Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• auxiliary in the esters is not yet resolved. Without a coacid succinic acid derivatives 26a/b/c–29a/b/c were obtained by dimerization of the half-ester radicals with yields of up to 50% and a facial diastereoselectivity of up to 87.5:12.5. Products that are similar to these of the anodic coupling can be

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• -dodecenolides, 12-tridecenolides and isomerized 13-tetradecenolides were obtained. In addition, ring expanded 14-pentadecenolides were observed. The latter can be explained by dimerization of esters 9 or 17, isomerization of the double bond, and final ring closure, leading to either ring-contracted or expanded

A new protocol for the synthesis of 4,7,12,15-tetrachloro[2.2]paracyclophane

• Donghui Pan,
• Yanbin Wang and
• Guomin Xiao

Beilstein J. Org. Chem. 2016, 12, 2443–2449, doi:10.3762/bjoc.12.237

• precursor of parylene D, from 2,5-dichloro-p-xylene. In the first bromination step, with H2O2–HBr as a bromide source, this procedure becomes organic-waste-free and organic-solvent-free and can appropriately replace the existing bromination methods. The Winberg elimination–dimerization step, using aqueous

• sodium hydroxide solution instead of silver oxide for anion exchange, results in a significant improvement in product yield. Furthermore, four substituted [2.2]paracyclophanes were also prepared in this convenient way. Keywords: bromination; dimerization; H2O2–HBr system; paracyclophane; polymerization

• prepare tetrachloroparacyclophane, but a pure polysubstituted product is difficult to obtain by electrophilic substitution without repeated crystallization or chromatographic purification [9]. Thus, we report an improved synthesis method using the Winberg dimerization of 2,5-dichloro-(4-methylbenzyl

Combined experimental and theoretical studies of regio- and stereoselectivity in reactions of β-isoxazolyl- and β-imidazolyl enamines with nitrile oxides

• Ilya V. Efimov,
• Marsel Z. Shafikov,
• Nikolai A. Beliaev,
• Natalia N. Volkova,
• Tetyana V. Beryozkina,
• Wim Dehaen,
• Zhijin Fan,
• Viktoria V. Grishko,
• Gert Lubec,
• Pavel A. Slepukhin and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2016, 12, 2390–2401, doi:10.3762/bjoc.12.233

• protons of the vinyl fragment in the 1H NMR spectra. Hydroxamoyl chlorides are known as masked nitrile oxides and the latter could easily be generated by reaction of the former with a base [31][32][33]. Nitrile oxides, apart from the expected cycloaddition reaction, could undergo dimerization affording

Synthesis of medronic acid monoesters and their purification by high-performance countercurrent chromatography or by hydroxyapatite

• Elina Puljula,
• Jouko Vepsäläinen and
• Petri A. Turhanen

Beilstein J. Org. Chem. 2016, 12, 2145–2149, doi:10.3762/bjoc.12.204

• unreported problem in the chlorination reaction of trimethyl methylene-BP with oxalyl chloride, i.e., we observed that the triester readily formed a dimer with itself during the chlorination reaction according to the 1H and 31P NMR spectra. Dimerization has been previously observed with clodronic acid

• trimethyl ester but not with medronic acid trimethyl ester [34]. In our case the dimerization led to low and unpredictable yields and therefore it was decided to develop an alternative method for the synthesis of mixed tetraesters. Here we describe a convenient method with good yields for the synthesis of

Thiophene-forming one-pot synthesis of three thienyl-bridged oligophenothiazines and their electronic properties

• Dominik Urselmann,
• Konstantin Deilhof,
• Bernhard Mayer and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2016, 12, 2055–2064, doi:10.3762/bjoc.12.194

• by a Sonogashira–Glaser sequence [74] also for probing delicate oxidative dimerization conditions with easily oxidizable phenothiazinyl moieties. According to our recent study on the formation of butadiynyl-bridged diphenothiazines [54] we were optimistic to probe this unusual approach. First, three

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

On the cause of low thermal stability of ethyl halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

• bimolecular dimerization leading to azines; and 3) a reaction of the diazo compound with the solvent or a reactant prior to nitrogen extrusion. The fact that the decomposition rate of all halodiazoacetates showed first order kinetics and that t1/2 for 2b is independent of its concentration indicates that

Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides

• Grzegorz Mlostoń,
• Róża Hamera-Fałdyga,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 1421–1427, doi:10.3762/bjoc.12.136

• [3 + 2]-cycloadditions. The high reactivity of ferrocenyl thioketones is demonstrated by the fact that no products of competitive reactions, such as dimerization of the intermediate 1,3-dipole or 1,3-dipolar electrocyclizations, were observed. Based on these observations one can expect that

Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

• Stefan Mark,
• Hubert Wadepohl and
• Markus Enders

Beilstein J. Org. Chem. 2016, 12, 1372–1379, doi:10.3762/bjoc.12.131

• ] and 2.3 Å–2.4 Å (Cr0) [70][71], respectively. As an alternative to the intramolecular coordination of the hemilabile donor to the vacant coordination site at the chromium center, a dimerization of the cationic methylchromium fragment could occur and examples of such dicationic dimers have been

• reported [72][73][74][75]. We were able to identify local minimum structures of dimers of compounds 3a+–8a+ but the calculated energies lie considerably higher compared to monomeric forms. Consequently, the saturation by the weak hemilabile donor is energetically preferred over dimerization. Another

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• could not isolate products due to decomposition under optimized IDC conditions. It was noticed that changing the solvent to THF effected very fast (within 5 minutes) dimerization of 3a and b at room temperature to afford 18a and b as sole products in 91–93% yield and in up to >20:1 dr (Scheme 4). This

• ], sharing a vicinal all-carbon quaternary stereogenic centers with extreme steric congestion at the C3a–C3a' σ-bond as well as the attendant lability of this linkage. Under the optimized conditions, one-pot dimerization of β-N-arylamido ester 3a and b and 9a took place in the presence of 1.2 equivalents of

• synthesis of 12b as per method A has been reproduced from reference [46]. Synthesis of spirocyclic product through IDC The synthesis of 14 as per method A has been reproduced from reference [46]. Conditions A: KOt-Bu, iodine; conditions B: KOt-Bu, NIS. Dimerization of β-N-aryl-amidoesters 3a and b

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• sterically hindered catalyst such as Rh2(esp)2 or Rh2(OPiv)4 is needed to prevent dimerization of the diazoacetate. These catalysts are presumed to protect the carbene intermediates from intermolecular reactions long enough to adopt the correct conformation for bridged-ring formation. An exploration of the

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• increase of the enantioselectivity. TCE heteroaryldiazoacetates were also successfully employed for the formation of the rhodium carbenoid insertion products in superior yields when compared to the reaction with methyl aryldiazoacetates. TCE aryldiazoacetates reduced significantly the carbene dimerization

Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes

• Grzegorz Mlostoń,
• Paulina Pipiak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 716–724, doi:10.3762/bjoc.12.71

• . Remarkably, in no single case, the ‘head-to-head dimerization’ of aryl/hetaryl and dihetaryl substituted thiocarbonyl ylides was observed. Keywords: [3 + 2]-cycloadditions; diazoalkanes; diradicals; 1,3-dithiolanes; reaction mechanisms; thioketones; Introduction Cycloaddition reactions belong to the most

• ). When the decomposition of 2a or 2b was performed in the presence of a suitable dipolarophile, the corresponding [3 + 2]-cycloadducts were formed, whereas in the absence of a dipolarophile, the ‘head-to-head dimerization’ leading to 2,2,3,3-tetraaryl-1,4-dithianes 4a,b is the exclusive reaction

• total, equimolar amount of 7c. After warming up and typical work-up procedure, the corresponding 1,3-dithiolane 10o and 1,4-dithiane 4c in a ratio of 2:1 were found as products identified in the 1H NMR spectrum of the crude reaction mixture. Thus, in this reaction dimerization of the intermediate

Opportunities and challenges for direct C–H functionalization of piperazines

• Zhishi Ye,
• Kristen E. Gettys and
• Mingji Dai

Beilstein J. Org. Chem. 2016, 12, 702–715, doi:10.3762/bjoc.12.70

• carbon-substituted piperazines [19][20][21][22]. Mendoza et al. have developed a [3 + 3] dimerization of azomethine to synthesize highly substituted piperazines [23]. Notably, Stoltz and co-workers recently developed an enantioselective synthesis of piperazin-2-ones and piperazines using a palladium

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

• group at the time had worked with cavitands. In fact, John was – to cut a long story short – instrumental to Don’s publications on the synthesis and properties of soluble carceplexes formed by the dimerization and covalent linking of tetrol-cavitands (Scheme 4). When I first arrived on the scene one of

• hydrophilic portal region, then dimerization of the host will not occur. For example the binding of charged amphiphiles such as n-octanoate lead to 1:1 complexes [33][34]. With these two points noted, a wide range of guests trigger dimerization to form the capsule with ostensibly sixteen negative charges on

• sterically hinder dimerization interfere less with an assembly as the angle between the two interfacing surfaces of a pair of cavitands increases from 0° (in a dimer) to ~70.5° (in a regular tetrahedron). This senary assembly many be higher in free energy, but because this container has a volume of four

Nucleic acids through condensation of nucleosides and phosphorous acid in the presence of sulfur

• Tuomas Lönnberg

Beilstein J. Org. Chem. 2016, 12, 670–673, doi:10.3762/bjoc.12.67

• buffer (pH 7.0). The tall peak eluting at 1.5 min in chromatogram C corresponds to either the enzyme itself or an impurity in the commercial preparation. Phosphitylation and subsequent dimerization of thymidine. Supporting Information Supporting Information File 54: Experimental methods, HPLC

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• bound substrate (Figure 25). Indeed, the exchange of this glutamate against an alanine residue resulted in an inactive version of the protein. Further an arginine residue, which could be involved in dimerization, was mutated to an aspartate. Also this mutant lost its catalytic activity, indicating that

• dimerization is essential [63]. The pseudopyronine synthase PyrS represents a homologue of PpyS. Using PpyS from Pseudomonas sp. GM30, it was analyzed if this KS is also involved in the formation of α-pyrones. The two pseudopyronines A (55) and B (56) have been up to now isolated from different Pseudomonas

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

• -derived NHCs have found widespread application as catalysts for benzoin reactions, whereas triazolium-derived NHCs have emerged as popular catalysts for enantioselective benzoin transformations. Review Homo-benzoin reactions The homo-benzoin condensation constitutes an overall catalytic dimerization of an

• –Michael cascade. Divergent catalytic dimerization of 2-formylcinnamates. One-pot, multicatalytic asymmetric synthesis of tetrahydrocarbazole derivatives. NHC-chiral secondary amine co-catalysis for the synthesis of complex spirocyclic scaffolds.

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• were reported many years ago. Were the water-soluble tweezers we set out to prepare in 1985 ever made? Where does the field stand today? We found that our molecular tweezers are well preorganized for dimerization, limiting their use in water [22], whereas Klärner and colleagues discovered that their

Comparison of the catalytic activity for the Suzuki–Miyaura reaction of (η⁵-Cp)Pd(IPr)Cl with (η³-cinnamyl)Pd(IPr)(Cl) and (η³-1-t-Bu-indenyl)Pd(IPr)(Cl)

• Patrick R. Melvin,
• Nilay Hazari,
• Hannah M. C. Lant,
• Ian L. Peczak and
• Hemali P. Shah

Beilstein J. Org. Chem. 2015, 11, 2476–2486, doi:10.3762/bjoc.11.269

• the form of a Pd(I) dimer [13]. This suggests that Cp is more likely to undergo dimerization than Cin. CpDim was confirmed to be a poor catalyst under the conditions employed in Figure 2 (Scheme 5). This result is indicative of CpDim as an off-cycle deactivation product, which reduces the amount of

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• , the addition of amino additives such as pyridine, morpholine, Et3N or DBU was shown to be detrimental to the G-HII-catalyzed dimerization of styrene (Table 2). Moderate to poor yields in stilbene 7’ were obtained and the value of the yields was correlated with the pKa of the couple ammonium/amine. An

• recommended to avoid dimerization. The most studied strategy allowing the use of olefins bearing N-heteroaromatics is the formation of the N-heteroaromatic salt prior to metathesis. The salt can be either isolated before metathesis or formed in situ using acidic additives. Alternatively, introduction of bulky

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• -functionalized arene dimerization [37]. Besides the issue of selectivity, another major challenge in the DG-assisted C–H activation lied in the removal of the DG, which undermined the efficiency of the synthetic procedure. To alternate the hardly removable DG of the pyridine ring, Carretero and co-workers [38

• related C–H transformation by providing key haloarene intermediates. For examples, in the CuI-catalyzed cross arene dimerization reactions reported by Daugulis et al., the in situ formation of iodoarene intermediate was discovered as the indispensable step during the generation of the biaryl products [65

Conformational equilibrium in supramolecular chemistry: Dibutyltriuret case

• Karina Mroczyńska,
• Małgorzata Kaczorowska,
• Erkki Kolehmainen,
• Ireneusz Grubecki,
• Marek Pietrzak and
• Borys Ośmiałowski

Beilstein J. Org. Chem. 2015, 11, 2105–2116, doi:10.3762/bjoc.11.227

• . Mass spectrometry analysis was performed on a Q-Exactive mass spectrometer (Thermo Scientific). The Benesi–Hildebrand equation [59] was used to find association constants while the method proposed by Tan [60] was used for dimerization of 1. It was assumed that 1:1 stoichiometry is present in all

Supramolecular chemistry: from aromatic foldamers to solution-phase supramolecular organic frameworks

• Zhan-Ting Li

Beilstein J. Org. Chem. 2015, 11, 2057–2071, doi:10.3762/bjoc.11.222

• secondary structures from aromatic backbones driven by different noncovalent forces (including hydrogen bonding, donor–acceptor, solvophobicity, and dimerization of conjugated radical cations) and solution-phase supramolecular organic frameworks driven by hydrophobically initiated aromatic stacking in the

• cavity of cucurbit[8]uril (CB[8]) are highlighted. Keywords: donor–acceptor interaction; foldamer; hydrogen bond; radical cation dimerization; supramolecular organic framework; Review Childhood and growing up I was born on July 23rd, 1966 in the small, remote village of Fang-Liu (a combination of two

• . In 1998, the group reported the extremely stable quadruple hydrogen-bonded dimers 8·8 [16] (Scheme 4). By using an 1H NMR dilution technique, a lower limit to the dimerization constant Kdim (>107 M−1) was estimated. Professor Zimmerman hoped to make an accurate determination of the binding stability