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

Molecular rearrangements of superelectrophiles

• Douglas A. Klumpp

Beilstein J. Org. Chem. 2011, 7, 346–363, doi:10.3762/bjoc.7.45

• different than monocationic electrophiles. Superelectrophiles may also involve hypervalent species, such as protosolvated tert-butyl cation (7). Superelectrophiles are characterized by several types of reactions [8]. As very powerful electrophiles, they are best known for their reactions with weak

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• established that the asymmetric addition of TMSCN to aldehydes can be catalysed by both Lewis acids and Lewis bases [1]. A Lewis acid catalyst activates the aldehyde by formation of an aldehyde-Lewis acid complex (e.g., 4) whilst a Lewis base catalyst activates the TMSCN through formation of a hypervalent

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

Benzyne arylation of oxathiane glycosyl donors

• Martin A. Fascione and
• W. Bruce Turnbull

Beilstein J. Org. Chem. 2010, 6, No. 19, doi:10.3762/bjoc.6.19

• with external alcohols would be easier to achieve if the phenyl sulfonium ion was formed with a less reactive counter ion. However, oxidation of 1-ABT in the presence of ketal 14 with NIS [33], or hypervalent iodine (III) with either bis(acetoxy)iodobenzene [PhI(OAc)2] [34] or bis(trifluoroacetoxy

Controlling hazardous chemicals in microreactors: Synthesis with iodine azide

• Johan C. Brandt and
• Thomas Wirth

Beilstein J. Org. Chem. 2009, 5, No. 30, doi:10.3762/bjoc.5.30

• 4a reacted with n-butyllithium to give amide 6 in quantitative yields as shown in Scheme 2. Another way to form a stable iodine–azide bonds are hypervalent iodine compounds [30][31]. This source of reagent has indeed been used for radical azidonations in flask reactions [18] and resulted in an

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• scale. Togni managed very recently to circumvent these difficulties by using hypervalent iodine compounds such as 5 [33][34][35]. When 2,4,6-trimethylphenol was treated with the hypervalent iodine compound depicted below, the corresponding trifluoromethyl ether was obtained beside C-trifluoromethylation

• trifluoromethyl ethers. Mechanism of the oxidative desulfurization-fluorination. Umemoto's O-(trifluoromethyl)dibenzofuranium salts 4 as CF3-transfer agents. Togni's approach using hypervalent iodine compounds as CF3-transfer agents. TAS OCF3 as a nucleophilic OCF3-transfer agent. Nitration of trifluoromethoxy

m-Iodosylbenzoic acid – a convenient recyclable reagent for highly efficient aromatic iodinations

• Andreas Kirschning,
• Mekhman S. Yusubov,
• Roza Y. Yusubova,
• Ki-Whan Chi and
• Joo Y. Park

Beilstein J. Org. Chem. 2007, 3, No. 19, doi:10.1186/1860-5397-3-19

• recycling of the iodine reagent is concerned. The broad use of hypervalent iodine reagents is still hampered by tedious purification and recycling protocols. Commonly, purification relies on chromatography. Recently, tagging strategies for reagents and catalysts have widely been investigated that allow easy

• but could potentially be applied to most other iodine(III)-mediated reactions. Hypervalent iodine reagents 1 – 6. Iodine(III)-promoted iodination of arenes and concept of purification. Proposed intermediates. Monoiodination of arenes with m-iodosylbenzoic acid 6 (see Supporting Information File 1 for