2910
J . Org. Chem. 1999, 64, 2910-2913
Notes
a remarkably strong organic C-H Brønsted acid.7,8 Its
Tr is(tr iflu or om eth a n esu lfon yl)m eth id e
lithium salt, LiC(SO2CF3)3 1b, has been extensively
employed as an electrolyte in nonaqueous high voltage
batteries,9 displaying high anodic stability,10 and so the
tris(trifluoromethanesulfonyl)methide anion seemed ide-
ally suited for our purposes as a triflate replacement.
(“Tr iflid e”) An ion : Con ven ien t
P r ep a r a tion , X-r a y Cr ysta l Str u ctu r es, a n d
Excep tion a l Ca ta lytic Activity a s a
Cou n ter ion w ith Ytter biu m (III) a n d
Sca n d iu m (III)
Francis J . Waller,*,† Anthony G. M. Barrett,*,‡
D. Christopher Braddock,‡ Dorai Ramprasad,†
R. Murray McKinnell,‡ Andrew J . P. White,‡
David J . Williams,‡ and Richard Ducray‡
Air Products and Chemicals, Inc., 7201 Hamilton
Boulevard, Allentown, Pennsylvania 18195-1501 and
Department of Chemistry, Imperial College of
Science, Technology and Medicine, South Kensington,
London, UK SW7 2AY
Seppelt’s preparation of 1a calls for the use of trifluo-
romethanesulfonyl fluoride (bp -21 °C) as an electro-
philic triflyl source.7 Aside from the inconvenience of
handling gaseous reagents, CF3SO2F is not commercially
available and is typically prepared via electrochemical
fluorination with anhydrous HF,12 a highly hazardous
undertaking in most standard laboratories. We were
intrigued by the possibility of using readily available
triflic anhydride in lieu of CF3SO2F especially since the
failure of organometallic reagents to add cleanly to triflic
anhydride is well-documented.12,13 Herein we report a
practical and convenient two-step preparation of the tris-
(trifluoromethanesulfonyl)methide anion (which we have
given the trivial name of “triflide”), conveniently isolated
as its cesium salt 1c, employing triflic anhydride as the
electrophilic triflyl source. Additionally we report the
preparation of the corresponding ytterbium(III) and
scandium(III) salts, 1d and 1e, respectively, and compare
their catalytic competence for aromatic nitration of
o-nitrotoluene with ytterbium(III) and scandium(III)
triflates.
Received J anuary 20, 1998
The lanthanide(III) triflates are the focus of much
current research.1 Recently we have reported the use of
lanthanide(III) triflates2 and the superior tetrapositive
group IV metal triflates, hafnium and zirconium,3,4 as
recyclable atom economic catalysts for aromatic nitration.
In an attempt to further enhance the catalytic activity
of these salts for nitrations, we sought to modify the
triflate counterion.5 On the basis of our current mecha-
nistic understanding6 of our lanthanide(III) catalyzed
nitration protocol we sought a counterion that should be
(i) a conjugate base of a very strong acid, (ii) unaffected
by strongly oxidizing conditions, i.e., not oxidized by
concentrated nitric acid, (iii) nonoxidizing itself, preclud-
ing the use of, for example, perchlorate, (iv) hydrolysis
resistant, ruling out counterions such as PF6- and SbF6
and (v) of increased solubility in organic solvents com-
pared to triflate itself. Thus, our attention was drawn to
Seppelt’s seminal paper7 which details the preparation
of tris(trifluoromethylsulfonyl)methane, HC(SO2CF3)3 1a ,
-
,
Resu lts a n d Discu ssion
Slow addition of triflic anhydride to a stirred solution
of trimethylsilylmethyllithium in pentanes at 0 °C re-
sulted in smooth reaction as evidenced by the gradual
precipitation of lithium triflate with only a slight increase
in the internal temperature (max. ≈10 °C). Basic aqueous
quench, extraction with dichloromethane, and strong
acidification (concentrated HCl) of the remaining aqueous
phase followed by extraction with dichloromethane led
† Air Products and Chemicals, Inc.
‡ Imperial College of Science, Technology, and Medicine.
(1) Reviews: (a) Marshman, R. W. Aldrichimica Acta 1995, 28, 77.
(b) Kobayashi, S. Synlett 1994, 689. (c) Engberts, J . B. N. F.; Feringa,
B. L.; Keller, E.; Otto, S. Recl. Trav. Chim. Pays Bas 1996, 115, 457.
(2) Waller, F. J .; Barrett, A. G. M.; Braddock, D. C.; Ramprasad, D.
Chem. Commun. 1997, 613.
(3) Waller, F. J .; Barrett, A. G. M.; Braddock, D. C.; Ramprasad, D.
Tetrahedron Lett. 1998, 39, 1642.
(4) Kobayshi, S.; Moriwaki, M.; Hachiya, I. Bull. Chem. Soc. J pn.
1997, 70, 267 and references therein.
(8) 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.;
Ignat′ev, N. V.; Kondratenko, N. V.; Volkonskii, A. Y.; Vlasov, V. M.;
Notario, R.; Maria, P.-C. J . Am. Chem. Soc. 1994, 116, 3047.
(9) (a) Dominey, L. A. US Pat. 5273840, 1993.
(10) (a) Koch, V. R.; Dominey, L. A.; Nanjundiah, C.; Ondrechen,
M. J . J . Electrochem. Soc. 1996, 143, 798. (b) Walker, C. W., J r.; Cox,
J . D.; Salomon, M. J . Electrochem. Soc. 1996, 143, L80.
(11) (a) Gramstad, T.; Hazeldine, R. N. J . Chem. Soc. 1956, 173. (b)
Hu, L.-Q., DesMarteau, D. D. Inorg. Chem. 1993, 32, 5007.
(12) (a) Hendrickson, J . B.; Bair, K. W. J . Org. Chem. 1977, 42, 3875.
(b) Hendrickson, J . B.; Sternbach, D. D.; Bair, K. W. Acc. Chem. Res.
1977, 10, 306 and references therein.
(5) For the use of bis(trifluorosulfonylmethane)imide as a alternative
counterion in conjunction with lanthanides, see: (a) Kobayashi, H.;
Nie, J .; Sonada, T. Chem. Lett. 1995, 307. (b) Mikami, K.; Kotera, O.;
Motoyama, Y.; Sakaguchi, H.; Maruta, M. Synlett 1996, 171. For the
use of perfluorooctanesulfonate see: (c) Hanamoto, T.; Sugimoto, Y.;
J in, Y. Z.; Inanaga, J . Bull. Chem. Soc. J pn. 1997, 70, 1421. For the
use of a sulphonated resin as a “counterion” see: (d) Yu, L.; Chen, D.;
Li, J .; Wang, P. G. J . Org. Chem. 1997, 62, 3575.
(6) (a) Waller, F. J .; Ramprasad, D.; Barrett, A. G. M.; Braddock,
D. C. Catalysis of Organic Reactions; Herkes, F., Ed.; Marcel Dekker:
New York, 1998; p 289. (b) Waller, F. J .; Barrett, A. G. M.; Braddock,
D. C.; Ramprasad, D. J . Chem. Soc., Perkin Trans. 1 1999, in press.
(7) Turowsky, L.; Seppelt, K. Inorg. Chem. 1988, 27, 2135.
(13) Triflic anhydride is known to oxidize Grignard reagents:
Creary, X. J . Org. Chem. 1980, 45, 2727.
10.1021/jo9800917 CCC: $18.00 © 1999 American Chemical Society
Published on Web 03/26/1999