A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• -8057 Zurich, Switzerland Department of Physical Chemistry, Faculty of Chemistry, University of Lodz, Pomorska 163/165, 90236 Łódź, Poland 10.3762/bjoc.17.108 Abstract In-situ-generated N-aryl nitrile imines derived from trifluoroacetonitrile efficiently react with polycyclic 1,4-quinones, yielding

• stability and could be isolated in moderate yield (53%). The presented method offers a straightforward access to hitherto little known trifluoromethylated polycyclic pyrazoles. All products were isolated as pale colored solids with medium-intensity absorption maxima in the range of 310–340 nm for

• trifluoroacetonitrile imines to give polycyclic pyrazole derivatives as exclusive products formed via spontaneous air oxidation of the initial [3 + 2]-cycloadducts. In contrast to some arylnitrile oxides and benzonitrile ylides, no competitive cycloaddition to the C=O bonds of the quinone molecule has been observed

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

• Ivan P. Mosiagin,
• Olesya A. Tomashenko,
• Dar’ya V. Spiridonova,
• Mikhail S. Novikov,
• Sergey P. Tunik and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105

• skeletons that are inaccessible via Pd-catalyzed cyclization. Keywords: arylation; pyridine; pyrrole; radical cyclization; tris(trimethylsilyl)silane; Introduction Polycyclic heteroaromatic molecules, which have a tunable electronic structure and excellent self-assembling properties, are highly desirable

• in materials science, especially in post-silicon electronics [1][2][3][4]. Though the remarkable progress in the synthesis of the polycyclic heteroarenes during the last two decades, further development of the existing methodologies is still required for broadening of the scope of polycyclic

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• Shakeel Alvi Rashid Ali Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, Okhla, New Delhi-110025, India; Phone: +91-7011867613 10.3762/bjoc.17.96 Abstract Design, synthesis and properties of polycyclic aromatic hydrocarbons (PAHs) has historically attracted a considerable

• metathesis, Ullmann-type coupling, Clauson–Kaas, and Van Leusen reactions as crucial transformations. Synthetic Strategy Basically, our endeavor toward the synthesis of truxene-based systems has been rooted in the development of new synthetic methodologies to assemble diverse polycyclic as well as

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• , delivering the corresponding regioisomers 8l and 8l’ in 62% with 1:1.6 ratio. Moreover, the naphthalene and tetrahydroisoquinoline-derived acrylamides were also compatible, giving the polycyclic products 8m and 8n in 77% and 70%, respectively. Additionally, protecting groups such as isopropyl, benzyl, or

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• derivative 57 in 72% combined yield (Scheme 18) [88]. In 2020, Pierce and co-workers developed a method for the synthesis of guanidinium alkaloid batzelladine D in enantiomeric and racemic form, along with a series of stereochemical analogues. The batzelladines are a family of polycyclic guanidinium

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• not estimated after each cycle [58]. In 2019, Lee et al. focused on the enantioselective desymmetrisation of polycyclic cyclohexenediones [59]. The variously substituted pyridine-oxazolines L9 and L12a,b were tested as ligands in combination with Pd(OAc)2 or Pd(TFA)2 (Table 31). As a suitable solvent

• -arylcyclopentanones to 1-tetralones [53]. Addition reaction of phenylboronic acid to 3-methyl-2-cyclohexenone catalysed by L9/Pd(TFA)2 in water [54]. Micellar nanoreactor PdL10c for the synthesis of flavanones [58]. Plausible catalytic cycle for the desymmetrisation of polycyclic cyclohexenediones by the addition of

• ]. Recyclisation of the polystyrene-supported Pd complex PdL11 [57]. Addition reactions of various boronic acids to polycyclic cyclohexenediones [59]. Addition reactions of arylboronic acids to 3-methyl-2-cyclohexenone catalysed by L13/Pd(TFA)2 [60]. Addition reactions of arylboronic acids to various enones

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• . Electrophilic substitution and further condensations give polycyclic systems, including oxazolo- and chromeno-fused analogues. Keywords: benzofuropyridines; benzoquinones; dibenzofurans; Meerwein reaction; metal-free synthesis; Introduction Dibenzofurans are important oxygen-containing heterocycles present in

• polycyclic derivatives was designed. The procedures towards such polycyclic building blocks include C–H-arylation strategies. In the classical Meerwein reaction, aryldiazonium salts are used as the reagents to couple aryl groups to electron-poor alkenes, and this process is assumed to proceed via a free

• regioselective in forming 16, which is a valuable building block for various condensation reactions to yield a diverse set of products, such as polycyclic fused nitrochromenes 21 as well as pyridopsoralens 22 and 23. All these novel scaffolds are interesting structures with potential medicinal applications, and

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• medicinally significant molecules. The review has been classified on the basis of the pharmacophores constructed by adopting the MWA-MCRs strategy. Review 1 Acridine Acridine is a polycyclic heteroarene with structural basis as anthracene in which one of the central carbon atoms is replaced by a nitrogen atom

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• Ramazan Kocak Arif Dastan Department of Chemistry, Faculty of Sciences, Atatürk University, Erzurum, 25240, Turkey 10.3762/bjoc.17.61 Abstract The synthesis of novel polycyclic π-conjugated dihydropyridazines, pyridazines, and pyrroles was studied. Dihydropyridazine dyes were synthesized by

• obtained gave absorbance and emission at long wavelengths. Keywords: dibenzosuberenone; inverse electron-demand Diels–Alder cycloaddition reactions; p-quinone methide; polycyclic π-conjugated dihydropyridazines; pyridazines; pyrroles; Inroduction Dibenzosuberone and dibenzosuberenone derivatives are

• exhibit photophysical properties such as photosensitization [13], fluorescence, and aggregation-induced emission (AIE) [14][15][16]. π-Conjugated polycyclic hydrocarbons (CPHs) containing polycyclic heteroaromatic molecules (PHAs) and aza-polycyclic aromatic hydrocarbons (aza-PAHs) have been attracting

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• derivatives with specific useful properties, creation of fundamentally new reagents for cycloaddition, and detailed studies on the multiaddition processes and the characteristics of polycyclic adducts. The majority of researchers developing methods for C60 functionalization prefer [2 + 1] cycloaddition

• ]. Representatives containing polycyclic aromatic systems based on phenothiazine 161 [144], carbazole 162 [145], and tetrathiofulvalenes 163 and 164 [146] and 1,1-binaphthalenes 165 and 166 [147] are known. They are shown in Figure 10. Various diaryl derivatives of C60 can also be obtained by this approach. Thus

• . Structures of complexes 63–65. Structures of spiromethanofullerenes 73–75. Quinone-substituted spiromethanofullerenes 82–84. Structures of 4-C61-phenylorganofullerenes 159 and 160. Structures of methanofullerenes containing aromatic polycyclic systems. 4,4-Diphenylfullerene derivatives 31, 32, 167, and 168

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• products, such as coffee cups or take-away containers, can be recycled into videocassette cases or office equipment. Incineration at a temperature below 1000 °C and insufficient air is believed to produce a mixture of volatile compounds, including hazardous polycyclic aromatic hydrocarbons, alkylbenzenes

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

• gram-scale syntheses of higher-order helicenes, double helical helicenes, and heterohelicenes. Keywords: acid; catalyst; cyclization; fluoroalcohol; helicenes; Introduction Helicenes are a class of polycyclic aromatic hydrocarbons (PAH) that consist of ortho-fused aromatic rings arranged in a helical

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

• ). Keywords: azine-fused helicenes; carbazole-based [6]helicenes; helical structures; Introduction [n]Helicenes are polycyclic aromatic molecules with nonplanar screw-shaped helical skeletons formed by n-ortho-fused benzene or other aromatic rings. Their helical structure is a consequence of the steric

• polycyclic π-systems additionally contributes to altering electronic structure and helps to fine tune optoelectronic properties [1][2][3][4][5][6][7][8][9][10][11][20][35][36][37]. The last decades highlighted heterohelicenes, incorporating one or two carbazole fragments, as a very attractive class of

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• congested arrays of stereocenters within the polycyclic framework of complex natural products usually require a sophisticated synthetic planning. This issue is not trivial because only a few strategies are available for the efficient synthesis of such an intriguing molecular architecture. More importantly

• 64% yield over three steps. The conversion of 138 to sinensilactam A (20) was achieved in two steps. Platinum-catalyzed [3 + 2] cycloaddition The platinum-catalyzed intermolecular [3 + 2] cycloaddition of propargyl ether derivatives and vinyl ether producing polycyclic indoles was disclosed by

• hydrodesulfurization with Raney nickel as catalyst and subsequent catalytic hydrogenation produced (±)-cuparene (13) in 90% yield. All-carbon [3 + 2] annulation in natural product synthesis The all-carbon [3 + 2] cycloaddition demonstrated the ability to assemble intricate polycyclic structures in the synthesis of

On the mass spectrometric fragmentations of the bacterial sesterterpenes sestermobaraenes A–C

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2020, 16, 2807–2819, doi:10.3762/bjoc.16.231

• initiate a cationic cyclisation cascade, leading to structurally highly complex and usually polycyclic terpenes in just one enzymatic transformation. The initially formed products are non-functionalised terpene hydrocarbons or, if the terminal cationic intermediate of the cyclisation cascade is trapped by

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• actinomycete origin. For example, salinosporamide A, an antitumor drug candidate in clinical trials, is a proteasome inhibitor with an unusual γ-lactam-β-lactone bicyclic core produced by marine Salinospora tropica [10]. Abyssomicin, another example of uncommon polycyclic frameworks, is an antibacterial

A new method for the synthesis of diamantane by hydroisomerization of binor-S on treatment with sulfuric acid

• Rishat I. Aminov and
• Ravil I. Khusnutdinov

Beilstein J. Org. Chem. 2020, 16, 2534–2539, doi:10.3762/bjoc.16.205

• reaction stops after the hydrogenation step giving endo-endo-pentacyclo[7.3.1.12,5.18,10.03,7]tetradecane in 68% yield with excellent selectivity (100%). Keywords: binor-S; diamantane; hydroisomerization; sulfuric acid; tetrahydrobinor-S; Introduction Among the highly diverse polycyclic and cage

• homologous series, has been poorly studied. The main cause of this situation is the lack of facile methods for its synthesis. In the literature, diamantane (1) is prepared by skeletal isomerization of strained С14Н20 polycyclic hydrocarbons [2][3][4][5][6][7]. In particular, the most suitable initial

• compounds for the preparation of diamantane are three isomeric polycyclic hydrocarbons C14H20 3а–с, which are obtained by hydrogenation of the norbornadiene dimer, heptacyclo[8.4.0.02,12.03,8.04,6.05,9.011,13]tetradecane (binor-S, 2). Binor-S is hydrogenated in the presence of a platinum catalyst (Н2PtCl6

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• ’ “Suman”, which means “Sunflower”), a beautifully simple yet much effective bowl-shaped C3-symmetric polycyclic aromatic hydrocarbon having three benzylic positions clipped between three phenyl rings in the triphenylene framework has attracted a tremendous attention of researchers worldwide. Therefore

• of the vital modes in metal binding and a range of π-conjugated planar systems having ηn-binding to metals have been reported. In contrast, buckybowls have multiple coordination sites for instance the positions available in the polycyclic architecture and also because of the presence of concave or

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• transformation widely used in the synthesis of polycyclic complex molecules. The intermolecular variant shows a wide alkyne scope, but in terms of the olefin counterpart is limited to the use of ethylene or strained alkenes, such as norbornene and norbornadiene. The high prevalence of five-membered ring systems

• of fluorine-containing compounds The utility of the Pauson–Khand reaction in the preparation of polycyclic compounds bearing both nitrogenated and cyclopentenone rings, two ubiquitous domains in drugs and natural products, has been reported in various contributions using 1,n-enynes, particularly 4

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• used similar disulfide-catalyzed [3 + 2] cycloaddition reactions for the synthesis of polycyclic frameworks. The irradiation of vinylcyclopropanes with alkenes or alkynes in the presence of dibutyl disulfide afford the desired bi- or tricyclic products with 54–88% yield (Scheme 2) [6]. In 2014, Maruoka

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• - and pyrrolo-fused polycyclic indoles is herein described, starting from 2-formylpyrrole and employing Diels–Alder and Heck arylation reactions. 3-(N-Benzyl-2-pyrrolyl)acrylates and 4-(pyrrol-2-yl)butenones underwent a highly endo-Diels–Alder cycloaddition with maleimides to furnish octahydropyrrolo

• [3,4-e]indoles, which served as precursors in the regioselective synthesis of aza-polycyclic skeletons via an intramolecular Heck arylation reaction. Through the latter reaction, the 3-(N-benzyl-2-pyrrolyl)acrylates give rise to 3-(pyrrolo[2,1-a]isoindol-3-yl)acrylates. A further oxidative

• aromatization of the polycyclic intermediates provides the corresponding polycyclic pyrrolo-isoindoles and isoindolo-pyrrolo-indoles. A theoretical study on the stereoselective Diels–Alder reactions, carried out by calculating the endo/exo transition states, revealed the assistance of non-covalent interactions

Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions

• Xiaoming Ma,
• Suzhi Meng,
• Xiaofeng Zhang,
• Qiang Zhang,
• Shenghu Yan,
• Yue Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106

• pyrrolidines II-b was less explored [27][28][29]. In recent years, our lab has reported a series of 1,3-dipolar cycloaddition-initiated methods for the synthesis of diverse heterocycles A–J bearing fused polycyclic rings such as tetrahydroepiminobenzo[b]azocines, tetrahydropyrrolobenzodiazepinones

A simple and easy to perform synthetic route to functionalized thienyl bicyclo[3.2.1]octadienes

• Dragana Vuk,
• Irena Škorić,
• Valentina Milašinović,
• Krešimir Molčanov and
• Željko Marinić

Beilstein J. Org. Chem. 2020, 16, 1092–1099, doi:10.3762/bjoc.16.96

• 54, 10000 Zagreb, Croatia NMR Centre, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia 10.3762/bjoc.16.96 Abstract In order to prepare novel polycyclic derivatives of bicyclo[3.2.1]octadiene systems fused with a thiophene ring, photochemical cyclization and aldol condensation

• the HRMS measurements is appreciated. Funding The University of Zagreb short term scientific support under the title “Synthesis and functionalization of novel (hetero)polycyclic photoproducts as cholinesterase inhibitors” is gratefully acknowledged.

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• -workers exploited the copper-catalysed asymmetric ring opening of polycyclic meso hydrazines with organoaluminium reagents (Scheme 13) [43]. This reaction followed a classical allylic substitution pathway. Interestingly, the organoaluminium reagents in this reaction did not only act as alkyl donors but

• oxabicyclic substrates with organolithium reagents (selected examples). Copper-catalysed ring opening of polycyclic meso hydrazines. Copper-catalysed ACA of Grignard reagents to alkenyl-substituted aromatic N-heterocycles. Copper-catalysed ACA of Grignard reagents to β-substituted alkenylpyridines. Copper

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• measurements show that helicene-like boomerangs may be usable as circularly polarized luminescent materials. Keywords: donor–acceptor systems; double C–H bond activation; helicenes; pyrroles; Introduction Nanographenes and other polycyclic aromatics as well as their heterocyclic analogues are typically