An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• reaction, causing the formation of complex products. Examples of dienes that have previously been used include cyclic diketones (o-benzoquinones) (Scheme 15, reaction pathways (i)) [60][89][156][157][158][160][161][162][163][164][165][211][215][226], o-quinone methides [87], o-xylylenes [125][153

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• reaction with their participation. Asymmetric conjugate addition of activated methylene compounds (such as diketones, keto esters and malonates) to nitroalkenes in the presence of Mg [43], Co [44][45], Mn [45] and Ru [46] complexes was performed. The most remarkable results were obtained with Ni(II

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• best using aromatic aldehydes with both electron-withdrawing and donating substituents in ortho, meta and para-positions. In addition, not only acetoacetates can be employed, but the reaction can be extended to ketones, thioesters, benzoylacetic esters, acetoacetamides, alkylic or cyclic β-diketones

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• -component cyclization of 2-formylbenzoic acids, primary amines and a 1,3-dicarbonyl compounds. The first proposal uses 2-formylbenzoic acid 33 (R = H, conditions A, Scheme 9), cyclic aliphatic and aromatic diketones 34 such as dimedone (R2R3 = -CH2CMe2CH2-) as the 1,3-dicarbonyl partner and a variety of

• = OH, conditions B, Scheme 9) instead of diketones and a quaternary ammonium salt as catalyst in water. In this multicomponent decarboxylative alkylation/cyclization process, they prepared several lactam derivatives 36 with good yields. While the first research group suggests that the reaction would

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

• acid treatment leads to acylamido-substituted 1,2-diketones DK that could be converted into quinoxalines QU. All classes of heterocycles accessed through the key β-ketoenamides show a unique substitution pattern – not easily accomplishable by alternative methods – and therefore many subsequent

• particular heterocyclic compounds. The synthesis of pyrimidines PM, pyrimidine N-oxides PO, oxazoles OX, 1,2-diketones DK and quinoxalines QU starting from β-ketoenamides KE is the topic of the present review. Review Scope of the LANCA three-component synthesis of β-ketoenamides The scope of the LANCA three

• -(trimethylsilyl)ethoxy-substituted β-ketoenamides KE as precursors and - mainly depending on the size of substituent R2 - oxazoles OX and/or the simple hydrolysis products 1,2-diketones DK were isolated in moderate to excellent yields (Table 6). With substituents R2 of moderate bulkiness the oxazoles OX are

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

• -workers also reported the first silver-catalyzed ring-opening and acylation of cyclopropanols 91 with aldehydes 48 for the synthesis of 1,4-diketones 144 (Scheme 39) [119]. They proposed that the involvement of an uncommon water-assisted 1,2-HAT process was strongly exothermic and it promoted the addition

A convenient and practical synthesis of β-diketones bearing linear perfluorinated alkyl groups and a 2-thienyl moiety

• Ilya V. Taydakov,
• Yuliya M. Kreshchenova and
• Ekaterina P. Dolotova

Beilstein J. Org. Chem. 2018, 14, 3106–3111, doi:10.3762/bjoc.14.290

• , Moscow Region, Russian Federation D. Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9, 125047 Moscow, Russian Federation 10.3762/bjoc.14.290 Abstract A versatile and robust synthetic protocol for the preparation of β-diketones bearing 2-thienyl and perfluorinated alkyl radicals of

• different length or a methyl group was developed. This protocol is suitable for the preparation of multigram quantities of diketones without cumbersome purification procedures. Moreover, the known method for purification of diketones via copper chelates was improved considerably. Keywords: Claisen

• condensation; copper chelate; β-diketones; perfluorinated esters; thiophene; Introduction Classical β-diketones have been studied for more than a century, and no doubt, they are the most popular O,O-ligands in the coordination chemistry of d- and f-elements [1][2][3]. These compounds are widely used as

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• on the 1H-imidazo[2,1-a]isoindolone skeleton, Hosseini-Zare et al. reported the synthesis of new 2,3-diaryl-5H-imidazo[2,1-a]isoindol-5-ones via the one pot reaction of 1,2-diketones, 2-formylbenzoic acid and ammonium acetate [15]. These methodologies usually use toxic solvents such as benzene [16

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• amount of HPW on silica decreased the yield of reaction [62]. The silica sulfuric acid (SSA) catalyst was synthesized by the treatment of silica gel with sulfuryl chloride under room temperature stirring. The catalyst was used in the acylation of amines with 1,3-diketones via C–C bond cleavage. Various

• protected aniline derivatives were obtained by the solvent-free reaction of anilines with 1,3-diketones at 120 °C or 140 °C in the presence of 2 equiv of water under 1 atm O2 atmosphere (Scheme 16). The probable reaction pathway for this reaction is shown in Scheme 16. Arylamine 15 attacks the activated

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

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Keshaba N. Parida,
• Gulab K. Pathe,
• Shimon Maksymenko and
• Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

• of enolates may be used to form the 1,4-diketone products in 38 to 74% yield. Due to the use of two TMS enol ethers as precursors, an optimization of the cross-coupling should include investigating the order of addition. Keywords: 1,4-diketones; enolates; enolonium species; hypervalent iodine

• . Recently, Loh reported the palladium-catalyzed coupling of an acid chloride with premade isolable indium homoenolates (In(CH2CHRC=OR')2), 1.2 equiv relative to the acid chloride) to give the corresponding 1,4-diketones [5]. Yet the direct coupling of two enolates is inarguably the shortest and most direct

• = H) to afford the 1,4-diketone 7 in 71% yield (Scheme 2) [31]. We therefore focused on identifying the minimum amount of the second enolate that would lead to optimal yields and found that as little as 1.2–1.4 equiv provided the desired 1,4-diketones in acceptable yields without the need for a large

Enhanced quantum yields by sterically demanding aryl-substituted β-diketonate ancillary ligands

• Rebecca Pittkowski and
• Thomas Strassner

Beilstein J. Org. Chem. 2018, 14, 664–671, doi:10.3762/bjoc.14.54

• changing the ancillary ligand from acetylacetonate (R = CH3) to sterically demanding aryl-substituted β-diketones (R = 2,4,6-trimethylphenyl, 2,3,5,6-tetramethylphenyl). The drastically increased quantum yield was accompanied by a shift in the emission color from the deep-blue to the sky-blue spectral

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• thiophenes (8aa–ai) were obtained in moderate to excellent yields (47–92%). When different 1,3-diketones were applied, the yields were affected by the keto–enol tautomer ratio. Alkyl substituents (isopropyl and cyclopropyl), which promote the enol forms of the ketones, afforded thiophenes 8aj and 8ak in good

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• convenient regioselective synthetic methods with mild conditions and good yields of the reactions [40][41]. Aggarwal et al. [42] reported the regiospecific synthesis of 4-trifluoromethyl-1H-pyrazolo[3,4-b]pyridines 18 by the reaction of 5-aminopyrazole 16 with trifluoromethyl-β-diketones 17 in refluxing

• predominant. The keto form 17 results in the formation of 6-trifluoromethylpyrazolo[3,4-b]pyridines 20 by attack of the 5-NH2 group (from 5-aminopyrazole 16) on the more electrophilic carbonyl group attached to CF3 (from trifluoromethyl-β-diketones 17) whereas the enolic form 21 reacts with the less

• -b]pyridine-spiroindolinone nucleus 59 with a high degree of regioselectivity without formation of the regioisomeric pyrazolo[1,5-a]pyrimidine 60 involving three-component reaction of 5-aminopyrazole 16, isatin 54 and cyclic β-diketones 58 in aqueous ethanol with p-TSA as catalyst (Scheme 13

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• 10.3762/bjoc.13.277 Abstract 4-Aza-6-nitrobenzofuroxan (ANBF) reacts with 1,3-dicarbonyl compounds and other CH acids to give carbon-bonded 1,4-adducts – 1,4-dihydropyridines fused with furoxan ring. In the case of most acidic β-diketones, which exist mainly in the enol form in polar solvents, the

• -dinitrobenzofuroxan (DNBF) another reaction pathway was observed. DNBF react with β-diketones and even monoketones in DMSO solution to give carbon-bonded σ-adducts in the absence of any added base [15] (Scheme 2). However, DNBF is a typical superelectrophile [16], it reacts very easily with water or methanol without

• starting material and resinification. Apparently, it was caused by interaction of Et3N with ANBF because the blank experiment (1 + Et3N with no ketone added) also resulted in decomposition of ANBF. Therefore we studied reactions of 1 with more acidic 1,3-diketones, ketoesters and related compounds. The

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

• Dmitry Yu. Vandyshev,
• Khidmet S. Shikhaliev,
• Andrey Yu. Potapov,
• Michael Yu. Krysin,
• Fedor I. Zubkov and
• Lyudmila V. Sapronova

Beilstein J. Org. Chem. 2017, 13, 2561–2568, doi:10.3762/bjoc.13.252

• [1,5-b]pyridazines along route B, 1-aminoimidazoles with no substituents at the C-5 atom of the original heterocycle and 1,3-dielectrophilic reagents are used, e.g., 1,3-diketones [24][25][26], β-ketoesters [24], α,β-unsaturated ketones [27][28], including those obtained in situ [29][30] or containing

Synthesis of ergostane-type brassinosteroids with modifications in ring A

• Vladimir N. Zhabinskii,
• Darya A. Osiyuk,
• Yuri V. Ermolovich,
• Natalia M. Chaschina,
• Tatsiana S. Dalidovich,
• Miroslav Strnad and
• Vladimir A. Khripach

Beilstein J. Org. Chem. 2017, 13, 2326–2331, doi:10.3762/bjoc.13.229

• -dehydroteasterone 32, which is unknown as a natural phytohormone. 3α- and 3β-alcohols of type 10 and 11 The hydride reduction of 3,6-diketones proceeds in a regioselective manner at the C-3 position [19]. Both 3α- and 3β-alcohols of type 10 and 11 (Scheme 1) can be obtained in this way depending on the reducing

• agent used. Thus, the reaction of 3,6-diketones with K-selectride was shown to afford 3α-hydroxy-6-ketones [31]. On the other hand, treatment of the diketone 31 with NaBH4 followed by acetate deprotection led to 24-epiteasterone (34) having a 3β-hydroxy group on the A-ring (Scheme 7). 2α-Hydroxy-3

Curcuminoid–BF₂ complexes: Synthesis, fluorescence and optimization of BF₂ group cleavage

• Henning Weiss,
• Jeannine Reichel,
• Helmar Görls,
• Kilian Rolf Anton Schneider,
• Mathias Micheel,
• Michael Pröhl,
• Michael Gottschaldt,
• Benjamin Dietzek and
• Wolfgang Weigand

Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223

• the molecule [9]. Although a range of papers reports the synthesis of BF2 complexes of β-diketones such as curcuminoids [13][14] or dibenzoylmethanes [15][16], to our knowledge the reported procedures for the hydrolysis of these complexes are very limited and not always reproducible. As part of our

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• likely to involve a nitrosoalkene intermediate, which is generated upon the action of TBAF or the anion of the 1,3-dicarbonyl compound on N,N-bis(silyloxy)enamine 3. Unlike malonic acid derivatives and β-keto esters, 1,3-diketones produced only complex mixtures of products in the reaction with N,N-bis

NHC-catalyzed cleavage of vicinal diketones and triketones followed by insertion of enones and ynones

• Ken Takaki,
• Makoto Hino,
• Akira Ohno,
• Kimihiro Komeyama,
• Hiroto Yoshida and
• Hiroshi Fukuoka

Beilstein J. Org. Chem. 2017, 13, 1816–1822, doi:10.3762/bjoc.13.176

• -diketones and 1,2,3-triketones with enones and ynones have been investigated. The diketones gave α,β-double acylation products via unique Breslow intermediates isolable as acid salts, whereas the triketones formed stable adducts with the NHC instead of the coupling products. Keywords: Breslow intermediate

• convert aldehydes to nucleophilic species, which react with activated alkenes to yield hydroacylation products [10][11][12][13][14]. When the carbonyl compounds I other than aldehyde behave similarly, functionalized 1,4-diketones IV would be produced (Scheme 1). Previously, we reported that benzils I (G

• ring-enlargement procedure to afford cyclic 1,4-diketones IV. With respect to the active species in the Stetter reaction, aminoenols II (G = H, Breslow intermediates) had been postulated as true nucleophiles for a long time and those generated from imidazolinium NHC were recently isolated in pure form

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

• Josef Jansa,
• Ramona Schmidt,
• Ashenafi Damtew Mamuye,
• Laura Castoldi,
• Alexander Roller,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90

• -diketones with arylhydrazines, halogenation of the resulting 1,3,5-triarylpyrazoles in the 4-position and further functionalization via Negishi cross-coupling [23][24] or halogen–lithium exchange reaction (Scheme 1). The resulting compounds amongst others seem to be interesting as potential complexing

• agents. Results and Discussion Chemistry Synthesis of 4-iodopyrazoles 3a–d As starting materials the symmetrical 1,3-diketones 1a and 1b were employed, which were obtained by condensation of ethyl 2- or 3-pyridinecarboxylates with the appropriate 2- or 3-acetylpyridines following known procedures [25][26

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

• ] cycloaddition between 1,3-diketones and aryl azidophenyl selenides. These sonochemically promoted reactions were found to be amenable to a range of 1,3-diketones or aryl azidophenyl selenides, providing an efficient access to new ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones in good to excellent yields and

• of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones by reacting a range of 1,3-diketones with substituted aryl azidophenyl selenides (Scheme 1). Results and Discussion Due to the fact that organocatalyzed β-enamine–azide cycloaddition reactions between azidophenyl aryl selenides and 1,3-diketones

• , optimum reaction conditions were extended to other 1,3-diketones 2a–e with different substitution patterns (Table 2). High yields of desired 1,2,3-triazoles were obtained using β-diketones 2a, 2b and 2c bearing methyl, ethyl and phenyl substituents (Table 2, entries 1–3). However, we observed that the

Isoxazole derivatives as new nitric oxide elicitors in plants

• Anca Oancea,
• Emilian Georgescu,
• Florentina Georgescu,
• Alina Nicolescu,
• Elena Iulia Oprita,
• Catalina Tudora,
• Lucian Vladulescu,
• Marius-Constantin Vladulescu,
• Florin Oancea and
• Calin Deleanu

Beilstein J. Org. Chem. 2017, 13, 659–664, doi:10.3762/bjoc.13.65

• synthetic approaches towards the isoxazole core include the reactions of hydroxylamine with aryl-β-diketones [20], α,β-unsaturated carbonyl compounds [21], or α,β-unsaturated nitriles [22], and 1,3-dipolar cycloaddition reactions between alkenes or alkynes and nitrile oxides [23][24][25]. Nitrile oxides are

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• papilloma virus type 11 (HPV11) inhibitors. These 1-indanones 99 have been synthesized using a N-heterocyclic carbene-catalyzed [4 + 1] annulation utilizing phthalaldehyde (97) and 1,2-diactivated Michael acceptors 98 (Scheme 31) [55][56]. 1.1.5 From ketones and 1,2-diketones: Another interesting approach

Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

• Mathew J. Jones,
• Ricardo Callejo,
• Alexandra M. Z. Slawin,
• Michael Bühl and
• David O'Hagan

Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

• conformation. To the best of our knowledge, 2,2,6,6-tetrafluorocyclohexanol is the only derivative containing this feature reported so far. It was prepared in an eight step synthesis [22]. At the outset we explored a more direct synthesis of this arrangement based on deoxofluorination of 1,3-diketones 5 with

• relationship. Results and Discussion The preparation of diketones 5a–c and bis-dithianes 6a–c was carried out by previously described methods. The dimethyl-diketone 5c was prepared by double methylation of 5b [25] (Scheme 2). Two different O-alkylated products 7 and 8 were also obtained as significant

• diketones 5a–c was explored with DAST or Deoxo-Fluor® (Scheme 3). When diketones 5a and 5b were treated with DAST or Deoxo-Fluor®, either neat or in DCM as a solvent, only complex and intractable products were obtained. These highly enolisable diketones [27][28] were incompatible with deoxyfluorination. In