Unexpected catalyzed C=C bond cleavage by molecular oxygen promoted by a thiyl radical

Article abstract of DOI:10.1021/jo0013148

Olefin oxidation with molecular oxygen, promoted by a transition metal catalyst and a thiophenol, involved C=C bond cleavage into the corresponding carbonyl derivatives. This new reaction proceeds under one atmosphere of oxygen, at room temperature, in the presence of an excess of thiophenol and a catalyst such as MnL₂ 3a or VC1L₂ 3c. It was applied to aromatic and aliphatic olefins, as well as to functionalized or unfunctionalized acyclic compounds, providing the corresponding ketones and aldehydes in up to 98% yield. The synthetic interest of this catalytic oxidation was illustrated by a one-step preparation of the fragrance (-)-4-acetyl-1-methylcyclohexene 7e in 73% isolated yield. The C=C bond cleavage probably results from a catalyzed decomposition of the β-hydroperoxysulfide intermediate 12 that is formed by the radical addition of thiophenol to the olefin in the presence of oxygen. Although an excess of the thiophenol was used, it was transformed into the disulfide which could then be reduced without purification in 83% overall yield, thereby allowing for recycling. In addition, the C=C bond cleavage under oxygen could be promoted by catalytic quantities of the thiyl radical, generated by photolysis of the disulfide; thus, in the presence of 0.1 equiv of bis(4-chlorophenyl) disulfide 4b and 5% of the manganese complex 3a, trans-methylstilbene 1b gave, under radiation, benzaldehyde 6a and acetophenone 7a in up to 95% yield. This new reaction offers an alternative to the classical C=C bond cleavage procedures, and further developments in the fields of bioinorganic and environmental chemistry are likely.

Full text of DOI:10.1021/jo0013148

4504
J . Org. Chem. 2001, 66, 4504-4510
Un exp ected Ca ta lyzed CdC Bon d Clea va ge by Molecu la r Oxygen
P r om oted by a Th iyl Ra d ica l†
Xavier Baucherel, J acques Uziel, and Sylvain J uge´*
Unite´ mixte Universite´ de Cergy Pontoise-ESCOM, FRE CNRS 2126, Synthe`se Organique Se´lective et
Chimie Organome´tallique, 5 Mail Gay Lussac - 95031 Cergy Pontoise Cedex, France
Sylvain.J uge@chim.u-cergy.fr
Received August 31, 2000
Olefin oxidation with molecular oxygen, promoted by a transition metal catalyst and a thiophenol,
involved CdC bond cleavage into the corresponding carbonyl derivatives. This new reaction proceeds
under one atmosphere of oxygen, at room temperature, in the presence of an excess of thiophenol
and a catalyst such as MnL2 3a or VClL2 3c. It was applied to aromatic and aliphatic olefins, as
well as to functionalized or unfunctionalized acyclic compounds, providing the corresponding ketones
and aldehydes in up to 98% yield. The synthetic interest of this catalytic oxidation was illustrated
by a one-step preparation of the fragrance (-)-4-acetyl-1-methylcyclohexene 7e in 73% isolated
yield. The CdC bond cleavage probably results from a catalyzed decomposition of the â-hydro-
peroxysulfide intermediate 12 that is formed by the radical addition of thiophenol to the olefin in
the presence of oxygen. Although an excess of the thiophenol was used, it was transformed into
the disulfide which could then be reduced without purification in 83% overall yield, thereby allowing
for recycling. In addition, the CdC bond cleavage under oxygen could be promoted by catalytic
quantities of the thiyl radical, generated by photolysis of the disulfide; thus, in the presence of 0.1
equiv of bis(4-chlorophenyl) disulfide 4b and 5% of the manganese complex 3a , trans-methylstilbene
1b gave, under radiation, benzaldehyde 6a and acetophenone 7a in up to 95% yield. This new
reaction offers an alternative to the classical CdC bond cleavage procedures, and further
developments in the fields of bioinorganic and environmental chemistry are likely.
In tr od u ction
oxidations using hydrogen peroxide or molecular oxygen9
have attracted increasing attention because of their
environmentally friendly byproducts. Although catalytic
oxidation of organic substrates by molecular oxygen is
highly desirable for its simplicity, in most cases10 it
requires the use of an aldehyde,11 2-propanol, or a â-keto
ester12 in stoichiometric amounts.
Considerable progress has been made in the field of
catalytic olefin oxidation since the advent of industrial
production of acetaldehyde1 and ethylene oxide.2 Conse-
quently, numerous catalyzed epoxidation3-5 or dihy-
droxylation reactions6 and ketone7 or R-hydroxyketone8
syntheses are now recognized as classical methods.
Moreover, from an ecological point of view, catalytic
(4) For pertinent references on catalyzed enantioselective epoxida-
tion of allylic alcohols, see: (a) Gao, Y.; Hanson, R. M.; Klunder, J .
M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J . Am. Chem. Soc. 1987,
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Asymmetric Synthesis; Ojima, I., Ed.; VCH: New York, 1993; chapter
4, pp 103-158.
(5) For examples of catalyzed enantioselective epoxidation of un-
functionalized olefins, see: (a) J acobsen, E. N. In Catalytic Asymmetric
Synthesis; Ojima, I., Ed.; VCH: New York, 1993; chapter 4, pp 159-
202. (e) P. Pietika¨inen, Tetrahedron Lett. 1994, 35 (6) 941-944. (f)
Fukuda, T.; Irie, R.; Katsuki, T. Synlett. 1995, 197-198. (g) Palucki,
M.; Finney, N. S.; Pospisil, P. J .; Gu¨ler, M. L.; Ishida, T.; J acobsen, E.
N. J . Am. Chem. Soc. 1998, 120, 948-954.
* To whom correspondence should be addressed. Fax: 33 1 34 25
70 67.
† This work was presented in part at the seventh International
Symposium on Dioxygen Activation (ADHOC-99), J uly 19-23, 1999,
York, UK.
(1) (a) Hagemeyer, H. J . In Encyclopedia of Chemical Technology,
4th ed.; Kroschwitz, J ., Ed.; Kirk-Othmer, Wiley: New York, 1991; Vol.
1, pp 100-102. (b) J ira, R. In Applied Homogeneous Catalysis with
Organometallic Compounds; Cornil, B.; Herrmann, W. A., Eds.; VCH:
Weinheim, 1996; Vol. 1, pp 374-393.
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Encyclopedia of Chemical Technology, 4th ed.; Kroschwicz, J ., Ed.;
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R. A. In Applied Homogeneous Catalysis with Organometallic Com-
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Vol. 1, pp 411-423.
(3) For representative examples of catalytic epoxidation of olefins,
see: (a) Mimoun, H.; Saussine, L.; Daire, E.; Postel, M.; Fisher, J .;
Weiss, R. J . Am. Chem. Soc. 1983, 105, 3101-3110. (b) Groves, J . T.;
Quinn, R. J . Am. Chem. Soc. 1985, 107, 5790-5792. (c) Koola, J . D.;
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Hoek, D.; Sheldon, R. A. Tetrahedron 1996, 12971-12978. (i) Cope´ret,
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M. C. J . Am. Chem. Soc. 1995, 117, 10805-10816. (c) Shing, T. K. M.;
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1982, 104, 6782-6784. (b) Mukaiyama, T.; Isayama, S.; Inoki, S.; Kato,
K.; Yamada, T.; Takai, T. Chem. Lett. 1989, 449-452. (c) Inoki, S.;
Kato, K.; Takai, T.; Isayama, S.; Yamada, T.; Mukaiyama, T. Chem.
Lett. 1989, 515-518. (d) Kato, K.; Yamada, T.; Takai, T.; Inoki, S.;
Isayama, S. Bull. Chem. Soc. J pn. 1990, 63, 179-186. (e) Inoki, S.;
Kato, K.; Isayama, S.; Mukaiyama, T. Chem. Lett. 1990, 1869-1872.
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Organic Compounds; Academic Press: New York, 1981. (b) Sawyer,
D. T. Oxygen Chemistry; Oxford University Press: New York, 1991.
(c) The Activation and Homogeneous Catalytic Oxidation; Barton, D.
H. R.; Martell, A. E.; Sawyer, D. T., Eds.; Plenum Press: New York,
1993.
10.1021/jo0013148 CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/26/2001

Unexpected Catalyzed CdC Bond Cleavage
J . Org. Chem., Vol. 66, No. 13, 2001 4505
Ta ble 1. C)C Bon d Clea va ge of Stilben e 1a w ith O2
Sch em e 1
reaction conditionsa
PhCHO 6a
entry ArSH catalyst acid
yieldb (%) time (h)
1
2
3
4
5
6
2a
c
c
c
2b
c
3a
none
3a
MnCl2
3a
3c
none
c
H3PO4 (0.2 equiv)
c
c
c
70
12
75
63
78
94
15
48
6
15
8
4
a
All reactions were carried out in acetone under 1 atm of oxygen
at room temperature, with trans-stilbene 1a (0.1M), catalyst (5%
mol), and thiophenol 2 (4 equiv.). Determined by GC. c Same as
entry above.
b
To investigate new reductants for the well-known
catalyzed epoxidation of olefins by oxygen, we used the
thiols 2, expecting the formation of the disulfide 4, which
could then be easily recycled by simple reduction or
irradiation (Scheme 1). However, using the thiophenol
2, the catalytic oxidation of trans-stilbene 1 in the
presence of the transition metal complex 3 did not give
the expected epoxide 5 (Scheme 1, eq 1), but produced
instead CdC bond cleavage in high yield (eq 2).
Although the oxidative cleavage of double bonds can
be performed by NaIO4 in the presence of osmium13 or
ruthenium tetraoxide,14 only a few examples of catalytic
oxidation using molecular oxygen as the terminal oxi-
dant15 have been reported. We now report here the
unexpected CdC bond cleavage by molecular oxygen,
promoted by thiophenol and related derivatives.
2a 16 and 5% of the manganese complex 3a , the conversion
of stilbene 1a was complete in 15 h, furnishing benzal-
dehyde 6a in 70% yield (Table 1, entry 1). Under these
conditions, no significant formation of the epoxide, diol,
or benzoic acid was observed. Similar results were
obtained using dichloromethane, ethyl acetate, toluene,
methanol, or acetonitrile as the solvent. Without a
catalyst, the conversion of stilbene was slower, and
benzaldehyde was obtained in only 12% yield after 48 h
(entry 2).
When 0.2 equiv of phosphoric acid or a weak acid17
were added to the reaction mixture, the reaction pro-
ceeded more rapidly, affording benzaldehyde in 75% yield
after 6 h (entry 3). The CdC bond cleavage also occurred
in the presence of 5% manganese(II) chloride or cobalt(II)
chloride as the catalyst, since 1a was completely con-
sumed in 15 h, giving benzaldehyde 6a in 63% yield
(entry 4). On the other hand, when 4-chlorothiophenol
2b was used, benzaldehyde was obtained in 78% yield
in 8 h (entry 5). However, no appreciable improvement
was observed with other aliphatic or aromatic thiols.18
The best results were obtained using 4-chlorothiophenol
2b with the vanadium catalyst VClL2 3c. Thus, in
acetone under oxygen at room temperature and in the
presence of phosphoric acid (0.2 equiv), 1a led to benzal-
dehyde 6a in 94% yield in 4 h (entry 6).
It is noteworthy that the NaBH4 reduction19 of the
crude disulfide 4a (or 4b) gave back the thiophenols 2a
or 2b in 83% overall yields.
The oxidation of several aromatic olefins was studied
(Table 2) using the best reaction conditions.
In the presence of the MnL2 complex 3a and thiophenol
2a , conversion of trans-methylstilbene 1b gave, in 4 h,
benzaldehyde 6a and acetophenone 7a in 95% and 98%
yields, respectively (entry 3). Monitoring the reaction
mixture by GC showed that acetophenone formation was
concomitant with olefin disappearance; however, benzal-
dehyde appeared more slowly and only reached a maxi-
mum after 4 h (Figure 1). It should be pointed out that
complete conversion of the olefin required the consump-
tion of 3 equiv of thiol over 2 h (Figure 1).
Resu lts a n d Discu ssion
Clea va ge of Ar om a tic Olefin s. First, the reaction
was investigated using trans-stilbene 1a with oxygen (1
atm) in the presence of the thiophenols 2a or 2b and 5%
mol equiv of the transition metal complexes 3a -c or of
the salts (MnCl2, CoCl2). The complexes 3a -c were
prepared by mixing a solution of the corresponding
transition metal chloride (1 equiv) with the ligand 10 (2
equiv), which was previously prepared by condensation
of salicylaldehyde 8 with methyl serinate 9 (Scheme 2).
When the reaction was performed in acetone at room
temperature in the presence of 4 equiv of the thiophenol
(10) For examples of catalytic olefin oxidation with oxygen and
without any associated reductant, see: preparation of ethylene oxide,2a
epoxidation or dihydroxylation, respectively, in the presence of a
ruthenium porphyrin catalyst,3b or osmium: Do¨bler, C.; Mehltretter,
G.; Beller, M. Angew. Chem., Int. Ed. 1999, 38, 3026-3028.
(11) Mukaiyama, T.; Yamada, T. Bull. Chem. Soc. J pn. 1995, 68,
17-35.
Although the reaction was slightly slower, very good
(12) (a) Punniyamurthy, T.; Iqbal, J . Tetrahedron Lett. 1994, 35,
4003-4006. (b) Punniyamurthy, T.; Bhatia, B.; Reddy, M. M.; Maikap,
G. C.; Iqbal, J . Tetrahedron 1997, 53, 7649-7670.
(16) Thiophenol 2a , which was provided by Clariant SA (BP1, Trosly
Breuil 60350, France), is nearly odorless.
(17) Use of formic, acetic, trichloroacetic, or benzoic acid gave also
satisfactory yields.
(18) Use of 4-bromo-, 3,4-dichloro-, 2,3,5,6-tetrafluorothiophenol,
2-mercaptobenzoic acid, 2-mercaptonaphthalene, or 2-mercaptopyrim-
idine in the oxidation reaction often led to incomplete conversion of
the olefin and formation of the aldehyde in poor yields. When
thioethanol or dodecanethiol was used in the presence of 5% MnL2
3a , stilbene 1a did not react at room temperature after 24 h.
(19) Ookawa, A.; Yokohama, S.; Soai, K. Synth. Commun. 1986, 16,
819-825.
(13) (a) Pappo, R.; Allen, D. S., J r.; Lemieux, R. U.; J ohnson, W. S.
J . Am. Chem. Soc. 1956, 21, 478-479.
(14) (a) Carlsen, P. H. J .; Katsuki, T.; Martin, V. S.; Sharpless, K.
B. J . Org. Chem. 1981, 46, 3936-3938. (b) Torii, S.; Inokuchi, T.,
Kondo, K. J . Org. Chem. 1985, 50, 4980-4982.
(15) (a) Kaneda, K.; Haruna, S.; Imanaka, T.; Kawamoto, K. J .
Chem. Soc., Chem. Commun. 1990, 1467-1468. (b) Barton, D. H. R.;
Wan Lee, K.; Mehl, W.; Ozbalik, N.; Zhang, L. Tetrahedron 1990, 46,
3753-3768. (c) Reetz, M. T.; To¨llner, K. Tetrahedron Lett. 1995, 36,
9461-9464. (d) Herrmann, W. A.; Weskamp, T.; Zoller, J . P.; Fischer,
R. W. J . Mol. Catal. A: Chem. 2000, 153, 49-52.

4506 J . Org. Chem., Vol. 66, No. 13, 2001
Baucherel et al.
Sch em e 2
Ta ble 2. Ap p lica tion to Va r iou s Ar om a tic Olefin s
a
All reactions were carried out in acetone under 1 atm of oxygen at room temperature in the presence of 0.2 equiv of H3PO4; Conditions
A: thiophenol 2a (4 equiv), catalyst 3a (5% mol); B: thiophenol 2b (4 equiv), catalyst 3c (5% mol). Determined by GC. c Isolated yield.
b
F igu r e 1. Kinetic study of the catalyzed CdC bond cleavage of trans-methylstilbene 1b into acetophenone 7a and benzaldehyde
6a .
results were also obtained with CoL2 3b, Cr(acac)3, Mn-
(acac)2, or V(acac)3 as the catalysts.
hyde was then formed at a rate corresponding to the
disappearance of the thiophenol 2a , and the yield reached
75% after 8 h (Figure 2). Ultimately the result was
comparable to that obtained starting from trans-stilbene
1a (entry 1).
Under standard conditions A, the reaction of cis-
stilbene 1c gave benzaldehyde in 75% yield in 8 h (entry
4). GC analysis of the reaction showed rapid conversion
of the cis-1c into its trans isomer 1a without any
consumption of the thiophenol 2a (Figure 2). Benzalde-
The same conditions have also been successfully ap-
plied to styrene 1d and diphenylethene 1e (entries 5, 6).

Unexpected Catalyzed CdC Bond Cleavage
J . Org. Chem., Vol. 66, No. 13, 2001 4507
F igu r e 2. Kinetic study of the catalyzed CdC bond cleavage of cis-stilbene 1c into benzaldehyde 6a .
Ta ble 3. Oxid a tion of Va r iou s Alip h a tic Olefin s
a
All reactions were carried out in acetone under 1 atm of oxygen at room temperature, using for conditions A: Mn-catalyst 3a (5%
mol)/thiophenol 2a (5 equiv); B: V-catalyst 3c (5% mol)/thiophenol 2b (5 equiv). Determined by GC. c Isolated yield.
b
However, in the case of the cyclic olefin 1f, the expected
dialdehyde 6b was obtained in low yield (entry 7).
Clea va ge of Alip h a tic Olefin s. Under the oxidation
conditions A shown above, vinylcyclohexane 1g reacted
very slowly giving cyclohexanecarboxaldehyde 6c in 34%
yield after 6 days (Table 3, entry 1). Using 4-chloro-
thiophenol 2b or ethyl acetate as the solvent, the reaction
produced comparable results. The best conditions were
obtained with the vanadium complex 3c20 as the catalyst,
when the conversion of vinylcyclohexane 1g reached
100% after 24 h, giving the cyclohexanecarboxaldehyde
6c in 58% yield (entry 2). It should be noted that the
appearance of cyclohexanecarboxaldehyde 6c was not
accelerated by the presence of an acid in the reaction
mixture.
the cleavage of several terpenes. â-Pinene 1j gave nopi-
none 7d in 68% isolated yield (entry 5), while more
interestingly, the regioselective cleavage of the acyclic Cd
C bond of the (S)-(-)-limonene 1k gave in one step and
in 73% isolated yield the fragrance (S)-(-)-7e, which had
been previously prepared in three steps and in 38%
overall yield from 1k (entry 6).21
Clea va ge of F u n ction a lized Olefin s. Under the
reaction conditions A, trans-cinnamic alcohol 1l, cinnamic
acid 1m , and ethyl cinnamate 1n underwent CdC bond
cleavage, providing benzaldehyde 6a in yields up to 73%
(Table 4, entries 1-3). In the last case, the reaction was
faster, and ethyl glyoxylate 6e was obtained in 53% yield;
however, when the reaction was carried out under the
conditions B, the yields improved (entry 4). Finally, ethyl
fumarate 1o also underwent CdC bond cleavage, to form
ethyl glyoxylate 6e in 41% yield over 48 h (entry 5).
Although the reaction was rather slow, these results
demonstrate that our method for CdC bond cleavage is
Using reaction conditions B as reported in Table 3,
1-octene 1h led to heptanal 6d in 58% yield over 24 h
(entry 3), while 2-methyl-1-hexene 1i gave 2-hexanone
7c in 74% yield in only 4 h (entry 4). We also investigated
(20) Use of commercialy available vanadium oxo bis (1-phenyl-1,3-
dibutanedionate) or V(acac)3 complexes led to similar results.
(21) J o Davisson, V.; Dale Poulter, C. J . Am. Chem. Soc. 1993, 115,
1245-1260.

4508 J . Org. Chem., Vol. 66, No. 13, 2001
Ta ble 4. Oxid a tion of Va r iou s F u n ction a lized Olefin s
Baucherel et al.
a
All reactions were carried out in acetone under 1 atm of oxygen at room temperature; Conditions A: thiophenol 2a (4 equiv)/Mn-
catalyst 3a (5% mol)/H3PO4 (0.2 equiv); B: thiophenol 2b (5 equiv)/catalyst 3c (5% mol)/without acid. Determined by GC. c Based on
b
unrecovered olefin.
Sch em e 3
also effective with unsaturated compounds bearing elec-
tron-withdrawing substituents.
any other reaction (Figure 2) are in agreement with the
reversible addition of the thiyl radical to the olefin 1
(Scheme 3). The improvement observed with 4-chloro-
thiophenol 2b also confirms this mechanism, since it is
known that the thiyl radical polarity (i.e., p-ClPhS‚)
favored this addition.23c,d
Mech a n ism of th e CdC Bon d Clea va ge. It is known
that addition of the thiyl radical ArS• to an olefin 1 is
reversible, but the resulting radical 11 can be trapped
by oxygen to provide the hydroperoxysulfide 12, which
then undergoes rearrangement to â-hydroxysulfoxide 13
(“TOCO” reaction; Scheme 3, eq 1).22,23
The fact that thiophenol was essential for the CdC
bond cleavage and that the cis-trans isomerization of
cis-stilbene 1c into trans-stilbene 1a was observed before
On the other hand, since the â-hydroxysulfoxide 13 did
not lead to the carbonyl products 6 and 7 (Scheme 3, eq
1), the carbon-carbon bond cleavage probably arises from
the decomposition of the â-hydroperoxysulfide 12, cata-
lyzed by the transition metal complexes MLn (eq 2). Thus,
it is reasonable to assume that the decomposition of 12
provides the carbonyl compound 7 and the hemithioacetal
14, leading to the aldehyde 6. Consequently, the fact that
the radical addition to the olefin occurs on the less
substituted carbon atom (anti-Markovnikov) may explain
the slower formation of the aldehyde 6 than of the ketone
7, as observed in trans-methylstilbene 1b (Figure 1). The
regioselectivity and the better reactivity observed for the
bond cleavage of limonene 1k , and the acyclic olefins
(22) (a) Kharash, M. S.; Nudenberg, W.; Mantell, G. J . J . Org. Chem.
1951, 16, 524-532. (b) Oswald, A. A.; Wallace, T. J . In The Chemistry
of Organic Sulfur Compounds; Kharash, N., Meyers, C. Y., Eds.;
Pergamon: J .; Oxford, 1966; pp 205-422. (b) Iriuchijima, S.; Maniwa,
K.; Sakakibara, T.; Tsuchihashi, G. J . Org. Chem. 1974, 39, 1170-
1171. (c) Szmant, H. H.; Mata, A. J .; Namis, A. J .; Panthananickal, A.
M. Tetrahedron 1976, 32, 2665-2680.
(23) (a) Ito, O.; Matsuda, M. J . Am. Chem. Soc. 1979, 101, 1815-
1819. (b) Ito, O.; Matsuda, M. J . Am. Chem. Soc. 1979, 101, 5732-
5735. (c) Ito, O.; Matsuda, M. J . Am. Chem. Soc. 1981, 103, 5871-
5874. (d) Ito, O.; Matsuda, M. J . Am. Chem. Soc. 1982, 104, 1701-
1703.

Unexpected Catalyzed CdC Bond Cleavage
J . Org. Chem., Vol. 66, No. 13, 2001 4509
Sch em e 4. P h otoin d u ced CdC Bon d Clea va ge
Ca ta lyzed by th e Disu lfid e 4b a n d th e Tr a n sition
Meta l Com p lex 3a
Promising selectivity was demonstrated by the cleavage
of the acyclic double bond of limonene 1k , which yielded
in one step the ketone 7e in 73% yield. Although this
catalyzed CdC bond cleavage requires 4 equiv of thiophe-
nol 2a (or 2b) as the coreagent, the disulfide produced
as the byproduct can be readily reduced in very good
yield, without any purification. Moreover, we have shown
that a disulfide can be used as a catalytic thiyl radical
precursor. Thus, by photolysis with a medium-pressure
mercury lamp, 0.1 equiv of disulfide was sufficient to
bring the reaction of trans-methylstilbene 1b with oxygen
to completion in 2 h, giving the corresponding carbonyl
derivatives.
Ta ble 5. P h otoin d u ced CdC Bon d Clea va ge of
tr a n s-Meth ylstilben e 1b u n d er Oxygen Bu bblin g
reaction conditionsa
products
The present system for the oxidation of olefins cata-
lyzed by transition metal complexes or salts offers an
alternative to the classical CdC bond cleavage proce-
dures, and new developments in the fields of bioinorganic
and environmental chemistry are likely.
entry 4b/1b ratio conversion timeb (h)
yieldsb(%) time (h)
1
2
3
0.5
0.5
0.5
2
6a
7a
6a
7a
6a
7a
73
95
55
91
40
95
0.5
1.5
1
3
2
0.25
0.1
Exp er im en ta l Section
8
a
All reactions were carried out in ethyl acetate under oxygen
Gen er a l P r oced u r es. Solvents were dried and freshly
distilled under a nitrogen atmosphere over sodium/benzophe-
none for THF, CaH2 for acetone, ethyl acetate, methylene
chloride, chloroform, and acetonitrile, and sodium alcoholate
for EtOH and i-PrOH. Oxygen gas was purchased from Air
Liquide and used as received. 4-Chlorothiophenol, Cr(acac)3,
cinnamic acid, cinnamic alcohol, ethyl cinnamate, ethyl fu-
marate, dihydronaphthalene, (-)-limonene, â-pinene, cis- or
trans-stilbene, trans-methylstilbene, styrene, 1,1-diphenyl-
ethene, V(acac)3, VCl3, and vanadium oxo bis(1-phenyl-1,3-
dibutanedionate) were purchased from Aldrich, Acros, Avo-
cado, and Fluka. All compounds were purified by either
vacuum distillation or recrystallization before use. MnCl2 and
CoCl2 were dried by heating at 100 °C.
bubbling, at room temperature, under radiation by medium-
pressure mercury lamp through Pyrex. Determined by GC.
b
1d ,e,g-j (Table 2, 3), can also be interpreted by this
mechanism.
P h otoin d u ced CdC Bon d Clea va ge. Since thiyl
radicals can be formed from aromatic disulfide photoly-
sis,22 we applied this activation process to promote the
CdC bond cleavage by oxygen under totally catalytic
conditions (Scheme 4).
In the absence of a catalyst, the photolysis of trans-
stilbene 1a under oxygen, performed by irradiation with
a medium-pressure mercury lamp through Pyrex in the
presence of thiophenol 2a , led to the formation of the
corresponding â-hydroxysulfoxide 13.
Photolysis of trans-methylstilbene 1b under oxygen in
the presence of a catalytic amount of the manganese
complex 3a and bis(4-chlorophenyl)disulfide 4b gave
acetophenone 7a and benzaldehyde 6a with the speed of
the reaction depending on the 4b/1b ratio (Table 5).
Using 0.5 or 0.25 equiv of disulfide 4b, the reaction
proceeded quite rapidly, and acetophenone 7a was ob-
tained in up to 95% yield. The benzaldehyde yields
reached 73%, but decreased under the oxidation condi-
tions (entries 1, 2). When the reaction was carried out
with 0.1 equiv of disulfide 4b, the conversion of 1b was
slower and acetophenone was produced in good yield
(95%), while benzaldehyde 6a was formed in only 40%
yield (entry 3).
GC analysis of reactions with aromatic olefins, cinnamic
alcohol, and cinnamic acid were performed with dodecane (1%)
as an internal reference using a Carlo Erba GC 6000 (Vega
series 2), equipped with an Alltech AT-WAX (30 m × 0.32 mm
i.d. × 0.5 µm film) column and fitted with a 1020 Perkin-Elmer
integrator. The programming of temperature was carried out
from 110 to 230 °C at 10 °C/min (hold 30 min). Oxidation of
trans-stilbene was also analyzed on a DB-5 (J &W Scientific)
(30 m × 0.32 mm i.d.) column with temperature program from
70 °C to 80 °C at 5 °C/min, 80 °C to 230 °C at 15 °C/min (hold
15 min). GC analyses of vinylcyclohexane, ethyl cinnamate,
diethyl fumarate, limonene, 2-methylhexene, 1-octene, and
â-pinene were performed with dodecane (1%) as an internal
reference and using a Perkin-Elmer Autosystem. It was
equipped with a RESTEK RTX 1- SE 30 (100% dimethylpoly-
siloxane; 30 m × 0.32 mm × 0.5 µm film) column and fitted to
a 1020 Perkin-Elmer integrator. The oven temperature was
programmed from 80 to 310 °C at 10 °C/min (hold 30 min).
The ethyl glyoxylate was compared to an authentic sample of
the corresponding hemiacetal with EtOH furnished by Clari-
ant SA. GC-MS analyses were performed on a Nermag R10-
10C mass spectrometer, coupled with a Varian gas chroma-
tography equipped with Chrompack CP-Sil-5 (30 m × 0.25 mm
i.d. × 0.25 µm film) column, with temperature program from
90 to 310 °C at 5 °C/min. All photolyses were conducted in a
temperature-controlled water bath (25 °C), with a Mazda
medium-pressure mercury 250 W lamp fitted with a Pyrex
sleeve. Thin-layer chromatography was performed on silica
chromagel (60 F254; SDS) and exposed by UV or permanganate
treatment. Flash chromatography was performed on silica gel
(60ACC, 6-35 µm; SDS). All NMR spectra were recorded on
a Bruker DPX 250 spectrometer using TMS as internal
Con clu sion
We have herein reported the first example of a catalytic
CdC bond cleavage, at room temperature, of olefins
under an oxygen atmosphere into aldehydes and ketones
in good to excellent yields. This new reaction resulted
from transition metal catalyzed decomposition of the
â-hydroperoxysulfide 12 formed in situ from thiyl radical
addition to the double bond, followed by oxygen trapping.
A study of the reaction showed that it can be performed
in a majority of common solvents and catalyzed by
various transition metal salts or complexes. It is par-
ticularly suited for acyclic substrates, and several ex-
amples showed that the reaction was compatible with
other functional groups such as alcohols, esters, or acids.
1
reference for H and 13C NMR. Melting points were measured
on a Buchi melting point apparatus and are uncorrected.
Optical rotation values were determined at 20 °C on a Perkin-
Elmer 241 polarimeter. Infrared spectra were recorded on a
Bruker Equinox 55. Mass spectral analyses were performed

4510 J . Org. Chem., Vol. 66, No. 13, 2001
Baucherel et al.
[R]D20 ) +36.5, lit.25 [R]2D0 ) +36.9 (c 4, MeOH); IR (neat, ν
cm-1): 2949 (s), 1711 (s); 1H NMR (CDCl3): δ 0.85 (3H, s, CH3),
1.33 (3H, s, CH3), 1.59 (1H, m, CH), 1.94-2.07 (2H, m, CH2),
2.23-2.39 (2H, m, CH2), 2.50-2.59 (3H, m). 13C NMR
(CDCl3): δ 21.3 (CH2CH2CO), 22.0 (CH3), 25.1 (CHCH2CH),
25.8 (CH3), 32.7 (CH2CO), 40.3 (CH2CHCH2), 41.1 (C(CH3)2),
57.8 (CHCO), 214.6 (CO); MS (EI) m/z (relative intensity): 108
(60), 69 (m/2z; 100), 55 (86); MS (DCI; CH4) m/z (relative
on a NERMAG R10-10C and a J EOL MS 700 for exact mass,
at the Mass Spectroscopy Laboratories of ENSCP and ENS
Paris, respectively. The major peak m/z is mentioned with the
intensity as a percentage of the base peak in brackets.
Elemental analyses were measured with a precision superior
to 0.3% at the Microanalysis Laboratory of P. & M. Curie
University (Paris).
P r ep a r a tion of Meth yl 2-N-Sa licylid en e-3-h yd r oxyp r o-
p a n oa te 10 Liga n d a n d Its Cor r esp on d in g ML2 Com -
p lexes. Following a literature procedure,12 in a 50 mL round-
bottomed flask equipped with a magnetic stirrer, 1.09 g (7
mmol) of methyl D,L-serinate hydrochloride24 was introduced
in 35 mL of EtOH, and triethylamine (1.1 mL; 7.9 mmol) was
added under stirring at room temperature. Then 0.75 mL of
salicylaldehyde 8 (7 mmol) was added, and the mixture was
stirred for 5 h. After removal of the solvent, the residue was
purified by chromatography on silica gel using acetonitrile as
eluent. The ligand was obtained as a yellow oil. Rf ) 0.8
(acetonitrile); yield 1.45 g, 93%; IR (neat, ν cm-1): 3444 (vs),
1740 (s), 1632 (w), 1279 (m); 1H NMR (CDCl3): δ 3.54 (3H, s,
CH3), 3.72 (1H, m, CH), 3.92 (2H, m, CH2), 6.64-6.71 (2H, m,
H arom), 7.04-7.12 (2H, m, H arom), 8.18 (1H, s, CHPh), 12.50
(1H, sl, OH); 13C NMR (CDCl3): δ 52.6 (CH3), 63.6 (CH2O),
72.7 (CH), 117.2 (CH arom), 118.6 (C arom), 119.0 (CH arom),
132.1 (CH arom), 133.1 (CH arom), 160.9 (C arom), 168.6
(CHPh), 170.4 (CO2Me); MS (EI; CH4) m/z (relative inten-
sity): 223(62), 192(26), 164(38), 132(100), 107(67), 77(29);
HRMS (EI) calcd for C11H13NO4: 223.0844; Found: 223.0844.
The complexes 3a -c were prepared by mixing a solution of
the ligand 10 (2 equiv) with the corresponding transition metal
chloride (1 equiv) and were used without further purification.
CdC Bon d Clea va ge u n d er Oxygen a n d in th e P r es-
en ce of Th iop h en ol. Typ ica l P r oced u r e. In a 25 mL round-
bottomed flask equipped with a magnetic stirrer and a rubber
septum containing the unsaturated compound 1a -o (1 mmol)
were added 22 mg of the ligand 10 (0.1 mmol) and 6.3 mg of
MnCl2 (conditions A), or 7.9 mg of VCl3 (conditions B) and 10
mL of acetone. Then, 4 equiv of thiophenol 2a (or 2b; 4 mmol)
was added, and the flask was subjected to three vacuum/O2
cycles, before pressurizing to 1 atm with a balloon of O2. After
addition of 0.2 equiv of H3PO4, the reaction medium was
stirred at room temperature and the reaction was monitored
by GC. Upon completion, the reaction mixture was filtered
through a short column of silica gel (3 cm), which was washed
with 2 × 50 mL of EtOAc. After removal of the solvent, the
residue was purified either by silica gel chromatography with
cyclohexane as eluent or distilled under vacuum using a bulb
to bulb Kugelrohr apparatus, to afford the carbonyl com-
pound(s) and a residue containing the disulfide 4a (or 4b).
(1R,5S)-(+)-Nop in on e 7d fr om (-)-â-P in en e 1j. In a 50
mL round-bottomed flask were introduced 19 mg of VCl3 (0.12
mmol), 53.8 mg of ligand 10 (0.242 mmol), and 10 mL of
acetone, under oxygen. After 20 min of stirring at room
temperature, 326 mg of â-pinene 1j (2.4 mmol; [R]2D0 ) -19
neat), 1.39 g of 4-chlorothiophenol 2b (9.6 mmol), and 15 mL
of acetone were added and then stirred at room temperature
for 20 h. After removing the solvent, the residue was distilled
using a bulb to bulb Kugelrohr apparatus under vacuum (bp
) 130 °C; 20 mmHg) to give 297 mg of the crude pinanone
7d , which was repurified by silica gel chromatography using
a mixture of pentane/diethyl ether (4:1) as eluent. Colorless
oil. Rf ) 0.2 (petroleum ether/diethyl ether); yield 226 mg, 68%;
intensity): 139 (MH+); HRMS (DCI, CH4) calcd for C9H15
(MH+): 139.1123; Found: 139.1125.
O
(S)-(-)-4-Acet yl-1-m et h ylcyclo-1-h exen e 7e fr om (S)-
(-)-Lim on en e 1k . In a 50 mL round-bottomed flask were
introduced 25 mg of VCl3 (0.16 mmol), 71 mg of ligand 10 (0.32
mmol), and 15 mL of acetone, under oxygen. After 20 min of
stirring at room temperature, 407 mg of (S)-(-)-limonene 1k
(3 mmol; [R]2D0 ) -100 (c 10, EtOH), 2.16 g of 4-chloro-
thiophenol 2b (14.95 mmol, 5 equiv), and 15 mL of acetone
were added and stirred at room temperature for 15 h. After
removal of the solvent, the residue was distilled using a bulb
to bulb Kugelrohr apparatus under vacuum (bp ) 120 °C; 1
mmHg), to give 430 mg of the crude ketone 7e and 2.47 g of a
residue, which was purified by chromatography using cyclo-
hexane as eluent, to give the disulfide 4b (1.88 g; yield 87%).
The final purification of 7e was carried out by silica gel
chromatography using a mixture of pentane/diethyl ether (95:
5) as eluent. Colorless oil. Rf ) 0.4 (petroleum ether/diethyl
ether 9:1); yield 300 mg, 73%; [R]2D0 ) -97 (c 3.6, CHCl3), lit.21
[R]2D0 ) -92 (c 6.3, CHCl3); IR (neat, ν cm-1): 2920 (s), 1709
(s), 1440 (m), 1362 (m), 1162 (m); 1H NMR (CDCl3): δ 1.65
(4H, m), 1.96 (3H, m, CH3CdC), 2.18 (5H, m), 2.48-2.58 (1H,
m, CHCO), 5.39 (1H, sl, CdCH); 13C NMR (CDCl3): δ 23.5
(CH3CdC), 25.0 (CH2), 27.1 (CH2), 28.1 (COCH3), 29.6 (CH2),
47.3 (CHCO), 119.3 (C)CH), 133.9 (C)CCH3), 212.1 (CO); MS
(EI) m/z (relative intensity): 138 (86), 123 (58), 95 (100); MS
(DCI; CH4) m/z (relative intensity): 139 (MH+; 100), HRMS
(DCI, CH4) calcd for C9H15O (MH+): 139.1123; Found: 139.1120.
P h otoin d u ced CdC Clea va ge of tr a n s-Meth ylstilben e
1b u n d er Oxygen a n d in th e P r esen ce of th e Disu lfid e
4b a n d th e Mn -Com p lex 3a . Typ ica l P r oced u r e. In an
annular Pyrex reactor, equipped with
a diving mercury
medium-pressure lamp 250 W, 194 mg of trans-methylstilbene
1b (1 mmol), 6.3 mg of MnCl2 (0.05 mmol), 22.3 mg of the
ligand 10 (0.1 mmol), and 10 mL of EtOAc were introduced.
The solution was irradiated under oxygen bubbling, and the
reaction was monitored by GC.
Ack n ow led gm en t. S.J . gratefully acknowledges the
Association Paul Neumann of the French Hoechst
Society (now Clariant) for financial support, and thanks
D. Mansuy and G. Mattioda for helpful discussions. We
also thank J . Salau¨n for his help in the preparation of
the manuscript, and N. Morin and N. Sellier for obtain-
ing HRMS and GCMS data.
Su p p or tin g In for m a tion Ava ila ble: Formation of 3-(2-
carboxaldehyde phenyl)propanal 6b and â-hydroxysulfoxide 13
by photolysis. Recycling of the disulfide 4b. This material is
available free of charge via the Internet at http://pubs.acs.org.
J O0013148
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