A metal-free approach for the synthesis of amides/esters with pyridinium salts of phenacyl bromides via oxidative C–C bond cleavage

• Kesari Lakshmi Manasa,
• Yellaiah Tangella,
• Namballa Hari Krishna and
• Mallika Alvala

Beilstein J. Org. Chem. 2019, 15, 1864–1871, doi:10.3762/bjoc.15.182

• new C–N bonds in the presence of transition metal catalysts [25][26][27][28][29][30][31][32][33][34]. Tang and Jiao reported copper catalyzed C–C single bond cleavage and C–N bond formation [35]. However, the transition metal catalysts and additives employed in these transformations are toxic and

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

• . The Pd-catalyzed Sonogashira reaction has successfully constructed arylated internal alkynes that are important intermediates in organic synthesis, molecular electronics and polymers [56]. C–N bond forming reactions between aryl halides and amines/amides/sulfonamides have been extensively studied in

• generation of iminyl radical intermediate 31 by homolytic cleavage of the C–N bond which was followed by reductive elimination and oxidation to yield final compound 21. Inspired by the work of Wang et al. [15] who have exploited a Cu(II)-catalyst for the construction of pyrido[1,2-a]benzimidazoles Li and Xie

• aromatic or aliphatic, only in case of triazoles substituted with an acetate group the final product was obtained in 66% yield. An open-flask, one-pot, Cu(II)-catalyzed ligand-free approach towards C–N bond formation was reported by Rasheed et al. [116]. The reaction was catalyzed by Cu(OAc)2 with cesium

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• CN at 2250 cm−1. In addition, there are characteristic bands at 1664–1668 cm−1, which may include both C=C bond and the exocyclic C=N bond. Fluctuations of endocyclic C=N fragments are observed at 1584 cm−1. Thus, at least one nitrile and one NH2 group are present in the obtained compounds. The 1H

An efficient and concise access to 2-amino-4H-benzothiopyran-4-one derivatives

• Peng Li,
• Yongqi Wu,
• Tingting Zhang,
• Chen Ma,
• Ziyun Lin,
• Gang Li and
• Haihong Huang

Beilstein J. Org. Chem. 2019, 15, 703–709, doi:10.3762/bjoc.15.65

• process. The direct C–N bond formation reaction at the 2-position smoothly took place using ethylsulfinyl as the optimal leaving group and various nucleophiles such as aliphatic and aromatic amines. A variety of 2-aminobenzothiopyranones were obtained in moderate to excellent yields without the assistance

Tandem copper and photoredox catalysis in photocatalytic alkene difunctionalization reactions

• Nicholas L. Reed,
• Madeline I. Herman,
• Vladimir P. Miltchev and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2019, 15, 351–356, doi:10.3762/bjoc.15.30

• of the C–N bond-forming step, as one might expect from its proposed role in radical oxidation (Figure 1C). Conclusion These studies have demonstrated that the copper-mediated alkene difunctionalization reactions recently reported by our laboratory can be rendered catalytic in Cu(II) by adding a

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• -hydroxyaryl)pyridine derivatives bearing a carboxylate or a nitrile group suitably placed at C3 position of the aza-ring has been achieved in acceptable chemical yields with a broad functional group tolerance. This sequential C–C/C–N bond making process proceeds through a regioselective allylic alkylation/aza

• DABCO, followed by aromatization using DBU as a base in an open-flask has been developed. This smart oxidant metal-free C–C/C–N bond forming process leads to an array of functionalized nicotinates/nicotinonitriles possessing an interesting phenolic moiety at C6 position in good to high yields. Moreover

The mechanochemical synthesis of quinazolin-4(3H)-ones by controlling the reactivity of IBX

• Md Toufique Alam,
• Saikat Maiti and
• Prasenjit Mal

Beilstein J. Org. Chem. 2018, 14, 2396–2403, doi:10.3762/bjoc.14.216

• ]. Aryliodonium imides or iminoiodanes can be prepared by the treatment of electron-deficient amines with iodine(III). However, these compounds explode at higher temperatures [4] and hence are stored under inert atmosphere and low temperature [5]. Polyvalent iodine derivatives are versatile reagents for C–N bond

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

Beilstein J. Org. Chem. 2018, 14, 2295–2307, doi:10.3762/bjoc.14.204

• the oxidation of the other C–N bond of the methyl group in N-methylaminobutyrate to form methylamine and succinate semialdehyde, an MAO reaction [39]. While the kcat/Km value of Mao with 4-aminobutyrate is only 8% that of Mabo, A. nicotinovorans grown on [14C]-nicotine produce [14C]-methylamine

• it contains covalently-bound FAD and produces hydrogen peroxide as a product in addition to 4-aminobutryate [5][38]. Mabo also catalyzes the oxidative demethylation of sarcosine. Based on these results, the mechanism of the enzyme is similar to that of sarcosine oxidase, direct oxidation of the C–N

• bond of the substrate methyl group by hydride transfer [40]. The resulting 4-aminobutryrate is likely a substrate for a chromosomally-encoded aminotransferase, producing α-ketoglutarate and succinate semialdehyde. Mao (γ-N-methylaminobutyrate oxidase) contains noncovalently-bound flavin and catalyzes

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• hydroarylation of glyoxylate with pyrimidine containing indoles and pyrroles 7 to provide products 63 with high productivity (Scheme 40) [79]. Similar to the imine, isocyanate is also an efficient electrophile for hydroarylation of C=N bond. It provides a high atom- and step-economical method for the preparation

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• molecules. An interesting report of C–N bond formation is seen in König and co-workers’ method for the formation of sulfonamidated pyrroles, using acridinium salts as photocatalysts, in the presence of oxygen and sodium hydroxide (Scheme 10) [53]. Unfortunately, this protocol was investigated for its use in

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• have been widely used in organic synthesis [38]. Although originally used as oxidative agents, their use has spread to coupling reactions, including those for the formation of C–C bonds [39][40][41][42][43]. In the case of C–N bond formation, introduction of an azido group using PhI=O and TMSN3 was

• -mediated glycosylation led us to apply the reaction to the synthesis of carbocyclic nucleosides. In addition, we were also encouraged by the study of Ochiai, who developed the Friedel–Crafts reaction via umpolung of allylsilanes using hypervalent-iodine reagents [61] and the pioneering work on C–N bond

• developed. Since the Friedel–Crafts type reaction involved carbocation intermediate, the reaction always gave a mixture of products. Unfortunately, the reaction was not efficient. However, it is worthy that the oxidative coupling reaction contains a novel type of C–N bond formation and would help to

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• has led to a much lower yield when compared to that obtained from the corresponding diaryl-λ3-iodane. In 2011, the group of Detert has reported the first example of a palladium-catalyzed double C–N bond formation starting from the cyclic (phenyl)(pyrido)-λ3-iodane 61 (Scheme 25) [65]. The reaction

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• formation followed by Cu–N dissociation and C–N bond formation. Experiments performed in t-BuOD/D2O [119] also showed almost exclusive (>98:2) deuteration of position 3 in the final pyrazole ring. This finding supports the idea of Cu(I)-acetylide addition to give 3-metalated pyrazole (Cu-pyrazolide) that is

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• glycosidic bond in 2'-deoxy ribonucleosides has a higher susceptibility to cleavage than in the corresponding ribonucleosides [38][39][40][41][43]. The rate of glycosidic (C–N) bond cleavage is enhanced by decreasing pH and enzymes, which modify the localized acid–base environment [31][35][36]. The C–N bond

• . The O–C–N bond between nucleobase and sugar defines the glycosidic bond. Replacement of nucleobase nitrogen by carbon results in C-nucleosides. A carbon (CH2) replacing the sugar oxygen results in carbocyclic nucleosides. When both the heteroatoms in the glycosidic bond are replaced by carbon, the

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• [105]. Conversion of 4-NP in five successive cycles of reduction, catalyzed by Au@citrate, Au@PEG and Au@PEG45-b-PS65. Reprinted with permission from [121]. Copyright 2015 American Chemical Society. C–N bond formation under micellar catalyst conditions, no organic solvent involved. Adapted from

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• -catalyzed aerobic conditions [29]. Under the same peroxide photolysis conditions (t-BuOOt-Bu with UV (254 nm) irradiation), the ortho-alkenylated imine 3aa underwent a C–N bond-forming cyclization to afford the spirocyclic imine 4 in 81% yield (Scheme 4). The reaction likely involves the initial formation

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• (147) with 3-oxo-3-arylpropanenitrile 15 under solvent-free grinding conditions. The reaction was proposed to proceed via formation of hydrazine by C–N bond cleavage which under reaction conditions provided 7-aminopyrazolo[1,5-a]pyrimidines 148 on coupling with 3-oxo-3-arylpropanenitrile 15 (Scheme 42

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• obtained after reductive elimination of species 18. The other envisaged pathway was the oxidation of intermediate 17 through a SET to form the cationic species 19, which would then afford the final product after a C–N bond formation. Liu and co-workers also proposed a racemic version of this reaction

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• subsequent 1,2-proton transfer followed by the elimination of triphenylphosphine and ring closure via formation of the new C–N bond gave the final γ-lactam derivatives 80 (Scheme 50) [66]. In 2013 Mohebat et al. used 6-amino-N,N'-dimethyluracil as an NH-acid and precursor of the carbon nucleophile in the

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• C–N bond is 1.368 Å compared to 1.333 Å for the C=C bond [5][10][11][12]. Also, the amide structure is found in Nature as the s-trans or s-cis isomer, which can be in equilibrium (Figure 2b) [13]. However, most of the time it is found as the s-trans isomer to minimize steric interaction and to

One-pot three-component route for the synthesis of S-trifluoromethyl dithiocarbamates using Togni’s reagent

• Azim Ziyaei Halimehjani,
• Martin Dračínský and
• Petr Beier

Beilstein J. Org. Chem. 2017, 13, 2502–2508, doi:10.3762/bjoc.13.247

• afforded the corresponding isothiocyanate in high yield. A variable temperature NMR study revealed a rotational barrier of 14.6, 18.8, and 15.9 kcal/mol for the C–N bond in the dithiocarbamate moiety of piperidine, pyrrolidine, and diethylamine adducts, respectively. In addition, the calculated barriers of

• and trifluoromethyl groups in a single structure generates a new family of compounds with potential application as agrochemicals or in drug design. A variable temperature NMR study allowed the determination of rotational barriers of 14.6, 18.8, and 15.9 kcal/mol for the C–N bond in the dithiocarbamate

• and an increased double bond character of the C–N bond. Variable temperature 1H NMR spectra of compound 4c (CH2 region on the left and CH3 region on the right); the sample was dissolved in CDCl3. The Eyring plot obtained for the rotation around the N–C bond in compound 4c. The optimized structure of

A mechanochemical approach to access the proline–proline diketopiperazine framework

• Nicolas Pétry,
• Hafid Benakki,
• Eric Clot,
• Pascal Retailleau,
• Farhate Guenoun,
• Fatima Asserar,
• Chakib Sekkat,
• Thomas-Xavier Métro,
• Jean Martinez and
• Frédéric Lamaty

Beilstein J. Org. Chem. 2017, 13, 2169–2178, doi:10.3762/bjoc.13.217

• attack on Cb, were considered (Scheme 5). The first step was to study if there was any preferential interaction between the free nitrogen atom and either Ca or Cb before the C–N bond formation. Both optimized structures are shown in Figure 1, and compound 16a is computed to be less stable than 16b by ΔG

• = 2.7 kcal mol−1. The C···N bond distance is slightly shorter in 16b (2.673 Å) than in 16a (2.682 Å). Many attempts to locate a transition state structure for the C–N bond formation starting from either 16a or 16b failed. Even though the geometry optimizations were performed with implicit inclusion of

• the solvent influence (SMD model with methanol), the zwitterionic character developing in the C–N bond formation could not be stabilized. However, the protic methanol solvent could act both as a base to abstract the proton from the nitrogen atom, and as an acid to facilitate the C–OMe bond cleavage

Transition-metal-free synthesis of 3-sulfenylated chromones via KIO₃-catalyzed radical C(sp²)–H sulfenylation

• Yanhui Guo,
• Shanshan Zhong,
• Li Wei and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2017, 13, 2017–2022, doi:10.3762/bjoc.13.199

• efforts in exploring enaminone C(sp2)–H bond sulfenylation [40][41] reactions have led us to establish the synthesis of 3-sulfenylated chromones via KIO3-catalyzed tandem reactions of o-hydroxylphenylenaminone and thiophenols via tandem C–H sulfenylation and intramolecular C–N bond oxygenation (B, Scheme

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• acetic acid (LAG). Contrastingly, when acrylic esters were treated with 8 mol % of PdCl2 and in absence of acetic acid, β,β-diindolylpropionates were obtained as the major product (Scheme 14) [70]. C–N bond synthesis Amongst C–N bonds the amide bonds are most abundant and important too [71]. According to

• the American Chemical Society (ACS) and the Green Chemistry Institute (GCI), the “amide bond formation avoiding poor atom economy reagent” is one of the top challenges for organic chemists [72]. Easy, economical, selective and convenient approaches on C–N bond syntheses are of great importance [73][74

• nearly 90% yields for α-amino esters in 90–120 min (Scheme 18). The Ritter reaction is another significant carbon–nitrogen (C–N) bond forming reaction in the synthesis of amides [86]. Generally, a nitrile and a tertiary alcohol in presence of a strong acid react to create amides. Major drawbacks