Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• method where both the glycosyl donor and the acceptor are present when the promoter is added, preactivation can generate reactive intermediates as the resting state allowing spectroscopic analysis such as low temperature NMR studies to better characterize the intermediate. This can help gaining a deeper

Difunctionalization of alkenes with iodine and tert-butyl hydroperoxide (TBHP) at room temperature for the synthesis of 1-(tert-butylperoxy)-2-iodoethanes

• Hao Wang,
• Cui Chen,
• Weibing Liu and
• Zhibo Zhu

Beilstein J. Org. Chem. 2017, 13, 2023–2027, doi:10.3762/bjoc.13.200

• and biological properties [26][27]. Organoperoxides have wide applications in the field of organic synthesis, as radical initiators, oxidants that replace transition metal oxidants, and key reactive intermediates in diverse organic synthesis reactions [28][29][30], as well as in medicinal chemistry

Mechanochemical synthesis of thioureas, ureas and guanidines

• Vjekoslav Štrukil

Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178

• reactions were performed which has led to the discovery of reactive intermediates, new phases and novel topologies in systems previously studied only by ex situ analyses [25][26]. To overcome the inability of PXRD to provide structural information on amorphous materials, a method based on real time in situ

• 27, it has been explicitly stated in the literature that these compounds are very reactive intermediates and immediately decompose to isothiocyanates and 1H-benzotriazole (HBt). With this in mind, we investigated the possibility to run the thiocarbamoylation reaction of para-substituted anilines as

• synthetic tool that enables the synthesis and isolation of molecular species as bench-stable chemicals, that are normally considered as reactive intermediates in solution environment. The observed reactivity of thiocarbamoyl benzotriazoles prompted us to examine their reaction with ammonia, as a potential

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• asymmetric α-amination reactions [145]. By using hydroxylamines 43 as simple N-containing reagents, the addition of these compounds to trichloroacetonitrile gives the reactive intermediates 44, which then serve as versatile electrophilic N-transfer reagents under asymmetric triazolium salt L catalysis

Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block

• Yuta Isoda,
• Norihiko Sasaki,
• Kei Kitamura,
• Shuji Takahashi,
• Sujit Manmode,
• Naoko Takeda-Okuda,
• Jun-ichi Tamura,
• Toshiki Nokami and
• Toshiyuki Itoh

Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93

• pathway [30]. Although it is hard to exclude another reaction mechanism involving oxocarbenium ions as reactive intermediates, the commonly accepted reactivity difference between α- and β-isomers of glycosyl triflate 3 seems to explain the observed selectivity well. Next, we attempted to synthesize the

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

• Anna S. Zalivatskaya,
• Dmitry S. Ryabukhin,
• Marina V. Tarasenko,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya,
• Elena V. Grinenko,
• Ludmila V. Osetrova,
• Eugeniy R. Kofanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2017, 13, 883–894, doi:10.3762/bjoc.13.89

• study protonated forms of the oxadiazoles as reactive intermediates by means of NMR and DFT calculations. It should be noted, that the metal-catalyzed hydroarylation of C=C bonds is widely used in organic synthesis [26][27]. The most efficient catalysts for these purposes are complexes of the transition

• species D. Thus, the NMR data reveal that the protonation of 5-styryl-substituted 1,2,4-oxadiazoles in superacids results in the formation of their relatively stable N4-protonated forms. However, these species do not react with aromatic π-nucleophiles (vide infra). Most probably, those reactive

• intermediates, generated under the protonation of substrates 1, are N4,C-diprotonated species D. The experimental results from the hydroarylation reactions of the side chain C=C double bond of oxadiazoles 1a–n with various arenes under the action of different acidic reagents leading to oxadiazoles 2a–za are

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• chemical processes that are difficult to perform under batch conditions, e.g., involving reactive intermediates or competitive reactions [74][75]. Compared to batch setups, performing reactions under continuous flow allows a fine tuning of the contact time between intermediates and catalytic active phase

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• of the channels, volume), and on the flow rate. The residence time is one of the crucial factors to be considered in optimizing flow reactions, especially when unstable or short-lived reactive intermediates are concerned. Microreactor technology provides also several benefits. Safety benefits

• the possibility to generate highly reactive intermediates, such as halomethyllithium carbenoids, that need to be used under internal-quenching technique in batch mode. In 2014, the first example of effective external trapping of a reactive chloromethyllithium (CML) has been reported [28]. α

Dimerization reactions of aryl selenophen-2-yl-substituted thiocarbonyl S-methanides as diradical processes: a computational study

• Michael L. McKee,
• Grzegorz Mlostoń,
• Katarzyna Urbaniak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 410–416, doi:10.3762/bjoc.13.44

• intermediate, delocalized diradical species. The influence of selenium as a ‘heavy atom’ for stabilization of this intermediate has been emphasized. Keywords: 1,3-dipolar cycloadditions; reaction mechanisms; reactive intermediates; thiocarbonyl S-methanides; thioketones; Introduction Thiocarbonyl S

• -methanides 1 belong to the class of S-centered 1,3-dipolar species, which were identified by Huisgen as reactive intermediates formed via nitrogen extrusion from 2,5-dihydro-1,3,4-thiadiazoles 2 [1][2]. In spite of the fact that several methods are reported for the preparation of these precursors, the most

• with solvation effects (assuming ∆H(solv) = ∆G(solv)) to obtain enthalpies at 298 K in THF (Equation 1). The calculated entropy was used to determine the –T∆S term to form free energies at 298 K in THF (Equation 2). Structures of the reactive intermediates as a diradical 6 or a zwitterion 7 in the

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• -on-a-chip approach. Kinetic and mechanistic studies The rapid analysis produced in flow NMR can be used for the detection of reactive intermediates and consequently for studying reaction mechanisms and the rapid optimization of a chemical process. The first example was described by Nakakoshi et al

Green chemistry

• Luigi Vaccaro

Beilstein J. Org. Chem. 2016, 12, 2763–2765, doi:10.3762/bjoc.12.273

• the safety of a chemical procedure, but also the proper selection of solvents, starting materials, and technologies used to generate and control reactive intermediates. In addition, the need for minimizing toxic waste and the respective disposal cost highlights how crucial it is to consider the

Superelectrophilic activation of 5-hydroxymethylfurfural and 2,5-diformylfuran: organic synthesis based on biomass-derived products

• Dmitry S. Ryabukhin,
• Dmitry N. Zakusilo,
• Mikhail O. Kompanets,
• Anton A.Tarakanov,
• Irina A. Boyarskaya,
• Tatiana O. Artamonova,
• Mikhail A. Khohodorkovskiy,
• Iosyp O. Opeida and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2016, 12, 2125–2135, doi:10.3762/bjoc.12.202

• (Scheme 1). All species A, B, C, and D may play a role as reactive intermediates derived from 1a and 2 in superacids. To estimate the electrophilic properties of cations A, B, C, and D we performed quantum chemical calculations by the DFT method (Table 1). HOMO and LUMO energies, global electrophilicity

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• reactive intermediates. Three important types of enantioconvergent catalysis are specifically discussed herein: type I – stereomutative, type II – stereoablative [8], and type III – parallel kinetic resolution [9]. The primary criteria for all enantioconvergent catalytic reactions are: The starting

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

• Valerij A. Nikolaev,
• Jury J. Medvedev,
• Olesia S. Galkina,
• Ksenia V. Azarova and
• Christoph Schneider

Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180

• ; transition-metal-catalyzed reactions; Wolff rearrangement; Introduction Transition-metal-catalyzed reactions of diazocarbonyl compounds (DCC) with different organic substrates comprise a powerful tool of organic synthesis [1][2][3][4][5][6][7][8]. Of prime importance was found to be the ability of reactive

• intermediates generated from diazo compounds (ammonium, oxonium, C=X-ylides and others) to react with a variety of electrophiles/nucleophiles yielding complex and challenging organic molecules from relatively straightforward initial compounds [9][10]. The research group by Hu and co-workers elaborated recently

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

One-pot synthesis of 4′-alkyl-4-cyanobiaryls on the basis of the terephthalonitrile dianion and neutral aromatic nitrile cross-coupling

• Roman Yu. Peshkov,
• Elena V. Panteleeva,
• Wang Chunyan,
• Evgeny V. Tretyakov and
• Vitalij D. Shteingarts

Beilstein J. Org. Chem. 2016, 12, 1577–1584, doi:10.3762/bjoc.12.153

• -coupling; cyanoarenes; reactive intermediates; reductive alkylation; Introduction Alkylcyanobiphenyls are well known largely due to their mesogenic properties, which were discovered by Gray in the 1970th [1][2]. Alkylcyanobiphenyls and their analogs (e.g., dialkyl and alkoxy alkyl derivatives) are still

The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• to 3c+·, followed by α-cleavage to F3+·. Two subsequent hydrogen rearrangements result in the conjugated reactive intermediates G3+· and H3+·, which may be followed by the elimination of water to I3+· that upon α-cleavage yields the benzyl cation J3+. Finally, PMA43 reveals a clean formation of the

Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

• Sean P. Bew,
• Glyn D. Hiatt-Gipson,
• Graham P. Mills and
• Claire E. Reeves

Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103

• rac-3 (Scheme 1). The formation and reaction of these reactive intermediates with NO generates O3 and mixtures of IPNs, i.e., rac-7–(E)-10 (Scheme 1). Contributing to the complexity of the climate chemistry associated with 1 is its oxidation to ketones, e.g., 11 and rac-6 and aldehydes, e.g., rac-5

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• of intermediates have been proposed to be the reactive intermediates in many reactions such as aldol, Michael, Mannich, and α-functionalization (α-chlorination, α-amination, α-fluorination) reactions. Proline-type organocatalysts are considered priviliged, because their corresponding enamines exist

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• ]. Meanwhile, the Breslow intermediate is produced from the aldehyde by the thiazolium 31-derived NHC. The union of these two reactive intermediates furnished α-amidoketones 32 in excellent yields (Scheme 18). A diastereoselective [4 + 1] annulation of phthalaldehyde with imines leading to the formation of cis

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• have pointed to the possibility that inherent dynamical tendencies of reactive intermediates may play important roles in enzyme evolution. Here we review key studies on the dynamical behavior of carbocations. First we provide an introduction to dynamical behavior and how it is examined using modern

• reactive intermediates often meet this criterion and exhibit what are called “non-statistical dynamic effects”, that is, product distributions that cannot be rationalized by traditional TST [19][29][30]. These effects (highlighted through the examples discussed below) are typically described using

Copper-mediated synthesis of N-alkenyl-α,β-unsaturated nitrones and their conversion to tri- and tetrasubstituted pyridines

• Dimitra Kontokosta,
• Daniel S. Mueller,
• Dong-Liang Mo,
• Wiktoria H. Pace,
• Rachel A. Simpson and
• Laura L. Anderson

Beilstein J. Org. Chem. 2015, 11, 2097–2104, doi:10.3762/bjoc.11.226

• hydroxylamines, as well as N-alkenyl and N-arylnitrones [1][2][3][4][5]. We have discovered that when this transformation is performed with oxime and hydroxamic acid substrates, these reactive intermediates can be accessed and subsequently rearrange to a variety of challenging organic fragments and heterocyclic

An unusually stable chlorophosphite: What makes BIFOP–Cl so robust against hydrolysis?

• Roberto Blanco Trillo,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2015, 11, 313–322, doi:10.3762/bjoc.11.36

• , in Pd catalysts. Keywords: chirality; hydrolysis; phosphorus; rearrangements; terpenoids; Introduction Phosphorus halides are highly reactive intermediates for the synthesis of phosphites and phosphoramidites [1][2][3][4][5], which are widely used, for example, as ligands in catalysts [6][7][8][9

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• of the generated reactive intermediates and assist in the formation of the desired products. Tin, silicon or sulfur-based electroauxiliaries have proved useful in this endeavour. Yoshida and co-workers developed an organothio electroauxiliary that is selectively cleaved under anodic oxidation

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

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

• substrate is electrochemically inactive. In many cases, undesired side-reactions can be avoided by using redox mediators, since reactive intermediates do not accumulate on the electrode surface. Moreover, the indirect approach is often used in order to inhibit electrode passivation caused by formation of

• nucleophilic trapping of anodically formed iminium (23) or alkoxycarbenium species (24). The reactive intermediates can be generated directly from ethers or carboxylic acid amides (Scheme 9) [32]. However, aliphatic ethers and amides generally exhibit high oxidation potentials, and a large number of functional