Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• reaction is facilitated under microwave irradiation and can be extended to the preparation of an imidazo-fused (benzo)thiazole skeleton 34 starting from (benzo)thiazol-2-ones instead of pyridin-2-ones. Moreover, the Cu(OTf)2 in [bmim]BF4 can be recovered and reused for multiple processes. The key step of

• presence of catalytic amounts of Cu(OTf)2 lead to the formation of the products through formation of one C–C bond and three C–N bonds (Scheme 26) [44]. The same procedure allows a more general scope, giving access to imidazo[1,2-a]pyrimidine, imidazo[1,2-a]pyrazine and imidazo[2,1-b]thiazole derivatives

5th International Symposium on Synthesis and Catalysis (ISySyCat2023)

• Anthony J. Burke and
• Elisabete P. Carreiro

Beilstein J. Org. Chem. 2024, 20, 2704–2707, doi:10.3762/bjoc.20.227

• Suzuki couplings and the reduction of the thiazole moiety to 2,3-dihydro[1,3]thiazolo[4,5-b]pyridines, a crucial intermediate, using BH3⋅NH3 and tris(pentafluorophenyl)borane as a Lewis acid, followed by treatment with formic acid. Gillie et al. reported the synthesis of a laterally fused N-heterocyclic

Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments

• Daria A. Burmistrova,
• Andrey Galustyan,
• Nadezhda P. Pomortseva,
• Kristina D. Pashaeva,
• Maxim V. Arsenyev,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2024, 20, 2378–2391, doi:10.3762/bjoc.20.202

• -triazole, thiazole, or pyridine were synthesized by the reaction of 3,5-di-tert-butyl-o-benzoquinone or 3,5-di-tert-butyl-6-methoxymethylcatechol with different heterocyclic thiols. The S-functionalized catechols were prepared by the Michael reaction from 3,5-di-tert-butyl-o-benzoquinone and the

• -derivatives of thiazole or pyridine, this process leads to the formation of the corresponding thioethers with a methylene linker. At the same time, thiolated 1,3,4-oxadiazole or 1,2,4-triazole undergo alkylation at the nitrogen atom in the reaction with 3,5-di-tert-butyl-6-methoxymethylcatechol to form the

• heteroatoms (nitrogen, sulfur, selenium, tellurium, etc.) as well as redox-active functional groups allows one to vary significantly the biological activity of such compounds. Heterocyclic molecular blocks are widely used in medicinal chemistry [12]. Thiazole, oxadiazole, triazole, imidazole, and other

O,S,Se-containing Biginelli products based on cyclic β-ketosulfone and their postfunctionalization

• Kateryna V. Dil and
• Vitalii A. Palchykov

Beilstein J. Org. Chem. 2024, 20, 2143–2151, doi:10.3762/bjoc.20.184

• the postmodification of the Biginelli products [2]. Both approaches were tested in this work. We used Hantzsch-type thiazole synthesis for postmodification of product 2a. By employing 2-bromoacetophenone, bromomalononitrile and 2-bromo-1-tetralone we obtained condensed thiazoles 3–5 in 67–88% yields

• using slightly modified methods described [37][38][39]. We also applied desulfurization to obtain products 6 and 7 [40][41] (Scheme 4). While the Hantzsch thiazole synthesis is well documented from a synthetic and mechanistic point [42][43] and do not need discussion, more desulfurizations and

• of other sulfones of both synthetic and biological importance can be obtained by using the in this work reported efficient, multicomponent and green protocol. We postfunctionalized the typical Biginelli product using Hantzsch-type thiazole chemistry and desulfurization. Assessing drug-likeness, we

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• 11 are formed via Hantzsch's thiazole synthesis. After acidic deprotection to thiazolylhydrazines 12, these react with enolates of 2,4-diketoesters, which are intermediaries prepared in a separate reaction vessel, yielding the corresponding (thiazol-2-yl)pyrazoles 8. However, hydrazines are not

• tolerated in this consecutive four-component reaction, as the 1,3,4-thiadiazine synthesis competes with the thiazole synthesis. Salicylaldehydes 14 and 4-hydroxy-6-methyl-2H-pyran-2-one (16) can also be used to produce 1,3-dicarbonyl compounds 18 by Knoevenagel condensation and subsequent cyclization. This

• organic synthesis. For instance, hydrazinecarbothioamide (40) can be used to synthesize bisheterocycles. Mohamed et al. were able to combine Hantzsch thiazole and Knorr pyrazole synthesis with this building block. Thiazolyl-pyrazolyl-chromenes 43 were synthesized in good yields from substituted 3

Negishi-coupling-enabled synthesis of α-heteroaryl-α-amino acid building blocks for DNA-encoded chemical library applications

• Matteo Gasparetto,
• Balázs Fődi and
• Gellért Sipos

Beilstein J. Org. Chem. 2024, 20, 1922–1932, doi:10.3762/bjoc.20.168

• results, thiazole 2b, benzothiazole 2i and benzimidazole 2t react very well with sodium nitrite in an acidic environment (Scheme 6, red section). Among the various subclasses of compounds, pyrazole 2l exhibited a high reactivity using t-BuONO and EtONa in ethanol (Scheme 6, red section). On the other hand

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

• studies. Thiazoles: 2-Thiazolylethylamine was characterized as a more selective and potent histamine H1 agonist [70]. Based on this, Govoni et al. [71] analyzed the pharmacological profile of several histamine H1 antagonists, with a section covering thiazole-based compounds. 2-(Thiazol-4-yl)ethylamine (99

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

• -free conditions at room temperature for 2 h [16]. Although thiamine had already been reported to be effective in other chemical transformations and its role in carbonyl activation in vivo through its thiazole ring is well known, no mechanism of action in the GBB condensation was proposed by the authors

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• . The pbt cluster, responsible for the synthesis of GE2270, encodes four MTs. Among these, only PbtM4 is an O-MT. It methylates thiazole D, resulting in a C-methylene-O-methyl-thiazole. The other MTs of the pbt cluster, one N-MT (PbtM1) and two C-MTs (PbtM2 and PbtM3) [64], will be discussed in later

• encoded in the pbt cluster of P. rosea. The thiopeptide GE2270 encoded by pbt undergoes further regioselective modification through C-methylation of thiazoles. The two rSAM MTs PbtM2 and PbtM3 methylate thiazole E and thiazole D, respectively [64]. PbtM2 and PbtM3 show substantial sequence similarities to

• -methylthiazole through C-methylation on an unactivated sp2 carbon centre of thiazole, likely thiazole 4. The analysis of Tbtl´s activity revealed its predominant independence from the leader peptide. Only one residue, Asn3, in the precursor peptide was shown to be crucial for activity [133]. Streptomyces

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• with potential for further modification by cross-coupling. The full scope of the transformation can be found in Supporting Information File 1, Schemes S2 and S3 [45]. Concerning scope limitations, the azido-alkynylation of vinyl-pyridine 1b was unsuccessful and thiazole 1c only afforded 18% of the

Synthesis and biological profile of 2,3-dihydro[1,3]thiazolo[4,5-b]pyridines, a novel class of acyl-ACP thioesterase inhibitors

• Jens Frackenpohl,
• David M. Barber,
• Guido Bojack,
• Birgit Bollenbach-Wahl,
• Ralf Braun,
• Rahel Getachew,
• Sabine Hohmann,
• Kwang-Yoon Ko,
• Karoline Kurowski,
• Bernd Laber,
• Rebecca L. Mattison,
• Thomas Müller,
• Anna M. Reingruber,
• Dirk Schmutzler and
• Andrea Svejda

Beilstein J. Org. Chem. 2024, 20, 540–551, doi:10.3762/bjoc.20.46

• lead structure with ample space for structural variations. By formally replacing one pyridine moiety of 1,8-naphthyridine 4 by a five-membered thiazole unit, we have identified thiazolo[4,5-b]pyridine 5 as a strong inhibitor of acyl-ACP thioesterase, which has further been confirmed via an X-ray co

• 6). This result indicated that borohydride reagents were able to activate the thiazole moiety in [1,3]thiazolo[4,5-b]pyridines, leaving the pyridine unit unchanged. While sodium cyanoborohydride afforded a comparable result, albeit with lower conversion, the use of silane reagents at elevated

• temperature [23] led to the cleavage of the thiazole ring, furnishing disulfides 18b and 18c exclusively (Table 1, entries 7–10). Interestingly, the reaction of 5 with ammonia borane at elevated temperature in toluene [20] furnished three reaction products with a low yield since 2,3-dihydro[1,3]thiazolo[4,5-b

Cycloaddition reactions of heterocyclic azides with 2-cyanoacetamidines as a new route to C,N-diheteroarylcarbamidines

• Pavel S. Silaichev,
• Tetyana V. Beryozkina,
• Vsevolod V. Melekhin,
• Valeriy O. Filimonov,
• Andrey N. Maslivets,
• Vladimir G. Ilkin,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2024, 20, 17–24, doi:10.3762/bjoc.20.3

• 1,2,3-triazole ring, either an additional pyrimidinedione, 4-nitroimidazole, isoxazole, 1,3,4-triazole, 2-oxochromone or thiazole ring, has been developed. The process was facilitated by a strong base and includes the cycloaddition reaction of 3,3-diaminoacrylonitriles (2-cyanoacetamidines) to

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

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

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

• 2017, the Co-catalyzed CDC for the C5-alkylation of oxazole/thiazole substrates with ethers afforded functionalized ethers in moderate to good yields (Scheme 29a) [91]. In 2016, Du et al. demonstrated that the construction of C(sp2)–C(sp3) bonds also proceeded smoothly with coumarins and cyclic or open

• tetrahydropyrans. CDC of thiazole with cyclic ethers. Cu(I)-catalyzed oxidative alkenylation of simple ethers. Cross-dehydrogenation coupling of isochroman C(sp3)–H bonds with anisole C(sp2)–H bonds. Pd(OAc)2/Cu(OTf)2-catalyzed arylation of α-C(sp3)–H bonds of ethers. Cu-catalyzed C(sp3)–H/C(sp2)–H activation

Synthesis of imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazines via a base-induced rearrangement of functionalized imidazo[4,5-e]thiazolo[2,3-c][1,2,4]triazines

• Dmitry B. Vinogradov,
• Alexei N. Izmest’ev,
• Angelina N. Kravchenko,
• Yuri A. Strelenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2023, 19, 1047–1054, doi:10.3762/bjoc.19.80

• esters are also suitable substrates for the reaction. In this case hydrolysis and thiazole ring expansion were accompanied with the change of the thiazolotriazine junction type from thiazolo[3,2-b][1,2,4]triazine to thiazino[2,3-c][1,2,4]triazine. Keywords: N,S-heterocycles; ring expansion; skeletal

• closer location in structures 5 (Figure 3). In the downfield region of the 13C NMR spectra registered without proton decoupling for isomeric acids 4a and 5a, the carbon atom doublets of the carboxyl groups, carbonyl groups of thiazole (for 4a) or thiazine (for 5a) cycles, as well as multiplets of

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• and 3 is the lack of two proton signals associated with the thiazoline moiety. Instead, the proton spectrum of 3 features a signal at δH 8.55 (H-13). The HMBC correlations linking H-13 to 163.3 ppm (C-12) and 146.3 ppm (C-14) indicate the presence of a thiazole rather than a thiazoline moiety. This

• carbon atoms C-13 and C-14 of the thiazole moiety, the loss of one degree of unsaturation and a loss of 2 Da in mass, it can be deduced that compound 5 possesses an alcohol function. Compound 6 (0.4 mg) was obtained as a brown oil. It possesses a molecular ion at m/z 291.1165 [M + H]+, which suggests a

• metabolites that were recovered in this study share a phenolic moiety with a thiazole or thiazoline substituent. This motif is present in many siderophores, e.g., in pyochelin [26], yersiniabactin [28], agrochelin [29], micacocidin [30], the Massilia-derived massiliachelin [18], as well as in piscibactin [31

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• thiazole synthesis and elimination to nitriles) were identified. The key factor that enables the successful Eschenmoser coupling reaction involves the optimum balance in acidity of nitrogen and carbon atoms of the intermediary α-thioiminium salts. Keywords: Eschenmoser coupling reaction; Hantzsch thiazole

• with a α-haloketone or α-haloester II. The initially formed α-thioiminium salt III can undergo either a base-catalyzed elimination to give nitrile X and thiol IX [10][11][12] or cyclization to give a thiazole XIII or thiazolone XI depending on the substituent at the carbonyl group Y. Both side

• Y: alkyl, aryl). This reaction pathway represents the well-known Hantzsch thiazole synthesis [13][14][15][16][17][18][19][20][21]. If the imidothioate IV is further deprotonated [10][11][12] at nitrogen using a strong base (e.g., NaOH/H2O or EtONa/DMF are strong enough), then another intramolecular

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• ,t and 4x,y). Lastly, we explored a few heterocycles that resemble imidazo[1,2-a]pyridine to vindicate the generality of this method. Gratifyingly, 6-phenylimidazo[2,1-b]thiazole, 2-phenylbenzo[d]imidazo[2,1-b]thiazole, and 2-phenylimidazo[1,2-a]pyrimidine participated well under the standard

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• alkenyl heteroarenes [61]. The aza-enolates were trapped with various Michael acceptors such as unsaturated ketones, esters, and amides (Scheme 25) [62]. The authors noted a strong substrate dependence of this process. The trapping reaction worked best with benzoxazole-derived substrate, while thiazole

One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides

• Arisu Koyanagi,
• Yuki Murata,
• Shiori Hayakawa,
• Mio Matsumura and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 1479–1487, doi:10.3762/bjoc.18.155

• benzamidine hydrochloride G. The reaction of D with amines may require an excessive amount of D due to competition between aminophenol and the byproduct aniline. A similar mechanism is considered for the construction of benzimidazole and thiazole rings. On the other hand, the released bismuth moiety, Ph3Bi=S

• , and achieved the syntheses of 2-aryl- and 2-alkylbenzazoles, such as oxazoles, imidazoles, and thiazole, in satisfactory yields. The protocol was successfully applied to the synthesis of tafamidis, a clinically used drug for transthyretin amyloid inhibition. The reaction is simple, can be performed in

A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

• pharmaceutical activities such as antimicrobial [2][3], antiviral [4], antitumor [5][6], anti-inflammatory [7][8] and so on. Moreover, as a type of important intermediates, thiazole is of prime importance in organic synthesis [9][10] which is used extensively in the preparation of flavors [11], polymers [12

• ], dyes [13], etc. These important features of thiazoles have driven intense interests in their facile synthesis [14][15][16][17]. Among various synthetic routes to the thiazole unit, the Hantzsch condensation of α-halo ketones (dielectrophiles) with various thioureas (dinucleophiles) should be the most

• and would lead to a large quantity of waste. Considering the importance of thiazoles in synthetic and medicinal chemistry, the development of greener and more atom economic processes for the thiazole synthesis has become increasingly necessary with growing awareness of environmental constraints

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• photophysical changes, have some common structural characteristics. For instance, heterocyclic units containing a nitrogen atom such as pyridine and thiazole, are one of the key structural features either in small molecules or polymers. Thus, the introduction of nitrogen with lone pairs of electrons in

• reaction. In order to clarify the coordination reaction of nitrogen atoms, Bazan’s group designed a conjugated polymer containing pyridine and thiazole groups and small molecule 15 (Figure 8) and compared the 1H NMR spectra and 19F NMR spectra after the addition of 1 equivalent B(C6F5)3 at various

• small molecule 15 containing pyridine and thiazole groups reported by Bazan et al. and pyridine groups-containing diketopyrrolopyrroles (DPP) 16–18 investigated by Huang et al. (a) 1H NMR spectra in the aromatic region and (b) 19F NMR spectra of compound 15 (top) and the mixture with 1 equivalent B(C6F5

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• -capping. The resulting compounds were treated with chloroacetic anhydride and then with thiazole. After anion exchange the chiral thiazolium salts (R)-35a/b, which differ in the chain length of the axle, were obtained in 9%/42% overall yield (see Figure 8a). For comparison, a rotaxane containing a BINOL

• -based axle and an achiral macrocycle was also synthesized. This design was chosen to investigate the difference between a covalently and a mechanically linked chiral unit with regard to the chiral induction in asymmetric catalysis. By acylative end-capping, followed by introduction of the thiazole unit

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• combining thiazole, selenazole, pyrazole, indazole, and indole moieties with both carboxyl functional groups and cycloaminyl units [27][28][29][30][31]. In recent decades, various methods of constructing 1,2-oxazole ring systems have been developed [1][2][3][4][5][6][7][32]. The two primary pathways to 1,2

• the range of 14.4–14.7 Hz, while the 3JHN values were in the range of 1–3 Hz [42][43]. The coupling constants 13C,15N of a series of 15N-labeled pyrazoles gave 1JCN values of 8–11 Hz, while 2JCN were less than 2 Hz [44]. The 15N-labeled 1,2-thiazole moiety was readily determined by measuring the