New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• . 4.1 Alkylation of active methylene compounds Hydroalkylation of styrenes, indene and norbornene with 1,3-diketones was firstly reported in 2004 by using AuCl3 and AgOTf in 1:3 ratio as the catalyst (Scheme 15) [51]. The addition took place with Markovnikov selectivity in good yields, however optimal

• conditions suffered from severe limitations on 1,3-diketones as nucleophiles and unfunctionalized olefins. The same catalytic system was then employed with cyclic enols, dienes and trienes although lower yields were recorded [52]. Remarkably, the intramolecular [Au(I)]-catalyzed addition of β-keto amides to

• . Mechanistic proposal for the cooperative [Au(I)]/menthol catalysis for the enantioselective intramolecular hydroamination of dienes. [Au(III)]-catalyzed addition of 1,3-diketones to alkenes. [Au(I)]-catalyzed intramolecular addition of β-keto amides to alkenes. Intermolecular [Au(I)]-catalyzed addition of

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• Yumeng Xi Boliang Dong Xiaodong Shi C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, United States 10.3762/bjoc.9.288 Abstract Gold-catalyzed O-vinylation of cyclic 1,3-diketones has been achieved for the first time, which provides direct

• 1,3-diketones with unactivated alkynes at ambient temperature. Results and Discussion As indicated in Scheme 1, the main challenge for the intermolecular O-nucleophile addition to alkynes is the competitive hydration side reaction. Although, theoretically, strictly anhydrous conditions shall prevent

• , though in low yield. Two regioisomers were isolated, which were assigned as 8a and 8b (Scheme 3A). Diphenylacetylene gave trace amounts of the desired product under the identical conditions. Several diketones were tested to explore the scope of nucleophiles. The 1,3-cyclohexanedione derivative worked

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

• Sudipta Pathak,
• Kamalesh Debnath and
• Animesh Pramanik

Beilstein J. Org. Chem. 2013, 9, 2344–2353, doi:10.3762/bjoc.9.269

• attention of synthetic as well as medicinal chemists [7][8][9]. Various methodologies for the synthesis of isocoumarins have been reported such as the reaction of o-halobenzoic acids and 1,3-diketones through a copper-catalyzed tandem sequential cyclization/addition/deacylation process [10][11], an iridium

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Mechanistic studies on the CAN-mediated intramolecular cyclization of δ-aryl-β-dicarbonyl compounds

• Brian M. Casey,
• Dhandapani V. Sadasivam and
• Robert A. Flowers II

Beilstein J. Org. Chem. 2013, 9, 1472–1479, doi:10.3762/bjoc.9.167

• 73% yield. To examine the breadth of this method, a series of δ-aryl-β-dicarbonyl substrates was prepared by a previously reported procedure [17]. As shown in Table 1, the intramolecular cyclization of δ-aryl-β-diketones with unsubstituted aryl rings (Table 1, entries 1 and 3) afforded 2-tetralone

• oxidation of several β-diketones and their related silyl enol ethers by CAN and the more lipophilic ceric tetra-n-butylammonium nitrate (CTAN) were measured in MeOH, MeCN and CH2Cl2 by using stopped-flow spectrophotometry [16]. In these experiments, initial oxidation of substrates generated radical cation

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

• Mostafa Kiamehr,
• Firouz Matloubi Moghaddam,
• Satenik Mkrtchyan,
• Volodymyr Semeniuchenko,
• Linda Supe,
• Alexander Villinger,
• Peter Langer and
• Viktor O. Iaroshenko

Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124

• pyridinium salts and diketones. Herein we report the results of that study. First, we studied the reaction of pyridinium salt 2a with dimedone (1a) using various bases in different solvents (Table 1). At the same time, different ratios of 1a and 2a were examined. To reach the optimal yields, dimedone and

• afforded the desired products in good to excellent yields. It is worth mentioning that only cyclohexanediones were prone to reaction with the tested pyridinium salts with formation of the corresponding tetracyclic products 3, 4, 6 and 7. In the frame of the current project a variety of 1,3-diketones and

• CF3-containing 1,3-diketones were investigated, but these failed for all mentioned cases. For 3-cyanopyridinium salts a departure from the general trend was observed in terms of reaction conditions regarding the base used; here the highest efficiency was observed for NaHCO3, and the reaction took 4

Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

• Yan Sun,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 8–14, doi:10.3762/bjoc.9.2

• ] derivatives in moderate yields (Scheme 1a) [15]. In order to explore the generality of this four-component reaction, the reactivity of the other cyclic 1,3-diketones was also investigated. In an exploratory experiment, the four-component reaction of p-methoxyaniline, dimethyl acetylenedicarboxylate, 1-benzyl

• of spiro[dihydropyridine-oxindole] 1b. The two kinds of spiro compounds from reactions of isatins with arylamines and cyclic 1,3-diketones. Molecular structure of spiro[dihydropyridine-oxindole] 2f. Molecular structure of compound 3d. The four-component reactions containing dimedone (a) and

Features of the behavior of 4-amino-5-carboxamido-1,2,3-triazole in multicomponent heterocyclizations with carbonyl compounds

• Eugene S. Gladkov,
• Katerina A. Gura,
• Svetlana M. Sirko,
• Sergey M. Desenko,
• Ulrich Groth and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2012, 8, 2100–2105, doi:10.3762/bjoc.8.236

• polyfunctional aminoazoles that have been studied in heterocyclization reactions [5][6][7][8][20], derivatives of 4-amino-1,2,3-triazole have been less well investigated. There are only a few examples of their heterocyclizations with β-diketones [21], N-cyanomethaneimidates [22], isocyanates [23], chalcones [24

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• these preparatively interesting four-membered ring compounds [64]. When an allene carries a hydroxy function, it is, of course, a special type of an enol (an allenol) and as such unstable. Yet, it may be generated as an intermediate to be employed in further transformations. Indeed, when α-diketones

New efficient ligand for sub-mol % copper-catalyzed C–N cross-coupling reactions running under air

• Per-Fredrik Larsson,
• Peter Astvik and
• Per-Ola Norrby

Beilstein J. Org. Chem. 2012, 8, 1909–1915, doi:10.3762/bjoc.8.221

• when using higher catalytic loadings with secondary amine ligands [12][13]. Several classes of ligands have proved efficient in copper-catalyzed cross-coupling reactions, such as phenanthrolines, alpha-amino acids, 1,3-diketones, salicylamides, and imines, but DMEDA is one of the few that works well

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• unsaturated 1,4-diketones catalyzed by thiourea and squaramide derivatives with Cinchona alkaloids afforded the formation of a new C–C bond in high yields (up to 98%) and enantiomeric purities (up to 93%). The absolute configuration of the product was suggested from comparison of the experimental and

• enantioenriched products through a carbon–carbon bond formation [1][2][3][4][5]. Recently, unsaturated 1,4-dicarbonyl compounds, such as 1,4-ketoesters [6][7][8], 1,4-diketones [9], 1,4-ketoamides [9][10] and dialkylfumarates [11], have been the substrates for this reaction. The reaction products can undergo

• addition of dialkylmalonates and nitromethane to 4-oxo-4-arylbutenoates catalyzed by N,N´-dioxide-Sc(OTf)3 complexes [8]. Despite these and other successful experimental results, the asymmetric addition of malonates to symmetric aromatic unsaturated 1,4-diketones has not been systematically studied

Screening of ligands for the Ullmann synthesis of electron-rich diaryl ethers

• Nicola Otto and
• Till Opatz

Beilstein J. Org. Chem. 2012, 8, 1105–1111, doi:10.3762/bjoc.8.122

• , phosphinites, phosphonates, imines, diimines, oximes, oxime ethers and diketones were selected for the screening (Figure 2). Several of these compounds have been employed in diaryl ether syntheses before [22][23][24]. As a starting point, N,N-dimethylglycine (L1) introduced by Ma et al. [22][25] in combination

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

• functionalised with furan heterocycles are reviewed. The methodologies used to prepare such compounds include the ring closure of 1,5-diketones and cross-coupling reactions. These versatile terpyridines and their derived metal complexes find applications in various fields including coordination chemistry

• describes the state of the art concerning preparation and applications of such terpyridines bearing a furanyl ring. Review Synthesis by ring closure of 1,5-diketones In 1976, Kröhnke introduced a synthetic methodology to prepare pyridine derivatives that relies on the ring closure of 1,5-diketo-derivatives

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

• Katharina C. Kress,
• Martin Kaller,
• Kirill V. Axenov,
• Stefan Tussetschläger and
• Sabine Laschat

Beilstein J. Org. Chem. 2012, 8, 371–378, doi:10.3762/bjoc.8.40

• complex 2 described by Haase [17][18][19][20][21]. In contrast to the various diketonato metallomesogens only a little information is available about the mesomorphic properties of metal-free diketones. Among the few examples are the nematic compounds 3 [22] and 4 [23][24] (Scheme 1). The corresponding

• patterns of 11a: (A) crystalline phase at 50 °C, (B) isotropic phase at 25 °C, and (C) nematic phase at 15 °C. Diketonato metallomesogens and diketones with mesomorphic properties. Malonates and cyanoacetates tethered to calamitic 4-cyanobiphenyl units. Synthesis of malonate and cyanoacetates tethered to 4

Organic synthesis using (diacetoxyiodo)benzene (DIB): Unexpected and novel oxidation of 3-oxo-butanamides to 2,2-dihalo-N-phenylacetamides

• Wei-Bing Liu,
• Cui Chen,
• Qing Zhang and
• Zhi-Bo Zhu

Beilstein J. Org. Chem. 2012, 8, 344–348, doi:10.3762/bjoc.8.38

• acids can activate 1,3-diketones [40] to produce intermediate 5 and 6. This complexation not only increases the nucleophilicity of the methylene carbon atom, but also simultaneously increases the electrophilicity of the carbonyl carbon atom. Consequently, nucleophilic attack of the acetate ion on the

Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

• Branislav Husár,
• Norbert Moszner and
• Ivan Lukáč

Beilstein J. Org. Chem. 2012, 8, 337–343, doi:10.3762/bjoc.8.37

• CQ photooxidation in PS are summarized in Scheme 3 [21]. The addition of molecular oxygen to the excited n→π* triplet state of ketones and 1,2-diketones to form 1,4-biradicals is a generally accepted mechanism, which has been theoretically treated and reviewed [37]. The oxygen atom released during

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• application of such organic materials are described. Metal complexes and metal sensitizers are not covered in this review. Review Synthesis of imidazole-derived chromophores A condensation of α-diketones and aldehydes in the presence of ammonia or ammonium salts (Debus–Radziszewski synthesis) is one of the

Regioselectivity in the multicomponent reaction of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal under controlled microwave heating

• Kamal Usef Sadek,
• Ramadan Ahmed Mekheimer,
• Tahany Mahmoud Mohamed,
• Moustafa Sherief Moustafa and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2012, 8, 18–24, doi:10.3762/bjoc.8.3

• investigation concerning the regioselectivity in multicomponent reactions of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal (DMFDMA) under controlled microwave heating. We began this study by treating 5-amino-3-methylpyrazole (1a) and dimedone (2a) with DMFDMA (3) in DMF under

• single-crystal X-ray diffraction [25][26] (Figure 1, Figure 2 and Table 1, Table 2, Table 3). With this result in hand, we went on to study the scope of such multicomponent reactions with several substituted 5-aminopyrazoles and cyclic 1,3-diketones. Thus, the reaction of 1b–f with 2a,b and 3, under the

• established by single-crystal X-ray diffraction of compounds 6e,g (Figure 3, Figure 4 and Table 3, Table 4) [27][28]. A proposed mechanism to account for the formation of products 6 is illustrated in Scheme 2. The base-catalyzed reaction of cyclic 1,3-diketones 2 with DMFDMA 3 gave the enaminone 7, which

Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones

• Anne T. Hylden,
• Eric J. Uzelac,
• Zeljko Ostojic,
• Ting-Ting Wu,
• Keely L. Sacry,
• Krista L. Sacry,
• Lin Xi and
• T. Nicholas Jones

Beilstein J. Org. Chem. 2011, 7, 1323–1326, doi:10.3762/bjoc.7.155

• trifluoroacetic anhydride followed by decomposition of the reaction mixture in methanol under reflux yielded 1,3-cyclohexandione in 25% yield. Later, Smit and coworkers reported the closely related acyclic reaction between alkynes and acyl cations leading to β-diketones in 25–76% yield [8][9]. Interestingly, only

Continuous gas/liquid–liquid/liquid flow synthesis of 4-fluoropyrazole derivatives by selective direct fluorination

• Jessica R. Breen,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• Jonathan Fray and
• Bhairavi Patel

Beilstein J. Org. Chem. 2011, 7, 1048–1054, doi:10.3762/bjoc.7.120

• -diketones and hydrazines [23]. However, the synthetic methodology for the preparation of the corresponding fluoropyrazole derivatives has not been developed to any great extent despite the potential use of such systems in life science applications. Recently, we explored direct fluorination of various

• of fluoropyrazole systems and, in this paper, we demonstrate that fluorination of diketones to corresponding fluorodiketones, followed by sequential cyclization to the appropriate fluoropyrazoles upon reaction with a hydrazine derivative, can be accomplished in a single, two-step, telescoped, gas

• derivatives were synthesised by sequential direct fluorination of appropriate 1,3-diketones and subsequent cyclisation of the in situ generated fluorodiketone with a hydrazine derivative. This represents the first example of a sequential, continuous flow gas/liquid–liquid/liquid process involving direct

Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• to form α-diketones and aldehydes in good yields is presented. Further directed synthesis of quinoxalines and benzimidazoles, via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine, was achieved in high yields. Keywords: allene; benzimidazole; gold-catalysis

• /hydration and oxidative cleavage of allenes to form α-diketones and aldehydes, and the synthesis of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine [45][46][47][48][49][50][51][52][53][54][55][56]. Results and Discussion Our initial

• oxidative transformation under the same reaction conditions. Having prepared a variety of α-diketones and aldehydes successfully, we then undertook the synthesis of quinoxalines and benzimidazoles (Scheme 2). Thus, the treatment of the corresponding mixture of α-diketone 2 and aldehyde 3 with benzene-1,2

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• labeling experiment was designed to elucidate the pathway responsible for the gold-catalyzed intramolecular oxygen transfer of 2-alkynyl-1,5-diketones (Scheme 8). By introducing an 18O atom into one of the carbonyls of the substrate, and using the 13C NMR spectra of the substrate and product to locate the

• transfer of 2-alkynyl-1,5-diketones. The discovery of a [4 + 2] cycloaddition of a furanium intermediate to a carbonyl group was further verified by quantum chemical calculations. The competing [2 + 2] and [4 + 2] reaction coordinates were computed for the simplified substrate 11a, shown in Scheme 10. In

• [4 + 2] pathway over the [2 + 2] pathway supports the postulate that the [4 + 2] pathway is dominant in the gold-catalyzed oxygen transfer of 2-alkynyl-1,5-diketones, which is exactly in accordance with the 18O isotopic experiments. Chan and co-workers developed a gold-catalyzed tandem intramolecular

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• -1,4-diketones after hydrolysis of the primary photochemical products (photo aldol reaction) [7], whilst the reaction of oxazoles with carbonyl compounds is a convenient protocol for the stereoselective synthesis of α-amino β-hydroxy ketones [8][9] as well as highly substituted α-amino β-hydroxy acids

• corresponding 1,3-diketones [13] or deaminated to yield Michael systems [14]. Thus, isoxazoles also appear to be important substrates for carbonyl–ene photocycloaddition due to possible applications in ring-opening transformations. Results and Discussion Synthesis of the isoxazole substrates The substrates

Syntheses and properties of thienyl-substituted dithienophenazines

• Annemarie Meyer,
• Eva Sigmund,
• Friedhelm Luppertz,
• Gregor Schnakenburg,
• Immanuel Gadaczek,
• Thomas Bredow,
• Stefan-S. Jester and
• Sigurd Höger

Beilstein J. Org. Chem. 2010, 6, 1180–1187, doi:10.3762/bjoc.6.135

• oxalyl chloride [23][24]. Bromination of 7 with NBS failed, however, the reaction with bromine under similar conditions as described for 4 afforded 8 in quantitative yields. Both routes towards the brominated bithiophene-diketones gave high overall yields and can be scaled up easily. Condensation of the

• diketones 4 and 8 with diaminobenzenes 9a and 9b, containing methyl and hexyl side groups [25], in pure acetic acid at 50 °C gave the phenazines 10 and 11 as yellow solids in 50–93% yield (Scheme 3) [26]. The hexyl derivatives 10b and 11b showed a significantly higher solubility than the methyl analogues

Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

• Kerstin Schmidt and
• Paul Margaretha

Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

• room temperature. The org. phase was washed with sat. aq NaCl, dried (MgSO4) and the residue (100% conversion to product from 1H NMR) purified by CC (SiO2, pentane/Et2O 1:1) to afford the diketones 3. 1-Butyl-2a,8b-dihydrocyclobuta[a]naphthalene-3,4-dione (3a): 37 mg (85%), viscous yellow oil, Rf