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

• to this topic [1][2][3][4][5][6][7][8][9][10][11][12][13]. A still growing number of λ3- and λ5-iodanes are now available as non-toxic and environmentally benign reagents that allow for performing a wide range of transformations under mild conditions. The oxidation of functional groups, halogenations

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• % ee), which displayed the importance of the calix[4]arene skeleton. We also employed calixarene-based chiral primary amine thioureas 47a and 47b in the enantioselective Michael addition of α,α-disubstituted aldehydes 51 to maleimides 52 (Scheme 14) [50]. The reactions proceeded under mild conditions

• [4]arene diamine 60 in our lab [58]. Accordingly, dimethyl squarate 61 was stirred with p-tert-butylcalix[4]arene diamine 60 in CH2Cl2 to give squarate 62. Subsequently, 62 was treated with (1S,2S)-N,N-dimethyl-1,2-diaminocyclohexane (63) under mild conditions, furnishing the final catalyst 64

[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

• -yl triflates [47] and trap them by reaction with sydnones (Scheme 2). These strain-promoted reactions proceed quickly under very mild conditions (at room temperature, in aqueous phosphate buffer with solubilizing DMSO). In a similar manner, very reactive benzynes (didehydrobenzenes) generated either

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

• develop a new C–H heteroarylation of pyridinones. Herein, we report the selective C–H heteroarylation of the C-6 position of bipyridinones by a rhodium-catalyzed reaction with indoleBX (reaction 2, Scheme 1A). In addition, we demonstrate that the mild conditions developed allow the heteroarylation of the

Rapid transformation of sulfinate salts into sulfonates promoted by a hypervalent iodine(III) reagent

• Elsa Deruer,
• Vincent Hamel,
• Samuel Blais and
• Sylvain Canesi

Beilstein J. Org. Chem. 2018, 14, 1203–1207, doi:10.3762/bjoc.14.101

• on the structure of the alcohol. We were pleased to observe successful transformations even in the presence of poorly reactive alcohols such as trifluoroethanol (TFE, Table 2, entry c) or hexafluoroisopropanol (HFIP, Table 2, entry d). Because of the mild conditions involved, this transformation

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• benzylic C–H bonds under mild conditions. The unique radical species, generated by the homolytic cleavage of the labile I(III)–Br bond of the in situ-formed bromo-λ3-iodane, initiated benzylic carboxylation with a high degree of selectivity for the secondary benzylic position. Keywords: carboxylic acids

Preparation, structure, and reactivity of bicyclic benziodazole: a new hypervalent iodine heterocycle

• Akira Yoshimura,
• Michael T. Shea,
• Cody L. Makitalo,
• Melissa E. Jarvi,
• Gregory T. Rohde,
• Akio Saito,
• Mekhman S. Yusubov and
• Viktor V. Zhdankin

Beilstein J. Org. Chem. 2018, 14, 1016–1020, doi:10.3762/bjoc.14.87

• oxidation of 2-iodo-N,N’-diisopropylisophthalamide with m-chloroperoxybenzoic acid under mild conditions. Single crystal X-ray crystallography of this compound revealed a five-membered bis-heterocyclic structure with two covalent bonds between the iodine atom and the nitrogen atoms. This novel benziodazole

• heterocyclic ring. Benziodazoles 5 are usually prepared by the treatment of 2-iodobenzamide derivatives 4 with appropriate oxidants under mild conditions [31][32][33][34][35]. Derivatives of benziodazole can be used as reagents for various oxidative functionalizations of organic substrates [33][36]. For

• . The oxidation of 2-iodo-N,N’-diisopropylisophthalamide (6a) with m-chloroperoxybenzoic acid (mCPBA) under mild conditions afforded the desired bicyclic benziodazole 7a in good yield. Unfortunately, we could not obtain the corresponding pure benziodazole derivatives 7 by the oxidation of precursors 6b

Polysubstituted ferrocenes as tunable redox mediators

• Sven D. Waniek,
• Jan Klett,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86

• syntheses [17][18][19][20][21][22][23][24][25][26][27][28]. Tuning of the electrochemical potential of substituted ferrocenium salts promoted a selective oxidative bicyclization reaction under mild conditions (Scheme 1a) [27]. Ferrocene and decamethylferrocene act as redox catalysts in Meerwein arylation

Electrochemically modified Corey–Fuchs reaction for the synthesis of arylalkynes. The case of 2-(2,2-dibromovinyl)naphthalene

• Fabiana Pandolfi,
• Isabella Chiarotto and
• Marta Feroci

Beilstein J. Org. Chem. 2018, 14, 891–899, doi:10.3762/bjoc.14.76

• and co-workers recently [15]. As mentioned above the second step of the Corey–Fuchs reaction requires the cleavage of a C–Br bond. We thus envisaged if this could be achieved electrochemically via a selective cathodic cleavage of the C–Br bond. In this way, the reaction could be performed under mild

• conditions and in the absence of reducing agents or bases in the reaction mixture. Electrochemical methods can be considered an environmentally friendly technique: they rely on the use of practically massless electrons (which are not converted to byproducts) instead of stoichiometric amounts of redox

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

• et al. described a nanogel composed of poly(N-isopropylacrylamide) brushes grafted on Pd-NPs (Pd@PNIPAM) to carry out coupling reactions in water under mild conditions [120]. They showed highly efficient coupling of several hydrophobic aryl halides with phenylboronic acid, which in all cases resulted

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• up to 94% yields. Shinde et al. also published iodine catalysis carried out at room temperature in DCE [45]. Whereas long reaction times were needed in the latter process, good yields could be achieved under mild conditions. In additional publications listed in Table 1, entries 42–64, phosphorus

• as catalysts. These latest strategies provide efficient syntheses under mild conditions without using harsh chemicals. Furthermore, the application of microwave irradiation or sonication is also preferred to conventional heating methods to accelerate the reactions. Synthesis of aminoalkylphenols The

An alternative to hydrogenation processes. Electrocatalytic hydrogenation of benzophenone

• Cristina Mozo Mulero,
• Alfonso Sáez,
• Jesús Iniesta and
• Vicente Montiel

Beilstein J. Org. Chem. 2018, 14, 537–546, doi:10.3762/bjoc.14.40

• [1][2][3]. Alternatively, electrocatalytic hydrogenation has emerged as a technique driven by its operational mild conditions, i.e., in situ “active hydrogen” generation, room temperature and atmospheric pressure, and higher selectivity [4][5][6][7][8][9][10]. This electrochemical “active hydrogen

Stimuli-responsive oligonucleotides in prodrug-based approaches for gene silencing

• Françoise Debart,
• Christelle Dupouy and
• Jean-Jacques Vasseur

Beilstein J. Org. Chem. 2018, 14, 436–469, doi:10.3762/bjoc.14.32

• to their rapid removal under mild conditions [57]. Heat-sensitive phosphate/thiophosphate-protecting groups have been incorporated into ONs via phosphoramidite chemistry using solid-support methodology. However, some required more drastic conditions (90 °C for a long period of time) to be cleaved

Preparation of trinucleotide phosphoramidites as synthons for the synthesis of gene libraries

• Ruth Suchsland,
• Bettina Appel and
• Sabine Müller

Beilstein J. Org. Chem. 2018, 14, 397–406, doi:10.3762/bjoc.14.28

• group, the dimer was reacted with another N-acyl-5'-O-DMTr-protected nucleoside-3'-O-phosphoramidite to afford the trimer. The 3'-O-TBDMS group was selectively removed under mild conditions with trimethylamine/3HF (Figure 4B) with strict control of pH to leave the β-cyanoethyl groups at the

Diels–Alder cycloadditions of N-arylpyrroles via aryne intermediates using diaryliodonium salts

• Huangguan Chen,
• Jianwei Han and
• Limin Wang

Beilstein J. Org. Chem. 2018, 14, 354–363, doi:10.3762/bjoc.14.23

• be easily obtained in 63% yield with palladium on carbon catalyst under hydrogen atmosphere at room temperature (Scheme 3). Conclusion In summary, we have demonstrated a Diels–Alder cycloaddition of N-arylpyrroles by using diaryliodonium salts under mild conditions. The synthetic method was extended

Continuous-flow retro-Diels–Alder reaction: an efficient method for the preparation of pyrimidinone derivatives

• Imane Nekkaa,
• Márta Palkó,
• István M. Mándity and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2018, 14, 318–324, doi:10.3762/bjoc.14.20

• ] syntheses of heterocyclic compounds. The rDA products can be gained, due to a thermal [4 + 2]-cycloreversion, by distillation under reduced pressure [29], boiling in solvent [30][31], and applying microwave irradiation [32][33][34][35] or flash vacuum pyrolysis [35][36]. rDA reactions under mild conditions

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• yielding [57][62]. Thus, a new mild synthetic route for the synthesis of 5-(pyridyl)thiophenes is required. We therefore investigated the synthesis of thienylpyridines using a metal-free approach. Results and Discussion At first, our efforts focused on the intramolecular cyclization reactions with mild

• conditions – in the absence of an added base at room temperature. To obtain aminothioacetal 7a, we initially performed the S-alkylation of the intermediate thiolate salt with 2-(bromomethyl)pyridine at room temperature overnight. We interestingly found that the desired 5-(pyridin-2-yl)thiophenes 8a has

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

• convenient regioselective synthetic methods with mild conditions and good yields of the reactions [40][41]. Aggarwal et al. [42] reported the regiospecific synthesis of 4-trifluoromethyl-1H-pyrazolo[3,4-b]pyridines 18 by the reaction of 5-aminopyrazole 16 with trifluoromethyl-β-diketones 17 in refluxing

Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)

• Michał Nowacki and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14

• developed a simple synthesis of indolo[3,2-b]quinoline derivatives by the reaction of nitroarenes with indol-2-ylmethyl carbanions generated from easily accessible starting materials. The reactions proceed under mild conditions and the elaborated method does not employ transition metals at any stage thus

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• was conducted under mild conditions using Umemoto’s reagent as the trifluoromethylation agent in the presence of isoamyl nitrite (iAmONO). The reaction proceeded smoothly with various arylamines under these conditions to give the corresponding products in modest to good yields. The reaction exhibits

• aryldiazonium ion, which is generated in situ from the corresponding arylamine. At the same time, a copper-catalyzed Sandmeyer trifluoromethylation of arenediazonium tetrafluoroborates was also reported by the group of Gooßen (Scheme 25) [44]. This reaction was conducted under mild conditions using TMSCF3 as

• trifluoromethylation reaction of terminal alkenes through C(sp3)–H activation (Scheme 29). Many substrates underwent the trifluoromethylation smoothly using Umemoto’s reagent 1e as a trifluoromethyl source and CuTC as catalyst under mild conditions. This reaction was tolerant to moisture and was compatible to

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• . Photoredox-active metal complexes or organic dyes are used to initiate photo-induced single-electron transfer (SET) processes upon excitation with visible-light. Such photooxidations or photoreductions yield reactive organic radicals, which can undergo unique bond forming reactions, under very mild

• conditions. The key concepts of photocatalysis and photoredox-catalyzed reactions for carbon–carbon and carbon–heteroatom (C–X) bond formation have been reviewed in detail. However, several new photocatalytic methods for the formation of carbon–sulfur (C–S) bonds were recently reported and we aim to

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

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

Palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides

• Tao Fan,
• Wei-Dong Meng and
• Xingang Zhang

Beilstein J. Org. Chem. 2017, 13, 2610–2616, doi:10.3762/bjoc.13.258

• under mild conditions and showed good functional group compatibility, even towards formyl and hydroxy groups, thus providing a facile route for applications in discovering biologically interesting molecules. Preliminary mechanistic studies reveal that a secondary trifluoromethylated alkyl radical is