Synthesis of new representatives of A₃B-type carboranylporphyrins based on meso-tetra(pentafluorophenyl)porphyrin transformations

• Victoria M. Alpatova,
• Evgeny G. Rys,
• Elena G. Kononova and
• Valentina A. Ol'shevskaya

Beilstein J. Org. Chem. 2024, 20, 767–776, doi:10.3762/bjoc.20.70

• meso-pentafluorophenyl-substituted porphyrins. Carboranes, due to their unique physical and chemical properties such as high chemical and biological stability [28][29], three-dimensional aromaticity [30][31], low toxicity [28], high hydrophobicity, and enriched boron content [32][33] are perspective

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae

• Jia Tang,
• Yixiang Zhang and
• Yudai Matsuda

Beilstein J. Org. Chem. 2024, 20, 638–644, doi:10.3762/bjoc.20.56

• polyketide moiety, contributing to structural diversification [9][10]. By contrast, in the biosynthesis of meroterpenoids derived from orsellinic acid and 5-methylorsellinic acid (5-MOA), the prenylation reaction typically occurs at the non-substituted carbon atom and thus preserves the aromaticity of the

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• reported that two-electron oxidation of [n]CPPs yields dications, [n]CPPs2+ [17][21][43], which are unusually stable due to the presence of in-plane aromaticity derived from the ring structure [19]. Therefore, we speculated that the CPP dication could be used as a host or a guest to alter the electronic

• stabilized by in-plane aromaticity, the single-electron transfer from [10]CPP to [5]CPP2+ to form [10]CPP•+⊃[5]CPP•+ is energetically unfavorable. The association constant (Ka) between [10]CPP⊃[5]CPP2+ [B(C6F5)4−]2 in 1,1,2,2-tetrachloroethane-d2 (TCE-d2) at 50 °C was determined to be 1.07 × 103 L·mol−1 by

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• indenofluorene (IF) or fluorene cores and containing various dithiafulvene (DTF) donor units that gain aromaticity upon oxidation and a variety of acceptor units, such as vinylic diesters, enediynes, and cross-conjugated radiaannulenes (RAs) that gain aromaticity upon reduction. In some cases, the DTF units are

• with one of the exocyclic enediyne units removed) [17][18] is a particularly good electron acceptor as it gains 14π-aromaticity upon reduction. In this work, we also want to further explore pyrrolo-annelated IF-DTFs with different substituents on the nitrogen atom, and the functionalization at the

• reduced at −0.81 V and −1.09 V vs Fc/Fc+ (similar conditions), but no donor properties (thereby contrasting 26 and 27). Of the acetylenic scaffolds studied, DTF-IF-RA 23 containing an RA moiety is the strongest acceptor, which we ascribe to gain of 14πz-aromaticity of the cyclic moiety of the reduced

Substituent-controlled construction of A₄B₂-hexaphyrins and A₃B-porphyrins: a mechanistic evaluation

• Seda Cinar,
• Dilek Isik Tasgin and
• Canan Unaleroglu

Beilstein J. Org. Chem. 2023, 19, 1832–1840, doi:10.3762/bjoc.19.135

• selective synthesis of expanded porphyrins and their chemistry with regard to their aromaticity and coordination properties. They used meso-aryl-substituted dipyrromethanes and aldehydes in the synthesis of A3B3-type hexaphyrins [13] and 5,10-diaryl-substituted tripyrranes in A4B2-hexaphyrin synthesis [6

• porphyrins were detected in the mass spectra of some of the products. 1H NMR analysis of the synthesized hexaphyrins proved that the spectra were in consistence with [26]hexaphyrin aromaticity [29]. Several other metal triflates such as Zn(OTf)2, Gd(OTf)3, and Yb(OTf)3 were also tested as catalysts in the

Unprecedented synthesis of a 14-membered hexaazamacrocycle

• Anastasia A. Fesenko and
• Anatoly D. Shutalev

Beilstein J. Org. Chem. 2023, 19, 1728–1740, doi:10.3762/bjoc.19.126

• deviation of 0.054 Å from the mean-square plane. The nuclear-independent chemical shift (NICS) [48][49][50] values of 5 in its optimized conformation were used as a magnetic criterion of aromaticity. The NICS(0) value for the macrocyclic ring (+2.23 ppm in DMSO), calculated at the HF/6-31+G(d) level, shows

• its somewhat anti-aromatic character. Obvious aromaticity of the pyrazole rings is confirmed by the NICS(0) values of −12.64 ppm. Macrocycle 5 has various reactive centers, including two amidrazone fragments with primary amino groups, which makes it possible to modify it in many ways [51][52][53][54

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• oscillator model of aromaticity) indexes [43] of the rings: while the trimethoxy-substituted, hydrazide-derived one presents values of 0.995 (hdz-CH3) and 0.990 (hdz-NO2), indicating high aromaticity, the aldehyde-derived ring shows HOMA indexes of 0.964 (hdz-CH3) and 0.961 (hdz-NO2), suggesting that, for

• both compounds, this H-bond decreases the aromaticity of the phenol-containing ring. Finally, O1···N1 distances are 2.581(2) and 2.539(3) Å for hdz-CH3 and hdz-NO2, respectively (Table 2). Thus, all the structural evidence discussed above converges to the conclusion that the presence of the electron

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

• Swagat K. Mohapatra,
• Khaled Al Kurdi,
• Samik Jhulki,
• Georgii Bogdanov,
• John Bacsa,
• Maxwell Conte,
• Tatiana V. Timofeeva,
• Seth R. Marder and
• Stephen Barlow

Beilstein J. Org. Chem. 2023, 19, 1651–1663, doi:10.3762/bjoc.19.121

• presumably dominant in the present case. The importance of radical stabilization may in part be because the positive charges in Y = H or alkyl 1+ ions is already substantially stabilized by the aromaticity of the benzimidazolium ions, whereas the spin densities of the corresponding 1• radicals are highly

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• other two have imine character [11][12]. They are rigid, planar molecules which feature macrocyclic aromaticity due to the cyclic delocalisation of π electrons [13]. The well-defined macrocyclic cavity termed the coordination core, can encompass one, two, or more central ions (typically metal/metalloid

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

• the NHCs facilitates this donation and also helps to favor the singlet state by forcing the carbene carbon atom into a bent, more sp2-like arrangement. The thermodynamic stabilization of the NHCs derived from heteroaromatic compounds can be attributed to their partial aromaticity, which was calculated

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• product 12. In addition to the considered variant thermal suprafacial [1,9]-H sigmatropic shift resulting in compound 11 is implemented in this case. This transformation is energetically favorable due to the restoration of aromaticity of the benzene and pyrimidine rings. At the same time, the elimination

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

• 10. The selectivity for the non-dehydrogenated coumarins 10d is not understood, but 10b likely does not undergo dehydrogenation because there is no formation of aromaticity to drive the reaction forward. When the bicyclic alkene is substituted unsymmetrically at the bridgehead position, the reaction

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• such as triazine, diazines or aromatics containing cyano and sulfone groups are popular acceptor units for the construction of highly efficient TADF emitters [8][9][10][11]. Pyrimidine (1,3-diazine) owing to its aromaticity, significant π-deficiency, strong electron affinity, high luminous efficiency

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• ) would allow for the stabilization of the radical by the methoxy substituent in the ortho position to the departing substituent. The methoxy substituent then presumably loses a hydrogen radical to form acetic acid and intermediate 17c. Further loss of formaldehyde would restore aromaticity and furnish

• . Once intermediate 18b is formed an H+ is abstracted by an acetate ion from the methoxy substituent again forming formaldehyde and acetic acid, along with subsequent quenching of the cation to restore aromaticity. Examples of photoredox-catalyzed cation radical accelerated reactions with the aromatic

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• frameworks 57 were accessed in excellent yields up to 93% and enantioselectivities up to 94% ee. Increased aromaticity proved again to be essential for achieving high enantioselectivities. Additionally, Lewis base activation of the allylsilane substrates through the thiourea sulfur atom is proposed to be

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• excess of the indole reactant. It is seen that in the presence of a base the C-2 deprotonation becomes very fast in 9 (for regaining aromaticity) so the boron at the initial C-3-borylated intermediate 8 (formed via SEAr) cannot migrate fast enough, leading to a C-3 borylation product 10a (unlike Pd) [38

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• undergo a [1,5]-sigmatropic hydrogen shift, to reinstall aromaticity of the indole ring, leading to the formation of 9a. In situ oxidation of intermediates 9a or 9b, probably from the dissolved oxygen present in the reaction mixture, leads to the formation of 1-indolyl-3,5,8-substituted γ-carbolines 3aa

Models of necessity

• Timothy Clark and
• Martin G. Hicks

Beilstein J. Org. Chem. 2020, 16, 1649–1661, doi:10.3762/bjoc.16.137

• chemists would also recognize that the nitrogen atoms are blue and the chlorine green in the ball-and-sticks model, so that the atomic labels are not necessary. Even the alternating double and single bonds in the benzene rings are recognized to indicate aromaticity. Chemists immediately know where the

• instance, an MO picture of the SN2 reaction is attractive but less common than the compact and informative “curly arrow” picture. The Diels–Alder reaction or aromaticity, on the other hand, cannot really be treated adequately within the Lewis picture without resorting to the Dewar–Zimmerman rules [80][81

• poorly determined statistical modeling. As outlined above, this will happen almost exclusively based on the Lewis bonding model. Such applications must extend the scope of the Lewis model by automatically recognizing the context-dependent features like aromaticity or a tendency to undergo electrocyclic

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• exhibits a narrow energy gap (1.78 eV) and a lower LUMO energy level than the parent peropyrene without the fusion of the five-membered rings. In addition, the effects of the peri-fused pentagons on the aromaticity and molecular orbitals of 1 were evaluated by theoretical calculations. This work presents

• aromatic sextet theory (Figure 2e). Interestingly, the long bond length of a, b, c, and d (1.471–1.504 Å) indicated that the double bonds on the five-membered rings have a small contribution to the overall aromatic delocalization of the carbon framework [26]. In order to evaluate the aromaticity of 1, a

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• from the electronic nature of the fulvene, the reactant partner, as well as steric arguments. In addition, substituents that are distant, but conjugated to the fulvene group, influence the aromaticity of the molecule [69][71], ultimately allowing modification of the molecule’s reactivity for a given

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• level optimized and experimental geometry of THTAA and its derivatives show considerable loss of aromaticity within the quinoxaline moiety. Keywords: aromaticity; density functional calculations; heterocycles; hydrogen bonds; X-ray structures; Introduction Quinoxaline derivatives 1 – also called

• averaged distances from 1.363 to 1.367 Å (Table 1). The C1–C2 and C4–C5 distances vary between 1.447 and 1.421 Å, respectively, indicating poor conjugation through these bonds, as a result of a partial loss of the aromaticity of the central benzene ring. This feature is confirmed also by the deviation of

• charge along the both conjugated moieties (Table 1). The bonds of C1–C6 (1.469 Å) and C8–C13 (1.441 Å) are also elongated, indicating further loss of aromaticity within the dication. The planarity distortion is smaller than observed in 3, judging by the torsion angles C7–C6–C1–C14 and C7–C8–C13–C14

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• properties of this carbon are mainly ruled by orbital factors. Despite the carbon C2 in these species has a large positive charge (0.46–0.48 e) and a great orbital coefficient (17.3–26.3%), reactions of nucleophiles with this atom are less probable, since it leads to a loss of aromaticity of the

Cyclobutane dication, (CH₂)₄²⁺: a model for a two-electron four-center (2e-4c) Woodward–Hoffmann frozen transition state

• G. K. Surya Prakash and
• Golam Rasul

Beilstein J. Org. Chem. 2019, 15, 1475–1479, doi:10.3762/bjoc.15.148

• aromaticity. The four bridge-head p-orbitals overlap inward in a tetrahedral fashion involving two electrons. We have now extended our study to obtain information on the structure, stabilities and possible rearrangement pathways of the elusive cyclobutane dication. The species is an example of the simplest

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• are continuously red-shifted from DTT 1 to DSS 4 the more selenium atoms are present in the heteroacene (292–312 nm). This finding can be explained by the slightly lower aromaticity of the selenophene rings compared to thiophenes as a result from the slightly lower electronegativity (EN 2.55 vs 2.58

The activity of indenylidene derivatives in olefin metathesis catalysts

• Maria Voccia,
• Steven P. Nolan,
• Luigi Cavallo and
• Albert Poater

Beilstein J. Org. Chem. 2018, 14, 2956–2963, doi:10.3762/bjoc.14.275

• the phosphine release, and the relative stability of the corresponding metallacycle over classical ylidene ligands. Mayer bond orders and steric maps provide structural reasons for these effects, whereas NICS aromaticity and conceptual DFT confirm that the electronic parameters do not play a

• ]. In order to evaluate the change of the aromaticity of the phenyl ring of the indenylidene derivatives 3–6, we evaluated the aromaticity of the six-membered aryl rings, as well as the ring current on the five-membered ring by means of magnetic-based aromaticity criterion NICS (GIAO, see all NICS

• values in Supporting Information File 1). The 5-membered rings turn out to be non-aromatic, whereas the changes of the aromaticity of the phenyl rings are minimal. Species I, 2 and 3 are 0.151 and 0.083 ppm more aromatic than 1, nearly identical for the IMes systems 5 and 6, 0.166 and 1.117 ppm and more