Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• electron-donating substituents at the para-position of the N-arylacrylamide led to good yields. In cases of meta-substitution, a mixture of C6 and C4-substituted oxindole products were obtained, whereas ortho-substitution resulted in the desired oxindoles in moderate yields. Nitrogen substitution was also

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• isolated in a high yield of 84% with reisolation of the 5-(2-iodophenyl)-1H-tetrazole (6) in 90% yield. Other para-halogenated benzaldehydes 4b–f were isolated in good yields of up to 88%. ortho-Substitution led to a lower yield of the iodinated product 4g (43%) compared to the para-iodinated analogues 4d

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• loading. Substrates with electron-withdrawing groups are tolerated, whereas strong electron-releasing groups decrease the reactivity. Steric hindrance also plays a crucial role, with ortho-substitution resulting in reduced catalytic activity. Mankad and co-worker [89] developed dehydrogenative borylation

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• amides was quite wide, including different EWGs and EDGs, as well as heterocycles, ortho-substitution was not tolerated. The authors applied the methodology for the synthesis of biologically important benzo[c]phenanthridine derivatives 117. Through methylation and subsequent aromatization of the

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• , good yields of the corresponding oxindoles (3da–ga) were achieved. A trifluoromethyl-substituted acrylamide afforded the product 3fa in very high 85% yield. In addition, ortho-substitution at the N-aryl moiety was also well tolerated, albeit with slightly decreased yields (3ha–ka, 50–63

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• (>20:1 dr, 84–>99% ee). Possibly due to the influence of steric hindrance, reactions involving substrate 2 with ortho-substitution on the benzene ring has lower yields and worse enantioselectivities than those with meta-substitution and para-substitution. Meanwhile, the enantioselectivities of the

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• aryl bromides proved to be the best coupling partners for this reaction (3, 7–9, 65–91%). Pyridyl bromides also proved to be very efficient (11, 12, 73–74%). The results also demonstrate that ortho-substitution in the aromatic ring poses no impeditive challenge to this reaction (10, 73%). The next step

Ligand-dependent stereoselective Suzuki–Miyaura cross-coupling reactions of β-enamido triflates

• Tomáš Chvojka,
• Athanasios Markos,
• Svatava Voltrová,
• Radek Pohl and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 2657–2662, doi:10.3762/bjoc.17.179

• gel. A moderate loss of stereochemistry was observed only in cases of bulky ortho-substitution of either arylboronic acid or vinyl triflate (2ad, 2da, and 2dd). Alkylboronic acids were found to be unreactive even after prolonged reaction time (1a with n-hexylboronic acid, 60 h, rt). Next, conditions

Enantioselective PCCP Brønsted acid-catalyzed aminalization of aldehydes

• Martin Kamlar,
• Robert Reiberger,
• Martin Nigríni,
• Ivana Císařová and
• Jan Veselý

Beilstein J. Org. Chem. 2021, 17, 2433–2440, doi:10.3762/bjoc.17.160

• -workers, using an (S)-TRIP derivative as the chiral catalyst (Figure 1) [14]. Soon after, Rueping et al. developed a similar methodology catalyzed by other chiral BINOL-phosphoric acids [15]. However, the reaction suffered from limited scope to aromatic aldehydes without an ortho-substitution; the

Synthesis of aryl 2-bromo-2-chloro-1,1-difluoroethyl ethers through the base-mediated reaction between phenols and halothane

• Yukiko Karuo,
• Ayaka Kametani,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2021, 17, 89–96, doi:10.3762/bjoc.17.9

• phenol, p-methoxyphenol (1b) was used, the reaction proceeded to afford ether 2b in 79% yield (Table 2, entry 1). An ortho-substitution with the bulkier tert-butyl group slightly affected the reaction giving product 2c in still acceptable yield (47%, Table 2, entry 2). p-Nitrophenol (1d), which is an

Deoxyfluorination of acyl fluorides to trifluoromethyl compounds by FLUOLEAD^®/Olah’s reagent under solvent-free conditions

• Yumeng Liang,
• Akihito Taya,
• Zhengyu Zhao,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2020, 16, 3052–3058, doi:10.3762/bjoc.16.254

• results are summarized in Scheme 2. Various acyl fluorides were investigated in the presence of 3 equiv of FLUOLEAD® and 5 equiv of nHF·pyridine. We first examined the deoxyfluorination of biarylacyl fluorides 1a and 1b with a para- or ortho-substitution. Both substrates gave excellent yields of the

Synthesis and characterization of bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives

• David Martínez-López,
• Amirhossein Babalhavaeji,
• Diego Sampedro and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2019, 15, 3000–3008, doi:10.3762/bjoc.15.296

• ; azonium; molecular switches; ortho substitution; photoisomerization; photoswitch; visible light; Introduction The application of photoswitches to control biological targets has been a driving force for the development of photoswitches that operate at wavelengths that are compatible with cells and tissues

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• azoarenes have been ortho-substitution of the benzene ring(s) or replacement of one of the benzenes for a pyrazole (to give arylazopyrazole switches). Here we study the combination of such high-performance features within a single switch architecture. Through computational analysis and experimental

• results therefore define improved designs for high performance azo switches, which will allow for high precision optically addressable applications using such components. Keywords: arylazopyrazoles; azobenzenes; molecular switches; ortho-substitution; photoswitches; thermal half-life; Introduction

• advancement to tackle these limitations in recent times has been the discovery that tetra-ortho substitution of the azobenzene unit can lead to a significant improvement of the photoswitching properties (Figure 1a). Specifically, o-methoxy [10][11] and o-thio [12] analogues reported by Woolley and co-workers

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

• substitution pattern of this biaryl moiety, a broad spectrum of efficacies for CXCR3 can be obtained, i.e., from antagonists to partial agonists and full agonists (Figure 1C) [24]. Meta and para-substitution yields antagonists (exemplified by 1a,b), while ortho-substitution with halogen atoms provides agonists

• inactive GPCR, while green represents the active GPCR. C) General structure and exemplary functional dose-response curves of the parent biaryl family of CXCR3 ligands disclosed in Wijtmans et al. [24], in which ortho substitution on the outer aromatic ring gives partial or full agonists, while meta

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

• reaction has well tolerated differently substituted ketones, with lack of product in case of ortho-substitution due to steric hinderance. Similarly, substituted 2-APs provided a library of compounds with god yield, however, α,β-unsaturated ketones, such as benzalacetone, did not afford any desired product

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

• Cyrus Mowdawalla,
• Faiz Ahmed,
• Tian Li,
• Kiet Pham,
• Loma Dave,
• Grace Kim and
• I. F. Dempsey Hyatt

Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91

• the use of BF3·Et2O seemed to be superior to Tf2O in the case of some I(III) reactants. In all the reactions tested, there were no products formed with the ortho-substitution pattern in contrast to the RICR, however, it is clear that electron-donating groups influence the ring substitution. When

Synthesis of fluoro-functionalized diaryl-λ³-iodonium salts and their cytotoxicity against human lymphoma U937 cells

• Prajwalita Das,
• Etsuko Tokunaga,
• Hidehiko Akiyama,
• Hiroki Doi,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2018, 14, 364–372, doi:10.3762/bjoc.14.24

• , but this value decreased considerably to 7.8% when used at 1 μM. Following this investigation, we found that the ortho-substituted diaryliodonium salts with an ortho-SO2CF3 group 3k and an ortho-CF3 group 3m displayed impressive results. A common feature of ortho-substitution on the aromatic group is

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• to the National Television Standards Committee standard (NTSC) blue values of (0.14, 0.08) [36]. Upon ortho-substitution of the dimesitylphenylboron acceptor with a carbazole, a mutual steric hindrance could be exerted between the donor and the acceptor resulting in the large dihedral angle of 72.6

• their differences of PLQYs (16.7%, 50.5% and 43.0% for T17, T18 and T19, respectively), the three molecules exhibiting similar photophysical properties (ΔEST, emission wavelength and decay times of the delayed emission). Recently, a potential alternative to the ortho-substitution of the triazine

Quinone-catalyzed oxidative deformylation: synthesis of imines from amino alcohols

• Xinyun Liu,
• Johnny H. Phan,
• Benjamin J. Haugeberg,
• Shrikant S. Londhe and
• Michael D. Clift

Beilstein J. Org. Chem. 2017, 13, 2895–2901, doi:10.3762/bjoc.13.282

• scope of this methodology by employing a range of 1,2-amino alcohol substrates 1 (Table 2). As reported in Table 1, the reaction involving phenylglycinol gave the desired N-PMP imine (7a) in 85% yield (Table 2, entry 1). ortho-Substitution of the arene is reasonably well-tolerated, as 2

Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids

• Simon Drescher,
• Vasil M. Garamus,
• Christopher J. Garvey,
• Annette Meister and
• Alfred Blume

Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99

• lamellar structure – prerequisites for the use as drug delivery vehicle – could not be observed, and bilayer fragments as well as elongated micelles were formed instead [35]. The isomers PC-C17mPhC17-PC and PC-C17oPhC17-PC, bearing a meta or ortho substitution at the central phenyl ring, showed the

(Z)-Selective Takai olefination of salicylaldehydes

• Stephen M. Geddis,
• Caroline E. Hagerman,
• Warren R. J. D. Galloway,
• Hannah F. Sore,
• Jonathan M. Goodman and
• David R. Spring

Beilstein J. Org. Chem. 2017, 13, 323–328, doi:10.3762/bjoc.13.35

• was observed (Figure 1). Whilst Hammett parameters are not tabulated for ortho-substitution, precluding an analogous quantitative analysis, the trend for ortho-halogenated substrates is qualitatively similar, although with even higher amounts of (Z)-product. This implies that electron-withdrawing

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• dependent on the solvent system; the enantioselectivity in benzene was significantly higher than in toluene or dioxane. Electron rich, neutral, and poor organotrifluoroborates were good substrates; however, ortho-substitution was not compatible and provided only trace product. In a subsequent publication

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

• groups, as well as sterically hindered aromatic rings, all taking place at room temperature. Suzuki–Miyaura-type C–H coupling reactions are typically more tolerant of electron-withdrawing groups (3d, 3f, 3k) and ortho-substitution (3g) on the aryl ring. On the other hand, the reaction with 4

[2.2]Paracyclophane derivatives containing tetrathiafulvalene moieties

• Laura G. Sarbu,
• Lucian G. Bahrin,
• Peter G. Jones,
• Lucian M. Birsa and
• Henning Hopf

Beilstein J. Org. Chem. 2015, 11, 1917–1921, doi:10.3762/bjoc.11.207

• recent report has appeared concerning the synthesis of a [2.2]paracyclophane doubly substituted by a dimeric tetrathiafulvalene in a pseudo-ortho substitution pattern [10]. This compound exhibited novel chiroptical properties. Prompted by these observations, we decided to investigate the synthesis of a

Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions

• Andreas Gansäuer,
• Andreas Okkel,
• Lukas Schwach,
• Laura Wagner,
• Anja Selig and
• Aram Prokop

Beilstein J. Org. Chem. 2014, 10, 1630–1637, doi:10.3762/bjoc.10.169

• proximity – ortho-substitution in 16 leads to a lower AC50 value than para-substitution in 15 – of the metal center enhances the biological activity. Conclusion In summary, we have devised an operationally simple, convenient, and mild strategy for the synthesis of triazole substituted titanocenes via strain