Catalytic aerobic oxidation of cycloalkanes with nanostructured amorphous metals and alloys

Article abstract of DOI:10.1002/(SICI)1521-3773(19991203)38:23<3521::AID-ANIE3521>3.0.CO;2-S

Under mild conditions (40 atm O2, 28?°C, 10-15 h), an efficient aerobic oxidation of cycloalkanes to cycloalkanols can be achieved using nanostructured amorphous metals such as Fe and Co and an amorphous alloy like Fe₂₀Ni₈₀ as catalysts. For example, cyclohexane is oxidized to cyclohexanol with 32-41% conversion, while 1-adamantanol is formed from adamantane with 52-57% conversion.

Full text of DOI:10.1002/(SICI)1521-3773(19991203)38:23<3521::AID-ANIE3521>3.0.CO;2-S

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t1 ˆ 23.25, t2 ˆ 23.92, and 4-phenyl-hexan-2-one: Tˆ 1208C, tS ˆ 32.25, tR ˆ
33.32; b) chiral HPLC Columns: Daicel Chiralcel OD and Chiralpak AD,
particle size: 5.0 mm, column dimensions: 25 cm (length) Â 0.46 cm (i.d.),
flow ˆ 1.0 mLmin 1. 1,3-diphenyl-pentan-1-one (Chiralpak AD, 2-PrOH/
hexanes ˆ 1/99), tS ˆ 20.43, tR ˆ 29.55; 3-(4-methoxyphenyl)-1-phenyl-pen-
tan-1-one (Chiralpak AD, 2-PrOH/hexanes ˆ 10/90), tS ˆ 12.65, tR ˆ 16.83;
1-(4-methoxyphenyl)-3-phenyl-pentan-1-one (Chiralcel OD, 2-PrOH/
hexanes ˆ 10/90), tS ˆ 19.80, tR ˆ 22.37; 3-(4-chlorophenyl)-1-phenyl-pen-
tan-1-one (Chiralpak AD, 2-PrOH/hexanes ˆ 5/95), tS ˆ 10.73, tR ˆ 13.87;
and 1-(3-chlorophenyl)-4-phenyl-pentan-1-one. (Chiralpak AD, 2-PrOH/
hexanes ˆ 1/99), tS ˆ 25.73, tR ˆ 34.97.
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Received: May 26, 1999 [Z13467IE]
German version: Angew. Chem. 1999, 111, 3720 ± 3723
Keywords: additions ´ asymmetric catalysis ´ C-C coupling ´
copper ´ zinc
Catalytic Aerobic Oxidation of Cycloalkanes
with Nanostructured Amorphous Metals and
Alloys**
[1] P. Perlmutter, Conjugate Addition Reactions in Organic Synthesis,
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110, 295; Angew. Chem. Int. Ed. 1998, 37, 283.
Venkitasamy Kesavan, Pennadam S. Sivanand,
Srinivasan Chandrasekaran,* Yuri Koltypin, and
Aharon Gedanken
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The functionalization of unactivated carbon ± hydrogen
bonds in saturated hydrocarbons has been investigated for
both its synthetic and biological interest.[1] Catalytic oxidation
of alkanes has been explored using several oxidants,[2] and
those reactions with molecular oxygen under mild condi-
tions[3] are especially rewarding goals. The oxidation of
cyclohexane turns out to be the least efficient of all major
industrial processes.[4]
Typically, cyclohexane is oxidized by air (15 atm) at 1608C
in the presence of cobalt naphthenate as oxidation initiator,
giving only 4% conversion with 80% selectivity for cyclo-
hexanone and cyclohexanol.[5] The addition of boric acid to
the oxidation mixture allows approximately 10% conversion
of cyclohexane with 90% selectivity for cyclohexanone and
cyclohexanol.[5] Murahashi et al. have reported the oxidation
of cyclohexane with iron powder and observed 11% con-
version with 95% selectivity for cyclohexanone and cyclo-
hexanol.[6]
Suslick and co-workers demonstrated the first sonochem-
ical synthesis of amorphous iron particles (10 ± 20 nm) by
ultrasonic irradiation of [Fe(CO)5], and the utility of these
particles as an efficient catalyst in the Fischer± Tropsch
process.[7] They have extended this sonication synthesis to
nanophase amorphous cobalt (20 nm) and an amorphous Co/
[*] Prof. S. Chandrasekaran, V. Kesavan, P. S. Sivanand
Department of Organic Chemistry
Indian Institute of Science
[7] E. L. Stangeland, T. Sammakia, Tetrahedron 1997, 53, 16503.
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Bangalore-560012 (India)
Fax : (‡ 91)80-334-16-83
E-mail: scn@orgchem.iisc.ernet.in
Y. Koltypin, Prof. A. Gedanken
Deptartment of Chemistry, Bar-Ilan University
Ramat-Gan 52900 (Israel)
[**] The authors thank the Ministry of Science and Arts (Israel) and the
Department of Science and Technology, New Delhi (India) for a
binational India ± Israel research grant.
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Fe alloy.[8] We have investigated the sonochemical synthesis of
amorphous nickel[9] (10 nm) from [Ni(CO)4] and of amor-
phous Fe/Ni alloy[10] (Fe20Ni80, 25 nm) from a solution of
[Fe(CO)5] and [Ni(CO)4]. The amorphous nature and the
particle size were established by X-ray diffraction (XRD) and
transmission electron microscopy (TEM) measurements.[11]
Here we report the oxidation of cyclohexane with up to
40% conversion and 80% selectivity[12] for cyclohexanone
and cyclohexanol using nanostructured amorphous metals
like Fe and Co and an amorphous alloy like Fe20Ni80 with
oxygen (40 atm) at room temperature (25 ± 288C) in the
absence of any solvent. In the aerobic oxidation isobutyr-
aldehyde as coreductant and a catalytic amount of acetic acid
were used. Initially the oxidations were carried out at room
temperature under 1 atm of oxygen, and it was found that
oxygen at 40 atm gave better conversion. The results are
summarized in Table 1.
The oxidation of adamantane with various nanometals/
alloys was carried out under similar conditions (288C, 40 atm
O2), and in general the conversion was in the range of 52 ±
57%; adamantan-1-ol was the major product in all the
reactions (Table 3). It is noteworthy that our catalytic system
is quite different from the GifII system.[13] For example, the
selectivity for the tertiary or secondary C H bond on a ªper
bondº basis for the oxidation of adamantane is 10 for our
system and 0.25 for the GifII system. Interestingly no other
oxidation products were observed in our reaction (100%
selectivity).
Table 3. Aerobic oxidation of adamantane using amorphous metals/alloys
at 288C.
Nanometal/alloy
Conversion [%]
1-ol:2-ol:2-one
Fe
Co
Fe20Ni80
56
57
52
16:1:3
11:1:0.5
17:2:1
Table 1. Aerobic oxidation of cyclohexanes using amorphous metals/alloys
at 288C.[a]
Although we do not have proof for a precise mechanism at
the present stage, the reaction can be rationalized by assuming
the following pathway, which is similar to that suggested by
Murahashi et al.:[6] The reaction of isobutyraldehyde with
molecular oxygen[14] in the presence of amorphous metal/alloy
and acetic acid would give perisobutyric acid,[15] which
subsequently reacts with metal/alloy to afford a metal ± oxo
species[16, 17] along with isobutyric acid. Abstraction of a
hydrogen atom from cyclohexane with the oxo-metal species
followed by hydroxy ligand transfer to the resulting radical
would give the alcohols. Under the same reaction conditions
alcohols can be converted into ketones.
Substrate
Nanometal/
alloy
Particle
size [nm]
Conver-
one:ol[c]
sion [%][b]
cyclohexane
Fe
Co
Fe20Ni80
20
20
25
20
20
25
40
41
38
32
38
36
1:4.5
1:5
1:3.6
1:1
1:3
1:2
methylcyclohexane Fe
Co
Fe20Ni80
[a] A mixture of nanometal/alloy (0.025 g), cyclohexane (250 mmol),
isobutyraldehyde (50 mmol), and acetic acid (5 mmol) was stirred in a
Parr reactor with oxygen (40 atm) at room temperature for 10 ± 15 h.
[b] Conversion is defined as the percentage of the starting alkane converted
into products. [c] Determined by GC analysis using starting alkane as
internal standard and also by isolation of products.
The reactions presented above clearly indicate that the
nanostructured amorphous metals/alloys are superior cata-
lysts for aerobic oxidation of cycloalkanes under mild reaction
conditions.
For the oxidation of cyclohexane, use of amorphous cobalt
gave the best result at 41% conversion and 80% selectivity
for cyclohexanone and cyclohexanol. In a control reaction
where the same cycloalkanes were treated with molecular
oxygen, isobutyraldehyde, and acetic acid in the absence of
amorphous Co, Fe, or alloy as catalyst, no oxidation products
were obtained. The oxidation of methylcylohexane under
similar conditions occurs only at the secondary and tertiary
C H bonds; primary C H bonds remain unaffected. In the
reaction catalyzed by amorphous cobalt the product was a
mixture of methylcyclohexanones and methylcyclohexanols
(1:3; 2-one:3-one:4-one ˆ 28:42:30 and 1-ol:2-ol:3-ol:4-ol ˆ
65:9:15:11). When the oxidation of cyclohexane was carried
out using nanostructured Co (20 nm) as catalyst at 708C under
40 atm of oxygen for 8 h, the conversion had gone up to 67%
but there was a change in the ratio of ketone to alcohol (1:2;
Table 2).
Received: May 27, 1999 [Z13471IE]
German version: Angew. Chem. 1999, 111, 3729 ± 3730
Keywords: alkanes ´ catalysts ´ C H activation ´ nano-
structures ´ oxidations
[1] a) C. L. Hill, Activation and Functionalization of Alkanes, Wiley, New
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J. Mol. Catal. A 1993, 83, L15.
Table 2. Aerobic oxidation of cyclohexane using amorphous metals/alloys
at 708C.
Nanometal/alloy
Conversion [%]
one:ol
Fe
Co
Fe20Ni80
62
67
56
1:1.5
1:2
1:2
[4] K. V. Ingold, Aldrichimica Acta 1989, 22, 69.
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ner.[4] We have now found that the single-crystal-to-single-
crystal enantioselective photodimerization of coumarin (1a)
or thiocoumarin (1b) proceeds efficiently in inclusion com-
plexes with (R,R)-( )-trans-bis(hydroxydiphenylmethyl)-2,2-
dimethyl-1,3-dioxacyclopentane (2a) or (R,R)-( )-trans-2,3-
bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[4.4]nonane (2b),
respectively.
[5] S. Ciborowski in Studies in Surface Science and Catalysis, Dioxygen
Activation and Homogenous Catalytic Oxidation, Vol. 66 (Ed.: L. I.
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[6] S. I. Murahashi, Y. Oda, T. Naota, J. Am. Chem. Soc. 1992, 114, 7913.
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Pittsburg, 1994.
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Res. 1997, 12, 402.
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Appl. Phys. 1997, 81, 6901.
[11] Y. Koltypin, X. Cao, G. Kataby, A. Gedanken, J. Non-Cryst. Solids
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[12] The selectivity is defined as in ref. [16] as the percentage of all the
desired products out of the total amount of products.
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When a solution of a 1:1 mixture of 1a and ( )-2a in a
mixture of EtOAc and hexane was kept at room temperature
for 3 h, a 1:1 inclusion complex (4) was obtained as colorless
needles.[6] Irradiation of 4 in the solid state with a 400 W high-
pressure Hg lamp (Pyrex filter, room temperature, 4 h) gave a
2:1 complex (5)[6] of ( )-2a with ( )-3a [Eq. (1)]. The
crystals were still clear after photoirradiation and the reaction
Enantioselective Single-Crystal-to-Single-
Crystal Photodimerization of Coumarin and
Thiocoumarin in Inclusion Complexes with
Chiral Host Compounds
Koichi Tanaka, Fumio Toda,* Eiko Mochizuki,
Nobuyoshi Yasui, Yasushi Kai, Ikuko Miyahara, and
Ken Hirotsu
Dedicated to Professor Masazumi Nakagawa
on the occasion of his 83rd birthday
Some examples of single-crystal-to-single-crystal photore-
actions have been reported,[1±5] but only a few of these involve
enantioselective reactions and they are all intramolecular
photocyclization reactions.[3±5] For example, the enantioselec-
tive photocyclization of N,N-dibenzyl-1-cyclohexenecarbo-
thioamide to an optically active b-thiolactam has been
reported to proceed in a single-crystal-to-single-crystal man-
proceeded in
a
single-crystal-to-single-crystal manner
throughout the reaction. The ( )-anti-head-to-head dimer
3a was isolated by exchange with DMF. A 1:1 complex of ( )-
2a with DMF was obtained as colorless needles in 99% yield
after recrystallization of the 2:1 complex 5 from DMF/H2O
(5/1). Concentration of the filtrate left the optically pure ( )-
anti-head-to-head dimer 3a, which was isolated as colorless
prisms in 89% yield. The optical purity of ( )-3a was
determined by comparison of its [a]D value to that of
enantiomerically pure 3a.[7] Optically pure (‡)-3a was
obtained when the host compound (‡)-2a was used instead
of ( )-2a.
[*] Prof. F. Toda, Dr. K. Tanaka
Department of Applied Chemistry, Faculty of Engineering
Ehime University, Matsuyama, Ehime 790 ± 8577 (Japan)
Fax: (‡81)899-927-9923.
Dr. E. Mochizuki, Dr. N. Yasui, Prof. Y. Kai
Department of Materials Chemistry, Osaka University
Yamadaoka 2 ± 1, Suita, Osaka 565 ± 0871 (Japan)
This result shows that two molecules of 1a are arranged in
chirally related positions, which gives the optically active anti-
head-to-head dimer 3a by [2‡2] photodimerization. This
Dr. I. Miyahara, Prof. K. Hirotsu
Department of Chemistry, Faculty of Science, Osaka City University
Sugimoto-cho, Sumiyoshi-ku, Osaka 558 ± 8585 (Japan)
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