New one-pot synthesis of 4-arylpyrazolo[3,4-b]pyridin-6-ones based on 5-aminopyrazoles and azlactones

• Vladislav Yu. Shuvalov,
• Ekaterina Yu. Vlasova,
• Tatyana Yu. Zheleznova and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2023, 19, 1155–1160, doi:10.3762/bjoc.19.83

• ). Their diluted alcohol solutions luminesce with a quantum yield of 0.09–0.23. Pyrazolo[3,4-b]pyridinones 4a–i, 9a, and 10a are characterized by an abnormally high Stokes shift (107–152 nm, 1.07–1.49 eV, Table 2). Such luminophores, which are colorless in daylight but become colored when irradiated with

Rhodium-catalyzed C–H functionalization of heteroarenes using indoleBX hypervalent iodine reagents

• Erwann Grenet,
• Ashis Das,
• Paola Caramenti and
• Jérôme Waser

Beilstein J. Org. Chem. 2018, 14, 1208–1214, doi:10.3762/bjoc.14.102

• regioselectivity for the C-6 position of bipyridinones and the C-8 position of quinoline N-oxides and tolerated a broad range of functionalities, such as halogens, ethers, or trifluoromethyl groups. Keywords: C–H activation; hypervalent iodine; indoleBX; indoles; pyridinones; rhodium catalysis; Introduction

• also omnipresent in bioactive compounds [2]. It can be directly bound to other heterocycles, such as a dihydropyrazidinone in hamacanthine A (4) (Figure 1) [3]. Due to their occurrence in biologically active compounds, it is therefore attractive to develop new methods to functionalize pyridinones. The

• procedures have been described for the modification of pyridinones to introduce other substituents, especially based on highly efficient C–H functionalization methods [10]. Very recently, several research groups have selectively functionalized the C-6 C–H bond by using a 2-pyridyl directing group on the

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• give intermediate radical 65, which was oxidised by Mn(OAc)3 to form the carbocation 66 and, after deprotonation, the trifluoromethyl compounds (Scheme 39) [62]. The same group also reported a straightforward method for the trifluoromethylation of pyrimidinones and pyridinones under the same reaction

• -position of pyridinones facilitated the trifluoromethyl radical attack [63]. Catalytic amounts of phosphovanadomolybdic acid, a heteropolyacid catalyst (HPA), was used by Mizuno, Yamaguchi and co-workers for the oxidative C−H trifluoromethylation of arenes and heteroarenes in the presence of CF3SO2Na and

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• showed that benzimidazoles, Biginelli adducts, dihydropyridines, furans, pyrans, pyridinones, and thiophenes had a high representation of intrinsic greenness; whereas, a high proportion of MCRs producing chromene-4-ones, coumarins, indoles, and pyrazoles had low probabilities of achieving intrinsic

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• 1.1.1 and 1.2.1), during the cleavage of the fully elongated precursor from the PKS (as for example for tetronates, tetramates and pyridinones, see chapters 1.7.1, 2.2.1 and 2.1.3) or during post-PKS tailoring (as for example during oxidative cyclisation in aureothin biosynthesis, see chapter 1.2.2

• established in four principal ways (Scheme 29). The biosynthesis of pyridinones (203, 207, 211 or 213) is mechanistically particularly diverse. It occurs via condensation reactions between carbonyl groups and nitrogen-containing functionalities, Michael addition–lactamisation cascades (similar to the

• mechanism for 4-substituted pyran-2-ones shown in Scheme 2e), Dieckmann condensations as well as oxidative ring expansion of tetramates (212, a–d in Scheme 29). Tetramates 209 are formed by Dieckmann condensation (c in Scheme 29). 2.1 Pyridinones 2.1.1 Condensation between carbonyl groups and nitrogen

Synthesis of functionalized spiro[indoline-3,4’-pyridines] and spiro[indoline-3,4’-pyridinones] via one-pot four-component reactions

• Li-Juan Zhang,
• Qun Wu,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 846–851, doi:10.3762/bjoc.9.97

• malononitrile afforded the functionalized spiro[indoline-3,4’-pyridine] derivatives in good yields. Similar reactions with ethyl cyanoacetate successfully afforded the functionalized spiro[indoline-3,4’-pyridines] and spiro[indoline-3,4’-pyridinones] as the main products according to the structures of the

• reactions of arylamines, methyl propiolate, aromatic aldehydes and malononitrile (ethyl cyanoacetate) and successfully developed a facile synthetic procedure for functionalized spiro[indoline-3,4’-pyridines] and spiro[indoline-3,4’-pyridinones]. Results and Discussion The efficient formation of

• reaction under similar conditions, the reaction usually resulted in a complicated mixture of spiro[indoline-3,4’-pyridines] 2 and spiro[indoline-3,4’-pyridinones] 3 depending on whether the cyano group or the ester group was taking part in the cyclization process (Scheme 1). In order to simplify the

Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes

• Elena Borsini,
• Gianluigi Broggini,
• Andrea Fasana,
• Chiara Baldassarri,
• Angelo M. Manzo and
• Alcide D. Perboni

Beilstein J. Org. Chem. 2011, 7, 1468–1474, doi:10.3762/bjoc.7.170

• either from direct cyclization or from a formal rearrangement of the carboxamide group. Terminal alkynes are essential to achieve bicyclic pyrrolo-fused pyridinones by a 6-exo-dig process, while the presence of a phenyl group at the C–C triple bond promotes the 7-endo-dig cyclization giving pyrrolo

• lacking the benzoyl group (Table 3, entries 11–14). The highest selectivity was obtained with toluene as solvent, where only pyrrolo[2,3-c]pyridinones, i.e., 5d and 9 (Table 3, entry 11), were formed. Although the picture of the products generated from the treatment of the propargyl pyrrole-2-carboxamides

• , 6.39; N, 11.10; found: C, 76.23; H, 6.30; N, 11.04. Significant relationships among hydrogen and carbon atoms arising from 2D-NMR studies to determine the pyrrolo-pyridinones. Pd-catalyzed cyclization of N-allyl-pyrrole-2-carboxamides. Proposed mechanism for the formation of the six-membered products