Catalytic oxidation of alcohols with Ru(Pybox)(Pydic) complex

Article abstract of DOI:10.1246/cl.2002.284

Primary and secondary alcohols were catalytically oxidized with diacetoxyiodobenzene in the presence of Ru(Pybox)(Pydic) complex to afford the corresponding aldehydes and ketones in high yields.

Full text of DOI:10.1246/cl.2002.284

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84
Chemistry Letters 2002
Catalytic Oxidation of Alcohols with Ru(Pybox)(Pydic) Complex
ꢀ
ꢀ
Seiji Iwasa, Kazushi Morita, Kentaro Tajima, Ahmad Fakhruddin, and Hisao Nishiyama
School of Materials Science, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580
(Received November 19, 2001; CL-011167)
Primary and secondary alcohols were catalytically oxidized
with diacetoxyiodobenzene in the presence of Ru(Pybox)(Pydic)
complex to afford the corresponding aldehydes and ketones in
high yields.
Attention has been paid for catalytic oxidation of alcohols as
one of fundamental organic reactions and industrial processes
under enduring efforts and consideration of efficiency and
environmental consciousness.1 Prominent successes in this
direction has been recently achieved by utilization of hydroper-
oxide or molecular oxygen with an assistance of potent ruthenium
2
;3
complexes. We disclose here an application of our epoxidation
system for efficient oxidation procedure of alcohols to aldehydes
or ketones since we have already reported a new epoxidation
system for olefins with Ru(Pybox)(Pydic) (1a), ruthenium[bi-
s(oxazolinylpyridine)-(pyridine-2,6-dicarboxylate)], and diace-
toxyiodobenzene [PhI(OAc)2].4
Scheme 1.
Table 1. Catalytic oxidation of alcohols with Ru(Pybox)(Pydic)
1a
a
a
Based on these previous studies, we initially applied our
hydrogenperoxide oxidation of hydroxamic acid to nitroso
intermediates with catalytic amount of 1a for the oxidation of
4
b
alcohols. This oxidation condition gave aldehydes and ketones
up to14–23% yields inthe case of benzyl alcohol derivatives. And
then we found that the addition of amines such as pyridine
increased the yields slightly up to 40%. However, further
optimization of the conditions shows no significant improvement
on the oxidation of alcohols.
On the other hand, the use of PhI(OAc)2 as an oxidant and
catalytic amount of 1a gave the corresponding products in high
yields as well as high chemoselectivities.
A typical procedure is as follows: To a solution of 1a
0.02 mmol, 2 mol% to alcohol) and benzhydrol (2a) (1.0 mmol)
(
in dichloromethane (5 mL) was added PhI(OAc)2 (1.4 mmol) as
5
an oxidant. The mixture was stirred for 10 h at room temperature.
After concentration, the residue was purified by column
chromatography with ethyl acetate-hexane to give benzophenone
(3a) in 96% yield (Scheme 1, Table 1, run 1). The oxidation of
several alkyl and benzylic secondary alcohols 2b–j is summar-
ized in Table 1. Among them, 4-phenyl-2-butanol 2c, mandelic
ester 2e and benzoin 2f required relatively longer reaction times
and an excess amount of the oxidant (run 3, 5–6).
A primary alcohol 2g, 1-dodecanol, was readily oxidized for
h under catalytic condition to give dodecanal (3g) in 97% yield
run 7). Oxidation of benzyl alcohols 2h and 2i was carried out at
6
(
room temperature to give the corresponding aldehydes in 74–76%
yields along with the corresponding carboxylic acids as side
products (run 8 and 9). In the case of cinnamyl alcohol,
epoxidation of olefin skeleton proceeded, but it was much slower
than the oxidation of hydroxyl groups (run 10).
In 1981, M u¨ ller and Gody reported catalytic oxidation of
alcohols with PhIO in the presence of RuCl2(PPh3)3 catalyst
in 45% with octanoic acid in 23%. They overcame the selectivity
of the aldehyde by using PhI(OAc) (1.3 equiv) in a short reaction
6
a
(
1 mol%). In their system, 1-octanol was oxidized to 1-octanal
2
Copyright Ó 2002 The Chemical Society of Japan

Chemistry Letters 2002
285
time.
The similar and chiral Ru(Pybox-i-pr)(Pydic) complex 1b
1 mol%) exhibited almost the same activity. The oxidation was
Press, Greenwich, CT (1994), Vol. 3, p 225. d) W. P. Griffith
and S. V. Ley, Aldrichchimica Acta, 23, 13 (1990). e) W. P.
Griffith, Chem. Soc. Rev., 21, 179 (1992). For recent papers: f)
K. Sato, M. Aoki, J. Takagi, and R. Noyori, J. Am. Chem. Soc.,
119, 12386 (1997). g) K. P. Peterson and R. C. Larlock, J.
Org. Chem., 63, 3185 (1998).
(
carried out in ethyl acetate because of high solubility of 1b.
Next, chemoselectivity between primary and secondary
ꢁ
alcohols with 2g and 2c was examined by using 1b at 0 C
(
Scheme 2). Dodecanol 2g was oxidized ca. four times faster than
-phenyl-2-butanol 2c. Similar selectivity for predominant
2
3
W.-H. Fung, W.-Y. Yu, and C.-M. Che, J. Org. Chem., 63,
2873 (1998) and references cited therein.
4
oxidation of primary alcohols were reported with certain
ruthenium complexes and co-oxidants, such as amine-N-oxide,
molecular oxygen, peracids etc.6b,d,i,j,q
E. Mark o´ , P. R. Giles, M. Tsukazaki, I. Chell e´ -Regnaut, C. J.
Urch, and S. M. Brown, J. Am. Che. Soc., 119, 12661 (1998).
References for Ru-catalyzed oxidations of alcohols are cited.
a) H. Nishiyama, T. Shimada, H. Itoh, H. Sugiyama, and Y.
Motoyama, J. Chem. Soc., Chem. Commun., 1997, 1863. b) S.
Iwasa, K. Tajima, S. Tsushima, and H. Nishiyama, Tetra-
hedron Lett., 42, 5897 (2001).
4
5
6
PhI(OAc)2 was purchased from ACROS. See ‘‘Encyclopedia
of Reagents for Organic Synthesis,’’ ed. by L. A. Paquette,
Wiley, New York (1995), Vol. 2, p 1479.
a) P. M u¨ ller and J. Gody, Tetrahedron Lett., 22, 2361 (1981).
They described that PhI¼O or PhI(OAc)2 themselves act as
oxidant of alcohols without metal catalysts, however they
need higher reaction temperature. Other Ru-catalyzed oxida-
tion of alcohols with a variety of oxidants, such as N-oxides,
epoxides, or molecular oxygen; for examples: b) K. B.
Sharpless, K. Akashi, and K. Oshima, Tetrahedron Lett.,
1
976, 2503. c) R. Tang, S. E. Diamond, N. Meary, and F.
Mares, J. Chem. Soc., Chem. Commun., 1978, 562. d) M.
Matsumoto and S. Itoh, J. Chem. Soc., Chem. Commun., 1981,
9
07. e) P. H. Carlsen, T. Katsuki, V. S. Martin, and K. B.
Sharpless, J. Org. Chem., 46, 3936 (1981). f) Y. Tsuji, T.
Ohta, T. Ido, H. Minbu, and Y. Watanabe, J. Organomet.
Chem., 270, 333 (1984). g) M. Tanaka, T. Kobayashi, and T.
Sakakura, Angew. Chem., Int. Ed. Engl., 23, 518 (1984). h) Y.
Yamamoto, H. Suzuki, and Y. Morooka, Tetrahedron Lett.,
26, 2107 (1985). i) C. Bilgrien, S. Davis, and R. S. Drago, J.
Am. Chem. Soc., 109, 3786 (1987). j) S. Kanemoto, S.
Matsubara, K. Takai, K. Oshima, K. Utimoto, and H. Nozaki,
Bull. Chem. Soc. Jpn., 61, 3607 (1988). k) A. C. Dengel,
A. M. Mel-Mendawy, W. P. Griffith, C. A. O’Mahoney, and
D. J. Williams, J. Chem. Soc., Dalton Trans., 1990, 737. l) J.-
E. B a¨ ckvall, R. L. Chowdhury and U. Karlsson, J. Chem.
Soc., Chem Commun., 1991, 473. m) A. Behr and K.
Eusterwiemann, J. Organomet. Chem., 403, 215 (1991). n)
G.-Z. Wang and J.-E. B a¨ ckvall, J. Chem. Soc., Chem.
Commun., 1992, 337. o) S.-I. Murahashi, T. Naota, Y. Oda
and N. Hirai, Synlett, 1993, 433. p) A. J. Bailey, W. P.
Grififth, and P. J. Savage, J. Chem. Soc., Dalton Trans., 1995,
3537. q) S.-I. Murahashi and T. Naota, Synlett, 1995, 733. r)
A. M. J. Jorna, E. M. Boelrijk, H. J. Hoorn, and J. Reedijk,
React. Func. Polym., 29, 101 (1996). s) T. Inoguchi, K.
Nakagawa, and S. Torii, Tetrahedron Lett., 36, 3223 (1996).
Scheme 2.
Thus we have demonstrated a new type of oxidation of
alcohols with PhI(OAc)2 and 1a, which can be sufficiently
applicable as a convenient synthetic protocol of oxidation of
alcohols. In place of PhI(OAc)2, other hypervalent iodo
compounds such as PhIO can also be used as an oxidant. We
are on the way of mechanistic investigation and isolation of
higher valent active ruthenium species, and also kinetic resolution
of secondary alcohol with 1b.
Dedicated to Prof. Teruaki Mukaiyama on the occasion of his
5th birthday.
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References and Notes
1
a) R. A. Scheldon and J. K. Kochi, in ‘‘Metal Catalyzed
Oxidation of Organic Compounds,’’ Academic Press, New
York (1981). b) S. V. Ley and A. Madin, in ‘‘Comprehensive
Organic Synthesis,’’ ed. by B. M. Trost and I. Fleming,
Pergamon, Oxford (1991), Vol. 7, p 251. c) S.-I. Murahashi
and T. Nota, in ‘‘Advances in Metal-Organic Chemistry,’’ JAI