8690
P. A. Krasutsky et al. / Tetrahedron Letters 43 (2002) 8687–8691
1992, 101, 249 (R=cyclopentyl, cycloheptyl, cyclohexyl-
and stirred at room temperature for 20 min. A solution of
TFPAA in TFAA (0.722 g, 2.5 mmol of TFPAA) was
then added dropwise into a well-stirred solution of car-
boxylic acid in freshly distillated TFAAn at −20°C and
stirred for another 20 min. Decarboxylation proceeds
immediately for acids 5–13. The conversion of acids 2–5
and the product distribution were verified by 1H NMR
analysis of the reaction mixture compare to signal of
1,4-di(trifluoromethyl)benzene. The work-up procedure
for the decarboxylation of acids 6–13 included the addi-
tion of CH2Cl2 (12 ml) into the reaction mixture, washing
with H2O (4×2 ml) and a saturated solution of NH4Cl in
water and drying over Na2SO4. Solvent was evaporated
and the residue was purified by column chromatography
using 5% solution of ether in pentane as an eluting
solvent. The yields of products are shown in Table 1.
Propionyltrifluoroacetyl peroxide (14): at 0°C; 1H NMR
(CF3COOH, 300 MHz): l 2.07 (q, J=7.5 Hz, 2H), 0.77
(t, J=7.5 Hz, 3H). 13C NMR (CF3COOH, 75 MHz): l
methylene); (f) Cotarca, L.; Delogu, P.; Nardelli, A.;
Maggioni, P.; Bianchini, R.; Sguassero, S.; Alini, S.;
Dario, R.; Clauti, G.; Pitta, G.; Duse, G.; Goffredi, F.
Org. Process Res. Dev. 2001, 5, 69 (R=cyclohexyl).
4. Perpropionic acid and 2-methylperpropionic acid were pre-
pared by a modified literature procedure3b from propi-
onic acid (3) and 2-methylpropionic acid (4), respectively:
H2O2 (35% solution in water, 110 g) was added dropwise
into a well-stirred solution of carboxylic acid (0.1 mol),
H2O (30 ml), and H2SO4 (35 g, 0.36 mol) at 0°C and
stirred for 1 h. The reaction mixture was then extracted
with CCl2FCF2Cl (12×10 ml). The combined organic
extracts were treated with a buffer solution (pH 8.0) until
all carboxylic acid was removed and then dried over
Na2SO4. Half of the solvent was evaporated at 20°C and
quality of the solution of peracid in CCl2FCF2Cl was
1
confirmed by H NMR and by iodometric titration and
used without further purification.
2
1
5. Trifluoroacetic anhydride (TFAAn) must be a freshly
distilled and stored in a Teflon® bottle. A solution of
TFPAA in TFAA must be prepared from freshly distil-
lated TFAAn and stored in a Teflon® bottle. For more
information, see Ref. 1
171.2, 154.7 (q, JCF=48 Hz), 113.4 (q, JCF=287.8 Hz),
22.5, 7.1. 19F NMR (CF3COOH, 282.2 MHz, relative to
CFCl3): l −73.3. 2-Methylpropionyltrifluoroacetyl perox-
1
ide (15): at −40°C; H NMR (CCl2FCClF2, 300 MHz): l
1.78 (h, J=7.2 Hz, 1H), 0.33 (d, J=7.2 Hz, 6H). 13C
2
6. Preparation of trifluoroacetates 16–28: Trifluoroacetates
were prepared by adding the corresponding alcohol (1
mmol) into trifluoroacetic anhydride (3 ml) at 0°C and
stirring for 0.5 h. The solvent was then evaporated and
trifluroacetates 17–25 were obtained in a quantitative
yield. 1-Adamantylmethyl trifluoroacetate (22): IR (film,
cm−1): 2965–2840, 1778, 1185. 1H NMR (CDCl3, 300
NMR (CCl2FCClF2, 75 MHz): l 162.3, 154.1 (q, JCF
=
48 Hz), 113.1 (q, JCF=287.8 Hz), 33.2, 17.6. 19F NMR
(CCl2FCClF2, 282.2 MHz, relative to CFCl3): l −73.4.
8. A solution of perpropionic acid and 2-methylperpropi-
onic acid CCl2FCF2Cl was used for decarboxylation by
method A.
1
9. (a) Sawada, H. Chem. Rev. 1996, 96, 1779; (b) Sawada,
H. J. Fluorine Chem. 2000, 105, 219.
MHz): l 3.94 (s, 2H), 2.02 (m, 3H), 1.8–1.5 (m, 12H). 13
C
2
NMR (CDCl3, 75 MHz): l 155.8 (q, JCF=41 Hz), 114.5
(q, CF3, 1JCF=285.8 Hz), 77.1, 38.8, 36.7, 33.4, 27.8.
GC/MS m/z (rel. intensity): 262 (1, M+), 149 (7), 135
(100), 107 (23), 93 (29), 79 (34), 69 (30). Anal. calcd for
C13H17F3O2: C, 59.53; H, 6.53. Found: C, 59.49; H, 6.51.
For properties of trifluoroacetates, see: Asadullah, M.;
Kitamura, T.; Fujiwara, Y. J. Catal. 2000, 195, 180
(cyclopentyl-, cyclohexyl-, cycloheptyl-trifluoroacetates).
Begue, J.-P.; Rock, M. H. J. Organomet. Chem. 1995,
489, C7 (cyclohexylmethyl trifluoroacetate); Creary, X.;
Jiang, Z. J. Org. Chem. 1996, 61, 3482 (homoadamant-3-
yl trifluoroacetate); Creary, X.; Jiang, Z. J. Org. Chem.
1994, 59, 5106 (adamant-1-yl trifluoroacetate).
10. Young, D. M.; Thompsom, B. US Patent 2,700,662,
1955. E.I. du Pont de Nemours & Co. Brit. 781,532,
1957. Carlson, D. P. Ger., Offen. 1,806,426, 1969.
11. (a) Ogino, K.; Abe, M.; Morikawa, K.; Mitani, M.;
Sawada, H.; Matsumoto, T. J. Jpn. Soc. Colour Mater.
1992, 65, 205; (b) Sawada, H.; Mitani, M.; Minoshima,
Y.; Nakayama, M. J. Jpn. Res. Institute Mater. Technol.
1994, 12, 185.
12. (a) Linhardt, R. J.; Murr, B. L.; Montgomery, E.; Osby,
J.; Sherbine, J. J. Org. Chem. 1982, 47, 2242; (b) Walling,
C.; Waits, H. P.; Milovanovic, J.; Pappiaonnou, C. G. J.
Am. Chem. Soc. 1970, 92, 4927; (c) Fujimori, K. In
Organic Peroxides; Ando, W., Ed.; John Wiley & Sons,
1992; pp. 318–385.
7. General procedure for decarboxylation:
Method A: A solution of peroxy acid (1 mmol, >92%
purity) in CH2Cl2 (6 ml)8 was added dropwise into well-
stirred trifluoroacetic anhydride (6 g, 28.6 mmol) at
−20°C. In the case of acids 2–5 1,4-di(trifluoro-
methyl)benzene (0.214 g, 1 mmol) was added into tri-
fluoroacetic anhydride as internal standard. Decarboxyla-
tion proceeds immediately for acids 5–13. The conversion
of acids 2–5 and products distribution were verified by 1H
NMR analysis of the reaction mixture compared to the
signal of 1,4-di(trifluoromethyl)benzene. Work-up proce-
dures for the decarboxylation of acids 6–13 included the
evaporation of solvent and the flash chromatography on
silica of the residue. Typically 5% solution of ether in
pentane was used as an eluting solvent. The yields of
products are shown in Table 1.
13. (a) Emmons, W. D.; Pagano, A. S.; Freeman, J. P. J. Am.
Chem. Soc. 1954, 76, 3472; (b) Holbert, G. W.; Ganem,
B. J. Chem. Soc., Chem. Commun. 1978, 248.
14. Krasutsky, P. A.; Semenova, I. G.; Safronova, E. E.;
Novikova, M. I.; Yurchenko, A. G. Zh. Org. Khimii.
1989, 25, 2336.
15. This ratio of trifluoroacetates is expected for nucleophilic
trapping of 3-homoadamantyl cation (94:6 for the reac-
tion with acetate ion): Nordlander, J. E.; Jindal, S. P.;
Schleyer, P. v. R.; Fort, R. C., Jr.; Harper, J. J.;
Nicholas, R. D. J. Am. Chem. Soc. 1966, 89, 4475.
16. Liggero, S. H.; Sustmann, R.; Schleyer, P. v. R. J. Am.
Chem. Soc. 1969, 91, 4571.
17. Krapcho, A. P.; Johanson, R. G. J. Org. Chem. 1971, 36,
146.
Method B: Carboxylic acid (1 mmol) was added into
freshly distilled trifluoroacetic anhydride (1.26 g, 6 mmol)
18. (a) Hashimoto, N.; Aoyama, T.; Shioiri, T. Tetrahedron
Lett. 1980, 21, 4619; (b) Lorenzin, M.; Guerriero, A.;