One-pot functionalisation of N-substituted tetrahydroisoquinolines by photooxidation and tunable organometallic trapping of iminium intermediates

• Joshua P. Barham,
• Matthew P. John and
• John A. Murphy

Beilstein J. Org. Chem. 2014, 10, 2981–2988, doi:10.3762/bjoc.10.316

• ][22][23][24]. Reports of organometallic additions to THIQs in this context are limited to aryl [25][26][27] and alkynyl [22][28][29][30] nucleophiles and the substrate scope is generally limited to N-aryl THIQs [31]. However, Li reported a hypervalent iodine mediated N-aryl THIQ oxidation which

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• hypervalent iodine reagents [9][10][11][12], and homogeneously or heterogeneously catalyzed multicomponent reactions [13][14]. Moreover, radical cyclizations predominantly conducted using Bu3SnH in the presence of azobisisobutyronitrile (AIBN) play a crucial role [15][16]. However, all these methods require

Exploration of C–H and N–H-bond functionalization towards 1-(1,2-diarylindol-3-yl)tetrahydroisoquinolines

• Michael Ghobrial,
• Marko D. Mihovilovic and
• Michael Schnürch

Beilstein J. Org. Chem. 2014, 10, 2186–2199, doi:10.3762/bjoc.10.226

• immediately. Although a broad range of (hetero)arenes undergo C–H-arylation under copper catalysis, heterocycles possessing acidic N–H bonds react at the nitrogen preferentially [52][53]. Moreover, directing groups such as acetyl (in combination with a hypervalent iodine aryl source) [42], or 2-pyridinyl

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ³,2-benziodaoxol-3-one

• Nico Santschi,
• Roman C. Sarott,
• Elisabeth Otth,
• Reinhard Kissner and
• Antonio Togni

Beilstein J. Org. Chem. 2014, 10, 1–6, doi:10.3762/bjoc.10.1

• -(trifluoromethyl)-3H-1λ3,2-benziodaoxol-3-one (3), a hypervalent-iodine-based electrophilic trifluoromethylating reagent, is described. Whereas considerations based on cyclic voltammetry and X-ray structural properties would predict an inferior reactivity when compared to the non-nitrated derivative 2, 19F NMR

• trifluoromethylation; 19F NMR kinetics; nitration; organo-fluorine; Introduction Since the advent of the hypervalent-iodine-based electrophilic trifluoromethylation reagents 1 and 2 in 2006 they have found widespread application in organic synthesis (Figure 1) [1][2][3][4]. Recently, increasing interest has been

IBD-mediated oxidative cyclization of pyrimidinylhydrazones and concurrent Dimroth rearrangement: Synthesis of [1,2,4]triazolo[1,5-c]pyrimidine derivatives

• Caifei Tang,
• Zhiming Li and
• Quanrui Wang

Beilstein J. Org. Chem. 2013, 9, 2629–2634, doi:10.3762/bjoc.9.298

• derivatives 5a–o. These incipient products undergo feasible Dimroth rearrangement to furnish the isolated [1,2,4]triazolo[1,5-c]pyrimidines 6a–o in moderate to high yields. Keywords: cyclization; hydrazones; hypervalent iodine; oxidation; rearrangement; [1,2,4]triazolo[1,5-c]pyrimidines; Introduction The

• an efficient synthesis of new [1,2,4]triazolo[1,5-c]pyrimidine derivatives from hypervalent iodine (IBD)-mediated oxidative cyclisation of aldehyde pyrimidinylhydrazones and consecutive Dimroth rearrangement in relatively good yields under very mild conditions. Results and Discussion The

• aldehydes, affording the corresponding hydrazones 4. In general, aromatic aldehydes provided higher yields than aliphatic aldehydes. In recent years, organo hypervalent iodine reagents have drawn considerable interests as versatile and environmentally benign oxidants with many applications in organic

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• ) redox couples could be accessed using external stoichiometric oxidants (i.e. Selectfluor or hypervalent iodine compounds) [73]. As schematically shown in Figure 1 this approach allows a double functionalization of simple alkenes with subsequent formation of new C–X and C–C bonds in a single catalytic

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• reaction conditions showed that cesium fluoride proved the best base. PhI(OAc)2 was the preferred oxidant over other hypervalent iodine compounds or sources of F+ or CF3+; additionally, the presence of a bis(oxazoline) as a ligand was beneficial to the reaction, as well as that of TEMPO to prevent

• -releasing groups at the 5-position, and considering the regioselective 3-functionalization of N-methylindole, the authors proposed the following catalytic cycle: 1) electrophilic palladation of indole, 2) oxidation of the resulting Pd(II) species by the combination of the hypervalent iodine reagent and

• trifluoromethylation; indeed, all of them used the same electrophilic CF3 source, namely Togni’s benziodoxolone reagent. M. Sodeoka and coworkers reported on the trifluoromethylation of indoles with Togni’s hypervalent iodine reagent in the presence of catalytic copper(II) acetate [82]. No additives were necessary

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime

• Raoni S. B. Gonçalves,
• Michael Dos Santos,
• Guillaume Bernadat,
• Danièle Bonnet-Delpon and
• Benoit Crousse

Beilstein J. Org. Chem. 2013, 9, 2387–2394, doi:10.3762/bjoc.9.275

• available reagents have been employed under metal-free conditions. A group [27] reported that the hypervalent iodine reagents (diacetoxyiodo)benzene (DIB) and phenyliodine bis(trifluoroacetate) (PIFA) could successfully promote the oxidation of aldoximes to the corresponding nitrile oxide. Those reagents

Regioselective 1,4-trifluoromethylation of α,β-unsaturated ketones via a S-(trifluoromethyl)diphenylsulfonium salts/copper system

• Satoshi Okusu,
• Yutaka Sugita,
• Etsuko Tokunaga and
• Norio Shibata

Beilstein J. Org. Chem. 2013, 9, 2189–2193, doi:10.3762/bjoc.9.257

• % yield (Table 1, entry 10). Using 4.0 equiv of Umemoto’s reagent 3b instead of 3a gave the product 2a in 27% yield (Table 1, entry 12). S-(Trifluoromethyl)benzothiophenium salt 3c [24], trifluoromethylsulfoxinium salt 3d [25], and hypervalent iodine(III) CF3 reagent 3e [26] did not proceed or provided

Zinc–gold cooperative catalysis for the direct alkynylation of benzofurans

• Yifan Li and
• Jérôme Waser

Beilstein J. Org. Chem. 2013, 9, 1763–1767, doi:10.3762/bjoc.9.204

• Yifan Li Jerome Waser Laboratory of Catalysis and Organic Synthesis, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCSO, BCH4306, 1015 Lausanne, Switzerland 10.3762/bjoc.9.204 Abstract The direct alkynylation of benzofurans was achieved for the first time using the hypervalent iodine

• successful in the case of the more complex drug 8-methoxypsoralen (8-MOP). Keywords: alkynylation; benzofurans; cooperative catalysis; direct functionalization; gold catalysis; hypervalent iodine; Introduction Benzofurans are important heterocycles frequently encountered in both bioactive compounds and

• the use of ethynylbenziodoxolones, which are cyclic hypervalent iodine reagents [22][23]. Nevertheless, the conditions we have used for other heterocycles gave only very low yields in the case of benzofurans. Herein, we would like to report the first catalytic direct C2-alkynylation of benzofurans 7

Hypervalent iodine/TEMPO-mediated oxidation in flow systems: a fast and efficient protocol for alcohol oxidation

• Nida Ambreen,
• Ravi Kumar and
• Thomas Wirth

Beilstein J. Org. Chem. 2013, 9, 1437–1442, doi:10.3762/bjoc.9.162

• Nida Ambreen Ravi Kumar Thomas Wirth Cardiff University, School of Chemistry, Park Place, Cardiff CF10 3AT, UK 10.3762/bjoc.9.162 Abstract Hypervalent iodine(III)/TEMPO-mediated oxidation of various aliphatic, aromatic and allylic alcohols to their corresponding carbonyl compounds was

• –Doering oxidation [3]. In synthetic chemistry, selective methods for the oxidation of alcohols are highly sought after, and methods with the ability to differentiate between various functional groups are desired. The use of hypervalent iodine reagents in organic chemistry has increased during recent years

• [4][5][6]. Hypervalent iodine compounds in general have emerged as versatile oxidizing agents with compounds such as DMP (Dess–Martin periodinane) and IBX finding regular utility as highly selective oxidizing agents [7][8][9]. The use of the nitroxyl radical TEMPO (2,2,6,6-tetramethylpiperidine-1

Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

• Stefan Riedmüller and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2013, 9, 1202–1209, doi:10.3762/bjoc.9.136

• . Furthermore, the reactivity of cyclic iodonium salts is compared with the reactivity of the corresponding cyclic bromonium analogues. Keywords: amination; carbazoles; hypervalent; iodine; iodonium salts; Introduction Carbazoles play an important role as core structural elements in natural products (e.g

• ] or the direct arylation [14][15] of the free NH-functionality of carbazole (path B). In the past decade, hypervalent iodine chemistry has undergone a renaissance and has developed to become a powerful area in synthetic organic chemistry. Open-chained iodonium salts are well explored in transition

• -metal-mediated reactions to construct new C–N bonds [16][17][18][19], whereas examples dealing with cyclic iodonium salts are underrepresented [20]. Our group is interested in the development of new C–X coupling strategies via (hypo)iodite or hypervalent iodine catalysis [21][22][23]. Here, we wish to

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• , mediated by metals such as Os, Mn, Pd, Ru, Fe, and Ag [26][27][28][29][30][31][32][33][34][35][36][37]. On the other hand, the metal-free hypervalent iodine(III)-mediated reactions have recently enjoyed a renaissance attracting extensive investigations [38][39]. It is particularly interesting in the case

The crystal structure of the Dess–Martin periodinane

• Albert Schröckeneder,
• Desiree Stichnoth,
• Peter Mayer and
• Dirk Trauner

Beilstein J. Org. Chem. 2012, 8, 1523–1527, doi:10.3762/bjoc.8.172

• the Dess–Martin periodinane (DMP), a hypervalent iodine reagent popular amongst synthetic chemists. In the solid state, the highly crystalline compound forms an intricate coordination polymer held together by intermolecular halogen and hydrogen bonds. Keywords: crystal structure; Dess–Martin

• periodinane; halogen bonds; hypervalent iodine; oxidant; Introduction The so-called Dess–Martin periodinane (DMP, 1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one, 1) has emerged as one of the most useful reagents for the oxidation of primary and secondary alcohols to the corresponding aldehydes and

• atoms have been observed in a range of other hypervalent iodine species [7][8][13][14][15][16][17], as well as iodine(I) compounds [18][19]. The ability to form halogen bonds may also account for the high solubility of DMP (1) in organic solvents. In addition to halogen bonds, the dimer is stabilized by

Approaches to α-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

• Sosale Chandrasekhar and
• V. Mohana Rao

Beilstein J. Org. Chem. 2012, 8, 1393–1399, doi:10.3762/bjoc.8.161

• , were thus formed in excellent yields (Table 3). The Hofmann rearrangement of carboxamides 9 was accomplished with one molar equivalent of phenyliodoso acetate [PhI(OAc)2] at 5–10 °C in methanolic KOH. The choice of the hypervalent iodine reagent was largely dictated by precedence [21][22][23]. The

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• being one of the “key green chemistry research areas” [4][5][6]. This review describes the current “state of the art” in organocatalyzed C–H activation reactions and highlights recent advances in sp2 and sp3 C–H bond functionalization. For simplicity, iodide or hypervalent iodine-mediated metal-free C–H

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• dual functionality consisting of a nitrile oxide and a pinacolyl boronate ester was prepared by mild hypervalent iodine oxidation (diacetoxyiodobenzene) of the corresponding aldoxime, without decomposition of the boronate functionality. The nitrile oxide was trapped in situ with a variety of

• dipolarophiles to yield aryl isoxazolines with the boronate ester function intact and available for subsequent reaction. Keywords: dipolar cycloaddition; heterocycle; nitrile oxide; hypervalent iodine oxidation; pinacol boronic acid esters; Introduction Metal-mediated coupling reactions to form carbon–carbon

• halogenation–dehydrohalogenation process is most common, several methods involving direct oxidative dehydrogenation of aldoximes have been reported, including the use of lead tetraacetate [22][23], mercury(II) acetate [24], hypervalent iodine [25][26], and manganese(IV) oxide [27]. We were interested in

Organic synthesis using (diacetoxyiodo)benzene (DIB): Unexpected and novel oxidation of 3-oxo-butanamides to 2,2-dihalo-N-phenylacetamides

• Wei-Bing Liu,
• Cui Chen,
• Qing Zhang and
• Zhi-Bo Zhu

Beilstein J. Org. Chem. 2012, 8, 344–348, doi:10.3762/bjoc.8.38

• chemical synthesis. This protocol not only adds a new aspect to reactions that use other hypervalent iodine reagents but also provides a wide space for the synthesis of disubstituted acetamides. Keywords: cleavage of carbon–carbon bond; (diacetoxyiodo)benzene; difunctionalized acetamides; novel oxidation

• ; 3-oxo-N-phenylbutanamides; Introduction Hypervalent iodine(III) reagents [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] have received much attention, as reflected by the plethora of publications and reviews [19][20][21][22][23]. This is due to their low toxicity, ready availability

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• [8], Et4N+Br− in the presence of hypervalent iodine reagents [9], and NBS in tetrabutylammonium bromide under molten salt conditions [10]. There is a recent report of the preparation of 3-bromocoumarins from acyclic precursors through bromination of a Wittig reagent with NBS followed by tandem Wittig

Hypervalent iodine(III)-induced methylene acetoxylation of 3-oxo-N-substituted butanamides

• Wei-Bing Liu,
• Cui Chen,
• Qing Zhang and
• Zhi-Bo Zhu

Beilstein J. Org. Chem. 2011, 7, 1436–1440, doi:10.3762/bjoc.7.167

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• hypervalent iodine compounds using electrochemistry [13]. Electrochemical microreactors for investigations of laminar flow have also been reported recently [14][15]. Results and Discussion The target of this research is to develop a simple and practical microreactor in which to carry out electrochemical

• reaction conditions described for 6a were also successful for 2,2-diphenylacetic acid (6b) and even an asymmetric reaction product could be formed through a mixture of phenylacetic acid (6a) and diphenylacetic acid (6b), although in smaller yield. Hypervalent iodine compounds can be used in organic

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• . A gold-catalyzed direct alkynylation of indole and pyrrole heterocycles 204 with a benziodoxolone-based hypervalent iodine reagent 203 has been developed [91]. The functional group tolerance was greatly increased when compared with direct alkynylation of indoles reported previously. Kar et al

One-pot gold-catalyzed synthesis of 3-silylethynyl indoles from unprotected o-alkynylanilines

• Jonathan P. Brand,
• Clara Chevalley and
• Jérôme Waser

Beilstein J. Org. Chem. 2011, 7, 565–569, doi:10.3762/bjoc.7.65

• to carry out (RT, and requires neither an inert atmosphere nor special solvents). Keywords: alkynylation; direct functionalization; gold; hypervalent iodine; indoles; Introduction Indoles are widespread in both natural products and synthetic drugs [1][2] and as a result, their synthesis and

• heterocycles has been intensively investigated [30][31][32][33][34]. Most of the developed methods involve the use of haloacetylenes. In contrast, our group has focused on the use of more reactive alkynyl hypervalent iodine reagents in order to expand the scope of direct alkynylation methods under milder

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• family of hypervalent iodine(III)-CF3 reagents as mild electrophilic trifluoromethylating agents suitable for reactions with carbon- and heteroatom-centered nucleophiles. These reagents further demonstrated generality in trifluoromethylation of a wide range of nucleophiles including the

• , enamines, and thiolate anions with these reagents, albeit in low to moderate yields [28]. Neutral hypervalent iodine(III)–CF3 reagent Initial attempts by Yagupolskii and Umemoto to synthesize iodonium salts with a trifluoromethyl group were unsuccessful. Whilst iodonium salts including p

• stability compared to the intermediates with Rf groups with more than one carbon atom. In 2006 Togni and co-workers reported a new family of hypervalent iodine compounds in which the CF3 group is bonded directly to the iodine atom. The overall synthetic protocol depends on a formal umpolung of the CF3 group

Synthesis and crystallographic analysis of meso-2,3-difluoro-1,4-butanediol and meso-1,4-dibenzyloxy-2,3-difluorobutane

• Bruno Linclau,
• Leo Leung,
• Jean Nonnenmacher and
• Graham Tizzard

Beilstein J. Org. Chem. 2010, 6, No. 62, doi:10.3762/bjoc.6.62

• hypervalent iodine species [21]. Such approaches often display poor stereoselectivity or result in rearrangement products. Treatment of 1,2-diols with SF4 [22][23], DAST [24], or deoxofluor [25] also leads to vicinal difluorides. Reaction with vicinal triflates has also been successful in some cases [7][26