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

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

• metal cations (Mg2+, Al3+), which rapidly are coordinated by the carboxylate anions formed at the cathode. Finally, the corresponding metal carboxylates can be precipitated from organic solvents allowing easy product isolation. Alongside all the benefits that are associated with these sacrificial anodes

• generated carboxylates, make the use of a membrane redundant, enabling the use of a simple undivided cell [44]. Moreover, the use of membranes in non-aqueous or aprotic environments is unsatisfactory as they become poorly conducting [44]. This procedure was patented and extended to various other substrates

Supercritical carbon dioxide: a solvent like no other

• Jocelyn Peach and
• Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

• investigated by Howdle et al. [90]. When the PFPE polymers were in their carboxylic acid form no microemulsions were formed, however, upon the conversion of the headgroups to ammonium carboxylates w/c microemulsions were observed. The length of the polymer tail was also shown to affect the ability to form

Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions

• Andreas Gansäuer,
• Andreas Okkel,
• Lukas Schwach,
• Laura Wagner,
• Anja Selig and
• Aram Prokop

Beilstein J. Org. Chem. 2014, 10, 1630–1637, doi:10.3762/bjoc.10.169

• structural feature [31]. The gelation ability of the neutral ester-substituted titanocenes critically depends on the steric demand of the substituents on the cyclopentadienyl ligands. The carboxylates are valuable complexes for mediating highly chemoselective Barbier type allylations [32][33]. These findings

• started our investigation with the preparation of azide-substituted cationic titanocenes. To this end, the titanocene carboxylates 1–3 shown in Figure 1 were employed as substrates because their substitution pattern should allow a first simple assessment of structure–activity relationships. The compounds

• A–D shown in Figure 2 were used as amino-substituted azides. They are readily obtained from the corresponding diazides through a Staudinger reaction (see Supporting Information File 1 for details) [45][46]. As for the carboxylates the different tether lengths and substitution patterns of the arene

Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

• Bernd Schmidt and
• Sylvia Hauke

Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102

• furanose 17. Facile migration of carboxylates upon TBAF-mediated desilylation of a vicinal alcohol has previously been observed by us in a different context [68]. We assume that this process starts with a nucleophilic attack of the alkoxylate 18 at the ester carbon, giving a five membered intermediate 19

Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

• Zong Guan,
• Jan C. Namyslo,
• Martin H. H. Drafz,
• Martin Nieger and
• Andreas Schmidt

Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79

• indazole 3 has been generated by thermal decarboxylation of indazolium-3-carboxylates 1 [20] which belong to the class of pseudo-cross-conjugated heterocyclic mesomeric betaines (Scheme 1). Its properties have been calculated [20][21] and examined by means of vibrational spectroscopy [21]. It was shown

• aforementioned class of pseudo-cross-conjugated heterocyclic mesomeric betaines. Thus the intermediates III are related to indazolium-3-carboxylates, -amidates, and -thioamidates shown in Scheme 1 and Scheme 2. The neutralization of the charges in cross-conjugated as well as in pseudo-cross-conjugated mesomeric

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• -1H-pyrazole-4-carbonitrile (5a), alkyl 3-hydroxypyrazole-4-carboxylates 5b, 5c or 1-(3-methyl-1H-pyrazol-4-yl)ethanone (5d). The reversed addition of the enol ethers to hydrazine hydrate the formation of bis-enehydrazine 6 product was observed in two tautomeric forms: with symmetrical and

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• products and 3,5-disubstituted pyrrole-2-carbonitriles 10 are obtained. Tsuge et al. reported the oxidation of pyrroline-3-carboxylates with chloranil [45] while pyrrole-2-carboxylates were obtained from the oxidation of pyrroline-2-carboxylate with chloranil [46][47] or DDQ [48]. Different oxidants were

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes

• Moustafa Sherief Moustafa,
• Saleh Mohammed Al-Mousawi,
• Maghraby Ali Selim,
• Ahmed Mohamed Mosallam and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2014, 10, 141–149, doi:10.3762/bjoc.10.11

• the products. Finally, these compounds were used for the efficient synthesis of 6-amino-5-cyanonicotinic acid ester derivatives 31a,b, ethyl 4-amino-5H-pyrano[2,3-d]pyrimidine-6-carboxylates 33a,b, 4-amino-6H-pyrrolo[3,4-g]quinazoline-9-carbonitrile 39, and 1,7-diamino-6-(N'-hydroxycarbamimidoyl)-3

• acid derivatives 31a,b, ethyl 4-amino-5H-pyrano[2,3-d]pyrimidine-6-carboxylates 33a,b, 4-amino-6H-pyrrolo[3,4-g]quinazoline-9-carbonitrile 39, and 1,7-diamino-6-(N'-hydroxycarbamimidoyl)-3-oxo-5-phenyl-3H-isoindole-4-carboxylate 40. X-ray crystal structure of 9. X-ray crystal structure of 13a. X-ray

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• electrocyclic ring opening to carboxylates 6 [25], although a non-concerted pathway can not be excluded (Scheme 1). To the best of our knowledge, metathesis/non-metathesis one flask sequences have not been used before for the two directional elaboration or desymmetrization of C2-symmetric building blocks. In

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

• Kegong Ji,
• Jonathan Nelson and
• Liming Zhang

Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227

• Kegong Ji Jonathan Nelson Liming Zhang Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, 93106, USA 10.3762/bjoc.9.227 Abstract Gold-catalyzed intermolecular oxidation of carboxylates of primary or secondary propargylic alcohols are realized with

• regioselectivities of this oxidation with different types of internal alkynes, we examined propargylic carboxylates, which have served as a versatile platform for the development of a diverse range of gold catalysis [21]. Herein we report our findings and the development of a reliable synthesis of α-carboxy α,β

• following observations and considerations: a) propargylic carboxylates of type 4a with an internal C–C triple bond typically undergo facile 3,3-rearrangements [26][27][28][29][30] instead of 1,2-acyloxy migrations. The former process would eventually lead to the formation of the enones 6 [31]. Due to

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• hexanoic acid > acetylacetone [53][54], it is possible to assign Cu(acac)2, which is ineffective in promoting the reaction, as the weakest oxidant. On the other hand, CuCl2 and Cu(OTf)2 induce reactions that follow a different pathway from those promoted by copper(II) carboxylates. These observations

• suggest that a rapid equilibrium does indeed exist between isomeric radical intermediates 9 and 10 (Scheme 7) and that the thermodynamically less stable isomer 9 undergoes fast hexenyl-radical cyclization leading to the formation of 11 in reactions promoted by copper(II) carboxylates. On the other hand, a

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• more reactive than a phenyltelluranyl radical. Substitution of halides (X), carboxys (COOR), or carboxylates (OCOR) with phosphorus After scattered research efforts into the uncontrolled radical C–H phosphination under harsh reaction conditions [40], Barton elegantly devised radical decarboxylative

Use of 3-[¹⁸F]fluoropropanesulfonyl chloride as a prosthetic agent for the radiolabelling of amines: Investigation of precursor molecules, labelling conditions and enzymatic stability of the corresponding sulfonamides

• Reik Löser,
• Steffen Fischer,
• Achim Hiller,
• Martin Köckerling,
• Uta Funke,
• Aurélie Maisonial,
• Peter Brust and
• Jörg Steinbach

Beilstein J. Org. Chem. 2013, 9, 1002–1011, doi:10.3762/bjoc.9.115

• corresponding potassium carboxylates under mild anhydrous conditions [37]. Its successful use for the acceleration of O-sulfonylations was recently described by Musachio et al. [38]. Conversion of [18F]10 with 4-nitroaniline in the presence of potassium trimethylsilanolate led to the formation of the desired

1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

• Astrid Hoppe,
• Faten Sadaka,
• Claire-Hélène Brachais,
• Gilles Boni,
• Jean-Pierre Couvercelle and
• Laurent Plasseraud

Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73

• under vacuo (method A) or by addition of NaBPh4 (method B). Possible catalytic and deactivation mechanisms are proposed. Keywords: aliphatic polyesters; green polymerization reaction; imidazolium-2-carboxylates; N-heterocarbene precursor; organocatalysis; Introduction Poly(ε-caprolactone) (PCL) and

• . In this quest and encouraged by our previous results, we chose to explore the potential of zwitterionic 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2, Figure 1). Indeed, methylimidazolium-2-carboxylates can be easily synthesized with high yields by the one-pot reaction of dimethyl carbonate

• concept was extended to the synthesis of aliphatic polycarbonates, involving the transesterification of DMC with linear alkane diols under solvent-free conditions, and based on a two-step polymerization process [50]. The high reactivity of imidazolium-2-carboxylates can be explained by their facile

A computational study of base-catalyzed reactions of cyclic 1,2-diones: cyclobutane-1,2-dione

• Nargis Sultana and
• Walter M. F. Fabian

Beilstein J. Org. Chem. 2013, 9, 594–601, doi:10.3762/bjoc.9.64

• bicyclic intermediate Int4 was found (Figure 4). Furthermore, this intermediate did not react to product P3 but instead through a concerted ring opening and proton transfer to P3a. The anticipated product P3 of path C is a γ-oxocarboxylate. Such γ-oxocarboxylic acids or carboxylates are prone to ring–chain

A one-pot catalyst-free synthesis of functionalized pyrrolo[1,2-a]quinoxaline derivatives from benzene-1,2-diamine, acetylenedicarboxylates and ethyl bromopyruvate

• Mohammad Piltan,
• Loghman Moradi,
• Golaleh Abasi and
• Seyed Amir Zarei

Beilstein J. Org. Chem. 2013, 9, 510–515, doi:10.3762/bjoc.9.55

• ][26]. Ma and Yuan have reported the synthesis of pyrrolo[1,2-a]quinoxalin-4(5H)-ones by CuI/L-proline-catalyzed coupling of N-trifluoroacetyl-2-haloanilines with methyl pyrrole-2-carboxylates [27]. The development of more efficient methods for the preparation of these compounds is still an active

The multicomponent approach to N-methyl peptides: total synthesis of antibacterial (–)-viridic acid and analogues

• Ricardo A. W. Neves Filho,
• Sebastian Stark,
• Bernhard Westermann and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2012, 8, 2085–2090, doi:10.3762/bjoc.8.234

• -terminus, which bears a N,N-dimethyl anthranilic amide moiety of still unknown biosynthetic origin. The previously reported synthetic strategy toward 1 was based upon a series of peptide couplings employing DCC reagent [5]. The necessity of difficult-to-perform peptide couplings with phenyl carboxylates

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• acetone-sensitised photodecarboxylation chemistry initially developed by Griesbeck [58] under batch conditions was suggested as being ideally suited to microflow conditions [59][60]. The chemistry involves the decarboxylative addition of potassium carboxylates to phthalimides, thus offering an alternative

• interest is the addition of carboxylates 46 to phthalimides 45 shown in Scheme 16. This reaction has also been compared for microflow and batch reactors for a number of substrates [61][62], and again, although residence times are lower under microflow conditions, productivity is higher for the batch

• completion [61]. In an extension of the above reactions, it was shown that α-thioalkyl-substituted carboxylates 50 could be added to phthalimides 45 in a microflow reactor (Scheme 16). Although the flow reaction proved successful, the final ratio of the desired product 51 to the unwanted reductive dimer 52

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Facile synthesis of functionalized tetrahydroquinolines via domino Povarov reactions of arylamines, methyl propiolate and aromatic aldehydes

• Jing Sun,
• Hong Gao,
• Qun Wu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2012, 8, 1839–1843, doi:10.3762/bjoc.8.211

• propiolates, and successfully established the imino Diels–Alder reaction with β-enamino ester as dienophile. This reaction provides a convenient and stereoselective procedure for the preparation of 2-aryl-4-arylamino-1,2,3,4-tetrahydroquinoline-3-carboxylates in satisfactory yields. Furthermore, we

Synthesis and ring openings of cinnamate-derived N-unfunctionalised aziridines

• Alan Armstrong and
• Alexandra Ferguson

Beilstein J. Org. Chem. 2012, 8, 1747–1752, doi:10.3762/bjoc.8.199

• -opening protocols have been developed, synthesis of the starting NH-aziridine-2-carboxylates is multistep and low-yielding. Synthetic routes include Gabriel–Cromwell addition of ammonia to an enoate [16][17]; epoxide opening with azide, followed by ring closure [19]; and a sequence of olefin

• aziridination methodology to access NH-aziridine-2-carboxylates in a single step from enoates. To the best of our knowledge, there exist only three examples of this transformation. Furukawa used diphenyl sulfilimine to form NH-aziridines from fumarate esters [32], and O-mesitylenesulfonylhydroxylamine (MSH) was

• moderate. Nonetheless, it is worth noting that this single-step transformation provides NH-aziridine-2-carboxylates in competitive or superior yields to alternative multistep methodologies. Having explored the scope of the aziridination, we were keen to investigate the susceptibility of our unactivated NH