December 1998
SYNLETT
1347
Lanthanide Perfluoroalkylsulfonylamide Catalysts for Fluorous Phase Organic Synthesis
a
a
b
b
b
Joji Nishikido, Hitoshi Nakajima, Takao Saeki, Akihiro Ishii, † and Koichi Mikami *
aNoguchi Research Institute, Itabashi-ku, Tokyo 173-0003, Japan
bDepartment of Chemical Technology, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8552, Japan
FAX 3 5734 2776; kmikami@o.cc.titech.ac.jp
Received 1 September 1998
Abstract: Lanthanide perfluoroalkylsulfonylamide complexes catalyze
the Friedel-Crafts acylation and Diels-Alder reaction more efficiently
than AlCl and Yb(OTf) in benzotrifluoride and hexafluoro-p-xylene.
3
3
The fluorous phase organic synthesis was first introduced by Zhu, who
1
used fluorous solvents in organic synthesis. Horvath and Rabai then
2
proposed the concept of fluorous biphasic catalysis. The most effective
fluorous moieties in catalysts are branched or linear perfluoroalkyl
3
chains with a high carbon number (fluorous ponytails). In the course of
4
our research project on lanthanide complexes as efficient catalysts in
organic synthesis, we report the development of lanthanide bis-
perfluoroalkylsulfonylamide catalysts for fluorous phase organic
synthesis.
In summary, we report the development of lanthanide
perfluoroalkylsulfonylamide catalysts in fluorous phase organic
synthesis. Because fluorous synthesis combines the favorable
purification features of solid-phase synthesis with the favorable reaction
and analysis features of liquid-phase organic synthesis, it could prove
valuable in the automated synthesis of libraries of organic compounds.
Further work along this line, using fluorousyl catalysts directed towards
asymmetric catalysis, are now under way in our laboratory.
The bis-sulfonylimides, HN(SO Rf) (Rf: CF , C F , and C F ) possess
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2
3
2
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4 9
remarkably high Bronstead acidity and bis-perfluorobutylsulfonylimide,
HN(SO C F ) , in particular, is the strongest acid so far known in the
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4 9 2
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References and Notes
gas phase. Therefore, the conjugate bases of these acids bind very
weakly with metals, leading to the high Lewis acidity of the metal
†
On leave from Chemical Research Center, Central Glass Co. Ltd.,
Kawagoe, Saitama 350-1151, Japan
complexes.
Thus,
we
prepared
the
ytterbium
bis-
perfluorobutylsulfonylamide complexes, Yb(N(SO C F ) ) , according
1
2
Zhu, D.-W. Synthesis 1993, 953.
2
4 9 2 3
6
b
to the reported procedure for Yb(N(SO CF ) ) . The catalytic activity
2
3 2 3
(a) Horvath, I. T.; Rabai, J. Science 1994, 266, 72. Also see:
(b) Pereira, S. M.; Savage, G. P.; Simpson, G. W. Synth. Commun.
of Yb(N(SO C F ) ) (7 mol%) was examined in a haloalkane
2
4 9 2 3
7
alternative, benzotrifluoride (BTF), at room temperature as compared
1
995, 25, 1023. (c) Hughes, R. P.; Trujillo, H. A. Organometallics
3
with those of typical Lewis acid complexes, such as AlCl or Yb(OTf)3
1996, 15, 286. (d) Curran, D. P.; Hadida, S. J. Am. Chem. Soc.
1996, 118, 2531. (e) Klement, I.; Lutjens, H.; Knochel, P. Angew.
Chem., Int. Ed. Engl. 1997, 36, 1454.
in the Friedel-Crafts acylation with acetic anhydride of anisol. AlCl3
and Yb(OTf)3 were insoluble in BTF, however, and no acylation
product was formed within 1 h. In contrast, Yb(N(SO C F ) )
n 2n+1 2 3
2
3
4
(a) Gladysz, J. A. Science 1994, 266, 55. (b) Horvath, I. T. In
Applied Homogeneous Catalysis with Organometallic
Compounds; Cornils, B.; Herrmann, W., Eds.; VCH Press:
Weinheim, 1996; p 601.
produced the acylation product, the yield increasing with elongating
perfluoroalkyl chains. When the reaction temperature was increased
(
40°C), an almost quantitative yield of the acylation product of anisol
was obtained by using Yb(N(SO C F ) ) (10 mol%) after 2 h (eq. 1).
2
4 9 2 3
Mikami, K.; Terada, M.; Nakai, T. Ann. Meeting of Chem. Soc.
Jpn., April 1986, 3Y29, 3Y30. Mikami, K.; Terada, M.; Nakai, T.
J. Org. Chem. 1991, 56, 5456; Tetrahedron: Asymm. 1991, 2, 993;
J. Chem. Soc. Chem. Commun. 1993, 343. Mikami, K.; Kotera,
O.; Motoyama, Y.; Sakaguchi, H. Synlett 1995, 975. Ishii, A.;
Kotera, O.; Saeki, T.; Mikami, K. Synlett 1997, 1145. Mikami,
K.; Kotera, O.; Motoyama, Y.; Tanaka, M. Inorg. Chem. Commun.
A similar reaction of anisol with acetic anhydride in α,α,α,α’,α’,α’-
hexafluoro-p-xylene also produced a high yield (94%) of the acylation
product. It should be noted that a one-phase system could be obtained
under the reaction conditions. Higher catalytic activity of
Yb(N(SO C F ) ) than Yb(OTf)3 was also observed with respect to
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the same acylation reaction in a homogeneous reaction system in
CH CN (5 mol% of Yb catalyst, 70 °C, 1 h) (Yb(N(SO C F ) ) : 75%
3
2 4 9 2 3
1
998, 1, 10, and references cited therein.
yield; Yb(N(SO CF ) ) : 61% yield; Yb(OTf) : 25% yield). Similar
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3 2 3
3
5
(a) Koppel, I. A.; Taft, R. W.; Anvia, F.; Zhu, S.-Z.; Hu, L.-Q.;
Sung, K. S.; DesMarteau, D. D.; Yagupolskii, L. M.; Yagupolskii,
Y. L.; Ignatev, N. V.; Kondratenko, N. V.; Volkonskii, A. Y.;
Vlasov, V. M.; Notario, R.; Maria, P.-C. J. Am. Chem. Soc. 1994,
reactions, such as acylation of alcohol (eq. 2) or the Diels-Alder reaction
of 2,3-dimethylbutadiene with methylvinylketone (eq. 3), were
examined by the catalytic use of Ln(N(SO C F ) ) as compared with
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the results obtained with Yb(OTf) . These results clearly indicate the
3
1
16, 3047. (b) Nie, J. Ph.D. Thesis, Kyushu University, 1995; We
higher catalytic activity of Yb(N(SO C F ) ) than the corresponding
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8
are grateful to Profs. H. Kobayashi and T. Sonoda.
Yb(OTf)3
.
Nishikido, Joji
