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

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

• effective. This method afforded the products with high selectivity and it could be extended to a variety of substrates, such as benzoxazole, benzothiazole, oxazole, and even acidic hydrocarbons and aniline. Fukuzama and co-workers [91] accomplished the C–H carboxylation of benzoxazole and benzothiazole

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• benzothiazole, in which benzothiazole compounds have higher reactivity and regioselectivity than thiazole. In 2014, Lei et al. successfully realized the copper-catalyzed oxidative alkenylation of simple ethers to construct allyl ethers in the presence of di-tert-butyl peroxide and KI (Scheme 10) [60]. The

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Nucleophile-induced ring contraction in pyrrolo[2,1-c][1,4]benzothiazines: access to pyrrolo[2,1-b][1,3]benzothiazoles

• Ekaterina A. Lystsova,
• Maksim V. Dmitriev,
• Andrey N. Maslivets and
• Ekaterina E. Khramtsova

Beilstein J. Org. Chem. 2023, 19, 646–657, doi:10.3762/bjoc.19.46

• targeted cancer therapy development. Keywords: 1,4-benzothiazine; 1,3-benzothiazole; 1H-pyrrole-2,3-diones; nitrogen heterocycle; sulfur heterocycle; Introduction Pyrrolo[2,1-b][1,3]benzothiazole (PBTA) is an angularly fused sulfur and nitrogen-containing heterocyclic scaffold. Its derivatives are

• ] and reactions of 3-acyl-2,3-dihydro-1,3-benzothiazole-2-carbonitriles with acetylenedicarboxylate (Scheme 1, entry 9) [4]. The second group of approaches to the PBTA scaffold is an annulation of o-aminothiophenol with a pyrrolothiazole moiety (Scheme 2). It includes catalytic cascade reactions of o

• 1 (Scheme 5). Firstly, FPDs 1 bear a 1,4-benzothiazine moiety that is known to be prone to undergo a ring contraction reaction to afford the corresponding 1,3-benzothiazole derivatives under the action of nucleophiles [39][40][41][42], oxidizing agents [43][44][45][46][47][48] or ultraviolet

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• -alkylarenesulfonamides, N-fluoropyridinium salts and derivatives, N-fluoroquinuclidium salts, N-fluoro-trifluoromethanesulfonimide, N-fluoro-sultams, N-fluoro-benzothiazole dioxides, N-fluoro-lactams, N-fluoro-o-benzenedisulfonimide, N-fluoro-benzenesulfonimide, 1-alkyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts, N

• fluorinating agents for an enantioselective fluorination was demonstrated (Scheme 22). 1-10. N-Fluoro-3,3-dimethylbenzothiazole dioxide In 1989, Lang and co-worker developed the saccharin-derived N-fluorosultam N-fluoro-3,3-dimethyl-2,3-dihydro-1,2-benzothiazole-1,1-dioxide (10-2) from the known precursor 10-1

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• /hydroxy)phenyl [26], 3/4-(N-((dimethylamino)methylidene)aminosulfonyl)phenyl [26][27], and sulfonamido-substituted benzothiazole [28] attached as an additional head are also reported in this review article. Literature data revealed that most of the double-headed nucleosides have the first nucleobase

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• later to form differently substituted 2-guanidinobenzimidazoles and 2-guanidinobenzothiazoles, respectively, with good to excellent yields (Scheme 11A) [30][31]. The efficiency of the reaction process usually follows the order: benzothiazole > benzimidazole > benzoxazole. The lower yields obtained with

• benzothiazole and benzimidazole-based sulfonylguanidine compounds were derived by the sulfonylation of the corresponding 2-guanidinobenzazoles and assayed as potential antimelanoma agents (Scheme 11C) [33]. Of note, a dearomatization of the benzothiazole ring was observed while grafting a sulfoguanidinyl group

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• derivative 38 initiated by an EDA complex. Synthesis of spiropyrroline derivative 40 initiated by an EDA complex. Synthesis of benzothiazole derivative 43 initiated by an EDA complex. Synthesis of perfluoroalkyl-s-triazine derivative 45 initiated by an EDA complex. Synthesis of indoline derivative 47

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• compounds ethyl (E)-3-(methylsulfanyl)acrylate and 2-(methyldisulfanyl)benzothiazole were identified and their structures were verified by synthesis. Feeding experiments with [methyl-2H3]methionine, [methyl-13C]methionine and [34S]-3-(dimethylsulfonio)propanoate (DMSP) resulted in the high incorporation

• into dimethyl trisulfide and S-methyl methanethiosulfonate, and revealed the origin of the methylsulfanyl group of 2-(methyldisulfanyl)benzothiazole from methionine or DMSP, while the biosynthetic origin of the benzothiazol-2-ylsulfanyl portion could not be traced. The heterocyclic moiety of this

• menaquinones [58]. Sulfur-containing compounds included dimethyl trisulfide (37), released by all six species, S-methyl methanethiosulfonate (38), 2-acetylthiazole (39), and benzothiazole (40), the latter also in the extracts from all six strains. In addition, the extracts from the three species C. marinus, C

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

• , affording biaryl species 161. Using this strategy, several trifluoromethyl ketones 162 and alcohols 163 bearing heteroaryl substituents (i.e., benzothiazole, quinoline, isoquinoline, benzimidazole, or imidazole) prone to be protonated were elegantly converted into the corresponding alcohols 163 and biphenyl

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• -established benzoxazole and benzothiazole ligands. Such complexes have then been used for α-functionalisations [117], RCAs [118], and cycloaddition reactions [119]. As much of Meggers work has been summarised previously [120], here we will include only recent examples from each reaction class. If an

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• the catalyst SiO2@H3PW12O40 [21], the reaction of tetracarbonyl compounds with o-aminothiophenol (1a) [22][23], the reaction of copper(II) chelate of ethyl pentafluorobenzoylpyruvate with o-aminothiophenol (1a, one example) [24] and the reaction of DMAD with 6-nitro-1,3-benzothiazole (one example) [25

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

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• ., formamide) and ethers through C–H activation using various five- and six-membered heteroarenes (e.g., benzothiazole) and employing benzaldehyde (8) as the photoinitiator [56]. This protocol was compatible with both C(sp3)–H activation (N-alkyl C–H bonds of amides or Cα–H bonds of ethers) and C(sp2)–H

• activation (carbonyl C–H bonds of formamides). Some of the amides or ethers found to be compatible with this method are shown in Scheme 26. A wide range of heteroarenes 114 was also found compatible with this method, including substituted benzothiazole substrates, substituted benzimidazoles, and thiazoles

• (Scheme 27b). The sulfate radical then reacted with formamide (106) to produce the carbamoyl radical 125, which could perform a nucleophilic addition to the C-2 position of the protonated benzothiazole 126. A deprotonation, followed by an oxidation, most probably by the intermediates 121 and 122, could

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• , compound 36 could be recycled and used in seven subsequent cycles. A further example of a silica-supported CuAAC catalyst was reported by Moghadam et al. (Scheme 7) [29]. In this study, the bis(benzothiazole)-substituted pyridine ligand BTP (41) was synthesized through the condensation of 2-aminothiophenol

• . Subsequently, a range of hybrid molecules, including triazole–benzimidazoles 50–53, triazole–benzothiazole 54, and triazole–benzoxazole 55, was prepared under the above-mentioned conditions (Scheme 8). The benefits of this catalytic system were mild reaction conditions, low catalyst loadings, a diverse set of

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• substituents (Scheme 5), and (v) the rate-determining step (i.e., breaking of the C–H bond) was suggested to follow a first-order kinetic isotope effect (KH/KD = 5). As such, a library of benzothiazole derivatives was reported using this methodology, and a plausible mechanism is shown in Figure 9. Synthesis of

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

• Andreas Boelke,
• Yulia A. Vlasenko,
• Mekhman S. Yusubov,
• Boris J. Nachtsheim and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223

• , benzothiazole- and pyrazole-substituted hydroxy(phenyl)-λ3-iodanes (12 and 6–8) show an excellent relation between thermal stability and reactivity, in particular in direct comparison with well-known benziodoxolones. We can also conclude that the pseudocyclic forms of aryl(phenyl)-λ3-iodanes should be the

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

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• Abstract Four benzothiazolium crown ether-containing styryl dyes were prepared through an optimized synthetic procedure. Two of the dyes (4b and 4d) having substituents in the 5-position of the benzothiazole ring are newly synthesized compounds. They demonstrated a higher degree of trans–cis

• aggregated much faster than its methyl-substituted analogue 4b. From another hand the substituent in the 5-position of the benzothiazole heterocycle sterically hinders the rotation of the alkylsulfo-anchoring group and thus plays the role of a controller with regard to its direction towards the crown ether

• . This finding is a resemblance to the results from reference [24] where the 5-methoxy-substituted benzothiazole styryl-crown ethers demonstrated higher quantum yields of trans-to-cis photoisomerization. Insight from electronic structure calculations To rationalize the experimental findings, we performed

Metal-free C–H mercaptalization of benzothiazoles and benzoxazoles using 1,3-propanedithiol as thiol source

• Yan Xiao,
• Bing Jing,
• Xiaoxia Liu,
• Hongyu Xue and
• Yajun Liu

Beilstein J. Org. Chem. 2019, 15, 279–284, doi:10.3762/bjoc.15.24

• potassium hydroxide and DMSO. This novel protocol is featured by direct C–H mercaptalization of heteroarenes and a simple reaction system. Keywords: benzothiazole; benzoxazole; C–H functionalization; mercaptalization; 1,3-propanedithiol; Introduction Both 2-mercaptobenzothiazoles and 2

• -catalyzed C–H thiolation of benzothiazole or benzoxazole with a disulfide and a thiol provides easy access to the corresponding sulfides [26][27][28][29][30][31][32][33][34]. However, the examples using C–H functionalization for preparing 2-mercaptobenzoxazoles or 2-mercaptobenzothiazoles are still rare. In

• ]. Therefore, we envisioned that aliphatic dithiol may be able to work as thiol source in the C–H mercaptalization of benzothiazole and benzoxazole as well, leading to the formation of 2-mercaptobenzothiazole and 2-mercaptobenzoxazole, respectively. We tested our hypothesis using benzothiazole (1a) as model

Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• . Rearomatization via hydrogen atom abstraction by the former generated superoxide radical anion leads to the desired 2-substituted benzothiazole. The authors observed a green colour of the reaction mixture indicating the formation of [Ru(bpy)3]3+. Therefore, they suggest an oxidative quenching cycle, but an

• photoexcited [Ru(bpy)3]2+* leading to [Ru(bpy)3]+ and a thiyl radical intermediate. Radical addition to the aromatic anilide moiety, single-electron oxidation and further deprotonation forms the desired 2-substituted benzothiazole by rearomatization. Both the regeneration of the [Ru(bpy)3]2+ by single-electron

Halogen-containing thiazole orange analogues – new fluorogenic DNA stains

• Aleksey A. Vasilev,
• Meglena I. Kandinska,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• David Sucunza,
• Juan J. Vaquero,
• Obis D. Castaño,
• Stanislav Baluschev and
• Silvia E. Angelova

Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283

• also noteworthy that the presence of the Br substituent in the C-5 position of the benzothiazole system does not influence the positions of the absorption maxima (cf. 5a vs 5c and 5b vs 5d) but does lead to a decrease in the molar absorptivity (up to 20% from 5b to 5d). The addition of dsDNA to the dye

• for deactivation of the excited state [43]. The replacement of the hydrogen atom at the C-5 position in the benzothiazole side of the molecules with a bromo substituent does not have any significant influence on the fluorescence of dyes 5c and 5d, which is similar to its effect on the absorption

• spectra and is in contrast to the by Armitage et al. observed influence of the replacement of hydrogen with fluorine atom in the benzothiazole ring [43]. Photostability The photostability of all dyes in the series was evaluated in acetonitrile with irradiation at 254 nm with a mercury lamp in equal