Reactions of alcohols with cesium fluoroxysulfate

Article abstract of DOI:10.1021/jo962424a

The reactions of alcohols with cesium fluoroxysulfate (CsSO₄F) in MeCN suspension were studied, and the role of the structure of the alcohol and the reaction conditions on the course of reaction was determined. Secondary benzyl alcohols bearing a nonactivating aromatic ring were selectively oxidized to the corresponding ketones, while the CsSO₄F-mediated reaction of phenyl-1-naphthylmethanol resulted in the formation of 1-fluoronaphthalene and benzaldehyde. Cyclic and noncyclic secondary alcohols were readily converted to ketones, as well as 1-hydroxybenzecyclanes to benzocyclanones- 1, without any further fluorination or oxidation under the reaction conditions. On the other hand, reactions of primary alcohols with CsSO₄F resulted in the formation of acid fluorides derived from further fluorination of aldehydes. Another type of transformation was observed in the case of alcohols bearing a benzyl functional group attached geminal to a hydroxy group, where decarbanylation of reactive intermediates resulting in the formation of benzyl fluoride derivatives became the main process. 2- Phenylethanol was so converted to benzyl fluoride and phenylacetyl fluoride in a 3:1 relative ratio, while 2-phenyl-1-propanol was selectively transformed to 1-phenyl-1-fluoroethane. The presence of the radical inhibitor nitrobenzene in the reaction mixture considerably inhibited conversion of the starting material. The same effect was observed by lowering the solvent polarity. Hammett correlation analysis of the effect of substituents on the reaction rates of oxidation of a set of substituted 1-phenyl-1-ethanols to acetophenones gave the reaction constant p⁺ = -0.32, while analysis of analogous data for the transformations of benzyl alcohols to benzoyl fluorides gave the value of -0.54. A mechanism including radical intermediates was proposed for the transformation of alcohols by CsSO₄F.

Full text of DOI:10.1021/jo962424a

4
916
J . Org. Chem. 1997, 62, 4916-4920
Articles
Rea ction s of Alcoh ols w ith Cesiu m F lu or oxysu lfa te
Stojan Stavber,* Iztok Ko sˇ ir, and Marko Zupan
Laboratory for Organic and Bioorganic Chemistry, “J o zˇ ef Stefan” Institute and Department of Chemistry,
University of Ljubljana, J amova 39, 1000 Ljubljana, Slovenia
Received December 30, 1996X
4
The reactions of alcohols with cesium fluoroxysulfate (CsSO F) in MeCN suspension were studied,
and the role of the structure of the alcohol and the reaction conditions on the course of reaction
was determined. Secondary benzyl alcohols bearing a nonactivating aromatic ring were selectively
4
oxidized to the corresponding ketones, while the CsSO F-mediated reaction of phenyl-1-naphth-
ylmethanol resulted in the formation of 1-fluoronaphthalene and benzaldehyde. Cyclic and noncyclic
secondary alcohols were readily converted to ketones, as well as 1-hydroxybenzocyclanes to
benzocyclanones-1, without any further fluorination or oxidation under the reaction conditions.
4
On the other hand, reactions of primary alcohols with CsSO F resulted in the formation of acid
fluorides derived from further fluorination of aldehydes. Another type of transformation was
observed in the case of alcohols bearing a benzyl functional group attached geminal to a hydroxy
group, where decarbonylation of reactive intermediates resulting in the formation of benzyl fluoride
derivatives became the main process. 2-Phenylethanol was so converted to benzyl fluoride and
phenylacetyl fluoride in a 3:1 relative ratio, while 2-phenyl-1-propanol was selectively transformed
to 1-phenyl-1-fluoroethane. The presence of the radical inhibitor nitrobenzene in the reaction
mixture considerably inhibited conversion of the starting material. The same effect was observed
by lowering the solvent polarity. Hammett correlation analysis of the effect of substituents on the
reaction rates of oxidation of a set of substituted 1-phenyl-1-ethanols to acetophenones gave the
+
reaction constant F ) -0.32, while analysis of analogous data for the transformations of benzyl
alcohols to benzoyl fluorides gave the value of -0.54. A mechanism including radical intermediates
was proposed for the transformation of alcohols by CsSO
4
F.
Compounds possessing a fluoroxy moiety attract con-
Sch em e 1
siderable interest among chemists. In spite of their usual
high reactivity and moderate stability, fluoroxy com-
pounds are often applied as useful reagents in organic
synthesis. The chemistry of these compounds, used as
selective fluorination reagents for organic molecules, was
1
reviewed recently. Cesium fluoroxysulfate (CsSO
4
F) is
the most stable and easily handled of them and, when
some safety precautions are taken into account, can be
conveniently used as a benchtop reagent. The organic
4
chemistry of CsSO F has been extensively studied during
4
Since, like all fluoroxy compounds, CsSO F is also a
the last decade, leading to the recognition that its
reactions with organic compounds strongly depend on the
type of organic molecule and the functional groups
present. The following types of reactions were ob-
served: fluorofunctionalization of alkenes or alkynes
through the addition or addition-elimination process,
fluorosubstitution reactions at a saturated, unsaturated,
or benzylic carbon atom and at a nitrogen atom, and
oxidation or oxygenation of particular functional groups
or heteroatoms. It was established that only small
variations concerning the structure of the substrate or
the reaction conditions are sufficient to change the
reaction course drastically and favor one reaction type.1
3
strong oxidant, competition between fluorofunctional-
ization and oxidation of an organic molecule possessing
oxidizable functional groups or heteroatoms can take
place.4 In our continued interest in the organic chem-
,5
istry of CsSO
4
F, we now report a more detailed study of
its reactions with alcohols.
Resu lts a n d Discu ssion
Role of th e Str u ctu r e of th e Alcoh ol on th e
Cou r se of Rea ction . In a typical experiment, described
in the Experimental Section, we treated diphenylmetha-
,2
4
nol (1a ) with a 20% molar excess of CsSO F in acetoni-
trile suspension and isolated benzophenone (2, Scheme
1) in almost quantitative yield, showing that the oxida-
X
Abstract published in Advance ACS Abstracts, J une 1, 1997.
(1) Rozen, S. Chem. Rev. 1996, 96, 1717.
(
2) (a) German, L., Zemskov, S., Eds. New Fluorinating Agents in
Organic Syntheses; Springer-Verlag: Berlin, 1989. (b) Zupan, M.;
Stavber, S. The Role of Reagent Structure in the Mild Introduction of
(3) Steele, W. V.; O’Hare, P. A. G.; Appelman, E. H. Inorg. Chem.
1981, 20, 1022.
a
Fluorine Atom into Organic Molecules. In Trends in Organic
(4) Stavber, S.; Zupan, M. Tetrahedron 1992, 48, 5875.
(5) Stavber, S.; Ko sˇ ir, I.; Zupan, M. J . Chem. Soc., Chem. Commun.
1992, 275.
Chemistry; Council of Scientific Information: Trivandrum, India, 1995;
Vol. V, pp 11-36.
S0022-3263(96)02424-3 CCC: $14.00 © 1997 American Chemical Society

Reactions of Alcohols with Cesium Fluoroxysulfate
J . Org. Chem., Vol. 62, No. 15, 1997 4917
Sch em e 2
Sch em e 4
found to be stable under the reaction conditions. No
further fluorination to R-fluoro ketones, as observed with
some N-F fluorinating reagents under similar reaction
6
conditions, nor the Baeyer-Villiger type of oxidation,
expected with reagents possessing similar oxidizing
7
power, took place. Hydroxy-substituted benzocyclanes
Sch em e 3
17 were also selectively transformed to the corresponding
benzocyclanones 18 and 1-phenyl-2-butanol (19a ) to
1
-phenyl-2-butanone (20a ). No fluorofunctionalization of
the benzylic carbon atom was observed in these cases,
in spite of the fact that under the same reaction condi-
tions benzocyclanes or alkyl-substituted aromatics could
be effectively fluorinated at the benzylic position by
1
,2b,8
CsSO
4
F.
2-Octanol (19b) was also quantitatively
transformed to 2-octanone (20b), which was again stable
under the reaction conditions.
On the other hand, intermediate products derived from
4
CsSO F-mediated reactions with primary alcohols re-
acted further, and acid fluorides were isolated as the final
result of the reactions, as shown in Scheme 4. Primary
benzyl alcohols bearing a nonactivated benzene ring
(21a -f) were transformed to the corresponding benzoyl
fluorides (22), while strong donating substituents on the
para position again favored the fluorodealkylation pro-
cess. The primary formed aldehyde could be isolated only
4
at short reaction times or a low CsSO F/alcohol molar
ratio. Thirty-five percent of benzaldehyde was detected
in the crude reaction mixture after 10 min reaction of
tion of the benzylic hydroxy group is the exclusive process
in this case. A different course of reaction was observed
when phenyl(1-naphthyl)methanol (1b) reacted with
benzyl alcohol (21c) with an equimolar amount of CsSO
while the relative ratio of aldehyde rose to 85% when a
-fold excess of starting alcohol was used. After the
4
F,
4
CsSO F under the same reaction conditions, and the
2
fluorodealkylation process, resulting in 1-fluoronaphtha-
lene (3) and benzaldehyde (4) as the reaction products,
was found to be dominant in this case. We further
studied the effect of substituents on the benzene ring in
secondary benzylic alcohols on the course of the reaction
reaction times ordinarily needed for oxidation of second-
ary alcohols with an equimolar or excess amount of
CsSO F only benzoyl fluorides and the starting benzyl
4
alcohols were detected in the reaction mixtures, thus
indicating that the fluorination of aldehydes to acid
4
with CsSO F and found that the reaction is directed
9
fluorides is faster than the oxidation of primary alcohols
toward oxidation of the benzylic hydroxy group if the
benzene ring is substituted with electron-withdrawing
substituents (5a-6c, Scheme 2) and towards fluorodealky-
lation products when strong electron-donating groups are
bonded para to the hydroxybenzyl block. Alkyl- and
cycloalkyl-substituted benzyl alcohols (7, 8) were also
readily transformed to the corresponding ketones, while
R-(trifluoromethyl)benzyl alcohol (9) was found to be
to aldehydes.
Furthermore, we established the role of the structure
of a primary alcohol molecule on the reaction course.
Alkyl-substituted primary alcohols (23, 24, Scheme 5)
were selectively converted to acid fluorides (27, 28) in
high yield, while a benzylic functional group attached
geminal to the hydroxy interfered in the reaction path-
way, causing the decarbonylation of reactive intermedi-
4
much more stable toward CsSO F under the mentioned
reaction conditions and converted to the ketone 14 in less
than 50% yield.
Cyclic alcohols (15, Scheme 3) were also readily
(
(
6) Stavber, S.; Zupan, M. Tetrahedron Lett. 1996, 37, 3591.
7) Hudlick y´ , M. Oxidations in Organic Chemistry; ACS Monographs
1
86; American Chemical Society: Washington, DC, 1990.
(
(
8) Stavber, S.; Zupan, M. J . Org. Chem. 1991, 56, 7347.
9) Stavber, S.; Planin sˇ ek, Z.; Zupan, M. J . Org. Chem. 1992, 57,
converted to the corresponding ketones 16 with CsSO
4
F
in MeCN medium. The resulting carbonyl products were
5334.

4
918 J . Org. Chem., Vol. 62, No. 15, 1997
Stavber et al.
9
Sch em e 5
for the reactions of CsSO
4
F with aldehydes in the case
of secondary alcohols, while in the case of benzyl alcohol
and 2-phenyl-1-propanol the inhibition is twice as strong
4
as for the reactions of CsSO F with the corresponding
aldehydes.9 The conversion of these primary alcohols to
acid fluorides or benzyl fluorides, respectively, are also
much more influenced by the solvent than the transfor-
9
mation of the analogous aldehydes to the same products,
as is evident from the data in Table 1. Less than 25% of
CH Cl in the solvent mixture stopped the reaction in
2 2
the case of 21a ,c, and 15% was sufficient to obtain the
same effect in the case of 26.
Ta ble 1. Effect of th e Rea ction Con d ition s on th e
Tr a n sfor m a tion of Acoh ols w ith CsSO4F a
Effect of th e Str u ctu r e of th e Alcoh ol on Rea ction
Ra tes. Applying the competitive technique for determi-
nation of relative reactivities expressed by relative rate
b
substrate
C6H5CH(Me)OH, 5b
solvent
yield (%)
1
0
MeCN
95; 10b
factors (krel), we established that benzyl alcohols are
more reactive than alkyl-substituted derivatives. 1-Phe-
nylethanol was found to be twice as reactive as 2-octanol
MeCN/0.1 mmol PhNO2 80
MeCN/1 mmol PhNO2
CH2Cl2
m-CF3C6H4CH(Me)OH, 5d MeCN
55
traces
93; 10d
(krel ) 1.8) and benzyl alcohol to the same degree more
reactive than decanol (krel ) 1.7) or 2-phenyl-1-propanol
(krel ) 2.1). This observation is in contrast to that found
for the relative reactivities of the corresponding alde-
MeCN/0.1 mmol PhNO2 86
MeCN/1 mmol PhNO2
MeCN
59
98; 22a
p-MeC6H4CH2OH, 21a
MeCN/0.1 mmol PhNO2 42
4
hydes in their reactions with CsSO F, where the reactiv-
MeCN/1 mmol PhNO2
MeCN/CH2Cl2 9:1
MeCN/CH2Cl2 4:1
MeCN/CH2Cl2 3:1
MeCN
18
69
54
traces
98; 22c
ity decreased in the order alkyl > aryl > benzyl substi-
tuted aldehyde.9 Correlation analysis using Hammett’s
relations between reaction rates and substituent param-
eters afforded values of the reaction constant for the
oxidation of a set of secondary (5) and primary (21) benzyl
C6H5CH2OH, 21c
MeCN/0.1 mmol PhNO2 65
MeCN/1 mmol PhNO2
MeCN/CH2Cl2 9:1
MeCN/CH2Cl2 4:1
MeCN/CH2Cl2 3:1
n-C6H14
26
79
53
0
4
alcohols with CsSO F. The Hammett correlation plot for
the transformation of 1-phenylethanols (5a -g) to ac-
etophenones, presented in Scheme 2, showed a satisfac-
0
+
tory correlation of relative rate factors with σ substit-
C6H5CH(Me)CH2OH, 26
MeCN
91; 31
30
traces
48
39
traces
+
uent constants and gave a straight line with slope F )
MeCN/0.1 PhNO2
MeCN/1 mmol PhNO2
MeCN/CH2Cl2 9:1
MeCN/CH2Cl2 8:1
MeCN/CH2Cl2 6:1
-
0.32 and a correlation coefficient of 0.97, while the
analysis of analogous data for a set of benzyl alcohols
(21a -f, Scheme 4) gave the value of -0.54 for the reaction
constant and a correlation coefficient of 0.99. The reac-
+
a
tion constant F for the oxidation of 5 to 10 has the same
sign but lower magnitude than those reported for the
Standard reaction conditions: 1 mmol of substrate in 2 mL of
solvent; inert atmosphere; 2.4 mmol (in the case of 5b and 5d 1.2
b
1
11
mmol) of CsSO4F; T ) 35 °C; 1 h. Measured from H (10a , 10d )
same reaction using dimethyldioxirane (F ) -1.57),
1
9
or F NMR spectra (22a , 22c, 31) of crude reaction mixtures using
anisole or octafluoronaphthalene as internal standard; calculated
on starting material.
12
chromic acid (F ) -1.16), or chromium trioxide in acetic
acid solvent (F ) -1.01)13 as oxidants and comparable to
those for oxidation by chromium trioxide under basic (F
1
3
ates and resulting in the formation of benzyl fluoride
derivatives (30, 31). 2-Phenylethanol (25) was thus
converted to benzyl fluoride (30) and phenylacetyl fluo-
ride in a 3:1 relative ratio, while 2-phenyl-1-propanol (26)
was selectively transformed to 1-phenyl-1-fluoroethane
31) and carbon monoxide, as detected by MS analysis
of the evolved gas.
Effect of Ra d ica l Sca ven ger a n d Solven t. The
important role of the solvent and the presence of various
radical scavengers in the reactions of CsSO F with
4
) -0.52) or neutral (F ) -0.37) conditions or by
2
-
II
14
+
S O8 -Cu ( F ) -0.27). On the other hand, F for
2
the CsSO F-mediated conversion of 21 to 22 is consider-
4
ably lower than those for the oxidation of benzyl alcohols
1
5
to benzaldehydes by HNO (F ) -2.25) or HNO (F )
3
2
-1.70, Yukawa-Tsuno method)16 and comparable to
those found for conversion of benzaldehydes to benzoyl
(
+
9
fluorides (F ) -0.38) by CsSO F.
4
P r op osed Mech a n ism . On the basis of the presented
experimental results, the possible reaction pathways of
transformation of secondary alcohols to ketones and
primary alcohols to acid fluorides by CsSO F are shown
4
in Scheme 6. The electron-transfer process (A), resulting
different types of organic molecules, pointed out in
several previous reports1 , was also established in the
,2b
4
reactions of CsSO F with alcohols. Nitrobenzene, often
used as a radical inhibitor, when added to the reaction
mixture while keeping the other reaction parameters
constant, reduced the conversion of 1-phenylethanol (5b)
in the formation of cation radical intermediate 32,
(
(
10) Pearson, R. E.; Martin, J . J . Am. Chem. Soc. 1963, 85, 3142.
11) Kova e` , F.; Baumstark, A. L. Tetrahedron Lett. 1994, 35, 8751.
3
and its m-CF analogue (5d ) to the corresponding ac-
etophenone by up to 37% (Table 1). The transformation
of benzyl alcohol (21c) or its p-Me derivative (21a ) was
suppressed by more than 80%, while the reaction of
(12) Lee, D. G.; Downey, W. L.; Maass, R. M. Can. J . Chem. 1968,
6, 441.
4
(
(
13) Kwart, H.; Francis, P. J . Am. Chem. Soc. 1955, 77, 4907.
14) Walling, C.; El-Taliawi, G. M.; Zhao, C. J . Org. Chem. 1983,
2
-phenyl-1-propanol (26) was completely inhibited by the
48, 4914.
(15) Ogata, Y.; Sawaki, Y.; Matsunaga, F.; Tezuka, H. Tetrahedron,
presence of an equimolar amount of nitrobenzene. The
degree of inhibition of the reaction caused by the presence
of a radical scavenger is comparable to those determined
1
966, 22, 2655.
(16) Moodie, R. B.; Richards, S. N. J . Chem., Soc. Perkin Trans. 2
1986, 1833.

Reactions of Alcohols with Cesium Fluoroxysulfate
J . Org. Chem., Vol. 62, No. 15, 1997 4919
Sch em e 6
Ta ble 2. Yield s of Isola ted P r od u cts in th e Rea ction s of
Alcoh ols w ith CsSO4F
isolation
product
method
yield(%)
benzophenone, 2
CC
TLC
CC
CC
CC
CC
CC
CC
CC
CC
CC
CC
CC
92
48
93
90
89
89
88
85
83
88
87
82
91
94
44
59
62
64
85
86
87
87
76
49
76
78
46
74
50
50
10
32
78
1
3
-fluoronaphthalene, 3
′-methylacetophenone, 10a
acetophenone, 10b
4
3
3
4
4
3
3
4
′-bromoacetophenone, 10c
′-bromoacetophenone, 10d
′-(trifluoromethyl)acetophenone, 10e
′-(trifluoromethyl)acetophenone, 10f
′-nitroacetophenone, 10g
′-chlorobenzophenone, 11a
′-(trifluoromethyl)benzophenone, 11b
′-nitrobenzophenone, 11c
propiophenone, 12
cyclopropylphenyl ketone, 13
R,R,R-trifluoroacetophenone, 14
cyclopentanone, 16a
cyclohexanone, 16b
cycloheptanone, 16c
CC
TLC
GLC
GLC
GLC
CC
CC
CC
CC
1
1
1
2
4
4
-indanone, 18a
-tetralone, 18b
-phenyl-2-butanone, 20a
-octanone, 20b
′-methylbenzoyl fluoride, 22a
9
TLC
GLC
CC
9
′-fluorobenzoyl fluoride, 22b
benzoyl fluoride, 22c
9
4
4
3
′-chlorobenzoyl fluoride, 22d
′-(trifluoromethyl)benzoyl fluoride, 22e
′-nitrobenzoyl fluoride, 22f
TLC
GLC
TLC
GLC
GLC
GLC
GLC
TLC
9
9
9
octanoyl fluoride, 27
decanoyl fluoride, 28
phenylacetyl fluoride, 29
benzyl fluoride, 30
9
9
9
1
-fluoro-1-phenylethane, 31
3
3b, which after hydrogen radical abstraction is then
transformed to the final carbonyl product. Both inter-
mediates 33a ,b were postulated and proved during
1
4,17a,20
peroxydisulfate-mediated oxidation of alcohols,
and
followed by proton loss thus forming radical intermediate
it was suggested that the initially-formed alkoxy radical
rapidly interconverts to the thermodynamically more
stable carbon radical. It is interesting that according to
our results disproportionation of cation-radical 32 or
radical 33, regularly observed during peroxydisulfate
oxidation of similar substrates, did not occur after
3
3, which could also be obtained by direct hydrogen
radical abstraction from the alcohol molecule (B), are two
possible reaction pathways. In both cases, the processes
-
•-
can be mediated by SO
4
F
(path A1) or SO
4
(path A2).
The electron-transfer process is generally accepted as the
key reaction channel in the oxidation of organic molecules
by peroxydisulfate where similar reactive species are
4
CsSO F-mediated oxidation. In this case, proton loss
from 32 and hydrogen abstraction from 33 are probably
involved, and in most cases the same reaction products
considerably faster processes than disproportionation of
are formed1
4,17
as in the present report. Since the
14,20b
the same intermediates.
In the case of secondary
fluoroxysulfate anion is an even stronger oxidant than
peroxydisulfate18 and the ionization potentials of alcohols
are between 9 and 10.5 eV, the electron-transfer pathway
is the most probable process in these reactions, but direct
alcohols, oxidation reactions stopped at the ketone for-
mation step, while aldehydes, originally formed from
primary alcohols, reacted further following the mecha-
9
nism already proposed in our previous report, thus
hydrogen abstraction, suggested in some other oxidation
resulting in acid fluorides or benzyl fluorides.
Definitive conclusions concerning the reaction pathway
reactions,1
1,19
could not be neglected. The electron defi-
ciency in cation-radical intermediate 32 in the case of
alkyl-substituted alcohols is located at the oxygen atom,
while in the case of benzyl alcohols 32 is additionally
stabilized due to resonance over the benzene ring.19
Proton loss, as the next step, can proceed from the
hydroxy group, thus forming alkoxy radical 33a , or from
the R-hydroxy carbon atom thus forming carbon radical
4
of oxidation of alcohols with CsSO F cannot be given, but
regarding the strong effect of the radical inhibitor on the
reaction course and the magnitude of the reaction
+
constant (F ), comparable to values obtained for many
radical transformations of alcohols, the main intermedi-
ates involved in these reactions must be of a radical
nature.
(
17) (a) Minischi, F.; Citterio, A.; Giordano, C. Acc. Chem. Res. 1983,
Exp er im en ta l Section
1
4
6, 27. (b) Walling, C.; Zhao, C.; El-Taliawi, G. M. J . Org. Chem. 1983,
8, 4910. (c) Walling, C.; El-Taliawi, G. M.; Amarnath, K. J . Am. Chem.
Soc. 1984, 106, 7573.
1H and 19F NMR spectra were recorded at 60 and 56.4 MHz,
respectively. Alcohols from commercial sources were used.
-
H- couple has a standard electrode potential of
and OF are the strongest oxidants among
(
18) The SO
4
F /SO
.52 V , and after F , XeF
reagents used in organic synthesis, while the S
4
3
2
2
2
2
2
-
2-
2
O
8
/2SO
4
couple has
(20) (a) Ledwith, A.; Russell, P. J .; Sutcliff, L. H. J . Chem. Soc.,
Perkin Trans. 2 1973, 630. (b) Caronna, T.; Citterio, A.; Grossi, L.;
Minischi, F.; Ogawa, K. Tetrahedron 1976, 32, 2741.
1
7a
a standard electrode potential of 2.01 V.
19) Snook, M. E.; Hamilton, G. A. J . Am. Chem. Soc. 1974, 96, 860.
(

4
920 J . Org. Chem., Vol. 62, No. 15, 1997
Stavber et al.
CsSO
Cs SO
Rea ction s of Alcoh ols w ith CsSO
d u r e. A solution of 2 mmol of alcohol in 4 mL of freshly
distilled and dry MeCN was degassed with argon. Then, 600
mg (2.4 mmol), or 1150 mg (4.6 mmol) in the case of primary
4
F was prepared by the reaction of water solution of
with F
and handled according to the literature.21
F . Gen er a l P r oce-
Th e Effect of Solven t on th e Tr a n sfor m a tion of Alco-
h ols. To a solution of 1 mmol of alcohol in 2 mL of solvent
2
4
2
4
(CH
and CH
mmol) or 575 (2.3 mmol) of CsSO
2
Cl
2
or n-hexane), or a solvent mixture consisting of MeCN
Cl , degassed with argon, was added 300 mg (1.2
F, and the reaction suspen-
2
2
4
sion was stirred under Ar at 35 °C for 2 h. The crude reaction
mixtures were isolated and analyzed as cited in the General
Procedure. The effect of the solvent on the course of reaction
is presented in Table 1.
alcohols, of CsSO
sion was stirred under Ar at 30-35 °C for 1 h. After dilution
with 60 mL of CH Cl , the insoluble residue was filtered off,
and the filtrate washed with saturated aqueous NaHCO (30
mL) and water (30 mL), dried (Na SO ), and evaporated under
reduced pressure. The crude reaction mixtures were analyzed
4
F was introduced, and the reaction suspen-
2
2
3
Th e Effect of Ra d ica l In h ibitor on th e Tr a n sfor m a tion
of Alcoh ols. In a degassed solution of 1 mmol of alcohol in
2
4
MeCN was introduced a corresponding amount of PhNO
CsSO F (1.2 or 2.3 mmol) and the reaction suspension stirred
2
and
1
19
by GLC and H and F NMR spectroscopy. The amounts of
4
1
19
the products formed were determined from H or F NMR
spectra of the crude reaction mixtures using anisole or
octafluoronaphthalene as internal standards and yields cal-
culated on starting material. Products were isolated by
at 35 °C under argon for 1 h. The crude reaction mixture was
isolated and analyzed as cited and the effect on the transfor-
mation to carbonyl products presented in Table 1.
Deter m in a tion of Rela tive Ra te F a ctor s. The procedure
column chromatography (SiO
TLC (SiO , n-hexane/CH Cl
2
, n-hexane) or by preparative
4:1) or GLC (OV 101 10%,
already described in the literature was used.4
,9
2
2
2
Chromosorb W A/W 80/100) and identified on the basis of the
spectroscopic data and comparison with authentic samples or
literature data. The yields collected in Table 2 refer to isolated
pure products.
Ack n ow led gm en t. The financial support of the
Ministry of Science and Technology of the Republic of
Slovenia is gratefully acknowledged.
(21) Appelman, E. H. Inorg. Synth. 1986, 24, 22.
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