The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• derivatives PM allows a variety of subsequent transformations to new derivatives. The C-4 methyl (in one case benzyl) group is an inevitable structural feature of these pyrimidines, but it can smoothly be used for oxidation reactions to introduce new functional groups. As typical examples selenium dioxide

• reasonable overall yields (Scheme 20) [30]. This pathway via the pyrimidine N-oxides represents a good alternative to the direct oxidation of the 4-methyl group by selenium dioxide (see Scheme 11). The subsequent transformation of the aldehyde PM71 to the oxime followed by dehydration afforded nitrile PM72

• of pyrimidine derivatives PM through selenium dioxide oxidations of PM5, PM9, PM15 and PM19 leading to 4-formyl-substituted pyrimidines PM41, PM42, PM44 and PM48 and selected subsequent transformations (TosMIC = tosylmethyl isocyanide). Conversion of 2-vinyl-substituted pyrimidine PM7 into aldehyde

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• diphenyl diselenides 12 for the synthesis of 2-phenylseleny-3,3-diarylcyclobutenes 13 under visible light irradiation (Scheme 5) [51]. The desired products 13 contained a cyclobutene group and a selenium atom, which makes the products possess unique biological and pharmaceutical activities. The mechanism

• synthesis of 1-naphthaldehydes 25 under mild conditions via a radical-mediated ring-opening and intramolecular cyclization of MCPs 23 with organic selenium reagents 24 (Scheme 8) [59]. In this reaction, the MCPs with electron-withdrawing groups gave lower yields than that with electron-donating groups

• diethyl phosphites. Organic-selenium induced radical ring-opening and cyclization of MCPs derivatives (cyclopropylaldehydes). Copper(I)-catalyzed oxidative radical trifluoromethylation/ring-opening/cyclization of MCPs with Togni reagent II. Ag(I)-mediated trifluoromethylthiolation/ring-opening/cyclization

Molecular iodine-catalyzed one-pot multicomponent synthesis of 5-amino-4-(arylselanyl)-1H-pyrazoles

• Camila S. Pires,
• Daniela H. de Oliveira,
• Maria R. B. Pontel,
• Jean C. Kazmierczak,
• Roberta Cargnelutti,
• Diego Alves,
• Raquel G. Jacob and
• Ricardo F. Schumacher

Beilstein J. Org. Chem. 2018, 14, 2789–2798, doi:10.3762/bjoc.14.256

• -(phenylselanyl)-1H-pyrazol-5-amine was submitted to an oxidative dehydrogenative coupling to produce a diazo compound confirmed by X-ray analysis. Keywords: diaryl diselenide; diazo compound; 1H-pyrazole; molecular iodine; multicomponent reaction; Introduction Selenium-containing compounds are of great

• β-ketonitriles, arylhydrazines and aryl sulfonyl hydrazides as sulfur source [21]. The chemistry of iodine-catalyzed transformations has emerged as a greener, efficient and economical alternative to transition metals in organic synthesis [22][23][24]. However, the synthesis of selenium-containing 5

• Lewis acid to generate the hydrazone intermediate A. Then, hydrazone A undergoes a cyclization reaction followed by an oxidative aromatization to yield 1H-pyrazol-5-amine 5. At the same time, the diaryl diselenide 3 reacts with the molecular iodine to generate an electrophilic selenium species B. The

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

• Takashi Go,
• Akane Morimatsu,
• Hiroaki Wasada,
• Genzoh Tanabe,
• Osamu Muraoka,
• Yoshiharu Sawada and
• Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

• under Pummerer reaction conditions of sulfoxides and the results are shown in Scheme 3. We first examined the following one-pot sequential reactions of the selenium analog: the mCPBA oxidation of N-allylpyrrolomethylselenide 6a, the following Pummerer reaction, and final treatment with TBAH. The

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• , entry 3). When other oxidants, such as selenium oxide and manganese dioxide, were used, even at reflux temperature, no reaction took place (Table 2, entries 4 and 5). Owing to the concern of heavy metal pollution from the metal oxidant, organic oxidants were tested. Fortunately, DDQ in dioxane could

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• metal-free alternative to the previous methods of formation of sulfur heterocycles 70 has been reported by using elemental sulfur in the presence of cesium carbonate (Scheme 32) [72]. The strategy can be extended to the synthesis of the cyclic selenium analogs 71 by utilizing elemental selenium and

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• ) 2.1.1. Oxidation of benzo[7]annulenes: 4,5-Benzotropone (11) was synthesized for the first time via oxidation with selenium dioxide of 7H-benzo[7]annulene (14, Scheme 2) [39][40][41][42][43][44][45]. Furthermore, the direct oxidation of 5H-benzo[7]annulene to benzotropones was examined by Srivastava and

• Dev [37]. The selenium dioxide oxidation of 5H-benzo[7]annulene (15) furnished not only 4,5-benzotropone (11; 27%) but also 2,3-benzotropone (12; 13%, Scheme 2). Pomerantz and Swei [51] investigated the oxidation of benzotropylium cation 16 with several oxidants. The oxidants used and results obtained

• synthesis of Julia’s ketone was achieved by dehydration of the known keto-alcohol 164 by boric acid. Oxidation of Julia’s ketone with selenium dioxide gave 2,3-benzotropone (12). An alternative synthesis for 12, which represents a feasible route to avoid the disadvantage of selenium dioxide, is also

Electrophilic trifluoromethylselenolation of terminal alkynes with Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate

• Clément Ghiazza,
• Anis Tlili and
• Thierry Billard

Beilstein J. Org. Chem. 2017, 13, 2626–2630, doi:10.3762/bjoc.13.260

• nucleophilic approach is based on the use of the CF3Se− anion which must be prepared from stoichiometric amounts of metallic selenium [40][41][42][43][44][45][46][47][48][49][50][51][52][53]. Concerning the electrophilic approach, two reagents, that are easy to obtain, have been described: CF3SeCl [38][54][55

Synthesis and photophysical properties of novel benzophospholo[3,2-b]indole derivatives

• Mio Matsumura,
• Mizuki Yamada,
• Atsuya Muranaka,
• Misae Kanai,
• Naoki Kakusawa,
• Daisuke Hashizume,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2017, 13, 2304–2309, doi:10.3762/bjoc.13.226

• ]indole 3 in 66% yield. Then, the chemical modification of the phosphorus atom of 3 was carried out and the results are shown in Scheme 2. The treatment of 3 with hydrogen peroxide, elemental sulfur, and elemental selenium afforded the corresponding phosphine oxide 4, sulfide 5, and selenide 6

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• precursors using metal-based reagents. For example selenium dioxide (SeO2, 10 equiv) has been used in the presence of an acid for oxidative dehydrogenation of tetrahydro-β-carbolines 49 to afford aromatic β-carbolines 50 (Scheme 15) [65]. Bhutania et al. [66] has also reported a similar synthesis of 1-aryl-β

• MnO2. Selenium dioxide and potassium dichromate-mediated oxidative dehydrogenation of tetrahydro-β-carbolines [65][66]. Synthesis of substituted benzazoles in the presence of barium permanganate. Oxidative dehydrogenation with phenanthroline-based catalysts. PPTS = pyridinium p-toluenesulfonic acid

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

• Serge Pérez and
• Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

• interaction with the protein led to the development of different molecular modelling methods. A somehow indirect application of the fine specificity of the binding of oligosaccharides to lectins has been elegantly developed to solve the phase problem in protein crystallography. Selenium-labelled carbohydrates

Transition-metal-free one-pot synthesis of alkynyl selenides from terminal alkynes under aerobic and sustainable conditions

• Adrián A. Heredia and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2017, 13, 910–918, doi:10.3762/bjoc.13.92

• acetylenes. Keywords: alkynyl selenide; electrophilic cyclization; nucleophilic substitution; potassium selenocyanate; terminal alkynes; Introduction Alkynyl selenides, as many other selenium compounds, have potential anti-oxidant activities, and may play a role in certain diseases such as cancer, heart

• for their synthesis have been developed. Among them are reactions between lithium or sodium acetylides and electrophilic selenium reactants [23]. The use of hypervalent iodine(III) species [24] or alkynyl bromides with RSeLi [25] as nucleophilic selenium species or the reaction of alkynyl bromides

• of obtaining alkynyl analogues based on our methodology developed for the synthesis of vinyl selenides. We herein report the optimized reaction conditions for the one-pot and three-step synthesis of alkynyl selenides 5 using KSeCN as selenium source in PEG 200 as the solvent under an oxygen

Ultrasound-promoted organocatalytic enamine–azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones

• Gabriel P. Costa,
• Natália Seus,
• Juliano A. Roehrs,
• Raquel G. Jacob,
• Ricardo F. Schumacher,
• Thiago Barcellos,
• Rafael Luque and
• Diego Alves

Beilstein J. Org. Chem. 2017, 13, 694–702, doi:10.3762/bjoc.13.68

• carbonyl compounds could successfully generate an enamine or an enolate, and these species react as dipolarophiles with organic azides in organocatalyzed 1,3-dipolar cycloadditions. Our research group has demonstrated β-enamine–azide cycloaddition reactions for the synthesis of selenium-functionalized

• environmentally sound substrates for the preparation of selenium-functionalized 1,2,3-triazoles still remains a challenge in organic synthesis. Ultrasonic irradiation has emerged in the past decades as a versatile tool in industrial and academic applications [62][63][64][65][66][67]. The use of sonication in

• -amides with a range of substituted aryl azides providing and efficient access to new N-aryl-1,2,3-triazoyl carboxamides in good to excellent yields and short reaction times of [75]. However, to the best of our knowledge, the use of sonochemistry to synthesize complex selenium-functionalized 1,2,3

Dimerization reactions of aryl selenophen-2-yl-substituted thiocarbonyl S-methanides as diradical processes: a computational study

• Michael L. McKee,
• Grzegorz Mlostoń,
• Katarzyna Urbaniak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 410–416, doi:10.3762/bjoc.13.44

• intermediate, delocalized diradical species. The influence of selenium as a ‘heavy atom’ for stabilization of this intermediate has been emphasized. Keywords: 1,3-dipolar cycloadditions; reaction mechanisms; reactive intermediates; thiocarbonyl S-methanides; thioketones; Introduction Thiocarbonyl S

Nucleophilic displacement reactions of 5′-derivatised nucleosides in a vibration ball mill

• Olga Eguaogie,
• Patrick F. Conlon,
• Francesco Ravalico,
• Jamie S. T. Sweet,
• Thomas B. Elder,
• Louis P. Conway,
• Marc E. Lennon,
• David R. W. Hodgson and
• Joseph S. Vyle

Beilstein J. Org. Chem. 2017, 13, 87–92, doi:10.3762/bjoc.13.11

• efficient and reproducible reaction of the nucleoside substrates with MobSeH was not achieved in a ball mill. We therefore moved to investigate displacements using potassium selenocyanate which is commercially available, less sensitive to oxidation, and is known to react selectively at selenium in reactions

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• : carbohydrate chemistry; fucose; lectin; selenoglycoside; Introduction Since the discovery of seleno mercaptan by Siemens in 1847 [1], organoselenium compounds have attracted high attention. Besides their biological and pharmaceutical relevance, e.g., selenocysteine or ebselen [2][3][4][5], selenium-containing

• -glucosamine, have been described in rats as metabolites for detoxifying inorganic selenite intake [12][13]. Selenium-containing compounds are also widely used as tools for protein X-ray crystallography in structural biology. The determination of a protein structure depends on the correct phase recovering

• enable the localization of heavy metal positions and hence determination of the phases [14][15]. Covalently modified detergents, for example selenium-containing alkyl glycosides, have been used to incorporate heavy atoms into the crystal [16][17][18]. To overcome problems in locating numerous rather

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• that the intersystem-crossing efficiency of squaraines can be remarkably increased by incorporation of heavy atoms like selenium or sulfur and the addition of long aliphatic side chains [20][21]. The enhanced intersystem-crossing efficacy due to spin-orbital interactions makes modified squaraines a

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• ), 474.0584 [M(35Cl)+] (calcd 474.0581), 476.0581 [M(37Cl)+] (calcd 476.0552). Synthesis of 2,10-di-tert-butyldipyrido[1,2-c:2′,1′-e]imidazolin-6-selenone (4b). A suspension of 2,10-di-tert-butyldipyrido[1,2-c:2′,1′-e]imidazolium tetrafluoroborate [41] (40.5 mg, 110 μmol) and selenium (32.1 mg, 407 μmol) in 3

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

• of oxidizing systems such as H2O2/aryl benzyl selenoxide and H2O2/diaryl diselenide is similar to that of m-chloroperbenzoic acid [212][232][233]. The main advantage of these selenium-containing systems is that the catalysts are regenerated and can therefore be used at low loadings [234][235][236

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

• as the presence of an o-halogen, an o-selenium, or an o-xanthate, respectively. One of the direct approaches to 2-oxindoles could be a one-electron oxidation of an amide enolate as shown in Scheme 1. Toward this end, in 2009, Kündig and co-workers have developed a novel route to 3,3-disubstituted-2

Direct estimate of the internal π-donation to the carbene centre within N-heterocyclic carbenes and related molecules

• Diego M. Andrada,
• Nicole Holzmann,
• Thomas Hamadi and
• Gernot Frenking

Beilstein J. Org. Chem. 2015, 11, 2727–2736, doi:10.3762/bjoc.11.294

• -selenium adducts, respectively, to determine the π-acceptor strength of the parent NHCs [64][65]. In the same way, Nolan et al. have applied this technique to a wider range of NHCs and have established the connection between the π-accepting abilities and the NMR chemical shift [66]. Furthermore, different

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• the final products, we deliberately avoided all toxic selenium based reagents [12][13]. We tested several methodologies and the results are summarized in Table 2. In our initial synthesis [9] we applied the hyperiodine chemistry, developed by Nicolaou. However, the o-iodoxybenzoic acid (IBX) mediated

Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

• Biljana M. Šmit,
• Radoslav Z. Pavlović,
• Dejan A. Milenković and
• Zoran S. Marković

Beilstein J. Org. Chem. 2015, 11, 1865–1875, doi:10.3762/bjoc.11.200

• , State University of Novi Pazar, Vuka Karadžića bb, 36300 Novi Pazar, Serbia 10.3762/bjoc.11.200 Abstract The mechanism and selectivity of a bicyclic hydantoin formation by selenium-induced cyclization are investigated. The proposed mechanism involves the intermediates formed by an electrophilic

• addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of

• observations. Results and Discussion We have recently reported a three-step reaction sequence to cis-fused bicyclic hydantoins involving selenium-induced cyclization of 5-alkenylhydantoins as the key step [24]. The reaction is chemo- and regiospecific giving only the five-membered bicyclic hydantoins, 5-exo

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

• systems which are found in streptorubin B and metacycloprodigiosin [148][149][150]. In this context, the cyclooctene 164 was reacted with the intermediate formed in situ from chloramine-T and elemental selenium [151] and yielded the allylic amine derivative 165 (75%). An N-alkylation with propargyl

Bis(vinylenedithio)tetrathiafulvalene analogues of BEDT-TTF

• Erdal Ertas,
• İlknur Demirtas and
• Turan Ozturk

Beilstein J. Org. Chem. 2015, 11, 403–415, doi:10.3762/bjoc.11.46

• , led to the production of superconducting salts based on TTF type donors containing a heteroatom such as sulfur, selenium, oxygen, etc. [17][18][19][20]. Among a large number of tetrathiafulvalene analogues, bis(ethyleneditiho)tetrathiafulvalene (BEDT-TTF, 3), also known as ET, has been the most