Preparation, structure, and reactions of trifluoroacetimidoyl palladium(II) complexes

Article abstract of DOI:10.1021/om201021b

Trifluoroacetimidoyl metal complexes are useful intermediates for the selective synthesis of organofluorine compounds. Herein, we report preparations, structures, and reactions of fluorinated imidoyl palladium complexes. Oxidative addition of trifluoroacetimidoyl halides to Pd(PPh₃)₄ afforded quantitatively the imidoyl palladium(II) complexes with phosphine ligands. The reaction of trifluoroacetimidoyl iodides with Pd ₂(dba)₃ provided the phosphine-free imidoyl palladium complex in high yields. The X-ray crystal structure analysis of the phosphine-free complex [Pd(μ-I){μ-C(CF₃)=N(PMP)}]₄ revealed a cyclic tetranuclear structure containing the imidoyl and iodo bridges. The generation of aminotrifluoromethylcarbene equivalents by protonation or electrophilic alkylation of imidoyl palladium(II) complexes is discussed.

Full text of DOI:10.1021/om201021b

Article
pubs.acs.org/Organometallics
Preparation, Structure, and Reactions of Trifluoroacetimidoyl
Palladium(II) Complexes
Hideki Amii,*,†,‡ Katsuhiko Kageyama,† Yosuke Kishikawa,† Tsuyoshi Hosokawa,† Ryo Morioka,‡
Toshimasa Katagiri,† and Kenji Uneyama*,†
†Department of Applied Chemistry, Faculty of Engineering, Okayama University, Okayama 700-8530, Japan
‡Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515 Japan
S
* Supporting Information
ABSTRACT: Trifluoroacetimidoyl metal complexes are useful intermediates
for the selective synthesis of organofluorine compounds. Herein, we report
preparations, structures, and reactions of fluorinated imidoyl palladium
complexes. Oxidative addition of trifluoroacetimidoyl halides to Pd(PPh3)4
afforded quantitatively the imidoyl palladium(II) complexes with phosphine
ligands. The reaction of trifluoroacetimidoyl iodides with Pd2(dba)3 provided
the phosphine-free imidoyl palladium complex in high yields. The X-ray crystal
structure analysis of the phosphine-free complex [Pd(μ-I){μ-C(CF3)
N(PMP)}]4 revealed a cyclic tetranuclear structure containing the imidoyl
and iodo bridges. The generation of aminotrifluoromethylcarbene equivalents
by protonation or electrophilic alkylation of imidoyl palladium(II) complexes is
discussed.
the Suzuki−Miyaura protocols, trifluoroacetyl and trifluoroace-
timidoyl moieties were successfully introduced to aromatic
compounds (eqs 3 and 4).9,10
INTRODUCTION
■
The application of transition metals to organic synthesis is one
of the most interesting interdisciplinary topics in chemistry.
There have been numerous transition-metal-catalyzed reactions
that are impossible to be achieved by conventional synthetic
methods. In particular, the breadth of organopalladium
chemistry has caused revolutionary changes in organic
synthesis.1 Meanwhile, organofluorine compounds have
attracted huge interest in various industrial sectors, because
incorporation of fluorine atoms or fluoroalkyl groups often
furnishes organic molecules with unique properties that cannot
be attained using any other element.2 Thus, enormous numbers
of fluorine-containing compounds have been widely used in
various fields, including pharmaceuticals, agrochemicals, dyes,
liquid crystals, and polymers. Recently, a great deal of attention
has been paid to transition-metal-catalyzed reactions to
introduce fluorine-containig substituents into organic mole-
cules.3 For instance, outstanding progress has been made in
cross-coupling reactions for installing fluoro and trifluorometh-
yl groups into aromatic rings (eqs 1 and 2).4−8 By the use of
For synthetic organofluorine chemistry, trifluoroacetimidoyl
halides 1 (X = Cl, Br, I) are highly integrated multifunctional
building blocks due to their potentially reactive sites, such as
halogens, C−N double bonds, CF3, and N-aryl groups.11
Trifluoroacetimidoyl chlorides are easily prepared in high yield
by refluxing a mixture of commercially available trifluoroacetic
acid (TFA), amines, PPh3, and Et3N in CCl4 in a one-pot
manner.12 Trifluoroacetimidoyl iodides were obtained by
halogen-exchange reaction of the corresponding chlorides
with NaI in acetone quantitatively. From the early 1990s, our
group started the systematic investigation of palladium-
catalyzed transformations by the use of trifluoroacetimidoyl
Special Issue: Fluorine in Organometallic Chemistry
Received: October 22, 2011
Published: December 21, 2011
© 2011 American Chemical Society
1281
dx.doi.org/10.1021/om201021b | Organometallics 2012, 31, 1281−1286

Organometallics
Article
halides 1. Carbon−carbon bond formations, such as Heck
reactions, Sonogashira reactions, and reductive homocoupling
of imidoyl halides 1, were developed (Scheme 1).13,14
addition of C−X bonds of imidoyl halides into metal
complexes.28,29 Among them, oxidative addition of imidoyl
halides is the most straightforward method to prepare imidoyl
palladium complexes. We commenced synthesis of fluorinated
imidoyl palladium complexes
(triphenylphosphine)palladium as a Pd(0) source.
2 using tetrakis-
Scheme 1
Trifluoroacetimidoyl iodide 1a was treated with Pd(PPh3)4 in
benzene at room temperature for 24 h, and oxidative addition
took place to give the trifluoroacetimidoyl palladium(II)
complex 2a quantitatively (Scheme 2). The reactions of the
Scheme 2
imidoyl chlorides 1b−1c with Pd(PPh3)4 under the same
experimental conditions afforded the corresponding palladium-
(II) phosphine complexes 2b−2c in high yields.
The iodide complex 2a crystallized in the monoclinic space
group P21/n (No. 14). The ORTEP drawing of 2a is shown in
Figure 1. The geometry at the Pd is trans square-planar; the
sum of the four angles at palladium is 359.97°.
Pd-catalyzed carboalkoxylation of imidoyl iodides is a
convenient protocol for the synthesis of fluorinated iminoesters
6,15 which are useful precursors for asymmetric synthesis of
fluorinated amino acids.16 Besides substitution reactions,
trifluoroacetimidoyl halides underwent the addition reactions
to unsaturated organic molecules. In 2008, our group
demonstrated the first intramolecular chloroimidoylation of
carbon−carbon triple bonds.17 Kuniyasu and Kambe succeeded
in the intermolecular thioimidoylation of alkynes to give the
adducts 7 in a highly regioselective fashion.18
As highlighted so far, the Pd-catalyzed reactions of imidoyl
halides 1 are valuable for a wide repertoire of organofluorine
compounds. In these transformations, the key intermediates are
trifluoroacetimidoyl palladium(II) complexes that are generated
by oxidative addition of the C−X bonds of imidoyl halides 1
into Pd(0) species. Toward the evolution of new Pd-catalyzed
reactions of imidoyl halides 1, we were interested in the
isolation of trifluoroacetimidoyl palladium complexes 2. Herein,
we report the synthesis and the structural analysis of
trifluoroacetimidoyl palladium(II) complexes 2. Furthermore,
we explored the electrophilic transformation of the imidoyl
ligands in 2 to give amino(trifluoromethyl)carbene equivalents.
Figure 1. Molecular structure of palladium complex 2a.
The iminoacyl unit of 2a has completely trigonal-planar
geometry, the sum of the bond angles around the C(1) atom
being 359.5°. The CN bond distance of 2a (1.28 Å) is similar
to those reported for typical C−N double bonds (1.30 Å). The
PMP group on the nitrogen of the imine moiety is bound in
syn geometry; the lone pair of electrons on the nitrogen atom is
anticoplanar to the palladium center. The X-ray structure of 2a
reveals that the imidoyl ligand is bound to the Pd(II) center in
an η1-coordination mode and the plane of the iminoacyl group
(involving the p-methoxyphenyl group on nitrogen) is oriented
perpendicularly to that of the palladium center in the crystal.
The Migita−Kosugi−Stille coupling is a versatile C−C bond-
forming reaction between organostannanes and organic halides
with a high level of functional group tolerance under neutral
conditions.30,31 The reactions of the imidoyl palladium(II)
complexes 2 with organotin compounds were examined
(Scheme 3). A mixture of isolated Pd complex 2a and Ph-
RESULTS AND DISCUSSION
■
Synthesis of Trifluoroacetimidoyl Palladium(II) Phos-
phine Complexes. To date, there has been considerable
interest in the chemistry of metal complexes containing imidoyl
ligands because they are equivalents of an acyl metal species.
The principal preparative methods for these complexes have
involved (1) migratory insertion reaction of isocyanide ligands
into carbon−metal σ bonds in alkyl−metal complexes,19−23 (2)
nucleophilic alkylation of isocyanide ligands in metal
complexes,24 (3) isomerization of nitrile-coordinated com-
plexes (π to σ),25 (4) deprotonation of amino carbene
complexes,26 (5) halogen displacement of imidoyl halides by
anion complexes of transition metals,27 and (6) oxidative
1282
dx.doi.org/10.1021/om201021b | Organometallics 2012, 31, 1281−1286

Organometallics
Article
Scheme 3
SnBu3 in DMF was heated at 60 °C for 20 h.; the
transmetalation and reductive elimination proceeded smoothly
to afford trifluoromethylated imine 8 in 54% yield.
Synthesis of Phosphine-Free Trifluoroacetimidoyl
Palladium(II) Complex. Phosphines serve as important
ligands for transition-metal-catalyzed reactions that coordinate
to stabilize the reactive metal centers and that affect the
reactivity of the catalysts. In some cases, the coordination of
phosphine ligands to metal centers decreases the efficiency of
the catalytic reactions, because it is considered that the
phosphine ligands occupy the reactive coordination sites in
the intermediate metal complexes. For instance, the Pd-
catalyzed carboalkoxylation and Heck-type reactions of
trifluoroacetimidoyl iodide 1a proceeded smoothly in the
absence of phosphine ligands. Presumably, these reactions
involve the intermediate phosphine-free imidoyl palladium(II)
complexes. There are several reports of the phosphine-free
palladium imidoyl complexes that are stabilized by other
ligands, such as tetrahydrothiophene (THT), amines, and
isocyanides. To our knowledge, there has been only one report
Figure 2. Molecular structure of phosphine-free Pd complex 2d.
Four pairs of (C- and N-bonded) imidoyl and iodo bridges
might contribute a remarkable stability for this structure to
achieve a coordination number of 4 (square-planar) at each Pd
atom.32 The distance between Pd(1)···Pd(2) was 3.62 Å. It is
much longer than the sum of the covalent radii of Pd(II) (2.56
Å); thus, there is no bond between Pd atoms in the complex
2d. In comparison with the phosphine complex 2a, the p-
methoxyphenyl group on nitrogen of the imine moiety is bound
in anti geometry; the lone pair of electrons on the nitrogen
atom is directed toward the neighbor Pd atom. The twist angle
around the imidoyl plane and the phenyl ring of PMP group is
37.2°. The CN bond distances of 2d (1.27 Å) is similar to
those reported for typical C−N double bonds (1.30 Å).
A potential practical use for the complex 2d is as a catalyst
for carboalkoxylation. The tert-butyl group is a fascinating
protecting group of a carboxylic acid because of easy removal
under acidic conditions.15b The isolated complex 2d was
treated with tert-butyl alcohol (solvent) in the presence of
K2CO3 at atmospheric pressure of carbon monoxide to give
tert-butyl iminoester 6a in 35% yield (Scheme 5). Interestingly,
by Uson
́
et al. on the isolation of [Pd(X){C(C6F5)NMe}]n
(X = Cl, Br, I), which have the imidoyl and halogen ligands
without other stabilizing organic ligands.23q,r They synthesized
these complexes by insertion reaction of methylisocyanide into
C−Pd σ bonds in the C6F5−palladium complexes; however,
they did not provide the structural detail about these oligomeric
complexes. From the viewpoint of the structural interest, we
have tried isolation and X-ray crystal structure analysis of the
phosphine-free complex [Pd(X){C(CF3)NAr}]n produced
by oxidative addition of the imidoyl halides to Pd(0).
The reaction of imidoyl iodide 1a with Pd2(dba)3·CHCl3
(2:1 molar ratio) in toluene at room temperature gave a new,
stable complex 2d (Scheme 4). The crude product was purified
Scheme 5
Scheme 4
by silica gel column chromatography to give orange crystals of
pure 2d in 92% yield. Meanwhile, the reaction of imidoyl
chloride 1b with Pd2(dba)3·CHCl3 did not proceed under the
same condition because of the lower reactivity of 1b compared
with that of the corresponding iodide 1a.
Elemental analysis of 2d was in accord with the composition
[Pd(I){C(CF3)N(PMP)}]4. Crystals of 2d (which are
monoclinic; a = 18.6641(6) Å, b = 14.0538(5) Å, c =
19.4447(5) Å; β = 108.495(2)°; Z = 16; space group, C2/c
(No. 15)) have been confirmed to be cyclic tetranuclear
complexes by X-ray crystal structure analysis. The molecular
structure of complex 2d ([Pd(μ-I){μ-C(CF3)N(PMP)}]4) is
shown in Figure 2.
the yield of the tert-butyl ester 6a dramatically increased to 77%
when the reaction was conducted in the presence of an additive,
such as 1,3-dimethyl-2-imidazolidinone (DMI). The additive
DMI might act as a polar solvent to enhance the nucleophilicity
of tert-butyl alcohol and/or as a weak ligand enough to reduce
aggregation of the imidoyl palladium species 2d, which blocks
1283
dx.doi.org/10.1021/om201021b | Organometallics 2012, 31, 1281−1286

Organometallics
Article
Pd coordination sites, and to accelerate the coordination of CO
to palladium.
information for the structure of N-methylation product 11, the
following experiments were conducted. When complex 11 was
heated under an O2 atmosphere in a sealed tube at 150−170
°C, N-methyl-N-hexyl amide 12 was formed in 34% yield.
Instead of molecular oxygen, when an excess amount of
elemental sulfur (S8) was utilized, N-methyl-N-hexyl thioamide
13 was isolated in 44% yield. From these experiments, the
existence of an α-(dialkylamino)-α-trifluoromethylcarbene
moiety in the palladium complex 11 was proved.
Insertion of carbene ligands into sulfur−hydrogen σ bonds is
one of the interesting reactions of metal−carbene complexes.
Treatment of the imidoyl palladium(II) complexes 2c with 2
equiv of methyl thioglycolate at 170 °C under neat conditions
afforded 1,3-thiazolin-4-one 14 in 93% yield (Scheme 8). The
Generation of Trifluoromethyl(amino)carbene Equiv-
alents. The chemistry of carbene intermediates has been of
considerable interest to various fields of science.33,34 These
highly reactive species are now widely used in synthesis, and
recently, the isolation of stable crystalline carbenes has led to a
renaissance in carbene chemistry.35 Trifluoromethyl carbenes 9
are known to be very unstable because strongly electron-
withdrawing trifluoromethyl groups destabilize the carbene
centers (Scheme 6).36,37 Owing to their high reactivities,
Scheme 6
Scheme 8
trifluoromethyl carbenes are used as photoaffinity labels in
biochemistry.38 Heteroatom-substituted trifluoromethyl car-
benes are structurally fascinating because they contain both
electron-donating and electron-withdrawing substituents on the
carbene centers. In 2000, Bertrand succeeded in isolation of
stable push−pull carbenes, such as phosphanyl-
(trifluoromethyl)carbene, which were stabilized by both
mesomeric and inductive donating effects of phosphine
atoms.35 To the best of our knowledge, there has been no
example of amino(trifluoromethyl)carbenes, the compounds
with neutral dicoordinate carbon atoms with trifluoromethyl
and amino groups, which are considered to be promising
building blocks for synthetic organic chemistry. On the other
hand, metal carbenes have been important exhibits in the
organometallic showcase.39 Transition-metal carbene com-
plexes are one of the useful candidates for trifluoromethylated
dicoordinate carbon compounds. It is known that the reactions
of electrophiles with nitrogen atoms of the iminoacyl ligands in
imidoyl metal complexes provide aminocarbene com-
plexes.40−42 We tried to synthesize amino(trifluoromethyl)-
carbene−palladium complexes 10 by the use of trifluoroaceti-
midoyl palladium(II) complexes 2 as starting materials.
When imidoyl phosphine complex 2c was treated with
trimethyloxonium tetrafluoroborate (Me3O+BF4−, so-called
Meerwein’s reagent), electrophilic methylation of the nitrogen
atom in imidoyl palladium 2c took place to afford new Pd
complex 11 (Scheme 7).
formation of 14 suggests that thioglycolate serves as a proton
source in the reaction and protonation of 2c at the nitrogen
takes place to give the carbene complex 15 in the initial step.
The carbene ligand in Pd complex 15 then undergoes insertion
into the S−H bond of thioglycolate to provide the N,S-acetal of
fluoral (16). Subsequent intramolecular amide formation of the
intermediate 16 gives rise to thiazolinone 14.
CONCLUSIONS
■
Development of organic transformations based on oxidative
addition of fluorinated imidoyl halides to Pd(0) has brought a
wide variety of useful organofluorine compounds. We have
disclosed preparations, structures, and reactions of trifluor-
oacetimidoyl palladium(II) complexes. The reactions of
trifluoroacetimidoyl halides with Pd(PPh3)4 afforded the
imidoyl palladium(II) phosphine complexes in high yield. By
the reaction of the trifluoroacetimidoyl iodide with Pd2(dba)3,
the phosphine-free trifluoroacetimidoyl palladium(II) complex
was synthesized and fully characterized. Electrophilic trans-
formations of the trifluoroacetimidoyl palladium(II) complexes
gave α-amino-α-trifluoromethylcarbene equivalents. Further
studies concerning the catalytic protocols for the generation
of trifluoromethylated carbene species are currently under
investigation.
Scheme 7
ASSOCIATED CONTENT
■
S
* Supporting Information
Elemental analysis of 11 was in accord with the composition
of the structure for the amino(trifluoromethyl)carbene−
palladium. However, unfortunately, we could not obtain good
crystals of the complex 11 for X-ray analysis. To obtain the
Details of experimental procedures and characterization data
(1H, 19F, and 31P NMR; IR; and mass spectrometry) for all new
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
1284
dx.doi.org/10.1021/om201021b | Organometallics 2012, 31, 1281−1286

Organometallics
Article
Am. Chem. Soc. 2009, 131, 3796. (n) Furuya, T.; Kaiser, H. M.; Ritter,
T. Angew. Chem., Int. Ed. 2008, 47, 5993. (o) Furuya, T.; Benitez, D.;
Tkatchouk, E.; Strom, A. E.; Tang, P.; Goddard, W. A. III; Ritter, T. J.
Am. Chem. Soc. 2010, 132, 3793. (p) Furuya, T.; Strom, A. E.; Ritter,
T. J. Am. Chem. Soc. 2009, 131, 1662. (q) Furuya, T.; Ritter, T. Org.
Lett. 2009, 11, 2860. (r) Tang, P.; Furuya, T.; Ritter, T. J. Am. Chem.
Soc. 2010, 131, 12150. (s) Nemoto, H.; Nishiyama, T.; Akai, S. Org.
Lett. 2011, 13, 2714. (t) Tang, P.; Wang, W.; Ritter, T. J. Am. Chem.
Soc. 2011, 133, 11482. (u) Lee, E.; Kamlet, A. S.; Powers, D. C.;
Neumann, C. N.; Boursalian, G. B.; Furuya, T.; Choi, D. C.; Hooker, J.
M.; Ritter, T. Science 2011, 334, 639.
(6) Recent reports on Cu-catalyzed cross-coupling for trifluorome-
thylation: (a) Xiao, J.-C.; Ye, C.; Shreeve, J. M. Org. Lett. 2005, 7,
1963. (b) Dubinina, G. G.; Furutachi, H.; Vicic, D. A. J. Am. Chem. Soc.
2008, 130, 8600. (c) Dubinina, G. G.; Ogikubo, J.; Vicic, D. A.
Organometallics 2008, 27, 6233. (d) Kieltsch, I.; Dubinina, G. G.;
Hamacher, C.; Kaiser, A.; Torres-Nieto, J.; Hutchison, J. M.; Klein, A.;
Budnikova, Y.; Vicic, D. A. J. Fluorine Chem. 2010, 131, 1108. (e) Chu,
L.; Qing, F.-L. Org. Lett. 2010, 12, 5060. (f) Zhang, C.-P.; Wang, Z.-L.;
Chen, Q.-Y.; Zhang, C.-T.; Gu, Y.-C.; Xiao, J.-C. Angew. Chem., Int. Ed.
AUTHOR INFORMATION
Corresponding Author
*Fax: +44 277 30 1280. E-mail: amii@chem-bio.gunma-u.ac.jp
(H.A.), uneyamak@cc.okayama-u.ac.jp (K.U.).
■
ACKNOWLEDGMENTS
■
The financial support from the Ministry of Education, Culture,
Sports, Science and Technology of Japan is gratefully
acknowledged. We thank Prof. Yoshio Nogami (Okayama
University), Prof. Toshiyuki Oshiki (Okayama University), and
Prof. Soichiro Kyushin (Gunma University) for their kind help
of X-ray crystal structure analyses. We are also grateful to Prof.
Nobuhiro Takeda (Gunma University) and Ms. Natsuko
Uekusa (Gunma University) for their assistance in the 31P
NMR study.
REFERENCES
■
(1) (a) Tsuji, J. Palladium Reagents and Catalysts: New Perspectives for
the 21st Century; Wiley: Chichester, U.K., 2004. (b) de Meijere, A.,
Diederich, F., Eds. Metal-Catalyzed Cross-Coupling Reactions; Wiley-
VCH: Weinheim, Germany, 2004. (c) Negishi, E., de Meijere, A., Eds.
Handbook of Organopalladium Chemistry for Organic Synthesis; Wiley-
Interscience: New York, 2002.
2011, 50, 1896. (g) Knauber, T.; Arikan, F.; Roschenthaler, G.-V.;
̈
Gooβen, L. J. Chem.Eur. J. 2011, 17, 2689. (h) Senecal, T. D.;
Parsons, A. T.; Buchwald, S. L. J. Org. Chem. 2011, 76, 1174.
(i) Morimoto, H.; Tsubogo, T.; Litvinas, N. D.; Hartwig, J. F. Angew.
Chem., Int. Ed. 2011, 50, 3793. (j) Xu, J.; Luo, D.-F.; Xiao, B.; Liu, Z.-
J.; Gong, T.-J.; Fu, Y.; Liu, L. Chem. Commun. 2011, 47, 4300. (k) Liu,
T.-F.; Shen, Q.-L. Org. Lett. 2011, 13, 2342. (l) Popov, I.; Lindeman,
S.; Daugulis, O. J. Am. Chem. Soc. 2011, 133, 9286. (m) Weng, Z. Q.;
Lee, R.; Jia, W. G.; Yuan, Y. F.; Wang, W. F.; Feng, X.; Huang, K.-W.
Organometallics 2011, 30, 3229. (n) Li, Y. M.; Chen, T.; Wang, H. F.;
Zhang, R.; Jin, K.; Wang, X. N.; Duan, C. Y. Synlett 2011, 1713.
(o) Kawai, H.; Furukawa, T.; Nomura, Y.; Tokunaga, E.; Shibata, N.
(2) (a) Welch, J. T.; Eswarakrishnan, S. Fluorine in Bioorganic
Chemistry; John Wiley & Sons: New York, 1991. (b) Filler, R.,
Kobayashi, Y., Yagupolskii, L. M., Eds. Organofluorine Compounds in
Medicinal Chemistry and Biomedical Applications; Studies in Organic
Chemistry; Elsevier Science Ltd.: Amsterdam, 1993; Vol. 48.
(c) Banks, R. E., Smart, B. E., Tatlow, J. C., Eds. Organofluorine
Chemistry: Principles and Commercial Applications; Topics in Applied
Chemistry; Plenum Publishing Corp.: New York, 1994. (d) Ojima, I.,
McCarthy, J. R., Welch, J. T., Eds. Biomedical Frontiers of Fluorine
Chemistry; ACS Symposium Series 639; American Chemical Society:
Washington, DC, 1996. (e) Hiyama, T. Organofluorine Compounds:
Chemistry and Applications; Springer-Verlag: Berlin, 2000. (f) Kirsch, P.
Modern Fluoroorganic Chemistry: Synthesis, Reactivity, Applications;
Wiley-VCH: Weinheim, Germany, 2004. (g) Chambers, R. D. Fluorine
in Organic Chemistry; Blackwell: Oxford, U.K., 2004. (h) Uneyama, K.
Organofluorine Chemistry; Blackwell: Oxford, U.K., 2006. (i) Begue, J.-
́ ́
P.; Bonnet-Delpon, D. Bioorganic and Medicinal Chemistry of Fluorine;
John Wiley & Sons, Inc.: Hoboken, NJ, 2008.
(3) Clark, J. H.; Wails, D.; Bastock, T. W. Aromatic Fluorination;
CRC Press: Boca Raton, FL, 1996.
(4) (a) Grushin, V. V.; Marshall, W. J. Acc. Chem. Res. 2010, 43, 160.
(b) Lundgren, R. J.; Stradiotto, M. Angew. Chem., Int. Ed. 2010, 49,
9322. (c) Furuya, T.; Kamlet, A. S.; Ritter, T. Nature 2011, 473, 470.
(d) Roy, S.; Gregg, B. T.; Gribble, G. W.; Le, V. D.; Roy, S.
Tetrahedron 2011, 67, 2161. (e) Furuya, T.; Ritter, T. J. Synth. Org.
Chem., Jpn. 2011, 69, 48. (f) Amii, H. J. Synth. Org. Chem., Jpn. 2011,
69, 752. (g) Tomashenko, O. A.; Grushin, V. V. Chem. Rev. 2011, 111,
4475.
́
Org. Lett. 2011, 13, 3596. (p) Tomashenko, O. A.; Escudero-Adan, E.
C.; Belmonte, M. M.; Grushin, V. V. Angew. Chem., Int. Ed. 2011, 50,
7655. (q) Zhang, C.-P.; Cai, J.; Zhou, C.-B.; Wang, X.-P.; Zheng, X.;
Gu, Y.-C.; Xiao, J.-C. Chem. Commun. 2011, 47, 9516.
(7) Cu-catalyzed aromatic trifluoromethylation and difluoromethyla-
tion: (a) Oishi, M.; Kondo, H.; Amii, H. Chem. Commun. 2009, 1909.
(b) Kondo, H.; Oishi, M.; Fujikawa, K.; Amii, H. Adv. Synth. Catal.
2011, 353, 1247. (c) Fujikawa, K.; Fujioka, Y.; Kobayashi, A.; Amii, H.
Org. Lett. 2011, 13, 5560.
(8) Recent reports on catalytic aromatic trifluoromethylation:
(a) Grushin, V. V.; Marshall, W. J. J. Am. Chem. Soc. 2006, 128,
4632. (b) Grushin, V. V.; Marshall, W. J. Am. Chem. Soc. 2006, 128,
12644. (c) Ball, N. D.; Kampf, J. W.; Sanford, M. S. J. Am. Chem. Soc.
2010, 132, 2878. (d) Wang, X.; Truesdale, L.; Yu, J.-Q. J. Am. Chem.
Soc. 2010, 132, 3648. (e) Ye, Y.; Ball, N. D.; Kampf, J. W.; Sanford, M.
S. J. Am. Chem. Soc. 2010, 132, 14682. (f) Wiehn, M. S.; Vinogradova,
E. V.; Togni, A. J. Fluorine Chem. 2010, 131, 951. (g) Shimizu, R.;
Egami, H.; Nagi, T.; Chae, J.; Hamashima, Y.; Sodeoka, M.
Tetrahedron Lett. 2010, 51, 5947. (h) Cho, E. J.; Senecal, T. D.;
Kinzel, T.; Zhang, Y.; Watson, D. A.; Buchwald, S. L. Science 2010,
328, 1679. (i) Kino, T.; Nagase, Y.; Ohtsuka, Y.; Yamamoto, K.;
Uraguchi, D.; Tokuhisa, K.; Yamakawa, T. J. Fluorine Chem. 2010, 131,
98. (j) Ball, N. D.; Gary, J. B.; Ye, Y.; Sanford, M. S. J. Am. Chem. Soc.
2011, 133, 7577. (k) Loy, R. N.; Sanford, M. S. Org. Lett. 2011, 13,
2548. (l) Samant, B. S.; Kabalka, G. W. Chem. Commun. 2011, 47,
7236. (m) Mu, X.; Chen, S. J.; Zhen, X. L.; Liu, G. S. Chem.Eur. J.
2011, 17, 6039. (n) Ji, Y.; Brueckl, T.; Baxter, R. D.; Fujiwara, Y.;
Seiple, I. B.; Su, S.; Blackmond, D. G.; Baran, P. S. Proc. Natl. Acad. Sci.
U.S.A. 2011, 108, 14411. (o) Ye, Y.; Lee, S. H.; Sanford, M. S. Org.
Lett. 2011, 13, 5464.
(5) Recent reports on aromatic fluorination: (a) Anbarasan, P.;
Neumann, H.; Beller, M. Angew. Chem., Int. Ed. 2010, 49, 2219.
(b) Yamada, S.; Gavryushin, A.; Knochel, P. Angew. Chem., Int. Ed.
́
2010, 49, 2215. (c) Cazorla, C.; Metay, E.; Andrioletti, B.; Lemaire, M.
Tetrahedron Lett. 2009, 50, 3936. (d) Furuya, T.; Ritter, T. J. Am.
Chem. Soc. 2008, 130, 10060. (e) Watson, D. A.; Su, M.; Teverovskiy,
G.; Zhang, Y.; García-Fortanet, J.; Kinzel, T.; Buchwald, S. L. Science
2009, 325, 1661. (f) Grushin, V. V.; Marshall, W. J. J. Am. Chem. Soc.
2006, 128, 12644. (g) Fors, B. P.; Watson, D. A.; Biscoe, M. R.;
Buchwald, S. L. J. Am. Chem. Soc. 2008, 130, 13552. (h) Barder, T. E.;
Walker, S. D.; Martinelli, J. R.; Buchwald, S. L. J. Am. Chem. Soc. 2005,
127, 4685. (i) Grushin, V. V.; Marshall, W. J. Organometallics 2008, 27,
4825. (j) Hull, K. L.; Anani, W. Q.; Sanford, M. S. J. Am. Chem. Soc.
2006, 128, 7134. (k) Wang, X.; Mei, T.-S.; Yu, J.-Q. J. Am. Chem. Soc.
2009, 131, 7520. (l) Kaspi, A. W.; Yahav-Levi, A.; Goldberg, I.;
Vigalok, A. Inorg. Chem. 2008, 47, 5. (m) Ball, N. D.; Sanford, M. S. J.
(9) (a) Nagajima, K.; Shimizu, I.; Yamamoto, A. Bull. Chem. Soc. Jpn.
1999, 72, 799. (b) Kakino, R.; Shimizu, I.; Yamamoto, A. Bull. Chem.
Soc. Jpn. 2001, 74, 371. (c) Kakino, R.; Yasumi, S.; Shimizu, I.;
Yamamoto, A. Bull. Chem. Soc. Jpn. 2002, 75, 137.
(10) Li, C.-L.; Chen, M.-W.; Zhang, X.-G. J. Fluorine Chem. 2010,
131, 856.
1285
dx.doi.org/10.1021/om201021b | Organometallics 2012, 31, 1281−1286

Organometallics
Article
(11) Reviews on the chemistry of trifluoroacetimidoyl halides:
(a) Uneyama, K. J. Fluorine Chem. 1999, 97, 11. (b) Uneyama, K.;
Amii, H.; Katagiri, T.; Kobayashi, T.; Hosokawa, T. J. Fluorine Chem.
2005, 126, 165.
(12) Tamura, K.; Mizukami, H.; Maeda, K.; Watanabe, H.; Uneyama,
K. J. Org. Chem. 1993, 58, 32.
(13) Uneyama, K.; Watanabe, H. Tetrahedron Lett. 1991, 32, 1459.
(14) Amii, H.; Kohda, M.; Seo, M.; Uneyama, K. Chem. Commun.
2003, 1752.
(15) (a) Watanabe, H.; Hashizume, Y.; Uneyama, K. Tetrahedron
Lett. 1992, 33, 4333. (b) Amii, H.; Kishikawa, Y.; Kageyama, K.;
Uneyama, K. J. Org. Chem. 2000, 65, 3404.
(26) (a) Yamamoto, Y.; Yamazaki, H. Bull. Chem. Soc. Jpn. 1975, 48,
3691. (b) Yu, Y. S.; Angelici, R. J. Organometallics 1983, 2, 1583.
(27) (a) Adams, R. D.; Chodosh, D. F.; Golembeski, N. M. J.
Organomet. Chem. 1977, 139, C39. (b) Alper, H.; Tanaka, M. J.
Organomet. Chem. 1979, 169, C5. (c) Adams, R. D.; Chodosh, D. F.;
Golembeski, N. M.; Weissman, E. C. J. Organomet. Chem. 1979, 172,
251.
(28) (a) Lappert, M. F.; Oliver, A. J. J. Chem. Soc., Chem. Commun.
1972, 274. (b) Lappert, M. F.; Oliver, A. J. J. Chem. Soc., Dalton Trans.
1974, 65. (c) Hitchcock, P. B.; Lappert, M. F.; Mclaughlin, G. M.;
Oliver, A. J. J. Chem. Soc., Dalton Trans. 1974, 68.
(29) Tanaka, M.; Alper, H. J. Organomet. Chem. 1979, 168, 97.
(30) (a) Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508.
(b) Kosugi, M.; Fugami, K. J. Organomet. Chem. 2002, 653, 50.
(31) (a) Kobayashi, T.; Sakakura, T.; Tanaka, M. Tetrahedron Lett.
1985, 26, 3463. (b) Kosugi, M.; Koshiba, M.; Atoh, A.; Sano, H.;
Migita, T. Bull. Chem. Soc. Jpn. 1986, 59, 677.
(16) (a) Abe, H.; Amii, H.; Uneyama, K. Org. Lett. 2001, 3, 313.
(b) Suzuki, A.; Mae, M.; Amii, H.; Uneyama, K. J. Org. Chem. 2004,
69, 5132. (c) Chen, M.-W.; Duan, Y.; Chen, Q.-A.; Wang, D.-S.; Yu,
C.-B.; Zhou, Y.-G. Org. Lett. 2010, 12, 5075.
(17) Isobe, A.; Takagi, J.; Katagiri, T.; Uneyama, K. Org. Lett. 2008,
(32) Examples of polynuclear complexes possessing μ-imidoyl
bridges: (a) Aime, S.; Gobetto, R.; Padovan, F.; Botta, M.;
Rosenberg, E.; Gellert, R. W. Organometallics 1987, 6, 2074.
(b) Day, M.; Hajela, S.; Hardcastle, K. I.; McPhillips, T.; Rosenberg,
E.; Botta, M.; Gobetto, R.; Milone, L.; Osella, D.; Gellert, R. W.
Organometallics 1990, 9, 913.
(33) Brahms, D. L. S.; Dailey, W. P. Chem. Rev. 1996, 96, 1585.
(34) (a) Morandi, B.; Carreira, E. M. Angew. Chem., Int. Ed. 2010, 49,
938. (b) Morandi, B.; Carreira, E. M. Angew. Chem., Int. Ed. 2010, 49,
4294. (c) Morandi, B.; Mariampillai, B.; Carreira, E. M. Angew. Chem.,
Int. Ed. 2011, 50, 1101. (d) Morandi, B.; Cheang, J.; Carreira, E. M.
Org. Lett. 2011, 13, 3080. (e) Morandi, B.; Carreira, E. M. Angew.
Chem., Int. Ed. 2011, 50, 9085.
10, 2657.
(18) Minami, Y.; Kuniyasu, H.; Sanagawa, A.; Kambe, N. Org. Lett.
2010, 12, 3744.
(19) For reviews, see: (a) Yamamoto, Y.; Yamazaki, H. Coord. Chem.
Rev. 1972, 8, 225. (b) Treichel, P. M. Adv. Organomet. Chem. 1973, 11,
21. (c) Shingleton, E.; Oosthuizen, H. E. Adv. Organomet. Chem. 1983,
22, 209. (d) Ito, Y.; Murakami, M. Synlett 1990, 245.
(20) Johnson, M. D.; Tobe, M. L.; Wong, L.-Y. J. Chem. Soc., Chem.
Commun. 1967, 572.
(21) Yamamoto, Y.; Yamazaki, H.; Hagihara, N. Bull. Chem. Soc. Jpn.
1968, 41, 532.
(22) (a) Otuka, S.; Nakamura, A.; Yoshida, T. J. Am. Chem. Soc. 1969,
91, 7196. (b) Yamamoto, Y.; Yamazaki, H. Bull. Chem. Soc. Jpn. 1970,
43, 2653. (c) Yamamoto, Y.; Yamazaki, H. Bull. Chem. Soc. Jpn. 1970,
43, 3634. (d) Otsuka, S.; Naruto, M.; Yoshida, T.; Nakamura, A. J.
Chem. Soc., Chem. Commun. 1972, 396. (e) Yamamoto, Y.; Yamazaki,
H. Inorg. Chem. 1972, 11, 211. (f) Otsuka, S.; Nakamura, A.; Yoshida,
T.; Naruto, M.; Ataka, K. J. Am. Chem. Soc. 1973, 95, 3180.
(g) Yamamoto, Y.; Yamazaki, H. Inorg. Chem. 1977, 16, 3182.
(23) (a) Yamamoto, Y.; Yamazaki, H.; Hagihara, N. J. Organomet.
Chem. 1969, 18, 189. (b) Otuka, S.; Nakamura, A.; Yoshida, T. J. Am.
Chem. Soc. 1969, 91, 7196. (c) Yamamoto, Y.; Yamazaki, H. Bull.
Chem. Soc. Jpn. 1970, 43, 2653. (d) Yamamoto, Y.; Yamazaki, H. Bull.
Chem. Soc. Jpn. 1970, 43, 3634. (e) Treichel, P. M.; Hess, R. W. J. Am.
Chem. Soc. 1970, 92, 4731. (f) Kajimoto, T.; Takahashi, H.; Tsuji, J. J.
Organomet. Chem. 1970, 23, 275. (g) Yamamoto, Y.; Yamazaki, H. J.
Organomet. Chem. 1970, 24, 717. (h) Crociani, B.; Richards, R. L. J.
Chem. Soc., Chem. Commun. 1973, 127. (i) Yamamoto, Y.; Yamazaki,
H. Inorg. Chem. 1974, 13, 438. (j) Yamamoto, Y.; Yamazaki, H. Inorg.
Chem. 1974, 13, 2145. (k) Crociani, B.; Nicolini, M.; Richards, R. L. J.
Organomet. Chem. 1975, 101, C1. (l) Clark, R. J. H.; Stockwell, J. A.;
Wilkins, J. D. J. Chem. Soc., Dalton Trans. 1976, 120. (m) Adams, R.
D.; Chodosh, D. F. J. Am. Chem. Soc. 1977, 99, 6544. (n) Adams, R.
D.; Chodosh, D. F. Inorg. Chem. 1978, 17, 41. (o) Roper, W. R.;
Taylor, G. E.; Waters, J. M.; Wright, L. J. J. Organomet. Chem. 1978,
157, C27. (p) Dormond, A.; Dahchour, A. J. Organomet. Chem. 1980,
(35) Buron, C.; Gornitzka, H.; Romanenko, V.; Bertrand, G. Science
2000, 288, 834.
(36) (a) Moss, R. A.; Zdrojewski, T.; Ho, G. J. Chem. Soc., Chem.
Commun. 1991, 946. (b) Moss, R. A. Acc. Chem. Res. 2006, 39, 267.
(37) (a) Moss, R. A.; Wang, L.; Krogh-Jespersen, K. J. Am. Chem. Soc.
2009, 131, 2128. (b) Lu, Z.; Moss, R. A.; Sauers, R. R.; Warmuth, R.
Org. Lett. 2009, 11, 3866. (c) Moss, R. A.; Zhang, M.; Krogh-
Jespersen, K. Org. Lett. 2010, 12, 3476. (d) Moss, R. A.; Shen, Y.;
Wang, L.; Krogh-Jespersen, K. Org. Lett. 2011, 13, 4752.
(38) (a) Kanoh, N.; Kumashiro, S.; Simizu, S.; Kondoh, Y.;
Hatakeyama, S.; Tashiro, H.; Osada, H. Angew. Chem., Int. Ed. 2003,
42, 5584. (b) Kanoh, N.; Asami, A.; Kawatani, M.; Honda, K.;
Kumashiro, S.; Takayama, H.; Simizu, S.; Amemiya, T.; Kondoh, Y.;
Hatakeyama, S.; Tsuganezawa, K.; Utata, R.; Tanaka, A.; Yokoyama, S.;
Tashiro, H.; Osada, H. Chem.Asian J. 2006, 1, 789. (c) Kanoh, N.;
Nakamura, T.; Honda, K.; Yamakoshi, H.; Iwabuchi, Y.; Osada, H.
Tetrahedron 2008, 64, 5692.
(39) (a) Maitlis, P. M.; Espinet, P.; Russell, M. J. H. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon: Oxford, U. K., 1982; Vol. 6, pp 292−299. (b) Dixon,
K. R.; Dixon, A. C. In Comprehensive Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U. K.,
1995; Vol. 9, pp 216−219.
(40) Treichel, P. M.; Benedict, J. J.; Hess, R. W.; Stenson, J. P. J.
Chem. Soc., Chem. Commun. 1970, 1627.
193, 321. (q) Uson
G.; Sheldrich, G. M. J. Chem. Soc., Dalton Trans. 1982, 2389. (r) Uson
R.; Fornies, J.; Espinet, P.; Garcia, A.; Foces-Foces, C.; Cano, F. H. J.
Organomet. Chem. 1985, 282, C35. (s) Onitsuka, K.; Yanai, K.; Takei,
F.; Joh, T.; Takahashi, S. Organometallics 1994, 13, 3862. (t) Kayaki,
Y.; Shimizu, I.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1997, 70, 917.
(24) (a) Treichel, P. M.; Stenson, J. P. Inorg. Chem. 1969, 8, 2563.
(b) Crociani, B.; Boschi, T.; Nicolini, M. J. Organomet. Chem. 1971, 33,
C81. (c) Crociani, B.; Nicolini, M.; Richards, R. L. J. Organomet. Chem.
1976, 104, 259.
́ ́
, R.; Fornies, J.; Espinet, P.; Lalinde, E.; Jones, P.
́
,
(41) (a) Crociani, B.; Boschi, T. J. Organomet. Chem. 1970, 24, C1.
(b) Crociani, B.; Nicolini, M.; Boschi, T. J. Organomet. Chem. 1978,
154, 65. (c) Crociani, B.; Nicolini, M.; Richards, R. L. J. Organomet.
Chem. 1976, 104, 259. (d) Crociani, B. Inorg. Chim. Acta 1977, 23, L1.
(42) (a) Lappert, M. F.; Oliver, A. J. J. Chem. Soc., Chem. Commun.
1972, 274. (b) Lappert, M. F.; Oliver, A. J. J. Chem. Soc., Dalton Trans.
1974, 65.
́
(25) (a) King, R. B.; Pannell, K. H. J. Am. Chem. Soc. 1968, 90, 3984.
(b) Bland, W. J.; Kemmitt, R. D. W.; Nowell, I. W.; Russell, D. R.
Chem. Commun. 1968, 1065. (c) Bland, W. J.; Kemmitt, R. D. W.;
Moore, R. D. J. Chem. Soc., Dalton Trans. 1973, 1292. (d) Green, M.;
Taylor, S. H.; Daly, J. J.; Sanz, F. J. Chem. Soc., Chem. Commun. 1974,
361.
1286
dx.doi.org/10.1021/om201021b | Organometallics 2012, 31, 1281−1286