H. Matsubara et al. / Journal of Fluorine Chemistry 129 (2008) 951–954
953
Table 2 (Continued )
Entry
Substrate
Procedure
C
Product
Isolated yield (%)b
8
97
92
92
92
9
C
D
C
10
11
a
General conditions: substrate (1 mmol), CH2l2 (2 mmol), hexane solution of Et2Zn or Et3AI (1 M, 2 mL_), FC-72 (1.5 mL) with aluminum foil protection from light, kept at
room temperature with gentle stirring. Procedure A: 36 h; Procedure B: 4 h with vigorous stirring; Procedure C: 58 h; Procedure D: 16 h with vigorous stirring.
b
Isolated yield by silica gel chromatography.
c
Cis/trans = 2.43/1.
Determined by 1H-NMR.
d
e
Galden HT-135 (1.5 mL) was used as a fluorous phase.
improved the yield (entry 6, Table 1). In order to reduce the
reaction time for the reaction of Et3Al/CH2I2, after the bottom layer
had disappeared, the test tube was stirred vigorously for a further
4 h (Procedure B). This modification also gave a good result (entry
3, Table 1).
the vigorous stirring of the resulting two layers after the bottom
layer disappeared significantly reduced the reaction time.
4. Experimental
Encouraged by the excellent adaptability of the Maruoka–
Yamamoto cyclopropanation reaction to the PV method, we
embarked on experiments with several other alkenes. In each
case 2 equiv. of CH2I2 and Et3Al was used (Table 2). In all cases
examined, the cyclopropanation reaction took place to give high
yields of the desired cyclopropanes. Styrene derivatives required
longer reaction times to complete than aliphatic alkenes (Proce-
dure C: with extended reaction time (58 h) after the bottom phase
disappeared) (entries 5–9, 11, Table 2). Coupled with the use of
vigorous stirring after the bottom layer disappeared, the total
reaction time was able to be shortened by a factor of 2–3 (entries 2
and 10, Table 2). Galden1 HT-135 is a polyether-type perfluori-
nated solvent, commercially available as a heat transfer liquid
(Solvay Solexis Inc.), bp 135 8C, density = 1.72 g/mL at 25 8C,
average molecular weight = 610. This inexpensive polyperfluoro
ether solvent was shown to function equally as well with FC-72
(entry 4).
FC-72 and Galden1 HT-135 were purchased from Sumitomo 3 M
Ltd., and Solvay Solexis Inc., respectively, and dried over molecular
˚
sieves 4 A before use. Reagents and solvents were used as received.
Hexane solution of diethylzinc (1 M) and triethylaluminum (1 M)
were purchased from Kanto Chemical Co,. Inc., and used as received.
Products were purified by column chromatography on silica gel
(Kanto Chemical Co., Inc., Silica Gel 60N, 70–230 mesh). 1H NMR
spectra were recorded with a JEOL JMN-500 (500 MHz) or a JEOL
JMN-400 (400 MHz) spectrometer while 13C NMR spectra were
recorded with a JEOL JMN-500 (125 MHz) or a JEOL JMN-400
(100 MHz) spectrometer. Infrared spectra were obtained on a JASCO
FT/IR-4100 spectrometer. Conventional and high-resolution mass
spectra were recorded with a Shimazu GCMS-QP 5050A instrument
and a JEOL MS-700 spectrometer, respectively.
4.1. General procedure for cyclopropanation of olefins by the phase-
vanishing method (Table 1, entry 2) (Procedure A)
FC-72 (1.5 mL) was placed in a pyrex test tube (13 mm
f
 105 mm) to which diiodomethane (2.0 mmol, 536 mg) was
added slowly using a glass pipette under argon atmosphere. 1-
Dodecene (1.0 mmol, 168 mg) was then added slowly, forming
three layers. A hexane solution (2 mL) of triethylaluminum (1 M)
was added to the top layer, and the test tube was covered with
aluminum foil in order to shield the reaction from light and kept it
at room temperature. The diiodomethane layer was gently stirred
using a magnetic stirrer, taking care not to mix the three layers. The
diiodomethane layer disappeared after 8 h, the hexane layer was
taken up with a pipette after 44 h. Additional hexane (3 mL Â 4)
was placed on the residual FC-72 layer, then decanted off. The
combined organic layer was washed with aqueous 0.5 M HCl
(20 mL) and saturated brine (20 mL), dried over Na2SO4, and
concentrated. Purification by short column chromatography on
silica gel with hexane gave decylcyclopropane (1, 178 mg, 98%) as a
3. Conclusion
Through the use of fluorous media, such as FC-72 (perfluor-
ohexanes) and Garden HT-135, as a phase screen, we have
demonstrated that cyclopropanation of alkenes can be easily
carried out conveniently without the necessity for slow addition of
diiodomethane and equipment for temperature control, which are
necessary for the conventional glass-flask reaction. Whereas the
Furukawa reagent (Et2Zn/CH2I2) did not function satisfactorily for
the present test tube-based triphasic system, the Maruoka–
Yamamoto reagent (Et3Al/CH2I2) gave the desired cyclopropana-
tion products in high yields. This carbenoid reagent coupled with
colorless oil; IR (neat):
1015, 820, 720 cmÀ1
n
3000, 2955, 2925, 2850, 1465, 1375, 1040,
;
1H NMR (500 MHz, CDCl3):
d
-0.12 (2H, m,
CH2 of cyclopropane), 0.38 (2H, m, CH2 of cyclopropane), 0.88 (3H,
t, J = 6.9 Hz, CH3), 1.17 (2H, q, J = 7.4, CH2-c-C3H6), 1.26–1.42 (16H,