A Se···O bonding catalysis approach to the synthesis of calix[4]pyrroles

• Qingzhe Tong,
• Zhiguo Zhao and
• Yao Wang

Beilstein J. Org. Chem. 2022, 18, 325–330, doi:10.3762/bjoc.18.36

• to the synthesis of calix[4]pyrroles. In the presence of 5 mol % selenide catalyst, calix[4]pyrrole products were obtained in moderate to good yields at room temperature. The experimental results showed that both bidentate and monodentate catalysts were catalytically active in the condensation

Synthesis and bioactivity of pyrrole-conjugated phosphopeptides

• Qiuxin Zhang,
• Weiyi Tan and
• Bing Xu

Beilstein J. Org. Chem. 2022, 18, 159–166, doi:10.3762/bjoc.18.17

• controlling cell fate. Keywords: cells; enzyme; N-terminal; peptides; pyrroles; self-assembly; Introduction Biomacromolecular assemblies have received considerable attention recently in the field of biomaterials [1][2][3][4][5][6][7], among which peptides are of particular interest because of their unique

• shown nucleobases, as the heteroaromatic groups, are able to act as the N-capping group for EISA of phosphopeptides [67]. In this study, we chose to examine a different type of heteroaromatic group, pyrroles, because pyrrole is adaptable for solid-phase synthesis [68] so that it is feasible to conjugate

• multiple pyrroles to phosphopeptides. In addition, pyrrole has yet to be incorporated in peptides for EISA, though oligomeric pyrroles have been extensively explored for binding nucleic acids [68]. Based on a naphthyl-capped phosphopeptide (Nap-ffpy, 1), we conjugated heteroaromatic dipyrrole or tripyrrole

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• methodology was extended to the carbosilylation of olefins with carbon nucleophiles 108 including indoles, pyrroles, and 1,3-dicarbonyls. The scope of the reaction was broad and could tolerate a variety of functional groups; however, electron-deficient alkenes afforded the products in slightly diminished

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• combination of acidic α-carbon atoms, isocyano groups, and sulfonyl moieties [18]. In general, TosMIC undergoes base-mediated 1,3-dipolar cycloadditions with activated alkenes to provide pyrroles as products [18] (Scheme 1A). Recently, alternative functionalizations using TosMIC as a tosyl source of

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• of prolinol silyl ether (cat. 120) and benzoic acid (A1) catalysts to bring about reaction between 3-formyl-substituted indoles or pyrroles 118 and diverse electrophiles, including carbonyls, imines and other Michael acceptors (Scheme 5) [69]. The reaction with secondary amines occurred via the

• . Asymmetric synthesis of chiral N-functionalized heteroarenes. Asymmetric cascade aza-Michael−aldol reactions of α,β-unsaturated ketones with pyrroles. Intramolecular aza-Michael addition of conjugated ketones. Intramolecular enantioselective aza-Michael addition. Asymmetric aza-Michael addition of 4

• chiral N-triflylphosphoramide. Aza-Michael addition of primary amines to β-trifluromethyl-β-phenylnitroolefin catalyzed nitrogen heterocyclic carbene. Asymmetric aza-Michael additions of pyrroles to protected (E)-4-hydroxybut-2-enals. Asymmetric aza-Michael addition of purine bases to aliphatic α,β

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

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• enaminones as both nucleophiles and electrophiles have frequently been exploited in the synthesis of heterocyclic products, including pyrroles and related systems [22][23][24][25][26][27][28]. Nonetheless, encouraged by the ease of access to pyrrole-containing products of type 12 and their potential

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• powerful nitrogen source for the synthesis of various N-heterocycles, such as isoquinolines, quinolines, pyridines, pyrroles, indoles, azoles, and azepines [40][41][42][43][44][45]. 1,3-Enyne, as a powerful Michael acceptor, is a wonderful synthon for the synthesis of N-heterocycles via tandem addition and

• functionalized pyridines and pyrroles. Review Synthesis of pyridines via tandem annulation of 1,3-enynes In 2015, Reddy and co-workers reported the synthesis of substituted pyridines via Lewis acid-mediated aza-annulation of 2-en-4-ynyl azides 1 (Scheme 1) [49]. They discovered that Ag-mediated intramolecular

• also found that the aza-annulation could be carried out under iodine-mediated electrophilic annulation reaction conditions to give 5-iodo-3,6-disubstituted pyridines 3 as the major products, occasionally with a small amount of 2-acylated pyrroles 4. The proposed mechanism for the Ag-catalyzed aza

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

• Ivan P. Mosiagin,
• Olesya A. Tomashenko,
• Dar’ya V. Spiridonova,
• Mikhail S. Novikov,
• Sergey P. Tunik and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105

• ][4][5][6][7][8][9][10][11][12][13]. Pyrroles with vicinal o-bromophenyl and heteroaryl substituents, which are readily accessible via reactions of the corresponding 2H-azirines and phenacylcycloiminium ylides [14][15][16][17][18][19], are excellent precursors for various fused aza-heteroaromatics via

• -bromophenyl-substituted pyrroles into 7-oxa-2a1-azabenzo[b]-cyclopenta[pq]pleiadenes [30]. However, an attempt to use AIBN/Bu3SnH for the cyclization of pyrrole 1a to compound 3a only led to a tarring of the reaction mixture, regardless of the temperature (70–110 °C, MeCN) and the protocol for mixing the

• parameters are drawn at 50% probability level. Molecular structure of compound 17a, displacement parameters are drawn at 50% probability level. Retrosynthetic analysis of heterocycles A and B. Free-radical cyclization of N-protected and N-unprotected pyrroles 1a and 2. Synthesis of 2H-pyrido[2,1-a]pyrrolo

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• substituted pyrrole-2-aldehydes to 5-azaindole transformation during a base-catalyzed imination reaction [31]. However, we envisioned that our methodology might be strategically applied towards the synthesis of substituted γ-carbolines as a C-3 nucleophilic attack is more favored in indoles than in pyrroles

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• irradiation under solvent-free conditions. The library of compounds proved to be active as xanthine oxidase inhibitors with the most potent molecule showcasing IC50 = 4 μM (Scheme 21). 5 Pyrroles Pyrroles are five-membered heterocycles consisting of four carbon atoms and a nitrogen atom. The pyrrole ring is

• found to be abundant in a plethora of lead molecules and marketed drugs like atorvastatin (57), elopiprazole (58), isamoltane (59) and tolmetin (60, Figure 5) [59][60]. The diverse pharmacological activities of pyrroles enlivened Kumar and co-workers [61] to report a facile and eco-friendly microwave

• -assisted four-component reaction involving chromene-aldehyde (61), amines 32, acyclic 1,3-diketones 54 and nitromethane using silica-gel-supported polyphoshoric acid as catalyst under neat conditions for the synthesis of tetra-substituted pyrroles 62. A comparative study of the protocol employing the

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• precursors in denitrogenative transannulation reactions under metal-catalysed conditions to form other heterocycles such as functionalized pyrroles, imidazoles and pyridines (Scheme 1b) [11][12][13]. The traditional method for the synthesis of triazole unit is the Huisgen 1,3-dipolar cycloaddition between

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• Ramazan Kocak Arif Dastan Department of Chemistry, Faculty of Sciences, Atatürk University, Erzurum, 25240, Turkey 10.3762/bjoc.17.61 Abstract The synthesis of novel polycyclic π-conjugated dihydropyridazines, pyridazines, and pyrroles was studied. Dihydropyridazine dyes were synthesized by

• also obtained by H-shift isomerization following the inverse electron-demand Diels–Alder reaction of tetrazines with p-quinone dibenzosuberenone. Then these pyridazines were converted to the corresponding pyrroles by reductive treatment with zinc. It was observed that all the dihydropyridazines

• obtained gave absorbance and emission at long wavelengths. Keywords: dibenzosuberenone; inverse electron-demand Diels–Alder cycloaddition reactions; p-quinone methide; polycyclic π-conjugated dihydropyridazines; pyridazines; pyrroles; Inroduction Dibenzosuberone and dibenzosuberenone derivatives are

Synthesis of N-perfluoroalkyl-3,4-disubstituted pyrroles by rhodium-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles with terminal alkynes

• Olga Bakhanovich,
• Viktor Khutorianskyi,
• Vladimir Motornov and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 504–510, doi:10.3762/bjoc.17.44

• Prague, Czech Republic 10.3762/bjoc.17.44 Abstract The rhodium-catalyzed transannulation of N-perfluoroalkyl-1,2,3-triazoles with aromatic and aliphatic terminal alkynes under microwave heating conditions afforded N-perfluoroalkyl-3,4-disubstituted pyrroles (major products) and N-fluoroalkyl-2,4

• -disubstituted pyrroles (minor products). The observed selectivities in the case of the reactions with aliphatic alkynes were high. Keywords: pyrrole; transannulation; rhodium carbene; triazole; Introduction Pyrroles are known to be important structural moieties appearing in natural products, synthetic drugs

• of pyrroles to the 3,4-disubstituted derivatives is challenging because an electrophilic aromatic substitution of pyrroles or the metalation of N-substituted pyrroles and the subsequent reaction with electrophiles take place in position two of the ring [6][7]. Recently, N-sulfonyl-1,2,3-triazoles

Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• electrophilic activation and hydrolysis of the resulting electron-rich pyrroles in an overall N-acylation/C(7a) hydroxylation. This transformation is central to a synthesis of legonmycins A and B that requires just three laboratory operations from commercially available proline derivative 15. It is noteworthy

Three-component reactions of aromatic amines, 1,3-dicarbonyl compounds, and α-bromoacetaldehyde acetal to access N-(hetero)aryl-4,5-unsubstituted pyrroles

• Wenbo Huang,
• Kaimei Wang,
• Ping Liu,
• Minghao Li,
• Shaoyong Ke and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2920–2928, doi:10.3762/bjoc.16.241

• , School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 1037 Luoyu road, Hongshan District, Wuhan 430074, China 10.3762/bjoc.16.241 Abstract N-(Hetero)aryl-4,5-unsubstituted pyrroles were synthesized from (hetero)arylamines, 1,3-dicarbonyl compounds, and α

• pyrrole-3-carboxamides. In the presence of 1.2 equiv of KI, a polysubstituted pyrazolo[3,4-b]pyridine derivative was also successfully synthesized. Keywords: acid catalyst; [1 + 2 + 2] annulation; KI; pyrazolo[3,4-b]pyridine; pyrroles; Introduction Among nitrogen-containing heterocycles, pyrroles have

• ][18] are some of the commonly used approaches for the construction of pyrrole scaffolds. Additionally, the biocatalytic synthesis of substituted pyrroles was also developed [19]. Though sustained efforts have been achieved to develop efficient synthetic methods for the preparation of this structural

UV resonance Raman spectroscopy of the supramolecular ligand guanidiniocarbonyl indole (GCI) with 244 nm laser excitation

• Tim Holtum,
• Vikas Kumar,
• Daniel Sebena,
• Jens Voskuhl and
• Sebastian Schlücker

Beilstein J. Org. Chem. 2020, 16, 2911–2919, doi:10.3762/bjoc.16.240

• , Universitätsstrasse 7, 45141 Essen, Germany 10.3762/bjoc.16.240 Abstract Ultraviolet resonance Raman (UVRR) spectroscopy is a powerful vibrational spectroscopic technique for the label-free monitoring of molecular recognition of peptides or proteins with supramolecular ligands such as guanidiniocarbonyl pyrroles

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• precursor for nitrogen heterocycles. As a part of our synthetic design towards the construction of five-membered heterocycles, we have previously reported the synthesis of highly substituted imidazoles [6], indoles [7] and pyrroles [8] starting from different azidochalcones. In continuation, employing α

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• -iminium triflates R‒C≡C‒C(CF3)=N+Me2 TfO− [27]. As a first synthetic application, we have reported the phospha-Michael addition providing 3-(triphenylphosphonio)-1-(trifluoromethyl)-1-(dimethylamino)allenes, which were subsequently transformed into α-(trifluoromethyl)pyrroles. In the present paper, we

Synthesis and highly efficient light-induced rearrangements of diphenylmethylene(2-benzo[b]thienyl)fulgides and fulgimides

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Valerii V. Tkachev,
• Andrey N. Utenyshev,
• Olga Yu. Karlutova,
• Alexander D. Dubonosov,
• Vladimir A. Bren,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2020, 16, 1820–1829, doi:10.3762/bjoc.16.149

• -isomers and of products of the photoinduced rearrangement completed by 1,5-H shift reaction, 3a,4-dihydronaphtho[2,3-c]furans(pyrroles) C, were established based on the data of 1H and 13C NMR spectroscopy and X-ray diffraction studies. Keywords: benzo[b]thiophene; fulgide; fulgimide; photorearrangement

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

• et al., allowing the synthesis of N-heterocycles such as indoles and pyrroles. The targeted heterocyclic products were obtained by cyclization of acetanilides with alkyne derivatives via a direct ortho-metalation pathway (Figure 17) [79]. Acetyl substituents acted as DG in this transformation

• 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

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

• reactions. We further extended the scope of this transformation to five-membered heterocyclic MBH adducts. To our delight, except pyrroles, the proposed methodology was amenable to MBH adducts of furan and thiophene (3n–q, 70–80%). The mechanistic pathway for the triazolation proceeded via a nucleophilic

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• representative example of the less common approach for the construction of the indole skeleton on substituted pyrroles by generating the benzene ring via an annulation process [36][37][38][39]. Due to our interest in transforming simple five-membered heterocycles into natural products [40][41] and complex aza

• provide compounds 12. To account for the strong endo preference of adducts 9, a computational study was performed to analyze the stationary points on the potential surfaces of the Diels–Alder reactions. Results and Discussion Synthesis Pyrroles 8a–j were prepared through a straightforward and efficient

• phosphonates 15a–c to afford derivatives 8a–f in high yields (Table 1, entries 1–6). For the synthesis of pyrroles 8g,h (R1 = Ac), pyrroles 13c and 13e were subjected to condensation reactions at a higher temperature, with acetone as the nucleophile (instead the phosphonate 15) in the presence of KOH as the