:10.3762/bjoc.19.142

• remaining unidentified product may be R2 (C36H74), but this product is not easily detected by GC–MS. In sharp contrast to the case of benzyl derivatives, where the use of dimer reductants primarily affords R2 products, biaryls are not observed as dehalogenation products of aryl halides by dimeric reductants

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• of a wide range of axially chiral biaryls, heterobiaryls, vinylarenes, N-arylamines, spiranes, and allenes with high efficiency and excellent stereoselectivity. Keywords: allenes; atropisomerism; axial chirality; chiral phosphoric acid; heterobiaryls; spiranes; Introduction Axial chirality is one

• ] play a crucial role in asymmetric catalysis, the construction of numerous axially chiral biaryls/heterobiaryls [21][35][36][37][38], and other useful asymmetric transformations [5]. Although chiral phosphoric acids have shown promising properties in asymmetric catalysis and play a significant catalytic

• role in the development of axially chiral compounds with biaryls, heterobiaryls, atropisomeric arylalkenes, allenes, and spiranes, there are only few comprehensive reviews in this area. Therefore, the aim of this review is to provide readers with an overview of recent advances in the asymmetric

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• ][27][28]. Various approaches starting from functionalized biaryls have hereby attracted considerable interest, since the precursors are readily available by established cross-coupling reactions. Beyond transition-metal-catalyzed reactions, acid-mediated cyclizations of biphenylcarboxylic acids and

• , giving fluorenone (3) in 62 and 76% yields [38]. Tadigoppula reported a PhI(OAc)2–BF3·OEt2-mediated cyclization of aldimines [39]. This prompted us to perform a systematic investigation of the potential of oxidative cyclizations of aminomethylated biaryls 2 and related compounds to fluorenones

• varying degree on the overall yield. This new protocol was utilized for the first total synthesis of the natural fluorenone nobilone (1d). Selected fluorenone-type natural products. Overview of published cyclization methodologies for the synthesis of fluorenones starting from functionalized biaryls

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• silica gel column chromatography (hexane/CH2Cl2 = 3:1) gave 1b (1.31 g, 88%). Conventional methods for the synthesis of helicenes. Brønsted acid-catalyzed cycloaromatization of biaryls bearing an acetal moiety. Two strategies for the helicene synthesis via Suzuki–Miyaura coupling/cycloaromatization

Total synthesis of decarboxyaltenusin

• Lucas Warmuth,
• Aaron Weiß,
• Marco Reinhardt,
• Anna Meschkov,
• Ute Schepers and
• Joachim Podlech

Beilstein J. Org. Chem. 2021, 17, 224–228, doi:10.3762/bjoc.17.22

• -3,5-dimethoxybenzene, where the longest linear sequence consists of five steps. The key reaction was a palladium-catalyzed Suzuki coupling of an aromatic boronate with a brominated resorcin derivative. Keywords: biaryls; boronates; mycotoxins; polyketides; Suzuki coupling; Introduction 5’-Methoxy-6

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• starting materials, rather expensive catalysts, harsh reaction conditions or low product yields. Transition-metal-catalyzed, electrophile-induced and oxidative radical cyclizations of ortho-alkynylated biaryls are widely used for the synthesis of polynuclear aromatics [57][58][59][60][61][62][63][64][65

• steps of the method are electrophile-induced 6-endo-dig cyclizations of ortho-alkynylated biaryls. The overall yields of helicenes in five stages of the synthesis exceed 30%. The single-crystal X-ray diffraction analysis revealed the non-planar crystal structures of the synthesized helicenes responsible

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• reports described that in some cases biaryls may be obtained in variable yields starting from biaryl phosphates [52], biaryl phosphonates II [53][54][55][56], and triaryl phosphates [57][58][59][60][61] (Scheme 1d, path b). In search for alternative ways for the preparation of biaryls under photoinduced

• % yield. Similar results were obtained with 4-alkylphenyl diphenyl phosphates, that afforded the 4-substituted biaryls 2c–e in up to 83% yield. However, when examining substrates bearing a strong electron-donating substituent (G = 4-OMe, 4-OPh, 3-OMe), the efficiency of the process decreased (see the

• these cases, the expected phenylated arenes 2j–l were isolated in the 50–64% range. We were then intrigued to extend the scope of the reaction by focusing on a few ethyl diaryl phosphates 3a–e. Gratifyingly, the formation of the symmetric biaryls 4 took place efficiently with the substrates bearing

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• ; ellagic acid; oxidative dimerization; Introduction Over the last century, the formation of an aryl to aryl bond has garnered considerable synthetic attention due to the applications of biaryls as pharmaceutical agents, as well as chiral auxiliaries in asymmetric synthesis [1][2][3]. Methods such as the

• Ullman coupling, Suzuki–Miyaura coupling and Stille coupling have dominated the field for the synthesis of biaryls [1][4]. Throughout the years, the exploration of oxidative dimerization reactions of electron-rich aromatic compounds, such as thiophenes, anilines and alkoxyarenes, in an attempt to

• establish high-yielding and selective oxidative coupling reactions, has afforded new and greener synthetic protocols for biaryls [5][6][7]. Several oxidants, such as the salts of Ag(I&II) [8], Ti(III&IV) [9], Mn(III) [10], Ce(IV) [11], Sn(IV) [12] and Fe(III) [13], as well as the hypervalent iodine reagents

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• was necessary to generate the aryl radicals (Figure 22). Similar results were obtained with this new procedure. This modified protocol was also compatible with a diversity of DGs and diazonium salts, thus furnishing a panel of 20 biaryls in good yields. Inspired by this work, several research groups

• compatible with a panel of electron-poor aryldiazonium partners, affording the targeted biaryls in moderate to high yields. Based on a literature survey, a plausible mechanism of this reaction is initiated by the addition of an aryl radical (generated from the corresponding diazonium precursor) to the Au(I

• reaction protocol, a range of biaryls was synthesized in moderate to good yields under very mild reaction conditions. Nevertheless, due to regioselectivity issues, this photo-flow direct arylation was mainly limited to symmetrical aryls. The site-selectivity issues could, however, be solved by using

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• the design of dye-sensitized solar cells (DSSC) [4]. Typical methods for the construction of a phenanthrene core involve transition-metal-catalyzed cycloisomerizations starting from arynes [5][6], o-alkynyl-biaryls [7][8], or substituted N-tosylhydrazones [9]. However, since the introduction in 1964

• -isocyano-1,1'-biaryls 4.1 have been reported, as summarized in Scheme 4. Along with substrate 4.1, a radical source R–X and a photocatalyst (PC), which is activated upon visible-light irradiation, are usually required. Oxidative quenching of the photoexcited PC* by R–X (path a) affords, upon loss of the

• biaryls 5.1a–d in up to excellent yields at room temperature by using α-bromoesters as radical precursors and [fac-Ir(ppy)3] as the photoredox catalyst [49]. A similar photocatalyzed tandem insertion/cyclization approach based on isocyanides and amino acid/peptide-derived Katritzky salts as precursors of

Pd-catalyzed asymmetric Suzuki–Miyaura coupling reactions for the synthesis of chiral biaryl compounds with a large steric substituent at the 2-position

• Yongsu Li,
• Bendu Pan,
• Xuefeng He,
• Wang Xia,
• Yaqi Zhang,
• Hao Liang,
• Chitreddy V. Subba Reddy,
• Rihui Cao and
• Liqin Qiu

Beilstein J. Org. Chem. 2020, 16, 966–973, doi:10.3762/bjoc.16.85

• bromobenzene substrates and the Pd···O interaction between carbonyl and palladium seem essential to achieve high enantioselectivity. Keywords: asymmetric catalysis; biaryls; monophosphine ligand; palladium catalyst; Suzuki–Miyaura couplings; Introduction Axially chiral molecules have received much attention

• studied fruitfully by Cammidge [37][38], Buchwald [13][28][39], Tang [40][41][42][43] and other groups [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59]. Nevertheless, for the asymmetric formation of large steric systems such as sterically demanding biaryls still remain limitations [24

Synthesis of triphenylene-fused phosphole oxides via C–H functionalizations

• Md. Shafiqur Rahman and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2020, 16, 524–529, doi:10.3762/bjoc.16.48

• converted to the triflate, and subjected to Suzuki–Miyaura couplings with 2-bromophenylboronic acid (5a) or 3-bromonaphth-2-ylboronic acid (5b) to afford the phosphole-fused biaryls 6a and 6b, respectively, in decent yields. Subsequent Suzuki–Miyaura couplings of 6a or 6b with 3,4-dialkoxyarylboronic acids

Synthesis of six-membered silacycles by borane-catalyzed double sila-Friedel–Crafts reaction

• Yafang Dong,
• Masahiko Sakai,
• Kazuto Fuji,
• Kohei Sekine and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2020, 16, 409–414, doi:10.3762/bjoc.16.39

• of phenothiasilin 3l that was obtained in 93% yield starting from diaryl thioether 1g. N-(Benzyl)methylamine-substituted diaryl thioether 1h was also transformed into phenothiasilin 3m in 58% yield. The corresponding six-membered silacycles were not formed using N-aryl-bridged biaryls as substrates

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• -isomer, but it should be complemented with other strategies to further increase intrinsic activity. Substituent effects on the outer ring One of the postulated contributors to the CXCR3 agonism effect of parent biaryls such as 1d and 1e is the increased π-electron density of the aromatic rings [24]. A

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• )2 and P(2-furyl)3 with aryl iodides 19a and 19b led to the expected biaryls 20a and 20b in moderate yields (Scheme 3). All these reactions proceeded without byproducts being observed. In all cases unreacted substrate 9d was recovered in correspondent quantity. With the 5-(hetero)aryl-substituted 4

• -catalysed intramolecular tandem stannylation/biaryl coupling protocol gave the attempted pentacyclic products [32]. However, having the biaryls 20a and 20b prepared we intended to develop a new approach to pyrido[4,3,2-mn]acridines by an alternative intramolecular cyclization step. To reach that aim, the

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

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• : asymmetric organocatalysis; axial chirality; biaryls; hydrogen bond; oxo-Diels–Alder reaction; Introduction The Diels–Alder (DA) reaction is a useful and easy-to-perform method for the synthesis of six-membered rings through the direct formation of C–C bonds between a diene and a dienophile (a substituted

A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade

• Hong Yan,
• Zhong-Yi Mao,
• Zhong-Wei Hou,
• Jinshuai Song and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2019, 15, 795–800, doi:10.3762/bjoc.15.76

• Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, People’s Republic of China 10.3762/bjoc.15.76 Abstract A diastereoselective approach to axially chiral imidazopyridine-containing biaryls has been developed. The reactions proceed through a radical cyclization cascade to construct

• the biaryls with good to excellent central-to-axial chirality transfer. Keywords: axial chirality; biaryl; electrochemistry; oxidation; radical; Introduction Axially chiral biaryls are prevalent in natural products, bioactive molecules and organocatalysts [1][2]. Among the many methods that have

• been developed for the synthesis of chiral biaryls [3][4][5][6][7][8][9][10], reactions that take avantage of the central-to-axial chirality transfer have been less explored [11][12][13][14]. In addition, an antroposelective synthesis of imidazopyridine-based biaryls has not been reported. Nitrogen

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• reagents [39][40] with various halo derivatives (e.g., aryl, vinyl, benzyl, or allyl) and has a broad scope to assemble diverse targets. This reaction was first reported in 1977, and it is an elegant and versatile method that allows the preparation of biaryls and olefins in good yields. To the best of our

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

• with Suzuki–Miyaura cross coupling in combination with metathesis (or vice-versa). Several cyclophanes, polycycles, macrocycles, spirocycles, stilbenes, biaryls, and heterocycles have been synthesized by employing a combination of Suzuki cross-coupling and metathesis. Various popular reactions such as

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

• selectivity using a differently ortho-substituted phenylbornic acid was observed. Keywords: arylpyridines; atropisomerism; cross-coupling; palladium; Suzuki–Miyaura reaction; Introduction Axially chiral biaryls not only subsist in many classes of natural and bioactive compounds [1][2] but also are an

• [10][11][12][13]. In recent years, many successful attempts to regioselective [14][15][16][17], chemoselective [18][19][20][21] or atropselective [1][22][23][24][25][26] synthesis of biaryls were presented, often taking advantage of the popular and useful Suzuki–Miyaura cross-coupling reaction

• ’-bromopyridinium N-(2’-pyrazinyl)aminides [17]. In 2014, a regiocontrolled polyarylation of pyridine was presented by Doebelin and co-workers [27]. Rotationally restricted biaryls are stereochemically and structurally important elements of a rapidly growing class of catalysts, natural products and chiral

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

• coupling reaction is a powerful method for the synthesis of ubiquitous biaryls and has been extensively employed in the synthesis of natural products, pharmaceuticals, agrochemicals, and polymers. The reaction usually involves a palladium-catalysed coupling of aryl boronates with aryl halides in organic

• . While activated aryl chloride 21f reacted with boronic acids possessing either electron-donating or electron-withdrawing groups to provide the corresponding biaryls in reasonable yields, to our dismay the reaction of inactivated aryl chlorides led to the recovery of starting materials (Table 3, entries

• partners in aqueous medium. All the complexes could catalyse the Suzuki–Miyaura coupling reaction to provide the corresponding biaryls in excellent yields with only 0.5 mol % catalyst loading. Furthermore, unlike the previously reported SNS pincer Pd(II) complexes, the catalysts in the current study were

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

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• traditional Pd-catalyzed aryl–heteroaryl coupling to biaryls [57]. Since then, KOt-Bu has been used as a mediator for various reactions including aryl–aryl coupling [58][59][60][61][62][63], inter- and intramolecular cyclizations [64][65][66][67][68], amidation [69], alkenylation [70], oxidation [71] and