Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

• Beatrice Lansbergen,
• Catherine S. Meister and
• Michael C. McLeod

Beilstein J. Org. Chem. 2021, 17, 404–409, doi:10.3762/bjoc.17.36

• %. Naphthalene 6h and 2-pyridine 6i were also successfully obtained, however, the reactions with the 3- and 4-pyridines 5j and 5k resulted in complex mixtures from which no desired product, nor starting material, could be observed. The scope of this chemistry also extends to substrates with a shorter

Decarboxylative trifluoromethylthiolation of pyridylacetates

• Ryouta Kawanishi,
• Kosuke Nakada and
• Kazutaka Shibatomi

Beilstein J. Org. Chem. 2021, 17, 229–233, doi:10.3762/bjoc.17.23

• synthesizing substituted pyridines are in high demand in pharmaceutical and agricultural chemistry [1][2]. Because of the unique features of fluorine atoms, fluorinated functional groups have also been recognized as important substructures in the design of medicinally relevant compounds [3][4][5][6

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• to 4-nitrobenzaldehyde (2a). The product of this is the intermediate B, which favors the formation of the corresponding desired product 3a, as shown in Scheme 5. Conclusion In summary, this work provides a green and simple synthetic methodology for the synthesis of higher azaarenes from pyridines and

• clean process. A variety of aromatic aldehydes, including electron-donating, electron-withdrawing, as well as halogen groups was screened, affording the products in moderate to excellent yields. Azaarenes such as pyridines with various substitution patterns and a few quinolines were also reacted with

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• formation of tar-like products. 2,5-Bis(N-sulfonylamidino)pyridines Bis(thioamide) 1p containing a pyridine ring was found to react with sulfonyl azides 2a,c–f either in boiling propanol or in the absence of a solvent to form compounds 3aj–an bearing two N-sulfonyl amidine fragments connected to a pyridine

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• , USA 10.3762/bjoc.16.239 Abstract Imidazo[1,5-a]pyridines were efficiently prepared via the cyclization of 2-picolylamines with nitroalkanes electrophilically activated in the presence of phosphorous acid in polyphosphoric acid (PPA) medium. Keywords: cyclization; heterocycles; imidazo[1,5-a

• ]pyridines; nitroalkanes; polyphosphoric acid; Introduction It is hard to overstate the importance of imidazo[1,5-a]pyridines in modern organic and medicinal chemistry. Several natural alkaloids possessing this core were isolated from marine sponges, for example, cribrostatin 6 (Figure 1) [1][2][3]. The

• development of efficient synthetic methods to access imidazo[1,5-a]pyridines, with more than 120,000 individual compounds prepared to date. Most synthetic approaches rely on various cyclocondensations of nucleophilic (2-aminomethyl)pyridine precursors, introducing a new five-membered ring. Typically

One-pot multicomponent green Hantzsch synthesis of 1,2-dihydropyridine derivatives with antiproliferative activity

• Giovanna Bosica,
• Kaylie Demanuele,
• José M. Padrón and
• Adrián Puerta

Beilstein J. Org. Chem. 2020, 16, 2862–2869, doi:10.3762/bjoc.16.235

• contributions. As a result, such research has grown exponentially in the past decade [5][6]. The work conducted by the German chemist Arthur Hantzsch exploded in the synthetic interest in dihydropyridines and pyridines when the pharmacological usefulness of these compounds in medicine was discovered [7]. The

• source of nitrogen has also been varied from the classical use of ammonia. The most common nitrogen source reported in literature is ammonium acetate (3). Others include the use of oxahydrazines, primary amines, and urea. The oxidation of dihydropyridines to pyridines has been achieved using mild

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• state. 4-Substituted pyridines exhibit a distinguished correlation between basicity and coordination strength as axial ligands with Ni-porphyrins [12]. Hence, Hammet σ values might be used to predict and to systematically optimize the performance of the spin switch. In previous studies we have shown

• diamagnetic (or the paramagnetic) species in the two photostationary states. The intermolecular association constants of pyridines as axial ligands to Ni-porphyrins as a function of their para substituents usually follow the Hammett relationship [5][12]. Hence, the association constants should also be

• notorious problem of porphyrin-based spin switches. To kill two birds with one stone, we introduced acidic substituents in 4-position of the pyridines (1h (R = SH), 1j (R = COOH)). Deprotonation to the corresponding anions should increase the coordination power of the pyridine and increase the solubility of

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

• reaction to proceed. Jiang et al. developed a similar system for the enantioselective radical addition into 2-vinylazaarenes 122 using DPZ and either α-amino radicals [60] or ketyl radicals [61], with pyridines being well tolerated as substrates in this latter case (Scheme 17a). The same group also

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• pyridines via C–N, C–C, and C–S bond formations in a mixture of ethanol and H2O under ultrasound irradiation. The catalyst is characterized by XRD, FTIR, Raman spectroscopy, SEM, and EDAX analysis. The main advantages of this methodology include the wide substrate scope, cleaner reaction profile, short

• : benzimidazoles; dihydropyrimidinones; highly substituted pyridines; natural dolomitic limestone; ultrasound irradiation; Introduction Nitrogen heterocycles are recognized as “privileged medicinal scaffolds” because these compounds are found in a wide variety of bioactive natural products and pharmaceuticals [1

• ][2][3]. Among them, benzimidazoles, dihydropyrimidinones, and pyridines have emerged as promising and valuable structural units in many pharmaceutical lead compounds (Figure 1) [4][5][6][7][8][9]. Hence, there is a great need for the development of a green and sustainable synthetic route to the

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• , heterocycles such as, pyrroles (e.g., IV) [24], keto pyrroles (e.g., V) [25], pyridines (e.g., VI) [26], pyrrolotriazoles (e.g., VII) [27], and triazolobenzoxazonines (e.g., VIII) [28] result from MBH acetates (Scheme 1). From these synthetic elaborations, three successive steps are universally utilized: (i

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• cleavage and aromatization to give substituted pyridines 255 [75] (Scheme 49). In 1989, Kanaoka and co-workers further studied the photo [2 + 2] cycloadditions of thiobarbiturates 256–258, whose skeletons consisted of a combination of a thioamide and an amide or a thioamide (two-imides system), and olefins

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• SET. After the reduction, a fragmentation affords the desired amidyl radicals together with the corresponding pyridines. The reduction potential of such species was around −0.75 V vs Ag/Ag+, depending on the substitution pattern. This scaffold was employed recently by the Hong group to achieve an

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• medicinal chemistry [19][20]. A number of clinically used drugs and clinical candidates, such as zolpidem, alpidem, saripidem, zolimidine, necopidem, and GSK812397 contain the imidazo[1,2-a]pyridine scaffold [21][22][23][24][25][26]. 3-(Arylselanyl)imidazo[1,2-a]pyridines IV were reported to act as

• potential antioxidants and showed antiproliferative activity [27][28]. Consequently, they have attracted much attention, and methods for their syntheses have been actively pursued. A powerful method for the synthesis of 3-selanylimidazo[1,2-a]pyridines involves the C–H selenation using imidazopyridine and a

• ]pyridines, which are isomers of imidazo[1,2-a]pyridines, with Se powder [34]. However, in this reaction, selenides and diselenides were generated in ratios of approximately 1:1; hence, an efficient selective synthesis has not yet been achieved. Inspired by the aforementioned reports and our continuing

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

• azaenolate with reactive Michael acceptors in a follow-up study [45]. While pyridines are among the most important classes of heterocyclic moieties that occur in many bioactive molecules, such as natural products, pharmaceuticals, and agrochemicals, the initial report by the Harutyunyan group did not include

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• , meta and para positions. Moreover, the methodology also showed effectiveness for heteroarenes such as pyridines and benzothiazoles. The authors also evaluated the use of NiTPP as a photoredox catalyst for other transformations involving both oxidative and reductive quenchings. The NiTPP-catalyzed

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• proceeding at the C2 carbon atom of the seleniranium cation 2 with dithiocarbomates [31], thiourea [32], alcohols [42], functionalized organic acids [43][44], functionalized pyridines [45], ammonium thiocyanate [46], and mercapto benzazoles [40] were developed (Scheme 4). The new methodology of a

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• lithium halogen elimination, halide migration, and ring-opening reactions [56][57]. Butylphosphines are also formed alongside the main product, and in most cases pure phosphine pyridines are obtained using column chromatography followed by extractions adding to the number of synthesis steps. This method

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• dehydrogenative coupling adopting oxygen atom as the linker [12][13][14][15][16][17]. In particular, bisbenzofuro[2,3-b:3′,2′-e]pyridines (BBZFPys) were found to exhibit intense photoluminescence with relatively high quantum efficiency (Φflu up to 0.70), indicating that the BBFZPy scaffold may serve as a key

• unsymmetrically substituted pyridines 3a–c in high yields. We then examined the oxidative cyclization of these compounds under the standard conditions adopting Pd(TFA)2 (30 mol %, TFA = trifluoroacetate) and AgOAc (3.0 equiv) as catalyst and oxidant, respectively, in pivalic acid as solvent (Scheme 3). Since the

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• Strukturchemie, Universitätsstraße 1, D-40225 Düsseldorf, Germany 10.3762/bjoc.15.262 Abstract Starting from substituted alkynones, α-pyrones and/or 1H-pyridines were generated in a Michael addition–cyclocondensation with ethyl cyanoacetate. The peculiar product formation depends on the reaction conditions as

• well as on the electronic substitution pattern of the alkynone. While electron-donating groups furnish α-pyrones as main products, electron-withdrawing groups predominantly give the corresponding 1H-pyridines. Both heterocycle classes fluoresce in solution and in the solid state. In particular

• emission solvatochromism. Also a donor-substituted α-pyrone shows pronounced aggregation-induced emission enhancement. Keywords: cyclocondensation; DFT calculations; fluorescence; heterocycles; 1H-pyridines; α-pyrones; Introduction A high sensitivity and precise tuneability of fluorescence colors are

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• pyridinyl motif. In fact, only two pyridinyl silicon rhodamines (13 and 14) are known so far, although halogenated pyridines are highly interesting for further functionalization or vector conjugation by nucleophilic aromatic substitution. For the implementation of the dihalogenated pyridine motif into the

• ., tetrasubstituted pyridines [48]) with substitution patterns difficult to obtain otherwise [49][50][51]. Results and Discussion Approaches to synthesize the pyridinyl silicon rhodamine 15 Table 2 and Scheme 3 summarize the experimental results towards the synthesis of the radiofluorinatable near-infrared dye 15. To

• HD reactions of nicotinic acids can be found in the literature. In fact, if 2,3-dihalogenated pyridines are used for the HD rearrangement as starting materials, only methyl groups are tolerated as carbon substituents. Optical properties of the pyridinyl silicon rhodamine 15 The dihalogenated

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

• 38% yield; whereas the use of 2-chlorobenzonitrile afforded 12 in 62% regioselectivity and in 34% yield. In both cases, partial conversions of the aryl chlorides were observed. Pyridines and quinoline heterocycles are very important structures in pharmaceutical chemistry as more than 100 currently

• marketed drugs contain these units. Therefore, the reactivity of 3- and 4-bromo-substituted pyridines, 3-bromoquinoline and 4-bromoisoquinoline for the α-arylation of lilolidine was also studied. In all cases, the desired N-containing coupling products 16–19 were obtained in high regioselectivities and in

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• constructing tetracyclic aromatic heterocycles containing selenium. For example, the reaction of 2-(2-iodophenyl)indoles with selenium powder in the presence of CuO as catalyst resulted in benzoselenopheno[3,2-b]indole derivatives [14]. The reaction of 2-(2-haloaryl)imidazo[1,2-a]pyridines with selenium using

• a CuI catalyst for the synthesis of benzo[b]selenophene-fused imidazo[1,2-a]pyridines occurred smoothly [15][16]. Performing these types of reactions without the addition of a transition metal catalyst is more challenging, but would alleviate the environmental burden of removing and disposing of the

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• reaction [14]. Recently, several hydroxyalkylation reactions followed by alkylation of arenes have been reported involving heterocycle-based superelectrophiles: pyridines, thiazoles, quinolines, isoquinolines, pyrazines, pyrazoles, imidazole and furans, bearing a formyl (carbonyl) group [15][16][17][18][19

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

• been given much attention in various research fields, such as the discovery of lead compounds in medicinal chemistry, or combinatorial chemistry [95][96]. Copper-catalyzed synthetic protocols Ghosh and Mishra [97] have successfully reported the synthesis of imidazo[1,2-a]pyridines in a three-component

• -benzenedicarboxylate), Puthiaraj and co-workers have unprecedently discovered the catalytic activity of this metal-organic framework (MOF) for the synthesis of imidazo[1,2-a]pyridines [100]. The three-component, one-pot reaction between 1, 3 and nitromethane (10, Scheme 5) involved an intermolecular aza-Michael

• heterogeneously catalyzed synthesis of imidazo[1,2-a]pyridines from 3 and ketones 20 has been reported (Scheme 7) [101]. Titania-supported CuCl2 (CuCl2/nano TiO2) played the role of catalyst in this transformation under aerobic conditions. Titania support helped in recyclability of the copper salt to four

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

• ]triazolo[4,3-a]pyridines was accessed through a 5-exo-dig-type cyclization of chloroethynylphosphonates and commercially available N-unsubstituted 2-hydrazinylpyridines. In addition, 3-methylphosphonylated [1,2,4]triazolo[4,3-a]quinolines and 1-methylphosphonylated [1,2,4]triazolo[3,4-a]isoquinolines were

• 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

• imidazo[1,2-a]pyridines [4]. In continuation of this study, herein we report an effective approach to the synthesis of new phosphonylated triazolopyridine derivatives by reacting chloroethynylphosphonates with 2-hydrazinylpyridines. The triazolopyridine ring is a structural fragment that is present in a