Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• 10.3762/bjoc.8.42 Abstract The synthesis of a heterocyclic mesomeric betaine by quaternization reaction of 1-butylimidazole and tetrabromo-1,4-benzoquinone is presented. The structure was verified by means of X-ray single-crystal analysis, NMR and IR spectroscopy. Inclusion complexes of the heterocyclic

• -bezoquinone to obtain novel mesomeric betaine materials with imidazolium-enolate structure. Results and Discussion The quaternization of 1-butylimidazole (2) with tetrabromo-1,4-benzoquinone (p-bromanil (1)) in acetonitrile and the subsequent quenching of the reaction mixture with water yielded dipole 2,3

• -dibromo-5-(1-butyl-1H-imidazol-3-ium-3-yl)-1,4-benzoquinone-6-olate (3) instead of the quadrupole compound (Scheme 1). Model compound 3 was dark red, solid, and soluble in chloroform, dichloromethane, and DMSO, but insoluble in water, acetone and toluene. The formation of 3 was confirmed by means of NMR

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• dihydropyridine 32. The latter undergoes aromatization upon reaction with benzoquinone to afford 33 (Scheme 6). Synthesis by cross-coupling reaction Cross-coupling reactions are widely used in organic chemistry [32] to create new C–C bonds. The importance of this technique was recently highlighted by the award of

Efficient synthesis of 1,3-diaryl-4-halo-1H-pyrazoles from 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes

• Yiwen Yang,
• Chunxiang Kuang,
• Hui Jin,
• Qing Yang and
• Zhongkui Zhang

Beilstein J. Org. Chem. 2011, 7, 1656–1662, doi:10.3762/bjoc.7.195

• -dearylation followed by the generation of the parent NH-pyrazole and p-benzoquinone [37]. Conclusion In summary, a series of novel 1,3-diaryl-4-halo-1H-pyrazoles was synthesized in moderate to excellent yields by using 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes in the presence of the mild base Cs2CO3. The

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

• aromatic species. The literature contains scattered reports of the use of oxidants for this transformation: 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), ceric ammonium nitrate (CAN), nitrobenzene, elemental sulfur, palladium and manganese dioxide among others, all of them far from being ideally suited

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

• hydride traps. Satisfactory results in RCM were, however, obtained from 78: in the presence of the 2nd-generation Grubbs catalyst 5 and benzoquinone in refluxing toluene, 78 was converted into the cyclized enol ether 79 in 70% yield, while with the Hoveyda–Grubbs catalyst (6, 10 mol %; benzoquinone 10 mol

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• method employs benzoquinone derivatives instead of azodicarboxylates as the oxidising agent. A series of phosphinites 31 was prepared by treatment of alcohols 30 with chlorodiphenylphosphine in the presence of triethylamine and DMAP. SN2 substitution of the phosphinites proceeds by oxidative activation

• of the leaving group with a 1,4-benzoquinone derivative, DBBQ (35) being most effective (Scheme 12). Addition of a thiol nucleophile to adduct 32 results in SN2 inversion and isolation of the enantiomerically pure (94:6–99:1 er) tertiary thioether 33 and by-product 34. Highest yields were obtained

• to give 39 in 95% yield (Scheme 13). The methodology was later refined to allow substitution of alcohols in 1 step. Phenoxydiphenylphosphine was used to prepare the phosphinite intermediate and an azide was used as the oxidising agent instead of a benzoquinone derivative (Scheme 14) [35][36][37

Predicting the UV–vis spectra of oxazine dyes

• Scott Fleming,
• Andrew Mills and
• Tell Tuttle

Beilstein J. Org. Chem. 2011, 7, 432–441, doi:10.3762/bjoc.7.56

• ; oxazine; TD-DFT; UV–vis; Introduction Oxazine dyes are a subclass of quinone imines, which are all based upon the p-benzoquinone imine or -diimine scaffold. Other important subclasses within the quinone imines include, the azine dyes and thiazine dyes. The structural relationships described are

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• homopentaprismane, somewhat analogous to the original cubane synthesis. As shown in Scheme 7, Diels–Alder reaction of 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene with p-benzoquinone gave 37 which underwent photolytic [2 + 2] closure to the pentacyclic dione 38. Subsequent dechlorination and functional group

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• activity of the catalyst. Furthermore, Johnson and coworkers reported that during a RCM to make a 9-membered ring, chlorinated solvents, such as 1,2-dichloroethane, inhibited olefin isomerization [25]. Grubbs and collaborators showed that catalytic amounts (10 mol %) of 1,4-benzoquinone (BQ) can prevent

• expected in the future. Experimental Materials 10-undecenoic acid (Sigma–Aldrich, 98%), 1,3-propanediol (Sigma–Aldrich, 99.6%), p-toluenesulfonic acid monohydrate (Sigma–Aldrich, 98.5%), ethyl vinyl ether (Sigma–Aldrich, 99%), sulfuric acid (Fluka, 95–97%), p-benzoquinone (Fluka, 98%), (1,3-bis(2,4,6

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

• results only in the formation of a chlorohydroquinone pyridinium species [72], and neutral conditions are required in this case [69]. For the synthesis of poly(SCF3) substituted p-hydroquinones, Scribner oxidized 2,6-bis(SCF3)-4-methoxyphenol to generate 2,6-bis(SCF3)-1,4-benzoquinone. The addition of

Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

• Satoru Arimitsu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2010, 6, No. 48, doi:10.3762/bjoc.6.48

• experimentation, it became clear that ethylene gas was crucial for driving this reaction forward (compare entry 4 with 7, Table 1) [21]. 2,6-Dichloro-1,4-benzoquinone, which has been reported to prevent isomerization [22], gave disappointing results (entry 8, Table 1). When our optimized conditions were applied

Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF₂

• Lukas J. Gooßen,
• Bettina Zimmermann and
• Thomas Knauber

Beilstein J. Org. Chem. 2010, 6, No. 43, doi:10.3762/bjoc.6.43

• acids is disclosed. In the presence of a catalyst system generated in situ from Pd(OAc)2 (2 mol %), CuF2 (2 equiv), and benzoquinone (0.5 equiv) in NMP, a wide range of olefins were coupled with various 2-nitrobenzoates at 130 °C with the release of carbon dioxide to afford the corresponding vinyl

• , in which p-benzoquinone is employed as oxidant [24]. However, their protocol is strictly limited to highly activated benzoates. We herein disclose an alternative protocol for the Pd-catalyzed decarboxylative Heck reaction, in which copper(II) fluoride is utilized as the oxidant. This way, various

• oxidants in an attempt to prevent the formation of palladium(0) species, which we assumed to be catalytically inactive in this process. This proved to be a good strategy, as the addition of p-benzoquinone resulted in higher yields of the Heck product, while at the same time suppressing the formation of the

Microwave assisted synthesis of triazoloquinazolinones and benzimidazoquinazolinones

• Aboul-Fetouh E. Mourad,
• Ashraf A. Aly,
• Hassan H. Farag and
• Eman A. Beshr

Beilstein J. Org. Chem. 2007, 3, No. 11, doi:10.1186/1860-5397-3-11

• δ = 28.4 and 26.8 ppm could be assigned to the two methyl carbons (see Supporting Information File 1 for full experimental data). To test the reactivity of compounds 4a-c towards oxidation, we refluxed a mixture of 2,3,5,6-tetrachloro-1,4-benzoquinone (5) and 4a-c in cholorobenzene (Scheme 2). The

Variations in product in reactions of naphthoquinone with primary amines

• Marjit W. Singh,
• Anirban Karmakar,
• Nilotpal Barooah and
• Jubaraj B. Baruah

Beilstein J. Org. Chem. 2007, 3, No. 10, doi:10.1186/1860-5397-3-10

• -benzoquinone reacts with primary amines to give 2,5-diamino 1,4-benzoquinones; similar reaction of 1,4-naphthoquinone with primary amines results in the formation of 2-amino 1,4-naphthoquinones. [13] However, the product formed from such simple reaction of amine with various quinones has much scope for

• formation of products 1 and 2 is interesting as in the case of 1,4-benzoquinone and 1,4-naphthoquinone we did not observe condensation reaction between either of the carbonyl group with amines under ambient conditions (for experimental please see Supporting Information File 1). It was earlier reported in

• progress to establish this. However, at the moment we have evidence that in the reaction between 4-amino-phenol and 1,4-benzoquinone, 1,4-dihydroxybenzene is formed as side product. This suggests involvement of 1,4-benzoquinone in aromatisation by abstracting hydrogen during product formation. In view of

Photosonochemical catalytic ring opening of α-epoxyketones

• Hamid R. Memarian and
• Ali Saffar-Teluri

Beilstein J. Org. Chem. 2007, 3, No. 2, doi:10.1186/1860-5397-3-2

• and α-epoxyketones have also occurred thermally or photochemically by the presence of various electron acceptors. These reactions have been observed thermally by ceric ammonium nitrate (CAN), [28][29] 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) [30] and iron(III) chloride [31] or photo-induced

Effect of transannular interaction on the redox- potentials in a series of bicyclic quinones

• Grigoriy Sereda,
• Jesse Van Heukelom,
• Miles Koppang,
• Sudha Ramreddy and
• Nicole Collins

Beilstein J. Org. Chem. 2006, 2, No. 26, doi:10.1186/1860-5397-2-26

• (Epox) where (Eo' = 1/2(Epred + Epox) [11]. In order to check our process, we measured the first reduction potential of p-benzoquinone to be -0.507 V, which is exactly the same as the value reported in the literature [3]. The cyclic voltammograms (CV) for p-benzoquinone and the quinone 3 are presented

• compounds 1–5 vs. their calculated LUMO+1 energies. LUMO of Compound 1. LUMO+1 of Compound 1. LUMO of Compound 2. LUMO+1 of Compound 2. LUMO of Compound 4. LUMO+1 of Compound 4. LUMO of Compound 5. LUMO+1 of Compound 5. LUMO of the reduced species 5·−. CV for p-benzoquinone and quinone 3. Cyclic Voltammetry

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• - and p-benzoquinone where the difference in the redox potential is 0.07 V [11] corresponding to 3 kcal mol-1. It may also be relevant that quinones are subject to attack by the hydroxyl ion to form (eventually) humic acids and that o-quinones are more reactive than p-quinones. [12][13] An analogous