Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• the types of products that can be formed from radical reactions of ene-sulfonamides. Results and Discussion Cyclizations of N-sulfonylindoles Radical cyclizations of 3-substituted N-alkylindoles provide spirocyclic indolines [12][13]. Nicolaou used this reaction as a key step in a synthesis of the

• '-formamidoethyl)-2-oxindoles. These transformations add new dimensions to the growing radical chemistry of ene-sulfonamides. (a) Radical reactions of ene-sulfonamides give diverse isolated products; (b) these products are often derived from transient imine intermediates. Isolation of stable imines strengthens the

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

• Dominik Lenhart and
• Thorsten Bach

Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86

• lactone and lactam substrates, the latter products were the only products isolated. For the six-membered lactones and lactams and for cyclopentenone the simple addition products prevailed. Keywords: cyclization; electron transfer; iridium; photochemistry; photoredox catalysis; radical reactions

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• -heterolytic fragmentation in which either an electrofugal (E+) or nucleofugal (Nu−) group is transferred from a position adjacent to respective positively and negatively charged radical centers (Scheme 1). These fragmentation reactions produce neutral radicals, which then participate in typical radical

• reactions, including C–C bond formation and addition to unsaturated centers. Because of their importance, α-heterolytic fragmentation reactions of radical anions and cations have been intensively studied from synthetic and mechanistic perspectives [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25

Multicomponent reactions II

• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 115–116, doi:10.3762/bjoc.10.7

• again presents a snap shot of this highly dynamic field. With the traditional formats of letters, full papers, and reviews it spans the broad range of modern chemistry, including organocatalytic, organometallic, transition metal-catalyzed, radical reactions, condensation and isonitrile-based MCR

Synthesis of nucleotide–amino acid conjugates designed for photo-CIDNP experiments by a phosphotriester approach

• Tatyana V. Abramova,
• Olga B. Morozova,
• Vladimir N. Silnikov and
• Alexandra V. Yurkovskaya

Beilstein J. Org. Chem. 2013, 9, 2898–2909, doi:10.3762/bjoc.9.326

• , SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia 10.3762/bjoc.9.326 Abstract Conjugates of 2’-deoxyguanosine, L-tryptophan and benzophenone designed to study pathways of fast radical reactions by the photo Chemically Induced Dynamic Nuclear Polarization (photo-CIDNP) method were obtained by the

• approach appeared to meet the requirements for the in situ NMR detection of the radical reactions with microsecond time resolution by Chemically Induced Dynamic Nuclear Polarization (CIDNP). Based on our fruitful experience in the CIDNP investigation of conjugates 1, 6, 7, and 8 (will be published soon

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

• of organic radical chemistry that delivered groundbreaking results, especially in organic synthesis. By the 1990’s, radical reactions (especially cyclizations) were broadly recognized as powerful tools to make molecules. This Renaissance I in organic radical chemistry was built on prior renaissances

• the new immigrants again come from a background of synthesis, often with a focus on catalysis. They bring along new ideas and different perspectives. As both new and established researchers have dared to try radical reactions in challenging new areas, their results have lit up the field. Successful

Stereoselectively fluorinated N-heterocycles: a brief survey

• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

• enantioselectivity. 6.5 Radical reactions Examples of direct fluorination of C–H bonds with fluorine-containing radicals are rare in the literature, especially if stereoselective versions of such reactions are sought. However, this transformation can be a very effective and concise method for synthesising

• fluorinated N-heterocycles. For example, L-cis-3-fluoroazetidine-2-carboxylic acid (73) was synthesised in one step from the corresponding amino acid 72 by photofluorination with fluoroxytrifluoromethane as the source of the fluorine radical, in 53% yield [72] (Scheme 9). Radical reactions can also be used to

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

• pentoxide, N2O5, which is formed through reversible recombination of NO2• with NO3•, by trace amounts of water present in acetonitrile, but this was not further explored. By performing the radical reactions in dichloromethane, potentially interfering reactions involving the solvent, which could complicate

Flow Giese reaction using cyanoborohydride as a radical mediator

• Takahide Fukuyama,
• Takuji Kawamoto,
• Mikako Kobayashi and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2013, 9, 1791–1796, doi:10.3762/bjoc.9.208

• characteristics, which include efficient mixing, efficient mass and heat transfer, and high operational safety [19][20][21][22][23]. Radical reactions also benefit from these advantages, and we have reported both photo- [24][25][26] and thermally-induced [27][28][29][30] radical reactions that are facilitated by

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• , such as simple multiple bonds or C–H bonds, are combined with multifunctionalization processes, they would become more efficient synthetic methods [6][7][8][9]. In this regard, radical reactions are capable of realizing multifunctionalization of inactivated organic molecules due to their high

Bromination of hydrocarbons with CBr₄, initiated by light-emitting diode irradiation

• Yuta Nishina,
• Bunsho Ohtani and
• Kotaro Kikushima

Beilstein J. Org. Chem. 2013, 9, 1663–1667, doi:10.3762/bjoc.9.190

• without any additives, through radical reactions induced by irradiation with light from commonly used light-emitting diodes (LEDs) [30]. In this reaction, additives, catalysts, heating, and inert reaction conditions are all unnecessary. Results and Discussion First, the bromination of cyclohexane under

Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

• Andreas Gansäuer,
• Meriam Seddiqzai,
• Tobias Dahmen,
• Rebecca Sure and
• Stefan Grimme

Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185

• substituted anilines that constitutes the C–C bond forming event of indoline synthesis via homolytic substitution with computational methods. The results are of general interest for the understanding of radical addition to electron rich arenes and should be helpful in the design of novel radical reactions

Preparation of optically active bicyclodihydrosiloles by a radical cascade reaction

• Koichiro Miyazaki,
• Yu Yamane,
• Ryuichiro Yo,
• Hidemitsu Uno and
• Akio Kamimura

Beilstein J. Org. Chem. 2013, 9, 1326–1332, doi:10.3762/bjoc.9.149

• cyclization process is also an interesting synthetic reaction that often provides an efficient method [11][12][13]. Recently, we reported a new type of higher-order radical cascade reaction between chiral enyne compounds and Bu3SnH, which is recognized as a useful reagent in radical reactions [14]. In this

• methylthiyl radical also undergoes such a radical cascade reaction to stereoselectively give bicyclic dihydrothiophenes [16]. We expected that tris(trimethylsilyl)silane (Me3Si)3SiH [17], which is a well-known alternative to Bu3SnH in radical reactions [18][19][20][21][22], would be a good promoter of a

Cascade radical reaction of substrates with a carbon–carbon triple bond as a radical acceptor

• Hideto Miyabe,
• Ryuta Asada and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2013, 9, 1148–1155, doi:10.3762/bjoc.9.128

• mild reaction conditions, because radical intermediates are not charged species. Therefore, a number of extensive investigations into sequential radical reactions have been reported over the past fifteen years and significant progress has been made in recent years [21][22][23][24][25][26][27][28][29

• (Figure 1) [37][38][39][40][41][42][43]. Enantioselective radical reactions have been intensively studied over the past fifteen years. Compared with stereocontrol studies on intermolecular radical reactions, the enantioselective stereocontrol in radical cyclizations still remains a major challenge [44][45

• for preparing functionalized cyclic compounds with multiple stereocenters. These studies offer opportunities for further exploration of fascinating possibilities in the realm of cascade radical reactions. Cascade bond formation based on radical reactions. Our method for controlling the geometry of

Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines

• Kebin Mao,
• Guoqin Fan,
• Yuanhong Liu,
• Shi Li,
• Xu You and
• Dan Liu

Beilstein J. Org. Chem. 2013, 9, 621–627, doi:10.3762/bjoc.9.69

• substitution reactions [8][9], radical reactions [10] and Pd-catalyzed reactions [11]. Thus, allylic amines have been used for the synthesis of numerous heterocycles and bioactive amines, such as α- and β-amino acids [12][13][14][15], different alkaloids [16], aminoallylsilanes [17], aminoepoxides [18

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

• Teruo Umemoto,
• Lloyd M. Garrick and
• Norimichi Saito

Beilstein J. Org. Chem. 2012, 8, 461–471, doi:10.3762/bjoc.8.53

• , while the reactions of Ar2S2 with XeF2/Et4NCl gave a mixture of cis- and trans-isomers according to Janzen's report [52]. Janzen proposed radical reactions with Cl· species [52]. The Cl2/KF reactions are ionic in nature, in which trans-form salts 8 exclusively form and react with Cl2 to give the trans

Koch–Haaf reaction of adamantanols in an acid-tolerant hastelloy-made microreactor

• Takahide Fukuyama,
• Yu Mukai and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2011, 7, 1288–1293, doi:10.3762/bjoc.7.149

• practical organic syntheses using flow microreactors, and we have reported thus far examples of Pd-catalyzed coupling reactions [11][12][13], radical reactions [14][15][16], and photoreactions [17][18][19][20][21]. Carbonylation reactions are a powerful tool for the introduction of carbon monoxide into

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• indicated that aromatics in close proximity to an incipient carbocation could accelerate tosylation reactions by up to 1800-fold [21]. Similarly, neighbouring aromatics have been shown to have an effect on radical reactions proceeding through a polarised transition state [22]. Clearly there is excellent

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• Compostela, Campus Vida, 15782 Santiago de Compostela, Spain 10.3762/bjoc.6.133 Abstract The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) to

• the Ru(II)–Ru(III) mixed-valence compound [(p-cymene)Ru(μ-Cl)3RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions. Keywords: Grubbs catalyst; indenylidene ligands; Kharasch reaction; microwave heating; olefin

• induced by polyhalogenated substrates is in line with the general mechanism postulated for ruthenium-catalyzed atom transfer radical reactions, as it involves a reversible oxidation of the metal center [32][33]. Under the experimental conditions adopted for our study, conversion of indenylidene precursor

Physical organic chemistry

• John A. Murphy

Beilstein J. Org. Chem. 2010, 6, 1025–1025, doi:10.3762/bjoc.6.116

• kinetics of radical reactions. Applications to complex reactions in biology, polymer chemistry and electronic materials are ever more prevalent, and add to contributions in ‘small molecule’ chemistry. Novel experimental techniques combined with the revolution in computational chemistry give new impetus to

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

• Giorgio Bencivenni,
• Riccardo Cesari,
• Daniele Nanni,
• Hassane El Mkami and
• John C. Walton

Beilstein J. Org. Chem. 2010, 6, 713–725, doi:10.3762/bjoc.6.84

• ; indium; Introduction The number of applications of indium [1][2][3][4][5][6], gallium [7][8][9][10][11] and other group 13 metal derivatives, as promoters of radical reactions, has been increasing ever since the original work of Baba and co-workers with dichloroindium hydride [12][13][14][15][16

Radical carbonylations using a continuous microflow system

• Takahide Fukuyama,
• Md. Taifur Rahman,
• Naoya Kamata and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2009, 5, No. 34, doi:10.3762/bjoc.5.34

• radical centers is high enough to compete with the premature quenching by tin hydride (Scheme 1). Encouraged by our previous successes with both radical reactions [12] and metal-catalyzed carbonylation reactions using microflow devices [18][19][20], we decided to examine a continuous microreaction system

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• ) [114]. 5.4. Parson. Radical cyclization The development of novel cascade (or domino) radical reactions is an active area of current research, and one approach to the mitomycin ring system focused on the application of 1-6-hydrogen atom transfer to create a pyrrolidinone radical, which could then

Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

• David M. Hodgson and
• Leonard H. Winning

Beilstein J. Org. Chem. 2008, 4, No. 38, doi:10.3762/bjoc.4.38

• also considered, however the practical difficulties of using this reagent (prone to polymerisation in the absence of a radical inhibitor) precluded its application. Using 3-methyl-2-butenal led to only rearranged–reduced product 8 (79%). In many cases, radical reactions are considered to proceed

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• sequences. Recent examples of the use of silicon-containing tethers have centred upon the Diels-Alder reaction,[4][5] radical reactions[6] and olefin metathesis reactions. There have been reports of applying the temporary tethering methodology of silicon species to the P-K reaction, but with limited success