V. Petrov, W. Marshall
JournalofFluorineChemistry207(2018)1–6
washing commercially available MCPBA (Aldrich, 55–70%) with buffer
pH 7 and drying in desiccator under vacuum, over P2O5 Compound 1
[16,18], 1b [21] and 2–4 [22] was prepared according reported pro-
cedures.
26.01. C9H8F3NO2. Found. C, 49.09, H, 3.80, N, 6.61, F, 25.84.
Compound 3a: Using 9 g (0.033 mol) of 3, 24 g + 9 g of MCPBA and
150 ml of CH2Cl2. It was isolated 7.3 g (72% yield) of 3a, B.P. 66.5-
67.5/0.15 mm Hg. Calc. (%): C, 44.62, H, 3.00, N, 5.20, F, 35.29.
C
10H8F5NO2. Found. (%): C, 44.32, H, 2.88, N, 5.03, F, 35.04.
4.1. Crystallography
Compound 4a: Using 6.1 g (0.021 mol) of 4, 8 g + 3 g of MCPBA
and 40 ml of acetonitrile. It was isolated 1.5 g (24% yield) of 4a, b.p.
82–83/0.15 mm Hg, crystallized on standing at ambient temperature.
Calc. (%): C, 41.39, H, 2,53, N, 4.39, F, 41.67. C11H8F7NO2. Found. (%):
C, 41.17, H, 2.40, N, 4.47, F, 41.58.
X-ray data for 4a were collected at −100° C using a Bruker 1 K CCD
system equipped with a sealed tube molybdenum source and a graphite
monochromator. The structure was solved and refined using the Shelxtl
[25] software package, refinement by full-matrix least squares on F2,
scattering factors from Int. Table Vol. C Tables 4.2.6.8 and 6.1.1.4.
Crystallographic data (excluding structure factors) for the structure in
this paper have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication nos. CCDC #1584646. Co-
pies of the data can be obtained, free of charge, on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44 1223 336033 or e
mail: deposit@ccdc cam ac uk
4.1.3. Oxidation of hydrocarbon substrates by 1a (NMR experiments)
In 5 mm NMR tube it was placed 0.3- 0.5 ml of CDCl3, ∼ 0.1-0.2 g of
organic substrate. NMR tube was cooled down to ∼–50 °C and ∼ 0.1 g
of oxaziridine 1a was added and tube allowed to warm up to ambient
temperature with occasional shaking (∼10 min). 1H and 19FNMR
spectra were taken within 1–2 h. In all cases complete conversion of
oxaziridine 1a was observed. Oxidation products
− Ph3P = O,
(CH3)3SO2, 7-oxa-bicyclo[4.1.0]heptane, acetaldehyde and cyclo-
hexene oxide were identified by comparison with authentic samples
(NMR).
4.1.1. Preparation of oxaziridines 1a and 1c
Into 50 ml three-neck round bottomed flask, equipped with ther-
mocouple, dry ice condenser, addition funnel and magnetic stir bar it
was placed 3–5 g of dry MCPBA and 20–30 ml of dry acetonitrile (ACN)
was added to the flask using syringe. The mixture was agitated for
5 min at ambient temperature, precooled to ∼5 °C and the corre-
sponding imidoyl fluoride (2–3 g) was added dropwise as a liquid.
Agitated reaction mixture was allowed to warm to ambient tempera-
ture. After 2 h at 22–25 °C (15 min at 0–3 °C in case oxidation of 1b) the
dry ice condenser and addition funnel were removed and the reaction
vessel was connected to vacuum source through cold (–78 °C) trap. The
mixture of the product and ACN was collected in cold trap at
50–300 mm Hg. It was washed with iced water (100 ml x 2) to remove
ACN, organic layer was separated and dried over MgSO4.
4.1.4. Hydrogenation of compound 2
A mixture of 20 g (0.11 mol) of 2, 100 ml of dry THF and 2 g of 5%
Pd on alumina was placed in 400 ml Hastelloy shaker tube, it was
cooled down with dry ice, evacuated and pressurized with 300 psi of
H2. The reactor was warmed up to ambient temperature and was kept
agitated at this temperature for 12 h. It was vented and unloaded. The
reaction mixture was filtered through CeliteR to remove the catalyst.
According 1H and 19F NMR only compound 2a was present in the crude
reaction mixture. The solvent was removed under reduced pressure and
the residue was distilled to give 12.8 g (64% yield) of 2a, b.p. 66 °C/
14 mm Hg, purity 99.9% (GC, NMR). NMR and MS data of 2a are given
Compound 1a: Using 5 g of 1. It was isolated 3 g (60% yield) of 1a
(purity 98%, 2% of ACN, NMR, and GC); NMR, MS and IR data are
4.1.5. Partial oxidation of 4
Compound 1c: yield 52%; Prepared using 2 g of 1b at 0–3 °C for
15 min, followed by vacuum transfer in −78 °C cold trap at 150 to
50 mm Hg, ∼20 min); after washing and drying by MgSO4 it was iso-
lated 1.1 g (52%) of 1c (99% purity, 1% ACN) NMR, MS and IR data for
To a well agitated mixture of 1.6 g dry MCPBA and 10 ml of CH2Cl2
it was added 1 g of 4 at +10 °C. The reaction mixture was warmed up to
ambient temperature and kept for 16 h According 1H and 19F NMR of
crude reaction mixture all starting material was converted at this point.
Precipitate was filtered off, organic layer was washed with sodium
thiosulfate (50mlx2) and saturated solution of NaHCO3 (50mlx2), dried
over MgSO4 and solvent was removed under reduced pressure. The
residue (oil) was left at ambient temperature for 24 h, white solids
which precipitated were filtered of and the residue (0.8 g) was analyzed
by GC/MS and 1H NMR and was shown to be a mixture of 4a and 4b in
ratio 85:15. NMR and MS data of 4b are given in Table 1.
4.1.2. Preparation of oxaziridines 2b, 3a and 4a
Into a 250 ml three-neck round bottomed flask (equipped with
thermocouple, dry ice condenser, addition funnel and magnetic stir bar
it was placed 8–24 g of MCPBA and 70–110 ml of the corresponding
solvent was added (ACN for oxidation of 4 and CH2Cl2 for oxidation of
2 and 3). The reaction mixture was agitated for 5 min at ambient
temperature, precooled to 10–15 °C and the corresponding imine
(6–9 g) was added dropwise as a liquid. Agitated reaction mixture was
allowed to warm to ambient temperature and temperature was kept
under 29 °C by occasional cooling of the reaction mixture. After 18–20 h
at 22–25 °C, the conversion of the imine was checked by NMR and
another portion of MCPBA (3–9 g) was added in case, if the oxidation
was not competed. The reaction mixture was agitated at ambient
temperature for another 5–6 h. The reaction mixture was cooled down
to 5 °C, filtered, washed several times with sodium thiosulfate, until
peroxide test was negative (starch paper; in case of 2b the reaction
mixture after water addition was extracted by CH2Cl2), 10% solution of
sodium bicarbonate (100mlx3) and dried over MgSO4. Solvent was
removed under reduced pressure affording crude product, which typi-
cally contained 1–3% of m-chlorobenzoic acid. Pure 2b, 3a and 4a were
isolated by distillation under reduced pressure.
Acknowledgements
Authors would like to thank Dr. R. Wheland for providing a sample
of purified perfluoro-N-methylmorpholine, Dr. V. Grushin for helpful
discussion, reviewers 2 and 3 for helpful suggestions and J. Buriak for
technical assistance
References
Compound 2b: Using 9 g (0.048 mol) of 2, 22 g + 5 g of MCPBA and
150 ml of CH2Cl2. After distillation it was isolated 5.6 g (54% yield) of
2b, b.p. 62.5-63/0.15 mm Hg. Calc.: C, 49.32, H, 3.68, N, 6.39, F,
5