Challenge N- versus O-six-membered annulation: FeCl₃-catalyzed synthesis of heterocyclic N,O-aminals

• Giacomo Mari,
• Lucia De Crescentini,
• Gianfranco Favi,
• Fabio Mantellini,
• Diego Olivieri and
• Stefania Santeusanio

Beilstein J. Org. Chem. 2024, 20, 1412–1420, doi:10.3762/bjoc.20.123

• intermediates through selective FeCl3-catalyzed intramolecular N-annulation. Keywords: α-aminoacetals; fused-ring systems; heterocyclic hemiaminals; heterocyclic N,O-aminals; multicomponent reactions; Introduction N-Fused heterocycles are ubiquitous within crucial molecules, including biologically active

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• ultimate elimination of chalcogen fragments upon thermal activation, photoirradiation and electron exchange. Keywords: arenes; chalcogens; extrusion; fused-ring systems; precursor approach; Introduction π-Conjugated polycyclic compounds (π-CPCs), including polycyclic aromatic hydrocarbons and their

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

• a subsequent Glaser–Hay coupling reaction, a RA acceptor unit was introduced to provide a DTF-IF-RA donor–acceptor scaffold with a low-energy charge-transfer absorption and multi-redox behavior. Keywords: alkynes; chromophores; fused-ring systems; heterocycles; redox chemistry; Introduction

An accelerated Rauhut–Currier dimerization enabled the synthesis of (±)-incarvilleatone and anticancer studies

• Tharun K. Kotammagari,
• Sweta Misra,
• Sayantan Paul,
• Sunita Kunte,
• Rajesh G. Gonnade,
• Manas K. Santra and
• Asish K. Bhattacharya

Beilstein J. Org. Chem. 2023, 19, 204–211, doi:10.3762/bjoc.19.19

• intermediate A tetrahydrofuran intermediate B with cis-fused ring systems is formed as seen in the existing literature [7]. A proton transfer of enolate moiety B yields another enolate C followed by the β-alkoxy elimination [17] of intermediate C to form intermediate D. The intermediate D on protonation leads

Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

• Yara Cristina Marchioro Barbosa,
• Guilherme Caneppele Paveglio,
• Claudio Martin Pereira de Pereira,
• Sidnei Moura,
• Cristiane Storck Schwalm,
• Gleison Antonio Casagrande and
• Lucas Pizzuti

Beilstein J. Org. Chem. 2022, 18, 1079–1087, doi:10.3762/bjoc.18.110

• first reported synthesis of pharmacologically interesting N-thiazolyl derivatives. Keywords: fused-ring systems; hydrazones; indazoles; intramolecular cyclization; N-heterocycles; Introduction 1H-Indazoles are important scaffolds due to the prevalence in compounds with biological activity [1], such as

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• ] and Gaussview [74] programs. A frequency calculation showed that all frequencies are positive indicating that a minimum was found [75]. The calculations showed that the middle section consisting of seven fused ring systems is nearly planar (Figure 10). The thiophene groups carrying the ethylhexyl

• compound, EtH-T-DI-DTT, consisting of seven, fused ring systems, with an electron-rich central DTT core, flanked by electron-withdrawing keto groups. Absorption studies in solution and in the solid state show strong aggregation of the molecules in films. EtH-T-DI-DTT shows excellent redox stability with

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• as starting materials. However, since 3,5-unsubstituted, 4-substituted indoles have two potential ring-closure sites (indole C3 and C5 positions), such reactions in principle can furnish either or both of the indole 3,4- and 4,5-fused ring systems. This Commentary will briefly highlight the issue by

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

• Attila Márió Remete,
• Tamás T. Novák,
• Melinda Nonn,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

• -Fluor®, CH2Cl2, 0 °C to rt, 27 h, 61% yield of two isomeric bromofluorinated products in a ≈11:10 ratio). We continued our synthetic explorations with unsaturated fused ring systems. Our first choice was the easily accessible N-benzylated cis-tetrahydrophthalic imide 7. Unfortunately, both bromo- and

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

• facilitates the synthesis of cyclopentenone-fused ring systems, which tend to be difficult to construct. The Pauson–Khand reaction has also been used as a key step in the synthesis of a number of biologically-relevant compounds, including fluorine-containing piperidine-fused cycles. Of course, where the

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• synthesized in a similar manner. The presence of a NO2 group in the starting hydrazinylpyridine induces a Dimroth-type rearrangement leading to 2-methylphosphonylated [1,2,4]triazolo[1,5-a]pyridines. Keywords: cyclization; fused-ring systems; nitrogen heterocycles; phosphorylation; rearrangement

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

• , In(OTf)3, results in the regioselective nucleophilic attack at both carbonyl groups forming benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones instead. Keywords: cyclization; fused-ring systems; indium; radical; regiodivergent; Introduction β-Ketoesters are versatile substrates frequently used in

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• formation of a 2,3-diarylindole was observed under the same conditions. Keywords: arylation; fused-ring systems; indole formation; palladium catalysis; sultams; Introduction The sulfonamide functional group stands out as one of the most important pharmacophores. At the same time, cyclic sulfonamides

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• construction of diverse fused ring systems. Other classical pericyclic processes that may potentially occur in fulvene fragments (electrocyclic and ene reactions, sigmatropic rearrangements and shifts) have received less attention, most probably with the only exception of the Claisen rearrangement [16

Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• -rearrangement metathesis (RRM) as the key steps. This approach delivers tri- and tetracyclic sulfones with six (n = 1), seven (n = 2) or eight-membered (n = 3) fused-ring systems containing trans-ring junctions unlike the conventional all cis-ring junctions generally obtained during the RRM sequence

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• functionalisation. Methodologies have been developed which facilitate the preparation of MPTTFs and BPTTFs independently substituted in almost all of the positions indicated in Figure 2. This ranges from the addition of simple alkyl, acyl or aryl substituents [13][19][26][27][28] to the preparation of fused ring

• systems [11][27], to the incorporation of MPTTFs and BPTTFs into more complex molecular architectures such as macrocycles [8][9][14], calix-pyrroles [1][10][11], calixarenes [29] and porphyrins [30]. Note that for MPTTFs, R1 and R2 can be either the same or different. Here, we present recent developments

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• (+)-vincadifformine (Scheme 14) [106]. The key step in the synthesis was an iminium ion cascade reaction that formed the fused ring systems by coupling 3,3-disubstituted tetrahydropyridine 57 with indole derivative 58. The former coupling partner was derived from chiral α-quaternary lactam 60, which was constructed

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part II: Iridomyrmecins

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• chiral centers complicates a stereoselective synthesis despite the small size of the molecule. Several methods have been published for the preparation of optically active cis-fused bicyclic iridoid lactones [7][8][9][10], whereas only a few syntheses of trans-fused ring systems have been reported [11

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• 2,2'-pyrrolylpyridines revealed 20 hits, all with cis geometry, discounting rigid fused-ring systems and one sterically hindered di-tert-butyl system; the corresponding absolute torsion angles ranged from 0 to 25°, mean value 7.5°. The molecular packing of 1 (Figure 2) is determined by a classical

Alkoxide-induced ring opening of bicyclic 2-vinylcyclobutanones: A convenient synthesis of 2-vinyl-substituted 3-cycloalkene-1-carboxylic acid esters

• Xiufang Ji,
• Zhiming Li,
• Quanrui Wang and
• Andreas Goeke

Beilstein J. Org. Chem. 2012, 8, 650–657, doi:10.3762/bjoc.8.72

• or acid derivatives makes this transformation a good supplementary method for the well-established Johnson–Claisen rearrangement. Keywords: alkoxide; cyclobutanones; esters; fused ring systems; ring opening; Introduction A great variety of methods are available for the synthesis of cyclobutane

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

• Raymond C. F. Jones,
• Abdul K. Choudhury,
• James N. Iley,
• Mark E. Light,
• Georgia Loizou and
• Terence A. Pillainayagam

Beilstein J. Org. Chem. 2012, 8, 308–312, doi:10.3762/bjoc.8.33

• condensation to give new 3-alkenyl-4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridine-4-ones, which are masked forms related to the acylpyridone natural products. Keywords: aldol reaction; fused-ring systems; heterocycles; isoxazole; metalation; pyridone; Introduction The 3-acyl-4-hydroxypyridin-2-one moiety 1

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• investigated in this reaction, and the corresponding enone products 2 were isolated in good yields. They employed the alkyne–carbonyl metathesis in the preparation of fused ring systems and obtained two six-membered bicyclic products. However, if the original ring was five- or eight-membered, the reaction