M.J. Mitcheltree et al. / Tetrahedron 69 (2013) 5634e5639
5637
were recorded at 75, 100 or 125 MHz at 24 ꢀC, unless otherwise
noted. Chemical shifts are expressed in parts per million (ppm,
scale) downfield from tetramethylsilane, and are referenced to the
carbon resonances of the solvent (CDCl3, 77.16; CD3OD, 49.00;
(CD3)2SO, 39.52). Distortionless enhancement by polarization
transfer (DEPT-135) spectra were recorded at 100 or 125 MHz at
24 ꢀC unless otherwise noted. 13C NMR and DEPT-135 data are
combined and represented as follows: chemical shift, carbon type
(obtained from DEPT-135 experiments). Fluorine nuclear magnetic
resonance (19F NMR) spectra were recorded at 282 MHz at 24 ꢀC
unless otherwise noted. Chemical shifts are expressed in parts per
13C NMR (125 MHz, CD3OD),
d
186.0 (C), 50.0 (C), 31.4 (CH2), 26.9
(CH2). 19F NMR (282 MHz, CD3OD),
d
ꢁ82.5 (3F), ꢁ114.0 (2F), ꢁ122.3
d
(2F), ꢁ127.2 (2F). FTIR (thin film), cmꢁ1: 3492.5 (br), 2959.4 (m),
2873.3 (w),1652.0 (s),1620.5 (m),1290.0 (s),1189.7 (s). LC/HRMS-ESI
(m/z): [MþH]þ calcd for C10H10F9NO3S, 396.0310; found 396.0311.
d
d
d
4.5.2. 1-Methyl-N-((perfluorobutyl)sulfonyl)cyclopentanecarboxamide
(6b). White solid. 1H NMR (400 MHz, CD3OD),
d
2.21e2.14 (m, 2H),
1.68e1.61 (m, 4H),1.40e1.35 (m, 2H).1.20 (s, 3H).13C NMR (100 MHz,
CD3OD),
189.2 (C), 54.0 (C), 39.0 (CH2), 26.2 (CH3), 26.0 (CH2). 19
NMR (282 MHz, CD3OD),
d
F
d
ꢁ82.5 (3F), ꢁ114.5 (2F), ꢁ122.1 (2F),
million (ppm,
d
scale) downfield from CFCl3. Data are represented as
ꢁ127.2 (2F). FTIR (thin film), cmꢁ1: 2961.7 (m), 2876.6 (w),1641.7 (s),
1467.1 (w), 1195.1 (s), 1133.5 (s). LC/HRMS-ESI (m/z): [MþH]þ calcd
for C11H12F9NO3S, 410.0467; found 410.0465.
follows: chemical shift, and integration. Attenuated total reflectance
Fourier transform infrared (ATR-FTIR) spectra were obtained using
a Thermo Electron Corporation Nicolet 6700 FTIR spectrometer
referenced to a polystyrene standard. Data are represented as fol-
lows: frequency of absorption (cmꢁ1), and intensity of absorption
(s¼strong, m¼medium, w¼weak, br¼broad). High-resolution mass
spectrometry (HRMS) data were obtained on a Waters analytical
ultra high-performance liquid chromatographyemass spectrome-
try (UPLC/HRMS) instrument equipped with an electrospray ioni-
zation (ESI) mass spectrometry detector and photodiode-array
detector; otherwise, HRMS spectra were obtained by chemical
ionization (CI) at the W. M. KeckFoundation Biotechnology Resource
Laboratory at Yale University. In the first case, UPLC/HRMS samples
4.5.3. N-((Perfluorobutyl)sulfonyl)cyclopent-2-enecarboxamide
(6c). White solid. 1H NMR (400 MHz, CD3OD),
d
5.80 (m, 1H), 5.76
(m, 1H), 3.48 (tdd, J¼8.8, 4.9, 2.4 Hz, 1H), 2.47e2.38 and 2.34e2.25
(m, 2H), 2.16e1.99 (m, 2H). 13C NMR (125 MHz, CD3OD),
184.1 (C),
133.1 (CH), 131.9 (CH), 56.77 (CH), 33.20 (CH2), 27.88 (CH2). 19F NMR
d
(282 MHz, CD3OD),
d
ꢁ82.5 (3F), ꢁ114.0 (2F), ꢁ122.4 (2F), ꢁ127.2
(2F). FTIR (thin film), cmꢁ1: 3471.3 (br), 1605.3 (m), 1285.7 (s),
1194.5 (s), 1135.3 (s), 1010.1 (m). LC/HRMS-ESI (m/z): [MþH]þ calcd
for C10H8F9NO3S, 394.0154; found 394.0160.
were eluted over a reverse-phase C-18 column (1.7
m
m particle size,
4.5.4. (1R,5S)-2-Methyl-N-((perfluorobutyl)sulfonyl)-5-(prop-1-en-
2-yl)cyclopent-2-enecarboxamide (6d). White Solid. 1H NMR
2.1ꢂ50 mm) with a linear gradient of 5% acetonitrileewater (v/v) to
95% acetonitrileewater (v/v) containing 0.1% formic acid over 3 min
at a flow rate of 0.8 mL/min.
(400 MHz, CD3OD),
(app t, J¼6.5 Hz, 1H), 2.57e2.49 and 2.24e2.17 (m, 2H), 1.71 (s, 6H).
13C NMR (75 MHz, CD3OD),
184.4 (C), 148.8 (C), 140.5 (C), 126.9
(CH), 110.0 (CH2), 64.6 (CH), 51.9 (CH), 37.9 (CH2), 20.7 (CH3), 15.4
d 5.42 (br, 1H), 4.76 (br, 1H), 4.68 (br, 1H), 3.27
d
4.4. Procedure for the preparation of perfluoro-n-butane-
sulfonyl azide (nonaflyl azide, NfN3)
(CH3). 19F NMR (282 MHz, CD3OD),
d
ꢁ82.5 (3F), ꢁ113.9 (2F), ꢁ122.3
(2F), ꢁ127.3 (2F). FTIR (thin film), cmꢁ1: 3439.1 (br), 2979.1 (w),
1605.0 (s), 1299.7 (s), 1197.0 (s). LC/HRMS-ESI (m/z): [MþNa]þ calcd
for C14H14F9NO3S, 470.0443; found 470.0439.
A 50-mL round-bottomed flask was charged with a magnetic stir
bar, sodium azide (880 mg, 13.6 mmol, 1.00 equiv) and anhydrous
methanol (15 mL). To this mixture was added per-
fluorobutanesulfonyl fluoride (NfF, 4.10 g, 13.6 mmol, 1 equiv) and
the mixture was stirred for 18 h at 23 ꢀC behind a blast shield. The
mixture was then passed over a fritted glass funnel to remove solid
precipitate. The filtrate was collected in a 75-mL pear-shaped flask,
and the filtrate was shaken with 20 mL of deionized water. The
fluorous phase was collected and passed over a plug of sodium
sulfate to afford neat nonaflyl azide as a colorless oil (2.16 g, 49%).19F
NMR and IR spectral data were in agreement with those reported.11
4.5.5. trans-N-((Perfluorobutyl)sulfonyl)-2-vinylcyclopentanecarbo-
xamide and cis-N-((perfluorobutyl)sulfonyl)-2-vinylcyclopentane-
carboxamide (trans-6e and cis-6e, inseparable mixture). trans-6e:
1H NMR (500 MHz, CD3OD),
d
5.81 (ddd, J¼17.4, 10.3, 7.2 Hz, 1H),
5.01 (app d, J¼17.2 Hz, 1H), 4.89 (dd, J¼10.5, 2.0 Hz, 1H). 2.78 (m,
1H), 2.44 (app q, J¼8.7 Hz, 1H), 1.99e1.39 (m, 6H). 13C NMR
(100 MHz, CD3OD),
d 185.9 (C), 142.7 (CH), 113.8 (CH2), 56.6 (CH),
49.61 (CH), 33.7 (CH2), 32.1 (CH2), 25.4 (CH2). 19F NMR (282 MHz,
CD3OD),
d
ꢁ82.5 (3F), ꢁ114.3 (2F), ꢁ122.2 (2F), ꢁ127.2 (2F). FTIR
4.5. General procedure for the ring contraction of
enoxysilanes
(thin film), cmꢁ1: 3478.9 (br), 2956.0 (m), 1638.3 (s), 1351.4 (m),
1209.2 (s). LC/HRMS-ESI (m/z): [MþH]þ calcd for C12H12F9NO3S,
422.0467; found 422.0461. cis-6e: 1H NMR (500 MHz, CD3OD),
A flame-dried 10-mL round-bottomed flask that had been fused
to a Teflon-coated valve was charged with a solution of per-
d
5.90 (ddd, J¼17.2, 10.2, 8.1 Hz,1H), 5.01 (app d, J¼17.2 Hz,1H), 4.88
(app d, J¼10.3 Hz, 1H), 2.84 (app q, J¼7.6 Hz, 1H), 2.78 (m, 1H),
1.99e1.57 (m, 6H). 13C NMR (100 MHz, CD3OD),
184.4 (C), 140.6
(CH), 114.7 (CH2), 54.6 (CH), 49.2 (CH), 33.0 (CH2), 29.3 (CH2), 24.9
fluorobutanesulfonyl azide (44.9 mg, 138
tonitrile (420 L). To this solution was added the enoxysilane
(126
mol, 1 equiv) at 23 ꢀC. The reaction vessel was then sealed
and heated for 3 h at 40 ꢀC. The mixture was then cooled to 23 ꢀ
mmol, 1.10 equiv) in ace-
d
m
m
(CH2). 19F NMR (282 MHz, CD3OD),
d
ꢁ82.5 (3F), ꢁ114.3 (2F), ꢁ122.2
C
(2F), ꢁ127.2 (2F). FTIR (thin film), cmꢁ1: 3478.9 (br), 2957.0 (m),
1638.3 (s), 1351.4 (m), 1209.2 (s). LC/HRMS-ESI (m/z): [MþH]þ calcd
for C12H12F9NO3S, 422.0467; found 422.0461.
and the solvent was removed by evaporation under a stream of
nitrogen gas. The residue obtained was purified by flash-column
chromatography (eluting with dichloromethane initially, grading
to 50% ethyl acetateedichloromethane over two-steps). Fractions
containing product were identified using TLC (50% ethyl aceta-
teedichloromethane, KMnO4 stain). All N-acyl sulfonamide prod-
ucts thus afforded (6aei; 8aec) featured Rf values of 0.10e0.20 in
50% ethyl acetateedichloromethane.
4.5.6. 2-Methyl-N-((perfluorobutyl)sulfonyl)-2-vinylcyclopent-anec-
arboxamide (6f, inseparable mixture, stereochemistry not determined,
* designates other diastereomer). 1H NMR (400 MHz, CD3OD),
d 6.02
(dd, J¼10.7, 17.5 Hz, 1H, 1H*), 4.99 (dd, J¼1.2, 17.5 Hz, 1H*), 4.98 (dd,
J¼1.32, 17.5 Hz, 1H), 4.91 (dd, J¼1.6, 10.8 Hz, 1H), 4.90 (dd, J¼1.4,
10.7 Hz, 1H*), 2.59 (app t, J¼8.1 Hz, 1H), 2.49 (app t, J¼8.1 Hz, 1H*),
2.06e1.42 (m, 6H, 6H*),1.22 (s, 3H*),1.06 (s, 3H). 13C NMR (100 MHz,
4.5.1. N-((Perfluorobutyl)sulfonyl)cyclopentanecarboxamide
(6a). White solid. 1H NMR (500 MHz, CD3OD),
d
2.69 (app quint,
CD3OD),
d 183.9 (C), 183.8 (C*), 149.1 (CH), 145.0 (CH*), 111.7 (CH2),
J ¼ 8.0 Hz, 1H), 1.86e1.74 (m, 4H), 1.72e1.64 and 1.59e1.53 (m, 4H).
110.6 (CH2*), 60.8 (CH), 58.7 (CH*), 40.5 (CH2), 40.0 (CH2*), 29.8 (C),