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

• nucleophilic 1,2-migration of aryl (Ph) or alkyl (Me) group R2 occurs, producing α-oxoketene D. The latter interacts with N–H-group of the aminoester 1 to give acylamides 6a–c. Predominance of the Wolff rearrangement over typical carbenoid reactions (N–H-insertion, etc.) in the case of diazodicarbonyl

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

• summarize systematically related and different features of these reactions, compares their mechanisms, and assesses the prospects of their application. By definition, a rearrangement is a migration of an atom or a group of atoms from one atom to another within the same molecule [189]. In contrast, a

• as rearrangements of peroxides can give both isomeric and non-isomeric compounds either containing a peroxy group or without the latter. In most cases, a rearrangement involves the migration or cleavage of the peroxide group in an intermediate molecule, and the stability of the latter is responsible

• binds to the carbonyl group of ketone 1 to form the tetrahedral intermediate 3 which is referred to as the Criegee intermediate. The next step involves the concerted migration of the R2 group to the peroxide oxygen atom, resulting in the formation of ester 4 and carboxylic acid 5 (Scheme 2). The ability

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• ; density functional theory (DFT); hapototropic rearrangements; HOMO–LUMO interactions; polyene-ML2 complexes; ring-whizzing; Introduction Polyene–transition metal complexes were found to undergo fluxional rearrangements as early as 1956 with the preparation of Cp2Fe(CO)2 [1]. The migration of an MLn unit

• thought [20] that migration of an ML2 unit from one ring to another would involve an η3 structure where Pt would bond to C(1), C(9) and C(8). For the carbon numbering system please see 48. Bonding between b2 ML2 and the b1g MO would be retained. Unfortunately this is not quite the entire story. One of the

Application of Cu(I)-catalyzed azide–alkyne cycloaddition for the design and synthesis of sequence specific probes targeting double-stranded DNA

• Svetlana V. Vasilyeva,
• Vyacheslav V. Filichev and
• Alexandre S. Boutorine

Beilstein J. Org. Chem. 2016, 12, 1348–1360, doi:10.3762/bjoc.12.128

• ) with barely visible traces of mono-polyamide conjugate (line 6, e). Lines 5d and 6d are visible by UV-shadowing bands of electrophoresis migration marker xylene cyanol that is absent in other gels. Mass-spectrometry analysis confirmed the identity of the products obtained (Table S3 in Supporting

• arrows indicate positions: a and c – initial alkyne-modified oligonucleotides, b and e – 1:1 conjugates TFO:polyamide, f – 1:2 conjugate TFO-polyamide, d – visible migration marker xylene cyanol. Electrophoresis analysis of reaction mixtures in 20% denaturing polyacrylamide gel after TINA-TFO-MGB

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• -ylidene)(pentacarbonyl) W(CO)5(12) (Scheme 1f) [53]. In principle, the formation of imines from NH carbene complexes can occur by three conceivable fundamental pathways. The first pathway starts with the dissociation of the carbene followed by a 1,2-H shift at the free carbene (elimination–migration). The

• second one operates via a hydrogen atom shift at the coordinated carbene followed by dissociation of the resulting imine (migration–elimination). A third conceivable pathway could start with CO loss, followed by H atom migration. To the best of our knowledge, the mechanism of the imine formation from NH

• carbene complexes is not yet established. In the absence of a base, the bulky diferrocenylcarbene complex Cr(CO)5(E-2) is stable even in refluxing toluene and hence, a simple migration–elimination or elimination–migration reaction is not anticipated in this case. We report here the heavier tungsten

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• [2,3,4-kl]acridines (the core structure of plakinidine C) from enaminones and 3-indolyl-3-hydroxyoxindoles through a cascade ring-opening/recyclization/methyl migration sequence (Scheme 61) [78]. The reactions proceeded well in MeCN in the presence of catalytic I2 (30 mol %) under an O2 atmosphere

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

• Štěpán Horník,
• Lucie Červenková Šťastná,
• Petra Cuřínová,
• Jan Sýkora,
• Kateřina Káňová,
• Roman Hrstka,
• Ivana Císařová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

• ]. The resulting disruption of protein–(glycosamino)glycan interactions had important biomedical consequences such as reduced selectin-mediated tumor cell adhesion [12][13], suppressed selectin-mediated leukocyte migration [11][14][15], reduced angiogenesis [3], or inhibition of tumor growth by decreased

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

• M. Fernanda N. N. Carvalho,
• M. João Ferreira,
• Ana S. O. Knittel,
• Maria da Conceição Oliveira,
• João Costa Pessoa,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

• may expect such a barrier in the tautomerization (probably catalyzed by water) which forms the zwitterion by proton migration from the neutral imine. The experimental results on Strecker degradation have been summarized in a rule that says that the most efficient promoters have a structure of the type

• ). We therefore expected that kinetic effects during the tautomerizations might be responsible for the observed selectivity and checked the interconversion pathways between the tautomers 7–11 which differ only in the position of one proton. Such a proton migration must of course be catalyzed, and water

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

• in bringing the issue of dynamic effects to a wide audience [46]. The question addressed in this work was ostensibly simple: is the mechanism of dehydration/alkyl migration of a protonated alcohol a concerted or stepwise process? The IRC for the process revealed a concerted mechanism (Figure 5, blue

• and co-workers [55]. Additionally, replacing R in Figure 5 with a non-methyl substituent opened up the possibility of the formation of two different products resulting from migration of different alkyl groups (tertiary carbocation products A and B in Figure 5). While these differences led to results

• preorganization of the substrate into a conformation that disfavors the 1,2-hydride shift actually promotes miltiradiene formation. Finally, when dynamics trajectories were initiated from the region of the 1,6-proton transfer transition state associated with proton migration to the si face of the C=C double bond

Art, auto-mechanics, and supramolecular chemistry. A merging of hobbies and career

• Eric V. Anslyn

Beilstein J. Org. Chem. 2016, 12, 362–376, doi:10.3762/bjoc.12.40

• medical school, research was one of my pursuits from freshman year throughout my undergraduate career. The project entailed the use of variable-temperature NMR to measure the dynamics of ligand migration in trimetallic osmium clusters [22][23]. Dr. Rosenberg was an inspirational figure, and his pursuit

Diastereoselective synthesis of new O-alkylated and C-branched inositols and their corresponding fluoro analogues

• Charlotte Collet,
• Françoise Chrétien,
• Yves Chapleur and
• Sandrine Lamandé-Langle

Beilstein J. Org. Chem. 2016, 12, 353–361, doi:10.3762/bjoc.12.39

• ]. The trityl group in myo-11 and scyllo-11 was cleaved without acetyl migration using FeCl3 [47] to afford myo-12 and scyllo-12 in good yields. The primary hydroxy groups can be easily converted into fluorine by action of DAST in dichloromethane in less than 5 minutes to give myo-13 and scyllo-13 in 95

• /or acetate migration. By reducing the reaction time to 15 minutes the byproducts formation could be lowered to 10% and myo-2 was obtained in 45% isolated yield. It is worthy to note that 41% of the starting material was recovered. At this stage, the fluorination was tested using DAST [48] on myo-20

• show any fluorine incorporation. Various types of compounds resulting from the migration of the tertiary acetate to the primary position, elimination reaction or cyclization were identified depending on the experimental procedure. From these results, the fluorination was finally investigated on myo-22

Mycothiol synthesis by an anomerization reaction through endocyclic cleavage

• Shino Manabe and
• Yukishige Ito

Beilstein J. Org. Chem. 2016, 12, 328–333, doi:10.3762/bjoc.12.35

• migration, as reported previously, gave mycothiol 1 [23][24]. Conclusion We demonstrated a MSH synthesis using an anomerization reaction through endocyclic cleavage in the presence of a weak Lewis acid. Murphy also reported the utility of the anomerization of glucuronic acid for preparing 1,2-cis-linked

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• [18][19], decarboxylative alkenylation of cycloalkanes with aryl vinylic carboxylic acids [20][21], trifluoromethylthiolation [22], thiolation [23][24], alkenylation [25][26], dehydrogenation−olefination and esterification [27][28], radical addition/1,2-aryl migration [29], cascade alkylation

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• promoting the migration of its acetalic H atom in a hydride-like manner. As result, we have disclosed a variety of tandem processes initiated by [1,5]- and [1,4]-hydride shifts from the acetalic carbon atom toward electrophilic molecular fragments [19][20][21][22][23][24][25][26][27]. Thus, we have reported

• products, it seems reasonable to hypothesize that the conversions 3 → 5 + 6 are initiated by an H migration from the acetalic carbon toward the fulvene substructure. If this migration is a [1,4]-hydride shift to the exocyclic C4 carbon atom of the fulvene fragment, as initially postulated, this step

• geometries of both transition structures TS1-A and TS1-B, more specifically to the distance between the two carbon atom termini of the H migration, shorter in TS1-B (2.63 Å) than in TS1-A (2.67 Å). Therefore, TS1-B is earlier than TS1-A. The geometry of TS1-B also accounts for its greater conjugation as the

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• ) polymerization [15][16], living ionic polymerizations, specifically ring-opening polymerization (ROP) [17], as well as migration insertion polymerization (MIP) [18], acyclic diene metathesis polymerization (ADMET) [19][20] and ring-opening metathesis polymerization (ROMP) [21][22][23][24][25][26][27]. These

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• GGPP cyclization to form the bicyclic cation 46, followed by a second cyclization and a 1,5-hydride shift to yield 47. This unusual hydride migration was experimentally supported by location of Hc at C-15 of 52. A 1,3-hydride shift generates the allylic cation 48, which can undergo another 1,5-hydride

• labeled product indicated a migration of the C-12 deuterium atoms to C-19 and to C-2, thus proving evidence for the proposed hydride migrations from 54 to 55 and from 57 to 58. The application of isotopes in mechanistic investigations is by far not limited to following atoms through the biosynthetic

• subsequent 1,2-hydride migration to 63 followed by ring closure gives 64, which is deprotonated to give pentalenene (65). Quantum chemical calculations led to the suggestion of the protoilludyl cation 66 as central intermediate between 61 and 64 (pathway B), which is directly formed from 61 [72

Total synthesis of panicein A₂

• Lili Yeung,
• Lisa I. Pilkington,
• Melissa M. Cadelis,
• Brent R. Copp and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 1991–1996, doi:10.3762/bjoc.11.215

• isolated from Reniera fulva and R. mucosa [2][3]. It has been postulated that the biosynthesis of paniceins centres around the cyclisation of a farnesyl precursor 6 [4] to an abscisane derivative 7 followed by a 1,2-methyl migration and subsequent oxidation to give panicein A (1) [1][3]. Subsequent

Cross metathesis of unsaturated epoxides for the synthesis of polyfunctional building blocks

• Meriem K. Abderrezak,
• Kristýna Šichová,
• Nancy Dominguez-Boblett,
• Antoine Dupé,
• Zahia Kabouche,
• Christian Bruneau and
• Cédric Fischmeister

Beilstein J. Org. Chem. 2015, 11, 1876–1880, doi:10.3762/bjoc.11.201

• phosphine could interact with the electron-deficient olefin leading to catalyst decomposition [31]. As observed by us and other groups in cross metathesis involving different substrates, double bond migration side-reactions took place during this transformation. This side reaction could be circumvented

• using benzoquinone [32] as an additive to decrease the extent of double-bond migration. As depicted in Table 1 (entries 1–4), 10 mol % of benzoquinone were necessary to ensure a limited amount (<10%) of side products resulting from double-bond migration. However, addition of benzoquinone resulted in

Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach

• Jingjing Wang,
• Samuel Z. Y. Ting and
• Joanne E. Harvey

Beilstein J. Org. Chem. 2015, 11, 1815–1822, doi:10.3762/bjoc.11.197

• was contaminated with further isomeric material. Careful analysis of the product mixtures led to the realisation that silyl migration from the primary to the secondary hydroxy group was occurring in the reaction, leading to the C20-linked ester isomer in addition to the desired C19 ester 11g. In

• -unsaturated ester 5a was formed as a mixture of diastereomers (Scheme 3), as expected, but was again contaminated with the regioisomer resulting from silyl migration (2:1 ratio 5a:isomeric C20 ester). Employing the PMB-protected C19 alcohols 7b [43][44][45] and 7c [43][44][45][49] led to the desired products

Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers

• Ivan Bassanini,
• Karl Hult and
• Sergio Riva

Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174

• respective two parent compounds. This is the so-called ‘dual drug’ strategy [37][38][39][40][41]. For instance [40][41], an increased capacity of inhibiting endothelial cell differentiation and migration (key steps of the angiogenic process) was observed as well as a marked ability to inhibit the

Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha,
• Ongolu Ravikumar and
• Jadab Majhi

Beilstein J. Org. Chem. 2015, 11, 1503–1508, doi:10.3762/bjoc.11.163

• amide in the presence of acid was discovered in 1886. This rearrangement involves the migration of a group anti to the leaving group on the nitrogen atom. The BR has widely been used in synthetic organic chemistry, for example, a large-scale production of Nylon-6 is based on the synthesis of ε

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Synthesis of icariin from kaempferol through regioselective methylation and para-Claisen–Cope rearrangement

• Qinggang Mei,
• Chun Wang,
• Zhigang Zhao,
• Weicheng Yuan and
• Guolin Zhang

Beilstein J. Org. Chem. 2015, 11, 1220–1225, doi:10.3762/bjoc.11.135

• unsatisfactory, even when prolonging the reaction time to 36 h or raising the temperature to 100 °C. By carefully investigating the two routes in Scheme 3, we assumed that an appropriate base is in favor of the [1,5]H σ migration in route 2, as well as lowering the acidity of Eu(fod)3 to prevent 12b from

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

• -aryl migration step. This was mediated by a hypervalent iodine reagent, PhI(OAc)2 (13), conducted in trimethyl orthoformate (14, TMOF) and methanol (Scheme 2). The direct saponification of the resulting rearranged methyl ester with an excess of base thus completed the telescoped flow synthesis of

• (Friedel–Crafts acylation, 1,2-aryl migration and saponification) this report focuses on improved output by intensifying the overall sequence (Scheme 3). As such an in-line extraction is performed after the Friedel–Crafts acylation step, followed by dissolving intermediate 18 in trimethyl orthoformate and

• DMF. This stream is then combined with a stream of ICl (21) to affect the 1,2-aryl migration in a heated flow reactor (1 min, 90 °C) followed by treatment of the stream with NaOH, 2-mercaptoethanol, MeOH and water in order to hydrolyse the intermediate methyl ester and quench residual ICl. After

DBU-promoted carboxylative cyclization of o-hydroxy- and o-acetamidoacetophenone

• Wen-Zhen Zhang,
• Si Liu and
• Xiao-Bing Lu

Beilstein J. Org. Chem. 2015, 11, 906–912, doi:10.3762/bjoc.11.102

• -diazabicycloundec-7-ene (DBU) is reported. This reaction provides convenient access to the biologically important compounds 4-hydroxy-2H-chromen-2-one and 4-hydroxy-2(1H)-quinolinone in moderate to good yields using carbon dioxide as the carboxylation reagent. An acyl migration from nitrogen to carbon is observed

• in the reaction of o-acetamidoacetophenone. Keywords: acyl migration; carbon dioxide; carboxylation; cyclization; condensation; Introduction 4-Hydroxy-2H-chromen-2-ones and 4-hydroxy-2(1H)-quinolinones are key structural subunits found in many natural products [1], commercial drugs [2][3] and

• cyclization of o-hydroxy- and o-acetamidoacetophenones with carbon dioxide to give 4-hydroxy-2H-chromen-2-ones and 4-hydroxy-2(1H)-quinolinones, respectively, in moderate to good yields under mild reaction conditions. An acyl migration from the nitrogen to carbon is observed in the reaction of o