Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• (59a) (X = NH) [92], the N-methyl-4-hydroxy-6-methylpyridin-2(1H)-one (59b) (X = NMe) [92], N-ethyl-4-hydroxy-6-methylpyridin-2(1H)-one (59c) (X = NEt) [92], 4-hydroxy-6-methyl-2H-pyran-2-one (59d) (X = O) [92], or cyclohexane-1,3-dione (60) [93]. The syntheses of derivatives 61 to 64 represent a

C–H-Functionalization logic guides the synthesis of a carbacyclopamine analog

• Sebastian Rabe,
• Johann Moschner,
• Marina Bantzi,
• Philipp Heretsch and
• Athanassios Giannis

Beilstein J. Org. Chem. 2014, 10, 1564–1569, doi:10.3762/bjoc.10.161

• tetrahydropyranyl ether (3,4-dihydro-2H-pyran, cat. pyridinium para-toluenesulfonate, CH2Cl2, 25 °C, quantiative, inconsequential mixture of diastereoisomers), and the C17 carbonyl group was transformed into its 2-picolylimine (2-picolylamine, cat. para-toluenesulfonic acid, toluene, 111 °C, 92% yield). Subjecting

Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• -dicyanomethylene-2-tert-butyl-6-(p-dialkylaminostyryl)-4H-pyran) [3] with a photochromic diarylethene (DAE) which showed a photoreversible two-way FRET controlled by the state of the photochromic moiety, and 49% quenching of the fluorescence upon UV irradiation [4]. Bifunctional molecules built on two distinct

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

• Dominik Lenhart and
• Thorsten Bach

Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86

• . With 5,6-dihydro-2H-pyran-2-one (12) two major products 13 and 14 could be isolated (Scheme 3). If performed in CH2Cl2 the reaction remained incomplete after 24 hours. The substrate was recovered in 20% and products 13 and 14 were obtained in a ratio of 55/45 with the tricyclic product prevailing. A

• higher type selectivity. The domino process was suppressed and the plain addition product 22 was obtained in 75% yield (Scheme 7). The latter result suggested that the previously discussed (Scheme 3) addition reaction to 5,6-dihydro-2H-pyran-2-one (12) might also lead to a single product if performed

• -dihydro-2H-pyran-2-one (12). Ir-catalyzed addition reactions of N-methyl-N-((trimethylsilyl)methyl)aniline (5) to 2-cyclopentenone (15). Ir-catalyzed formation of tricyclic products 19 by a domino radical addition reaction to α,β-unsaturated lactams 18. Ir-catalyzed addition reactions of N-methyl-N

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• presence of Yb(fod)3 to afford 2-alkoxy-3,4-dihydro-5-vinyl-2H-pyran 33. In the presence of electron-poor dienophiles, as N-phenylmaleimide, maleic anhydride, activated azo compounds or naphthoquinone, 33 underwent normal Diels–Alder reactions thus giving the corresponding cycloadducts 34 as single

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• have the drawbacks of carbohydrates such as low binding affinity or instability [4][5]. Many carbohydrates and their mimetics contain pyran rings, however, the corresponding ring-expanded compounds, oxepanes, have been investigated only in a limited number of studies. Several oxepane units can be found

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

• , P.O. Box 83523, Qena, Egypt 10.3762/bjoc.10.11 Abstract Novel routes for the preparation of 2-amino-4H-pyran-3-carbonitrile 9, amino-arylbenzoic acid ester derivatives 13a,b, 2-aminotetrahydro-4H-chromene-3-carbonitrile 18, 3-amino-4-cyanotetrahydronaphthalene-2-carboxylic acid ester 26 and 4-amino

• -pyran 9 and that the yield of the process can be improved if equimolar amounts of DMADC, benzylidenemalononitrile and malononitrile are used [20]. Similar observations have been made in previous studies of these reactions using 1-methylimidazole [21]. Recently we observed that 2-amino-4H-pyran 9 can be

• generate 10 that cyclizes to form 12. Subsequent aromatization of 12 produces the benzoate derivative 13b. Alternatively, 8 could react with malononitrile to yield 11 that then serve as a precursor to 13 (Scheme 4). In support of the former mechanistic proposal, it was observed that 2-amino-4H-pyran 9

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• , Lucknow-226001, India 10.3762/bjoc.9.92 Abstract A direct one-pot base-induced alkenylation of indolin-2-ones has been developed by using 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles. Different bases such as MeONa, NaH and t-BuONa have been used to optimize the reaction conditions to obtain the

• ; 2H-pyran-2-one; Introduction 6-Aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles have emerged as versatile synthons for the construction of an array of arenes and heteroarenes through base-induced ring transformation by nitrogen, sulfur and carbon nucleophiles [1]. However, suitably functionalized 2H

• -pyran-2-ones have not been investigated for the alkenylation of indolin-2-ones. An extensive literature survey on the pharmacological properties of 3-alkenylindolin-2-ones revealed that they possess potent antitumor [2][3][4][5], antipyretic [6], antifungal [7][8], anti-inflammatory [9], and analgesic

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• . Grant et al., found the trans-fused (1R,4aS,7R,7aR)-1-methoxy-4,7-dimethyl-1,4a,5,6,7,7a)-hexahydrocyclopenta[c]pyran, called (1R)-1-methoxymyodesert-3-ene, among the volatiles of the Ellangowan poison bush, which they transformed to the corresponding lactone a' [24]. Apart from this compound and very

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• glycals using several aromatic and aliphatic alkynes. This Pd-catalyzed cross-coupling reaction presents a facile access to alkynyl C-glycosides and sets the stage for a reductive/oxidative refunctionalization of the enyne moiety to regenerate either C-glycosidic structures or pyran derivatives with a

• also the sterically encumbered TIPS groups render the reduction of the olefinic moiety much more difficult. In contrast to the other enynes the carbohydrate derivative 11a was fully reduced in a diastereoselective manner and in excellent yield to the pyran 14d by employing Pearlman’s catalyst (rt

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• [58], and pyran derivatives [59]. Gratifyingly, the treatment of tetrahydro-2H-1,2-oxazine derivatives 12 and 13 with an excess of SmI2 in tetrahydrofuran smoothly provided the expected amino alcohols 16 and 17 in excellent yields (Scheme 5). In order to compare the behaviour of a compound still

A concise synthesis of 3-(1-alkenyl)isoindolin-1-ones and 5-(1-alkenyl)pyrrol-2-ones by the intermolecular coupling reactions of N-acyliminium ions with unactivated olefins

• Nianhong Lu,
• Lihong Wang,
• Zhanshan Li and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 192–200, doi:10.3762/bjoc.8.21

• −1, 2θmax = 51°, 9126 reflections measured, 3995 unique (Rint = 0.0696), which were used in all calculations. The final wR(F2) was 0.1427 (for all data), R1 = 0.0764. CCDC file No. 835330. 3-(3,4-Dihydro-2H-pyran-5-yl)-2-methylisoindolin-1-one (3k): Colorless solid, mp 94–97 °C; 1H NMR (400 MHz

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• and H4a are antiperiplanar to H1, H3 and H5. All these findings confirm that the pyran ring takes a chair conformation, where the substituents at C1, C3 and C5 are present in equatorial position. The tosyl group at C4 got easily deprotected at room temperature with Mg–MeOH (Scheme 3) [42] to afford

Multicomponent reaction access to complex quinolines via oxidation of the Povarov adducts

• Esther Vicente-García,
• Rosario Ramón,
• Sara Preciado and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2011, 7, 980–987, doi:10.3762/bjoc.7.110

• quinolines 21 in high yields, and the elimination product 22 was not detected. The processes were slower (5–8 h) than those involving the pyran-fused substrates 17,17' (Scheme 3). Interestingly, although DDQ is also capable of promoting these transformations, it is not as selective as Wako MnO2, and apart

Homoallylic amines by reductive inter- and intramolecular coupling of allenes and nitriles

• Peter Wipf and
• Marija D. Manojlovic

Beilstein J. Org. Chem. 2011, 7, 824–830, doi:10.3762/bjoc.7.94

• temperature improved the reaction workup and provided compound 23 in 60% yield. In order to determine the relative configuration of pyran 21, the amine was protected as the t-butyl carbamate (Supporting Information File 1). Signals for both hydrogen atoms Hb and Hc were doublets of doublets with one large and

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• malonate diesters, while tetrahydropyrans 3c and 3d were obtained from tetrahydro-4H-pyran-4-one. The advantages and disadvantages of each route are discussed. Dibromides 1c and 1d were used to prepare sulfonium zwitterions 11c and 11d. Keywords: 1,5-dibromopentanes; heterocycles; methodology; synthesis

• addition of a Grignard reagent to tetrahydro-4H-pyran-4-one, elimination of water, and hydrogenation of the olefin (Method 2A). Typical yields for Method 2A range from 20–30% [39][40]. The second route is the Wittig olefination of tetrahydro-4H-pyran-4-one followed by hydrogenation (Method 2B). Yields for

• the Wittig olefination of tetrahydro-4H-pyran-4-one range from 35–75% [41][42][43]. The third route (Method 2C) begins from tetrahydropyran-4-carboxylic acid: The acid chloride is reacted with a Grignard reagent, and the resulting ketone reduced under Wolff–Kischner conditions. Typical yields for this

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• , found 174.0689; Anal. calcd for C11H10O2: C, 75.8, H, 5.8; found: C, 75.6, H, 5.8. Procedure for the synthesis of (R)-2-((2R,3R)-3-(tert-butyldimethylsilyloxy)-6-oxo-3,6-dihydro-2H-pyran-2-yl)-2-hydroxyethyl benzoate (4g): The acrylate 3g (330 mg, 0.78 mmol) and phenol (37 mg, 0.39 mmol) were dissolved

• '-(ethene-1,2-diyl)bis(5-(prop-1-en-2-yl)-3,6-dihydro-2H-pyran-3-ol (7b): [α]D25: –390.0 (c 0.13, CH2Cl2); 1H NMR (300 MHz, CDCl) δ 6.05 (d, J = 5.4, 2H); 5.96 (d, J = 1.7, 2H); 4.93 (s, 1H); 4.83 (s, 2H); 4.49 (d, J = 15.6, 2H); 4.25 (d, J = 15.5, 2H); 4.04 (s, 2H); 3.99 (d, J = 5.5, 1H); 3.32 (s, 2H

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• to a tricarboxylic acid core. Keywords: aminopyrans; carbohydrate mimetics; Lewis acids; lithiated enol ethers; nitrones; oxidative cleavage; stereodivergent synthesis; Introduction The pyran structural motif can be found in numerous bioactive natural products. Possible strategies towards their

• stabilized carbenium ion 6 (Scheme 3). Subsequent attack of the oxocarbenium ion on the enol ether moiety leads to ring closure affording the cationic pyran intermediate 7. Subsequent proton transfer to the (moderately basic) hydroxylamine nitrogen re-establishes the enol ether moiety. During aqueous work-up

•  10). Sodium azide presumably acts as base to initiate the reaction by deprotonation of the hydroxylamine moiety. A hydride shift from the benzylic position to the 3-position of the pyran ring produces the nitrone moiety of 21 and simultaneously displaces the axially positioned bromo substituent by an

Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

• Guillaume G. Launay,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

• noted separately by Jaber et al. [12] and subsequently by Kataoka et al. [13]. For example, homoallylic alcohol 1 was converted to pyran 2 with a high diastereoselectivity (Scheme 1) [12]. Most recently, oxa-, aza- and thia-Prins fluorination cyclisations have been carried out using ionic liquid

• the Prins fluorination products, pyran 5m was subjected to hydrogenolysis [23] as illustrated in Scheme 2. This resulted in the efficient conversion to the corresponding open chain compound 3-fluoro-5-phenylpentyl acetate (7). The structural diversity of the Prins fluorination reaction was extended

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• investigations have demonstrated that incorporation of SAAs in peptide structures can circumvent the adverse properties of bioactive natural systems. Thus, SAAs containing amino and carboxylic functional groups, and a rigid ring system (pyran, furan, oxetane) have emerged as versatile and conformationally

Pd/C-mediated synthesis of α-pyrone fused with a five-membered nitrogen heteroaryl ring: A new route to pyrano[4,3-c]pyrazol-4(1H)-ones

• Dhilli Rao Gorja,
• Venkateswara Rao Batchu,
• Ashok Ettam and
• Manojit Pal

Beilstein J. Org. Chem. 2009, 5, No. 64, doi:10.3762/bjoc.5.64

• ] (or 2H-pyran-2-one) and their benzo derivatives, e.g. isocoumarins [3], have shown a wide range of pharmacological activities [4][5][6] such as antifungal, antimicrobial, phytotoxic and other effects. On the other hand α-pyrones fused with a five-membered heteroaryl ring, e.g. thienopyranones, have

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• generates a flexible C3–C4 single bond within the open merocyanine forms in place of the former double bond of the pyran ring (Scheme 1), resulting in a significant structural alteration of the β-turn scaffold. Herein we describe the synthesis of functionalized photochromic pyrans by palladium-catalyzed

• The starting materials, propargyl alcohol 9 and the phenol 8b, were prepared essentially by following literature procedures (Scheme 3). Synthesis of the pyran precursors 10 and 12a/b was accomplished by using PPTS and trimethyl orthoformate in DCE in a standard protocol developed by Carreira [27] for

• in good to excellent yields (Scheme 6). Starting from the bromo-substituted pyran 2b a final carbonylation step (Scheme 6) would directly complete the synthesis of an Fmoc-protected ω-amino acid. Though many protocols for Heck carbonylations are known, only a few report neutral reaction conditions

A short stereoselective synthesis of (+)-(6R,2′S)-cryptocaryalactone via ring- closing metathesis

• Palakodety Radha Krishna,
• Krishnarao Lopinti and
• K. L. N. Reddy

Beilstein J. Org. Chem. 2009, 5, No. 14, doi:10.3762/bjoc.5.14

• the sub-classes of these 5,6-dihydro-2H-pyran-2-one compounds is the styryl lactones which possess a styryl moiety side chain. The styryl moiety of goniothalamin has been shown to be of importance for its cytotoxic effect on different cancer cells as well as its antimicrobial, larvicidal activity and

• also isolated from C. bourdilloni, C. moschata and C. myrtifolia and their absolute configuration was established [34]. These cryptocaryalactones are natural germination inhibitors with no effect on corn [35]. We were interested in synthesizing natural products containing 5,6-dihydro-2H-pyran-2-one