H. Schill, S. I. Kozhushkov, R. Walsh, A. de Meijere
FULL PAPER
(ddd, J = 6.8, 11.2, 141.8 Hz, 1 H, O13CH2), 4.68 (s, 1 H, OH)
ppm. 13C NMR: δ = 3.2 (d, J = 2.5 Hz, CH2), 5.2, 10.6 (CH2), 19.4
(d, J = 47.4 Hz, CH), 13.2 (C), 66.2 (13CH2) ppm.
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1Ј,1Ј-D2 (1.95 g, 79%) was obtained according to GP3. H NMR:
δ = 1.02–1.19 (m AAЈBBЈ, 4 H, 2 CH2), 1.38 (s, 2 H, CH2) ppm.
13C NMR: δ = 10.0 (CH2), 10.1 (2 CH2), 10.6, 137.2 (C), 97.9
(quint, J = 24.7 Hz, CD2) ppm.
Preparation of Spiropentylmethyl Bromides 17. General Procedure
(GP) 2: To a solution of triphenylphosphane (1.05 equiv.) in anhy-
drous dichloromethane (50 mL), bromine (1.05 equiv.) was added
at –30 to –15 °C over a period of 10 min. After an additional
15 min of stirring, a mixture of alcohol (35 mmol) and anhydrous
pyridine (1 equiv.) was added dropwise at –15 °C over a period of
15 min. The mixture was stirred at 20 °C for an additional 12 h,
and then all the volatile material was “bulb-to-bulb”-distilled into
a trap cooled to –78 °C, at first under water-aspirator vacuum and
30 °C oil-bath temperature, and then under further reduced pres-
sure (0.1 Torr) with an oil bath (100 °C). The receiver flask was
warmed up to 20 °C, and the solvent was removed by distillation
at atmospheric pressure using a 30-cm Vigreux column. The residue
was distilled under reduced pressure.
2,2-Dideuterio-1-methylenespiropentane (4-2,2-D2): From the bro-
mide 17-2,2-D2 (4.89 g, 30 mmol) and tBuOK (4.38 g, 39 mmol),
4-2,2-D2 (1.36 g, 55%) was obtained according to GP3. H NMR:
δ = 1.02–1.19 (m AAЈBBЈ, 4 H, 2 CH2), 5.15 (s, 1 H, =CH2), 5.29
(s, 1 H, =CH2) ppm. 13C NMR: δ = 10.1 (2 CH2), 98.5 (CH2), 10.5,
137.3 (C), 10.0 (quint, J = 26.2 Hz, CD2) ppm.
1
([13C]Methylene)spiropentane (4-1Ј-13C): According to GP3, a mix-
ture (2.17 g) of the labeled methylenespiropentane 4-1Ј-13C and
tert-butyl spiropentyl[13C]methyl ether (72:28) was obtained from
the bromide 17-1Ј-13C (4.70 g, 29.0 mmol) and tBuOK (4.23 g,
37.7 mmol). 4-1Ј-13C: 1.20 g, 52% (based on the 1H-NMR spec-
trum). 1H NMR: δ = 1.02–1.19 (m AAЈBBЈ, 4 H, 2 CH2), 1.38 (dd,
J = 2.0, 3.8 Hz 2 H, CH2), 5.15 (ddt, J = 0.5, 2.0, 160.3 Hz, 1 H,
=13CH2), 5.29 (d, J = 161.5 Hz, 1 H, =13CH2) ppm. 13C NMR: δ
= 10.1 (CH2), 10.2 (2 CH2), 10.6 (C), 98.8 (13CH2), 137.5 (d, J =
98.5 Hz, C) ppm. tert-Butyl spiropentyl[13C]methyl ether: 939 mg,
(Bromodideuteriomethyl)spiropentane (17-1Ј,1Ј-D2): From the
alcohol 16-1Ј,1Ј-D2 (3.87 g, 38.7 mmol), Ph3P (10.65 g, 40.6 mmol),
Br2 (6.49 g, 2.09 mL, 40.6 mmol) and pyridine (3.11 g, 3.28 mL),
the bromide 17-1Ј,1Ј-D2 (5.10 g, 81%) was obtained according to
GP2, b.p. 78–80 °C (99 mbar). 1H NMR: δ = 0.64–0.74 (m, 2 H,
CH2), 0.76–0.84 (m, 2 H, CH2), 0.77 (dd, J = 4.5, 7.0 Hz, 1 H,
CH2), 1.14 (dd, J = 4.5, 7.5 Hz, 1 H, CH2), 1.61 (dd, J = 7.0,
7.5 Hz, 1 H, CH) ppm. 13C NMR: δ = 2.6, 6.0, 14.7 (CH2), 19.7
(CH), 17.5 (C), 38.0 (quint, J = 23.4 Hz, CD2) ppm.
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1
21% (based on the H-NMR spectrum). H NMR: δ = 0.57–0.78
(m, 4 H, 2 CH2), 1.00–1.11 (m, 3 H, CH2 + CH), 1.27 (s, 9 H, 3
CH3), 3.22 (ddd, J = 7.3, 9.3, 140.0 Hz, 1 H, O13CH2), 3.32 (ddd,
J = 6.5, 9.3, 141.5 Hz, 1 H, O13CH2) ppm. 13C NMR: δ = 3.5
(CH2), 5.4 (CH2), 11.2 (CH2), 13.4 (C), 17.4 (d, J = 50.3 Hz, CH),
27.6 (3 CH3), 65.5 (13CH2), 72.3 (C) ppm.
1-(Bromomethyl)-2,2-dideuteriospiropentane (17-2,2-D2): From the
alcohol 16-2,2-D2 (4.58 g, 45.7 mmol), Ph3P (12.59 g, 48 mmol),
Br2 (7.67 g, 2.47 mL, 48 mmol) and pyridine (3.62 g, 3.70 mL), the
bromide 17-2,2-D2 (5.51 g, 74%) was obtained according to GP2,
Scrambling of 13C and D2 Labels in 1Ј-Labeled Methylenespiropen-
tanes 4: A sample of each of the 1Ј-labeled methylenespiropentane
4 (50–80 mg) was placed in a thick-walled ampoule (volume ca.
1 mL). The ampoule was purged with Ar and sealed before being
heated in an oven at 210 °C for 60 min. The contents of the am-
poules were analyzed on the basis of their 1H- and 13C-NMR spec-
tra.
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b.p. 75–77 °C (99 mbar). H NMR: δ = 0.66–0.71 (m, 1 H, CH2),
0.75–0.84 (m, 2 H, CH2), 0.92–0.98 (m, 1 H, CH2), 1.71 (t, J =
7.0 Hz, 1 H, CH), 3.33 (dd, J = 7.0, 9.8 Hz, 1 H, BrCH2), 3.51 (dd,
J = 7.0, 9.8 Hz, 1 H, BrCH2) ppm. 13C NMR: δ = 2.6, 6.0, 39.7
(CH2), 19.8 (CH), 17.4 (C), 14.2 (quint, J = 23.1 Hz, CD2) ppm.
Kinetic Measurements of the Rearrangement of Methylenespiropen-
tene (4) in the Gas Phase: The apparatus used was a static conven-
tional grease-free vacuum system made from Pyrex, with Youngs
stopcocks. The spherical reaction vessel (volume ca. 250 mL) was
placed in a stirred salt (NaNO2/KNO3 eutectic) bath thermostat
controlled by an AEI (GEC) RT3R/2 controller. Temperatures were
measured with a calibrated Pt/Pt-13%Rh thermocouple. Pressures
Ն1 Torr were measured with a conventional mercury manometer,
pressures Ͻ1 Torr with Pirani G5C-2 and Speedivac B4 (Edwards)
instruments. Product-mixture analyses were performed by gas
([13C]Bromomethyl)spiropentane (17-1Ј-13C): From the alcohol 16-
1Ј-13C (3.53 g, 35.6 mmol), Ph3P (10.05 g, 38.3 mmol), Br2 (6.13 g,
1.97 mL, 38.3 mmol) and pyridine (2.77 g, 2.83 mL), the bromide
17-1Ј-13C (4.86 g, 84%) was obtained according to GP2, b.p. 77–
78 °C (95 mbar). 1H NMR: δ = 0.66–0.74 (m, 2 H, CH2), 0.78–
0.86 (m, 2 H, CH2), 0.93–0.97 (m, 1 H, CH2), 1.16 (quint, J =
3.6 Hz, 1 H, CH2), 1.60–1.65 (m, 1 H, CH), 3.33 (ddd, J = 8.3, 9.8,
153.0 Hz, 1 H, BrCH2), 3.52 (ddd, J = 6.8, 9.8, 153.0 Hz, 1 H,
BrCH2) ppm. 13C NMR: δ = 2.7 (d, J = 2.9 Hz, CH2), 6.0, 14.8
(CH2), 17.6 (d, J = 2.6 Hz, C), 20.0 (d, J = 46.9 Hz, CH), 38.7
(13CH2) ppm.
chromatography with
a Perkin–Elmer 8310 chromatograph
(4 mϫ2.3 mm, 15% MS550 on Chromosorb 60/80W, 35 °C) with
FID detection and electronic peak integration (Hewlett–Packard
HP 3380 A). The reactant master mixture consisted of about 1.0–
1.5% of 4 [prepared from bicyclopropylidene (3)[5a] according to
the published procedure[9]] and 1.5–2.0% of n-pentane as an in-
ternal standard diluted to about 400 Torr with N2 in a 500-mL
reservoir. Runs were carried out by admitting a known pressure
of the mixture (16–30 Torr) into the pre-evacuated (Յ0.005 Torr)
reaction vessel for a certain time. The reaction was quenched by
sampling some of the reaction vessel contents with a pre-evacuated
sample container, from which samples (diluted with about 30 Torr
of N2) could be injected into the gas chromatograph. After 2–3
runs, a blank analysis of the unused master mixture was performed
to check the mass balance of the reaction. To rule out the influence
of radical chain-reaction pathways, a run with about 5% propene
Preparation of Labeled Methylenespiropentanes 4. General Pro-
cedure (GP) 3: To a stirred solution of potassium tert-butoxide
(1.3 equiv.) in anhydrous dimethyl sulfoxide (50 mL), 30 mmol of
the respective neat spiropentylmethyl bromide 17 was added over
a period of 0.5 h, while the temperature was maintained between
20 and 25 °C. After additional stirring in a closed flask at ambient
temperature for 12 h, all the volatile material was “bulb-to-bulb”-
distilled into the cold trap under reduced pressure (0.1 Torr) at a
maximum temperature of 40 °C inside the flask. The content of the
cold trap was warmed up to 20 °C, washed with four 5-mL portions
of ice-cold water and transferred into a preweighed vessel contain-
ing a couple of granules of molecular sieves (4 Å). The products
were of 93–95% purity.
(Dideuteriomethylene)spiropentane (4-1Ј,1Ј-D2): From the bromide as a radical scavenger was performed. For the test of surface influ-
17-1Ј,1Ј-D2 (4.89 g, 30 mmol) and tBuOK (4.38 g, 39 mmol), 4- ences, the reactor was replaced with another one filled with flame-
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Eur. J. Org. Chem. 2007, 1510–1516