Z. Yan et al. / Tetrahedron Letters 50 (2009) 2727–2729
2729
O
S
O
C
(1.0 equiv) in CH2Cl2 was stirred for 1 h. Then it was treated with
HCF2CF2OCF2CF2SO2F (1.0 equiv) and stirred at rt for 12 h. Alcohol
(R 0 OH) (2.0–10.0 equiv) was added followed by the addition of
1.5–2.0 equiv of DBU. The resultant mixture continued to stir at
rt for 24 h. The workup procedure is simple and just evaporation
of volatile ingredients and purification of residue through flash col-
umn chromatography were needed.
O
C
CN-
RCOO-
(RCO)2O
R
O
Rf
R
CN
O
A
B
CN-
RCOO-
Scheme 2.
For the amidation of carboxylic acids (RCOOH) with amines
(R’NH2), the procedure is a little bit different from the above one.
After addition of 2.0–10.0 equiv of amine (R 0 NH2) and 1.5–2.0 equiv
of DBU, the reaction should be run in reflux for 24 h. The workup
procedure is the same as described above.
The procedure for anhydridization: At room temperature, a solu-
tion of carboxylic acid (RCOOH) and 1,3-diazabicyclo[5.4.0]-undec-
7-ene (DBU, 1.0 equiv) in CH2Cl2 was stirred for 1 h. Then
HCF2CF2OCF2CF2SO2F (0.5 equiv) and trimethylsilyl cyanide
(0.5 equiv) were added, respectively, and the resultant mixture
continued to stir at rt for 24 h. The workup procedure is the same
as described above.
the fact that the stronger acidity of hydroxyl group in phenol deriv-
atives resulted in the easier formation of phenol anions which is a
strong nucleophile.
For amidation of carboxylic acids with amines, similarly, the
structure of amines has a considerable influence on the reaction.
In the case of linear primary amines (entries 16–20), amides can
be obtained in 68–80% yields. For sterically encumbered branched
substrates (entries 21 and 22), only low yields of desired products
were formed. The result in entry 23 (no desired product formed)
indicates that the secondary amine is not a suitable substrate for
this reaction.
Results from entries 24–27 in Table 1 shows that HCF2CF2OCF2-
CF2SO2F/(CH3)3SiCN system also can efficiently mediate anhydridi-
zation of some aromatic carboxylic acids. In all the cases, only
desired symmetrical anhydrides were formed and the others were
unreacted starting materials carboxylic acids. Unfortunately,
HCF2CF2OCF2CF2SO2F/(CH3)3SiCN system is not applicable to anhy-
dridization of aliphatic carboxylic acids which might be due to the
instability of intermediate B (see Scheme 2) of aliphatic carboxylic
acids. A possible mechanism was put forward to interpret the
anhydridization and is shown in Scheme 2. Intermediate A (mixed
anhydride, see Scheme 1) is first formed and then is attacked by
cyanide anion resulting from the reaction of DBUꢀHF salt with
(CH3)3SiCN to afford acyl cyanide (intermediate B). Cyanide moiety
in acyl cyanide is a very good leaving group and the reaction of acyl
cyanide with carboxylic acid anion smoothly offers a symmetrical
anhydride. The failure of reaction of intermediate A with carbox-
ylic acid anion might be due to the weak nucleophility of RCOOꢁ
References and notes
1. (a) Otera, J. Esterification Methods Reaction and Applications; Wiley-VCH:
Weinheim, 2003; (b) Multzer, J. Comprehensive Organic Functional Group
Transformations. In Carboxylic Esters and Lactones; Moody, C. J., Ed.; Pergamon:
Oxford, 1995; Vol. 6, p 121; (c) Johnes, J. The Chemical Synthesis of Peptides;
Oxford University Press: Oxford, 1991; (d) Bodanszky, M. Principles of Peptide
synthesis; Springer: Berlin, 1984.
2. Multzer, J.. In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.;
Pergamon: Oxford, 1991; Vol. 6, p 323.
3. (a) Brewster, J. H.; Ciotti, C. J. J. Am. Chem. Soc. 1955, 77, 6214–6215; (b)
Chandrasekaran, S.; Tumer, J. V. Synth. Commun. 1982, 12, 727–731; (c) Hassner,
A.; Alexanian, V. Tetrahedron Lett. 1978, 46, 4475–4478; (d) Inanaga, J.; Hirata,
K.; Saeki, H.; Katsuki, T.; Yamaguchi, M. Bull. Chem. Soc. Jpn. 1979, 52, 1989–
1993; (e) Saito, Y.; Yamaki, T.; Kohashi, F.; Watanabe, T.; Ouchi, H.; Takehata, H.
Tetrahedron Lett. 2005, 6, 1277–1279.
4. (a) Ruan, Z.; Lawrence, R. M.; Cooper, C. B. Tetrahedron Lett. 2006, 47, 7649–
7651; (b) Belleau, B.; Malek, G. J. Am. Chem. Soc. 1968, 90, 1651–1652; (c) Kiso,
Y.; Yajima, H. J. Chem. Soc., Chem. Commun. 1972, 942–943; (d) Kiso, Y.; Kai, Y.;
Yajima, H. Chem. Pharm. Bull. 1973, 21, 2507–2510; (e) Sheehan, J. C.; Hess, G. P.
J. Am. Chem. Soc. 1955, 77, 1067–1068; (f) Gorecka, A.; Leplawy, M. T.; Zablocki,
J.; Zwierzak, A. Synthesis 1978, 474–476; (g) Ohta, A.; Inagawa, Y.; Okuwaki, Y.;
Shimazaki, M. Heterocycles 1984, 22, 2369–2373; (h) Yamada, S. I.; Kasai, Y.;
Shioiri, T. Tetrahedron Lett. 1973, 14, 1595–1598; (i) Cosmatos, A.; Photaki, J.;
Zervas, L. Chem. Ber. 1961, 94, 2644–2655; (j) Shioiri, T.; Ninomiya, K.; Yamada,
S. Z. J. Am. Chem. Soc. 1972, 94, 6203–6205; (k) Wernic, D.; Dimaio, J.; Adams, J. J.
Org. Chem. 1989, 54, 4224–4228; (l) Kim, S.; Chang, H.; Ko, Y. K. Tetrahedron Lett.
1985, 26, 1341–1342; (m) Ramage, R.; Ashton, C. P.; Hopton, D.; Parrot, M. J.
Tetrahedron Lett. 1984, 25, 4825–4828; (n) Jackson, A. G.; Kenner, G. W.; Moore,
G. A.; Ramage, R.; Thorpe, W. D. Tetrahedron 1976, 32, 3627–3630; (o) Galph, I. J.;
Mohammed, A. K.; Patel, A. Tetrahedron 1988, 44, 1685–1690.
5. (a) Streitwieser, A.; Wilkins, C. L.; Kiehlmann, E. J. Am. Chem. Soc. 1968, 90, 1598–
1601; (b) Su, T. M.; Sliwinski, W. F.; Schleyer, P. R. J. Am. Chem. Soc. 1969, 91,
5386–5388; (c) Beyl, V.; Niederprum, H.; Voss, P. Justus Liebigs Ann. Chem. 1970,
731, 58–66; (d) Chen, Q. Y.; Zhu, R. X.; Li, Z. Z.; Wang, S. D.; Huang, W. Y. Acta
Chim. Sinica 1982, 40, 337–340; (e) Chen, Q. Y.; He, Y. B. Synthesis 1988, 896–
897; (f) Bennua-Skalmowski, B.; Vorbruggen, H. Tetrahedron Lett. 1995, 36,
2611–2614; (g) Klar, U.; Neef, G.; Vorbruggen, H. Tetrahedron Lett. 1996, 37,
7497–7498; (h) Chen, Q. Y. J. Fluorine Chem. 1995, 72, 241–246; (i) Zhu, Z.; Tian,
W. S.; Liao, Q. J. Tetrahedron Lett. 1996, 37, 8553–8556; (j) Zhu, Z.; Tian, W. S.;
Liao, Q. J.; Wu, Y. K. Bioorg. Med. Chem. Lett. 1998, 8, 1949–1952; (k) Fei, X. S.;
Tian, W. S.; Chen, Q. Y. Bioorg. Med. Chem. Lett. 1997, 7, 3113–3118; (l) Fei, X. S.;
Tian, W. S.; Chen, Q. Y. J. Chem. Soc., Perkin Trans. 1 1998, 2, 1139–1142; (m) Tian,
W. S.; Lei, Z.; Chen, L.; Huang, Y. J. Fluorine Chem. 2000, 101, 305–308; (n) Chen,
L.; Ding, K.; Tian, W. S. Chem. Commun. 2003, 838–839; (o) Yan, Z.; Wang, J.;
Tian, W. Tetrahedron Lett. 2003, 44, 9383–9384; (p) Yan, Z.; Tian, W. Tetrahedron
Lett. 2004, 45, 2211–2213.
ꢁ
species and the bulky size of Rf SO3 moiety.
In conclusion,
a novel and efficient condensing reagent,
HCF2CF2OCF2CF2SO2F, for esterification and amidation is described.
It is especially suitable for esterification of carboxylic acids with pri-
mary alcohols, primary allylic alcohols and phenol derivatives, and
for amidation of carboxylic acids with linear primary amines. High
efficiency, mild reaction conditions and air- and moisture-stability
are the distinctive advantages for HCF2CF2OCF2CF2SO2F-induced
condensation reactions. In addition, HCF2CF2OCF2CF2SO2F/(CH3)3-
SiCN as a new anhydridization condensing agent system was also
developed. It can relatively efficiently induce the anhydridization
of some aromatic carboxylic acids to produce symmetrical aromatic
anhydrides in moderate to good yields. Their application in the
preparation of peptides and other interesting target molecules is
currently underway in our laboratory.
2. Experimental
2.1. General procedure for esterification, amidation and
anhydridization
6. Hansen, R. L. J. Org. Chem. 1965, 29, 4322–4424.
7. Rad, M. N. S.; Behrouz, S.; Faghihi, M. A.; Khalafi-Nezhad, A. Tetrahedron Lett.
2008, 49, 1115–1120.
The reaction was performed in one-pot procedure in CH2Cl2. At
room temperature, a solution of carboxylic acid (RCOOH) and DBU