Nonanebis(peroxoic acid): a stable peracid for oxidative bromination of aminoanthracene-9,10-dione

• Vilas Venunath Patil and
• Ganapati Subray Shankarling

Beilstein J. Org. Chem. 2014, 10, 921–928, doi:10.3762/bjoc.10.90

• an oxidant in the reaction, which re-oxidizes the HBr and utilizes up to 90–95% [25][26] of bromine. Various oxidants are used for this purpose [27][28][29][30]. Compared to these commonly used oxidants the use of peracids is likely to be limited due to their instability and the resulting storage

• at the expense of 1.25 equivalents of peroxide in 2 h (Table 2, entry 15). No product formation was observed in the absence of peracid (Table 2, entry 16). To confirm the efficiency of nonanebis(peroxoic acid), bromination was carried out using commercially available oxidants. The results obtained

• are summarized in Table 3. It was found that one equivalent of nonanebis(peroxoic acid) (contains two active oxygen atoms) (Table 3, entry 1) was sufficient to promote the dibromination of 1-aminoanthracene-9,10-dinone (1a) smoothly at room temperature and in less time. Amongst the other oxidants

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• products and 3,5-disubstituted pyrrole-2-carbonitriles 10 are obtained. Tsuge et al. reported the oxidation of pyrroline-3-carboxylates with chloranil [45] while pyrrole-2-carboxylates were obtained from the oxidation of pyrroline-2-carboxylate with chloranil [46][47] or DDQ [48]. Different oxidants were

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• phosphites (P(OR)3), activated through oxidants such as iodine, have been reported to give the corresponding phosphates in a Michaelis–Arbuzow type reaction [83][84][85] (Scheme 5). In order to improve atom economy and side product separation, we rationalized that in the phosphonium intermediate III

The renaissance of organic radical chemistry – deja vu all over again

• Corey R. J. Stephenson,
• Armido Studer and
• Dennis P. Curran

Beilstein J. Org. Chem. 2013, 9, 2778–2780, doi:10.3762/bjoc.9.312

• all sorts of heterocyclic ring systems, especially heteroaromatic systems [26][27], i) radical chemistry with water or in water [28], k) sequential transformations with both reductants and oxidants, l) radical chemistry in materials science [29][30], and m) high level computations of radicals and

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

• 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

• acetanilides by Z.-J. Shi et al., a copper-catalyzed process was developed by C. Chen and C. Xi and colleagues for the functionalization of pivanilides [84]. The latter methodology is simpler and more atom-economical since it does not require additives such as PivOH or stoichiometric metal salts as oxidants

• functionalized in moderate yields by using sodium trifluoromethanesulfinate (Langlois’s reagent) and tert-butyl peroxide with 10 mol % of copper(II) triflate (Table 19). The supposed mechanism implies single electron transfers where t-BuOOH and Cu(OTf)2 serve as oxidants (Figure 9). Interestingly, Langlois’s

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• derivatives are treated with α,β-unsaturated carbonyl compounds in the presence of ammonia to initially form dihydropyridines 1.38, which can ultimately be converted into the corresponding aromatic pyridine upon oxidation with a variety of oxidants such as MnO2, HNO2, HNO3 or cerium ammonium nitrate (CAN

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• ] or α,β-unsaturated carbonyl compounds are attractive synthetic targets of high economic and scientific interest [11][12][13][14][15][16][17]. Allylic oxidations of olefins to enones have classically been performed with strong oxidants such as chromium or other metal-based reagents [18][19]. In

Gold catalysis for organic synthesis II

• F. Dean Toste

Beilstein J. Org. Chem. 2013, 9, 2040–2041, doi:10.3762/bjoc.9.241

• catalysis with gold has seen notable advancements and is highlighted in several articles. The remarkable breakthroughs in oxidative transformations catalyzed by gold complexes, including those employing N-oxides as stoichiometric oxidants, have featured prominently in many recent innovations. Taken together

An easy direct arylation of 5-pyrazolones

• Hao Gong,
• Yiwen Yang,
• Zechao Wang and
• Chunxiang Kuang

Beilstein J. Org. Chem. 2013, 9, 2033–2039, doi:10.3762/bjoc.9.240

• yields decreased to trace, 31%, 0% and 22%, respectively (Table 1, entries 10–13). Other reaction parameters such as temperature and oxidants were also screened. When the reaction temperatures were 25 °C, 60 °C, and 120 °C, the yields decreased to 0%, 31% and 35%, respectively (Table 1, entries 14–16

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• oxidants [12][13][14], metal-catalyzed oxidation [15][16][17][18], UV light-mediated photochemistry [7][19][20][21], and visible light-mediated photochemistry [22][23]. Recently, the last approach has become a major research focus in organic chemistry. The enthusiasm surrounding this approach is partially

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

• Kegong Ji,
• Jonathan Nelson and
• Liming Zhang

Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227

• carboxylate; Introduction We reported in 2010 [1] that α-oxo gold carbenes could be conveniently generated as reactive intermediates in gold-catalyzed intermolecular oxidation of alkynes. By using pyridine N-oxides [1] and later 8-substituted quinoline N-oxides [2] as the external oxidants, this approach

• substrates from other well established, facile gold catalysis to the formation of distinctively different functional products in the presence of oxidants. The relatively low selectivity (i.e., ~7:1) of 5a-OAc over 5a-H was drastically improved upon catalyst screening. It was eventually found that the ratio

Damage of polyesters by the atmospheric free radical oxidant NO₃^•: a product study involving model systems

• Catrin Goeschen and
• Uta Wille

Beilstein J. Org. Chem. 2013, 9, 1907–1916, doi:10.3762/bjoc.9.225

• polymers, the mechanism of their degradation upon exposure to environmental oxidants is barely understood. In this work, model systems of important structural motifs in commercial high-performing polyesters were used to study the reaction with the night-time free radical oxidant NO3• in the absence and

• presence of other radical and non-radical oxidants. Identification of the products revealed ‘hot spots’ in polyesters that are particularly vulnerable to attack by NO3• and insight into the mechanism of oxidative damage by this environmentally important radical. It is suggested that both intermediates as

• well as products of these reactions are potentially capable of promoting further degradation processes in polyesters under environmental conditions. Keywords: environmental oxidants; free radicals; nitrate radicals; polyester degradation; product studies; reaction mechanisms; Introduction Polymers

Enantioselective synthesis of planar chiral ferrocenes via palladium-catalyzed annulation with diarylethynes

• Yan-Chao Shi,
• Rong-Fei Yang,
• De-Wei Gao and
• Shu-Li You

Beilstein J. Org. Chem. 2013, 9, 1891–1896, doi:10.3762/bjoc.9.222

• protecting group on the nitrogen of L-Val-OH was changed to Ac or Cbz, the enantioselectivity slightly decreased (94% ee, entries 10 and 11, Table 1). The oxidants such as Cu(OAc)2, Cu(OTf)2, Ag2CO3, Ag2O, AgOAc and benzoquinone (BQ) were examined but none of them could improve the yield efficiently (for

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

• Jincan Zhao,
• Hong Fang,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2013, 9, 1718–1723, doi:10.3762/bjoc.9.197

• , Fe2O3 and Fe3O4 tested (Table 1, entries 4–8). Application of other oxidants such as K2S2O8, H2O2 (30% aqueous solution) or TBPB did not afford any improvements (Table 1, entries 9–11). A decreased loading of Fe(acac)3 to 10 mol % or an increased amount of DTBP to 5.0 equiv and a lower temperature (110

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• ][34][35][36][37][38]. Various catalytic systems have been developed by Jung [39] and Larhed et al. [40][41][42][43] by employing diverse variations in oxidants, ligands or palladium complexes [44][45][46][47]. Nowadays, several competent methods are also known to achieve this transformation with

• different reaction conditions employing base-free, ligand-free conditions or by using conventional oxidants such as oxygen, benzoquinone, Cu salts, etc. [48][49][50][51][52][53]. In this article we report two new protocols for Heck cross-coupling reactions: (i) a stable SPO ligated palladium complex 6

An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles

• Alexandre Jean,
• Jérôme Blanchet,
• Jacques Rouden,
• Jacques Maddaluno and
• Michaël De Paolis

Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168

• (Scheme 1). In the course of our investigations, we observed that pyrrolidine 4 could be converted into the corresponding pyrrole 5 by a simple isomerization, avoiding the use of oxidants. We describe herein the details of these observations and the scope of this methodology for the concise preparation of

Mechanistic studies on the CAN-mediated intramolecular cyclization of δ-aryl-β-dicarbonyl compounds

• Brian M. Casey,
• Dhandapani V. Sadasivam and
• Robert A. Flowers II

Beilstein J. Org. Chem. 2013, 9, 1472–1479, doi:10.3762/bjoc.9.167

• -electron oxidations employing δ-aryl-β-dicarbonyl compounds have been carried out on arenes containing pendant β-ketoesters [10][11]. When Mn(III)-based oxidants are employed, secondary oxidations of the 2-tetralone products can occur [10][11]. Cerium(IV) ammonium nitrate (CAN) is a versatile, inexpensive

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• Scheme 3) [22][24][27]. On the other hand, the same spirocyclic ketone is obtained in the 9,10-dicyanoanthracene (DCA) and biphenyl (BP) sensitized PET reaction of probe II, while reactions of this substrate with certain oxidants afford ring-expanded ketone and enone products (right in Scheme 3) [23][25

• fast oxidation of the more stable isomer 10 by stronger oxidants such as CuCl2 or Cu(OTf)2 occurs to give the stable tertiary carbocation 13, which is then captured by Cl− or MeCN. In order to explore the generality of the proposed counter-anion-dependent reactivity switch in the nature of copper(II

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• selective oxidation of organic substrates under mild and environmentally benign conditions represents one of the major challenges in organic synthesis [1]. In this context, the replacement of traditional oxidants, often used in stoichiometric amounts, with molecular oxygen is mandatory in order to improve

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

• Matthew T. Richers,
• Chenfei Zhao and
• Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

• stoichiometric n-butyllithium for the iodine reaction. The conversion of the aminals formed from the condensation of aminobenzaldehydes and secondary amines to the corresponding dihydroquinazoline and quinazolinone structures under mild and catalytic conditions would be preferable to using harsh oxidants and

Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C–H functionalization

• Ryan Pearson,
• Shuyu Zhang,
• Gang He,
• Nicola Edwards and
• Gong Chen

Beilstein J. Org. Chem. 2013, 9, 891–899, doi:10.3762/bjoc.9.102

• cyclization and oxidation steps can be performed in one step to give the phenanthridines in a shorter procedure. A variety of oxidants, such as 1,4-benzoquinone (BQ), KMnO4, ceric ammonium nitrate (CAN), and copper salts were examined [46]. The combination of PhI(OAc)2 (2 equiv) and Cu(OAc)2 (2 equiv

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• furnished the tetrabromide 207, which on hydrolysis (H2O, Al2O3) provided the dibromo diol 208 [138]. A careful study of the oxidation of several conjugated bisallenes with different oxidants has been carried out by Pasto and co-workers [139]. As summarized in Scheme 50, the tetramethylbisallene 24 yields

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• rearrangement that is operative during the alkylation of indoles [46]. In 1969, Fujiwara and Moritani reported the alkenylation of arenes catalyzed by Pd(OAc)2, using Cu(OAc)2 or AgOAc as oxidants [47]. This strategy provides a convenient method for the synthesis of olefins linked to heteroarenes, including

• -substituted indoles. Coupling of indole and 2-methyl-2-butene in the presence of Pd(OAc)2 (40 mol %), Cu(OAc)2 and AgOTf as the co-oxidants in MeCN constitutes a simple route to N-prenylated indoles 8 (Scheme 7) [54]. This mild reaction, which exhibits broad functional-group tolerance, can be successfully