Cupration of C2F5H: Isolation, structure, and synthetic applications of [K(DMF)2][(t -BuO)Cu(C2F 5)]. Highly efficient pentafluoroethylation of unactivated aryl bromides

Article abstract of DOI:10.1021/ja407017j

Pentafluoroethane, C₂F₅H (HFC-125), is smoothly cuprated with preisolated or in situ-generated [K(DMF)][(t-BuO)₂Cu] to give [K(DMF)₂][(t-BuO)Cu(C₂F₅)] (1) in nearly quantitative yield. Complex 1 has been isolated, structurally characterized, and demonstrated to be an exceedingly versatile pentafluoroethylating reagent for a variety of substrates, including unactivated aryl bromides.

Full text of DOI:10.1021/ja407017j

Communication
pubs.acs.org/JACS
Cupration of C2F5H: Isolation, Structure, and Synthetic Applications
of [K(DMF)2][(t‑BuO)Cu(C2F5)]. Highly Efficient Pentafluoroethylation
of Unactivated Aryl Bromides
Anton Lishchynskyi and Vladimir V. Grushin*
Institute of Chemical Research of Catalonia (ICIQ), Tarragona 43007, Spain
S
* Supporting Information
we report the facile synthesis of a new CuC2F5 reagent in nearly
ABSTRACT: Pentafluoroethane, C2F5H (HFC-125), is
smoothly cuprated with preisolated or in situ-generated
[K(DMF)][(t-BuO)2Cu] to give [K(DMF)2][(t-BuO)Cu-
(C2F5)] (1) in nearly quantitative yield. Complex 1 has
been isolated, structurally characterized, and demonstrated
to be an exceedingly versatile pentafluoroethylating
reagent for a variety of substrates, including unactivated
aryl bromides.
quantitative yield directly from inexpensive and readily available
C2F5H, an ozone-friendly refrigerant and a fire suppression
agent. We also describe full structural characterization of this
novel CuC2F5 species and its remarkable ability to pentafluoro-
ethylate a variety of substrates, including unactivated aryl
bromides, in a highly efficient manner.
We have recently found15 the first cupration reaction of
fluoroform (CHF3) and demonstrated the synthetic value of the
thus-produced CuCF3 in a variety of trifluoromethylation
reactions.15−17 A logical extension of these developments was
to examine whether this method could be applied to higher H-
perfluoroalkanes. To our surprise, under the conditions leading
to the highly selective cupration of fluoroform, CF3(CF2)nH (n =
2, 5, 7), H(CF2)6H, and (CF3)2CFH did not produce Cu−Rf but
rather gave KF/KHF2 and complex mixtures of organofluorine
products (19F NMR). An even bigger surprise came when, after
all these failures, C2F5H underwent exceedingly smooth and
clean cupration to give a C2F5Cu derivative in nearly quantitative
yield (Scheme 1). There have been no literature reports on the
preparation of CuC2F5 compounds directly from C2F5H.
luoroalkylated molecules are of special importance to the
F
development of modern agrochemicals, pharmaceuticals,
and specialty materials.1,2 A variety of methods are available for
the introduction of the smallest perfluoroalkyl group, CF3, into
organic substrates. Pentafluoroethylation reactions are vastly less
developed, despite the fact that in certain cases C2F5 derivatives
exhibit properties that are superior to those of their CF3
counterparts.3 Since the original work of Gassman and O’Reilly4
and more recent developments by Roschenthaler5a−d and
̈
others,5e C2F5Li has been successfully used for pentafluoroethy-
lation of carbonyl compounds and some other electrophiles.
Efficient alternative methods for the generation and synthetic
Scheme 1. Cupration of Rf−H
−
applications of C2F5 carbanion equivalents have been
reported.2k,6−8
The carbanion methodology,2k,4−8 however, is not applicable
to pentafluoroethylation of aromatic and other organic halides.
Moreover, pentafluoroethylated aromatic compounds cannot be
made by the Swarts-type process9 that is used to manufacture
benzotrifluorides (ArCF3). Currently available synthetic routes
to aromatic C2F5 derivatives are not only scarce but also suffer
from a narrow substrate scope and limited functional group
tolerance. Altogether, only two dozen or so pentafluoroethyla-
tion reactions of haloarenes have been reported in the literature.
The decarboxylative pentafuoroethylation of aryl iodides with
CuI/C2F5CO2M (M = Na, K, Me)10 occurs at 150−180 °C,
which is too high a temperature for a number of functional
groups to survive. Apart from the high cost and low availability of
the C2F5 silane source, the CuI/C2F5SiMe3/KF system11 has
been used for pentafluoroethylation of a handful of iodoarenes
bearing only Me, NO2, Ac, and CO2Et substituents on the ring. A
few aromatic C2F5 derivatives have been prepared from highly
activated (hetero)aryl iodides and CuC2F5 produced by thermal
decomposition of CuCF3.12,13 Pentafluoroethylation of unac-
tivated bromoarenes such as bromobenzene is unknown.14
As is clear from the above, the area of aromatic
pentafluoroethylation remains severely underdeveloped. Herein
Adding C2F5H to [K(DMF)][(t-BuO)2Cu],15 preisolated or
generated in situ from CuCl and t-BuOK (1:2), in N,N-
dimethylformamide (DMF) at room temperature resulted in an
instantaneous reaction. 19F NMR analysis of the resultant
solution indicated the formation of “CuC2F5” (ca. 95%) along
with traces (<1%) of [Cu(C2F5)2]−.18−20 The CuC2F5 product
appeared to be much more robust than the CuCF3 analogue
prepared in a similar manner from CHF3.15 This difference in
stability is explained by less facile α-F-elimination from higher
RfM complexes compared with their CF3M congeners. (For
Received: July 9, 2013
© XXXX American Chemical Society
A
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Journal of the American Chemical Society
Communication
instance, under conditions where C2F5Li is stable,4,5 CF3Li
decomposes to LiF and CF2.) The enhanced stability of the
C2F5H cupration product allowed for its isolation and study by
single-crystal X-ray diffraction. The structure of this novel
compound, [K(DMF)2][(t-BuO)Cu(C2F5)] (1),21 is shown in
Figure 1. Like [M(DMF)n][(t-BuO)2Cu] (M = Na, K),15 1 is a
produced the most efficient reagent.22 The latter was found to
pentafluoroethylate iodoarenes 2a−o in 90−99% yield at 23−50
°C (Scheme 2). A slight 20% excess of CuC2F5 was sufficient to
Scheme 2. Pentafluoroethylation of Aryl Iodides with C2F5H-
a
Derived CuC2F5
Figure 1. Structure and ORTEP drawing of [K(DMF)2][(t-BuO)Cu-
(C2F5)] (1) (S = μ-DMF-κ2O) with thermal ellipsoids drawn to the 50%
probability level and all H atoms omitted for clarity.
polymer in the solid state. Each two adjacent K atoms are bridged
by two μ-DMF-κ2O molecules and one μ-[(t-BuO)Cu(C2F5)]-
κ2O unit. The latter is similar to the μ-[(t-BuO)Cu(CF3)]-κ2O
link found previously15 in the structure of [Cu4(CF3)2(C(OBu-
t)2)2(μ3-OBu-t)2]. Only two X-ray structures of Cu−C2F5
compounds have been reported, one Cu(III) species,
[(C2F5)2Cu(S2CNEt2)],20 and one mixed Cu(I) ate complex,
[K(DMPU)3][(C2F5)CuCl].13 The Cu−C bond length in 1
(1.893(4) Å), while considerably shorter than that in the Cu(III)
complex (1.981(7) Å), is close in length to that found in the
[(C2F5)CuCl]− anion (1.916 Å). The Cu−C−C angles in the
structures of 1 (115.7(3)°), the Cu(III) complex (117.4(6)°),
and [(C2F5)CuCl]− (116.8°) are similar. The less stable and
consequently nonisolable primary product of the cupration of
fluoroform15 likely has a structure similar to that of 1.
We next explored the possibility of using 1 for pentafluoro-
ethylation of various substrates. First, the reactivity of 1 toward
aryl iodides was tested. For initial studies, 4-fluoroiodobenzene
was chosen as a substrate in order to extract more information
from monitoring the reaction by 19F NMR. No reaction of 1
generated from CuCl/t-BuOK (1:2) and C2F5H in DMF was
observed upon addition of 10 equiv of 4-IC6H4F at room
temperature, and only small amounts of 4-C2F5C6H4F were
produced after 3 h at 50 °C. After ca. 10 h at 80 °C, however, the
reaction reached full conversion of 1 to 4-C2F5C6H4F (19F NMR:
δ −84.4, 3F; −106.8, 1F; −113.2, 2F) and 4-t-BuOC6H4F (19F
NMR: δ −120.3) in a 1:1.2 ratio. Remarkably, no side
decomposition of 1 was observed. These results indicated that
(i) 1 is less reactive toward aryl halides yet much more thermally
stable than its CF3 analogue15,22 and (ii) like fluoroform-derived
CuCF3 prior to the stabilization,15 1 both fluoroalkylates and tert-
butoxylates the substrate.
a
Yields determined by 19F NMR using an internal standard.22
achieve full conversion of the starting ArI substrates. Electron-
withdrawing or -donating substituents at the ortho, meta, or para
position were easily tolerated, including simple alkyls (2b), MeO
(2c, 2d), CHO (2e), Cl (2f), Br (2g), CF3 (2h), CO2Et (2i), Ac
(2j), NO2 (2k), CN (2l), and CONH2 (2m). The reaction of 4-
IC6H4Br (2g) side-produced 1,4-(C2F5)2C6H4 (ca. 8%). Both 1-
iodonaphthalene and 2-iodopyridine underwent smooth fluo-
roalkylation, giving 3n and 3o in yields of 97% and 95%,
respectively.
Aryl bromides are much more cost-attractive and readily
available but significantly less reactive than iodoarenes. There
have been no reports of general methods for efficient
trifluoromethylation or pentafluoroethylation of unactivated
bromoarenes. We were pleased to find that our Cu reagent
pentafluoroethylated various bromo(hetero)arenes 4a−m at
80−90 °C with high selectivity in 80−99% yield (Scheme 3).
Even particularly challenging bromobenzene (4a), o- and p-
bromoanisole (4c and 4e), and m-bromotoluene (4d) were
smoothly converted to the corresponding C2F5 derivatives in
≥94% yield. 2-(Pentafluoroethyl)naphthalene (5j) and the three
heterocyclic derivatives 5k−m were produced in 90−96% yield
(19F NMR) and isolated in 82−97% yield (0.42−0.72 g).22 The
structure of 5j was confirmed by single-crystal X-ray diffraction
(Figure 2).
The tert-butoxylation side reaction was efficiently suppressed
by adding Et3N·3HF (TREAT HF) or Py·nHF to 1 in DMF prior
to use in pentafluoroethylation reactions. This technique was
adopted from our previous work with fluoroform-derived
CuCF3.15 Interestingly, it was found that not only HF sources
but also other acids such as AcOH or HCl in dioxane could be
used with 1 to eliminate the undesired tert-butoxylation. The best
results in the current work were obtained with TREAT HF.22,23
A series of optimization experiments indicated that adding 1.6
equiv of HF in the form of TREAT HF to a solution of 1
The CuC2F5 was found to be useful for pentafluoroethylation
of not only aryl halides but also a variety of other substrates
(Scheme 4), including arylboronic acids and terminal acetylenes
under oxidative conditions (in air), benzylic and vinylic
bromides, and metal complexes. Treatment of [(tmeda)Pd(Ph)-
I] with our CuC2F5 reagent gave [(tmeda)Pd(C2F5)(Ph)] (6),
which was isolated in 90% yield and fully characterized, including
by single-crystal X-ray diffraction (Figure 3). Palladium
complexes bearing a σ-C2F5 ligand are extremely rare because
of the lack of general methods for Pd−C2F5 bond formation.
B
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Journal of the American Chemical Society
Communication
C(Rf) bond lengths are longer for Rf = C2F5 (2.019(2) Å in 6 and
2.033(5) Å in 7) than for Rf = CF3 (1.993(1) Å in 8). This is
consistent with a decrease in the degree of s character in the
carbon’s hybrid orbital directed toward Pd upon replacement of
one F atom in 8 with the less electronegative CF3 to give 6
(Bent’s rule).28 The Pd−N bond distances trans to the Rf ligand
are similar for Rf = CF3 (2.169(1) Å in 8) and Rf = C2F5
(2.166(2) Å in 6 and 2.180(2) Å in 7) and are ca. 0.03−0.04 Å
shorter than those trans to the Ph and Me ligands. These data
show that the structural trans influences of C2F5 and CF3 are
indistinguishable within experimental error and somewhat
weaker than those of Me and Ph.
Scheme 3. Pentafluoroethylation of Aryl Bromides with
C2F5H-Derived CuC2F5
a
a
19F NMR (isolated) yields.22
Figure 3. ORTEP drawing of [(tmeda)Pd(C2F5)(Ph)] (6) with thermal
ellipsoids drawn to the 50% probability level and all H atoms omitted for
clarity.
Table 1. Selected Bond Distances (Å) for
[(tmeda)Pd(Rf)(R)]
Figure 2. ORTEP drawing of 2-C10H7C2F5 (5j) with thermal ellipsoids
drawn to the 50% probability level and all H atoms omitted for clarity.
Rf = C2F5
R = Ph (6)
(this work)
Rf = C2F5
R = Me (7)
(ref 24)
Rf = CF3
R = Ph (8)
(ref 26)
bond
Scheme 4. Pentafluoroethylation of Various Substrates with
C2F5H-Derived CuC2F5
Pd−C(Rf)
Pd−C(R)
Pd−N trans to Rf
Pd−N trans to R
2.019(2)
1.990(2)
2.166(2)
2.213(2)
2.033(5)
2.171(4)
2.180(2)
2.221(4)
1.993(1)
1.996(1)
2.169(1)
2.198(1)
A comment is due on the peculiar varying reactivity of different
H-perfluoroalkanes toward the dialkoxycuprate. The abrupt
change in reaction pathways for the CF3(CF2)nH/[K(DMF)]-
[(t-BuO)2Cu] system when going from n = 1 (cupration) to n > 1
(HF elimination) is not fully understood. It is conceivable that
HF elimination is preferred for C3 and higher H-perfluoro-
alkanes because the substituted olefinic products RfCFCF2 are
more stable than CF2CF2 that would result from dehydro-
fluorination of C2F5H. Mechanistic studies of this interesting
reactivity pattern are currently underway.
In conclusion, like CHF3 but unlike other higher H-
perfluoroalkanes, C2F5H undergoes smooth cupration with
[K(DMF)][(t-BuO)2Cu]. This reaction occurs at room temper-
ature and atmospheric pressure to give quantitatively [K-
(DMF)2] [(t-BuO)Cu(C2F5)] (1), which has been structurally
characterized. Complex 1, while being slightly less reactive
toward electrophiles than its CF3 counterpart, is much more
thermally stable. This stability allowed for highly efficient
pentafluoroethylation of not only iodoarenes (>90% yield) but
also much more inert unactivated aryl bromides (80−99% yield).
These reactions of bromoarenes are unprecedented. Efficient
C2F5 transfer has also been demonstrated from 1 to benzylic and
vinylic bromides, arylboronic acids, and terminal acetylenes
under oxidative conditions (in air) as well as to another metal
(Pd) center. This new methodology is likely to find use in both
academia and industry.
Only one such adequately characterized complex, [(tmeda)Pd-
(C2F5)(Me)],24 has been reported.25
The trans influence and electronic effects of the CF3 and
higher Rf groups are not without controversy.2r The X-ray
structures of 6 and its previously reported26 CF3 analogue 8
provided a unique opportunity to compare the structural trans
influences of C2F5 and CF3.27 Table 1 lists coordination bond
distances for 6 and its counterparts [(tmeda)Pd(Rf)(R)], where
Rf = C2F5, R = Me (7)24 and Rf = CF3, R = Ph (8).26 The three
structures display similar, nearly undistorted square-planar
geometries, suggesting no excessive steric crowding in the
coordination sphere. The almost identical Pd−C(R) bond
distances for R = Ph (1.990(2) Å in 6 and 1.996(1) Å in 8) are
slightly shorter than that for R = Me (2.171(4) Å in 7). The Pd−
C
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Journal of the American Chemical Society
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Fluorine Compounds; Roesky, H. W., Ed.; Wiley: Hoboken, NJ, 2013; p
205 and references cited therein. (e) Nagaki, A.; Tokuoka, S.; Yamada,
S.; Tomida, Y.; Oshiro, K.; Amii, H.; Yoshida, J.-i. Org. Biomol. Chem.
2011, 9, 7559.
(6) (a) Krishnamurti, R.; Bellew, D. R.; Prakash, G. K. S. J. Org. Chem.
1991, 56, 984. (b) Dilman, A. D.; Arkhipov, D. E.; Levin, V. V.;
Belyakov, P. A.; Korlyukov, A. A.; Struchkova, M. I.; Tartakovsky, V. A. J.
Org. Chem. 2008, 73, 5643. (c) Prakash, G. K. S.; Wang, Y.; Mogi, R.; Hu,
J.; Mathew, T.; Olah, G. A. Org. Lett. 2010, 12, 2932.
ASSOCIATED CONTENT
* Supporting Information
Full details of synthetic (PDF) and crystallographic (CIF)
studies. This material is available free of charge via the Internet at
http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
vgrushin@iciq.es
■
(7) (a) Barhdadi, R.; Troupel, M.; Perichon, J. Chem. Commun. 1998,
1251. (b) Russell, J.; Roques, N. Tetrahedron 1998, 54, 13771.
(8) (a) Petrov, V. A. Tetrahedron Lett. 2001, 42, 3267. (b) Pooput, C.;
Notes
́
Dolbier, W. R., Jr.; Medebielle, M. J. Org. Chem. 2006, 71, 3564.
(9) Filler, R. Adv. Fluorine Chem. 1970, 6, 1.
The authors declare no competing financial interest.
(10) (a) Davidson, R. I. U.S. Patent 4,822,904, 1989. (b) Carr, G. E.;
Chambers, R. D.; Holmes, T. F.; Parker, D. G. J. Chem. Soc., Perkin Trans.
1 1988, 921. (c) Freskos, J. N. Synth. Commun. 1988, 18, 965.
(d) Langlois, B. R.; Roques, N. J. Fluorine Chem. 2007, 128, 1318.
(11) Urata, H.; Fuchikami, T. Tetrahedron Lett. 1991, 32, 91.
(12) (a) Burton, D. J.; Wiemers, D. M.; Easdon, J. C. U.S. Patent
4,582,921, 1986. (b) Kremlev, M. M.; Tyrra, W.; Mushta, A. I.;
Naumann, D.; Yagupolskii, Y. L. J. Fluorine Chem. 2010, 131, 212.
(c) Kobayashi, Y.; Kumadaki, I. J. Chem. Soc., Perkin Trans. 1 1980, 661.
(13) One ArI substrate has been pentafluoroethylated with
[(DMPU)2Zn(C2F5)2] in the presence of CuCl (10%) and phen
(20%). See: Popov, I.; Lindeman, S.; Daugulis, O. J. Am. Chem. Soc.
2011, 133, 9286.
(14) (a) A few examples of pentafluoroethylation of activated
bromoarenes have been reported.10b,c,12b Attempted Cu-catalyzed
perfluoroalkylation of 4-bromobiphenyl with [(DMPU)2Zn(Rf)2]
generated in situ from RfH gave the desired product in <5% yield.13
(b) Pd-catalyzed borylation of a few unactivated aryl bromides followed
by oxidative fluoroalkylation of the resultant arylboronate esters with
[(phen)CuC2F5] has been reported. See: Litvinas, N. D.; Fier, P. S.;
Hartwig, J. F. Angew. Chem., Int. Ed. 2012, 51, 536.
ACKNOWLEDGMENTS
■
We thank Drs. Jordi Benet-Buchholz and Eddy Martin for single-
crystal X-ray diffraction studies and Dr. Alessandro Zanardi and
Maxim A. Novikov for selected preliminary experiments. The
ICIQ Foundation and the Spanish Government (Grant
CTQ2011-25418) are thankfully acknowledged for support of
this work.
REFERENCES
■
(1) For selected recent monographs, see: (a) Kirsch, P. Modern
Fluoroorganic Chemistry; Wiley-VCH: Weinheim, Germany, 2004.
(b) Uneyama, K. Organofluorine Chemistry; Blackwell: Oxford, U.K.,
2006. (c) Ojima, I. Fluorine in Medicinal Chemistry and Chemical Biology;
Wiley-Blackwell: Chichester, U.K., 2009. (d) Petrov, V. A. Fluorinated
Heterocyclic Compounds: Synthesis, Chemistry and Applications; Wiley:
Hoboken, NJ, 2009.
(2) For selected reviews, see: (a) Burton, D. J.; Yang, Z.-Y. Tetrahedron
1992, 48, 189. (b) McClinton, M. A.; McClinton, D. A. Tetrahedron
1992, 48, 6555. (c) Dolbier, W. R., Jr. Chem. Rev. 1996, 96, 1557.
(d) Umemoto, T. Chem. Rev. 1996, 96, 1757. (e) Burton, D. J.; Lu, L.
Top. Curr. Chem. 1997, 193, 45. (f) Prakash, G. K. S.; Yudin, A. K. Chem.
Rev. 1997, 97, 757. (g) Singh, R. P.; Shreeve, J. M. Tetrahedron 2000, 56,
7613. (h) Cahard, D.; Ma, J.-A. Chem. Rev. 2004, 104, 6119.
(i) Schlosser, M. Angew. Chem., Int. Ed. 2006, 45, 5432. (j) Cahard,
D.; Ma, J.-A. J. Fluorine Chem. 2007, 128, 975. (k) Uneyama, K.; Katagiri,
T.; Amii, H. Acc. Chem. Res. 2008, 41, 817. (l) Ma, J.-A.; Cahard, D.
Chem. Rev. 2008, 108, PR1. (m) Davis, C. R.; Burton, D. J. In The
Chemistry of Organocopper Compounds; Rappoport, Z., Marek, I., Eds.;
Wiley: Chichester, U.K., 2009. (n) Shibata, N.; Matsnev, A.; Cahard, D.
Beilstein J. Org. Chem. 2010, 6, 65. (o) Sato, K.; Tarui, A.; Omote, M.;
Ando, A.; Kumadaki, I. Synthesis 2010, 1865. (p) Dhara, M. G.; Banerjee,
S. Prog. Polym. Sci. 2010, 35, 1022. (q) Roy, S.; Gregg, B. T.; Gribble, G.
W.; Le, V.-D.; Roy, S. Tetrahedron 2011, 67, 2161. (r) Tomashenko, O.
A.; Grushin, V. V. Chem. Rev. 2011, 111, 4475. (s) Qing, F.-L.; Zheng, F.
Synlett 2011, 1052. (t) Dilman, A. D.; Levin, V. V. Eur. J. Org. Chem.
2011, 831. (u) Nie, J.; Guo, H.-C.; Cahard, D.; Ma, J.-A. Chem. Rev.
2011, 111, 455. (v) Grygorenko, O. O.; Artamonov, O. S.; Komarov, I.
(15) Zanardi, A.; Novikov, M. A.; Martin, E.; Benet-Buchholz, J.;
Grushin, V. V. J. Am. Chem. Soc. 2011, 133, 20901.
(16) Novak
2012, 51, 7767.
(17) Novak, P.; Lishchynskyi, A.; Grushin, V. V. J. Am. Chem. Soc. 2012,
134, 16167.
́
, P.; Lishchynskyi, A.; Grushin, V. V. Angew. Chem., Int. Ed.
́
(18) Reported 19F NMR data for “CuC2F5”: δ −82.8 (3F), −110.0
(2F).12,19 For [Cu(C2F5)2]−: δ −82.9 (3F), −116.1 (2F).14b,20
(19) Wiemers, D. M.; Burton, D. J. J. Am. Chem. Soc. 1986, 108, 832.
(20) Naumann, D.; Roy, T.; Caeners, B.; Hutten, D.; Tebbe, K.-F.;
Gilles, T. Z. Anorg. Allg. Chem. 2000, 626, 999.
(21) In contrast with the cupration of CHF3,15 which cannot be
efficiently carried out in THF, the reaction of preisolated [K(DMF)][(t-
BuO)2Cu] with C2F5H in THF afforded 1, albeit in a slightly lower yield
(81%). No formation of [Cu(C2F5)2]− was detected in this case.
(22) See the Supporting Information for details.
(23) In contrast with fluoroform-derived CuCF3,15 the CuC2F5 reagent
produced upon treatment with HCl or AcOH is stable.
V.; Mykhailiuk, P. K. Tetrahedron 2011, 67, 803. (w) Acena, J. L.;
Sorochinsky, A. E.; Soloshonok, V. A. Synthesis 2012, 44, 1591.
̃
(24) Hughes, R. P.; Meyer, M. A.; Tawa, M. D.; Ward, A. J.;
Williamson, A.; Rheingold, A. L.; Zakharov, L. N. Inorg. Chem. 2004, 43,
747.
(x) Mace,
́
Y.; Magnier, E. Eur. J. Org. Chem. 2012, 2479.
(3) See, for example: (a) Andrzejewska, M.; Yep
́
ez-Mulia, L.; Cedillo-
(25) The formation of [(Et3P)2Pd(C2F5)I] in unspecified yield via
condensation of Pd vapor with Et3P and C2F5I has been mentioned. See:
Klabunde, K. J.; Low, J. Y. F. J. Am. Chem. Soc. 1974, 96, 7674.
(26) Grushin, V. V.; Marshall, W. J. J. Am. Chem. Soc. 2006, 128, 4632.
(27) Although X-ray analysis has been performed for trans-
[(Ph2PMe)2Pt(Rf)Cl] (Rf = CF3, C2F5), packing disorder in the CF3
complex precludes comparison of the structural trans influences of C2F5
and CF3. It has been suggested on the basis of the ν(Pt−Cl) values that
the IR trans influences of CF3 and C2F5 are similar. See: Bennett, M. A.;
Chee, H.-K.; Robertson, G. B. Inorg. Chem. 1979, 18, 1061.
(28) Bent, H. A. Chem. Rev. 1961, 61, 275.
Rivera, R.; Tapia, A.; Vilpo, L.; Vilpo, J.; Kazimierczuk, Z. Eur. J. Med.
Chem. 2002, 37, 973. (b) Johansson, A.; Poliakov, A.; Åkerblom, E.;
Wiklund, K.; Lindeberg, G.; Winiwarter, S.; Danielson, U. H.;
Samuelsson, B.; Hallberg, A. Bioorg. Med. Chem. 2003, 11, 2551.
(4) (a) Gassman, P. G.; O’Reilly, N. J. Tetrahedron Lett. 1985, 26, 5243.
(b) Gassman, P. G.; O’Reilly, N. J. J. Org. Chem. 1987, 52, 2481.
(5) (a) Schneider, M.; Marhold, A.; Kolomeitsev, A.; Kadyrov, A.;
Roschenthaler, G.-V.; Barten, J. U.S. Patent 6,872,861, 2005.
(b) Kolomeitsev, A. A.; Kadyrov, A. A.; Szczepkowska-Sztolcman, J.;
Milewska, M.; Koroniak, H.; Bissky, G.; Barten, J. A.; Roschenthaler, G.-
V. Tetrahedron Lett. 2003, 44, 8273. (c) Shevchenko, N. E.; Nenajdenko,
̈
̈
V. G.; Roschenthaler, G.-V. J. Fluorine Chem. 2008, 129, 390.
̈
(d) Kazakova, O.; Roschenthaler, G.-V. In Efficient Preparations of
̈
D
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