Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• position of quinoline N-oxides and pyridine N-oxides, utilizing hypervalent iodine salts as the arylation reagents. The reaction was facilitated by visible light in conjunction with a photocatalyst. The absence of either the photocatalyst or light resulted in only trace amounts of the product, underscoring

• their essential roles in product formation. Optimized conditions comprised the reaction of the quinoline N-oxides 25 (1 equiv) with diaryliodonium tetrafluoroborates 26 (2 equiv) as the arylating agent, 1,4-benzoquinone (BQ) as an additive (2 equiv), the photocatalyst eosin Y (10 mol %), and Cs2CO3 (1

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

• amidating reagent leading to the isolation of copper–arylcarbamato species and the desired product. The developed amidation protocol works highly efficiently and selectively over a broad range of substrates including polyfluorobenzenes, azoles, and quinoline N-oxides (Scheme 74). 2.10 C(sp2)–H thiolation

Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines

• Geetanjali S. Sontakke,
• Rahul K. Shukla and
• Chandra M. R. Volla

Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42

• simplicity of the developed protocol. The current transformation was also found to be compatible for the late-stage modification of natural products. Keywords: amination; heteroarylation; quinoline N-oxides; regioselective; triazoles; Introduction Quinoline is a key heterocyclic moiety found in many

• ][37][38][39][40][41][42][43][44][45]. For example, Yin and co-workers developed a protocol for the deoxygenative C2-amination of pyridine/quinoline N-oxides using t-BuNH2 and Ts2O/TFA in 2007 (Scheme 1a) [48]. Later, Londregan and co-workers were successful in achieving C2-amination employing

• mentioning that when pyridine N-oxide was employed instead of 1a, only traces of the corresponding product were observed even after prolonged reaction time. Subsequently, the substrate scope was evaluated by analyzing electronic and steric effects of substituents present on the quinoline N-oxides 1 (Scheme 3

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

• heteroarenes was realized using the benziodoxolone hypervalent iodine reagents indoleBXs. Functionalization of the C–H bond in bipyridinones and quinoline N-oxides catalyzed by a rhodium complex allowed to incorporate indole rings into aza-heteroaromatic compounds. These new transformations displayed complete

• 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

• C-8 position of quinoline N-oxides, whereas formation of the quinolinone had been observed in our previous work (Scheme 1B). The obtained products combine up to three classes of privileged heterocycles in medicinal chemistry in a single compound, and are therefore expected to be highly useful

Recent advances in copper-catalyzed C–H bond amidation

• Jie-Ping Wan and
• Yanfeng Jing

Beilstein J. Org. Chem. 2015, 11, 2209–2222, doi:10.3762/bjoc.11.240

• products 49 or 50 by incorporating phthalimide/saccharin 46. Under the standard conditions, however, the reaction of benzamide with 2-phenylpyridine provided product 51 with low yield (Scheme 14). As a special aromatic system, quinoline N-oxides were well investigated in their reactivity for metal

• -catalyzed C–H activation. Based on the known results of quinoline N-oxide C–H alkenylation [61], arylation [62] and alkylation [63] etc, Li and co-workers [64] investigated and established the C–H amidation of quinoline N-oxides 52 via copper catalysis. According their results, quinoline N-oxides 51

• and benzene C–H bonds. Copper-catalyzed C–H amination/amidation of quinoline N-oxides. Copper-catalyzed aldehyde formyl C–H amidation. Copper-catalyzed formamide C–H amidation. Copper-catalyzed sulfonamidation of vinyl C–H bonds. CuCl2-catalyzed amidation/sulfonamidation of alkynyl C–H bonds. Cu(OH)2

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

• Kegong Ji,
• Jonathan Nelson and
• Liming Zhang

Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227

• carboxylate; Introduction We reported in 2010 [1] that α-oxo gold carbenes could be conveniently generated as reactive intermediates in gold-catalyzed intermolecular oxidation of alkynes. By using pyridine N-oxides [1] and later 8-substituted quinoline N-oxides [2] as the external oxidants, this approach

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Gold-catalyzed regioselective oxidation of terminal allenes: formation of α-methanesulfonyloxy methyl ketones

• Yingdong Luo,
• Guozhu Zhang,
• Erik S. Hwang,
• Thomas A. Wilcoxon and
• Liming Zhang

Beilstein J. Org. Chem. 2011, 7, 596–600, doi:10.3762/bjoc.7.69

• ][13][14][15][16][17] or via allenes generated in situ [18][19][20][21]. We have recently shown that highly reactive gold carbenes can be generated from alkynes via gold-promoted intermolecular oxidation by pyridine/quinoline N-oxides [22][23][24][25], making benign alkynes effective surrogates of