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

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

• 3v in 23% yield. In addition to β-keto esters, other active methylene derivatives, including β-ketoamide, β-keto nitrile and β-keto sulfone were also suitable coupling partners with relatively lower yields (3w–y) and most of the starting materials were recovered. The method could also be applied to

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

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• reagent [9][10][11], and phenylsulfonyl group transfer reagent [12][13]. In the field of mechanochemistry, the usefulness of N-fluorobenzenesulfonimide has been exemplified in the asymmetric fluorination of β-keto esters (Scheme 1a) [14], and in diastereoselective fluorinations (Scheme 1b) [15], which

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

• generation of DNA-encoded chemical libraries. Results and Discussion The synthetic strategy for the synthesis of novel functionalized 1,2-oxazole derivatives is outlined in Scheme 1. The synthetic sequence began with preparing β-keto esters 2a–h by treating N-Boc-protected cyclic amino acids 1a–h with

• Meldrum’s acid in the presence of EDC·HCl and DMAP, followed by methanolysis of the corresponding adducts [27][28][31][36][37][38]. Reaction of the resulting β-keto esters 2a–h with N,N-dimethylformamide dimethylacetal afforded cycloaminyl β-enamino ketoesters 3a–h. After isolation of compounds 3a–h from

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

• the highest result with a 56% ee. F-CD-BF4 30-1 is a nonhygroscopic, free-flowing solid with a high decomposition point (189 °C, dec). Enantioselective fluorinations of the sodium enolates of other ketones and β-keto esters with F-CD-BF4 30-1 were also investigated. The trimethylsilyl enol ether of 2

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

• of a Lewis acid (LA) to activate 1,3-dicarbonyls through the formation of metallic enolates was recently explored by Schindler’s group for the intramolecular tert-alkylation of prenylated β-keto esters 103 (Scheme 39A

Selective synthesis of α-organylthio esters and α-organylthio ketones from β-keto esters and sodium S-organyl sulfurothioates under basic conditions

• Jean C. Kazmierczak,
• Roberta Cargnelutti,
• Thiago Barcellos,
• Claudio C. Silveira and
• Ricardo F. Schumacher

Beilstein J. Org. Chem. 2021, 17, 234–244, doi:10.3762/bjoc.17.24

• 10.3762/bjoc.17.24 Abstract We described herein a selective method to prepare α-organylthio esters and α-organylthio ketones by the reaction of β-keto esters with sodium S-benzyl sulfurothioate or sodium S-alkyl sulfurothioate (Bunte salts) under basic conditions in toluene as the solvent at 100 °C. When

• tautomers was possible, revealing them as significant intermediates for the mechanism elucidation. Keywords: α-alkylthio esters; α-alkylthio ketones; Bunte salts; C–C bond cleavage; β-keto esters; Introduction During the last ten years, sodium S-organyl sulfurothioates, also known as Bunte salts, were

• or α-thio ketones starting from β-keto esters. It is worthwhile to note herein that although some excellent synthetic protocols have already been developed, there is a gap to be filled in the preparation of α-benzyl thiocarbonyl and α-alkyl thiocarbonyl compounds not fully explored by these recent

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• photocatalysis. The first example of PTC being used in combination with photocatalysis was developed by Gao towards the oxygenation of 1-indanone derived β-keto esters 159 (Scheme 23) [73]. Gao proposes tetraphenylporphyrin (TPP) acting as a sensitiser to form 1O2 via photoinduced energy transfer, which is then

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• compounds, was efficiently implemented via this disulfide, which induced an aerobic oxidation. The hydroxylation and hydroxymethylation of a broad range of β-keto esters and β-keto amides that had electron-donating or -withdrawing groups on the phenyl ring gave good to excellent yields (42–98%, Scheme 10

• ). One exceptional decrease in the yield of the hydroxylation product (13–33%) occurred when β-keto esters with methoxy groups on the phenyl ring were used, but the hydroxymethylation yield was just undulated slightly. Other carbonyl compounds, 1,3-diones, and functionalized five-, six-, and seven

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• 96:4), but low dr (up to 66:33) (Scheme 40) [90]. Another relevant example has been described by Meng and co-workers with the synthesis of α-hydroxy-β-keto esters using TPP, a visible-light source, and a phase-transfer catalyst (PTC) as enantio-catalyst [91]. They reported the preparation of indanone

• -α-hydroxy-β-keto esters in 81–93% yields and 39–75% ee (Scheme 41). The mechanism of this reaction involves the attack of the enolate paired with the chiral counter ion PTC to the singlet oxygen electrophile to give the hydroperoxide intermediate, which is converted to α-hydroxy-β-keto esters

• amides (71–99% yields) and with 5–66% ee (Scheme 42). In 2018, Meng and co-workers developed a bifunctional photo-organocatalyst combining both the photosensitizer and the chirality inducer. Relevant enantiomeric excesses were observed (up to 86% ee) in the oxidation of both β-keto esters and β-keto

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds

• Vuyisa Mzozoyana,
• Fanie R. van Heerden and
• Craig Grimmer

Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22

• chloride (1) to yield methyl 2-fluorobenzoylacetate (3) [38][39]. These reactions are very rare in the literature, however, there are similar reactions for the synthesis of β-keto esters as reported by Sijbesma et al. [40] and Anwar [41]. The second step of the synthesis was the Pechmann reaction, commonly

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• co-workers [71] described the one-pot asymmetric gem-chlorofluorination of active methylene compounds by using a copper(II) complex with a chiral spiro 2-pyridyl monooxazoline ligand (SPYMOX). The corresponding α-chloro-α-fluoro-β-keto esters were isolated with up to 92% ee (Scheme 29a). This

• approach could be extended to asymmetric gem-chlorofluorination of β-ketophosphonates. Two years later, the same authors [72] demonstrated the highly enantioselective fluorination of α-alkyl-β-keto esters and α-alkylmalonates using the same catalyst system (Scheme 29b). Moreover, various cyclic and acyclic

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

• Juanjuan Feng,
• Tianyu Li,
• Jiaxin Zhang and
• Peng Jiao

Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179

• could be prepared from enantiomerically pure β-hydroxy ketones through β-hydroxy-directed carbonyl reduction following Evans’ [3] or Prasad’s [4][5][6][7][8][9][10][11] method. The Narasaka–Prasad reduction of a δ-hydroxy-β-keto esters derived from β-hydroxy esters [12][13][14][15][16][17][18][19][20

Vicinal difunctionalization of alkenes by four-component radical cascade reaction of xanthogenates, alkenes, CO, and sulfonyl oxime ethers

• Shuhei Sumino,
• Takahide Fukuyama,
• Mika Sasano,
• Ilhyong Ryu,
• Antoine Jacquet,
• Frédéric Robert and
• Yannick Landais

Beilstein J. Org. Chem. 2019, 15, 1822–1828, doi:10.3762/bjoc.15.176

• reaction using xanthogenates, alkenes, and sulfonyl oxime ethers (Scheme 1, reaction 1) [21][22]. The reaction proceeds efficiently to provide good yields of α-alkoxyimino esters, potential precursors of lactams, lactones and β-keto esters. Since the three-component radical reaction involving alkyl halides

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

• acceptors and aldehydes [27][28][29][30][31][32], ketones [33], α-cyano esters [34][35], β-keto esters [35], β-keto acids [36], thiomalonates [37], nitroalkanes [38], oxindoles [39] and thiols [40] as Michael donors. There are only few examples of the use of sulfones as Michael donors in asymmetric addition

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• , nucleophilic fluorinating technique of β-keto esters 102 using 106/HF/m-CPBA as a catalytic system to access fluorinated β-keto esters 103 with moderate enantioselectivity [73]. β-Keto esters having sterically hindered adamantyl or menthyl groups lead to good selectivity. However, no further enhancement of ee

• oxylation of ketones reported by Masson et al. α-Fluorination of β-keto esters. Alkynylation of β-ketoesters and amides catalyzed by phase-transfer catalyst. Alkynylation of β-ketoesters and dearomative alkynylation of phenols. Acknowledgements The authors highly acknowledge the financial assistance

Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• transition metal catalyst Cu(OTf)2, Wu and co-workers achieved aerobic oxidative coupling of secondary amines with β-keto esters to form C(sp3)–C(sp3) bonds (Scheme 1) [18]. Although much advance has been made for the functionalization of glycine derivatives, most of these strategies mentioned above require

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

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

• short reaction times. In addition, this protocol was extended to β-keto esters, β-keto amides and α-cyano ketones. Selanyltriazoyl carboxylates, carboxamides and carbonitriles were synthesized in high yields at short times of reaction under very mild reaction conditions. Keywords: cycloadditions

• as a mixture of regioisomers (6:1) (Table 2, entry 10). In addition, the possibility to perform the reaction of 2-azidophenyl phenyl selenide (1a) with β-keto-esters, β-keto-amides and α-cyano-ketones 2f–k was also investigated. The reaction conditions optimized for 1,3-diketone 2a were employed, but

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

• 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

β-Amino functionalization of cinnamic Weinreb amides in ionic liquid

• Yi-Ning Wang,
• Guo-Xiang Sun and
• Gang Qi

Beilstein J. Org. Chem. 2016, 12, 2372–2377, doi:10.3762/bjoc.12.231

• , Grignard and organolithium reagents or ester enolates, the Weinreb amides can be easily converted into aldehydes, ketones, and β-keto esters, respectively [13][14][15][16][17][18][19][20]. Therefore, the transformation of β-amino Weinreb amides can provide a promising pathway towards the achievement of β

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

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• chirally pure α-amino ketones formed in this reaction are valuable building blocks in organic synthesis [37]. The NHC generated from the bicyclic pentafluoro triazolium salt promoted the chemoselective cross aza-benzoin reaction of aldehydes with N-PMP-imino esters to afford α-amino-β-keto esters in good

Asymmetric α-amination of β-keto esters using a guanidine–bisurea bifunctional organocatalyst

• Minami Odagi,
• Yoshiharu Yamamoto and
• Kazuo Nagasawa

Beilstein J. Org. Chem. 2016, 12, 198–203, doi:10.3762/bjoc.12.22

• Minami Odagi Yoshiharu Yamamoto Kazuo Nagasawa Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16, Naka-cho, Koganei city, 184-8588, Tokyo, Japan 10.3762/bjoc.12.22 Abstract An asymmetric α-amination of β-keto esters with azodicarboxylate in the

• presence of a guanidine–bisurea bifunctional organocatalyst was investigated. The α-amination products were obtained in up to 99% yield with up to 94% ee. Keywords: α-amination; bifunctional catalyst; guanidine; hydrogen-bonding catalyst; urea; Introduction Asymmetric α-amination of β-keto esters is an

• particular, catalytic asymmetric α-amination of β-keto esters has been widely explored, using both metal catalysts and organocatalysts [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. We have developed a series of guanidine–bis(thio)urea bifunctional organocatalysts, and have used them in a variety of