7
658 J . Org. Chem., Vol. 65, No. 22, 2000
Notes
Sch em e 1
Exp er im en ta l P r oced u r e for th e Cou p lin g Rea ction of
-Iod oocta n e (1), Olefin (2), a n d CO. A small vial containing
1
AIBN (0.39 mmol) and a micromagnetic stirring bar were placed
in a 50-mL stainless steel autoclave. After the autoclave was
evacuated and then filled with argon, 1 (1.3 mmol), 2a (1.6
mmol), and (TMS)
autoclave (outside the vial) with a syringe. Then, CO was
pressurized to 50 atm, and then CO was added to the autoclave
3
SiH (2.0 mmol) were charged into the
2
with an HPLC pump to attain the total pressure of ap-
proximately 220 atm. The temperature was raised to 80 °C and
the pressure examined was achieved with the addition of more
CO
2
. After 5 h reaction, the vessel was cooled to approximately
and excess CO were vented, and the reactor was
-78 °C, CO
2
slowly warmed to room temperature. The remaining organic
liquid was diluted with 20 mL of ether. 1,8-Diazabicyclo[5.4.0]-
undecene (ca. 0.2 mL) was added to this solution to form a white
2
precipitate, and a small portion of ether solution of I was added
until the color changed. The precipitate was filtered off through
a plug of silica gel, and the precipitate was washed with ether
(
20 mL × 3). The combined ether solution was dried over
2
observed in scCO (Figure 1) can be interpreted in terms
anhydrous Na SO , and concentrated under reduced pressure.
2
4
of the cage effect. At high viscosities, 6 was predomi-
nantly obtained because of the cage effect as observed in
benzene. At low viscosities, the initially formed exocyclic
radical predominantly reacts with the silane to give 5
because of a weak cage effect. A similar remarkable
change in the selectivity with varying the pressure (or
The remained yellow oil was chromatographed on silica gel using
hexane/ethyl acetate (from 100/0 to 95/5 v/v) as a mobile phase.
A main fraction (R
contained 229.1 mg of 3a (90% yield).
-Cya n o-3-u n d eca n on e (3a ): 1H NMR (300 MHz, CDCl
f
) 0.34, hexane/ethyl acetate 5/1 (v/v))
1
3
2
)
-
δ 2.75 (t, COCH
COCH CH CN, 2H), 1.54 (br s, CH
br s, CH (CH CH CH
2
CH
2
CN, 2H), 2.53 (t, CH
2
CN, 2H), 2.39 (t, CH
CH CH
, 3H); C{ H}
2
2
3
(CH
2
)
5
2
2
CO, 2H), 1.22
density) of the CO
2
medium has also been presented in
13
1
(
3
2
)
5
2
2
CO, 10H), 0.82 (t, CH
3
1
7
the free-radical chlorination of alkanes, and the photo-
Fries rearrangement of naphthyl acetate.18 The product
ratio further increased at low substrate concentration
3
NMR (75.45 MHz, CDCl ) δ 206.4, 119.1, 42.4, 37.6, 31.7, 29.2,
29.1, 29.0, 23.6, 22.6, 14.0, 11.3; ESI HRMS calcd for C12
H
21
-
NOK (M + K) m/z 234.1260, found 234.1259.
1
Meth yl 4-oxod od eca n oa te (3b): H NMR (300 MHz, CDCl
3
)
(
0.0083 M) probably because of the dilution effect as
δ 3.62 (s, CH
COCH CH COO, 2H), 2.39 (t, CH
m, CH (CH CH CH CO, 2H), 1.22 (br s, CH
CO, 10H), 0.82 (t, CH , 3H); 13C{
H} NMR (75.45 MHz, CDCl ):
3
O, 3H), 2.67 (t, COCH
2
CH
2
COO, 2H), 2.53 (t,
CH COO, 2H), 1.53
(CH CH CH
1
6a,b
observed in solution.
2
2
2
COCH
2
2
The radical carbonylative ring-closing reaction of 6-io-
dohexyl acrylate (0.25 mmol) with 2 equiv of (TMS) SiH
in the presence of AIBN (0.2 equiv) in scCO including
(
3
2
)
5
2
2
3
2
)
5
2
2
-
1
3
3
3
δ 209.0, 173.2, 51.6, 42.7, 36.9, 31.7, 29.3, 29.1, 29.0, 27.6, 23.7,
2
2
2.5, 14.0. These spectroscopic data were consistent with those
CO (CO 50 atm, total pressure 295 atm) at 80 °C for 2 h
afforded the eleven-membered macrolide in 68% isolated
yield (eq 2). The yield of the macrolide is comparable to
that achieved in benzene.3b
1
9
previously reported.
1
2
,5-Tr id eca n ed ion e (3c): H NMR (300 MHz, CDCl
3
) δ 2.64
COCH
2
CO, 2H),
(m, COCH
2
CH
2
COCH
, 3H), 1.53 (m, CH
CH CH CO, 10H), 0.83 (t, CH
) δ 209.6, 207.2, 42.8, 36.8, 36.0,
3
, 4H), 2.40 (t, CH
2
COCH
2
CH
CH
, 3H); C-
2
3
,
2
H), 2.15 (s, COCH
.23 (br s, CH
3
3
(CH
2
)
5
CH
2
1
3
1
3
(CH
2
)
5
2
2
3
1
{
H} NMR (75.45 MHz, CDCl
1.8, 29.9, 29.3, 29.2, 29.1, 23.8, 22.6, 14.0. The H NMR data
3
1
3
2
0
were consistent with those previously reported.
Exp er im en ta l P r oced u r e for th e Ca r bon yla tive Cy-
cliza tion of 1-Iod o-4-h exen e (4). A small vial containing AIBN
(
0.15 mmol) and a micromagnetic stirring bar were placed in a
0 mL stainless steel autoclave. After the autoclave was evacu-
ated and then filled with argon, 4 (1.25 mmol) and (TMS) SiH
1.75 mmol) were charged to the autoclave (outside the vial) with
a syringe through an opening against a flow of argon. Then, CO
was pressurized to 50 atm, and finally CO was added to the
5
3
(
2
autoclave with an HPLC pump to attain the total pressure of
approximately 220 atm. The temperature was raised to 80 °C
and the final desired pressure (325 atm) was achieved with the
In conclusion, this free-radical carbonylation in scCO
is characterized by high efficiency and tunability of
product distribution with pressure because of the char-
2
addition of more CO
approximately -78 °C, CO
2
. After 5 h, the vessel was cooled to
and excess CO were vented, and the
2
acteristic properties of scCO
CO and controllable cage strength. Thus, scCO
2
such as high miscibility of
can
1
reactor was slowly warmed to room temperature. H NMR
spectrum of the reaction mixture containing 0.5 mmol of benzene
as an internal standard showed the yields of 5 and 6 to be 31%
and 68%, respectively.
2
replace environmentally unacceptable benzene. This is
the first example of free-radical carbonylation of organic
halides in scCO
2
.
Ca r bon yla tive Cycliza tion of 6-Iod oh exyl Acr yla te. A
small vial containing AIBN (0.05 mmol) and a micromagnetic
stirring bar were placed in a 50 mL stainless steel autoclave.
After the autoclave was evacuated and then filled with argon,
Exp er im en ta l Section
6
3
-iodohexyl acrylate (0.25 mmol) and (TMS) SiH (0.5 mmol) were
SAF ETY WARNING: Operators of high-pressure equipment
charged to the autoclave (outside the vial) with a syringe through
an opening against a flow of argon. Then, CO was pressurized
to 50 atm, and finally CO was added to the autoclave with an
2
should take proper precautions to minimize the risk of personal
7
b
injury.
HPLC pump to attain the total pressure of approximately 220
(17) (a) Tanko, J . M.; Suleman, N. K.; Fletcher, B. J . Am. Chem.
Soc. 1996, 118, 11958-11959. (b) Fletcher, B.; Suleman, N. K.; Tanko,
J . M. J . Am. Chem. Soc. 1998, 120, 11839-11844.
(19) Gavin, D. J .; Geraghty, Niall W. A. Synth. Commun. 1994, 24,
1351-1361.
(20) Stetter, H.; Kuhlmann, H. Chem. Ber. 1976, 109, 3426-3431.
(18) Andrew, D.; Des Islet, B. T.; Margaritis, A.; Weeden, A. C. J .
Am. Chem. Soc. 1995, 117, 6132-6133.