Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• ligands attached to the iodane are part of the target molecule or in which the iodane acts as an oxidant and a group-transfer reagent in a consecutive reaction sequence. The chapters are divided by the structure of the transferred functional groups, starting from simple diarylations and oxidative

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• of an external oxidant. The use of catalytic chiral hypervalent iodine reagents in asymmetric catalysis is one of the most challenging ongoing topics and this review will focus on the development of various chiral hypervalent iodine reagents and their application in typical organic transformations

• new kind of binaphthyl-based chiral I(III) prereagent 19 with the 8 and 8′ positions of the naphthalene substituents being occupied by iodide. Here they have observed that this chiral hypervalent iodine reagent 19 in the presence of co-oxidant m-CBPA is very useful for the dearomatizing

• a high level of enantioselectivity. Naphthol derivatives 31 were converted to spirocyclic lactones 32 in the presence of m-CPBA as co-oxidant for the in situ generation of the I(III) catalyst. Secondary n–π* and/or hydrogen-bonding interactions of the catalyst ensured remarkable enantioselectivities

Iodine(III)-mediated halogenations of acyclic monoterpenoids

• Laure Peilleron,
• Tatyana D. Grayfer,
• Joëlle Dubois,
• Robert H. Dodd and
• Kevin Cariou

Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96

• bromocarbocyclization of aryl-geranyl derivatives using a combination of iodine(III) oxidant and a bromide source. In this fashion, the reaction of homogeranylbenzene with bis(tert-butylcarbonyloxy)iodobenzene and triethylsilyl bromide, followed by acidic treatment led to a tricyclic brominated adduct (Scheme 1

• NIS [21] and does not require the use of a strong oxidant such as IBX [22]. Compared to the standard procedure for the preparation of acetoxyhypohalites that requires the use of expensive and potentially toxic silver salts [23], our method offers a more practical alternative. It also differs from the

Hypervalent iodine-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• )-mediated Ritter-type oxyamidation and amido-amidation of terminal alkenes in the presence of a Lewis acid. Optimization studies of this Ritter-type oxyamidation commenced with oxidant screening in the presence of a Lewis acid (Table 1). Without oxidant, the Ritter-type oxyamidation still proceeded to give

Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

• Felix Scheidt,
• Christian Thiehoff,
• Gülay Yilmaz,
• Stephanie Meyer,
• Constantin G. Daniliuc,
• Gerald Kehr and
• Ryan Gilmour

Beilstein J. Org. Chem. 2018, 14, 1021–1027, doi:10.3762/bjoc.14.88

• enable this transformation [28][29]. Employing Selectfluor® as the terminal oxidant, it was possible to generate p-TolIF2 in situ from p-iodotoluene and an inexpensive HF source [30][31][32][33][34][35]. This strategy proved to be mild and general, smoothly converting terminal olefins to the

• DCE (0.2 mol·L−1) with 20 mol % catalyst loading, and using Selectfluor® as the oxidant. An initial reaction screen, based on the conditions reported for our vicinal difluorination study [9], began with an exploration of the effect of amine/HF ratio. This was deemed prudent due to the perceived

• . Conclusion An operationally simple route to 5-fluoromethyl-2-oxazolines from readily accessible N-allylcarboxamides is disclosed based on an I(I)/I(III) catalysis manifold. This metal-free fluorocyclisation employs p-iodotoluene (10 mol %) as an inexpensive organocatalyst and Selectfluor® as oxidant. The

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

• δ being the averaged chemical shift of the mixture. The detection of the resonances of 1/1+–4/4+ should allow for determining the ratio of 1:1+–4:4+ by in situ NMR experiments. Thus, titration of 1–4 with Magic Green, tris(2,4-dibromophenyl)ammoniumyl hexachloroantimonate [10], as a strong oxidant

• -C6H3Br2)3]+ as oxidant. a[N(2,4-C6H3Br2)3]. bCDHCl2. cResidual solvents and grease. Selected transformations with ferrocene/ferrocenium as SET reagents (a) [27], catalyzed (b,c) [29][30][31] and mediated transformations (d–f) [34][35][36] by the ferrocene/ferrocenium redox couple. Methyl esters of

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Keshaba N. Parida,
• Gulab K. Pathe,
• Shimon Maksymenko and
• Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

• -coupling by using cerium(IV) as a one-electron oxidant [11]. Importantly for the discussion of the present work, Wirth’s strategy relied on a hypervalent iodine [13][14][15] mediated oxidative cross-coupling. Although these processes add a further step to the process, carrying out the cross-coupling in an

• challenging cross-coupling of two dissimilar ketone enolates. In this context Hirao achieved the intermolecular cross-coupling by taking advantage of the different oxidation potentials of boron enolates and trimethylsilyl enol ethers to achieve selectivity with vanadium (V, 0.625 equiv) as the oxidant (Scheme

2-Iodo-N-isopropyl-5-methoxybenzamide as a highly reactive and environmentally benign catalyst for alcohol oxidation

• Takayuki Yakura,
• Tomoya Fujiwara,
• Akihiro Yamada and
• Hisanori Nambu

Beilstein J. Org. Chem. 2018, 14, 971–978, doi:10.3762/bjoc.14.82

• to benzophenone in the presence of Oxone® (2KHSO5·KHSO4·K2SO4) as a co-oxidant at room temperature. A study on the substituent effect of the benzene ring of N-isopropyl-2-iodobenzamide on the oxidation revealed that its reactivity increased in the following order of substitution: 5-NO2 < 5-CO2Me, 3

• isophthalic acids (SIBX) [39] has been reported. Nevertheless, from a green chemistry viewpoint, pentavalent iodine oxidants are not ideal because oxidation reactions require a stoichiometric amount of the oxidant that produces an equimolar amount of organoiodine waste. The catalytic use of pentavalent iodine

• developed as catalysts for the oxidation of alcohols in the presence of Oxone® (2KHSO5·KHSO4·K2SO4) as a co-oxidant. In these reported systems, high temperatures (40–70 °C) are often required to generate potentially explosive pentavalent iodine compounds in situ except for the reactions involving

An efficient and facile access to highly functionalized pyrrole derivatives

• Meng Gao,
• Wenting Zhao,
• Hongyi Zhao,
• Ziyun Lin,
• Dongfeng Zhang and
• Haihong Huang

Beilstein J. Org. Chem. 2018, 14, 884–890, doi:10.3762/bjoc.14.75

• cycloaddition of azomethine ylides with N-alkyl maleimide, followed by a facile oxidation using DDQ as oxidant. Further manipulation with alkylamine/sodium alkoxide alcohol solution conveniently led to novel polysubstituted pyrroles in good to excellent yields (Scheme 1). Results and Discussion As shown in

• . Unfortunately, the desired pyrrole product 12a was obtained only in 41% yield with DDQ (4 equiv) as oxidant at room temperature for 48 h (Table 3, entry 1). As expected, toluene as solvent improved the reaction outcome to afford 12a in a good yield up to 71% (Table 3, entry 2). Subsequently, reducing the amount

One-pot synthesis of diaryliodonium salts from arenes and aryl iodides with Oxone–sulfuric acid

• Natalia Soldatova,
• Pavel Postnikov,
• Olga Kukurina,
• Viktor V. Zhdankin,
• Akira Yoshimura,
• Thomas Wirth and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 849–855, doi:10.3762/bjoc.14.70

• , Park Place, Main Building, Cardiff CF10 3AT, UK 10.3762/bjoc.14.70 Abstract A facile synthesis of diaryliodonium salts utilizing Oxone as versatile and cheap oxidant has been developed. This method shows wide applicability and can be used for the preparation of iodonium salts containing electron

• highly desirable goal. Previously, we have published the utilization of Oxone® (2KHSO5·KHSO4·K2SO4) as a readily available and effective oxidant for the preparation of various hypervalent iodine compounds [36][37][38][39][40][41][42]. Oxone is used as an efficient oxidant for the direct conversion of

• substituted 2-iodobenzoic acids to arylbenziodoxoles [37][38], 2-iodobiphenyl to dibenziodolium compounds [39], iodoarenes to iodylbenzenes and [bis(trifluoroacetoxy)iodo]arenes [40][41], and for the preparation of diaryliodonium trifluoroacetates and triflates [42]. Yakura also used Oxone® as an oxidant for

Biocatalytic synthesis of the Green Note trans-2-hexenal in a continuous-flow microreactor

• Morten M. C. H. van Schie,
• Tiago Pedroso de Almeida,
• Gabriele Laudadio,
• Florian Tieves,
• Elena Fernández-Fueyo,
• Timothy Noël,
• Isabel W. C. E. Arends and
• Frank Hollmann

Beilstein J. Org. Chem. 2018, 14, 697–703, doi:10.3762/bjoc.14.58

• this reaction, however, necessitates significant molar surpluses of the stoichiometric oxidant (such as acetone). This not only negatively influences the environmental impact of the reaction [6] but also complicates downstream processing. Furthermore, the nicotinamide cofactor (even if used in

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

• )indoles 52. Then, through C-2 cyclization of the indole ring using I2 as catalyst and tert-butyl hydroperoxide as oxidant, chromeno[2,3-b]indoles were isolated in 71–98% yields. In a different reaction pathway, starting from 3-(aminoalkyl)indoles 53 and phenols or naphthols, 3-(α,α-diarylmethyl)indoles 52

Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• amino acids has always been paid much attention in industrial and academic setting and many advances have been made [12][13][14][15][16][17]. Li et al. first reported the functionalization of glycine derivatives with malonates using a stoichiometric quantity of Cu(OAc)2 as catalyst and oxidant [12

• terminal oxidants [14]. The protocol was also extended to reactions with 2-alkylquinoline [15] and phenols [16] using O2 and di-tert-butyl peroxide (DTBP) as oxidant, respectively (Scheme 1). A CuCl-catalyzed oxidative cross coupling of glycine derivatives with indoles has been developed by Hou et al

• ., wherein simple copper salts were used as catalysts and oxygen as the co-oxidant (Scheme 1) [17]. Alternatively, photocatalytic versions of CDC reactions of glycine derivatives with C-nucleophiles were also developed [18][19]. For example, combining the visible light catalyst Ru(bpy)3Cl2, and the

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

• POCl3 to afford the respective 1-arylpyrazolo[3,4-d]pyrimidin-4-ones 222 in a one pot single step procedure (Scheme 60). POCl3 acted as chlorinating agent as well as an oxidant in the reaction which in situ generated acyl chlorides from acids making the condensation and cyclization easier and faster

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

• easy-to-handle potassium (trifluoromethyl)trimethylborate K+[CF3B(OMe)3]− as a CF3 source, molecular oxygen as the oxidant. However, another side reaction, substitution of the boronate by methoxy groups originating from the CF3 source, arose in this transformation. At the same year, the group of Fu

• -membered-ring transition state. Note that the presence of an olefin moiety in the product promised further conversion to other types of CF3-containing molecules. Later, the group of Wang [50] employed cheap copper chloride as the catalyst and a hypervalent iodine(III) reagent 1j as both the oxidant and the

• -oxadiazoles proceeded smoothly using TMSCF3 as a trifluoromethyl source and air as an oxidant to give the corresponding products in high yields. Various 1,3,4-oxadiazoles bearing electron-donating and electron-withdrawing groups at the para position on the aryl rings were well tolerated, although the latter

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

• as oxidant. Based on radical trapping experiments, the authors suggest that the reaction might proceed via a radical addition pathway. Wang et al. developed a 9-mesityl-10-methylacridinium tetrafluoroborate (Acr+-Mes BF4−) catalyzed radical thiol–ene reaction with broad scope (Scheme 12) [42]. Both

• radical. Yadav and co-workers presented a metal-free radical thiol–ene approach, using benzophenone as photoredox catalyst (Scheme 13) [43]. No sacrificial oxidant is required for this reaction as benzophenone is regenerated by hydrogen atom transfer to the anti-Markovnikov radical intermediate. Aliphatic

• to heteroaromatic substrates like indoles would produce valuable synthetic intermediates. By applying Rose Bengal as organic photocatalyst and aerobic oxygen as terminal oxidant, they were able to functionalize a series of indole derivatives and also could show the applicability of the thiocyanation

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

• -workers reported a metal-free protocol for the trifluoromethylation of styrenes with CF3SO2Na, tert-butyl hydroperoxide and benzoquinone (BQ) as oxidant. The reactions were run at 80 °C for 16 h to give mixtures of α-trifluoromethyl ketones 12 and the corresponding alcohols 13 (Scheme 6) [25]. The scope

• by oxidative trifluoromethylation with CF3SO2Na. In that case, 2-iodoxybenzoic acid (IBX) was used as the oxidant to generate the trifluoromethylated radical 22 and atmospheric oxygen was the oxygen source to form the ketone (Scheme 9) [28]. Synthesis of β-trifluoromethyl ketones from cyclopropanols

• Scheme 10. β-Trifluoromethyl ketones could also be obtained from allylic alcohols 25 by a cascade trifluoromethylation/1,2-aryl migration. Yang, Xia and co-workers employed sodium triflinate under metal-free conditions with ammonium persulfate as the oxidant that was necessary to generate the CF3 radical

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• ][12][13] with leaving groups, thus switching to an electrophile [14][15][16], or convert to an α-radical carbon with an oxidant [17][18][19]. β-Ketoesters are also inexpensive, abundant and commercially available, making them attractive substrates. In our continuing effort to develop green and atom

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

• . Surprisingly, we observed that the corresponding benzyl isothiocyanate was obtained in high yield. This may be attributed to the low stability of the corresponding S-trifluoromethyl benzyldithiocarbamate. Alternatively, the iodane 3 can act as an oxidant towards the intermediate benzyl dithiocarbamic acid

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

• Tathagata Mukherjee,
• Soumik Biswas,
• Andreas Ehnbom,
• Subrata K. Ghosh,
• Ibrahim El-Zoghbi,
• Nattamai Bhuvanesh,
• Hassan S. Bazzi and
• John A. Gladysz

Beilstein J. Org. Chem. 2017, 13, 2486–2501, doi:10.3762/bjoc.13.246

• CF3C6F11/toluene to 87:13 for CF3C6F11/acetone. The CF3C6F11/toluene partition coefficient of Rf11CH2I was also >99:<1. Next, CH3CN/C6F6 solutions of the fluorous aliphatic iodides (n = 11, 13) were treated with aqueous NaOCl and conc. HCl. The combination of HCl and a mild oxidant generates Cl2, providing

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• consisted in transforming the H-phosphinic acid into trivalent trimethylsilyl esters by reaction with hexamethyldisilazane followed by the oxidation with air followed by methanolysis [249]. A similar method that used a silylated intermediate and oxygen as oxidant was reported by Piettre et al. to produce

Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations

• Andrea Porcheddu,
• Evelina Colacino,
• Giancarlo Cravotto,
• Francesco Delogu and
• Lidia De Luca

Beilstein J. Org. Chem. 2017, 13, 2049–2055, doi:10.3762/bjoc.13.202

• -tetramethylpiperidine 1-oxyl) as the catalytic oxidising agent (Anelli–Montanari reaction) has been the main driving force behind the successful development of greener oxidation procedures [18][19]. The classic Anelli–Montanari oxidation requires aqueous NaOCl (bleach) as a co-oxidant, and it works in a CH2Cl2/H2O two

• the bpy/CuI/NMI catalyst system with Fe(NO3)3·9H2O, a cheaper, ligand-free co-oxidant (Scheme 1) [29][30]. This made the oxidative process more appealing for pharmaceutical applications, and specifically beneficial in the preparation of fragrances and food additives [31]. Despite the advances, the

• improved yields of all tested substrates: 3-phenyl-1-propanol, cyclohexanol and nonanol. Despite several attempts to improve the alcohol-to-aldehyde conversion, by, for instance, milling under an oxygen atmosphere and the use of more reactive co-oxidant catalysts [69], no significant improvements were

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

•  11) using 2,3-dichloro-5,6-dicyanoquinone (DDQ) as an efficient oxidant [67]. Su and co-workers have also reported an asymmetric version of the CDC reaction between terminal alkynes and sp3 C–H bonds under high speed ball milling conditions [68]. Several optically active 1-alkynyl

• desired product at 25 Hz within 30 min (Scheme 13) [69]. The oxidant DDQ was added in portions at 7 min intervals to get better yields. Different active methylene compounds like diethylmalonate, dibenzylmalonate, malonitrile, and unsymmetrical 1,3-dicarbonyl compounds were explored for the CDC reaction

• and co-workers reported bromination of phenol derivatives, chalcones, 1,3-dicarbonyl compounds using NaBr as bromine source and oxone as oxidant under ball-milling conditions [96]. Within 1 h they could isolate more than 90% of mono or poly-brominated products of phenol and 1,3-dicarbonyl compounds

Iodoarene-catalyzed cyclizations of N-propargylamides and β-amidoketones: synthesis of 2-oxazolines

• Somaia Kamouka and
• Wesley J. Moran

Beilstein J. Org. Chem. 2017, 13, 1823–1827, doi:10.3762/bjoc.13.177

• conditions to effect catalytic processes with sub-stoichiometric quantities of iodine compound in the presence of an oxidant [6][7][8][9][10][11]. In this regard, we have reported the use of iodoarenes as precatalysts in the cyclizations of N-alkenylamides 1 [12], δ-alkynyl β-ketoesters 2 [13] and 5-oxo-5

• [32][33][34][35][36]. Gao and co-workers described the I2-catalyzed cyclization of β-acylaminoketones using tert-butyl hydroperoxide as the oxidant; notably, adding DBU led to oxazole formation whereas adding K2CO3 generated oxazolines [37][38]. Our proposed new approaches to oxazoline formation

• -iodoanisole provided a diminished yield of 6a (Table 1, entry 2) [12]. The iodoarene was found to be essential for the conversion of the starting material, as its absence led to complete return of 4a (Table 1, entry 3). Using Oxone as oxidant led to essentially no conversion of 4a (Table 1, entry 4). Changing

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• cycloetherification reactions based on the use of in situ-generated chiral quaternary ammonium hypoiodite species. By using Maruoka-type catalysts B, which contain an iodide counter anion, in the presence of a simple oxidant like H2O2 they were able to generate a chiral hypoiodite species in situ, which then