Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• heterogeneous continuous-flow procedure for the polarity reversal of aromatic α-diketones is presented. Propaedeutic batch experiments have been initially performed to select the optimal supported base capable to initiate the two electron-transfer process from the carbamoyl anion of the N,N-dimethylformamide

• examples, α-hydroxy ketones (benzoin reaction) and 1,4-diketones (Stetter reaction) [1][2][3][4]. The synthetic utility of the umpolung methodology has therefore spurred intensive research on process intensification through the heterogeneization of NHC catalysts [5][6][7][8][9] for facilitating the post

• -unsaturated acceptors [27][28][29]. Indeed, activation of aromatic α-diketones may occur through a double electron-transfer (ET) process triggered by the carbamoyl anion derived from N,N-dimethylformamide (DMF) solvent with catalytic base, which generates an enediolate anion as key reactive species of

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• traditional way this heterocycle is synthesized from urea, aldehydes, and 1,3-diketones. The method described in this work is quite general and can be applied to any monocyclic structure. The Supporting Information contains an atlas of target bond dissection maps applied to 27 kinds of heterocyclic structures

• 1,3-diketones, urea, and aldehydes. A full integer partitioning and target bond dissection mapping analysis for three-component couplings of this heterocycle, as shown in Figure 9, indicates that the chemical space consists of twelve [3 + 2 + 1], six [4 + 1 + 1], and two [2 + 2 + 2] possible

Et₃B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

• Ahlem Abidi,
• Yosra Oueslati and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

• of the MBH carboxylates with aliphatic 1,3-diketones in the presence of K2CO3. A drawback of these synthetic approaches is the need to first perform the acylation step of the corresponding allyl MBH alcohols. For this reason, we herein report an efficient direct method for the allylation of β

• acidity is relatively higher, led to a mixture of the mono- and bis-alkylation products 3c and 4c in 45 and 23% yields, respectively (Table 2, entries 1–3). Under the same conditions, the allylation of a variety of β-keto esters and β-diketones (Table 2, entries 4–9), in DMF at 80 °C, selectively gave the

• selected the acyclic alcohol 1b to react with stabilized carbanions derived from the β-keto esters 2e–f and β-diketones 2g–i in anhydrous THF using 1 equiv of NaH and 2 equiv of Et3B. Under these conditions, all these reactions worked well in refluxing THF, affording in 2 h the corresponding monoallylation

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

• -catalyzed rearrangement of endoperoxide 242b containing an electron-withdrawing substituent leads to a product mixture of hydroxy ketone 244, and diketones 245 and 246 (Scheme 75) [353]. A further study [352] on the base-catalyzed rearrangements of substituted bicyclic endoperoxides showed that the pathway

• hand, endoperoxides 249a,b bearing electron-withdrawing groups (ester, acetyl) attached to the seven-membered ring are isomerized to diketones 250a,b (Scheme 77) [345]. The Kornblum–DeLaMare reaction of endoperoxide 251a containing an electron-withdrawing substituent at the bridge head atom lead to the

• -diketones 283 (Scheme 84) [359][360]. The Kornblum–DeLaMare rearrangement of 1,2-dioxenes 284 [361], 1,2-dioxanes 286 [362], and tert-butyl peroxides 288 [330][363] produces 1,4-dicarbonyl compounds 285, 287, and 289, respectively (Scheme 85). These compounds are versatile starting substrates for the

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• carbonyl compounds such as β-diketones, β-keto thioesters, acetoacetamides and nitroacetone have been shown to participate in the classical Biginelli reaction [25], β-ketophosphonates 6 were found to be unreactive in similar conditions [26]. However, Yuan et al. developed a modified Biginelli condensation

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• Paul Hommes Hans-Ulrich Reissig Freie Universität Berlin, Institut für Chemie und Biochemie, Takustrasse 3, D-14195 Berlin, Germany 10.3762/bjoc.12.112 Abstract The scope of a flexible route to unsymmetrically functionalized bipyridines is described. Starting from 1,3-diketones 1a–e, the

• we reported on a new pyridine synthesis starting from symmetrically substituted 1,3-diketones 1a and 1b, respectively, that were converted into the corresponding β-ketoenamines and subsequently by N-acylation into β-ketoenamides such as 3a or 3b [1]. Their cyclocondensation followed by O-alkylation

• available in excellent yields from the 1,3-diketones 1a and 1b employing aqueous ammonia in the presence of silica gel [21]. Compound 2c was prepared from 1c in 87% yield with ammonium formate [22][23]. Interestingly, treatment of 1c with aqueous ammonia/silica gel failed to give 2c, deacetylation to 1

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

• José M. Andrés,
• Miriam Ceballos,
• Alicia Maestro,
• Isabel Sanz and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

• -diketones. Reaction of nitrostyrenes with β-keto esters and β-dicarbonyl compounds. Reaction of nitrostyrenes with α-nitrocyclohexanone and ethyl α-nitropropionate. Screening of catalysts and optimization of the reaction conditions for the additions of diethyl malonate and ethyl 2-oxocyclopentanecarboxylate

• to β-nitrostyrene. Addition of malonates and β-diketones to nitrostyrenes catalyzed by IV and V. Reaction of nitrostyrenes with β-substituted cycloalkanones catalyzed by V. Reactions of nitrostyrenes with α-nitrocyclohexanone and ethyl α-nitropropionate. Supporting Information Supporting Information

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• practical application of these metal-free methods. The application of copper catalysts was found as effective solution to some of these problems. For example, Wu et al. [70] reported the efficient synthesis of α-iodoketals 76 and 77 via CuO-mediated selective mono-iodination of diketones 74 and

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles

• Kandasamy Rajaguru,
• Arumugam Mariappan,
• Rajendran Suresh,
• Periasamy Manivannan and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219

• Abstract The reaction of α-azidochalcones with carboxylic acids has been investigated resulting in the formation of α-amido-1,3-diketones under microwave irradiation via in situ formation of 2H-azirine intermediates. An interesting reaction is described wherein, with trifluoroacetic acid at lower

• temperature, it affords highly substituted 2-(trifluoromethyl)oxazoles. These flexible transformations proceed under solvent free conditions in good to excellent yields without any catalyst. Keywords: α-amido-1,3-diketones; α-azidochalcones; carboxylic acids; 2H-azirines; oxazoles; Introduction α

• various substituted benzoic acids 2d–g as well and the resultant α-amido-1,3-diketones 3k–o are obtained in moderate to good yields (Figure 3). The mechanism for the formation of α-amido-1,3-diketone 3 is given in Scheme 2. Initially, by thermolysis, α-azidochalcone undergoes denitrogenative decomposition

Design and synthesis of hybrid cyclophanes containing thiophene and indole units via Grignard reaction, Fischer indolization and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Mukesh E. Shirbhate

Beilstein J. Org. Chem. 2015, 11, 1514–1519, doi:10.3762/bjoc.11.165

• explored the alternative option to the target cyclophane 1 involving the bisindolization followed by RCM (Figure 1, Route B). To design aza-polyquinanes, we reported several bisindole derivatives starting with diketones under conditions of a low melting reaction mixture [38][39][40]. Based on this insight

An intramolecular C–N cross-coupling of β-enaminones: a simple and efficient way to precursors of some alkaloids of Galipea officinalis

• Hana Doušová,
• Radim Horák,
• Zdeňka Růžičková and
• Petr Šimůnek

Beilstein J. Org. Chem. 2015, 11, 884–892, doi:10.3762/bjoc.11.99

• the starting substrates A simple retrosynthesis of enaminones 3 leads to the corresponding β-diketones 4 accessible through Claisen condensation of 3-phenylpropionic ester 5 with the appropriate acetophenone 6 (Scheme 3). The synthesis of ester 5 was accomplished according to Scheme 4. The classic

• -Diketones 4 were obtained using tert-butoxide or tert-pentoxide mediated Claisen condensation of esters 5 with the appropriate acetophenones 6a–d (Scheme 5, step c). The substitution pattern on compounds 6 was chosen so that the final products 1 are the precursors for the synthesis of galipinine, galipeine

• -diketones 4 with ammonium surrogate (AcONH4 or NH4HCO3). The regioselectivity of the synthesis was checked by means of 2D 1H–13C HMBC (See Supporting Information File 1, page S69). The non-equivalence of NH2 protons together with the relatively high chemical shift of one resonance of the pair (δ ≈ 10 ppm

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

• Gebze-Kocaeli, Turkey 10.3762/bjoc.11.46 Abstract This review aims to give an overview of the current status of our research on the synthesis of π-electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, ET) analogues prepared from 1,8-diketones via a ring forming reaction. The new synthesized π

• molecules, obtained from 1,8-diketone ring closure reactions, and coupling reactions, published by our group. Review BVDT-TTF analogues from 1,8-diketones Bis(vinylenedithio)tetrathiafulvalene (BVDT-TTF) 4 (R = Ph, 4-CH3OC6H4, 4-BrC6H4, 4-CH3C6H4, 4-O2NC6H4, 2-thienyl) is a fully unsaturated analogue of

• produce 13 as a minor product through the intermediate 12 by the loss of elemental sulfur. The reaction of a series of 1,8-diketones with LR 15 or P4S10 was further explored in 2003 [53]. With both reactants, 1,4-dithiin 11 was obtained as a major and thiophene 13 as a minor product along with the side

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• 5-acyl-substituted 2H-1,4-oxazines. They could, in principle, be prepared from azirines and α-diazo ketones or 2-diazo-1,3-diketones via ring opening across the N–C2 bond in the intermediate azirinium ylides to form 2-azabuta-1,3-dienes and subsequent cyclization of the latter into 2H-1,4-oxazines

• the mechanism of trapping of dihydroazireno[2,1-b]oxazole intermediates by acetyl(methyl)ketene were investigated by the DFT method. Results and Discussion Rhodium(II) carbenoids generated from α-diazoketones or 2-diazo-1,3-diketones react with various nitrogen-containing compounds, such as amines [16

• generated by thermolysis of 2-diazo-1,3-diketones [12] or 5-arylfuran-2,3-diones [13]. Therefore, the presence of compounds 8f,g among the reaction products provides evidence for the formation of some amounts of acetyl(methyl)ketene (12) under the reaction conditions, which, in turn, gives us insight to the

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• of the compounds 4–6a through the intermediate 7 (pathway A) as for cyclic 1,3-diketones [13][25] was excluded because the latter does not react with amide 3a under any comparable conditions. Most likely the formation of chroman-3-carboxamide 4a proceeds through imine 8 (pathway B) since the reaction

(CF₃CO)₂O/CF₃SO₃H-mediated synthesis of 1,3-diketones from carboxylic acids and aromatic ketones

• JungKeun Kim,
• Elvira Shokova,
• Victor Tafeenko and
• Vladimir Kovalev

Beilstein J. Org. Chem. 2014, 10, 2270–2278, doi:10.3762/bjoc.10.236

• application of the proposed protocol allowed for the synthesis of selected polysubstituted pyrazoles in a one-pot procedure directly from acids and ketones. Keywords: Claisen condensation; 1,3-diketones; heterocycles; triflic acid; trifluoroacetic acid anhydride; Introduction 1,3-Diketones represent one of

• synthesis of β-diketones from acids and ketones with an immediate activation of both carbonyl and methylene components in the course of the reaction. Herein, we would like to describe a direct and operationally simple TFAA/TfOH-mediated synthesis of 1,3-diketones from unmodified carboxylic acids and ketones

• (indanones, tetralone, acetophenones, 2-acetylthiophene and methyl benzyl ketone) with alkanoic acids RCOOH 1d–h (where R = 1-adamantylmethyl, neopentyl, isopropyl, methyl, phenyl) gave the corresponding β-diketones 3c–t in 37–86% yields (Table 2). In most cases reactions were carried out at the molar ratios

Derivatives of the triaminoguanidinium ion, 3. Multiple N-functionalization of the triaminoguanidinium ion with isocyanates and isothiocyanates

• Jan Szabo,
• Kerstin Karger,
• Nicolas Bucher and
• Gerhard Maas

Beilstein J. Org. Chem. 2014, 10, 2255–2262, doi:10.3762/bjoc.10.234

• 1,3-diketones follow condensation/cyclization pathways resulting in unsymmetrical N-heterocyclic products [14][15]. Azidation of TAG-Cl with two equivalents of sodium nitrite in water afforded the highly shock- and friction-sensitive (5-azido-1H-tetrazol-1-yl)carbonimidoyl diazide rather than the

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• excellent ee (up to 96%). In subsequent transformations, the β-lactone products underwent various ring opening reactions to provide very useful derivatives, such as 1,3-diketones and enol esters, with good diastereoselectivity. 2.12 Annulations through domino aza-MBH/Michael reactions Because

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2014, 10, 2021–2026, doi:10.3762/bjoc.10.210

• , and also furnishes three dehydration products, the anti-configurated diketones 21–23, produced in a 1:3:1 ratio. Again the fully or partially conjugated isomers are deeply colored (intense yellow) and display absorption maxima at 389 and 358 nm, respectively (Scheme 6). For 21 yellow single crystals

A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H)-furanones

• Jubi John,
• Eliza Târcoveanu,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 1462–1470, doi:10.3762/bjoc.10.150

• [19][20][21][22][23][24][25][26]. Synthetic routes for the preparation of these compounds involve transformations of substituted α-hydroxy-1,3-diketones [15][17], substituted furans [27][28][29], cyclization of allenic hydroxyketones [30], transition metal-catalyzed strategies (Au [31][32][33], Pt [34

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• the reaction, and the results are summarized in Scheme 3. The 1,2-dibromo products were obtained in moderate to high yields. With the success of the bromination of phenols and alkenes, we further focused on the complementary bromination of diketones and cyclization reactions. The treatment of

• (monitored by TLC). After the reaction was completed, the solvent was concentrated in vacuo. The residue was purified by flash column chromatography to give the final product. Bromination of diketones To a 10 mL round bottom flask equipped with a magnetic stir bar were added 5 (0.4 mmol), CBr4 (133 mg, 0.4

• situ generation of bromine. Synthesis of dibromophenol product 2b''. Scope of the photocatalytic bromination of alkenes. Bromination of diketones and cyclization reactions. Survey of the photocatalytic bromination reaction conditions. Scope of the photocatalytic bromination of phenols. Supporting

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• several substituents and enolates 33 can be generated from methyl- or ethyl vinyl ketone, the corresponding α,β-unsaturated esters being unreactive. Enamines 34 arise from cyclic or linear C3–C5 ketones, acetophenones and β-diketones. It is noteworthy, that the reactions are highly regiospecific for

Secondary amine-initiated three-component synthesis of 3,4-dihydropyrimidinones and thiones involving alkynes, aldehydes and thiourea/urea

• Jie-Ping Wan,
• Yunfang Lin,
• Kaikai Hu and
• Yunyun Liu

Beilstein J. Org. Chem. 2014, 10, 287–292, doi:10.3762/bjoc.10.25

• ) [14] has been dominantly employed for DHPMs synthesis in both racemic [15][16][17][18] and asymmetric versions [19][20][21][22][23]. Despite of many recognized advantages of the Biginelli reaction, the product diversity suffered from limitations because β-ketoesters or 1,3-diketones are intrinsically

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

• Kobayashi cyclization of hydroperoxides, the reaction of 1,4-diketones with hydrogen peroxide, the intramolecular nucleophilic substitution by the hydroperoxide group, the cyclization with participation of halogenonium ion donors, acid-mediated rearrangements of peroxides, the palladium-catalyzed

• NaBH4 in an alkaline medium [331]. 3.6. Synthesis of 1,2-dioxanes from 1,4-dicarbonyl compounds The reaction of 1,4-diketones 242 (cyclohexanone derivatives) with hydrogen peroxide in a neutral medium produced 3,6-dihydroxydioxanes 243 albeit without reported yields (Scheme 69). The resulting compounds

Efficient synthesis of dihydropyrimidinones via a three-component Biginelli-type reaction of urea, alkylaldehyde and arylaldehyde

• Haijun Qu,
• Xuejian Li,
• Fan Mo and
• Xufeng Lin

Beilstein J. Org. Chem. 2013, 9, 2846–2851, doi:10.3762/bjoc.9.320

• chemistry [5][6][7][8]. Recently, many one-pot variants of Biginelli-type reactions for the preparation of novel DHPMs using various active methylene compounds [9][10][11][12][13][14][15], such as enaminone, cyclic β-diketones, acetophenone, benzocyclic ketones and β-oxodithioesters etc., have also been

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

• al. [61]. Further, (−)-isosteviol and its esters can be converted into the corresponding 1,2-diketones 5a–c via Riley oxidation [62][63][64][65][66]. The linkage of the two building blocks by condensation reaction of the keto with the amino functionalities presents a promising route for the

• %. Since path A and path B both proceed with almost identical yields, either pathway is suitable for the preparation of such protected 1,2-diketones. Apart from applying 3,5-dinitrobenzyl chloride in the reaction sequence, the conversion of the carboxylic acids 1 and 9 with 4-nitrobenzyl (PNB) chloride was

• overall yields as well, rendering 11 in 54% and 57%, respectively. Upon employing 4-nitrobenzyl chloride, both reaction paths result in slightly higher yields than the analogous reactions with 3,5-dinitrobenzyl chloride. Diketones 10 and 11 were then brought to condensation with hexaammoniumtriptycene