Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• dimerized 16-membered ring product 101 in 57% yield, which was generated by a RRM–dimerization sequence and its monomer 100 in 14% yield along with 99 in 26% yield (Scheme 20). Bicyclo[2.2.1]heptene derivatives Holtsclaw and Koreeda [25] have explored a chemoselective RRM of the enone containing norbornene

Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

• Andrzej Tracz,
• Mateusz Matczak,
• Katarzyna Urbaniak and
• Krzysztof Skowerski

Beilstein J. Org. Chem. 2015, 11, 1823–1832, doi:10.3762/bjoc.11.198

• worse than nG-SIPr. As outlined in Table 2, all tested catalysts were similarly effective in CM of methyl undecenoate 12 with cis-1,4-diacetoxy-2-butene (13), but parent dichloro complexes provided smaller quantities of dimerization product of 12. In CM of 12 with electron deficient methyl acrylate 15

SmI₂-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B

• Nils Marsch,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2015, 11, 1700–1706, doi:10.3762/bjoc.11.184

• -configuration were formed by SmI2-mediated reductive dimerization of a 4-(indol-6-yl)butenone, obtained by Heck reaction. The two indolyl units appear to chelate Sm(II)/(III) leading to a gauche-type arrangement at the newly formed bond between the two β-carbons. Through a sequence of Sonogashira cross coupling

• plants [1][2][3] and also in fungi [4] and myxobacteria [5][6]. One example is raputindole A (1), isolated in 2010 from the Rutaceous tree Raputia simulans Kallunki [1], which exhibits a unique tetrahydrocyclopenta[f]indole partial structure (Figure 1) probably formed by dimerization of (E)-6-(3

• their reductive dimerization. We also describe the synthesis of the antimicrobial natural product indiacen B (2) from the myxobacterium Sandaracinus amylolyticus [5], bearing a unique isoprene moiety chlorinated at the methylene group. Results and Discussion SmI2-induced reductive dimerizations 6

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• showed two reversible two-electron redox waves at −0.03 and 0.38 V vs Fc/Fc+ in benzonitrile under normal conditions [25][60]. Conducting nanostructure formation from star-shaped oligo-TTFs Although pristine TTF does not self-associate in solution due to the low association constant for dimerization, the

• tris(TTF)[18]annulene 32. Star-shaped TTF oligomers 38–43. Pyridazine-3,6-diol-TTF 45 and its trimer 46. Redox potentials of 16–19 and absorption maxima of monocations 16•+, 17•+, 18•+ and 19•+, and dications 162+, 172+, 182+ and 192+ [25][59]. Association (dimerization) constants and thermodynamic

A novel and widespread class of ketosynthase is responsible for the head-to-head condensation of two acyl moieties in bacterial pyrone biosynthesis

• Darko Kresovic,
• Florence Schempp,
• Zakaria Cheikh-Ali and
• Helge B. Bode

Beilstein J. Org. Chem. 2015, 11, 1412–1417, doi:10.3762/bjoc.11.152

• in the total loss of photopyrone production (Figures S1 and S2, Supporting Information File 1). Similarly, no photopyrone was produced in a R121D derivative. R121α is predicted by the model to be located at the dimer interface interacting with D137β. Thus, dimerization shown to be essential for KS

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

• was subjected to dimerization involving cross-metathesis with G-I/G-II/Schrock catalysts which generated the cyclized product 154. Subsequently, hydrogenation of the cyclophane 154 followed by minor functional group modification gave the natural products 155 and 156 (Scheme 23). Furthermore, the same

• 171 via RCM/CM using G-I (12) or G-II (13) under high dilution conditions to obtain the [n], [n,n] and [n,n,n]paracyclophanes 172–174. Compounds with a short alkenyl chain gave mainly [n,n] and [n,n,n]paracyclophanes (173 and 174) by a dimerization or trimerization sequence. When the compound has a

Cathodic hydrodimerization of nitroolefins

• Michael Weßling and
• Hans J. Schäfer

Beilstein J. Org. Chem. 2015, 11, 1163–1174, doi:10.3762/bjoc.11.131

• reduction of the nitro group to oximes would be favoured. On the other side the electrolyte should not be aprotic as protons are required for protonation of the intermediate anions in the reductive dimerization (Scheme 1). According to the proposed mechanism for the cathodic hydrodimerization the radical

• anion b formed by one electron reduction of the substrate a, has three pathways for dimerization [1][2]. In path (I) protonation followed by one-electron reduction leads to anion c, which in a Michael addition with substrate a forms the anion d, which is protonated to hydrodimer f. In path (II) b

• in [6][7][8]. There have been reports on the reductive dimerization of nitro alkenes prior to 1991. 1,4-Dinitro-2,3-diphenylbutane (3) has been obtained in less than 20% yield in the catalytic hydrogenation of β-nitrostyrene (4) [11]. Hydrodimerization of 4 was observed in enzymatic reduction [12

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• by an electrochemical simulation program (DigiElch 7) involving an electrochemical mechanism (Scheme 4) composed by three one-electron processes and two charge-coupled chemical reactions (i.e., formation of mixed-valence and dimerization via a square scheme). Due to the equivalence of the two TTF

• bulky groups at the periphery of the TTF moieties does not provide an advantage for the self-assembly of dimers. Moreover, this dimerization phenomenon which is driven by the inclusion of one sidewall into the cavity of the opposing clip is not observed in the solid state for clips 2 and 3 (Figure 8

Carboxylated dithiafulvenes and tetrathiafulvalene vinylogues: synthesis, electronic properties, and complexation with zinc ions

• Yunfei Wang and
• Yuming Zhao

Beilstein J. Org. Chem. 2015, 11, 957–965, doi:10.3762/bjoc.11.107

• oxidative dimerization reaction of corresponding dithiafulvene (DTF) precursors [27]. This straightforward C–C bond forming reaction has not only allowed TTFV derivatives with different substituents to be readily assembled, but served as an effective methodology to construct the π-conjugated frameworks of

• ]. This olefination reaction went completion within 3 hours to give DTF 4 in 77% yield after column separation. Compound 4 was then subjected to an oxidative dimerization in CH2Cl2 at room temperature using iodine as oxidant. The dimerization gave TTFV 5 as a stable yellow solid in 80% yield

• generated on the electrode surface via the DTF dimerization reaction [15][16]. In the following scan cycles, the redox wave pair characteristic of TTFV at Epa = +0.62 V and Epc = +0.54 V was found to gradually increase in intensity as a result of increasing electrochemical dimerization. The same

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• generated for the dication of both of these compounds, which signals intramolecular interaction of the two polaronic TTF units as we exclude π-dimerization since the EPR inactivity did not depend on the concentration of the species. A non-negligible interaction between the polaronic states was observed for

Regulation of integrin and growth factor signaling in biomaterials for osteodifferentiation

• Qiang Wei,
• Theresa L. M. Pohl,
• Anja Seckinger,
• Joachim P. Spatz and
• Elisabetta A. Cavalcanti-Adam

Beilstein J. Org. Chem. 2015, 11, 773–783, doi:10.3762/bjoc.11.87

• , is highly conserved [50]. Six of the seven cysteine residues Cys14/Cys79, Cys47/Cys113, and Cys43/Cys111 form intramolecular disulfide bonds to stabilize the monomer, whereas the seventh cysteine (Cys78) contributes to the formation of an intermolecular bond between the two monomers for dimerization

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• glycothymine branches in 13 and 14 are sterically more hindered than the thymine branches in 7 and 8. Again UV–vis spectroscopy further underlines the dimerization success as the absorption maximum at 270 nm disappears and mass spectrometry supports intramolecular photocycloaddition only (cf. Supporting

Attempts to prepare an all-carbon indigoid system

• Şeref Yildizhan,
• Henning Hopf and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 363–372, doi:10.3762/bjoc.11.42

• ). To rationalize its formation we propose that the deoxygenation of 13 does indeed take place, but provides a carbenoid intermediate 15 rather than the vicinal diol complex that is usually postulated to be formed during the McMurry dimerization. Possibly the dimerization of the substrate molecule

• interactions. Our next approach towards 4 (or a derivative) started from indan-1-one (18, Scheme 4). Enolization of 18 was carried out with sodium hydride in THF and on subsequent oxidative dimerization the expected bis-ketone 19 was obtained. This compound is produced as a mixture of two diastereomers in

• component for this type of condensation would be the tetra-substituted olefin 2-(2-indanylidene)indane (30), in which each methylene group is activated both by a benzene ring and a double bond. We prepared this known olefin [28] by a McMurry-type dimerization of 2-indanone (9). The structure determination

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

• Taiki Kojima,
• Rika Obata,
• Tsuyoshi Saito,
• Yasuaki Einaga and
• Shigeru Nishiyama

Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21

• . As shown in Figure 1, the radical intermediate derived from phenylacrylate through a one-electron reduction (right) differs from that obtained by anodic oxidation of 4-hydroxyphenyl-1-propene (left). Therefore, the reductive dimerization of cinnamic acid derivatives was expected to provide access to

• effect of MeCN was observed for this dimerization reaction, while stereoselectivity was unaffected among the conditions tested and the racemic form was predominant over the meso form in all cases. Electrochemically prepared (±)-2 was further converted into E-5 and E-8 as novel unprecedented neolignan

Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions

• Almaz Zagidullin,
• Vasili Miluykov,
• Elena Oshchepkova,
• Artem Tufatullin,
• Olga Kataeva and
• Oleg Sinyashin

Beilstein J. Org. Chem. 2015, 11, 169–173, doi:10.3762/bjoc.11.17

• dimerization was observed only upon heating to 190 °C leading to the product of the [2 + 2] cycloaddition reaction [9]. At the same time, 3,4,5-tri(p-fluorophenyl)-1-ethyl-1,2-diphosphole (1e) is stable at room temperature and undergoes the [4 + 2] cycloaddition reaction only upon heating at 60 °C resulting in

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• bpz have been reported [26][27][28], the most common of which involve transition metal-catalyzed reductive homocouplings of halopyrazine electrophiles [29][30]. However, we found these procedures to be capricious in our hands, and after a survey of known reductive dimerization protocols, the highest

Synthesis of antibacterial 1,3-diyne-linked peptoids from an Ugi-4CR/Glaser coupling approach

• Martin C. N. Brauer,
• Ricardo A. W. Neves Filho,
• Bernhard Westermann,
• Ramona Heinke and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2015, 11, 25–30, doi:10.3762/bjoc.11.4

• ; Introduction A re-occurring principle of nature to mediate or increase biological activity is dimerization [1]. Many protein receptors dimerize upon activation and recruit their active form by this transformation. This process is mainly initiated by dimeric natural products or symmetric bivalent ligands, which

• another study Chen and co-workers found a GLP-1R antagonist only because of an unexpected dimerization [5]; and a dimer of S-adenosylmethionine is up to 13-fold more active than the monomer for promoting the binding of Escherichia coli methionine repressor to its operator DNA [6]. Peptoids are compounds

A facile synthesis of functionalized 7,8-diaza[5]helicenes through an oxidative ring-closure of 1,1’-binaphthalene-2,2’-diamines (BINAMs)

• Youhei Takeda,
• Masato Okazaki,
• Yoshiaki Maruoka and
• Satoshi Minakata

Beilstein J. Org. Chem. 2015, 11, 9–15, doi:10.3762/bjoc.11.2

• iodine-containing reagent t-BuOI, which is readily generated in situ from t-BuOCl and NaI, serves as a powerful oxidant for homo- and cross-dimerization of aromatic amines leading to aromatic azo compounds [27][28][30]. However, the employment of t-BuOI as an oxidant for this intramolecular oxidative N=N

Synthesis of an organic-soluble π-conjugated [3]rotaxane via rotation of glucopyranose units in permethylated β-cyclodextrin

• Jun Terao,
• Yohei Konoshima,
• Akitoshi Matono,
• Hiroshi Masai,
• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2014, 10, 2800–2808, doi:10.3762/bjoc.10.297

• β-CD 14. After the deprotection of the triisopropyl group of 14 and the Glaser dimerization reaction of 15, symmetrical oligothiophene 16 bearing two PM β-CDs was obtained. Treatment of 16 with Na2S and KOH followed by dibromination by N-bromosuccinimide formed dibromo-heptathiophene 17 with two

Microsolvation and sp²-stereoinversion of monomeric α-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR

• Rudolf Knorr,
• Monika Knittl and
• Eva C. Rossmann

Beilstein J. Org. Chem. 2014, 10, 2521–2530, doi:10.3762/bjoc.10.263

• . However, our sterically congested model system [9] 1 exhibited separate resonances of the latter three donor ligands (“Don” in Scheme 1) above the melting points of the solvent mixtures, so that the microsolvation numbers d could be measured by simple NMR integrations. On this basis, dimerization

• agreement with the corresponding effects of dimerization that were reported [22] for 1a in toluene. A 1H NMR spectrum taken at −55 °C revealed a substantially decreased magnitude of 2JH,H = ca. 3.7 Hz. The lack of further 2JH,H data in Table S9 [15] was due to strong line broadening in the presence of

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• CO2 dimerization product [50]. Additional insight in the carboxylation mechanism was gained by comparing the reactivity of 1,3-cyclohexadiene with a mixture of 2,4-hexadiene isomers. The fixed cyclic conformation of 1,3-cyclohexadiene increases its reactivity towards CO2 fixation, explained by a

• . The presence of protons drastically increases the amount of dimerization product and favors the hydrogenation of the carbonyl group to the alcohol [75][76][82][91]. The cathode material again plays an important role in the electrocarboxylation of carbonyl compounds. Toxic lead cathodes [85] and

• methoxymethane-1,1,1’-tricarboxylate precursors. R1: ethoxycarbonyl [151]. Electrochemical dimerization of CO2 with stable electrodes [153]. Electrocarboxylation of 1,3-butadiene in different setups.a Acknowledgements This research is funded by the Industrieel Onderzoeksfonds KU Leuven (project IKP/10/005). We

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives

• Marijana Radić Stojković,
• Marko Škugor,
• Łukasz Dudek,
• Jarosław Grolik,
• Julita Eilmes and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225

• spectrum for ds-RNA (poly rA–poly rU) and ICD at low ratios[compd]/[DNA] (0.1; 0.2), which is attributed to DP77–DBTAA intercalation. Under the same conditions the ICD bands of AP3/AP3am exhibit a significant intensity only at r > 0.3, which strongly corroborates the hypothesis of the dimerization of the

Building complex carbon skeletons with ethynyl[2.2]paracyclophanes

• Ina Dix,
• Lidija Bondarenko,
• Peter G. Jones,
• Thomas Oeser and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 2013–2020, doi:10.3762/bjoc.10.209

• The oxidative dimerization (Glaser coupling) of the achiral hydrocarbon 2 took place effortlessly and in high yield (Scheme 3). However, we have been unable so far to determine the exact structure of the isolated dimer. As shown in Scheme 3, in principle, two different dimers of 2 could be formed: one

• structural information. Our proposal of two types of dimers results, firstly, from the spectra of the dimers generated by Glaser coupling of 4-ethynyl[2.2]paracyclophane and secondly, from the dimerization results with the pseudo-ortho compound 4 described below. NMR analysis proved unambiguously that two

• diastereomers are generated (as expected) by the oxidative dimerization of the mono ethynyl derivative [9], but assignment of the various spectra to specific stereoisomers remains an open question, and will only be possible after the resolution of the 4-ethynyl[2.2]paracyclophane, determination of its absolute

A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H)-furanones

• Jubi John,
• Eliza Târcoveanu,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 1462–1470, doi:10.3762/bjoc.10.150

• not detect the formation of diene-2,5-dicarboxylate 4 (formed by the dimerization of 2a) as a side product, although this was observed previously in the reaction of activated alkenes [40] and 4-chloroacetoacetates. Table 1 summarizes our efforts towards optimizing various reaction parameters with 1a

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• under lower concentration of the acceptor ketone and the probability of hydroxybenzyl radical dimerization (i.e., route II) is disfavoured under these conditions. Photohydroxymethylation of carbonyl compounds and imines. Model process: photocatalyzed acetophenone/methanol reaction. Photocatalyzed