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

• generate a fluoride ion that facilitates limiting enolization processes, and an electrophilic N–F fluorinating agent that is reactive towards neutral enol species. Keywords: difluorination; difluoromethylene; direct fluorination; electrophilic fluorination; organofluorine; Introduction Fluorine is

• fluorine atoms per fluorinated drug, and fluorine is also present in the structures of 50% of marketed agrochemicals [4]. In the context of the research reported here, the incorporation of difluoromethylene (CF2) units into life science products is growing in importance and a number of commercially

• difluoromethylene units. To meet the demands of synthetic chemists within the life science discovery and manufacturing arenas, many fluorination methods have been developed over the years to introduce difluoromethylene groups into organic systems. Approaches using nucleophilic fluorination include halogen exchange

Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

• Yumei Wang,
• Guangzhu Wang,
• Yanping Zhu and
• Kaiwu Dong

Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20

• SHP2 inhibitor that has entered phase II clinical trials for the treatment of solid tumors and has been approved by the FDA as a rare drug for treating esophageal cancer (Figure 1) [4]. Among the fluoroalkyl moieties, the geminal difluoromethylene group has showcased its beneficial properties as an

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• . The scope of the bromination reaction was further extended with various alkyl bromides. As shown in Scheme 3, a series of activated alkyl bromides containing ester, difluoromethylene, benzyl motifs (2b–f), and unactivated alkyl bromides (2g–i) were evaluated in this reaction. Activated alkyl bromides

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• presents a difluoromethylene group (–CF2–) in the alpha position to the iodine, was performed (see Figure S3 in Supporting Information File 1). Even in this case, an important shift of the fluorine signal was observed. Thus, from a mechanistic point of view, the reaction is driven by the formation of a

Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)

• Yukiko Karuo,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167

• ) has been used as a fluorine-containing building block for the construction of trifluoromethyl and difluoromethylene motifs [1][2]. Such structures have been found in several multifunctional materials and biologically important molecules (Figure 1) [3][4][5][6][7]. The halothane structure contains two

• (s, 1F), −78.4 (s, 1F); EIMS m/z: 268, 270 [M]+; HREIMS: [M]+ calcd for C13H14ClFSi, 268.0486, 270.0457; found, 268.0490, 270.0452. Medicines containing a difluoromethylene group. Fluoroalkene analogs of some drugs. Reaction of phenol with polyfluoroalkanes. Proposed mechanism. Sonogashira cross

Cathodic generation of reactive (phenylthio)difluoromethyl species and its reactions: mechanistic aspects and synthetic applications

• Sadanobu Iwase,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2022, 18, 872–880, doi:10.3762/bjoc.18.88

• ; (phenylthio)difluoromethyl radical; Introduction Organofluorine compounds containing a difluoromethylene group have been of much interest from biological aspects since the difluoromethylene group is isopolar and isosteric with an ether oxygen [1][2]. Particularly, organic molecules bearing a (arylthio

• bearing a perfluoroalkyl or perfluoroacyl group [27][28][29][30]. Furthermore, they extended this methodology to tandem cyclization to provide fused difluoromethylene-containing heterocycles [31]. In consideration of these facts, we studied the cathodic reduction of 1 using a mediator. Indirect cathodic

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

Synthesis of aryl 2-bromo-2-chloro-1,1-difluoroethyl ethers through the base-mediated reaction between phenols and halothane

• Yukiko Karuo,
• Ayaka Kametani,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2021, 17, 89–96, doi:10.3762/bjoc.17.9

• agrochemical sciences because deliberately incorporated fluorine atoms often change the chemical properties of the parent molecules by improving the absorption, resistance to metabolism, and pharmacological activities. To date, difluoromethyl or difluoromethylene compounds have been studied extensively as well

• as monofluorinated and trifluoromethylated arenes or aliphatics [1][2][3][4]. Recent progress in difluoromethylene chemistry successfully led to the finding of bioactive compounds such as pantoprazole, a proton pump inhibitor [5], and AFP-07, a prostaglandin I2 receptor-selective agonist [6][7][8

• ], which suggests the importance of the difluoromethylene unit in drug discovery (Figure 1). There have been many reports for the construction of the difluoromethylene unit, such as the deoxygenating conversion of a carbonyl group to the difluoromethylene unit using N,N-diethylaminosulfur trifluoride (DAST

Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines

• Vladimir Kubyshkin

Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151

• trifluoromethyl- or a difluoromethylene group. This orientation of the substituents explains the observed trends in the pKa values, lipophilicity, and the kinetics of the amide bond rotation. The study also provides a set of evidences that the transition state of the amide-bond rotation in peptidyl-prolyl favors

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• (335; Scheme 53) [96]. The first Cu(I)-catalyzed allylic displacement on alkenes containing a CF3 group was reported in 2018. Enantioenriched γ,γ-gem-difluoroallylic boronates 339–341 can be obtained via this process. Once the obtained difluoromethylene scaffolds are formed, they are readily converted

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

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• -dependent manner the ability to induce the RNase H cleavage of the complementary RNA strand [35]. In continuation of our work we became interested in the fluorination of [4.3.0]bicyclo-DNA [36]. Consequently, the 6’-position of the [4.3.0]bicyclo-DNA was substituted with a difluoromethylene group, and the

• fluorine atoms had an effect on the C5’–C6’ and the C6’–C7’ bond length which were shorter than other C–C bonds in the cyclohexyl ring (Table S2, Supporting Information File 1). Furthermore, the difluoromethylene unit affected the C5’–C6’–C7’ angle and the F–C6’–F angle. The former was widened and the

• latter shortened compared to the structure of the non-fluorinated bc4,3-T (Table 2 and Table S3, Supporting Information File 1). This phenomenon was also observed for other difluoromethylene containing compounds [46]. Apart from that, the observed parameters of the 6’-diF-bc4,3-T were very similar to the

Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• organofluorine compounds in medicinal chemistry and related fields [1][2] have stimulated intensive developments of methods for their synthesis [3][4]. Though the major emphasis has long been placed on trifluoromethylated molecules, compounds bearing the difluoromethylene fragment have attracted increasing

Copper-catalyzed asymmetric methylation of fluoroalkylated pyruvates with dimethylzinc

• Kohsuke Aikawa,
• Kohei Yabuuchi,
• Kota Torii and
• Koichi Mikami

Beilstein J. Org. Chem. 2018, 14, 576–582, doi:10.3762/bjoc.14.44

• [1][2]. Therefore, the development of novel synthetic methods for the introduction of fluorinated fragments, such as trifluoromethyl (CF3), difluoromethyl (CF2H), and difluoromethylene (-CF2-), has attracted a great deal of attention from synthetic organic chemists [3][4][5][6]. Among these methods

Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

• Takeshi Fujita,
• Ryo Kinoshita,
• Tsuyoshi Takanohashi,
• Naoto Suzuki and
• Junji Ichikawa

Beilstein J. Org. Chem. 2017, 13, 2682–2689, doi:10.3762/bjoc.13.266

• elimination from 2a, 1,2-migration of the phenyl group, and deprotonation, followed by hydrolysis of the resulting doubly activated benzylic difluoromethylene unit (Scheme 2). Neither a combination of bis(pyridine)iodonium (IPy2BF4) and trifluoromethanesulfonic acid nor a combination of I2 and silver(I

• characterization of 6 was achieved by X-ray analysis using a single crystal of 6a (Figure 2), and it was found that the iodoarylation products 6 have a seven-membered carbocycle bearing adjacent difluoromethylene and iodomethylene units. In addition, a selective HI elimination from 6a could be achieved by the

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

• each other in a cyclohexane ring is introduced as a new design strategy which could be applicable to the preparation of polar hydrophobic cyclohexane motifs. Keywords: aliphatic rings; C–F bond; cyclohexane conformation; difluoromethylene group; organofluorine chemistry; Introduction Selective

• polar-hydrophobic properties [10]. Although selective mono-fluorination and CF3 incorporation have had wide currency, the difluoromethylene (CF2) motif has received relatively less attention despite possessing unique properties [11][12][13][14]. For example CH2F2 shows the highest molecular dipole (1.97

Computational study of productive and non-productive cycles in fluoroalkene metathesis

• Markéta Rybáčková,
• Jan Hošek,
• Ondřej Šimůnek,
• Viola Kolaříková and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2015, 11, 2150–2157, doi:10.3762/bjoc.11.232

• concentrated on the side chain of the vinyl group [24][25][26][27] or applications of 2-fluoroalkenes [28][29][30]. As an exception, the reaction of the Grubbs 2nd generation catalyst with 1,1-difluoroethene gave an isolable difluoromethylene-containing ruthenium complex with very poor catalytic activity [31

• with selected fluoro- and chloroalkenes has been studied and the higher stability of a ruthenium intermediate containing a difluoromethylene ligand has been emphasized [36][37]. A complete mechanism of alkene metathesis including initiation, productive and non-productive cycles represents a highly

• favourable. In contrast to the symmetrical molecule of ethene, two orientations of 1,1-difluoroethene are possible, which we arbitrarily assigned as syn for the coordination of difluoromethylene to ruthenium forming 2,2-difluororuthenacyclobutane intermediate s2I and anti for the coordinaton of methylene to

Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes

• Artem A. Zemtsov,
• Alexander D. Volodin,
• Vitalij V. Levin,
• Marina I. Struchkova and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2015, 11, 2145–2149, doi:10.3762/bjoc.11.231

• , unique stereoelectronic properties of the CF2-unit may be exploited in conformational analysis [3][4][5], carbohydrate and peptide research [6][7], and reaction engineering [8][9]. Typically, the difluoromethylene fragment is created by deoxyfluorination, which requires harsh or hazardous conditions [10

Lewis acid-promoted hydrofluorination of alkynyl sulfides to generate α-fluorovinyl thioethers

• Davide Bello and
• David O'Hagan

Beilstein J. Org. Chem. 2015, 11, 1902–1909, doi:10.3762/bjoc.11.205

• . When 70% HF·Py was employed, up to 70% conversion was achieved, but with over-fluorination to generate only the difluoromethylene thioether 4a (not isolated). In view of the lack of control with HF·Py attention turned to triethylamine trihydrogen fluoride (3HF·Et3N). This proved unsuccessful presumably

Deoxygenative gem-difluoroolefination of carbonyl compounds with (chlorodifluoromethyl)trimethylsilane and triphenylphosphine

• Fei Wang,
• Lingchun Li,
• Chuanfa Ni and
• Jinbo Hu

Beilstein J. Org. Chem. 2014, 10, 344–351, doi:10.3762/bjoc.10.32

• precursors for organic synthesis, but also act as bioisosteres for enzyme inhibitors. Among various methods for their preparation, the carbonyl olefination with difluoromethylene phosphonium ylide represents one of the most straightforward methods. Results: The combination of (chlorodifluoromethyl

• used in the design of potential enzyme inhibitors [4][5][6], since difluoromethylene functionality (CF2) is known to be isosteric and isopolar to an oxygen atom [7][8][9], and the gem-difluorovinyl functionality is believed to be a bioisostere for a carbonyl group [10]. More commonly, 1,1

• -difluoroalkenes, which are highly electrophilic towards many nucleophiles at the terminal difluoromethylene carbon [11], are used as valuable precursors of di- and trifluoromethyl compounds [10][12], monofluoroalkenes [13], monofluorinated heterocycles [14][15], carboxylic acids and esters [16]. Consequently

The difluoromethylene (CF₂) group in aliphatic chains: Synthesis and conformational preference of palmitic acids and nonadecane containing CF₂ groups

• Yi Wang,
• Ricardo Callejo,
• Alexandra M. Z. Slawin and
• David O’Hagan

Beilstein J. Org. Chem. 2014, 10, 18–25, doi:10.3762/bjoc.10.4

• in the extended anti-zig-zag chain and suggests a design modification for long chain aliphatics which can introduce conformational stability. Keywords: difluoromethylene; fatty acids; fluorination; organic fluorine chemistry; organo-fluorine; palmitic acid; Introduction The selective replacement of

• ]. The difluoromethylene (CF2) functionality has received considerably less attention as a functional group for modifying the properties of organic molecules, relative to –F and –CF3 groups. However we have recently become interested in the CF2 group, and in particular have noticed that the replacement

Cu-catalyzed trifluoromethylation of aryl iodides with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide

• Yuzo Nakamura,
• Motohiro Fujiu,
• Tatsuya Murase,
• Yoshimitsu Itoh,
• Hiroki Serizawa,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2013, 9, 2404–2409, doi:10.3762/bjoc.9.277

• organometallic reagents such as lithium and magnesium, which are widely utilized in non-fluorine organic synthesis, cannot be used. These trifluoromethyl metal reagents are generally too unstable to prepare even at low temperature because of facile α-fluoro elimination generating the singlet difluoromethylene

• 9% yield (Table 1, entry 7). The product 3a should be derived from CuCF2CF3 generated by an insertion of difluoromethylene (:CF2) decomposed from CuCF3 into CuCF3 [23]. Decreasing the loading of phen, the yield of product 2a was further increased to exceed the level of 90% yield (Table 1, entry 8

The preferred conformation of erythro- and threo-1,2-difluorocyclododecanes

• Yi Wang,
• Peer Kirsch,
• Tomas Lebl,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2012, 8, 1271–1278, doi:10.3762/bjoc.8.143

• . This structure has two distinct types of methylene group, those located at corners of the ring and those at edges. Recently we prepared and explored the conformation of cyclododecane ring systems carrying either one or two difluoromethylene (CF2) groups in place of methylenes (CH2) [7]. The study

Novel synthesis of pseudopeptides bearing a difluoromethyl group by Ugi reaction and desulfanylation

• Jingjing Wu,
• Hui Li and
• Song Cao

Beilstein J. Org. Chem. 2011, 7, 1070–1074, doi:10.3762/bjoc.7.123

• building block 2,2-difluoro-2-(phenylthio)acetic acid (2) as one component, followed by removal of the phenylsulfanyl protecting group in the presence of tributyltin hydride and azobisisobutyronitrile. Keywords: difluoromethyl functionality; gem-difluoromethylene-containing acid; pseudopeptides; reductive

• cleavage; Ugi reaction; Introduction Fluorinated amino acids and pseudopeptides have increasingly attracted attention in recent years [1][2][3][4][5]. The selective incorporation of fluorine-containing groups, such as trifluoromethyl, difluoromethyl and difluoromethylene, into peptides or peptidomimetics

• isosteric and isopolar to the hydroxyl group and can behave as a hydrogen donor through hydrogen bonding [13]. However, to date, most fluorine-containing peptide modifications involve the introduction of trifluoromethyl or difluoromethylene into molecules [14][15][16][17][18]. Only a few examples have been

Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

• Satoru Arimitsu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2010, 6, No. 48, doi:10.3762/bjoc.6.48

• -difluoromethylene moiety has been reported to improve their biological activities. For example, a gem-difluoro-γ-lactam can inhibit γ-lactamase, which is responsible for bacterial resistance to γ-lactam antibiotics [2][3][4]. Additionally, α,α-difluoro lactams are precursors of some biologically active compounds [5