Synthesis of 2,2-difluoro-1,3-diketone and 2,2-difluoro-1,3-ketoester derivatives using fluorine gas

• Alexander S. Hampton,
• David R. W. Hodgson,
• Graham McDougald,
• Linhua Wang and
• Graham Sandford

Beilstein J. Org. Chem. 2024, 20, 460–469, doi:10.3762/bjoc.20.41

• Swing Road, Greensboro, North Carolina, NC 27409, USA 10.3762/bjoc.20.41 Abstract Solutions of 1,3-diketones and 1,3-ketoester derivatives react with fluorine to give the corresponding 2,2-difluoro-1,3-dicarbonyl derivatives in the presence of quinuclidine. Quinuclidine reacts with fluorine in situ to

• agents offers an alternative fluorination route, for example, the reactions of MeCN solutions of 1,3-diketones with electrophilic fluorinating agents such as Selectfluor eventually give the corresponding 2,2-difluoro-1,3-diketone derivatives [12]. Monofluorination of the 1,3-diketone substrates is rapid

• corresponding 2,2-difluoroketones [15]. In related kinetic studies concerning the electrophilic 2-fluorination of 1,3-diketones with Selectfluor [16][17], we demonstrated that the rate-determining step for difluorination was enolization of the intermediate 2-fluoro-1,3-diketone. Monofluorination of 1,3

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• π-CPCs relies on the extrusion of carbon monoxide (CO) from soluble precursors incorporating bridging ketone fragment(s). In contrast with the thermal activation required in retro-Diels–Alder reactions, photoirradiation of α-diketones triggers a Strating–Zwanenburg decarbonylation leading to the

• release of two CO molecules (Scheme 1, top right). After a proof of concept on pentacene with soluble precursors including a bicyclo[2.2.2]octane-2,3-dione framework [20][21], α-diketones were intensely exploited as soluble photoprecursors for the synthesis of acenes of increasing length up to undecacene

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• trifluoroacetonitrile imine, are highly versatile in that they react with olefins, acetylenes, dimethyl fumarate, dimethyl maleate, β-diketones, β-keto esters, bicyclic olefins, and potassium isothiocyanate and isocyanate affording the corresponding trifluoromethyl-containing compounds, generally with good yields [51

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• in combination with di-tert-butyl peroxide (DTBP) as an oxidant enables the CDC of the C(sp3)–H bond in the α-position to oxygen of various ethers with the active methylene C(sp3)–H bond in 1,3-diketones (Scheme 17) [78]. This method can generate various functionalized molecules and is expected to

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• 3b used in only three cases [12][13][19], to the best of our knowledge. Extending beyond Scheme 2, only two syntheses of nitrocyclopropanes containing cyclic keto esters or diketones have been reported [20][21]. These findings indicate that the synthesis of nitrocyclopropanes with an acyl group is

• quite difficult, although they would be very useful in synthetic chemistry, if available. In this study, we investigated the synthesis of nitrocyclopropanes using keto esters 3c–f and diketones 3b and 3g instead of diester 3a as the starting 1,3-dicarbonyl compounds. Results and Discussion We commenced

• detected (Scheme 3). Next, method a (Scheme 2) was employed to synthesize nitrocyclopropanes 1 possessing an acyl group. Keto esters 3c–f and diketones 3b and 3g underwent conjugate addition to nitrostyrene 2a to afford the corresponding adducts 4b–g with moderate yields (Table 1). For unsymmetrical

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• pyranone ring leading to the formation of α-hydroxy-1,2-diketones. This phototransformation is initiated by an excited state intramolecular proton transfer (ESIPT) process. In most cases the resulting α-hydroxy-1,2-diketones are unstable and their further reactions open access to various original products

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• trapping by adding MeLi (1.05 equiv), which indeed led to a significant increase in yield and selectivity due to the high reactivity of the lithium dialkyl zincate enolate. Various 1,3-diketones 39 were prepared using this method with good yields and excellent enantioselectivities while only the trans

Oxa-Michael-initiated cascade reactions of levoglucosenone

• Julian Klepp,
• Thomas Bousfield,
• Hugh Cummins,
• Sarah V. A.-M. Legendre,
• Jason E. Camp and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2022, 18, 1457–1462, doi:10.3762/bjoc.18.151

• from 12 gave moderate to low yields of bridged species, most effectively with electron-poor aromatic aldehydes, and reactions had to be monitored to optimize conversions and prevent decomposition (Scheme 2) [14]. Analysis of the NMR spectra indicated that instead of the open chain diketones 13, the

A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

• protocol proceeds in an undivided cell equipped with graphite plate electrodes under constant current conditions. Various active methylene ketones, including β-keto ester, β-keto amide, β-keto nitrile, β-keto sulfone and 1,3-diketones, can be converted to the corresponding 2-aminothiazoles. Mechanistically

Derivatives of benzo-1,4-thiazine-3-carboxylic acid and the corresponding amino acid conjugates

• Péter Kisszékelyi,
• Tibor Peňaška,
• Klára Stankovianska,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 1195–1202, doi:10.3762/bjoc.18.124

• 1,3-dicarbonyl compounds using a catalytic amount of hydrazine hydrate without solvent in a short reaction time (10 min) [14]. Reactions of 2-aminothiophenols with β-keto esters and β-diketones under microwave irradiation (MWI) using basic alumina as heterogeneous catalyst without solvent afforded 4H

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• 1,3-diketones [21], etc. Electrosynthesis is considered as a more sustainable approach to perform chemical reactions, and an interesting alternative to conventional synthetic methods both in laboratory and industry processes. In fact, the electron may be considered to be a clean reagent, which

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• was simplified later on by the use of the hydrochloride salts of the α-aminoamides 2, instead of their free base, along with the addition of a second equivalent of sodium hydroxide [13]. As expected, from asymmetric 1,2-diketones (1, R1 ≠ R2 and ≠ H), reports [14][15][16] describe the occurrence of

A study of the photochemical behavior of terarylenes containing allomaltol and pyrazole fragments

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2022, 18, 588–596, doi:10.3762/bjoc.18.61

• contraction of the 4-pyranone cycle 1 leading to the formation of unstable α-hydroxy-1,2-diketones. These intermediates can be captured intramolecularly using various functional groups present in the molecule or by employment of additional reagents. For example, a convenient method for trapping of unstable α

• -hydroxy-1,2-diketones 2 is the condensation with 1,2-phenylenediamine resulting in the formation of fused quinoxalines 3 (Scheme 1A) [22]. Another variant of similar catching reaction is reduction by NaBH3CN with the formation of diols 4 (Scheme 1A) [23]. Thus, the introduction of additional reagents

• allows the use of photogenerated α-hydroxy-1,2-diketones in the synthesis of various products. An alternative approach for trapping of such unstable intermediates is the preliminary introduction of functional groups into the 3-hydroxypyran-4-one structure. In this case, the intermediate α-hydroxy-1,2

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• 1,3-diketones, β-ketoesters, or β-ketoamides. We optimized the reaction conditions to control the selectivity of the production of isoxazoles and circumvent other competing reactions, such as O-imidoylation or hetero [3 + 2]-cycloaddition. The reaction happens fast in water and completes within 1–2

• needed to be synthesized independently [23]. While ruthenium(II) and palladium catalysts are useful, they are expensive and environmentally unfriendly. The dehalogenation of hydroximoyl chlorides in the presence of a strong base to generate nitrile oxides and a follow-up cycloaddition with 1,3-diketones

• , we herein report a method for the synthesis of 3,4,5-trisubstituted isoxazoles in water under mild basic conditions at room temperature via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides (Figure 1). No additional metal catalyst was used. Results and

Asymmetric organocatalytic Michael addition of cyclopentane-1,2-dione to alkylidene oxindole

• Estelle Silm,
• Ivar Järving and
• Tõnis Kanger

Beilstein J. Org. Chem. 2022, 18, 167–173, doi:10.3762/bjoc.18.18

• presence of a multifunctional squaramide catalyst. Michael adducts were obtained in high enantioselectivities and in moderate diastereoselectivities. Keywords: cyclopentane-1,2-dione; enantioselective catalysis; Michael addition; organocatalysis; squaramide; Introduction Diketones are generally very

• versatile starting materials in organic synthesis [1][2]. Specifically, due to their keto–enol tautomerism and high reactivity, diketones are excellent precursors for different pharmaceuticals [3]. Cyclic 1,3-diketones have been widely exploited to access enantiomerically enriched scaffolds with increased

• to synthesise indoloquinolizidines [5]. Moreover, six-membered and five-membered cyclic 1,3-diketones have been investigated in reactions with acetates of nitroalkenes [6], cyanoacrylates and benzylidene malononitriles [7], ortho-hydroxy-benzhydryl alcohols [8], α,β-unsaturated pyrazolamides [9] and

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• regioisomeric 1,2-oxazole derivatives. Accordingly, the synthetic route starts from the condensation of 1,3-diketones with N,N-dimethylformamide dimethylacetal to form β-enamino ketoester. The latter undergoes a subsequent cycloaddition reaction with hydroxylamine to form regioisomerically substituted 1,2

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• products, ethyl (oxazolin-2-yl)alkanoates 3. Interestingly, the reaction of α-diazo-β-diketones and 2-arylaziridines generated 2-(2-oxoalkylidene)oxazolidines [21], while the current reaction of alkyl α-diazo-β-oxoalkanoates and 2-arylaziridines gave alkyl (oxazolin-2-yl)alkanoates as products, showing

• hydrogen bond. Thus, the tautomerization favors to the left direction, forming D-form products, when α-diazo-β-diketones are as starting materials (R1 = alkyl and aryl), while it predominates to the right direction, generating 2-(alkoxycarbonyl)methyloxazolines as products, when alkyl α-diazo-β

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• . Notably, the reaction did not proceed in the dark or in the absence of the photosensitizer at 30 °C; further, the reaction generated the desired product in lower yield at 120 °C. The scope was broad and tolerated a wide array of 1,3-keto esters and 1,3-diketones, as well as both benzylic and aliphatic C

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• halogenated 2-hydroxypyridines (pyridin-2(1H)-ones) 38 and α,β-unsaturated 1,4-diketones or 1,4-ketoesters 39 in different solvents. The best results (yield 96%, ee >91%) were obtained on using squaramide catalyst in chloroform. However, for others, the yields ranged from 50–98% with good to excellent

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• . Synthesis of bis(indol-3-yl)sulfides using N-silylated 3-bromoindole 93. Fischer indole synthesis of bis(indol-3-yl)sulfides using thio diketones. Oxidative synthesis of bis(indol-3-yl)sulfides using indoles and elemental sulfur. Synthesis of bis(indol-3-yl)sulfides using sulfoxides as sulfur source

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• esters 29, such as 1,3-diketones, β-ketoesters, cyclic 1,3-diketone (dimedone), and β-ketoamide, respectively, to afford desired 1,4,5-trisubstituted 1,2,3-triazoles containing glycosyl with high yield. It should be pointed out that no byproducts were recognized under optimized reaction conditions. In

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• reported the use of active methylene compounds as suitable nucleophiles in intramolecular hydroalkylation reactions (Scheme 2) [25]. In the presence of PdCl2(CH3CN)2, the hydroalkylation of β-diketones 1 gave only 6-endo-trig cyclization products 2 in moderate to good yields (Scheme 2). The methodology

• -substituted β-diketones 2a and 2b (61 and 70% yield, respectively). Notably, the unsaturated carbocycles expected from palladium β-hydride elimination were not observed, indicating that an oxidant was not required in the reaction medium to regenerate the Pd(II) species. Later, deuterium-labeling experiments

• . Despite these disadvantages, this Fe(III) hydroalkylation could be carried out in air instead of an inert atmosphere usually required in gold methodologies. More recently, iridium complexes were used as efficient catalysts in intermolecular hydroalkylation reactions between β-diketones and less reactive

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• sites, and eight possible tautomeric forms. The major tautomer of biguanide has long been debated and different representations have been depicted in textbooks and research articles. Historically, the biguanide structure was presented similarly to diketones (Figure 1, 1a), which led to misunderstandings

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• -fused tetrahydrodibenzoacridinones 9 using phenanthren-9-amine 8, aldehydes 5, and cyclic 1,3-diketones 6 as structural units in ethanol under microwave irradiation to result in the targeted products in excellent yields. A conventional heating used for the same protocol delivered the desired products in

• synthesis of 3-functionalized indoles 34 by employing amines 32, arylglyoxal monohydrate 33 and cyclic 1,3-diketones 6 under microwave irradiation in the greener solvent system EtOH/H2O (Scheme 10). A plausible mechanism (Scheme 11) suggests a TFA-catalyzed Knoevenagel condensation between 4-hydroxy-6

• ). The synthesis of indoline-spiro fused pyran derivatives 53 was reported by Jiang and co-workers [57] employing a multicomponent reaction between substituted isatins 35, cyclic 1,3-diketones 6 and malononitrile (51) in an aqueous medium without any catalyst. Reaction diversity was examined by using