2-Heteroarylethylamines in medicinal chemistry: a review of 2-phenethylamine satellite chemical space

• Carlos Nieto,
• Alejandro Manchado,
• Ángel García-González,
• David Díez and
• Narciso M. Garrido

Beilstein J. Org. Chem. 2024, 20, 1880–1893, doi:10.3762/bjoc.20.163

• a heteroaromatic ring bound to the C3 position of the GABA chain is well tolerated for activity. Thiophenes: Back to the MAO-A scenario, Vallejo et al. [14] also developed thienyl-substituted isopropylamines 13–16, which were found to bind to MAO-A with IC50 values in the micromolar range with

Mono or double Pd-catalyzed C–H bond functionalization for the annulative π-extension of 1,8-dibromonaphthalene: a one pot access to fluoranthene derivatives

• Nahed Ketata,
• Linhao Liu,
• Ridha Ben Salem and
• Henri Doucet

Beilstein J. Org. Chem. 2024, 20, 427–435, doi:10.3762/bjoc.20.37

• ]thiophenes [25]. In these reactions, the C–H bonds at the C2 and C3 positions of the thienyl unit were functionalized. In order to obtain acenaphtho[1,2-c]thiophenes and related compounds that are not easily accessible [33][34][35][36][37][38], we investigated the reactivity of three 5-membered heteroarenes

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• ]. In addition to anilino groups, a myriad of donor entities, including urea-substituted phenyl groups [18][19], carbazoles [20], phenothiazines [21][22], thiophenes [23][24][25][26], tetrathiafulvalenes (TTFs) [27], extended TTFs [28], ferrocenes [27][29][30][31][32][33][34][35][36][37][38][39][40][41

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

• pyridine ring and two thiophenes inverted and fused with two pyrrole nitrogen atoms. The macrocycles exhibited facile oxidations, indicating their electron-rich nature, and demonstrated selective sensing of Cu2+ ions. Conclusion and Outlook The construction of new macrocycles has been a driving force for

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• efficient Lewis acid catalyst (Scheme 10) [50]. In the procedure, oxidative cleavage of one S–N bond and 1,2-sulfur migration afforded π-conjugated 6-substituted 2,3-diarylbenzo[b]thiophenes 16. A plausible mechanism is shown in Scheme 11. The coordination of AlCl3 with the phthalimide/succinimide unit of 1

• ‑mediated electrophilic cyclization of aryl alkynoates. Construction of 6-substituted benzo[b]thiophenes. Plausible mechanism for construction of 6-substituted benzo[b]thiophenes. AlCl3‑catalyzed cyclization of N‑arylpropynamides with N‑sulfanylsuccinimides. Synthetic utility of AlCl3‑catalyzed cyclization

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• example, when esters 1a are subjected to Lewis acid-induced denitration, highly electron-deficient enones (reaction b) [4] are obtained. The latter compounds are highly reactive and undergo reaction with, e.g., mercaptoacetaldehyde affording thiophenes (reaction c) [5] or with activated (hetero)aromatic

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• blocks, including their unsaturated and oxidized derivatives (Figure 1a). The chemistry of fully unsaturated 1,4-dithiins have received a good deal of attention in synthesis [19][20][21][22][23], in particular as these heterocycles constitute non-aromatic (and non-planar) analogues of thiophenes that

• reported for vinyl sulfides, including dihydrodithiin 13 (Scheme 5a) [36]. In fact, Parham has found that fully unsaturated dithiins can undergo this electrophilic formylation, but at the same time also undergo a ring contraction and an aromatizing desulfurization to yield thiophenes as the main formylated

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

• , compound 6 features a quinoidal antiaromatic [10] structure. Antiaromaticity is reported to further decrease the energy gap. The electron-rich dithiole units provide an extended tetrathiafulvalene structure, leading to compound 7 exhibiting two reversible one-electron oxidations [25]. Fused thiophenes have

• asymmetric analogue, which is only alkylated on one side (9), achieved OFET hole mobilities up to 17.22 cm2 V−1 s−1 in polycrystalline films obtained by thermal evaporation [28]; both examples prove the potential of thienoacenes in OFETs. ITIC, a system with fused thiophenes, in combination with donor

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• heteroarenes such as thiophenes, benzofurans, furans, and indoles were found suitable substrates and afforded the desired products with high chemo- and site-selectivity. A possible mechanism for the reaction was also described. The first step of the catalytic cycle involves the formation of a cationic complex

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• heteroarenes were much poorer, with pyrroles and thiophenes giving yields of ≈20% or less and benzofuran and benzothiophene failing to produce any product. Interestingly, a cyclopentanone-derived substrate (120) failed to yield the corresponding α-amino cyclohexanone 121 under the standard conditions used for

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• alkyl group, direct dehydration was not possible because of blocking. Later they reported a similar transformation of thiiranes to provide a wide variety of substituted thiophenes. They had synthesized substituted thiophenes 133b starting from thiiranes 131b via cyclization utilizing the catalytic

• amount of HgO and dil. H2SO4 at room temperature [95]. Initially, the Hg(II)-salt-catalyzed the formation of intermediate 132b which further proceeded by dehydration to yield thiophenes 133b as the final product (Scheme 39). Starting with 1-alkynyl-2,3-epoxy alcohols 135, Marson et al. had reported a Hg

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• , Vasilyev and Khoroshilova investigated the superacid-promoted activation of α-(trifluoromethyl) silyl ethers exhibiting a thiophene core [73]. At 0 °C, thiophenes 72-Cl and 72-Br undergo electrophilic dimerization, affording a mixture of 73-Cl and 73-Br (Scheme 20). When the reaction was cooled to −60 °C

• < T < −40 °C in the presence of aromatic nucleophiles, thiophenes 72-Cl and 72-Br could be converted into 74-Cl and 74-Br derivatives via a side-chain arylation reaction. When the reaction was conducted at −40 °C, the reactivity was shown to be governed by the nature of the halogen atom. For the

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

• 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

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

• Paola Vitale,
• Luciana Cicco,
• Ilaria Cellamare,
• Filippo M. Perna,
• Antonio Salomone and
• Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

• ][3]. As part of our ongoing research in DES chemistry, we reported recently on the preparation of valuable heterocycles by (a) nucleophilic substitution (tetrahydrofuran derivatives) [4], (b) heterocyclodehydration reactions (2-aminoimidazoles, 2-pyrazinones, benzoxazines, thiophenes) [5][6][7][8

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

• heteroarene coupling partners. Indeed, furans, thiophenes, and pyrroles underwent selectively the non-directed C–H functionalization, delivering a diversity of heteroaryl–aryl coupling products. Remarkably, the continuous-flow technique rendered this transformation perfectly suited for large-scale and rapid

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• thiophenes as substituents. It appears that the sequence of the building blocks is less important than their nature and quantity. The same regularity holds true (with less precision) for the most red-shifted absorption bands of SyTh1 and AsTh2 (CFs have 18 nm difference in band positions); both DAEs

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• functionalization of heteroarenes such as thiophenes, furans, pyrroles and indoles [14][15], this methodology has been widely applied for the preparation of new aryl-substituted heteroarenes [16][17][18][19][20][21]. Several results dealing with the C–H bond functionalization of indoles have been reported allowing

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

• the synthesis of dithienothiophene 1, which is mostly built up by oxidative dehydrocoupling of 3,3’-dithienyl sulfide or ring-closure reactions of brominated thiophenes with ethyl mercaptoacetate, are described in literature [24]. For comparability to the selenophene-containing triacenes 2–4, we

• 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

• slightly less aromatic than thiophenes with increasing number of selenium atoms a continuous decrease of the anodic peak potential was observed going from 2 (0.84 V) over 3 (0.82 V) to 4 (0.80 V). In comparison, dithienopyrrole (DTP), a corresponding nitrogen-bridged 2,2’-bithiophene, with a peak potential

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• thiophenes possessing donor and acceptor substituents (-Ph/-PhOMe, -Ph(CF3)2/-PhNMe2, and -Ph(CF3)2/-PhOMe) have been investigated [8][40]. However, sufficient separation of the oxidation waves in order to assure a fully stepwise oxidation process is difficult to achieve and could only be realized in the

• attached to the 5-position of the thiophenes (e.g., -PhOMe). For all compounds, the major isomer obtained in the synthesis [33] is shown. Proposed mechanism for the oxidative cyclization of sDTE66-Me. Upon two-fold oxidation, both open isomers cyclize to the dication C2+. This dication can reversibly be

One-pot synthesis of epoxides from benzyl alcohols and aldehydes

• Edwin Alfonzo,
• Jesse W. L. Mendoza and
• Aaron B. Beeler

Beilstein J. Org. Chem. 2018, 14, 2308–2312, doi:10.3762/bjoc.14.205

• aldehydes worked well including para-nitro (7), ortho-methyl (8), and para-methoxy groups (9). Other notable examples include heterocycles, such as basic pyridines, thiophenes, and furans 16–18. Additionally, aliphatic 13 and 20 and alkenyl aldehydes 21 performed well providing synthetically useful

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• protocol for coupling simple five-membered heterocycles to substituted benzenes, using Eosin Y as the photocatalyst, starting from arenediazonium salts (Scheme 6) [47]. The scope of the reaction is limited to N-Boc-pyrroles, furans and a couple of simple substituted thiophenes with respect to the

• potential to be of interest if explored further. The good physical chemical properties of thiazoles, as well as their ability to act as isosteres to thiophenes, carbonyls and pyrazoles [49][50] make this scaffold an intriguing novel motif. 2.3 C(sp2)–X bond formation The obvious extension after considering

• the formation of aromatic thioethers by functionalising C–H bonds of imidazo[1,2-α]pyridines and benzo[d]imidazo[1,2-b]thiophenes using Eosin B and sulfinic acids (Scheme 8) [51]. The manipulated heterocycles, particularly the imidazopyridines, are motifs which are commonly encountered in medicinal

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• –CF3COOH, TMSCl/NaI failed to reduce secondary OH groups in diheteroaromatic systems and the reduction with H2/Pd/C-ZnBr2 was very slow [32]. On the other hand, some rigid diarylmethanols were successfully reduced to benzo[b]indeno[2,1-d]thiophenes using the Et3SiH–CF3COOH system which was reported in the

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• significant antibacterial activity against Gram-positive bacterial strains [50]. Several other distamycin analogs were synthesized by replacing one or more pyrrole rings with other heterocycles such as pyrazoles [51], benzofurans [52], thiazoles, thiophenes, imidazole and oxazoles [53] in order to establish a

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Keshaba N. Parida,
• Gulab K. Pathe,
• Shimon Maksymenko and
• Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

• -membered heterocycles such as thiophenes, furans, and pyrroles. Consequently, numerous multistep approaches to unsymmetrical 1,4-dicarbonyl compounds involving, e.g., SN2-type displacements [1] or highly functionalized substrates such as β-ketoesters [2][3] or β-ketosulfones [4] have been developed

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• , Korea Translational Research Branch, National Cancer Center, 323 Ilsan-ro, Ilsandong-gu, Goyang-si Gyeonggi-do 10408, Korea 10.3762/bjoc.14.16 Abstract Herein, we describe a novel approach for the practical synthesis of tetrasubstituted thiophenes 8. The developed method was particularly used for the

• facile preparation of thienyl heterocycles 8. The mechanism for this reaction is based on the formation of a sulfur ylide-like intermediate. It was clearly suggested by (i) the intramolecular cyclization of ketene N,S-acetals 7 to the corresponding thiophenes 8, (ii) 1H NMR studies of Meldrum’s acid

• those of others. Keywords: 5-(heterocyclic)thiophenes; one-pot sequential synthesis; sulfur ylide; tetrasubstituted thiophene; Introduction Since the discovery of stable sulfonium ylides 1 in 1930 [1] and the pioneering work of several research groups during the 1960s (2 and 3) [2][3][4][5][6][7][8][9