5
24
A. Itoh et al.
LETTER
.
1
)
I2
R
2I
FSM-16 (200 mg)
I2 (0.3 equiv.), hν (400 W)
2 (74 %)
+
60 % of 19
was recovered
1
(50 mg)
.I
2)
.
+
I
19
O2
(50 mg)
iPr O (10 ml), 48 h
2
20
R
Scheme 2
O
O
.I
O
H
OH
I
The promoter FSM-16 was found to be a recyclable pho-
tocatalyst. Thus, the recovered FSM-16, which was dried
at room temperature for 2 h under reduced pressure,
showed no loss of activity for the reaction after being used
three times (Table 3).
2
O
1
22
R
R
R
I
CO H
2
2
3
R
Table 3 Recycle of FSM-16
Scheme 3
FSM-16
I2 (0.3 equiv.), hν
1
50 mg)
2
(
(
3) (a) Inagaki, S.; Koiwai, A.; Suzuki, N.; Fukushima, Y.;
(
iPr O (5 ml), r.t., 36 h
2
Kuroda, K. Bull. Chem. Soc. Jpn. 1996, 69, 1449.
(
b) Inagaki, S.; Fukushima, Y.; Kuroda, K. J. Chem. Soc.,
Cycle of FSM-16 1st
Yield (%) of 2 80
2nd
84
3rd
81
Chem. Commun. 1993, 680.
4) (a) Itoh, A.; Kodama, T.; Inagaki, S.; Masaki, Y. Org. Lett.
2000, 2, 331. (b) Itoh, A.; Kodama, T.; Inagaki, S.; Masaki,
Y. Chem. Lett. 2000, 542. (c) Itoh, A.; Kodama, T.; Inagaki,
S.; Masaki, Y. Org. Lett. 2000, 2, 2455. (d) Itoh, A.;
Kodama, T.; Masaki, Y. Chem. Lett. 2001, 686. (e)Itoh,A.;
Kodama, T.; Inagaki, S.; Masaki, Y. Org. Lett. 2001, 3,
Although the mechanism of the interaction between the
substrate and the active site on the pore walls of FSM-16
and the reasons for the promoting effect of a catalytic
amount of iodine are not yet clear, Scheme 3 shows a pos-
sible path by considering both the lack of promoting effect
without oxygen in this reaction and our previous study for
2653.
(
5) A typical procedure follows: In a pyrex tube, a suspension of
4-tert-butylstyrene (1, 50 mg), iodine and silica (100 mg) in
dry i-Pr O (5 mL) was stirred, and irradiated externally at
2
4
room temperature with a 400-W high-pressure mercury
lamp under aerobic atmosphere for 36 h. FSM-16 was then
filtered off and washed with ethyl acetate, and the filtrate
was washed with aq. sodium thiosulfate solution and brine.
The organic layer was dried over magnesium sulfate and
concentrated under reduced pressure. Pure 4-tert-
butylbenzoic acid (2) (46 mg, 82%) was obtained after
purification by preparative TLC.
oxidation with FSM-16. Benzyl radical species 20 is gen-
erated by addition of an iodine radical, which is formed
under photoirradiation, to the double bond. Radical spe-
cies 20 traps molecular oxygen in air to afford 21, and,
furthermore, hydroperoxide 22 is thought to be formed by
abstraction of the hydrogen atom from a hydrogen source
such as i-Pr O or FSM-16. We believe -iodo carbonyl
2
(
6) The reaction will be completed in a much shorter reaction
time than that indicated in the table with a new 400-W high-
pressure mercury lamp, since the lamp, we used, is thought
to be deteriorated: it had been used for a long time (14000
hrs) before this study. Product 2, for example, was afforded
in 80% yield for 18 h reaction with a new lamp when 1 was
used as starting material..
compound 23 is a key intermediate, since 4-tert-bu-
tylphenacyl iodide (23, R = t-Bu) was detected by NMR
as a by-product in the course of the reaction when using 1
as substrate, and 2 was obtained in 62% yield when using
4
-tert-butylphenacyl iodide as substrate under the same
reaction conditions. The intermediate 23 is then trans-
formed to the corresponding carboxylic acid under the
conditions, although the details of the transformation are
not clear.
(7) The unit cell dimension of FSM-16 was 45.3 nm. The pore
diameter was 2.8 nm, and the specific surface area was 948
2
m /g.
(
8) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.;
In conclusion, we have found a useful method for selec-
tive cleavage of double bonds conjugated with an aromat-
ic nucleus with a combination of FSM-16 and catalytic
iodine under photoirradiation.
Beck, J. S. Nature 1992, 359, 710.
(9) Tanev, P. T.; Pinnavaia, T. J. Science 1995, 267, 865.
10) (a) Zhang, W.; Froba, M.; Wang, J.; Tanev, P. T.; Wong, J.;
Pinnavaia, T. J. J. Am. Chem. Soc. 1996, 118, 9164.
(
(
b) Tanev, P. T.; Chibwe, M.; Pinnavaia, T. J. Nature 1994,
68, 321.
11) The pore walls of FSM-16 with higher stability than MCM-
1 will suppress the conversion of strained siloxane bridges,
3
(
References
4
(
1) Comprehensive Organic Transformations: A Guide to
Functional Group Preparations; Larock, R. C., Ed.; Wiley-
VCH: New York, 1989, .
which are proposed to be the active sites for photo reaction,
into inactive unstrained bridges, see: Inaki, Y.; Yoshida, H.;
Kimura, K.; Inagaki, S.; Fukushima, Y.; Hattori, T. Phys.
Chem. Chem. Phys. 2000, 2, 5293.
(
2) Hudlicky, M. Oxidations in Organic Chemistry, ACS
Monograph 186; American Chemical Society: Washington,
DC, 1990, 77–84.
Synlett 2002, No. 3, 522–524 ISSN 0936-5214 © Thieme Stuttgart · New York