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

• -methylmenthol- (2)-, 8-phenylmenthol- (3)-, and 8-p-anisylmenthol- (4)-2-alkylmalonates (Figure 1). Results and Discussion Anodic hetero- and homo-coupling of carboxylates The carboxylic acids 13a/b–18a/b for the Kolbe electrolyses were synthesized according to Scheme 1. The chiral auxiliary 1–4 is acylated

• purity (Scheme 1). Anodic hetero-coupling of carboxylates Carboxylates of aliphatic carboxylic acids are oxidized to carbonyloxy radicals at a platinum electrode at potentials being generally higher than 2.0 V (vs NHE). The carbonyloxy radicals undergo fast decarboxylation to alkyl radicals at or near

• the case for 18a/b. Even in the case of 16a/b and 17a/b a significant portion of polar products is found, indicating a partial oxidation of the phenyl group. Anodic homo-coupling of carboxylates The carboxylic acids 13a/b–16a/b have also been subjected to homo-coupling and the diastereomers 26a/b/c

Et₃B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

• Ahlem Abidi,
• Yosra Oueslati and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

• Tsuji–Trost reaction involving, as substrates, allyl carboxylates [2], carbonates [3], and phosphates [4]. Obviously, the direct nucleophilic allylic substitution of allyl alcohols is a more attractive process especially from an economical and environmental point of view [5], as water, generated by this

• of the MBH carboxylates with aliphatic 1,3-diketones in the presence of K2CO3. A drawback of these synthetic approaches is the need to first perform the acylation step of the corresponding allyl MBH alcohols. For this reason, we herein report an efficient direct method for the allylation of β

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

• catalyst and its ligands on the efficiency of the processes studied, non-fluorinated rhodium carboxylates (Rh2L4; L = OAc, Oct, Piv) and catalysts with trifluoroacetate or perfluorobutyrate ligands [Rh2L4; L = CF3CO2 (tfa), C3F7CO2 (pfb)] were used in this research. Results and Discussion In the beginning

• case of the amide 6c [16]. The yield of acetamide 7 was heavily dependent on the Rh(II)-catаlyst ligand nature, attaining the highest values of 46–50% when dirhodium carboxylates with perfluorinated ligands were used (Table 2, entries 7–9). Most clearly this tendency is evident when comparing the

• compounds 3а–с can be apparently explained by some sterical reasons and, first of all, by the problems associated with the approach of the N–H-group of the bulky secondary amine 1 to the electrophilic carbon atom of H-Rh-carbenoid C (Scheme 2). Carbenoids from perfluorinated carboxylates F-Rh(II) are

Potent triazine-based dehydrocondensing reagents substituted by an amido group

• Munetaka Kunishima,
• Daiki Kato,
• Nobu Kimura,
• Masanori Kitamura,
• Kohei Yamada and
• Kazuhito Hioki

Beilstein J. Org. Chem. 2016, 12, 1897–1903, doi:10.3762/bjoc.12.179

• (NMM). Related triazinylammonium salts (DMT-Am) can be prepared from other tertiary amines 5 instead of NMM (Scheme 1c) [6]. Since the direct reaction of carboxylates with CDMT is very slow, the formation of DMT-Am is essential for the conversion of carboxylates into 4 [7]. Therefore, we developed

Organic chemistry meets polymers, nanoscience, therapeutics and diagnostics

• Vincent M. Rotello

Beilstein J. Org. Chem. 2016, 12, 1638–1646, doi:10.3762/bjoc.12.161

• (including us) could generate emulsions with diameters small enough (<200 nm) for use as in vivo delivery vehicles [60]. Once again, supramolecular chemistry came to the rescue. Anslyn showed that guanidinium groups bound strongly to carboxylates [61]. This led to the surmise that this interaction could be

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

• halodiazoacetates are also much less stable than EDA in the presence of a weak acid such as acetic acid and dramatically more sensitive towards transition metal salts such as Cu(OTf)2 and Rh2(II) carboxylates. Calculations predict the diazo carbons in the halodiazoacetates to have a much less nucleophilic character

Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

• Anne L. Schöffler,
• Ata Makarem,
• Frank Rominger and
• Bernd F. Straub

Beilstein J. Org. Chem. 2016, 12, 1566–1572, doi:10.3762/bjoc.12.151

• group prepared, isolated, and structurally characterized molecular dicopper acetylide complexes, and investigated their reactivity towards azide substrates [36]. For standard CuAAC reactions, copper(I) carboxylates [5][38], mononuclear copper(I) phosphine carboxylate complexes [39] or copper(I) salts

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• polyketides, they mostly appear in form of 3-acyltetronates and it was proposed that this structural motif is able to mimic corresponding anions of acidic functional groups like phosphates, sulphates or carboxylates. In fact, tetronates often act by inhibiting enzymes that process the respective functional

Towards potential nanoparticle contrast agents: Synthesis of new functionalized PEG bisphosphonates

• Souad Kachbi-Khelfallah,
• Maelle Monteil,
• Margery Cortes-Clerget,
• Evelyne Migianu-Griffoni,
• Jean-Luc Pirat,
• Olivier Gager,
• Julia Deschamp and
• Marc Lecouvey

Beilstein J. Org. Chem. 2016, 12, 1366–1371, doi:10.3762/bjoc.12.130

• bifunctional molecules substituted by amines, thiols, carboxylates, sulfonates, phosphonates or bisphosphonates [5][6][7]. Particularly, a strong interaction between the NPs and the phosphonic moiety was observed and more interestingly the best results were obtained with bisphosphonate products [8][9]. For the

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• ]; (ii) attack of a side-chain amine onto a carbonyl [86]; (iii) condensation between the N-terminal amine of the core peptide onto a side-chain carboxylate [87]. Biochemically, these macrolactams are formed via two distinct routes: (a) ATP-dependent activation of carboxylates [88], and (b) peptidase

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

• Jakub Saadi,
• Christoph Bentz,
• Kai Redies,
• Dieter Lentz,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• aryl iodide substituent were prepared following our well-established route via 2-siloxycyclopropane carboxylates D [6][7] that allows a regioselective introduction of the benzylic substituents at the α-carbon [8][9] to give intermediates E (Scheme 2). After fluoride-promoted ring opening [10] 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

• from the rhodium atom involved in the insertion mechanism increasing therefore its electrophilic character [12]. Four specific types of chiral rhodium(II) complexes can be found as catalyst in enantioselective insertion reactions of carbenoids in C(sp3)–H bonds: carboxylates [13][14][15][16][17][18][19

• desired azacycloalkenes 102a–c in 95–98% yield and 92–95 % ee (Table 11). Only the diene 100d did not cyclize and did not afford the nine-membered heterocycle by this methodology. In 2015, Hashimoto et al reported the synthesis of methyl 2-vinyltetrahydropyran-3-carboxylates (104) by an enantioselective

• approach to 2,3-dihydrobenzofurans. Enantioselective intramolecular rhodium carbenoid insertion into C(sp3)–H bonds to afford cis-disubstituted β-lactones. Enantioselective intramolecular rhodium carbenoid insertion into C(sp3)–H bonds to afford cis-2-vinyltetrahydropyran-3-carboxylates. First rhodium

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

• “coated” with water-solubilizing carboxylic acids/carboxylates to bestow good water solubility under basic conditions, and; 2) possessed a rim of hydrophobicity around the entrance to its interior hydrophobic pocket. We envisioned that driven by the hydrophobic effect this host would readily form 1:1

• carboxylates have proven to be one of the most reliable approaches to date, it is not the only approach. For example, working with Scott Grayson across town at Tulane University we successfully formed the dendrimer–coated host shown in Figure 8 [36], as well as wide series of polymer coated derivatives coupled

Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

• Tsuyuka Sugiishi,
• Hideki Amii,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2015, 11, 2661–2670, doi:10.3762/bjoc.11.286

• -scale operation. On the other hand, economical and useful perfluoroalkylated carboxylic acid derivatives, such as perfluoroalkylated carboxylates (CnF2n+1CO2Na or CnF2n+1CO2K), halodifluoroacetates (XCF2CO2R), perfluoroalkyl carboxylates (CnF2n+1CO2R), perfluoroalkyl ketones (CnF2n+1COR), and

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• Pyrococcus furiosus does not interfere. Decarboxylases A number of enzymes are capable of catalysing the reversible interconversion of lipophilic aromatics and the more polar respective carboxylates [12]. It is thought these reactions may proceed in the carboxylation direction as a detoxification mechanism

Convenient preparation of high molecular weight poly(dimethylsiloxane) using thermally latent NHC-catalysis: a structure-activity correlation

• Stefan Naumann,
• Johannes Klein,
• Dongren Wang and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 2261–2266, doi:10.3762/bjoc.11.246

• literature procedures (see Supporting Information File 1). Compounds 7-Neo-CO2, 7-iPr-CO2 and 5Cl-Me-CO2 have not been described before and full characterization can be found in the experimental part (Supporting Information File 1). In accordance with previous findings [17][27], these NHC-carboxylates were

• thermally labile pre-catalysts both practically feasible and advantageous. Conclusion In conclusion, we have demonstrated the first polymerization of D4 using NHC-carboxylates. Sterically non-hindered, highly nucleophilic protected NHCs like 5Me-Me-CO2 offer access to an “on demand”, metal-free and

• 5Me-Me-CO2. Note that the fivefold monomer excess was used in case of BnOH being present. Thermal activation of a 5Me-Me-CO2/BnOH/D4 (1:5:500) composition after a latency period of 72 h. NHC-carboxylates part of this study (top) and polymerization scheme with initial thermal decarboxylation and final

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• -wheel” of copper(II)–carboxylate complexes [28], a structure in which the two copper(II) ions are bridged by four carboxylates in a syn–syn configuration (dCu···Cu 2.613 Å), whilst two THF molecules occupy axial coordination sites. Complex 1 displays a monomeric structure with a distorted square

• molecules being most probably bound to the copper ions in aqueous solution, while in THF, the carboxylates interact more tightly with the copper ions. This is in agreement with the 1H NMR spectra of 1, which showed well resolved peaks for the benzophenone protons in D2O, while in THF-d8 broad resonances

Synthesis of quinoline-3-carboxylates by a Rh(II)-catalyzed cyclopropanation-ring expansion reaction of indoles with halodiazoacetates

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

Beilstein J. Org. Chem. 2015, 11, 1944–1949, doi:10.3762/bjoc.11.210

• Magnus Morten Martin Hennum Tore Bonge-Hansen Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, NO-0315 Oslo, Norway 10.3762/bjoc.11.210 Abstract In this letter, we report a novel synthesis of ethyl quinoline-3-carboxylates from reactions between a series of indoles and

• efficient method for the synthesis of ethyl quinoline-3-carboxylates from reactions between indoles and ethyl halodiazoacetates. The reaction propably follows a cyclopropanation-ring expansion pathway. Indoles with substituents in the 3,4,5 and 6 positions were good substrates for the reaction, but a

• commercially available indoles in combination with the scope of the reaction makes the cyclopropanation-ring expansion an attractive method for an efficient synthesis of quinolone-3-carboxylates. Experimental Detailed experimental procedures and analytical data for the compounds are available in Supporting

Fe(II)/Et₃N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

• Ekaterina E. Galenko,
• Olesya A. Tomashenko,
• Alexander F. Khlebnikov,
• Mikhail S. Novikov and
• Taras L. Panikorovskii

Beilstein J. Org. Chem. 2015, 11, 1732–1740, doi:10.3762/bjoc.11.189

• Emb. 7/9, 199034, St. Petersburg, Russia 10.3762/bjoc.11.189 Abstract A simple approach was developed for the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates from easily available compounds, 5-methoxyisoxazoles and phenacylimidazolium salts under hybrid Fe(II)/Et3N relay catalysis. The

• alkyl 2H-azirine-2-carboxylates can be prepared by isomerization of 5-alkoxyisoxazoles under Fe(II)-salt catalysis [30]. Quite recently this isomerization has been used for the preparation of substituted pyrrole-2-carboxylic acid derivatives by the domino reaction of 3-aryl-5-methoxyisoxazoles with 1,3

• ammonium formate as a source of hydrogen, to give the corresponding methyl 4-(1H-imidazol-1-yl)-1H-pyrrole-2-carboxylates 12 in high yields (Scheme 3). The reaction of aq KOH with imidazolium bromides 1 at room temperature afforded the corresponding stable ylides 2 (Table 2) in high yields without

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• –alkylidene-triggered metathesis-based polymerizations, Ru contamination was very low (<2.5 ppm) and even outrivals earlier reported systems bearing two pyridinium carboxylates by at least a factor of 10 [14]. Clearly, both the initiator and any Ru-containing decomposition products selectively stay in the IL

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

• diesters More recently, symmetric diesters have been synthetized exploiting both the activated extremities of divinyl carboxylates. C6-dicarboxylic acid diesters derivatives of the thiazoline of N-acetylglucosamine (NAG-thiazoline, 10a,b, Figure 2) were prepared and their inhibitor activities towards

• . The formed diol was mixed with an equal molar amount of divinyl sebacate and lipase as a catalyst, after some time methoxypoly(ethylene glycol) was added to react with the remaining vinyl carboxylates to give an amphiphilic polymer. This product self-assembled into nanometer-scale-sized particles in

Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

• Franziska Klitsche,
• Julian Ramcke,
• Julia Migenda,
• Andreas Hensel,
• Tobias Vossmeyer,
• Horst Weller,
• Silvia Gross and
• Wolfgang Maison

Beilstein J. Org. Chem. 2015, 11, 678–686, doi:10.3762/bjoc.11.77

• ], carboxylates [5] and phosphates [6] as well as phosphonates [7] for metal and metal oxide surfaces. In addition, bifunctional catechols like dopamine or DOPA (L-3,4-dihydroxyphenylalanine, Figure 1B), have received considerable interest as anchor groups for important metal surfaces such as titanium oxide, iron

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles

• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess and
• Viktor I. Saloutin

Beilstein J. Org. Chem. 2015, 11, 385–391, doi:10.3762/bjoc.11.44

• -oxo esters and their analogues with 5-aminotetrazole is an efficient synthetic approach to novel azaheterocycles. 2-Ethoxymethylidene-3-oxo esters bearing alkyl substituents react with 5-aminotetrazole to form ethyl 2-azido-4-alkylpyrimidine-5-carboxylates which are capable of subsequent nucleophilic

• amounts of sodium acetate in the reaction of fluorinated esters 1a,b with 5-AT in 1,4-dioxane under reflux leads to the formation of ethyl 2-amino-4-(polyfluoroalkyl)pyrimidine-5-carboxylates 4a,b (Scheme 2). In the case of 1a (R = CF3), ethyl 2-(1H-tetrazol-5-ylamino)-4-(trifluoromethyl)-pyrimidine-5

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• azadienes onto the keto group, provides a rapid access to non-fused 2H-1,4-oxazine-5-carboxylates 4, a new type of non-spirocyclic 1,4-oxazine photochromes [15]. In the search for new compounds with useful photochromic characteristics and a high fatigue resistance we focused on 5-unsubstituted, 5-aryl-, and

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• carboxylates affords compounds 33a–c in moderate to good yields, whereas the reaction with NaN3 provided the ω,ω’-diazide 34. The latter compound served as interface for labelling with various alkyne-functionalized compounds. As proof-of-concept we successfully coupled 34 with the perylene derivative 35 to