The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• . Stereochemistry of the alcohol 58 was established by long-range 19F coupling to the cis-trimethylsilyl group hydrogens (JH-F = 0.9 Hz). Long-range 19F coupling to the TMS methyl groups of 58 was also observed in the 13C NMR spectrum (JC-F = 2.1 Hz) [64][65]. This long-range 19F coupling is not observed when the

Fluorine-containing substituents: metabolism of the α,α-difluoroethyl thioether motif

• Andrea Rodil,
• Alexandra M. Z. Slawin,
• Nawaf Al-Maharik,
• Ren Tomita and
• David O’Hagan

Beilstein J. Org. Chem. 2019, 15, 1441–1447, doi:10.3762/bjoc.15.144

• 19F NMR spectrum consistent with non-equivalence of the fluorines, immediately indicative of sulfoxide formation. Isolation and subsequent 1H and 19F NMR analyses as well as high-resolution mass spectrometry secured the identity of these metabolites as sulfoxides 6 and 7 and sulfone 8. The structure

• naphthalene ring, as summarised in Scheme 3. These metabolites were isolated by reversed-phase HPLC and characterised by 1H and 19F NMR and mass spectrometry. This identified sulfoxides 11 and 12 as the major metabolites and a trace amount of a minor sulfone which had the general structure 13 as determined by

• hydrolytic lability of the analogous oxygen ethers. By way of example α,α-difluoroethyl ether 14 [18] was incubated with cultures of C. elegans under the standardised conditions, as illustrated in Scheme 4. 19F NMR of the extract indicated a trace of residual starting material with one major metabolite which

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• stated in the procedure. NMR spectra were collected on a Bruker Ultrashield Plus/Avance II 400 MHz spectrometer. 1H NMR spectra were recorded at 400 MHz and 13C NMR spectra at 100 MHz with residual solvent signals as references. 19F NMR spectra were recorded at 376 MHz. Stereochemistry was assigned

• = 11.4 Hz, 7.2 Hz, 1H, H7), 3.69 (dd, J = 11.5 Hz, 4.6 Hz, 1H, H7), 3.60–3.49 (m, 4H); 13C NMR (100 MHz, CD3OD) δ 161.6, 146.2, 127.4, 127.3, 126.6, 122.4, 115.5, 115.3, 79.0, 78.6, 74.7, 69.4, 68.4, 61.5, 51.6; 19F NMR (376 MHz, CD3OD) δ −115.54; HRMS (m/z): [M + H]+ calcd for 340.1306; found, 340.1309

• ), 3.90 (dd, J = 2.9 Hz, 0.9 Hz, 1H, H5), 3.79 (dd, J = 11.2 Hz, 6.9 Hz, 1H, H7), 3.70 (dd, J = 11.6 Hz, 4.71 Hz, 1H, H7), 3.60–3.48 (m, 4H); 13C NMR (100 MHz, CD3OD) δ 164.5, 146.2, 132.9, 130.5, 122.9, 121.1, 114.4, 111.9, 78.9, 78.7, 74.7 69.4, 68.4, 61.5, 51.5; 19F NMR (376 MHz, CD3OD) δ −114.83; HRMS

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• nature of the halogen bond assembly. The crystal lattice of 1 contains two structurally different dimeric assemblies A and B, formally resulting in the mixture of a capsular dimer and a dimeric pseudo-capsule. 1H and 19F NMR analyses supports the existence of these halogen-bonded complexes and enhanced

• –NH2 protons of the NARXs are expected [32][33]. Additionally, NARXs are also known to cooperatively bind small guest molecules such as mono- and diamides [42][43]. Consequently, we used 1H and 19F NMR spectroscopy to study the XB assemblies formed between Hex-NARBr 1 and 1,4-diiodooctafluorobutane (5

• acetonitrile. The 1H and 19F NMR spectra of all these samples were recorded at 298 K and analyzed. In the 19F NMR analyses, the fluorine signals of the XB donor DIOFB were monitored. In all cases, minor upfield shifts of the fluorines on the terminal carbons were observed (0.12 ppm in 1·DIOFB, 0.13 ppm in 1

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

• Laize A. F. Andrade,
• Lucas A. Zeoly,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

• interactions (nN → σ*C–F), which can be demonstrated by means of 19F chemical shifts. The results were rationalized with the aid of theoretical calculations and natural bond orbital (NBO) analysis, allowing for the evaluation of competing steric, electrostatic and hyperconjugative interactions. Keywords

• enhance the fluoride character of the fluorine involved in such interaction. Because of the negative charge on the fluorine in the resonance structure derived from the generalized anomeric effect, a shielding effect is expected for this fluorine. The 19F NMR assignment of the diastereotopic fluorines was

• possible considering the 3JH,F(1) SSCC earlier reported, and comparing the 19F and 19F{1H} NMR experiments: the more shielded diastereotopic fluorine corresponds to Fpro-S, thus yielding 1b as the dominant conformation. Such a shielding effect decreases on going from cyclohexane (−89.4 ppm) to pyridine

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• achieved in the presence of Pd/C as a catalyst. Concomitant hydrogenolysis of two carbon–chlorine bonds also took place under these conditions and a 71:29 diastereomeric mixture of the monochloracetamides 19f/19’f was obtained (41%). The rather small difference of steric hindrance between the methyl and

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• leads to the selective formation of the desired 1,2-trans glycosidic linkages and can be easily removed at the end of the synthesis [7][8][36][42]. Moreover, 19F NMR experiments can be employed to assist in the analysis and monitoring of reactions involving N-TFA building blocks. First, we describe the

• -2C (δ = 4.50 ppm in 14α; δ = 3.52–3.43 ppm in 14β). The value of the coupling constant J1,2 in ring C confirmed the configuration of the new glycosidic linkage (J1,2 = 3.2 Hz in 14α; J1,2 = 8.2–8.5 Hz in 14β). 19F NMR spectra also showed clear differences in the chemical shifts for the

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

• compounds 3a–g and 5. Supporting Information File 522: Copies of 19F and 13C NMR spectra and LR mass spectra of compounds 3a–g and 5. Acknowledgements We are grateful to the Russian Science Foundation (grant No. 19-13-00272) for supporting the synthetic part of this work. Financial support for the NMR and

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• :2, rt, 19.5 h, 44%; f) CEP-Cl, DIPEA, THF, rt, 75 min, 43%. Tm and ΔTm/mod data from UV-melting curves (260 nm) of ON1–7 in duplexes with complementary DNA and RNA. Supporting Information Additional tables and figures, the experimental part, as well as copies of the NMR spectra (1H, 13C, 19F, 31P

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• at 400 MHz; 13C NMR at 101 MHz) or a JEOL–ECA500 spectrometer (19F NMR at 471 MHz). Chemical shifts are reported in ppm relative to the internal standard signal (0 ppm for Me4Si in CDCl3) for 1H NMR and the solvent signal (77.16 ppm for CDCl3) for 13C NMR. Data are presented as follows: chemical

• , 24.34, 24.29; 19F NMR (471 MHz, CDCl3) δ −126.3; HRMS–APCI+ (m/z): [M + H]+ calcd for C47H54FN2O8, 793.3859; found, 793.3859. Synthesis of bis(salen) (R,R,S,S)-8: The crude product was obtained from (S,S)-1,2-cyclohexanediamine monohydrochloride (28 mg, 0.19 mmol), 3-tert-butyl-5-fluoro-2

• ), 72.8, 72.0, 35.1, 35.0, 33.2, 33.0, 29.3, 29.1, 24.35, 24.29; 19F NMR (471 MHz, CDCl3) δ −126.3; HRMS–APCI+ (m/z): [M + H]+ calcd for C64H77F2N4O8+, 1067.5704; found, 1067.5697. Synthesis of bis(salen) (R,R,R,R)-8: The crude product was obtained from (R,R)-1,2-cyclohexanediamine monohydrochloride (0.10

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• corresponding product 19f-Me in good yield. Methyl, ethyl, and tert-butyl acrylates 18b, 18c, and 18d, respectively, also afforded the corresponding products. The product of the reaction with acrylamide 18e was also obtained. Scheme 19 shows a plausible reaction mechanism for this four-component coupling

Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex

• Henrike Ehrhorn,
• Janin Schlösser,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2018, 14, 2425–2434, doi:10.3762/bjoc.14.220

• from [NaW2Cl7(THF)5] [86]. The 13C and 19F NMR spectra are also consistent with literature values. Crystals of W2F3 suitable for X-ray diffraction analysis were obtained upon cooling a saturated pentane solution to −40 °C. Unfortunately, the crystal structure suffers from severe disorder. Each tungsten

• internal or terminal alkynes to isolate the corresponding alkylidyne complex. In an NMR study on the cleavage of the Mo≡Mo triple bond, in which Mo2F6 was treated with two equivalents of 1-phenyl-1-propyne, no signals corresponding to a possible molybdenum alkylidyne complex were detected in the 1H and 19F

• -like reaction, the W≡W bond is cleaved, with 2-butyne forming as a side product. Following this reaction by 1H and 19F NMR spectroscopy revealed fast and selective formation of WPhF3, and after 14 minutes, most of the starting material W2F3 was already consumed, with full conversion observed after 28

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

• Ken Tamamoto,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213

• 1.5 years in the refrigerator [35]. In order to examine the stability of 2-Zn in more detail, we quantitatively evaluated the thermal stability of 2-Zn under various temperature conditions (Figure 2). After a given duration, the recovery yield of 2-Zn was determined by 19F NMR analysis using an

• for Cu(I)-catalyzed cross-coupling reaction of 2-Zn with benzoyl chloride (5a). Supporting Information Supporting Information File 332: Experimental procedures, characterization data (1H, 13C, 19F NMR, IR and HRMS), copies of 1H, 13C and 19F NMR spectra.

Determining the predominant tautomeric structure of iodine-based group-transfer reagents by ¹⁷O NMR spectroscopy

• Nico Santschi,
• Cody Ross Pitts,
• Benson J. Jelier and
• René Verel

Beilstein J. Org. Chem. 2018, 14, 2289–2294, doi:10.3762/bjoc.14.203

• HCl compound 4a afforded an isolable iodonium-type structure [20]. Although this activation can be conveniently followed by 19F NMR spectroscopy with 4a resonating at −40.1 ppm and the fully protonated “iodonium” congener 4c at −20 ppm [1], this technique provides no indication on how to best

• then subjected to spectroscopic analysis. A 19F NMR chemical shift of −23.2 ppm was obtained, thereby confirming the presence of 4c. However, under these strongly acidic and activating conditions, the compound is unstable over a prolonged period of time (12 h). During the acquisition of the 17O NMR

Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• -oxyimidation product 3a from styrene 1a and N-hydroxyimide 2a a. Supporting Information Supporting Information File 213: Experimental procedures, characterization data, copies of 1H, 13C and 19F NMR spectra, copies of HRMS and FT-IR spectra and the ORTEP diagram and X-ray data for compound 3ca. Supporting

Diazirine-functionalized mannosides for photoaffinity labeling: trouble with FimH

• Femke Beiroth,
• Tomas Koudelka,
• Thorsten Overath,
• Stefan D. Knight,
• Andreas Tholey and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1890–1900, doi:10.3762/bjoc.14.163

• . This can be monitored by 19F NMR spectroscopy showing the typical diazirine CF3 signal around −68 ppm [29]. Whereas mannoside 3 was received in good purity, compound 4 was always obtained with contaminations. Thus, 3 was the preferred ligand for the following photolabeling experiments. Results obtained

• the peptides in a 1:1 ratio. After irradiation with UV light, two new signals were detected in nano-LC–ESIMS experiments in comparison to the original peptide spectra (Table 2). It should be noted that whereas we could monitor photodecomposition of the photolabels by 19F NMR spectroscopy (cf. [29

• ]), we could not observe labeled products by fluorine NMR. This is presumably due to the low labeling efficiency as in the literature 19F NMR spectra were obtained with proteins having 19F-labeled amino acids incorporated [30]. Disappointingly, instead of crosslinking, we observed two different other

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• ratio of amines and HF was important for obtaining reasonable yields. Indeed, excellent 19F NMR yields albeit lower isolated yields were obtained in this reaction (Scheme 12). In an attempt to induce enantioselectivity, the chiral aryl iodide derivative 39 only gave a moderate enantioselectivity (22% ee

Synthesis of trifluoromethylated 2H-azirines through Togni reagent-mediated trifluoromethylation followed by PhIO-mediated azirination

• Jiyun Sun,
• Xiaohua Zhen,
• Huaibin Ge,
• Guangtao Zhang,
• Xuechan An and
• Yunfei Du

Beilstein J. Org. Chem. 2018, 14, 1452–1458, doi:10.3762/bjoc.14.123

• product based on the analysis of its 19F NMR (δ −55.67). The above results from the experiment provided supportive evidence that the CF3 radical was likely involved as a reactive species in the reaction process. Based on this and previous reports [62][63][64][65][66][67][68], a possible reaction pathway

Hypervalent iodine(III)-mediated decarboxylative acetoxylation at tertiary and benzylic carbon centers

• Kensuke Kiyokawa,
• Daichi Okumatsu and
• Satoshi Minakata

Beilstein J. Org. Chem. 2018, 14, 1046–1050, doi:10.3762/bjoc.14.92

• solvents and reaction parameters on the decarboxylative acetoxylation.a Supporting Information Supporting Information File 166: Experimental procedures, characterization data, copies of the 1H, 13C, and 19F NMR spectra. Acknowledgements This work was supported by JSPS KAKENHI Grant Number JP16K17868.

Imide arylation with aryl(TMP)iodonium tosylates

• Souradeep Basu,
• Alexander H. Sandtorv and
• David R. Stuart

Beilstein J. Org. Chem. 2018, 14, 1034–1038, doi:10.3762/bjoc.14.90

• nucleophilicity. Supporting Information Supporting Information File 150: General experimental details, procedures, tabulated spectroscopic data, and 1H, 13C{1H}, and 19F NMR spectra of compounds 1g, 2a–i, and 3. Acknowledgements We acknowledge Portland State University for financial support of this research.

Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

• Felix Scheidt,
• Christian Thiehoff,
• Gülay Yilmaz,
• Stephanie Meyer,
• Constantin G. Daniliuc,
• Gerald Kehr and
• Ryan Gilmour

Beilstein J. Org. Chem. 2018, 14, 1021–1027, doi:10.3762/bjoc.14.88

• the cyclisation event, oxazoline 2r was generated from the corresponding α-chiral amide under standard conditions. Analysis of the crude reaction mixture by 19F NMR allowed a yield of >95% to be determined and a 1:1 dr. This is to be expected given the remote nature of the stereocentre. It is

• increased to 32 hours. Yields refer to isolated values whilst NMR yields are given in parentheses (19F NMR using ethyl fluoroacetate as an internal standard). X-ray molecular structure of compound 2c. Thermal ellipsoids shown at the 50% propability level. Torsion angle (F1–C10–C9–O1 −73.4°) consistent with

• the fluorine gauche effect. CCDC number 1815371. Exploring diastereocontrol and the synthesis of the fluorohydrin 3. Yields in parentheses were determined by 19F NMR using ethyl fluoroacetate as an internal standard. Unless otherwise stated, yields refer to isolated values. Optimisation of reaction

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

• organic layer was dried over anhydrous Na2SO4 and evaporated under reduced pressure (350 mmHg). The concentrated solution was used without purification for the next protection reaction. The yield of alcohol product 2 was determined by 19F NMR analysis using benzotrifluoride (BTF) as an internal standard

• determined by 19F NMR analysis. p-Nitrobenzoylated alcohol 2a’ was purified by silica-gel column chromatography (EtOAc/hexane 1:40) as a colorless liquid (53% yield for 2 steps, 89% ee). 1H NMR (300 MHz, CDCl3) δ 8.34–8.31 (m, 2H), 8.24–8.20 (m, 2H), 4.33 (q, 4H, J = 6.9 Hz), 1.97 (d, 3H, J = 0.9 Hz), 1.28

• (t, 3H, J = 7.0 Hz); 13C NMR (75 MHz, CDCl3) δ 164.3, 162.3, 151.1, 134.0, 131.2, 123.7, 122.7 (q, J C-F = 282.9 Hz), 80.7 (q, J C-F = 30.4 Hz), 63.2, 16.6, 13.8; 19F NMR (282 MHz, CDCl3) δ −78.4 (s, 3F); HRMS (APCI-TOF): [M]−· calcd for C13H12F3NO6, 335.0617; found, 335.0623; FTIR (neat, cm−1) 784

Synthesis and stability of strongly acidic benzamide derivatives

• Frederik Diness,
• Niels J. Bjerrum and
• Mikael Begtrup

Beilstein J. Org. Chem. 2018, 14, 523–530, doi:10.3762/bjoc.14.38

• 152–154 °C; 1H NMR (500 MHz, methanol-d4) δ 7.99 (dd, J = 9.0, 5.2 Hz, 2H), 7.29 (t, J = 8.8 Hz, 2H); 13C NMR (126 MHz, methanol-d4) δ 167.6 (d, J = 254.3 Hz), 166.0, 132.8 (d, J = 9.6 Hz), 129.1 (d, J = 3.1 Hz), 121.0 (q, J = 321.5 Hz), 117.1 (d, J = 22.7 Hz); 19F NMR (470 MHz, methanol-d4) δ −76.93

• 8.09 (d, J = 8.0 Hz, 1H), 7.86 (d, J = 8.1 Hz, 1H); 13C NMR (126 MHz, methanol-d4) δ 166.3, 136.5, 136.0 (q, J = 32.6 Hz), 130.6, 127.0 (q, J = 4.0 Hz), 125.0 (q, J = 271.9 Hz), 121.0 (q, J = 321.5 Hz); 19F NMR (470 MHz, methanol-d4) δ −64.31 (s, 3F), −77.06 (s, 3F); HRMS (TOF) m/z: [M − H]− calcd for

• ), 139.1 (dm, J = 250.0 Hz), 121.0 (q, J = 321.4 Hz), 111.9 (t, J = 17.6 Hz); 19F NMR (470 MHz, methanol-d4) δ −78.15 (s, 3F), −142.78 (d, J = 17.9 Hz, 2F), −152.25 (t, J = 19.2 Hz, 1F), −162.65 (t, J = 18.3 Hz, 2F); HRMS (TOF) m/z: [M − H]− calcd for C8F8NO3S−, 341.9477; found, 341.9520. 4-Bromo-N

The selective electrochemical fluorination of S-alkyl benzothioate and its derivatives

• Shunsuke Kuribayashi,
• Tomoyuki Kurioka,
• Shinsuke Inagi,
• Ho-Jung Lu,
• Biing-Jiun Uang and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2018, 14, 389–396, doi:10.3762/bjoc.14.27

• -(ω-carboxy)alkyl benzothioates afforded intramolecular cyclization products like lactones instead of the corresponding α-fluorinated products. Experimental General information 1H, 13C and 19F NMR spectra were recorded on a JEOL JNM EX-270 (1H: 270 MHz, 13C: 67.8 MHz, 19F: 254.05 MHz) spectrometer in

• CDCl3. The chemical shifts for 1H, 13C and 19F NMR spectra are given in δ (ppm) from internal TMS, CDCl3 and monofluorobenzene, respectively. Cyclic voltammetry was performed using an ALS Instrument model 600A. Preparative electrolysis experiments were carried out with Metronnix Corp. (Tokyo) constant

• /EtOAc (20:1 to 1:1) as an eluent. The yield of the fluorinated products were estimated by 19F NMR using monofluorobenzene as an internal standard. The known fluorinated products, benzoyl fluoride [39], p-chlorobenzoyl fluoride [40] and p-fluorobenzoyl fluoride [41] were identified by comparison with 19F

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes

• Anna-Lena Dreier,
• Andrej V. Matsnev,
• Joseph S. Thrasher and
• Günter Haufe

Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25

• addition of ice-water. After work-up 22% of the aldol addition products were formed in a syn/anti-ratio of 97:3 as determined by 19F NMR spectroscopy (Scheme 1). Subsequently, the reaction conditions were optimized (Table 1). Elevation of the reaction temperature (15 h reflux) led to an increase of the

• , entry 13), while 2-bromo-, 2,6-dichloro- and 2,4-dinitrobenzaldehydes failed to give any aldol products (Table 2, entries 14–16). Besides the starting materials, only minor amounts of SF5-containing side products of unknown structure were detected in the 19F NMR spectra of the crude product mixtures

• chromatography (Scheme 3). In order to ascertain the configuration of our products, we performed a heteronuclear Overhauser effect (1H,19F-correlation spectrum (gHOESY), see Supporting Information File 1 for a copy of the spectrum). From this spectrum it becomes clear that the four equatorial fluorine atoms do