Oxidative photodecarboxylation of α-hydroxycarboxylic acids and phenylacetic acid derivatives with FSM-16

Article abstract of DOI:10.1021/ol991284z

(Formula Presented) FSM-16, a mesoporous silica, was found to catalyze oxidative photodecarboxylation of α-hydroxy carboxylic acid and phenyl acetic acid derivatives to afford the corresponding carbonyl compounds. Furthermore, FSM-16 proved to be reuseable by recalcination at 450 °C after the reaction.

Full text of DOI:10.1021/ol991284z

ORGANIC
LETTERS
2000
Vol. 2, No. 3
331-333
Oxidative Photodecarboxylation of
r-Hydroxycarboxylic Acids and
Phenylacetic Acid Derivatives with
FSM-16
,†
Akichika Itoh,† Tomohiro Kodama,† Shinji Inagaki,‡ and Yukio Masaki*
Gifu Pharmaceutical UniVersity, 5-6-1 Mitahora-higashi, Gifu 502-8585, Japan, and
Toyota Central R & D labs., Inc., Aichi, 480-1192, Japan
masaki@gifu-pu.ac.jp
Received November 29, 1999
ABSTRACT
FSM-16, a mesoporous silica, was found to catalyze oxidative photodecarboxylation of r-hydroxy carboxylic acid and phenyl acetic acid
derivatives to afford the corresponding carbonyl compounds. Furthermore, FSM-16 proved to be reuseable by recalcination at 450 °C after the
reaction.
Recently, the importance of environmentally friendly pro-
cesses has been recognized over all fields of industry and,
needless to say, in the field of synthetic organic chemistry
as well. Photoreaction is a promising process in this context.1
Especially, the development of photocatalysts is a subject
that is now receiving much attention. TiO2, which catalyzes
oxidation of NOx and reduction of CO2,2 is one example of
a practical and useful photocatalyst. The photoreactivity of
microporous silicas,3 which contain transition metals, also
has been studied by many groups;4 however, little is known
about the silica itself.5 A similar trend appears for mesopo-
rous silicas,3 where there is only one report on the photo-
reactivity of the silica itself,6 and there are no reports
regarding the application of mesoporous silicas to synthetic
organic chemistry, so far. In the course of our investigation
on the application of mesoporous silicas to synthetic
chemistry, we have found that benzylic acid (1) was
oxidatively decarboxylated under irradiation to give ben-
zophenone (2) in the presence of FSM-16, which is a
mesoporous silica developed by Inagaki,7 and possesses high
(5) Yoshida, H.; Tanaka, T.; Matsuo, S.; Funabiki, T.; Yoshida, S. J.
Chem. Soc., Chem. Commun. 1995, 761. Ogata, A.; Kazusaka, A.; Enyo,
M. J. Phys. Chem. 1986, 90, 5201. Anpo, M.; Yun, C.; Kubokawa, Y. J.
Catal. 1980, 61, 267. Morikawa, A.; Hattori, M.; Yagi, K.; Otsuka, K. Z.
Phys. Chem., N. F. 1977, 104, 309.
(6) Yoshida, H.; Kimura, K.; Inaki, Y.; Hattori, T. Chem. Commun. 1997,
129.
(7) Inagaki, S.; Koiwai, A.; Suzuki, N.; Fukushima, Y.; Kuroda, K. Bull.
Chem. Soc. Jpn. 1996, 69, 1449. Inagaki, S.; Fukushima, Y.; Kuroda, K. J.
Chem. Soc., Chem. Commun. 1993, 680.
† Gifu Pharmaceutical University
‡ Toyota Central R & D labs., Inc.
(1) CRC Handbook of Organic Photochemistry and Photobiology;
Horspool, W. M., Song, P.-S. Ed.; CRC Press: Boca Raton, 1995.
(2) Liu, B. J.; Torimoto, T.; Matsumoto, H.; Yoneyama, H. J. Photochem.
Photobiol. 1997, 108, 187. Inoue, T.; Fujishima, A.; Konishi, S.; Honda,
K. Nature 1979, 277, 637.
(3) IUPAC recommends a classification of pore to micropore (D < 2
nm; D, pore diameter) and mesopore (2 nm < D < 50 nm), see: IUPAC
Manual of Symbols and Terminology, appendix 2, Part 1, Colloid and
Surface Chemistry. Pure Appl. Chem. 1972, 31, 578.
(4) Anpo, M.; Yamashita, H. Surface Photochemistry; Anpo, M., Ed.;
John Wiley & Sons: London, 1996.
(8) Yamamoto, T.; Tanaka, T.; Funabiki, T.; Yoshida, S. J. Phys. Chem.
B 1998, 102, 5830. Yamamoto, T.; Tanaka, T.; Inagaki, S.; Funabiki, T.;
Yoshida, S. J. Phys. Chem. B 1999, 103, 6450.
(9) Kresge, C. T.; Lenowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J.
S. Nature 1992, 359, 710. Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Lenowicz,
M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T.-W.; Olson, D. H.; Sheppard,
E. W.; McCullen, S. B.; Higgis, J. B.; Schlenker, J. L. J. Am. Chem. Soc.
1992, 114, 10834.
(10) Zhang, W.; Fro¨ba, M.; Wang, J.; Tanev, P. T.; Pinnavaia, T. J. J.
Am. Chem. Soc. 1996, 118, 9164. Tanev, P. T.; Chibwe, M.; Pinnavaia, T.
J. Nature 1994, 368, 321.
10.1021/ol991284z CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/11/2000

surface area, narrow pore size distribution, high pore volume,
and acidic property8 such as that of MCM-419 and HMS,10
which are typical mesoporous silicas (Scheme 1).
Next, the effect of additives on this reaction was studied
(Table 2).16 Without additives, only a trace of the product 2
Table 2. Study for Oxidative Photodecarboxylation with
Several Additives
Scheme 1
recovery
yield of
entry
additives
t (h)
of 1 (%)
2 (%)
1
2
3
4
5
6
7
8
9
24
5
78
<1
25
44
66
56
30
54
67
9
88
55
35
20
20
66
23
10
Thermal11 and photolytic12 oxidative decarboxylation reac-
tions of phenyl acetic acid derivatives, which have been
reported by several groups to proceed by using heavy metals
as promoters, produce a large amount of waste and thus
causes environmental problems. If FSM-16, which is free
of heavy metals, is recyclable, the reaction using FSM-16 is
considered to be a reaction of low environmental impact. In
this letter, we report the catalytic ability of FSM-16 in the
oxidative photodecarboxylation reaction of R-hydroxy car-
boxylic acids and phenyl acetic acid derivatives.
FSM-16
MCM-41
HMS
5
5
H-Y
5
Na-Y
5
H-ZSM-5
SiO2
5
5
Al2O3
5
was obtained even after a longer reaction time (24 h), and
78% of the starting benzylic acid (1) was recovered (entry
1). MCM-41 and HMS, which are other mesoporous silicas,
and H-Y, Na-Y, and H-ZSM-5, which are typical mi-
croporous zeolites, showed photoreactivity to some extent,
however, they were not as effective as FSM-16 (entries 2-7).
Silica gel and alumina, which are amorphous porous materi-
als, afforded 2 in only low yields (entries 8 and 9).
Other R-hydroxycarboxylic acids (3, 5, and 8) also
afforded the corresponding products in the same manner as
1 (Table 3). Acetophenone (4) was obtained in 78% yield
as the sole product when atrolactic acid (3) was used as a
substrate (entry 1). 4-Methoxymandelic acid (5) and 2-hy-
droxypalmitic acid (8), which are secondary R-hydroxy
carboxylic acids, gave a mixture of the corresponding
aldehyde and carboxylic acid (entries 2 and 3). Surprisingly,
Table 1 shows the results of photoreaction of benzylic acid
(50 mg) in the presence of FSM-1613 (100 mg) in several
solvents using 100- and 400-W high-pressure mercury lamps
at room temperature.14 Among the solvents examined, hexane
was found to afford the best results (entries 1-7).15 Without
irradiation, benzophenone (2) was scarcely obtained even
in the presence of FSM-16; on the other hand, the reaction
proceeded smoothly under irradiation even with a 100-W
lamp (entries 11 and 12).
Table 1. Study of Reaction Condition for Oxidative
Photodecarboxylation Reaction with FSM-16
(11) Kim, Y. I.; Kim, Y. H. Tetrahedron Lett. 1998, 39, 639. Mohri, K.;
Mamiya, J.; Kasahara, Y.; Isobe, K.; Tsuda, Y. Chem. Pharm. Bull. 1996,
44, 2218. Komuro, M.; Nagatsu, Y.; Higuchi, T.; Hirobe, M. Tetrahedron
Lett. 1992, 33, 4949. Banerjee, A.; Hazra, B.; Bhattacharya, A.; Banerjee,
S.; Banerjee, G. C.; Sengupta, S. Synthesis 1989, 765. Fristad, W. E.; Klang,
J. A. Tetrahedron Lett. 1983, 24, 2219. Giordano, C.; Belli, A.; Citterio,
A.; Minisci, F. J. Chem. Soc., Perkin Trans. 1 1981, 1574. Santaniello, E.;
Ponti, F.; Manzocchi, A. Tetrahedron Lett. 1980, 21, 2655. Dessau, R. M.;
Heiba, E. I. J. Org. Chem. 1975, 25, 3647.
(12) Habibi, M. H.; Farhadi, S. Tetrahedron Lett. 1999, 40, 2821. Maki,
Y.; Sako, M.; Oyabu, I.; Murase, T.; Kitade, Y.; Hirota, K. J. Chem. Soc.,
Chem. Commun. 1989, 1780.
(13) FSM-16 used in this study was synthesized according to ref 7. The
unit cell dimensions of this FSM-16 was 4.63 nm. The pore diameter was
2.9 nm, and the specific surface area was 882 m2/g.
(14) A typical procedure follows: Irradiation of a suspension of benzilic
acid (1, 50 mg) and FSM-16 (100 mg) in dry hexane (5 mL) at room
temperature with a 400-W high-pressure mercury lamp for 5 h. FSM-16
was then filtered off and washed with ethyl acetate, and the filtrate was
concentrated under reduced pressure. Pure benzophenone (2) (35 mg, 88%)
was obtained after purification by preparative TLC.
(15) The solubility of O2 in hexane is higher than that of other typical
organic solvents, see: Che, Y.; Tokuda, K.; Ohsaka, T. Bull. Chem. Soc.
Jpn. 1998, 71, 651.
hν
(W)
FSM-16
(mg)
t
recovery
yield of
entry
solvent
(h)
of 1 (%)
2 (%)
1
2
400
400
400
400
400
400
400
400
400
400
100
100
100
100
100
100
100
100
100
100
50
5
5
5
5
5
5
5
4
3
5
5
5
47
35
32
18
56
21
<1
11
19
18
10
73
34
49
50
36a
12b
65
88
80
63
75
79
<1
acetone
MeCN
MeOH
H2O
3
4
5
6
toluene
hexane
hexane
hexane
hexane
hexane
hexane
7
8
9
10
11
12
100
100
a A total of 17% of 1,1-diphenylethylene glycol was obtained. b A total
of 11% of benzopinacol was obtained.
(16) The conversions using the additives except FSM-16 were not
optimized.
332
Org. Lett., Vol. 2, No. 3, 2000

Table 3. Oxidative Photodecarboxylation of Several Substrates
Table 4. Recycle of FSM-16
with FSM-16
cycle of FSM-16
1st
2nd
91
3rd
86
4th
86
5th
81
yield (%) of 2
87
The mechanism of this reaction is not clear yet, however,
the active sites produced by dehydration from silanol groups
on the wall of FSM-16 during calcination are thought to
participate in decarboxylation of the substrate.5 An atmo-
spheric oxygen is also concerned in this reaction as an
oxidizing reagent. Table 5 shows the results of a study of
Table 5. Effect of Oxygen
yield of 2 (%)
t (h)
under N2
under O2
under air
3
5
5
7
61
73
69
88
the effect of oxygen. Only a small amount of product 2 was
obtained under N2, while under O2 the yield of 2 was
comparable to that under air. Since no acceleration of this
reaction was observed under O2, a high concentration of
oxygen was not required; however, oxygen proved to be an
important factor for this reaction. Furthermore, an attempt
was made to detect the intermediates and to clarify the
reaction pathway by terminating the reaction with 12 at 12
h; however, the possible intermediates, 5 or 4-methoxybenzyl
alcohol (14), were not detected by 400 MHz NMR analysis.17
On the other hand 14 was allowed to react under the same
conditions as for 12 and found to afford 6 (9%) and 7 (3%),
which were similar to results for 12. This suggests the final
oxidized products were provided by oxidation of a benzyl
alcohol species as the possible intermediates. Studies on a
more detailed mechanism and applications to other substrates
are now in progress in our laboratory.
2-phenylpropionic acid (11) and 4-methoxyphenylacetic acid
(12), which possess no hydroxyl group at the R-position,
also afforded acetophenone (4, 47%), and a mixture of the
corresponding degraded aldehyde (6, 30%) and carboxylic
acid (7, 44%), respectively (entries 4 and 5). On the other
hand, palmitic acid (13), which is a simple carboxylic acid,
was unfortunately intact under the conditions, and only the
starting material was recovered quantitatively even after 48
h (entry 6).
The promoter FSM-16 was found to be recyclable and
useful as a photocatalyst. Thus, the recovered FSM-16, which
was recalcinated at 450 °C for 4 h after the photoreaction of
1, showed high activity in the reaction, providing 81% yield
of 2 even after being reused 5 times (Table 4).
(17) The detected products of this reaction were 6 (8%) and 7 (2%).
The yield was estimated on the ratio of integral value of 400 MHz NMR
analysis.
OL991284Z
Org. Lett., Vol. 2, No. 3, 2000
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