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Search for "metal-free" in Full Text gives 288 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Selective benzylic C–H monooxygenation mediated by iodine oxides

  • Kelsey B. LaMartina,
  • Haley K. Kuck,
  • Linda S. Oglesbee,
  • Asma Al-Odaini and
  • Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

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  • widely used in industrial processes as promoters of autoxidation in the functionalization of benzylic C–H bonds of aryl alkanes, such as in the synthesis of terephthalic acid from p-xylene [21]. Metal-free oxidants have been used in benzylic C–H to C–O functionalization. Specifically, the use of
  • radicals are then captured by I2, generated in situ by the reduction of iodate. The benzylic iodide formed upon trapping is expected to be reactive, readily converting to the corresponding ester in carboxylic acid media. Conclusion A metal-free method for the selective monooxygenation of secondary benzylic
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Published 05 Mar 2019

Metal-free C–H mercaptalization of benzothiazoles and benzoxazoles using 1,3-propanedithiol as thiol source

  • Yan Xiao,
  • Bing Jing,
  • Xiaoxia Liu,
  • Hongyu Xue and
  • Yajun Liu

Beilstein J. Org. Chem. 2019, 15, 279–284, doi:10.3762/bjoc.15.24

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Published 29 Jan 2019

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

  • Yu Liu,
  • Qiao-Lin Wang,
  • Zan Chen,
  • Cong-Shan Zhou,
  • Bi-Quan Xiong,
  • Pan-Liang Zhang,
  • Chang-An Yang and
  • Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

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  • cyclization under transition-metal free conditions. With the addition of a radical scavenger such as TEMPO or BHT, the reaction was suppressed remarkably. In the same year, Dai’s group also reported the ring-opening-initiated tandem cyclization of cyclopropanols 91 with acrylamides 122 or 2-isocyanobiphenyls
  • transformation proceeded under transition-metal-free conditions with high selectivity and yields. A series of substituents such as methoxy, dimethoxy, trimethoxy, methyl, chloro, bromo, and fluoro on the aromatic ring of cyclopropanols were tolerated well. The mechanism is outlined in Scheme 35. A β
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Published 28 Jan 2019

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

  • Aude-Héloise Bonardi,
  • Frédéric Dumur,
  • Guillaume Noirbent,
  • Jacques Lalevée and
  • Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

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  • developments have promoted the emergence of metal-free catalysts that could in the future discard those based on metals, notably due to cost and environmental issues. Both categories of photoredox catalysts (PCs) will be described in this part and a series of structures is given in Scheme 2. 2.1 Metal-based
  • phosphorescent molecules, e.g., in the microsecond time scale [69]. Due to these really interesting properties, metal-based and metal-free TADF fluorescent materials have been extensively studied over the past few years, improving the photophysics of this new class of materials by molecular design [72][73][74
  • catalysts For some specific applications, it can be essential to develop metal-free systems because of potential toxicity, storage stability or bioaccumulation of metal for example. Organic photoredox catalysis has been largely studied in the past few years and is the topic of many reviews [17][40][45][49
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Published 12 Dec 2018

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

  • Rudolf Knorr and
  • Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

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  • fission may also be used to generate different metal derivatives of the nucleofugal anions as equilibrium components. Fluoride-catalyzed, metal-free desilylation admitted carbonyl addition but blocked the retro-addition. Keywords: alkoxide fission; desilylation; fragmentation; retro-addition; reversible
  • ). Preparation and cleavage of the adduct 18 of fluoren-9-one (15). Proton transfer from dicyclopropyl ketone (19) to 2Li. Metal-free release of the carbanion unit in 25 and its seizure by t-BuCH=O (→ 7); Bu = n-butyl. Supporting Information Supporting Information File 336: Ion-pair intermediate through
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Published 11 Dec 2018

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

  • Stanislav V. Lozovskiy,
  • Alexander Yu. Ivanov,
  • Olesya V. Khoroshilova and
  • Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

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  • noting, that compounds 3a–h have strictly cis-configuration of SO2Ar group and a vinyl substituent at C2 carbon. It should be mentioned that palladium-catalyzed isomerization of such (arylsulfonyl)allenes 2 into trans-butadienes 3 was described recently [23]. Herein, we have developed a novel metal-free
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Published 22 Nov 2018

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

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  • -Michael reaction between MBH carbonates derived from an acrylate/acrylonitrile and N-sulfonyl ketimines as C,N-binucleophiles catalyzed by DABCO, followed by elimination of SO2 under the influence of base and subsequent aromatization in an open atmosphere. Keywords: MBH carbonates; metal-free; N-sulfonyl
  • practical usage. Therefore, we are interested to devise a metal-free based general synthetic technique for the construction of substituted (2-hydroxyaryl)nicotinate/nicotinonitrile scaffolds. In recent years, our research group has been concentrated on the development of new synthetic methods for the
  • 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
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Published 02 Nov 2018

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

  • Robby Vroemans,
  • Yenthel Verhaegen,
  • My Tran Thi Dieu and
  • Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

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  • .14.246 Abstract A new metal-free one-pot three-component procedure towards fully substituted triazolochromenes has been developed, starting from commercially available materials. Salicylaldehydes and nitroalkenes were reacted under solvent-free conditions, followed by a 1,3-dipolar cycloaddition of the
  • the development of a metal-free sequential one-pot three-component reaction and the mechanochemically assisted 3-nitrochromene synthesis towards fully substituted triazolochromenes, without the isolation of the intermediate 3-nitrochromenes, have not been reported until now. Results and Discussion To
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Published 22 Oct 2018

Transition metal-free oxidative and deoxygenative C–H/C–Li cross-couplings of 2H-imidazole 1-oxides with carboranyl lithium as an efficient synthetic approach to azaheterocyclic carboranes

  • Lidia A. Smyshliaeva,
  • Mikhail V. Varaksin,
  • Pavel A. Slepukhin,
  • Oleg N. Chupakhin and
  • Valery N. Charushin

Beilstein J. Org. Chem. 2018, 14, 2618–2626, doi:10.3762/bjoc.14.240

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  • 10.3762/bjoc.14.240 Abstract The direct C–H functionalization methodology has first been applied to perform transition metal-free C–H/C–Li cross-couplings of 2H-imidazole 1-oxides with carboranyllithium. This atom- and step-economical approach, based on one-pot reactions of nucleophilic substitution of
  • . An alternative approach to exploit the C–X/C–M cross-coupling reactions, leading to heterocyclic boron clusters, is based on the C–H/C–M coupling strategy. One of the ways to realize these cross couplings is the transition metal-free methodology for direct C–H functionalization of azaheterocyclic
  • mentioned C–H/C–Li coupling reactions successfully as a nucleophilic partner. The direct transition metal-free C–H/C–Li cross-coupling reactions of 2H-imidazole 1-oxides 1a–d with 2 have been found to result in the novel carboranes 4a–d and 5a–d of various architectures. These transformations are able to be
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Published 12 Oct 2018

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

  • Amrita Das,
  • Mitasree Maity,
  • Simon Malcherek,
  • Burkhard König and
  • Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

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  • reports on direct C–H functionalization using transition metals or metal free [37][38][39] conditions and different sources of sulfur, for example arylsulfonyl chlorides, sodium arylsulfinates, sulfinic acids and arylsulfonyl hydrazides have been reported (Scheme 1). However, the protocols require
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Published 27 Sep 2018

Microfluidic light-driven synthesis of tetracyclic molecular architectures

  • Javier Mateos,
  • Nicholas Meneghini,
  • Marcella Bonchio,
  • Nadia Marino,
  • Tommaso Carofiglio,
  • Xavier Companyó and
  • Luca Dell’Amico

Beilstein J. Org. Chem. 2018, 14, 2418–2424, doi:10.3762/bjoc.14.219

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  • functionalize organic molecules is receiving considerable interest from the scientific community [2]. Thus, innovative light-driven metal-free synthetic methods have been successfully developed [3]. More recently, the microfluidic photoreactor (MFP) technology has revealed to be a key technology applicable for
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Published 17 Sep 2018

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

  • Lu Yang,
  • Yuwei Wu,
  • Yiming Yang,
  • Chengping Wen and
  • Jie-Ping Wan

Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210

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  • development of these metal-catalyzed cycloaddition strategies [33][34][35]. Alongside the vast progress happened in MAAC-based 1,2,3-triazole synthesis, the past decade has witnessed the emergence of another powerful cycloaddition tool for the 1,2,3-triazole synthesis: the metal-free cycloaddition of azides
  • construction, enamines with good stability and easy availability such as enaminones have exhibited also conspicuously versatile application in the metal-free synthesis of divergent 1,2,3-triazoles by directly acting as starting materials [51][52][53][54]. In 2016, Dehaen and co-workers [55] reported the
  • and tosyl azide employing water the sole reaction medium, a series of 4-acyl-NH-1,2,3-triazoles has been efficiently synthesized under catalyst-free and very mild heating conditions, thus providing the first water-mediated metal-free method toward the synthesis of 4-acyl-NH-1,2,3-triazoles. The
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Published 07 Sep 2018

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

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  • related transition metal-catalysed C–C bond forming reactions are in the top 5 most used reactions in medicinal chemistry [45]. Therefore, the development of metal-free variants of these types of reactions is a very attractive goal. An interesting approach was taken by König et al., who report the
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Published 03 Aug 2018

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

  • Xiang Li,
  • Pinhong Chen and
  • Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

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  • ) reagents were applied to oxidize transition metals [21][22][23][24][25]. In an alternative way, the electrophilic hypervalent iodine(III) reagents can activate alkenes directly in a metal-free manner. Based on this strategy, dichlorination [26], 1,2-difluorination [27], gem-difluorination [28
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Published 18 Jul 2018

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

  • Fateh V. Singh,
  • Priyanka B. Kole,
  • Saeesh R. Mangaonkar and
  • Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

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  • Sreenithya [92] developed a metal-free approach for the synthesis of 1,1'-dimethyl-3,3'-spirobi[indoline]-2,2'-dione (61) from N1,N3-dimethyl-N1,N3-diphenylmalonamide (60) using PIFA (31) in trifluoroethanol at room temperature. The spirolactam 61 was isolated in 75% yield (Scheme 21). According to the
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Published 17 Jul 2018

β-Hydroxy sulfides and their syntheses

  • Mokgethwa B. Marakalala,
  • Edwin M. Mmutlane and
  • Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

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  • electron-donating groups. Whilst this method offers a one-pot, transition metal-free and odorless approach to β-hydroxy sulfides utilizing atmospheric oxygen, an environmentally benign and cheap oxidant, its chief drawback is the incompatibility with aliphatic alkenes and dialkyl disulfides to provide the
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Published 05 Jul 2018

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

  • Nicole C. Neyt and
  • Darren L. Riley

Beilstein J. Org. Chem. 2018, 14, 1529–1536, doi:10.3762/bjoc.14.129

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  • developed a simple transition-metal-free continuous flow method for the reduction of aldehydes in aqueous media utilising sodium dithionite which does not generate or use molecular hydrogen. The process affords comparable yields to those obtained under batch conditions but in reduced reaction residence time
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Published 22 Jun 2018

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

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  • metal-free alternative to the previous methods of formation of sulfur heterocycles 70 has been reported by using elemental sulfur in the presence of cesium carbonate (Scheme 32) [72]. The strategy can be extended to the synthesis of the cyclic selenium analogs 71 by utilizing elemental selenium and
  • been further extended to the synthesis of a new series of molecules 77, where the central thiophene moiety is replaced by a 6-membered heterocycle, which is substituted by a gem-dimethyl or a cyclopropyl group. In this case, the reaction can be performed under metal-free conditions in the presence of a
  • Namitharan has very recently demonstrated that a one-pot palladium-catalyzed Heck coupling allows for transferring the aryl group of (diacetoxyiodo)arenes released after a metal-free methylenation reaction (Scheme 45) [110]. The latter that is performed by reacting PhI(OAc)2 with DMSO, applies to amidines 97
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Published 21 Jun 2018

Metal-free formal synthesis of phenoxazine

  • Gabriella Kervefors,
  • Antonia Becker,
  • Chandan Dey and
  • Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

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  • Gabriella Kervefors Antonia Becker Chandan Dey Berit Olofsson Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106-91 Stockholm, Sweden 10.3762/bjoc.14.126 Abstract A transition metal-free formal synthesis of phenoxazine is presented. The key step of the sequence is
  • ][8], are present in a variety of dyes [9], and can be applied in chemosensors and dye-sensitized solar cells (Figure 1) [10][11][12]. N-Arylphenoxazines were recently employed as photoredox catalysts in metal-free polymerizations [13]. The first synthesis of phenoxazine dates back more than 100 years
  • [14], and a range of synthetic routes to this target has since been developed [1]. Transition metal-free routes include the synthesis from 2-aminophenols and 3,4-dihaloarenes decorated with electron-withdrawing substituents, which proceed through a Smiles rearrangement (Scheme 1a) [15][16][17]. More
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Published 20 Jun 2018

Synthesis of trifluoromethylated 2H-azirines through Togni reagent-mediated trifluoromethylation followed by PhIO-mediated azirination

  • Jiyun Sun,
  • Xiaohua Zhen,
  • Huaibin Ge,
  • Guangtao Zhang,
  • Xuechan An and
  • Yunfei Du

Beilstein J. Org. Chem. 2018, 14, 1452–1458, doi:10.3762/bjoc.14.123

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  • trifluoromethylated 2H-azirine compounds. This method features mild reaction conditions, a simple operation, and metal-free characteristics. The presence of both, the biologically interesting CF3 group and the 2H-azirine skeleton in the products obtained might making them interesting for further applications in
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Published 15 Jun 2018

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

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  • partner) are taken into account. Other additives, such as additional bases, acids or catalysts were neglected. Review 1. Diaryliodonium salts 1.1. Acyclic diaryliodonium salts Acyclic diaryliodonium salts 1 find widespread application in numerous metal-free and transition metal-mediated electrophilic
  • waste. Examples for their atom-economical utilization, in which at least both aryl ligands are transferred, are still rare. A general approach would involve at first a metal-catalysed or metal-free arylation step of a suitable substrate A with the diaryliodonium salt 1 to give monoarylated intermediate
  • –boron bond formation gives one equivalent of arylboronic ester 4 and an iodoarene 2 through a metal-free boron arylation. Subsequent cross coupling under Suzuki conditions affords symmetrical biphenyls 3’ in good yields. Due to the temporary introduction and cleavage of the boron moiety the formal atom
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Published 30 May 2018

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

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  • application due to their reduced toxicity, ready availability and lower costs as replacement for transition metals leading to several “metal-free” like chemical transformations. The ongoing demand of modern synthetic chemistry for the development of catalytic enantioselective C–C bond formation reactions
  • different stereoelectronic properties by using aliphatic alcohols as a sole source of chirality [64]. Olofsson and Wirth et al. also jointly reported the synthesis of new structurally distinct chiral reagents 20 considering their interest towards asymmetric metal-free arylation [65]. In 1997, Wirth et al
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Published 30 May 2018

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

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  • , reports aimed at realizing efficient and selective metal-free C(sp3)–H transformations are rather limited; however, investigations by several research groups are still ongoing [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Hypervalent iodine reagents are now widely accepted as a safe
  • synthesis of lactones via the intramolecular oxidative cyclization of aryl carboxylic acids at the benzyl carbon under transition-metal-free conditions [52]. Based on our previous research and general interest in the unique reactivity of hypervalent iodine(III)–Br bonds [53][54][55][56], we report the
  • facilitate the activation of the benzylic C(sp3)–H bond are rare [21][57][58][59][60][61][62]. Furthermore, only a limited number of transition-metal-free methods have been reported; successful examples include the Wohl–Ziegler-type conditions [21], the sodium bromate system [57] for the conversion of
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Published 16 May 2018

Hypervalent iodine(III)-mediated decarboxylative acetoxylation at tertiary and benzylic carbon centers

  • Kensuke Kiyokawa,
  • Daichi Okumatsu and
  • Satoshi Minakata

Beilstein J. Org. Chem. 2018, 14, 1046–1050, doi:10.3762/bjoc.14.92

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  • operationally simple method under metal-free and mild reaction conditions can be used to produce a variety of acetates, which can be efficiently transformed into tertiary and benzylic alcohols. Decarboxylative functionalization using PhI(OAc)2/I2 system. Substrate scope. Reactions were conducted on a 0.5 mmol
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Published 15 May 2018

Imide arylation with aryl(TMP)iodonium tosylates

  • Souradeep Basu,
  • Alexander H. Sandtorv and
  • David R. Stuart

Beilstein J. Org. Chem. 2018, 14, 1034–1038, doi:10.3762/bjoc.14.90

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  • Souradeep Basu Alexander H. Sandtorv David R. Stuart Department of Chemistry, Portland State University, Portland OR 97201, United States 10.3762/bjoc.14.90 Abstract Herein, we describe the synthesis of N-aryl phthalimides by metal-free coupling of potassium phthalimide with unsymmetrical aryl
  • -deficient and sterically encumbered aryl groups. Keywords: arylation; C–N coupling; diaryliodonium; hypercoordinate iodine; metal-free; Introduction Imides are important structural units in a range of approved pharmaceuticals and agrochemicals (Scheme 1a) [1]. Despite the general prevalence of imides, N
  • , transition metals feature prominently in such methods, but even recent examples employ stoichiometric metal mediators [4]. Metal-free methods by classic SNAr are also attractive, but only possible on very electron-deficient arene substrates [5]. Diaryliodonium salts are useful reagents for metal-free aryl
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Published 11 May 2018
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