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V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 143 (2012) 220–225
The intermediate zwitterion 11a undergoes intramolecular
3.1.2. Preparation of 4
transfer of a proton to the carbanion center, resulting in the
formation of unsaturated product 11. It should be pointed out that
an alternative mechanism of formation 11, involving a single
electron transfer process also cannot be ruled out at this point.
Clear, liquid compound 3 (27 g, 0.1 mol, purity >99%, NMR)
stored in glass sample vial crystallized over a three month period at
ambient temperature. According to NMR, the solid product was
compound 4 (purity >99%), m.p. 28–28.5 8C, yield quantitative.
Data of NMR spectroscopy and mass spectrometry for 4 are given
in Table 1.
3. Experimental
1H, 13C and 19F NMR spectra were recorded on a Bruker DRX-
500 (499.87 MHz) instrument using CFCl3 or TMS as internal
standards in CDCl3 as a lock solvent. GC and GC/MS analyses were
carried out on a HP-6890 instrument, using an HP FFAP capillary
column and either TCD (GC) or mass selective (GS/MS) detectors,
respectively. Dry DMF (99.8%, water – 100 ppm), 1,1-dimethox-
yethylene (ketene dimethylacetal, 2, assay 95.5%), 4 M solution of
HCl in 1,4-dioxane (Aldrich), aluminum powder (200 mesh, 99%,
3.1.3. The reaction of 3 with quadricyclane
The solution of 3.6 g (0.013 mol) of 3 and 2 g (0.022 mol) of
quadricyclane in 15 ml of dry DMF was kept in a glass sample vial
at ambient temperature. The progress of the reaction was
monitored by 1H and 19F NMR spectroscopy. The conversion of
3 was 32% (4 h), 70% (24 h), and 93% (48 h). After 72 h, the reaction
was complete, and the reaction mixture contained compounds 5
and 4 in a 9:1 ratio (NMR).
Aldrich),
sublimed
sulfur
(Alfa-Aesar,
99.5%),
1,1-bis
(methylthioethylene) (ketene dimethylthioacetal (9), TCI Amer-
ica), and quadricyclane (Exciton, 98%, remainder norbornadiene)
were obtained from commercial sources and used without further
purification. CsF (Aldrich) was dried at 100–120 8C under dynamic
vacuum for 4–8 h and was stored and handled inside a glove box.
Compound 1 was prepared according to a modified procedure
using CsF as a catalyst [3]. Compound 5 was identified by
comparison of NMR data to previously reported values [6]. Due to a
high ratio of sulfur to fluorine, elemental analysis were not
attempted for new materials, and the purity of all isolated
compounds established by GC and NMR spectroscopy was at
least 98%.
3.1.4. Preparation of 6
A mixture of 5.4 g (0.02 mol) 4, 0.64 g (0.02 mol) of sulfur, 0.1 g
(0.0007 mol) dry CsF, and 20 ml of dry DMF was agitated for 2 days
at 25 8C. The reaction mixture was diluted with 50 ml of water, and
extracted by hexane (30 ml  3). The combined organic layers
were washed with water (30 ml  3), dried over MgSO4, and then
the solvent was removed under vacuum. The crude product
(orange oil, 3.1 g, purity 96%) was identified as compound 6. No
further purification of 6 was attempted. Data of NMR spectroscopy
and mass spectrometry for 6 are given in Table 1.
3.1.5. Preparation of 7
After compound 3 (0.09 mol) was generated in 200 ml of DMF as
described in Ref. [3], and its formation was confirmed by NMR, 3.2 g
of sulfur was added to the reaction mixture (mildlyexothermic). The
reaction mixture was agitated at ambient temperature for 12 h, and
then it was diluted with 500 ml of water, and extracted with hexane
(100 ml  3). The combined organic layers were washed with water
(100 ml  3), dried over MgSO4, and then the solvent was removed
under vacuum. The crude product was distilled under vacuum to
give 23 g (78%) of 7, b.p. 65–67 8C/1.7 mm Hg, which crystallized on
standing. DataofNMR spectroscopyand massspectrometry for 7are
given in Table 1.
3.1. Crystallography
X-ray data for 4, 7, 10, 11 and 13 were collected at À100 8C
using a Bruker 1K CCD system equipped with a sealed tube
molybdenum source and a graphite monochromator. The struc-
tures were solved and refined using the Shelxtl [14] software
package, refinement by full-matrix least squares on F2, scattering
factors from Int. Tab. Vol. C Tables 4.2.6.8 and 6.1.1.4. Crystallo-
graphic data (excluding structure factors) for the structures in this
paper have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication nos. CCDC #799785–
799790. Copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
3.1.6. Preparation of 8
A solution of compound 3 (5.7 g, 0.021 mol) in 10 ml of dry DMF
was slowly added to a mixture of 1 g of Al powder activated by 0.2
of PbCl2 (see Ref. [4] for activation procedure) in 750 ml of dry DMF
at a rate sufficient to keep the internal temperature <35 8C. The
reaction mixture was agitated for 2 h at ambient temperature,
filtered, diluted with 200 ml of water, and extracted with hexane
(50 mlÂ). The combined organic layers were washed with water
(100 ml  3), dried over MgSO4, and then the solvent was removed
under vacuum. The crude product was distilled under vacuum to
give 2.8 g (65%) of 8, b.p. 86–89 8C/50 mm Hg. Data of NMR
spectroscopy and mass spectrometry for 8 are given in Table 1.
3.1.1. Preparation of 3
Method A: The solution of 1 in DMF was prepared using the
procedure described in Ref. [3], by bubbling 33 g (0.21 mol) of
hexafluoropropylene into a mixture of 200 ml of dry DMF, 6.4 g of
sulfur and 1.0 g (0.0065 mol) of dry CsF at 50–65 8C. After all the
sulfur dissolved, the reaction mixture was cooled to 25 8C, and 17 g
(0.19 mol) of 2 was added slowly keeping the internal temperature
of the reaction mixture <35 8C. After all of 2 was added, the
reaction mixture was agitated for 1 h, diluted by 500 ml of water,
and extracted by hexane (100 ml  3). The combined organic
layers were washed by water (200 ml  3), dried over MgSO4, and
then the solvent was removed under vacuum. The crude product 3
(50 g, purity 98%, containing 2% of isomer 4, NMR) was distilled
under vacuum to give 41 g (80%) of 3, b.p. 39–41 8C/2 mm Hg. Data
of NMR spectroscopy and mass spectrometry for 3 are given in
Table 1.
3.1.7. Preparation of 10
A solution of compound 9 (1.2 g, 0.01 mol) was added slowly to
a mixture of 1.9 g (0.0052 mol) of 1 and 0.1 g (0.0007 mol) of dry
CsF at 25–28 8C. The reaction mixture was agitated at ambient
temperature for 3 h, and then worked up as described above to give
2.4 g (80%) of slightly brown solid, m.p. 34–36 8C, identified as
compound 10 (purity 98%) by NMR.
Method B: Compound 2 (8.5 g, 0.096 mol) was added slowly to a
mixture of 1 (18.2 g, 0.05 mol) and 1 g (0.0065 mol) of dry CsF at
25–35 8C. The isolation of 3 was carried out as described in Method
A. After vacuum distillation, 42 g (82%) of compound 3 was
isolated.
3.1.8. Preparation of 11
To a solution of 10 g (0.028 mol) of 1 in 30 ml of dry DMF was
slowly added a solution of 2.5 g (0.028 mol) of 2 in 5 ml of DMF at
0–2 8C over ꢁ5 min. The reaction mixture was agitated at 2 8C for