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

• the literature. They can be obtained from enones by Michael addition of nitromethane, partial reduction and dehydrogenation of the resulting pyrroline with selenium or sulfur in moderate yields (3 steps) [40][41]. Alternatively, a Nef reaction of the nitromethane adducts gives masked 1,4-dicarbonyls

The Flögel-three-component reaction with dicarboxylic acids – an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives

• Mrinal K. Bera,
• Moisés Domínguez,
• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 394–404, doi:10.3762/bjoc.10.37

• compounds. An alternative option for the side chain functionalization of 4- or 6-methyl substituted pyrimidines involves an oxidation with selenium dioxide (Riley oxidation [66][67][68]). To explore the synthetic potential of the newly prepared compounds we exemplarily oxidized bis(pyrimidine) 23a by this

• method in order to finally prepare a macrocyclic compound such as 34 (Scheme 7). Treatment of 23a with an excess of selenium dioxide at 90 °C resulted in the formation of an inseparable mixture of two different aldehydes (probably the dialdehyde and the monoaldehyde). After reduction of the mixture with

Novel supramolecular affinity materials based on (−)-isosteviol as molecular templates

• Christina Lohoelter,
• Malte Brutschy,
• Daniel Lubczyk and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2013, 9, 2821–2833, doi:10.3762/bjoc.9.317

• , (−)-isosteviol can be oxidized under Riley conditions (Table 1, reaction conditions a: selenium dioxide/xylene) [62][63] to give the corresponding diketone 9 [66]. Subsequent esterification with 3,5-dinitrobenzylic chloride under basic conditions (Table 1, reaction conditions b for R = DNB) [67] proceeds with a

The renaissance of organic radical chemistry – deja vu all over again

• Corey R. J. Stephenson,
• Armido Studer and
• Dennis P. Curran

Beilstein J. Org. Chem. 2013, 9, 2778–2780, doi:10.3762/bjoc.9.312

• ][14][15][16], e) radical trifluoromethylation [17] and radical fluorination [18][19][20], f) natural product synthesis [21], g) new main group radical chemistry involving elements like boron [22], phosphorous [23] and selenium [24], tellurium [25], among others, h) synthesis or functionalization of

New syntheses of 5,6- and 7,8-diaminoquinolines

• Maroš Bella and
• Viktor Milata

Beilstein J. Org. Chem. 2013, 9, 2669–2674, doi:10.3762/bjoc.9.302

• treatment of hydrochloride 5 with selenium dioxide in water at room temperature afforded selenadiazoloquinoline 6 in 76% yield (Scheme 2) in comparison with 18% yield obtained by heating of diaminoquinoline 3 with selenium dioxide in dioxane under reflux [9]. To date, pyridoquinoxaline 8 has been prepared

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• enantioselectivities were obtained under the reverse ratio of the reagents. Della Sala’s group [47] has demonstrated the first example of a meso-aziridine desymmetrization with selenium nucleophiles to produce chiral β-aminoselenides in high enantioselectivities (up to 99% ee). Surprisingly, when the sterically

Organocatalytic asymmetric selenofunctionalization of tryptamine for the synthesis of hexahydropyrrolo[2,3-b]indole derivatives

• Qiang Wei,
• Ya-Yi Wang,
• Yu-Liu Du and
• Liu-Zhu Gong

Beilstein J. Org. Chem. 2013, 9, 1559–1564, doi:10.3762/bjoc.9.177

• products; selenofunctionalization; Introduction Selenofunctionalization of carbon–carbon double bonds provides practicable opportunities for rapid construction of molecule complexity [1][2][3][4][5][6][7][8], because the versatile carbon–selenium bond could either stabilize carbanions [9][10], serve as a

Photoinduced synthesis of unsymmetrical diaryl selenides from triarylbismuthines and diaryl diselenides

• Yohsuke Kobiki,
• Shin-ichi Kawaguchi,
• Takashi Ohe and
• Akiya Ogawa

Beilstein J. Org. Chem. 2013, 9, 1141–1147, doi:10.3762/bjoc.9.127

• triphenylbismuthine (2a, 0.5 mmol) were placed in a Pyrex test tube ( = 9 mm) with CHCl3 (4 mL), and the mixture was irradiated by a xenon lamp for 5 h at room temperature. As a result, 0.042 mmol (21% yield based on the amount of selenium atoms) of diphenyl selenide (3aa) was obtained after the isolation by silica

• affords unsymmetrical diaryl selenides in good yields. This method is efficient, because two arylseleno groups from diaryl selenides can be used as a selenium source, and its advantage is that the reaction proceeds in the absence of transition-metal catalysts. Experimental General comments Compounds 1a

Isotopically labeled sulfur compounds and synthetic selenium and tellurium analogues to study sulfur metabolism in marine bacteria

• Nelson L. Brock,
• Christian A. Citron,
• Claudia Zell,
• Martine Berger,
• Irene Wagner-Döbler,
• Jörn Petersen,
• Thorsten Brinkhoff,
• Meinhard Simon and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 942–950, doi:10.3762/bjoc.9.108

• sulfur source for the MeSH volatiles, whereas incorporation of labeling from sulfate was not observed. Moreover, the utilization of selenite and selenate salts by marine alphaproteobacteria for the production of methylated selenium volatiles was explored and resulted in the production of numerous

• methaneselenol-derived volatiles via reduction and methylation. The pathway of selenate/selenite reduction, however, proved to be strictly separated from sulfate reduction. Keywords: dimethylsulfoniopropionate; Roseobacter clade; selenium metabolism; sulfur metabolism; volatiles; Introduction The Roseobacter

• -serine to L-cysteine. Elemental sulfur, hydrogen sulfide, or thiosulfate can be funneled via the lithotrophic sulfur oxidation (Sox) pathway to sulfate [18][19][20][21][22]. Analogous degradation steps for the selenium and tellurium derivatives of DMSP (dimethylseleniopropionate, DMSeP, and

Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• , such as halogen–lithium exchange, tin–lithium exchange, selenium–lithium exchange or reductive lithiation [1][2][3][4][5][6][7][8]. Once the organolithium has been generated, the intramolecular carbolithiation reaction usually takes place with high stereochemical control, as a consequence of a rigid

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• overall yields were very good (78–91%); the relative yields of the three dimers were not determined, however. A monosubstituted bisallene has been prepared by Braverman and co-workers by treatment of the sulfonium or selenium salt 108 with DBU in acetone at 0 °C, providing a mixture of 109 and 110 in a 7

Supramolecular hydrogels formed from poly(viologen) cross-linked with cyclodextrin dimers and their physical properties

• Yoshinori Takashima,
• Yang Yuting,
• Miyuki Otsubo,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1594–1600, doi:10.3762/bjoc.8.182

• adding selenium or platinum complexes yields supramolecular assemblies of bis(molecular tube)s cross-linked with the β-CD dimer, which form nanofibers [12][13][14][15]. Moreover, mechanically linked polyrotaxane with the α-CD and poly(ethylene glycol) (PEG) produces a hydrogel material, which exhibits

Synthesis and characterization of Sant-75 derivatives as Hedgehog-pathway inhibitors

• Chao Che,
• Song Li,
• Bo Yang,
• Shengchang Xin,
• Zhixiong Yu,
• Taofeng Shao,
• Chuanye Tao,
• Shuo Lin and
• Zhen Yang

Beilstein J. Org. Chem. 2012, 8, 841–849, doi:10.3762/bjoc.8.94

• the presence of catalytic NaOMe, followed by treatment with NH4Cl. Then, condensation of 13 with acetylacetaldehyde dimethyl acetal in 1,4-dioxane afforded 6-methyl-2-(4-pyridinyl)pyrimidine 14 in 62% yield [47]. Consequent allylic oxidation of 14 with selenium dioxide gave 11e in moderate yield

Synthesis of functionalized macrocyclic derivatives of trioxabicyclo[3.3.0]nonadiene

• Sabine Leber,
• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2012, 8, 738–743, doi:10.3762/bjoc.8.83

• the bisdioxine-derived macrocycles. Okazaki and co-workers designed bowl-shaped [8] and lantern-shaped [9] molecules containing a functionalized aryl group, which allowed the preparation of, among other things, stable simple enols [8] and a variety of unusual sulfur [9], selenium [10][11] and

Synthesis and oxidation of some azole-containing thioethers

• Andrei S. Potapov,
• Nina P. Chernova,
• Vladimir D. Ogorodnikov,
• Tatiana V. Petrenko and
• Andrei I. Khlebnikov

Beilstein J. Org. Chem. 2011, 7, 1526–1532, doi:10.3762/bjoc.7.179

• . Selenium dioxide-catalyzed oxidation of benzotriazole thioether by H2O2, however, proceeds selectively and yields sulfoxide only. Keywords: azole; oxidation; sulfone; sulfoxide; thioether; Introduction Compounds comprising two pyrazole moieties linked by an aliphatic spacer act as bidentate chelating

•  1, entry 4). It is evident that hydrogen peroxide alone is not an effective oxidant for thioether 5, therefore other oxidizing systems should be evaluated. Selenium(IV) oxide was reported to be an efficient catalyst in a thioether oxidation reaction promoted by H2O2 [17]. However, the performance of

• sulfone can be selectively isolated by varying the oxidation conditions. Sulfone can be prepared by the addition of an excess of H2O2 in acetic acid at elevated temperature, while sulfoxide is selectively formed upon the addition of H2O2 and selenium dioxide in methanol. Experimental General methods

A novel high-yield synthesis of aminoacyl p-nitroanilines and aminoacyl 7-amino-4-methylcoumarins: Important synthons for the synthesis of chromogenic/fluorogenic protease substrates

• Xinghua Wu,
• Yu Chen,
• Herve Aloysius and
• Longqin Hu

Beilstein J. Org. Chem. 2011, 7, 1030–1035, doi:10.3762/bjoc.7.117

• reach completion. After the completion of selenocarboxylation as monitored by LC-MS, a solution of azide in THF was added by syringe or cannulation. The reaction started immediately with the precipitation of gray selenium and the formation of nitrogen gas, and was complete within 2 h at room temperature

• isopropanol solution of sodium hydrogenselenide [22]. To a suspension of selenium (40 mg, 0.5 mmol) in deaerated isopropanol (5 mL) was added sodium borohydride (24 mg, 0.6 mmol) in one portion at room temperature. The mixture was stirred under a nitrogen atmosphere to provide a colorless solution of NaHSe in

• isopropanol, which was ready to be used. Preparation of an aqueous solution of sodium hydrogenselenide [22]. To a suspension of selenium (40 mg, 0.5 mmol) in deaerated distilled water (5 mL) was added sodium borohydride (40 mg, 1.0 mmol) in one portion at 5 °C. The mixture was vigorously stirred under a

Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation

• Vadim A. Soloshonok and
• Donna J. Nelson

Beilstein J. Org. Chem. 2011, 7, 744–758, doi:10.3762/bjoc.7.85

• straightforward and general methods for the preparation of the corresponding selenium derivatives, which are useful intermediates in organic synthesis, often with interesting biological applications [4][5]. Thus, organoselenium compounds are reported to have antitumor [6][7][8], antimicrobial [7][8], antiviral [7

• ][8], and anti-oxidant [9][10] properties. It is interesting to note that the current applications of organoselenium derivatives have outpaced those of conventional inorganic selenium compounds [6][7][8][9][10]. This potential in biological applications [11] of organoselenium compounds is enhanced by

• reactivity of organoselenium compounds, it is expected that chiral selenium containing derivatives could be synthetically useful as chiral auxiliaries or intermediates for the development of a novel asymmetric methodology platform [15][16][17][18]. Furthermore, compared with sulfur analogs [44], chiral

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• , separation of the diastereomers by flash chromatography was possible, affording the pure tetrahydropyridine derivative trans-133 in 74% yield. Successive epoxidations on enantiopure trans-133 and then 134, followed each time by regioselective epoxide opening (with a selenium–boron complex and water

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• their effects appear to be a general phenomenon in metathesis chemistry. In this review, we collect these reports and discuss the activating effect of allylic chalcogens, such as oxygen, sulfur and selenium, as well as their relative reactivity in olefin metathesis. The applications of the allylic

• allyl sulfide with combined CM yields of 73% (CM and self-metathesis) and 45% (CM only, no self-metathesis observed), respectively (Scheme 11b) [38]. This further improvement in reactivity may be attributed to the increased softness of selenium which makes the coordination to ruthenium even more

• favorable than the sulfur in allyl sulfides. While, as a single example, Kotetsu and co-workers have synthesized selenium-containing bicyclic β-lactams via RCM of an allyl selenide derivative, enhanced reactivity was unnoticed [39]. With a better understanding of the allylic chalcogen effect, olefin

Intramolecular hydroxycarbene C–H-insertion: The curious case of (o-methoxyphenyl)hydroxycarbene

• Dennis Gerbig,
• David Ley,
• Hans Peter Reisenauer and
• Peter R. Schreiner

Beilstein J. Org. Chem. 2010, 6, 1061–1069, doi:10.3762/bjoc.6.121

• , was added 3.33 g (30.0 mmol) of selenium dioxide. The mixture was stirred at 80 °C for 4 h. After filtration, concentration of the solution gave a brown oil that was dissolved in 5% sodium hydroxide solution and washed three times with small portions of diethyl ether. The aqueous layer was acidified

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33