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(c) Synthesis of 2-Cyclopentyl-2-methylpropane-1,3-diyl Bis-
(trifluoromethanesulfonate). A general procedure for triflation of
alcohols, reported in the literature,38 was followed. To a 3-neck
flame-dried flask containing a magnetic stirring bar and equipped with
a dropping funnel were added 6.64 mL of triflic anhydride (Tf2O:
39.5 mmol, 2.5 equiv) followed by 25 mL of DCM under Ar at T = 0
°C. A solution of 3.17 mL of pyridine (39.5 mmol, 2.5 equiv) and 2-
cyclopentyl-2-methylpropane-1,3-diol (2.5 g, 15.8 mmol) dissolved in
25 mL of DCM was then added dropwise to the Tf2O solution. The
mixture was successively warmed to rt and followed by GC analysis.
After complete conversion of the substrate (2 h), the reaction was
quenched with water and extracted three times with 30 mL of DCM.
The organic layers were collected, dried with anhydrous Na2SO4,
filtered, and dried in vacuo to give 6.60 g (15.6 mmol, 99% yield) of a
brown solid containing the crude product. 2-Cyclopentyl-2-methyl-
propane-1,3-diylbis(trifluoromethanesulfonate) has been identified by
1H NMR analysis and used in the following step without further
2-Methylcyclopentanone. GC−MS m/z (relative abundance): 98
(M+), 83, 69, 56, 55, 42 (100), 39. Data are consistent with those
obtained from the analysis of a commercially available sample.
3-Methylcyclopentanone. GC−MS m/z (relative abundance): 98
(M+), 83, 70, 69, 56, 55, 42 (100), 41, 39. Data are consistent with
those reported in the literature.42
trans-1-Methylcyclopentane-1,2-diol. GC−MS m/z (relative
abundance): 116 (M+), 98, 83, 73, 69, 57 (100). Data are consistent
with those reported in the literature.43
2-Hydroxy-2-methylcyclopentanone. GC−MS m/z (relative
abundance): 114 (M+), 98, 83, 73, 69, 57 (100), 41. Data are
consistent with those reported in the literature.44
1-tert-Butylcyclopentanol. GC−MS m/z (relative abundance):
109, 85 (100), 67, 57. Data are consistent with those obtained from
the analysis of an authentic sample that was present in our laboratory
from previous studies.40
2-tert-Butylcyclopentanone. GC−MS m/z (relative abundance):
140 (M+), 125, 97, 84, 78 (100), 57, 55, 41. Data are consistent with
those reported in the literature.45
1
purification. H NMR (CDCl3, 400 MHz) δ: 4.38 (s, 4H), 1.98 (m,
1H), 1.64 (m, 6H), 1.32 (m, 2H), 0.99 (s, 3H).
3-tert-Butylcyclopentanone. GC−MS m/z (relative abundance):
140 (M+), 125, 97, 84, 69, 57 (100), 55, 41. Data are consistent with
those reported in the literature.46
1-Phenylcyclopentanol. GC−MS m/z (relative abundance): 162
(M+), 144, 133 (100), 128, 115, 105, 98, 78, 77, 55. Data are
consistent with those obtained from the analysis of an authentic
sample that was present in our laboratory from previous studies.40
2-Phenylcyclopentanone. GC−MS m/z (relative abundance): 160
(M+), 145, 117, 105, 104 (100). Data are consistent with those
reported in the literature.47
3-Phenylcyclopentanone. GC−MS m/z (relative abundance): 160
(M+), 142, 131, 128, 120, 117, 115, 105 (100), 100. Data are
consistent with those obtained from the analysis of a commercially
available sample.
trans-1-Phenylcyclopentane-1,2-diol. GC−MS m/z (relative
abundance): 178 (M+), 133, 105, 77. Data are consistent with
those reported in the literature.48
2-Hydroxy-2-phenylcyclopentanone. GC−MS m/z (relative
abundance): 176 (M+), 148, 133, 129, 120, 115, 105. Data are
consistent with those reported in the literature.49
1-Methylcyclohexanol. GC−MS m/z (relative abundance): 114
(M+), 99, 85, 81, 72, 71 (100), 59, 58, 57, 55, 43. Data are consistent
with those obtained from the analysis of a commercially available
sample.
(d) Synthesis of tert-Butylcyclopentane. To a 3-neck flame-dried flask
equipped with a dropping funnel and containing 5.0 g of 2-
cyclopentyl-2-methylpropane-1,3-diylbis(trifluoromethanesulfonate)
(12 mmol) in 50 mL of THF under stirring was added 40 mL of a 1.0
M solution of LiBHEt3 in THF (40 mmol) dropwise under Ar at T =
0 °C. The mixture was then warmed to rt and followed by GC
analysis. After 1 h, quantitative conversion of the substrate was
observed and the reaction was quenched with 1.0 M HCl and
extracted three times with 35 mL of pentane. The organic layers were
collected, dried with anhydrous Na2SO4, and filtered. Because of the
relatively low boiling point of the product, special care was taken
during the purification procedures. Pentane and THF were distilled
away from the mixture at ordinary pressure, and the crude material
was then purified by silica gel column chromatography using pentane
as eluent. Pentane was distilled away once again at ordinary pressure
and the product dried in vacuo at 0 °C, yielding 770 mg (6.1 mmol,
41% yield) of pure tert-butylcyclopentane. Spectroscopic and
spectrometric data are consistent with those previously reported in
the literature.37 1H NMR (CDCl3, 700 MHz) δ: 1.61 (m, 1H), 1.56
(m, 4H), 1.49 (m, 2H), 1.22 (m, 2H), 0.84 (s, 9H). 13C NMR{1H}
(CDCl3, 100 MHz) δ: 51.1, 32.1, 27.8, 27.4, 26.0. GC−MS m/z: 126
(M+), 111, 69, 68, 57, 56 (100).
Phenylcyclopentane was obtained by Friedel−Crafts alkylation of
benzene following a procedure reported in the literature.39 1H NMR
(CDCl3, 400 MHz) δ: 7.28−7.14 (m, 5H), 3.04−2.93 (m, 1H),
2.07−2.01 (m, 2H), 1.80−1.50 (m, 6H).
2-Methylcyclohexanone. GC−MS m/z (relative abundance): 112
(M+), 97, 95, 85, 84, 81, 69 (100). Data are consistent with those
obtained from the analysis of a commercially available sample.
3-Methylcyclohexanone. GC−MS m/z (relative abundance): 112
(M+), 97, 95, 84, 83, 79, 69 (100). Data are consistent with those
obtained from the analysis of a commercially available sample.
4-Methylcyclohexanone. GC−MS m/z (relative abundance): 112
(M+), 97, 95, 84, 83, 79, 69, 58, 55 (100). Data are consistent with
those obtained from the analysis of a commercially available sample.
Cyclohexyl methyl ketone. GC−MS m/z (relative abundance):
126 (M+), 111, 84, 71, 68, 67, 55 (100). Data are consistent with
those obtained from the analysis of a commercially available sample.
1-Ethylcyclohexanol. GC−MS m/z (relative abundance): 128
(M+), 99 (100), 85, 81, 72, 69, 55. Data are consistent with those
obtained from the analysis of an authentic sample that was present in
our laboratory from previous studies.40
Reaction Products. The following reaction products are
commercial samples of the highest quality available and were used
as received: 1-methylcyclopentanol, trans-2-methylcyclopentanol, 2-
methylcyclopentanone, 3-phenylcyclopentanone, 1-methylcyclohexa-
nol, 2-methylcyclohexanone, trans-2-methylcyclohexanol, 3-methyl-
cyclohexanone, cis-4-methylcyclohexanol, trans-4-methylcyclohexanol,
4-methylcyclohexanone, cyclohexyl methyl ketone, 4-ethylcyclohex-
anol (cis−trans mixture), 4-ethylcyclohexanone, 4-isopropylcyclohex-
anol (cis−trans mixture), 4-isopropylcyclohexanone, 4-tert-butylcyclo-
hexanone, cis-4-tert-butylcyclohexanol, trans-4-tert-butylcyclohexanol,
trans-2-phenylcyclohexanol, 4-phenylcyclohexanone.
Authentic samples of 1-tert-butylcyclopentanol, 1-phenylcyclopen-
tanol, 1-ethylcyclohexanol, 1-isopropylcyclohexanol, 1-tert-butylcyclo-
hexanol, and 1-phenylcyclohexanol were available in our laboratory
from previous studies.40
2-Cyclohexyl-2-propanol was prepared by reaction of cyclohexyl
methyl ketone with ethylmagnesium chloride in anhydrous tetrahy-
drofuran according to a procedure reported in the literature.41
In order to compare reaction products with authentic samples by
GC analysis, cis−trans mixtures of secondary alcohols were obtained
by reduction with NaBH4 of available ketones
2-Ethylcyclohexanone. GC−MS m/z: 126 (M+), 111, 97, 83, 69,
67, 55 (100). Data are consistent with those reported in the
literature.50
3-Ethylcyclohexanone. GC−MS m/z: 126 (M+), 111, 98, 97, 83
(100), 70, 55. Data are consistent with those reported in the
literature.51
4-Ethylcyclohexanone. GC−MS m/z: 126 (M+), 111, 108, 98, 83,
70, 67, 56, 55 (100). Data are consistent with those obtained from the
analysis of a commercially available sample.
Characterization of the Oxidation Products. 1-Methylcyclo-
pentanol. GC−MS m/z (relative abundance): 100 (M+), 85, 83, 71
(100), 58, 57, 55. Data are consistent with those obtained from the
analysis of a commercially available sample.
2-Cyclohexyl-2-propanol. GC−MS m/z (relative abundance): 142
(M+), 130, 124, 120, 115, 109 (100), 100. Data are consistent with
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J. Org. Chem. 2021, 86, 9925−9937