Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of β-ketoesters

• Wen-Bin Yi,
• Xin Huang,
• Zijuan Zhang,
• Dian-Rong Zhu,
• Chun Cai and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 1233–1240, doi:10.3762/bjoc.8.138

• electrophilic reaction with Selectfluor (F-TEDA-BF4, 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)), as developed by Bank [7][8][9]. The Cahard [10][11][12] and Shibata [13][14] groups combined cinchona alkaloids and Selectfluor for asymmetric fluorination of substrates such as

• imido-protected phenylglycines (up to 94% ee), indanones and tetralones (up to 91% ee), ethyl α-cyanotolyl acetates (up to 87% ee), and cyclic β-ketoesters (up to 80% ee) [15]. A catalytic approach for the cinchona alkaloids and Selectfluor combinations has also been developed [16]. The Togni group

• employed chiral titanium Lewis acid TiCl2(TADDOLate) for the asymmetric fluorination of β-ketoesters (up to 96% ee) [17][18][19][20]. Most Selectfluor-promoted asymmetric fluorinations require a stoichiometric amount of chiral promoters to suppress the competitively direct achiral fluorination. Different

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• glacial acetic acid (Scheme 1) [25]. Treatment of bromide 3 with Zn and N-methylimidazole [26] afforded the protected maltal derivative 4, which was transformed to the target compounds by utilizing Selectfluor® as a fluorinating agent [23][27][28] in a nitromethane solution. The mixture of anomeric 2

• relaxation filter. Syntheses of maltose derivatives; reagents and conditions: (a) Ac2O, Pyr, 97%; (b) HBr, AcOH, 99%; (c) Zn, N-methylimidazole, ethyl acetate, 74%; (d) Selectfluor®, CH3NO2, 40%; (e) NaOMe, MeOH, 99%; (f) NH2NH2·HOAc, DMF, 94%; (g) DAST, CH2Cl2, 89%; (h) NaOMe, MeOH, 99%; (i) α,α

Combination of gold catalysis and Selectfluor for the synthesis of fluorinated nitrogen heterocycles

• Antoine Simonneau,
• Pierre Garcia,
• Jean-Philippe Goddard,
• Virginie Mouriès-Mansuy,
• Max Malacria and
• Louis Fensterbank

Beilstein J. Org. Chem. 2011, 7, 1379–1386, doi:10.3762/bjoc.7.162

• the synthesis of 3-fluoro-2-methylene-pyrrolidine (3a) and -piperidine (3b) from 1,5- and 1,6-aminoalkynes, respectively, using a combination of a gold-catalyzed hydroamination reaction followed by electrophilic trapping of an intermediate cyclic enamine by Selectfluor. Careful attention was paid to

• the elucidation of the mechanism and Selectfluor was suggested to play the double role of promoting the oxidation of gold(I) to a gold(III) active species and also the electrophilic fluorination of the enamine intermediates. Keywords: cycloisomerization reactions; fluorinated pyrrolidines; gold

• catalysis; Selectfluor; Introduction The useful properties of fluorinated compounds in medicinal chemistry have motivated an intense effort towards the synthesis of new molecules bearing fluorine substituents [1][2]. Therefore, the development of a rapid access to C–F bonds is of great importance. Quite

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• (Scheme 53). The latter is the first example of a gold-catalyzed intramolecular C–C cross-coupling reaction involving aryl C–H functionalization with Selectfluor® as the oxidant. 2,4-Dien-6-ynecarboxylic acids 316 undergo gold-catalyzed tandem 1,6-cyclization/decarboxylation to afford 2,3-disubstituted

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions

• Deyun Qian and
• Junliang Zhang

Beilstein J. Org. Chem. 2011, 7, 808–812, doi:10.3762/bjoc.7.92

• existence of Au(I)/Au(III) catalytic cycles [26][27][28][29][30][31][32]. For instance, Zhang and co-workers have developed a gold-catalyzed oxidative cross-coupling reaction of arylboronic acids with propargyl esters [27], and Selectfluor® – a source of electrophilic fluorine – was used to oxidize the

• presence of oxidant (Selectfluor®) and base, and undergo a Au(I)/Au(III)-catalyzed Sonogashira-type cross-coupling reaction (Scheme 1). Results and Discussion We embarked on developing a general protocol for Sonogashira-type cross-coupling by using propargyl tosylamide (1a) and phenylboronic acid as the

• efficiency was quite low (Table 1, entries 4, 5). Without Selectfluor® as additive, the cross-coupling reaction did not occur (Table 1, entry 6), indicating that it was crucial for this transformation via oxidation of gold(I) to the gold(III) species [26][27][28][29][30][31][32]. Reducing the amount of

Efficient 1,4-addition of α-substituted fluoro(phenylsulfonyl)methane derivatives to α,β-unsaturated compounds

• G. K. Surya Prakash,
• Xiaoming Zhao,
• Sujith Chacko,
• Fang Wang,
• Habiba Vaghoo and
• George A. Olah

Beilstein J. Org. Chem. 2008, 4, No. 17, doi:10.3762/bjoc.4.17

• fluorinating bis(phenylsulfonyl)methane, which is commercially available [11]. Our strategy for the preparation of monofluoro methanes was to use commercially available Selectfluor® [35] as the electrophilic fluorine source. The monofluorination of (nitromethylsulfonyl)benzene with Selectfluor® under the

• improved conditions [36] [treatment of (nitromethylsulfonyl)benzene (6.75 mmol) with NaH (6.75 mmol) in THF (25 mL) followed by Selectfluor® (6.75 mmol) in 15 mL of DMF at 0 °C] gave [fluoro(nitro)methylsulfonyl]benzene 3a in 62% isolated yield (Table 1, entry 1). A doublet was observed at δ −142.16 ppm in

DBFOX- Ph/metal complexes: Evaluation as catalysts for enantioselective fluorination of 3-(2-arylacetyl)-2-thiazolidinones

• Takehisa Ishimaru,
• Norio Shibata,
• Dhande Sudhakar Reddy,
• Takao Horikawa,
• Shuichi Nakamura and
• Takeshi Toru

Beilstein J. Org. Chem. 2008, 4, No. 16, doi:10.3762/bjoc.4.16

• reactions. Stoichiometric approaches based on cinchona alkaloid/Selectfluor® combinations [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], chiral ligand/metal-catalyzed [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] or organocatalytic [58

Themed series in organo- fluorine chemistry

• David O'Hagan

Beilstein J. Org. Chem. 2008, 4, No. 11, doi:10.3762/bjoc.4.11

• enabling elemental fluorine to be used in large scale organo-fluorine production [4]. The introduction in the early 1990's of air stable electrophilic fluorinating reagents such as Selectfluor [5] has been revolutionary and has opened up many new methods for fluorine introduction, and provided the

Single and double stereoselective fluorination of (E)-allylsilanes

• Marcin Sawicki,
• Angela Kwok,
• Matthew Tredwell and
• Véronique Gouverneur

Beilstein J. Org. Chem. 2007, 3, No. 34, doi:10.1186/1860-5397-3-34

• Selectfluor. These reactions proceeded with efficient transfer of chirality from the silylated to the fluorinated stereocentre. Upon double fluorination, an unsymmetrical ethyl syn-2,5-difluoroalk-3-enoic ester was prepared, the silyl group acting as an anti stereodirecting group for the two C-F bond forming

• temperature in CH3CN in the presence of 1.0 eq. of NaHCO3 and 1.5 eq. of Selectfluor [1-chloromethyl-4-fluoro-1,2-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)]. The reactivity of the (E)-allylsilanes 1a-d possessing a single stereogenic centre was surveyed in priority to probe how structural variations

• 2e was formed in 95% yield as a diastereomeric mixture of both syn-2e and anti-2e isomers. The high d.r. [19:1] suggested that the transfer of chirality (anti approach of Selectfluor) from the silylated to the fluorinated stereocentre was very efficient. A third allylic fluoride was detected in the