Double- and triple-consecutive O-insertion into tert-butyl and triarylmethyl structures

Article abstract of DOI:10.1021/ol049171p

(Matrix Presented) The concecutive Criegee rearrangement reactions were studied for tert-butyl trifluoroacetate, triarylcarbinols, and benzophenone ketales with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFA). The formation of methyl acetate and methyl trifluoroacetate indicates that the consecutive double-O-insertion process has taken place for tert-butyl trifluoroacetate. The intermediate dimethoxymethylcarbonium ion was detected below 5°C. A consecutive triple-O-insertion process has been observed for triarylmethanols and benzophenone ketals. A new high yield method of corresponding diaryl carbonates synthesis was developed.

Full text of DOI:10.1021/ol049171p

ORGANIC
LETTERS
2
004
Vol. 6, No. 15
539-2542
Double- and Triple-Consecutive
O-Insertion into tert-Butyl and
Triarylmethyl Structures
2
,†
†
‡
‡
Pavel A. Krasutsky,* Igor V. Kolomitsyn, Sergiy G. Krasutsky, and Paul Kiprof
Natural Resources Research Institute, 5013 Miller Trunk Highway,
Duluth, Minnesota 55811-1442, and Department of Chemistry,
UniVersity of Minnesota, 10 UniVersity DriVe, Duluth, Minnesota 55812
pkrasuts@d.umn.edu
Received May 6, 2004
ABSTRACT
The concecutive Criegee rearrangement reactions were studied for tert-butyl trifluoroacetate, triarylcarbinols, and benzophenone ketales with
trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFA). The formation of methyl acetate and methyl trifluoroacetate indicates that the
consecutive double-O-insertion process has taken place for tert-butyl trifluoroacetate. The intermediate dimethoxymethylcarbonium ion was
detected below 5 °C. A consecutive triple-O-insertion process has been observed for triarylmethanols and benzophenone ketals. A new high
yield method of corresponding diaryl carbonates synthesis was developed.
1
Criegee postulated the formation of intermediate peroxyes-
2
ters in Baeyer-Villiger reaction based on the discovery of
Scheme 1
3
the ionic decomposition of 9-acylperoxydecalin. The Criegee
rearrangement, in contrast to the Baeyer-Villiger reaction,
can occur with consecutive O-insertions (Scheme 1). More-
over, consecutive O-insertions have never been reported for
aldehydes or ketones,6 therefore, the Criegee and Baeyer-
Villiger process are rather different from a synthetic point
of view.
1,3
4,5
-8
†
Natural Resources Research Institute.
University of Minnesota.
‡
1) Criegee, R. Justus Liebigs Ann. 1948, 560, 127.
V. Ber. 1890, 33, 8585.
(
3) Criegee, R. Chem. Ber. 1944, 77, 722.
(4) (a) Krasutsky, P. A.; Baula, O. P.; Yurchenko, A. G. Russ. J. Org.
Chem. 1994, 30, 370. (b) Krasutsky, P. A.; Baula, O. P.; Botov, E. M.
Russ. J. Org. Chem. 1996, 32, 1225. (c) Krasutsky, P. A.; Kolomitsyn, I.
V.; Kiprof, P.; Carlson, R. M.; Fokin, A. A. J. Org. Chem. 2000, 65, 3926.
(
d) Krasutsky, P. A.; Kolomitsyn, I. V.; Kiprof, P.; Carlson, R. M.;
Sydorenko, N. A.; Fokin, A. A. J. Org. Chem. 2001, 66, 1701.
5) (a) Bailey, W. F.; Shih, M.-J. J. Am. Chem. Soc. 1982, 104, 1769.
b) Bailey, W. F.; Bischoff, J. J. J. Org. Chem. 1985, 50, 3009.
6) Hassal, C. H. Org. React. 1957, 9, 73. Plesnicar, B. In Organic
Chemistry, Part C; Trahanovsky, W. S., Ed.; Academic Press: New York,
978; p 254. Krow, G. R. Tetrahedron 1981, 37, 2697.
The hypothetic triple-O-insertion pathway of the consecu-
tive Criegee rearrangement is shown in Scheme 1. Stable
(
(
(
(7) Renz, M.; Meunier, B. Eur. J. Org. Chem. 1999, 737.
(8) Krow, R. G. Org. React. 1993, 43, 251.
1
1
0.1021/ol049171p CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/29/2004

1
products of every O-insertion step (A-C) are easily recog-
nized. The formation of B could be the mistaken as
proceeding from A through the Baeyer-Villiger reaction.
However, the possibility of distinguishing the Baeyer-
Villiger reaction of ketone A to ester B from the consecutive
Criegee rearrangement by kinetic consideration has been
shown in our previous research.4d
A solution of TFPAA in TFA has been found to be a very
favorable system for consecutive O-insertions into cage
structures.4
dimethoxyethyl cation (6) was detected (Scheme 2) by H
1
3
and C NMR at -25 °C (total conversion of perester 2 was
35%). The spectrum of cation 6 is identical to a previously
1
1,17
reported one.
Methyl acetate (7), methyl trifluoroacetate
(8), and traces of acetone were also present in the reaction
mixture. Formation of traces of acetone can be explained
by the relatively low stability of ester 3 that decomposes to
acetone and trifluoroacetate 8. Further stirring at 5 °C results
in the increase of acetate 7 and trifluoroacetate 8 and decrease
of trifluoroperacetate 2. Therefore, acetate 7 and trifluoro-
acetate 8 are evidently the product of the double-O-insertion
and the subsequent decomposition of the intermediate ortho
ester 5 in TFA. At room temperature, the final products 7
and 8 were formed in 4 h. Cation 6 does not perform a third
O-insertion. When perester 2 was generated from tert-
butyl hydroperoxide (9) and trifluoroacetic anhydride (TFAA),
methyl trifluoroacetate (8) and acetone (10) were formed in
equivalent amounts at rt in TFA as the only products of
mono-O-insertion in the Criegee rearrangement process
Further generalization of this approach to acyclic and arylic
structures is the main goal of this study. The specific desire
to find structures susceptible to the triple O-insertion also
motivated this work. The synthetic peculiarity of the solution
of TFPAA in TFA allow the selective double-O-insertions
1
5b
4
in the consecutive Criegee rearrangements. This became
understandable when a stable dioxacarbonium ion was
observed in the reactions of 2-methyladamantane-2-ol with
4c
the TFPAA in TFA. It was demonstrated earlier that relative
stabilities decrease when a methyl group is replaced by a
phenyl group in methyl- and phenyl-substituted delocalized
1
8
(Scheme 3). The comparatively lower acidity of TFA,
9
carbocations. Moreover, the dimethoxymethylcarbonium ion
1
0
11
is stable, and can be generated in TFA. At the same time,
the aryl group has better migratory aptitude than the methyl
Scheme 3
7
,12
group in the Baeyer-Villiger reaction and Criegee rear-
1
3
rangement. These observations prompted our research on
tert-butyl trifluoroacetate (1), triarylmethanols 11-14, and
benzophenone ketals 19 and 25.
The consecutive Criegee rearrangement1 of tert-butyl
trifluoroacetate (1) with 10-fold excess of TFPAA in TFA
at -15 °C was not observed, in contrast to consecutive
Criegee rearrangement of cage compounds,3c,d within 10 h.
The only formation of corresponding tert-butyl trifluoro-
4
compared to superacids, does not stabilize the intermediate
carboxonium ion, but its acidity is enough to catalyze
Criegee rearrangements.
The reaction of triarylmethanols 11-14 with 10-fold
excess of TFPAA in TFA, in contrast to tert-butyl trifluo-
1
9
1
5
1
peracetate (2) was detected at -15 °C in situ by H
NMR and C NMR (Scheme 2). This method can be
1
3
(12) Strucul, G. Angew. Chem., Int. Ed. 1998, 37, 1198.
(
13) (a) Goodman, R. M.; Kishi, Y. J. Am. Chem. Soc. 1998, 120, 9392.
b) Sheldon, R. A.; van Doorn, J. A. Tetrahedron Lett. 1973, 13, 1021.
14) Reaction of tert-Butyl Trifluoroacetate with TFPAA. A solution
(
(
of tert-butyl trifluoroacetate (1) (0.1 g, 0.6 mmol) in TFA (1 mL) was added
to a solution of TFPAA in TFA (1.73 g, 6 mmol of TFPAA) at -15 °C.
Scheme 2
(
a) The temperature was allowed to rise to 5 °C. After the solution was
o
stirred for 2 h at 5 C the formation in situ of 1,1-dimethoxyethyl cation
1
13
(
6) was detected by H and C NMR analysis at -25 °C. The observed
level of tert-butyl trifluoroperacetate (2) conversion was 35%. (b) The
temperature was allowed to rise room temperature, and after the solution
was stirred for 4 h at room temperature the formation in situ of methyl
1
acetate (7) and methyl trifluoroacetate (8) was detected by H NMR analysis.
Ratio of products was 7/8 ) 1:1.
(15) tert-Butyl Trifluoroperacetate (2). (a) A solution of tert-butyl
trifluoroacetate (1) (0.1 g, 0.6 mmol) in TFA (1 mL) was added to a solution
of TFPAA in TFA (1.73 g, 6 mmol of TFPAA) at -15 °C. After 1 h, the
formation of tert-butyl trifluoroperacetate (2) in situ was observed by NMR
1
analysis at -15 °C. TMS in CD3COCD3 was used as external standard. H
NMR (CF3COOH, 300 MHz): δ. 0.927. 13C NMR (CF3COOH, 75
2
1
MHz): δ 149.9 (q, JCF ) 48.1 Hz), 113.5 (q, JCF ) 283.2 Hz), 88.3,
2
2
6.4. (b) Modified literature procedure:16 trifluoroacetic anhydride (0.47 g,
.2 mmol) was added to tert-butyl hydroperoxide (0.1 g, 1.1 mmol) at -15
C. The formation of tert-butyl trifluoroperacetate in situ was observed by
considered as a new and simple method of synthesizing
trifluoroperacetate 2.16
When the temperature was allowed to rise to 5 °C, and
after 2 h of stirring, the formation of the intermediate 1,1-
°
NMR analysis after 30 min at -15 °C.
(16) Bartlett, P. D.; Hiatt, R. R. J. Am. Chem. Soc. 1958, 80, 1398.
(
17) Olah, G. A.; Hartz, N.; Rasul, G.; Burrichter, A.; Prakash, G. K. S.
J. Am. Chem. Soc.1995, 117, 6421.
18) Criegee Rearrangement of tert-Butyl Trifluoroperacetate (2).
(
(
9) Larsen, J. W.; Bouis, P. A.; Riddle, C. A. J. Org. Chem. 1980, 45,
TFA (3 mL) was added to a solution of tert-butyl trifluoroperacetate (2) in
TFAA (0.6 g, 1.16 mmol of peroxide 2) at -15 °C. The formation in situ
4
969.
1
(
10) (a) Taft, R. H.; Martin, R. H.; Lampe, F. W. J. Am. Chem. Soc.
of acetone (10) and methyl trifluoroacetate (8) was detected by H NMR
1
965, 87, 2490. (b) Martin, R. H.; Lampe, F. W.; Taft, R. W. J. Am. Chem.
analysis. Ratio of products was 10/8 ) 1:1.
Soc. 1966, 88, 1353.
11) Ramsey, B. G.; Taft, R. W. J. Am. Chem. Soc. 1966, 88, 3058.
(19) Olah, G. A.; Parker, D. G.; Yoneda, N. J. Org. Chem. 1977, 42,
(
32.
2540
Org. Lett., Vol. 6, No. 15, 2004

roacetate (1), occurs at -25 °C yielding triple-O-insertion
20a
products 15-18 (Scheme 4). Diphenyl carbonate (15), di-
Scheme 5
Scheme 4
2
6
yield (Scheme 5). The formation of diphenylethoxycarbe-
2
7
1
13
nium ion (20) was detected at -15 °C by H and C NMR
1
in situ when ketal 19 was dissolved in TFA. The H NMR
spectral data of cation 20 are identical to the data previously
reported. The quantitative formation of carbonate 24
2
1
28
(
p-methylphenyl) carbonate (16), di(p-chlorophenyl) car-
22
23
bonate (17), and di(p-methoxyphenyl) carbonate (18) were
obtained with high yields (90-96%). Only traces (<1%) of
double-O-insertion products and traces (<1%) of mono-O-
insertion products were detected by GC/MS analysis of the
reaction mixtures. All spectral data of the products 15-18
were identical to the corresponding literature values. The
NMR monitoring of reaction at -25 °C did not reveal any
signs of intermediate carboxonium ions. However, ben-
zophenone was converted quantitatively to phenyl benzoate
at the described oxidation conditions. Moreover, phenyl
benzoate was stable for 10 h in a solution of TFPAA in TFA
at room temperature. This result supports the assumption that
carbonates 15-18 are products of triple-O-insertions of
alcohols 11-14 as well as clearly demonstrating that
consecutive O-insertions are not possible for Baeyer-Villiger
reaction under these conditions.
occurred when 10-fold excess of TFPAA was added to the
2
6b
solution of carboxonium ions 20 in TFA.
When the
reaction mixture was quenched with water (after 1 h) the
26a
second O-insertion product ester 22 was obtained with 95%
yield. Ester 22 was stable in a solution of TFPAA in TFA
even at room temperature and no traces of carbonate 24 were
found. Consequently, the formation of ester 22 is the result
of the reaction of water with the intermediate cation 21
2
4
29
(double-O-insertion product ) and subsequent decomposition
3
0
of the corresponding orthoester. Cation 21 undergoes
Criegee rearrangement with intermediate formation of ester
23, which decomposes giving carbonate 24sa triple-O-
insertion product.
When benzophenone diphenylketal (25)31-33 was treated20b
with 10-fold excess of TFPAA in TFA at -25 °C and
carbonate 15 (Scheme 6) was observed as the only product
25
Benzophenone diethyl ketal (19) undergoes the consecu-
tive Criegee rearrangement with TFPAA in TFA at -25 °C
with the formation of ethyl phenyl carbonate (24) in 96%
Scheme 6
(
20) Diphenyl Carbonate (15). (a) A solution of triphenylmethanol (11)
(
0.1 g, 0.38 mmol) in dry CF2ClCCl2F (1 mL) was added to a solution of
TFPAA in TFA (1.1 g, 3.8 mmol of TFPAA) at -25 °C and stirred for 1
h. The solution was then quenched with H2O (20 mL) and extracted with
three portions of CH2Cl2 (20 mL), and the organic part was washed with
water and dried over Na2SO4. The solvent was evaporated, and the residue
was purified by flash chromatography on silica gel (ether/hexanes ) 2/3).
Crystallization from ether yielded white crystals of carbonate 15 (0.078 g,
96%). (b) A solution of benzophenone diphenyl ketal (25) (0.1 g, 0.28 mmol)
of a consecutive Criegee rearrangement of ketal 25. In
contrast to ketal 19, ketal 25 decomposed to benzophenone
and phenol under the same reaction conditions (TFA, -15
in dry CFCl3 (0.6 mL) was added dropwise to a solution of TFPAA in
TFA (0.91 g, 2.8 mmol of TFAA) at -25 °C and stirred for 1 h. The solution
was then quenched with H2O (20 mL) and extracted with three portions of
CH2Cl2 (20 mL); the organic part was washed with water and dried over
Na2SO4. The solvent was evaporated and the residue was purified by flash
chromatography on silica gel (ether/hexanes ) 2/3). Crystallization from
ether yielded white crystals of carbonate 15 (0.058 g, 96%).
27
°C) in which cation 20 was generated. This results support
(25) Verevkin, S. P.; Peng, W.-H.; Beckhaus, H.-D.; Ruechardt, C. Eur.
J. Org. Chem. 1998, 2323.
24a
(
21) Di(p-methylphenyl) Carbonate (16). Using the same procedure
as for diphenyl carbonate (15) from tri(p-methylphenyl)methanol (12) (0.1
g, 0.33 mmol), 0.073 g (91%) of di(p-methylphenyl) carbonate (16) was
obtained.
(26) Reaction of Benzophenone Diethyl Ketal (19) with TFPAA. Ketal
19 (0.1 g, 0.4 mmol) was dissolved a solution of TFAA (0.1 mL) in TFA
(1 mL) at -15 °C. The resulting solution was added to a solution of TFPAA
in TFA (1.18 g, 4 mmol of TFPAA) at -25 °C. (a) After 1 h, the reaction
mixture was quenched with H2O (20 mL), extracted with three portions of
CH2Cl2 (20 mL), and dried over Na2SO4. The solvent was evaporated, and
the residue was purified by flash chromatography on silica gel (ether/hexanes
) 2/3) to yield 0.056 g (95%) of ethyl benzoate (22). (b) After 2 h, the
reaction mixture was quenched with H2O (20 mL), extracted with three
portions of CH2Cl2 (20 mL), and dried over Na2SO4. The solvent was
evaporated, and the residue was purified by flash chromatography on silica
gel (ether/hexanes ) 2/3) to yield ethyl phenyl carbonate (24) (0.059 g,
96%).
(
22) Di(4-chlorophenyl) Carbonate (17).24b Using the same procedure
as for diphenyl carbonate (15) from tri(4-chlorophenyl)methanol (13) (0.1
g, 0.28 mmol), 0.07 g (90%) of di(4-chlorophenyl) carbonate (17) was
obtained as colorless crystals.
24a
(
23) Di(4-methoxyphenyl) Carbonate (18). Using the same procedure
as for diphenyl carbonate (15) from tri(4-methoxyphenyl)methanol (14) (0.1
g, 0.29 mmol), 0.073 g (92%) of di(4-methoxyphenyl) carbonate (18) was
obtained as white crystals.
(
24) (a) Lu, X.; Reid, D. L.; Warkentin, J. Can. J. Chem. 2001, 79, 319.
(
b) Lu, X.; Warkentin, J. Can. J. Chem. 2002, 80, 228.
Org. Lett., Vol. 6, No. 15, 2004
2541

9
the observation that the relative stability of carboxonium
difference is that methanol immediately esterifies in TFA at
5 °C.
ions decreases when methyl or ethyl is replaced by phenyl.
Furthermore, the quantitative formation of carbonate 15 from
ketal 25 allows for the assumption that cation 26 is generated
from ketal 25 on the way to carbonate 15 at -25 °C.
Trifluoroacetates 23 and 27 may be considered as the most
feasible intermediates on the way to carbonate 24 and 15
respectively (Scheme 7). The lack of the intermediate
Triarylmethyl as well as diphenylalkoxy and diphenylphe-
noxy structures undergo the consecutive Criegee rearrange-
ment with TFPAA in TFA with the formation of the triple-
O-insertion products. In contrast to triarylmethyl structures,
only a double-O-insertion reaction occurs with tert-butyl
trifluoroacetate under similar conditions. The relative stability
of the intermediate 1,1-dimethoxyethyl cation (6) in TFA
and low migratory aptitude of the methyl group may be the
reason for selective double-O-insertion into the tert-butyl
group. The relative lower stability of aryloxycarbonium ions,
as well as high migratory aptitude of aryl groups, results in
a triple-O-insertion. The triple-O-insertion into triarylmethyl
structures results in a high-yield formation of diaryl carbon-
ates. This new one-step synthesis leads to easy access to
diaryl carbonates and alkyl aryl carbonates.
Scheme 7
Acknowledgment. This work was supported by the
graduate student program of the University of Minnesota,
Duluth, Department of Chemistry. We are grateful to Natural
Resources Research Institute (UMD) for providing help with
spectral equipment.
carboxonium ion at -25 °C in a case of alcohols 11-14
may be explained by their instability and the fast decomposi-
tion of corresponding esters to carbonates 15-18 in TFA
media at -25 °C. This assumption was supported by the
formation of phenol that was observed by GC/MS from
alcohol 11 and ketal 19 when the ratio was 11/TFPAA )
Supporting Information Available: H NMR and 13
NMR spectra of all new structures. This material is available
free of charge via the Internet at http://pubs.acs.org.
C
OL049171P
32
(
31) Benzophenone Diphenyl Ketal (25). Ketal 25 was synthesized
33
1/5 and 19/TFPAA ) 1/4, respectively. A similar reaction
by a modified literature procedure: dichlorodiphenylmethane (3 g, 12.7
mmol) was added to a solution of sodium phenolate (3.67 g, 31.6 mmol) in
chlorobenzene (300 mL) and refluxed overnight. Water (300 mL) was added
to the reaction mixture, which was extracted with three portions of CH2Cl2
(100 mL). The solvent was evaporated under vacuum, and the residue was
purified by flash chromatography on silica gel (ether/hexanes ) 2/3).
Crystallization from ether yielded ketal 25 (4 g, 90%) as white crystals. IR
apparently occurs with intermediate esters 5. The only
(
27) Diphenylethoxycarbenium Ion (20). Benzophenone diethyl ketal
19) (0.1 g, 0.4 mmol) was dissolved in a solution of trifluoroacetyl
anhydride (0.1 mL) in TFA (1 mL) at -15 °C, and the formation of cation
0 was detected in situ by NMR analysis at -15 °C. TMS in CD3COCD3
(
-
1
1
2
(film, cm ): 3026, 1599, 1588, 1491. H NMR (CDCl3, 300 MHz): δ
1 2
1
was used as external standard. H NMR (CF3COOH, 300 MHz): δ 7.46
7.66 (m, 4H), 7.24-7.06 (m, 14H), 6.86 (tt, J ) 6.3 Hz, J ) 2.1 Hz,
13
13
(
m, 4H), 7.17 (m, 6H), 4.66 (q, J ) 6.9 Hz, 2H), 1.16 (t, J ) 6.9, 3H).
NMR (CF3COOH, 75 MHz) APT: δ 204.9(+), 135.5 (+), 134.4 (-), 130.8
-), 128.3 (-), 65.7 (+), 15.1 (-).
28) Olah, G. A.; DeMember, J. R.; Mo, Y. K.; Svoboda, J. J.; Schilling,
P.; Olah, J. A. J. Am. Chem. Soc. 1974, 96, 884.
C
2H). C NMR APT (CDCl3, 75 MHz): δ 154.2 (+), 142.2 (+), 128.9
(-), 128.1 (-), 127.7 (-), 126.7 (-), 122.2 (-), 120.0 (-), 105.2 (+).
MS m/z (rel intensity): 259 (100), 216 (10), 165 (25), 105 (26), 77 (48).
(32) Borkovec, A. B. J. Org. Chem. 1961, 26, 4866.
(
(
(33) Korshak, V. V.; Bulgakova, I. A.; Salazkin, S. N.; Vinogradova, S.
V. Study of the reaction of diphenyldichloromethane with phenol. Inst.
Elementoorg. Soedin., Moscow, USSR 1973.
(
29) Assuming that cation 20 is the mono-O-insertion product.
(30) Deslongchamps, P.; Dory, Y. L.; Li, S. Tetrahedron 2000, 56, 3533.
2542
Org. Lett., Vol. 6, No. 15, 2004