660
Churchill, Churchill, Huynh, Takeuchi, Distefano, and Jameson
filtered, and the hexanes removed by use of a rotary
evaporator. The resulting liquid was distilled and
a 43.3 g (42%) fraction obtained at 75–77ЊC (21
mm Hg) was judged by GC/MS to be the desired
product.
removed by rotary evaporator. The resulting liquid
was distilled and a 34.9 g (46%) fraction obtained
at 77–78ЊC (30 mm Hg) was judged by GC/MS to
be the desired product.
Synthesis of 1,1-di(pyrazol-1-yl)cyclopentane. A
300-mL roundbottomed flask was charged with 7.49
g (0.47 mol) of 1,1-diethoxycyclopentane, 7.01 g
(0.103 mol) pyrazole, 150 mL cyclohexane and 25
mg p-toluenesulfonic acid. The flask was fitted with
a Soxhlet apparatus in which the thimble is charged
with 20 g of 4-E molecular sieves (activated at
400ЊC for 5 h). The Soxhlet apparatus was topped
by a nitrogen T-tube and the reaction mixture is
heated to reflux for 15 h. The progress of the
reaction was monitored by TLC (alumina/toluene).
The organic layer was separated, dried over MgSO4,
and filtered. Evaporation of the organic layer to a
volume of 25 mL resulted in a deposit of white
crystals (6.2 g, 65% yield) which have a melting
Synthesis of 1,1-di(pyrazol-1-yl)cyclohexane. A
300-mL round-bottomed flask was charged with 150
mL toluene, 9.80 g (0.139 mol) pyrazole, 8.00 g (0.047
mol) 1,1-diethoxycyclohexane, and 25 mg p-tolu-
enesulfonic acid. The flask was fitted with a Soxhlet
apparatus in which the thimble is charged with 20 g
of 4-E molecular sieves (activated at 400ЊC for 5 h).
The Soxhlet apparatus was topped by a nitrogen T-
tube and the reaction mixture was heated to reflux for
5 days. The progress of the reaction was monitored
by TLC (alumina/toluene). The organic layer was
separated, dried over MgSO4, filtered, and evapo-
rated to an oil which was placed in a freezer over-
night. The crystals which resulted were triturated
with hexanes, filtered, and rinsed with hexanes and
methanol. In this manner, 5.35 g (53%) of white crys-
tals (m.p. 68–70ЊC) were obtained. 1H NMR (CDCl3)
ppm 1.5–2.9 (m, 10 H); 6.0–6.3 (m, 2H); 7.39
(d of d, 2H, J ϭ 3.2, 0.6 Hz); 7.50–7.60 (m, 2H).
13C NMR (CDCl3) ppm 22.4; 24.7; 35.7; 95.9; 106.1;
127.2; 139.6.
Preparation of a single crystal of 1,1-di(pyrazol-
1-yl)cyclohexane. A 50-mg sample was dissolved in
a minimum of warm cyclohexane. The solution was
cooled slowly in the dark and uncovered until com-
plete evaporation of the solvent occurred (approxi-
mately 2 days). A number of clear, colorless crystals
(approximately 2 mm ϫ 2 mm ϫ 3 mm) were col-
lected from the container. The 1H NMR spectrum of
the crystals was consistent with the 1H NMR spectrum
reported above and the melting point of the crystals
was 75.5–76ЊC. A crystal of size 0.45 ϫ 0.25 ϫ 0.15
mm was cut carefully from a larger crystal and used
for the X-ray diffraction study.
1
point of 126–131ЊC. H NMR (CDCl3) ppm 1.7–2.0
(m, 4 H); 2.8–3.1 (m, 4H); 6.22 (d of d, 2H, J ϭ
3.2, 0.6 Hz); 7.4–7.7 (m, 4H). 13C NMR (CDCl3)
ppm 22.4; 37.8; 86.6; 106.3; 127.7; 139.5.
Preparation of a single crystal of 1,1-di(pyrazol-
1-yl)cyclopentane. A 50-mg sample was dissolved in
a minimum of warm cyclohexane. The solution was
cooled slowly in the dark and uncovered until com-
plete evaporation of the solvent occurred (approxi-
mately 2 days). A number of clear, colorless crystals
(approximately 1 mm ϫ 1 mm ϫ 3 mm) were col-
lected from the container. The 1H NMR spectrum of
the crystals was consistent with the 1H NMR spectrum
reported above and the melting point of the crystals
was 130–131ЊC. A crystal of size 0.4 ϫ 0.4 ϫ 0.5
mm, cut from a larger crystal, was used in the X-ray
diffraction study.
Crystallographic studies
Synthesis of 1,1-diethoxycyclopentane. A 1-L
roundbottomed flask was charged with (in order)
70.0 g montmorillonite K, 400 mL hexanes, and
115 g triethyl orthoformate, (0.777 mol) and the
mixture was stirred for 15 min. Cyclopentanone
(43.7 g; 0.52 mol) was added and the mixture was
stirred for 1 h, at which time GC/MS analysis
indicated the reaction was complete. The montmo-
rillonite was removed by filtration, washed with
hexanes, and the combined filtrates were washed
with 200 mL of 0.5% Na2CO3. The organic layer
was dried over MgSO4, filtered, and the hexanes
Diffraction data were collected as described
previously;5 details are provided in Table 1. All
calculations were performed on a VAXstation 3100
computer with the use of the SHELXTL PLUS6,7
(Release 4.11 (VMS)) program package. Analytical
scattering factors were employed8a with the assump-
tion of neutral atoms; these were corrected for both
the real (⌬f Ј) and imaginary (i⌬f Љ) components of
anomalous dispersion.8b The following items should
be noted.
(1) A complete sphere of X-ray diffraction data
Churchill, Melvyn Rowen
