Cyclododecane was converted to cyclododecanone and cyclo-
dodecanol with a 32% conversion after 6 h. Elemental sulfur
was also formed and filtered.
The oxidation of cyclohexane was not only limited to a 20
mmol scale. A large scale experiment was carried out (Table
3).
After 36 h the conversion of the hydrocarbon to ketone and
alcohol was 14.33%. The lower conversion value was a result of
a decrease in the rate of the reaction due to the increased
hydrocarbon to solvent ratio. After filtration of the reaction
mixture, 625 mmol of sulfur was obtained. In other experiments
A major limitation with hydrocarbon oxidation was over
oxidation of the oxygenated products.6,10 Blank experiments
were carried out to investigate the inherent stability of the
products of oxidation. The results are summarized in Table 2.
Both cyclohexanone and cyclododecanone were stable under
the oxidative conditions outlined above. It was also shown that
the ketone produced as the major oxidation product (Table 1)
was not the result of over oxidation of the alcohol. Since
essentially no over oxidation occurs over 36 h the possibility of
nearly 100% conversion of the hydrocarbon is now a realistic
target.
using variable H
quantified (Table 4).
When the flow rates of one or both of H
2 2
S and O flow rates the sulfur formed was
2 2
S and O were varied
from that of the standard flow rate (Table 4, entry 4), the total
amount of ketone and alcohol decreased. A reasonable
correlation between the amount of H
obtained was seen.
2
S used and that of sulfur
Table 2 Stability of oxygenated products in hydrogen sulfide Gif
We have developed an efficient new procedure for the
selective oxidation of hydrocarbons to the corresponding ketone
and alcohol by simply passing through a stream of oxygen and
hydrogen sulfide. At the same time we have provided an
efficient route to dispose of hydrogen sulfide gas. This
synergistic oxidation of hydrocarbons and removal of hydrogen
sulfide provides a route for the nearly quantitative conversion of
hydrocarbons to their oxygenated products. It is a significant
improvement on our original work.10
a
oxidation
Starting
material
Recovered
ketone (%)
Recovered
alcohol (%)
Others (%)
a
Cyclohexanone
Cyclohexanol
Cyclododecanone
98.6
1.5
95.6
—
98.5
—
—
b
—
c
4.4
a
FeIIICl
-tert-butylpyridine (15 mmol), MeCN (33 ml). Oxygen and hydrogen
3 2
·6H O (1 mmol), ligand (4 mmol), ketone or alcohol (20 mmol),
Although there is considerable prior work on the oxidation of
4
11
saturated hydrocarbons by non-haem systems the normal
sulfide were passed through the homogeneous solution for 4 h. The products
substitution pattern according to the C–H bond strength is
b
were analysed by GC, naphthalene was used as internal standard. Not
1
,6,12
followed. Gif chemistry is a separate subject.
In the present
c
detected. Four diketones in minor amounts.
1
work, as in general, if the picolinic acid or the pyridine base are
omitted from the system then very little oxidation takes place. A
detailed mechanistic discussion has not been presented. The
reactions differ from normal only in the enhancement of alcohol
relative to ketone.
Table 3 Conversion of cyclohexane to oxygenated products on a 784 mmol
a
scale
Cyclohexanone/ Cyclohexanol/ Total/
Conversion
(%)
Entry t/h
mmol
mmol
mmol
We thank Quest International, the Welch Foundation, the
N.S.F and the Schering Plough Corporation for the support of
this work.
1
2
3
4
5
6
7
8
4
8
15.97
22.43
31.57
34.90
43.08
47.66
55.32
78.97
4.91
8.39
20.88
30.82
41.87
46.95
60.08
66.57
77.38
2.66
3.93
5.34
5.99
7.66
8.49
9.87
12
16
20
24
28
36
10.30
12.05
17.00
18.91
22.06
33.35
References
1 D. H. R. Barton, B. Hu, D. K. Taylor and R. U. Rojas Wahl, J. Chem.
Soc., Perkin Trans. 2, 1996, 1031.
2 D. H. R. Barton, B. Hu, T. Li and J. MacKinnon, Tetrahedron Lett.,
112.32 14.33
1
996, 37, 8329.
a
FeIIICl
3 D. H. R. Barton; B. Hu, D. K. Taylor and R. U. Rojas Wahl, New.
J. Chem., 1996, 20, 121.
3
·6H
2
O (20 mmol), ligand (60 mmol), cyclohexane (784 mmol),
4
-tert-butylpyridine (150 mmol), MeCN (80 ml). Oxygen and hydrogen
sulfide were passed through the homogeneous solution. The solution was
filtered to remove the sulfur deposited and the products were analysed by
GC, naphthalene was used as internal standard.
4 D. H. R. Barton and A. Sobkowiak, New J. Chem., 1996, 20, 929 and
references there cited.
5 D. H. R. Barton and B. Chabot, Tetrahedron, 1996, 52, 10287.
6
7
D. H. R. Barton and D. Doller, Acc. Chem. Res., 1992, 25, 504.
D. H. R. Barton, M. Costas and J. MacKinnon, unpublished results.
2 2
Table 4 Effect of the amount of H S and O on ketone/alcohol formation in
presence of Fe
IIa
8 V. Schuchardt, W. A. Carvalho and E. V. Spinace, Synlett, 1993, 713.
9
F. Minisci, F. Fontana, S. Araneo and F. Recupero, J. Chem. Soc., Chem.
Commun., 1994, 1823; Tetrahedron Lett., 1994, 35, 3759; F. Minisci
and F. Fontana, Tetrahedron Lett., 1994, 35, 1427.
H
2
S/
O
2
/
Ketone/
mmol
Alcohol/
mmol
Sulfur/
mmol
21
Entry
mmol ml min
t/h
1
1
1
0 D. H. R. Barton, M. J. Gastiger and W. B. Motherwell, J. Chem. Soc.,
Chem. Commun., 1983, 41.
1 See, for example, G. K. Cook and J. M. Mayer, J. Am. Chem. Soc. 1995,
1
2
3
4
5
6
7
8
9
35
35
35
35
25
25
25
15
15
15
15
25
50
100
120
100
50
25
100
50
8
8
4
4
4
8
8
4
4
4
4
1.23
1.55
2.16
2.17
1.24
1.07
0.75
0.56
0.87
0.71
0.60
0.79
1.27
1.45
1.98
0.55
0.97
0.61
0.38
0.78
0.65
0.36
17
30
28
30
21
20
19
11
11
10
11
1
17, 7139.
2 W. Nam and J. S. Valentine, New J. Chem, 1989, 13; C. Sheu,
A. Sobkowiak, L. Zhang, N. Ozbalik, D. H. R. Barton and D. T. Sawyer,
J. Am. Chem. Soc., 1989, 111, 8030; C. Sheu, A. Sobkowiak, S. Jeon and
D. T. Sawyer, J. Am. Chem. Soc., 1990, 112, 879; C. Sheu, S. A. Rickert,
P. Cofre, B. Ross, A. Sobkowiak, D. T. Sawyer and J. R. Kanofsky,
J. Am. Chem. Soc., 1990, 112, 1936; C. Sheu and D. T. Sawyer, J. Am.
Chem. Soc., 1990, 112, 8212, and later papers from the Sawyer
group. Summarising article: V. Schuchardt, W. A. Carvalho and
E. V. Spinace, Synlett, 1993, 713, and earlier papers there cited B. Singh,
J. R. Long, G. C. Papaefthymiou and P. Stavropoulos, J. Am. Chem.
Soc., 1996, 118, 5824.
1
1
0
1
25
15
a
II
Fe Cl
2
2
·4H O (1 mmol), ligand (3 mmol), hydrocarbon (20 mmol), 4-tert-
butylpyridine (15 mmol), MeCN (33 ml). Oxygen and hydrogen sulfide
were passed through the homogeneous solution for 4–8 h. The products
were analysed by GC, naphthalene was used as internal standard. The H
is the total passed.
2
S
Received, 12th November 1996; Com. 6/07700E
558
Chem. Commun., 1997