Regioselective CH bond activation on stabilized nitrogen ylides promoted by Pd(II) complexes: Scope and limitations

Article abstract of DOI:10.1021/om201001c

The orthopalladation of N-ylides [H_xC_yN-CHC-(O)Ar] (H_xC_yN = pyridine, benzylamine, imidazole, aniline, and phenylpyridine; Ar = aryl) has been studied. The incorporation of the Pd atom to these substrates is regioselective, since the orthopalladation is produced, in most of the cases, only at the aryl ring of the benzoyl group with concomitant C-bonding of the Nylide. The X-ray structure of one representative example is reported. Factors governing the observed orientation are discussed, because this regioselectivity is worthy of note, considering the deactivating nature of the carbonyl group. Two exceptions to the general trend have been observed. The first one is the double metalation of the ylide [PhMe₂NCHC(O)Ph], which incorporates one Pd at each Ph. The second one is the palladation of the phenylpyridine derivative, which occurs at the pyridinic 2-phenyl ring and produces a six-membered palladacycle.

Full text of DOI:10.1021/om201001c

Article
pubs.acs.org/Organometallics
Regioselective CH Bond Activation on Stabilized Nitrogen Ylides
Promoted by Pd(II) Complexes: Scope and Limitations
Loreto Grande, Elena Serrano, Luciano Cuesta, and Esteban P. Urriolabeitia*
́ ́
Instituto de Síntesis Química y Catalisis Homogenea, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain
S
* Supporting Information
ABSTRACT: The orthopalladation of N-ylides [HxCyN−CHC-
(O)Ar] (HxCyN = pyridine, benzylamine, imidazole, aniline, and
phenylpyridine; Ar = aryl) has been studied. The incorporation of
the Pd atom to these substrates is regioselective, since the
orthopalladation is produced, in most of the cases, only at the aryl
ring of the benzoyl group with concomitant C-bonding of the N-
ylide. The X-ray structure of one representative example is
reported. Factors governing the observed orientation are
discussed, because this regioselectivity is worthy of note,
considering the deactivating nature of the carbonyl group. Two
exceptions to the general trend have been observed. The first one
is the double metalation of the ylide [PhMe2NCHC(O)Ph],
which incorporates one Pd at each Ph. The second one is the
palladation of the phenylpyridine derivative, which occurs at the pyridinic 2-phenyl ring and produces a six-membered
palladacycle.
functional groups available confers a really great synthetic
potential to this methodology.
INTRODUCTION
■
The functionalization of organic molecules through a CH bond
activation process promoted by transition metals is, at present,
one of the most active research areas in chemistry.1 This
strategy provides alternative methodologies and improved tools
to develop more concise and straightforward synthetic routes
when compared with the conventional preparative organic
procedures.1 The advantages of the CH activation methodology
are evident in terms of economy and waste reduction. However,
because of the ubiquity of the C−H bond in organic substrates,
the selectivity of the activation process is a critical point, and
synthetic strategies must be developed to obtain the best
performance in this challenging task. One of the most
successful solutions is the ortho functionalization, which is
easily achieved in aromatic substrates through the introduction
of a directing group on the starting substrate.2 This strategy
results in the formation of orthometalated complexes, which are
valuable tools in stoichiometric and/or catalytic processes.1,3−17
Among different metals, palladium and, therefore, cyclo-
palladated complexes,4 have proved to be highly efficient
reagents in metal-mediated organic synthesis.3−17 The
versatility of this methodology is clearly reflected by the large
variety of molecules that have been functionalized at the ortho
position of the directing group, and by the wide scope of
functional groups that can be introduced regiospecifically into a
given substrate, resulting in the formation of C−C, C−O, C−
N, C−S, C−P, or C−X (X = halogen) bonds.5−17 The
combination of the regioselective metalation by the directing
group effect, the wide scope of substrates, and the plethora of
On the other hand, the chemistry of ylides is still a
fascinating research field, since they are versatile ligands toward
transition metals and show exciting properties and applica-
tions.18−25 We are interested in the chemical behavior of ylides
and related species, such as iminophosphoranes, and a
significant part of our recent research work has been centered
on these substrates,26 including specific studies on CH bond
activations and functionalization processes.27 One of our most
significant results is the regioselective palladation of keto-
stabilized iminophosphoranes [R3PNC(O)Ar], that is, those
containing an arylamide group.27d,e,i,j The incorporation of the
Pd is produced exclusively at the ortho position of the
arylamide ring, as it is shown in Figure 1 (left). DFT
calculations performed on this system showed that the reaction
is kinetically controlled27i and that the presence of the carbonyl
group is critical since, in its absence, the regioselectivity is
reversed (Figure 1 right). Obviously, the regioselective
palladation of an aromatic ring when several options are
possible is of considerable interest, since it would allow for the
selective incorporation of a given functional group.27j
On the other hand, the comparison of keto-stabilized
iminophosphoranes with the homologous keto-stabilized P-
ylides reflects a divergent behavior of the two substrates, as
shown in Figure 2: whereas the orthopalladation of the
iminophosphoranes is produced at the benzamide ring, that of
Received: October 17, 2011
Published: December 23, 2011
© 2011 American Chemical Society
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Figure 1. Iminophosphoranes and observed regioselective orthopalladations.27d,e,i,j
Figure 2. Divergent behavior of iminophosphoranes and ylides toward orthopalladation.27d
the P-ylides is produced at the P-aryl ring, with full
regioselectivity.27d
derivatives of pyridine (labeled a−e), N,N-dimethylbenzyl-
amine (f), N-methylimidazole (g), N,N-dimethylaniline (h),
and 2-phenylpyridine (i).
Therefore, it is clear that not only is the carbonyl group
important (stabilized vs nonstabilized substrates) but also the
nature of the donor group (N vs CH) seems to be critical. Now
we want to check if it is possible to extend these observations to
other competitive carbonylic substrates, aiming to achieve
regioselective functionalizations. In particular, this contribution
is focused on the regioselective cyclopalladation of N-ylides
derived from pyridine, benzylamine, imidazole, aniline, and
phenylpyridine. We have studied N-ylides with benzoyl
stabilizing substituents (N-phenacylpyridinium ylides), since
they have attracted recently a renewed interest as starting
materials of high-added-value products.28 Gratifyingly, we
found that N-ylides, such as [HxCyN−CHC(O)Ar], where
HxCyN represents one amine or one heterocycle and Ar is an
aryl group, can be palladated regioselectively at the benzoyl ring
ortho to the carbonyl group, almost regardless of the nature of
the amine, the heterocycle, and/or the aryl group. Here, we
report the results obtained on this type of chemistry.
The N-ylides have been synthesized in two steps, as a general
procedure. The first one involves the synthesis of the “-onium”
salts (1) by reaction of the corresponding bromoketone with
the appropriate amine29a or, alternatively, following the method
of King.29b In the second step, the ylides are prepared (except
2e) by deprotonation of the corresponding “onium” salts, using
K2CO3 or NaOH as a base, in water at 0 °C.29c,d In some cases,
the ylides are generated and reacted “in situ”, because they
could not be isolated. All ylides examined in this work have
been prepared previously,29 and we have employed known or
slightly modified procedures for their preparation.
Orthopalladation of Pyridinium N-Ylides. The N-ylides
were reacted with a classical palladating reagent as Pd(OAc)2,
and the outcome of the reaction was examined in detail for each
case. The reaction conditions were optimized for each substrate
analyzed. For the sake of simplicity and convenience, instead of
fully characterizing the complexes with presumably acetate
bridges, the resulting orthopalladated complexes were isolated
and characterized as dimeric structures with chloride bridges
(4a−4i), and/or as monomeric complexes containing an acac
ligand (5a−5i).
RESULTS AND DISCUSSION
■
Synthesis of the N-Ylides. We have performed the
synthesis of five families of N-ylides (Chart 1), namely,
The first set of compounds studied were N-ylides derived of
pyridine (2a−2d). The orthometalation step was carried out by
reaction of the ylide with Pd(OAc)2 in dry toluene at
temperatures in the range of 25−60 °C (see the Experimental
Section), followed by acetate/chloride metathesis by reaction
with LiCl in methanol. In this way, the complexes 4a−4d were
isolated in good yield as air-stable, yellow solids and
characterized as binuclear species with the classical chloride
bridging structure (Scheme 1). In some cases, the solubility of
4a−4d avoids proper 13C NMR measurements. Therefore,
complexes 4a−4d have been transformed into the more soluble
acac derivatives 5a−5d by metathesis of the chloride bridges by
the chelate acac ligand. 4a−4d were reacted with Tl(acac)
(molar ratio of 1:2) in CH2Cl2 at 25 °C (Scheme 1), affording
5a−5d as yellow or pale yellow solids, which were fully
characterized by NMR, mass spectrometry, IR, and micro-
analysis.
Chart 1. N-Phenacyl Ylides Studied in This Work
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the Pd center is well documented for P-ylides,20,26a,b but it has
been very rarely characterized for N-ylides,18l,m,30 probably due
to the higher nucleophilic character of the Cα atom in these N-
ylides, compared with that of the oxygen. The incorporation of
the Pd center to the pyridine ring, directed by the N-ylidic
moiety, has recently been invoked by Hu et al. in order to
explain the catalytic arylation on N-phenacylpyridinium
derivatives.28d These authors provide an explanation based on
the HOMO location on the ylide species, which resides on the
ortho- and para-carbons of the pyridine group, and suggest that
the ylides are the true reactive species. Surprisingly, our starting
materials are N-phenacylpyridinium ylides too, and, in our
hands, we have detected incorporation of the Pd atom only at
the benzoyl ring. This different reactivity is really similar to that
found in closely related species, such as N-iminopyridinium
ylides [H5C5N-NC(O)Ph]. The contribution of Dias et al.28g,h
about the orthopalladation of these ligands reports the
regioselective incorporation of the Pd center to the ortho
positions of the benzamide fragment, directed by its N-bonding
to the iminic nitrogen. However, recent work of Charette et al.
describes with great detail the catalytic arylation28a and
alkenylation28e of the ortho positions of the pyridine moiety
of the same N-iminopyridinium ylides, where the authors
suggest that the O-bonding of the carbonyl oxygen assists the
orientation. Therefore, we have examples of the two
orientations in two different scenarios.
Probably, the different reaction conditions (in our case, there
is not an excess of K2CO3 during the reaction, nor presence of
phosphine or aryl bromide)28d and, therefore, the different
reaction mechanisms could account for this opposite
regioselectivity. In the catalytic process, it is reasonable to
assume28e that the reaction starts with the reduction of the Pd
salt [Pd(OAc)2] to a Pd(0) species due to the action of the
phosphine and that this intermediate adds oxidatively the aryl
bromide, giving an (aryl)(bromide)−Pd(II) complex, presum-
ably stabilized by additional coordination of the phosphine.
This complex could be responsible for the interaction with the
N-phenacylpyridinium derivatives, and it is, at this point, where
the CH bond activation should be produced. The Pd-
containing species that interacts with the ylide in that case28e
(an electron-rich aryl-Pd species) and in our case (the very
electrophilic Pd(OAc)2 complex) are clearly quite different,
probably this difference accounting for the different reaction
outcomes. Additionally, in our case, the observed selectivity can
be explained attending to geometrical factors. The higher
affinity of the electrophilic Pd center for the ylidic carbon atom
over the carbonylic oxygen governs the coordination step.
Upon the formation of the intermediary species by palladium
coordination to the ylidic carbon, it is obvious that the
activation of the ortho proton of the benzoyl group is favored
geometrically, because it would drive the formation of a five-
membered metallacycle, whereas the C−H activation over the
pyridine ring would form a highly unstable cycle of four
members.
Scheme 1. Synthesis of Complexes 4a−4d and 5a−5d
The analysis of the IR spectra is a very practical tool to
evaluate the outcome of these reactions; in particular, the shifts
observed for the carbonyl groups are very good indications of
the reaction pattern of these systems. In the ylides used as
starting materials (2a−2d),29 the IR spectra display a very
strong absorption in the range of 1559−1599 cm−1 assigned to
the carbonyl group, whose positions reflect the presence of
electronic conjugation of the negative charge into the ketonic
double bond. In the resulting orthopalladated complexes (4a−
4d), the bands due to the CO moiety moved to 1647−1668
cm−1, indicating that the conjugation with the carbonyl group
has been broken, and, therefore, suggesting that the ylidic
carbon is coordinated to the palladium. This kind of
coordination is expected to drive the C−H activation process
to the benzoyl ring, a regiochemistry that is clearly confirmed
by the analysis of the NMR data.
In the 1H NMR spectra of 4a−4d are observed the
disappearances of one of the aromatic protons of the benzoyl
group, while the pyridine set of signals remains virtually
unaltered. The NMR data also confirmed the σ coordination of
the ylidic carbon, which is reflected in the significant upfield
shift showed by the signal of the carbon of the ylide unit (for
example, from 98.48 to 81.69 ppm for ylide d), reflecting the
change in the hybridization of sp2 to sp3 upon coordination to
the Pd center. Complexes 5a−5d were also characterized by
NMR, mass spectrometry, IR, and microanalysis. All data
indicate that the ylide remains cyclopalladated after the
chloride/acac metathesis, confirming the stability of the five-
membered metallacyclic ring. In addition, the structure of 5c
was analyzed by X-ray diffraction studies (see below).
These results show that the palladation of the benzoyl ring is
totally regioselective, since we have not detected signals due to
other isomers in the NMR spectra. To achieve this metalation,
it is very likely that the ylidic Cα atom acts as a directing group
with concomitant formation of a five-membered ring. However,
in principle, there is a second option (not observed in our
case), namely, the cyclometalation of the ortho positions of the
pyridine ring, which seems to be directed by interaction of the
Pd with the carbonyl oxygen,28 and formation of a six-
membered ring. The coordination of the carbonyl oxygen to
Although the deprotonation of the pyridinium salts 1a−1d
has been an efficient and practical method for the synthesis of
the ylides 2a−2d, it resulted to be not viable for the derivative
1e, which contains a methyl group ortho to the quaternary
nitrogen of the pyridinium ring. Apparently, the base employed
can abstract one of these relatively acidic methyl protons,
generating a carbanion able to attack the ketonic carbon, and
leading to the formation of the indolizine 3 by means of an
intramolecular aldol condensation (see Scheme 2). Although
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Scheme 2. Unexpected Synthesis of Indolizine 329n
the two groups would be expected. This difference has to be
reflected in very different chemical shifts, and we have not
1
observed this difference in the H, nor in the 13C, NMR
1
spectra. In fact, the H NMR spectrum shows accidentally
isochronous N-methyl groups, whereas the 13C{1H} NMR
spectrum shows very similar chemical shifts for the two N-
methyl groups (50.23 and 50.49 ppm). These facts strongly
suggest that the palladation has been produced at the benzoyl
ring. Probably, the different sizes of the resulting palladacycles
(five- vs six-membered) are critical in order to achieve a given
orientation.
The following substrate evaluated was a derivative of N-
methylimidazole (1g). The reactions of the imidazolium salt 1g
with diverse bases at different temperatures always yielded
decomposition products, without traces of the ylide species. In
this case, the ylide seems to be too reactive, precluding its
isolation and characterization. However, the imidazolium salt
1g reacts cleanly with Pd(OAc)2 at 25 °C during 2 h in CH2Cl2,
affording the desired orthopalladated complex 4g (Scheme 4).
unexpected, this synthesis displays considerable interest due to
the multiple applications presented by this kind of molecule,29n
for example, in medicinal chemistry or in material science.
However, and despite this potential interest, we considered that
the synthesis of novel indolizines is not the topic of this article,
and we have not continued with this type of reaction.
Orthopalladation of N-Ylides Derived from other N
Sources. The next ligand studied was the ylide 2f, which is
analogous to the derivatives 2a−2d but contains a N,N-
dimethylbenzylamine group instead of the pyridine moiety. The
reaction of the ylide 2f with Pd(OAc)2 in toluene at 60 °C
during 2 h yielded the presumably orthometalated complex
with acetate bridges, which is treated with LiCl in methanol,
affording complex 4f (Scheme 3). Although the elemental
Scheme 4. Synthesis of Complex 5g
Scheme 3. Synthesis of Complexes 4f and 5f
analysis and mass spectrometry of 4f clearly indicated the
formation of a typical structure of an orthometalated complex
with chloride bridging ligands, this complex resulted to be
poorly soluble in all the common organic solvents, precluding a
total characterization. A simple derivatization to the mono-
nuclear species 5f by treatment with Tl(acac) allowed for a
complete analysis of its structure.
In this reaction, probably, the ylide is generated “in situ” by
intermediacy of the acetates present in the reaction media,
which likely are capable of playing the role of the base. The
intermediate with chloride bridges 4g was poorly soluble in the
common organic solvents, avoiding its full characterization.
Therefore, 4g was transformed by the typical strategy into the
mononuclear complex 5g, containing an acac ligand, whose
The IR band assigned to the carbonyl group of the ylide unit
appears at 1647 cm−1, in the range expected for a complex with
the ylidic carbon σ-coordinated to palladium and with the CO
1
1
group nonbonded to the metallic fragment. In the H NMR,
structure was inferred from the NMR data. In the H NMR
the ylidic proton and the NMe2 group undergo a considerable
shift to lower fields (from 4.24 and 2.34 ppm in 2f, to 5.21 ppm
and 3.26 ppm in 5f, respectively), and the initially equivalent
protons of the CH2N group are now diastereotopic and appear
as a well-resolved AB spin system. Both facts are a consequence
of the C coordination to the metallic center. A singlet at 3.26
ppm show that the two N-methyl groups behave as equivalent
in the NMR time scale. The Cα-bonding displays two potential
sites for the posterior orthometalation, one is the CH bond
activation of the benzoyl ring to afford a metallacycle of five
members, and the other is the cyclometalation of the phenyl
ring of the dimethylbenzylamine moiety generating a six-
membered cycle. If palladation were produced at the benzylic
moiety, the two N-methyl groups would be located on a six-
membered metallacycle, adjacent to the asymmetric ylidic
carbon, and a large difference in the chemical environment of
spectrum, the most informative signals are two different sets of
signals for the aromatic fragments, where three aromatic
protons are easily assigned to the N-methyl imidazole aromatic
ring, and only four protons, all of them nonequivalent, are
attributed to the benzoyl ring. These data clearly indicate that
the benzoyl ring has been cyclometalated, the heterocyclic unit
remaining unaltered. It is also remarkable in this spectrum that
the initial CH2N group of the ammonium salt has been
transformed into a CHN unit, evidenced by the presence of a
1
singlet at 6.18 ppm in the H NMR, which integrates by only
one proton, indicating a σ coordination of the ylidic carbon to
the metallic center. This kind of coordination is supported by
the fact that, in the 13C NMR, the signal assigned to the ylidic
carbon (64.50 ppm) resonates within the typical range of this
kind of system. In the IR spectrum, the CO group appears at
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1662 cm−1, in the expected region for C-bonded keto-stabilized
ylides.
complex, which is the result of two independent orthopallada-
tions. In 5h2, in addition to the cyclometalated benzoyl ring,
there is another metallacycle of seven members, resulting from
the C−H activation of the aromatic ring of the N,N-
dimethylaniline. This second orthometalation process is
assisted by the carbonyl group, which behaves as a directing
group, coordinating a second palladium atom and directing the
C−H activation process to the N,N-dimethylamine moiety.
This is the only case we have found where the carbonyl group
behaves as a directing group. A similar bis-orthopalladated
dinuclear complex has been characterized in P-ylides.27d It
seems reasonable to propose that 5h2 is formed from 5h1,
which is the species initially generated. This idea is supported
by the fact that reactions carried out at room temperature in
CH2Cl2 afforded mixtures in which 5h1 is the major
compound. For example, after 1.5 h of reaction time, the
obtained molar ratio of 5h1/5h2 is 1.7/1. However, analogous
reactions carried out in toluene, but with longer reaction times
or higher temperatures, did not show a full conversion to the
derivative 5h2, and severe decomposition was observed instead.
The structures depicted for 5h1 and 5h2 in Scheme 5 are
based on the NMR data. The unusual double metalation
Considering that coordination through the ylidic carbon
seems to be preferred, the regiochemistry observed is
predictable. The palladation of the imidazolium ring directed
by the C-bonding of the ylide, either at C2 or at C4, seems
complicated since it will lead to a cycle of four members.
However, the incorporation of the Pd center to the
imidazolium ring could be achieved, in principle, in the case
of the O-bonding of the ylide since a six-membered palladacycle
would be formed, as it has been postulated in the case of the
pyridinium salts. We have not detected the presence of other
isomers so, once again, it seems that the O-bonding of the ylide
is not favored in these reaction conditions and that the C-
bonding is the effective directing group of the ylide unit.
The behavior of the ylide derived from N,N-dimethylaniline
h has also been examined. Analogously to what is observed in
the case of the N-methylimidazole g, all efforts to isolate the
ylide failed, and orthopalladation was achieved by “in situ”
generation of the ylide. The reaction between the anilinium salt
1h with Pd(OAc)2 in toluene at 65 °C resulted to be an
efficient strategy for the synthesis of orthometalated N-ylides
(Scheme 5). In this case, the expected chloride-bridging
1
undergone by 5h2 is inferred from the H NMR spectrum,
where the lack of one proton on each aromatic ring is clearly
observed. The 13C NMR displays, in addition to the σ-bonded
ylidic carbon, signals attributable to two different σ Pd−C
bonds, confirming the presence of two cyclopalladated arene
rings. On the other hand, the O-bonding of the ylide can be
easily inferred from the shift to low energies of the IR
absorption due to the νCO stretch (1555 cm−1), and from the
observation of the deshielding of the signal due to the carbonyl
group, now appearing at 207.06 ppm. The existence of two
nonequivalent acac ligands, as judged from the NMR and IR
data, is another evidence of the formation of the bimetallic
complex.
Scheme 5. Synthesis of Complexes 5h1 and 5h2
Finally, we examined the reactivity of the N-ylide 2i, which
contains a phenylpyridine group. In this case, the stable ylide 2i
was isolated and fully characterized. The reaction of 2i with
Pd(OAc)2 in CH2Cl2 at 25 °C for 4 h afforded a new
cyclopalladated complex 4i (Scheme 6), which showed a
Scheme 6. Synthesis of Complexes 4i and 5i
complex 4h could not be isolated, although one-pot
derivatization to the respective mononuclear species containing
acac ligands allowed for the synthesis of well-defined species 5h
and a full understanding of the outcome of the reaction.
Conversely to the other examples described above, this
reaction was not totally selective and afforded a mixture of the
cyclopalladated complexes 5h1 and 5h2 in a molar ratio of 1:5
in the aforementioned conditions. The minor compound (5h1)
displays a structure similar to the other examples described up
to here, in which a palladacycle of five members has been
formed by palladation of the benzoyl ring directed by the ylidic
unit. However, the major compound (5h2) is a bimetallic
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correct elemental analysis and a very low solubility in common
organic solvents. Compound 4i was derivatized to the species
5i, containing a chelate acac ligand, to perform the appropriate
characterization (Scheme 6).
In this system, there are three potential positions for
orthometalation: if the ylidic carbon behaves as a directing
group, both the benzoyl ring and the phenyl ring are accessible,
and also the pyridine is able to being activated if the carbonyl
group orientates the orthometalation. The analysis of the NMR
data revealed that only one of the three aromatic rings has been
activated selectively, as judged by the lack of only one aromatic
proton. The IR indicates that the ketone group was not bonded
to the Pd center, since the νCO absorption appears at 1650
cm−1. This fact suggests that the ylidic carbon is playing the role
of a directing group and, therefore, causing the activation of the
benzoyl group or the phenyl ring. The 1H−13C HMBC
spectrum clearly revealed that the benzoyl ring was not
activated, because the carbonyl carbon shows a clear correlation
with the two equivalent ortho protons of the C6H5 moiety
nonmetalated. This observation indicates that the C−H
activation has taken place over the phenyl ring of the
phenylpyridine unit, leading to the formation of the complex
5i. A full assignation of the structure was achieved by a
combination of COSY, 1D-NOESY, HSQC, and HMBC
spectra, confirming the connectivity inferred previously and
depicted in Scheme 6.
Conversely to all the syntheses discussed up to here, the
benzoyl ring remains intact, the orthometalation taking place
over the phenyl group of the phenylpyridine moiety selectively.
This regioselective C−H activation led to the formation of a
six-membered ring, instead of the anticipated formation of a
palladacycle of five members resulting from the activation of the
benzoyl group. In this particular case, the interpretation of the
regiochemistry observed is a challenging task, and probably a
delicate balance between electronic and geometric factors
seems to be operative. One key to understanding this
unexpected reactivity could be the enhanced acidity of the
phenyl protons due to the strong electron-withdrawing ability
of the quaternary pyridinium salt, in similar way as observed
with the dimethylaniline system. Also, geometrical factors can
be important, because it is interesting to note that the
metallacycle formed is immersed into a tricyclic system,
which makes the evaluation of its relative stability difficult.
X-ray Crystal Structure of 5c. A molecular drawing of
compound 5c is shown in Figure 3. The structure shows clearly
that the Pd atom has been incorporated to the benzoyl
fragment and that the ylide fragment is C-bonded. Therefore,
the Pd atom lies in a slightly distorted square-planar
environment and is surrounded, additionally, by the oxygen
atoms of the chelating acac ligand. The Pd−C(6) bond distance
[1.964(2) Å] is identical, within experimental error, to those
found in related benzoyl or benzamide systems,27d and the Pd−
C(13) bond distance [2.022(3) Å] falls in the usual range of
distances found for this type of bonds.26,27 Interestingly, the
bond distance of Pd(1)−O(3) [2.076(2) Å] is slightly longer
than the bond distance of Pd(1)−O(2) [2.060(2) Å], reflecting
the higher trans influence of the orthometalated carbon versus
the ylidic carbon. Other internal parameters are as expected.
Figure 3. Molecular structure of complex 5c. Ellipsoids of non-
hydrogen atoms have been drawn at 50% probability. Selected bond
distances (Å) and angles (deg): Pd(1)−C(6) 1.964(2), Pd(1)−C(13)
2.022(3), Pd(1)−O(2) 2.060(2), Pd(1)−O(3) 2.076(2), N(1)−
C(13) 1.476(3), C(12)−C(13) 1.509(3), O(1)−C(12) 1.222(3),
C(7)−C(12) 1.480(3); C(6)−Pd(1)−C(13) 80.92(10), C(6)−
Pd(1)−O(2) 92.53(8), C(13)−Pd(1)−O(2) 173.17(8), C(6)−
Pd(1)−O(3) 174.94(9), C(13)−Pd(1)−O(3) 95.17(8), O(2)−
Pd(1)−O(3) 91.25(7), O(1)−C(12)−C(7) 126.8(2), O(1)−
C(12)−C(13) 123.6(2), C(7)−C(12)−C(13) 109.4(2), N(1)−
C(13)−C(12) 111.9(2), N(1)−C(13)−Pd(1) 114.27(17), C(12)−
C(13)−Pd(1) 106.46(15).
phenylpyridine. The incorporation of the Pd atom to these
substrates is, in most of the cases, regioselective, since the
orthopalladation is produced only at the aryl ring of the benzoyl
group, directed by the coordination of the ylidic Cα carbon,
and favoring the formation of five-membered rings over other
ring sizes. Two exceptions to the general trend have been
observed. One is the double metalation of the ylide
[PhNMe2CHC(O)Ph], being the first metalation C-directed
and the second one directed by the carbonyl oxygen. The
second one is more intriguing, because the palladation of the
phenylpyridine derivative occurs at the pyridinic 2-phenyl ring
and produces selectively a six-membered palladacycle. These
results show that the nucleophilicity of the ylidic Cα and the
ring size are not the only parameters governing the selectivity
and that other geometric, steric, and electronic factors have to
be taken into account.
EXPERIMENTAL SECTION
■
General Methods. Solvents were dried and distilled using
standard procedures before use. Elemental analyses (CHN) were
carried out on a PerkinElmer 2400-B microanalyser. Infrared spectra
(4000−380 cm−1) were recorded on a PerkinElmer Spectrum One IR
spectrophotometer. 1H and 13C NMR spectra were recorded in
CDCl3, DMSO-d6, or CD2Cl2 solutions at 25 °C on Bruker AV300
1
and AV400 spectrometers (δ in parts per million, J in hertz) at H
operating frequencies of 300.13 and 400.13 MHz, respectively. 1H and
13C spectra were referenced using the solvent signal as an internal
standard. ESI+ mass spectra were recorded using an Esquire 3000 ion-
trap mass spectrometer (Bruker Daltonic GmbH) equipped with a
standard ESI/APCI source. Samples were introduced by direct
infusion with a syringe pump. Nitrogen served as both the nebulizer
gas and the dry gas. The mass spectra (MALDI+) were recorded from
CHCl3 solutions on a MALDI-TOF Microflex (Bruker) spectrometer
(DCTB as matrix). Ylides 2a,29d,e 2b,29f 2c,29g,h 2d,29a 2f,29i,j 2g,29k,l
2h,29i and 2i28e,29m were synthesized according to published methods.
CONCLUSION
■
In summary, we have described the syntheses of several
orthometalated complexes derived from N-ylides, in particular,
derivatives of pyridine, benzylamine, imidazole, aniline, and
399
dx.doi.org/10.1021/om201001c | Organometallics 2012, 31, 394−404

Organometallics
Article
Synthesis of 7-Methyl-2-phenylindolicine (3).29n 1e (0.602 g,
1.96 mmol) was reacted with K2CO3 (1.05 g, 8.3 mmol) in H2O (5
mL) to give 3 as an orange oil in 96% yield. MS (ESI+) [m/z, (%)]:
MeOH (20 mL) and treated with LiCl (0.084 g, 1.97 mmol). The
resulting mixture was stirred at room temperature, and after some
minutes, 4f precipitated as a yellow solid. Obtained: 0.213 g (55%
yield). Anal. Calcd for C34H36Cl2N2O2Pd2 (788.41): C, 51.80; H, 4.60;
N, 3.55. Found: C, 51.40; H, 4.94; N, 4.02. MS (MALDI+) [m/z,
(%)]: 753.1 (45%) [M − Cl]+. IR: ν = 1648 (νCO) cm−1. NMR: 4f
could not be fully characterized due to its insolubility in common
organic solvents.
1
207.8 (100%) [M]+. H NMR (CDCl3): δ 3.75 (s, 3H, CH3), 6.20
(dd, 1H, H6, 3JHH = 7.2, 4JHH = 1.6), 6.46 (s, 1H, H1), 7.00 (s, 1H, H8),
7.17 (t, 1H, Hp, Ph, 3JHH = 7.6), 7.27 (t, 2H, Hm, Ph, 3JHH = 7.6), 7.40
4
4
(d, 1H, H3, JHH = 1.2), 7.56 (dd, 2H, Ho, JHH = 1.6), 7.69 (d, 1H,
H5).
Synthesis of 4g. Complex 4g was obtained following the same
method than that described for 4a, except that the reaction starts from
the imidazolium salt instead of the ylide. Therefore, 1g (0.267 g, 0.951
mmol) was reacted with Pd(OAc)2 (0.213 g, 0.951 mmol) in dry
CH2Cl2 (15 mL) at 25 °C for 2 h. The resulting suspension was
evaporated to dryness and the residue dissolved in MeOH (20 mL)
and treated with LiCl (0.084 g, 1.97 mmol). The resulting mixture was
stirred at room temperature, and after some minutes, 4g precipitated
as a yellow solid. Obtained: 0.190 g (58.6% yield). Anal. Calcd for
C24H22Cl2N4O2Pd2 (682.17): C, 42.26; H, 3.25; N, 8.21. Found: C,
42.09; H, 3.11; N, 7.96. NMR: 4g could not be fully characterized due
to its insolubility in common organic solvents.
Synthesis of 4i. Complex 4i was obtained following the same
method than that described for 4f. Therefore, 2i (0.100 g, 0.366
mmol) was reacted with Pd(OAc)2 (0.083 g, 0.366 mmol) in dry
CH2Cl2 (15 mL) at 38 °C for 4 h, and with LiCl (0.084 g, 1.97 mmol)
in MeOH (20 mL), giving 4i as a yellow solid. Obtained: 0.13 g
(85.8% yield). Anal. Calcd for C38H28Cl2N2O2Pd2 (828.36): C, 55.10;
H, 3.41; N, 3.38. Found: C, 54.93; H, 3.44; N, 3.12. IR: ν = 1651
(νCO) cm−1. NMR: 4i could not be fully characterized due to its
insolubility in common organic solvents.
Synthesis of 4a. A solution of 2a (0.120 g, 0.659 mmol) and
Pd(OAc)2 (0.147 g, 0.659 mmol) in dry toluene (15 mL) was stirred
at 60 °C for 2 h. After the reaction time, the resulting suspension was
cooled, and the precipitated solid was filtered and washed with toluene
(5 mL). This solid was suspended in MeOH and allowed to react with
excess LiCl (0.055 g, 1.318 mmol) at 25 °C for 30 min. The color of
the suspension evolved, and a yellow solid was finally obtained. The
suspension was filtered, and the yellow solid 4a was washed with
MeOH (5 mL) and Et2O (25 mL) and dried in vacuo. Obtained: 0.19
g (85% yield). Anal. Calcd for C26H20Cl2N2O2Pd2 (676.2): C, 46.18;
H, 2.98; N, 4.14. Found: C, 45.92; H, 3.18; N, 3.92. MS (MALDI+)
[m/z, (%)]: 641 (10%) [M − Cl]+. IR: ν = 1668 (νCO) cm−1. 1H NMR
(dmso-d6): δ 6.82 (s, 1H, C(H)N), 7.16 (s, br, 2H, H4 + H5), 7.42 (s,
v br, 1H, H6), 7.98 (t, 2H, Hm, py, 3JHH = 6.4), 8.21 (s, v br, 1H, H3),
8.38 (t, br, 1H, Hp, py), 8.82 (s, br, 2H, Ho, py).
Synthesis of 4b. Complex 4b was obtained following the same
method than that described for 4a with slight modifications.
Therefore, 2b (0.06 g, 0.264 mmol) was reacted with Pd(OAc)2
(0.059 g, 0.264 mmol) in dry toluene (15 mL) at 25 °C for 15 h, and
with LiCl (0.023 g, 0.542 mmol) in MeOH (10 mL), giving 4b as a
yellow solid. Obtained: 0.049 g (50% yield). Anal. Calcd for
C28H24Cl2N2O4Pd2 (736.25): C, 45.68; H, 3.29; N, 3.80. Found: C,
45.65; H, 3.61; N, 3.68. MS (MALDI+) [m/z, (%)]: 736 (10%) [M]+.
Synthesis of 5a. Complexes 5a−5i were prepared using the same
experimental method. Only the representative synthesis of 5a is
detailed here. To a suspension of 4a (0.101 g, 0.148 mmol) in CH2Cl2
(10 mL) was added Tl(acac) (0.089 g, 0.296 mmol). The appearance
of the suspension changed, and a white precipitate was obtained after
30 min of stirring at 25 °C. This suspension was filtered through a
Celite pad, and the resulting solution was evaporated to dryness. The
treatment of the residue with cold n-pentane (15 mL) and stirring gave
complex 5a as a pale yellow solid. Obtained: 0.089 g (75.2% yield).
Anal. Calcd for C18H17NO3Pd (401.75 g/mol): C, 53.81; H, 4.27; N,
3.49. Found: C, 53.46; H, 4.01; N, 3.27. IR: ν = 1664 (νCO, ylide),
1578, 1505 (νCO, acac) cm−1. MS: (ESI+) [m/z, (%)]: 301.9 (100%)
1
IR: ν = 1647 (νCO3) cm−1. H NMR (dmso-d6): δ 3.68 (s, 3H, OMe),
6.66 (d, 1H, H4, JHH = 7.6), 6.70 (s, 1H, CHN), 7.33 (d, 1H, H3),
3
7.83 (s, 1H, H6), 7.89 (m, 2H, Hm, py), 8.30 (t, 1H, Hp, py, JHH
=
7.6), 8.73 (s, br, 2H, Ho, py).
Synthesis of 4c. Complex 4c was obtained following the same
method than that described for 4a with slight modifications.
Therefore, 2c (0.128 g, 0.499 mmol) was reacted with Pd(OAc)2
(0.112 g, 0.499 mmol) in dry toluene (15 mL) at 40 °C for 2 h, and
with LiCl (0.042 g, 1.00 mmol) in MeOH (20 mL), giving 4c as a
yellow solid. Obtained: 0.134 g (68% yield). Anal. Calcd for
C30H28Cl2N2O6Pd2 (796.3): C, 45.25; H, 3.54; N, 3.52. Found: C,
45.06; H, 3.99; N, 3.91. MS (MALDI+) [m/z, (%)]: 761 (60.6%) [M
− Cl]+. IR: ν = 1648 (νCO) cm−1. 1H NMR (dmso-d6): δ 3.68 (s, 3H,
MeO), 3.75 (s, 3H, MeO), 6.27 (s, 1H, C(H)N), 6.55 (s, 1H, H4),
7.47 (s, br, 1H, H6), 7.94 (t, 2H, Hm, py, 3JHH = 6.3), 8.35 (t, 1H, Hp,
py), 8.75 (d, 2H, Ho, py). 13C{1H} NMR (dmso-d6): δ 55.01 (CH3O),
55.06 (CH3O), 82.13 (C(H)N), 95.75 (C4), 109.78 (C6), 122.03
(C2), 126.09 (Cm, py), 142.22 (Cp, py), 145.40 (Co, py), 155.87 (C-
O), 158.54 (C-O), 160.37 (C1), 194.05 (CO).
1
[M − acac]+. H NMR (CDCl3): δ 1.38 (s, 3H, CH3, acac), 1.94 (s,
3H, CH3, acac), 5.11 (s, 1H, CH-acac), 6.54 (s, 1H, C(H)N), 7.03 (td,
3
3
4
1H, H5, JH5−H4 ≈ JH5−H6 = 7.4, JH5−H3 = 1.0), 7.16 (td, 1H, H4,
3JH4−H3 = 7.4, JH4−H6 = 1.4), 7.44 (dd, 1H, H6), 7.64 (t, 2H, Hm, py,
4
3JHH = 7.3), 7.86 (d, 1H, H3), 8.06 (t, 1H, Hp, py), 8.71 (d, 2H, Ho,
py). 13C{1H} NMR (CDCl3): δ 27.57 (CH3, acac), 28.20 (CH3, acac),
79.33 (CHN), 99.96 (CH, acac), 124.40 (C4, C6H4), 124.72 (C3,
C6H4), 126.07 (Cm, py), 130.21 (C5, C6H4), 132.17 (C6, C6H4),
140.84 (Cp, py), 142.87 (C2, C6H4), 145.17 (Co, py), 152.20 (C1,
C6H4), 186.70 (CO, acac), 187.49 (CO, acac), 200.62 (CO, ylide).
Synthesis of 5b. 4b (0.030 g, 0.041 mmol) was reacted with
Tl(acac) (0.024 g, 0.081 mmol) in CH2Cl2 (10 mL), giving 5b as a
yellow solid. Obtained: 0.016 g (90% yield). Anal. Calcd. for
C19H19NO4Pd (431.78): C, 52.85; H, 4.44; N, 3.24. Found: C,
52.74; H, 4.67; N, 3.59. MS (MALDI) [m/z, (%)]: 331.6 (24.4%) [M
Synthesis of 4d. Complex 4d was obtained following the same
method than that described for 4a with slight modifications.
Therefore, 2d (0.15 g, 0.71 mmol) was reacted with Pd(OAc)2
(0.16 g, 0.71 mmol) in dry toluene (15 mL) at 60 °C for 1 h, and
with LiCl (0.060 g, 1.42 mmol) in MeOH (15 mL), giving 4d as a
yellow solid. Obtained: 0.147 g (78% yield). Anal. Calcd for
C28H24Cl2N2O2Pd2 (704.25): C, 47.75; H, 3.43; N, 3.98. Found: C,
47.92; H, 3.68; N, 3.74. MS (MALDI) [m/z, (%)]: 669 (34.8%) [M −
1
− acac]+. IR: ν = 1641 (νCO, ylide), 1567, 1505 (νCO, acac) cm−1. H
NMR (CDCl3): δ 1.41 (s, 3H, CH3, acac), 1.94 (s, 3H, CH3, acac),
3.82 (s, 3H, CH3O), 5.12 (s, 1H, CH, acac), 6.46 (s, 1H, C(H)N),
6.61 (dd, 1H, H4, 3JH4−H3 = 8.4, 4JH4−H6 = 2.5), 7.39 (d, 1H, H6), 7.43
(d, 1H, H3), 7.64 (t, 2H, Hm, py, 3JHH = 7.8), 8.06 (t, 1H, Hp, py), 8.68
(d, 2H, Ho, py).
1
Cl]+. IR: ν = 1655 (νCO) cm−1. H NMR (dmso-d6): δ 2.54 (s, 3H,
CH3), 6.74 (s, br, 1H, C(H)N), 7.15 (s, br, 2H, H4 + H5), 7.41 (s, br,
1H, H6), 7.79 (s, br, 2H, Hm, py), 8.21 (s, br, 1H, H3), 8.65 (s, br, 2H,
Ho, py). 13C{1H} NMR (dmso-d6): δ 21.19 (CH3), 81.69 (C(H)N),
124.34 (C6), 124.66 (C5), 126.67 (Cm, py), 129.39 (C4), 133.88 (C3),
144.48 (Cp, py), 150.24 (Co, py), 152.21 (C2), 155.34 (C1), 197.73
(CO).
Synthesis of 4f. Complex 4f was obtained following the same
method than that described for 4a with some modifications. Therefore,
2f (0.250 g, 0.987 mmol) was reacted with Pd(OAc)2 (0.213 g, 0.951
mmol) in dry toluene (15 mL) at 60 °C for 1.5 h. The resulting
suspension was evaporated to dryness and the residue dissolved in
Synthesis of 5c. 4c (0.020 g, 0.025 mmol) was reacted with
Tl(acac) (0.015 g, 0.050 mmol) in CH2Cl2 (10 mL), giving 5c as a
yellow solid. Obtained: 0.010 g (93% yield). Anal. Calcd for
C20H21NO5Pd (461.8): C, 52.02; H, 4.58; N, 3.03. Found: C, 51.83;
H, 4.55; N, 3.26. MS (MALDI+) [m/z, (%)]: 363 (15.3%) [M −
acac]+. IR: ν = 1644 (νCO, ylide), 1574, 1553, 1511 (νCO, acac) cm−1.
1H NMR (CDCl3): δ 1.43 (s, 3H, CH3, acac), 1.94 (s, 3H, CH3, acac),
3.74 (s, 3H, CH3O), 3.83 (s, 3H, CH3O), 5.13 (s, 1H, CH, acac), 6.09
400
dx.doi.org/10.1021/om201001c | Organometallics 2012, 31, 394−404

Organometallics
Article
4
(d, 1H, H4, JH4−H6 = 2.1), 6.33 (s, 1H, C(H)N), 7.05 (d, 1H, H6),
treated with cold n-pentane (20 mL). Further stirring gave 5h as a
yellow solid. Obtained: 0.166 g (34.3% yield). Complex 5h was
characterized spectroscopically as the mixture of the mononuclear 5h1
and the dinuclear 5h2 complexes in a 1:5 molar ratio. IR: ν = 1555
7.64 (t, 2H, Hm, py, 3JHH = 7.8), 8.07 (t, 1H, Hp, py), 8.67 (d, 2H, Ho,
py). 13C{1H} NMR (CDCl3): δ 26.57 (CH3, acac), 27.23 (CH3, acac),
54.25 (OMe), 54.32 (OMe), 78.25 (CHN), 94.92 (C4, C6H4), 98.85
(CH, acac), 105.43 (C6, C6H4), 122.64 (C2, C6H4), 124.79 (Cm, py),
139.77 (Cp, py), 144.32 (Co, py), 157.37 (C3, C6H4), 158.36 (C5,
C6H4), 160.52 (C1, C6H4), 185.59 (CO, acac), 186.56 (CO, acac),
196.96 (CO, ylide).
1
(νCO, ylide), 1573, 1512 (νCO, acac) cm−1. H NMR (CDCl3): δ 1.72
(s, CH3, acac, 5h1), 1.80 (s, CH3, acac, 5h2), 1.89 (s, CH3, acac, 5h2),
1.99 (s, CH3, acac, 5h1), 2.02 (s, CH3, acac, 5h2), 2.03 (s, CH3, acac,
5h2), 3.69 (s, NCH3, 5h1), 3.74 (s, NCH3, 5h2), 3.76 (s, NCH3,
5h2), 3.78 (s, NCH3, 5h1), 5.18 (s, CH, acac, 5h1), 5.23 (s, CH, acac,
5h2), 5.29 (s, CH, acac, 5h2), 6.03 (s, CHN, 5h2), 6.14 (s, CHN,
5h1), 6.90 (dd, H3′, NC6H4, 5h2, 3JHH = 7.1, 4JHH = 1.9), 6.98 (td, H5,
C6H4, 5h2, 3JHH = 7.6, 4JHH = 1.1), 7.13−7.22 (m, H4 (C6H4) + H4′,H5′
(NC63H4), 5h2), 7.28−7.29 (m, H3, C6H4, 5h2), 7.54 (dd, H6, C6H4,
Synthesis of 5d. 4d (0.097 g, 0.14 mmol) was reacted with
Tl(acac) (0.086 g, 0.28 mmol) in CH2Cl2 (10 mL), giving 5d as a
yellow solid. Obtained: 0.030 g (51% yield). Anal. Calcd for
C19H19NO3Pd (415.78): C, 54.89; H, 4.61; N, 3.37. Found: C,
54.91; H, 4.92; N, 3.53. MS (ESI+) [m/z, (%)]: 314.9 (87.5%) [M −
acac]+. IR: ν = 1649, 1636 (νCO, ylide), 1571, 1509(νCO, acac) cm−1.
1H NMR (CDCl3): δ 1.43 (s, 3H, CH3, acac), 1.94 (s, 3H, CH3, acac),
2.49 (s, 3H, CH3), 5.12 (s, 1H, CH, acac), 6.46 (s, 1H, C(H)N), 7.03
(t, 1H, H5, 3JH5−H4 ≈ 3JH5−H6 = 7.1), 7.17 (m, 1H, H4), 7.40−7.50 (m,
3H, H3 + Hm (pic)), 7.86 (d, 1H, H6, 3JH6−H5 = 7.4), 8.50 (d, 2H, Ho,
4
3
5h2, JHH = 7.6, JHH = 1.0), 7.67 (dd, H6′, NC6H4, 5h2, JHH = 7.2,
4JHH = 2.2). In the aromatic region, only the following signals assigned
to the minor isomer 5h1 could be identified unambiguously: 7.36 (t,
Hm, NPh, 3JHH = 7.8), 7.54 (t, Hp, NPh), 8.02 (d, Ho, NPh). 13C{1H}
NMR (CDCl3): δ 27.35, 27.65, 27.71, 27.88 (4CH3, 2 acac), 51.71
(NCH3), 63.37 (NCH3), 85.48 (CHN), 99.69 (CH, acac), 100.33
(CH, acac), 114.55, 122.96, 124.99, 127.77, 128.61, 130.19, 131.69,
134.12 (CH of C6H4 and NC6H4), 146.59, 156.93, 157.00 (Cq of C6H4
and NC6H4), 186.13, 186.81, 186.95, 188.51 (4CO, 2 acac), 207.06
(CO, ylide) (one of the Cq atoms was not detected). Only the signals
of the major isomer, 5h2, could be unambiguously identified.
pic, JHH = 5.9). 13C{1H} NMR (CDCl3): δ 21.87 (CH3, pic), 27.71
3
(CH3, acac), 28.20 (CH3, acac), 78.56 (CHN), 99.87 (CH, acac),
124.31 (C5, C6H4), 124.61 (C3, C6H4), 126.61 (Cm, pic), 130.11 (C4,
C6H4), 132.16 (C6, C6H4), 142.73 (Cp, pic), 144.59 (Co, pic), 152.26
(C2, C6H4), 154.49 (C1, C6H4), 186.58 (CO, acac), 187.51 (CO,
acac), 201.21 (CO, ylide).
Synthesis of 5f. 4f (0.120 g, 0.152 mmol) was reacted with
Tl(acac) (0.092 g, 0.304 mmol) in CH2Cl2 (10 mL), giving 5f as a
yellow solid. Obtained: 0.097 g (70% yield). Anal. Calcd for
C22H25NO3Pd (457.86): C, 57.71; H, 5.50; N, 3.06. Found: C,
Synthesis of 5i. 4i (0.084 g, 0.100 mmol) was reacted with
Tl(acac) (0.061 g, 0.202 mmol) in CH2Cl2 (15 mL), giving 5i as a
yellow solid. Obtained: 0.058 g (63% yield). Anal. Calcd for
C24H21NO3Pd (477.84): C, 60.32; H, 4.43; N, 2.93. Found: C,
59.98; H, 4.12; N, 2.55. IR: ν = 1650 (νCO, ylide), 1580, 1511 (νCO
,
57.60; H, 5.91; N, 3.19. IR: ν = 1647 (νCO, ylide), 1574, 1515 (νCO
,
acac) cm−1. 1H NMR (CDCl3): δ 1.89 (s, 3H, CH3, acac), 1.99 (s, 3H,
CH3, acac), 5.23 (s, 1H, CH, acac), 6.70 (s, 1H, CHN), 7.02−7.08 (m,
2H, H4′ + H5′3, C6H4), 7.24−7.30 (m, 3H, Hm (Ph) + H5 (py)), 7.37 (t,
1H, Hp, Ph, JHH = 7.6), 7.54 (m, 1H, H6′, C6H4), 7.61 (m, 1H, H3′,
C6H4), 7.91−7.98 (m, 2H, H3 + H4, py), 8.17−8.21 (m, 3H, Ho (Ph)
+ H6 (py)). 13C{1H} NMR (CDCl3): δ 28.34 (CH3, acac), 28.40
(CH3, acac), 69.71 (CHN), 99.56 (CH, acac), 122.32 (C5, py), 124.72,
129.51 (C4′ + C5′, C6H4), 126.72 (two collapsed signals, C3′ (C6H4) +
C4(py)), 128.10 (Cm, PhCO), 128.80 (Co, PhCO), 132.08 (Cp,
PhCO), 135.34, 136.56 (Cipso (PhCO) + C2′ (C6H4)), 136.86 (C6′,
C6H4), 140.66 (C3, py), 141.48 (C6, py), 154.84 (C1′, C6H4), 162.67
(C2, py), 186.59 (CO, acac), 187.92 (CO, acac), 192.45 (CO, ylide).
X-ray Crystallography. Crystals of 5c of suitable quality for X-ray
measurements were grown by diffusion of n-hexane into a CH2Cl2
solution of the crude product at −15 °C. A single crystal was mounted
at the end of a quartz fiber in a random orientation, covered with
perfluorinated oil and placed under a cold stream of N2 gas. Data
collection was performed on an Oxford Diffraction Xcalibur2
diffractometer using graphite-monocromated Mo Kα radiation (λ =
0.71073 Å). A hemisphere of data was collected based on ω-scan or ϕ-
scan runs. The diffraction frames were integrated using the program
CrysAlis RED,31 and the integrated intensities were corrected for
absorption with SADABS.32 The structure was solved and developed
by Patterson and Fourier methods.33 All non-hydrogen atoms were
refined with anisotropic displacement parameters. The hydrogen
atoms were placed at idealized positions and treated as riding atoms.
Each H atom was assigned an isotropic displacement parameter equal
to 1.2 times the equivalent isotropic displacement parameter of its
acac) cm−1. MS: (MALDI+) [m/z, (%)]: 357.8 (14%) [M − acac]+.
1H NMR (CDCl3): δ 1.89 (s, 3H, CH3, acac), 1.97 (s, 3H, CH3, acac),
2
3.26 (s, 6H, Me2N), 4.89 (d, 1H, CH2N, JHH = 12.6), 5.04 (d, 1H,
CH2N), 5.21 (s, 1H, C(H)N), 5.28 (s, 1H, CH, acac), 7.02 (td, 1H,
3
3
4
3
H5, JH5H4 ≈ JH5H6 ≈ 7.2, JH5H3 = 1.1), 7.05 (td, 1H, H4, JH4H5
≈
3JH4H3 ≈ 7.2, 4JH4H6 = 1.6), 7.33 (dd, 1H, H6), 7.36−7.39 (m, 3H, Hm
+ Hp, Ph), 8.71 (dd, 2H, Ho, Ph, 3JHH = 7.6, 4JHH = 2.1), 7.80 (d, 1H,
H3). 13C{1H} NMR (CDCl3): δ 28.29 (CH3, acac), 28.44 (CH3, acac),
50.23 (Me2N), 50.49 (Me2N), 66.81 (CH2N), 80.82 (C(H)N), 99.72
(CH, acac), 123.26 (C3), 124.33 (C5), 128.70 (C4), 128.97 (Cm, py),
129.27 (s, Cipso, Ph), 130.12 (Cp, Ph), 130.77 (C6), 133.01 (Co, Ph),
141.96 (C2), 146.87 (C1), 185.77 (CO, acac), 188.37 (CO, acac),
197.77 (CO, ylide).
Synthesis of 5g. 4g (0.100 g, 0.146 mmol) was reacted with
Tl(acac) (0.087 g, 0.293 mmol) in CH2Cl2 (15 mL), giving 5g as a
yellow solid. Obtained: 0.072 g (60.5% yield). Anal. Calcd for
C17H18N2O3Pd (404.74): C, 50.45; H, 4.48; N, 6.92. Found: C, 50.23;
H, 4.17; N, 7.01. IR: ν = 1662 (νCO, ylide), 1583, 1510 (νCO, acac)
cm−1. 1H NMR (CDCl3): δ 1.62 (s, 3H, CH3, acac), 1.96 (s, 3H, CH3,
acac), 3.74 (s, 3H, NMe), 5.19 (s, 1H, CH, acac), 6.18 (s, 1H, CHN),
3
6.92 (s, 1H, H4, imid), 7.02 (t, 1H, H4, C6H4, JHH = 7.3), 7.14 (td,
1H, H5, C6H4, 3JHH = 7.3, 4JHH = 1.1), 7.32 (s, 1H, H5, imid), 7.40 (d,
1H, H3, C6H4), 7.57 (d, 1H, H6, C6H4), 8.62 (s, 1H, H2, imid).
13C{1H} NMR (CDCl3): δ 28.18 (CH3, acac), 28.34 (CH3, acac),
35.84 (NCH3, imid), 64.50 (CHN), 99.85 (CH, acac), 120.12 (C4,
imid), 124.21 (C3, C6H4), 125.85 (C4, C6H4), 125.87 (C5, imid),
129.82 (C5, C6H4), 131.96 (C6, C6H4), 142.04 (C2, C6H4), 151.42
(C1, C6H4), 186.12 (CO, acac), 188.02 (CO, acac), 202.52 (CO,
ylide). The signal corresponding to the C2 (imid) carbon was not
observed.
2
parent atom. The structures were refined to Fo , and all reflections
were used in the least-squares calculations.34
Synthesis of 5h. To a suspension of 1h (0.174 g, 0.545 mmol) in
toluene (15 mL) was added Pd(OAc)2 (0.122 g, 0.545 mmol). This
mixture was stirred at 60 °C for 2 h, then the resulting solid was
separated by centrifugation. This solid was dissolved in MeOH (10
mL) and was reacted with an excess of LiCl (0.086 g, 2.02 mmol) for 2
h. After the reaction time, the solvent was evaporated in vacuo and the
residue redissolved in CH2Cl2 (20 mL), giving a yellow solution. This
solution was treated with Tl(acac) (0.330 g, 1.09 mmol) and stirred
for 25 min at 25 °C. After filtration of all insoluble solids (TlCl and
LiCl), the resulting solution was evaporated to dryness and the residue
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF of complex 5c. This material is available free of charge via
the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Fax: (+0034)976761187. E-mail: esteban@unizar.es.
401
dx.doi.org/10.1021/om201001c | Organometallics 2012, 31, 394−404

Organometallics
Article
(c) Powers, D. C.; Geibel, M. A. L.; Klein, J. E. M. N.; Ritter, T. J. Am.
Chem. Soc. 2009, 131, 17050.
ACKNOWLEDGMENTS
■
Funding by the Ministerio de Ciencia e Innovacion
(Spain, Project CTQ2008-01784) and Gobierno de Aragon
(Grupo E97) is gratefully acknowledged. L.C. thanks Consejo
Superior de Investigaciones Cientificas and MICINN for a Juan
de la Cierva contract.
́
(MICINN)
(7) Example of introductionof arylsulfonyl groups: Zhao, X.;
Dimitrijevic, E.; Dong, V. M. J. Am. Chem. Soc. 2009, 131, 3466.
(8) Example of introductionof ethoxycarbonyl groups: Yu, W. Y.; Sit,
W. N.; Lai, K. M.; Zhou, Z.; Chan, A. S. C. J. Am. Chem. Soc. 2008,
130, 3304.
́
(9) Selected halogenation reactions: (a) Hull, K. L.; Anani, W. Q.;
Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 7134. (b) Whitfield, S. R.;
Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 15142. (c) Li, J. J.; Mei, T.
S.; Yu, J.-Q. Angew. Chem., Int. Ed. 2008, 47, 6452. (d) Wang, X.; Mei,
T.-S.; Yu, J.-Q. J. Am. Chem. Soc. 2009, 131, 7520. (e) Powers, D. C.;
Ritter, T. Nat. Chem. 2009, 1, 302.
(10) Selected amidation and carboamidation reactions: (a) Thu, H.-
Y.; Yu, W.-Y.; Che, C.-M. J. Am. Chem. Soc. 2006, 128, 9048.
́
(b) Houlden, C. E.; Bailey, C. D.; Ford, J. G.; Gagne, M. R.; Lloyd-
Jones, G. C.; Booker-Milburn, K. I. J. Am. Chem. Soc. 2008, 130, 10066.
(11) Example of aminationreactions: Dick, A. R.; Remy, M. S.;
Kampf, J. W.; Sanford, M. S. Organometallics 2007, 26, 1365.
(12) Example of introductionof alkynyl groups: Tobisu, M.; Ano, Y.;
Chatani, N. Org. Lett. 2009, 11, 3250.
REFERENCES
■
(1) Selected recent reviews: (a) Godula, K.; Sames, D. Science 2006,
312, 67. (b) Deprez, N. R.; Sanford, M. S. Inorg. Chem. 2007, 46, 1924.
(c) Alberico, D.; Scott, M. E.; Lautens, M. Chem. Rev. 2007, 107, 174.
(d) Park, Y. J.; Park, J.-W.; Jun, C.-H. Acc. Chem. Res. 2008, 41, 222.
(e) Kakiuchi, F.; Kochi, T. Synthesis 2008, 3013. (f) Chen, X.; Engle,
K. M.; Wang, D.-H.; Yu, J.-Q. Angew. Chem., Int. Ed. 2009, 48, 5094.
(g) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem. Soc.
Rev. 2009, 38, 3242. (h) Storr, T. E.; Baumann, C. G.; Thatcher, R. J.;
De Ornellas, S.; Whitwood, A. C.; Fairlamb, I. J. S. J. Org. Chem. 2009,
74, 5810. (i) Daugulis, O.; Do, H.-Q.; Shabashov, D. Acc. Chem. Res.
2009, 42, 1074. (j) Zhang, M. Adv. Synth. Catal. 2009, 351, 2243.
(13) Selected alkenylation reactions: (a) Lee, G. T.; Jiang, X.; Prasad,
K.; Repic, O.; Blacklock, T. J. Adv. Synth. Catal. 2005, 347, 1921.
(b) Rauf, W.; Thompson, A. L.; Brown, J. M. Chem. Commun. 2009,
3874.
(14) Example of acylationreactions: Jia, X.; Zhang, S.; Wang, W.;
Luo, F.; Cheng, J. Org. Lett. 2009, 11, 3120.
(k) Vedernikov, A. N. Chem. Commun. 2009, 4781. (l) Muniz, K.
̃
Angew. Chem., Int. Ed. 2009, 48, 9412. (m) Ackermann, L.; Vicente, R.;
Kapdi, A. R. Angew. Chem., Int. Ed. 2009, 48, 9792. (n) Roger, J.;
Gottumukkala, A. L.; Doucet, H. ChemCatChem 2010, 2, 20.
(o) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. Rev. 2010,
110, 624. (p) Yu, J.-Q.; Shi, Z. C-H Activation. In Topics in Current
Chemistry; Springer Verlag: Heidelberg, Germany, 2010; Vol. 292.
(q) Zhang, S.-Y.; Zhang, F.-M.; Tu, Y.-Q. Chem. Soc. Rev. 2011, 40,
1937. (r) McMurray, L.; O’Hara, F.; Gaunt, M. J. Chem. Soc. Rev. 2011,
40, 1885. (s) Davies, H. M. L.; Morton, D. Chem. Soc. Rev. 2011, 40,
1857. (t) Yeung, C. S.; Dong, V. M. Chem. Rev. 2011, 111, 1215.
(u) Collet, F.; Lescot, C.; Dauban, P. Chem. Soc. Rev. 2011, 40, 1926.
(v) Boorman, T. C.; Larrosa, I. Chem. Soc. Rev. 2011, 40, 1910.
(w) Hartwig, J. F. Chem. Soc. Rev. 2011, 40, 1992. (x) Zhou, M.;
Crabtree, R. H. Chem. Soc. Rev. 2011, 40, 1875. (y) Shi, W.; Liu, C.;
Lei, A. Chem. Soc. Rev. 2011, 40, 2761. (z) Gutekunst, W. R.; Baran, P.
S. Chem. Soc. Rev. 2011, 40, 1976.
(15) Selected arylation reactions: (a) Hull, K. L.; Sanford, M. S. J.
Am. Chem. Soc. 2009, 131, 9651. (b) Liegault, B.; Lapointe, D.; Caron,
́
L.; Vlassova, A.; Fagnou, K. J. Org. Chem. 2009, 74, 1826. (c) Campeau,
L. C.; Schipper, D. J.; Fagnou, K. J. Am. Chem. Soc. 2008, 130, 3266.
(d) Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 11904.
(e) Lafrance, M.; Gorelsky, S. I.; Fagnou, K. J. Am. Chem. Soc. 2007,
129, 14570. (f) Daugulis, O.; Zaitsev, V. G. Angew. Chem., Int. Ed.
2005, 44, 4046. (g) Lazareva, A.; Daugulis, O. Org. Lett. 2006, 8, 5211.
(h) Shabashov, D.; Daugulis, O. Org. Lett. 2006, 8, 4947. (i) Daugulis,
O.; Zaitsev, V. G.; Shavashov, D.; Pham, Q. N.; Lazareva, A. Synlett
2006, 3382. (j) Scarborough, C. C.; McDonald, R. I.; Hartmann, C.;
Sazama, G. T.; Bergant, A.; Stahl, S. S. J. Org. Chem. 2009, 74, 2613.
(k) Zhou, H.; Chung, W.-J.; Xu, Y.-H.; Loh, T.-P. Chem. Commun.
2009, 3472. (l) Zhou, H.; Xu, Y.-H.; Chung, W.-J.; Loh, T.-P. Angew.
Chem., Int. Ed. 2009, 48, 5355. (m) Watanabe, T.; Oishi, S.; Fujii, N.;
Ohno, H. J. Org. Chem. 2009, 74, 4720. (n) Kalyani, D.; Deprez, N. R.;
Desai, L. V.; Sanford, M. S. J. Am. Chem. Soc. 2005, 127, 7330.
(o) Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006,
128, 14047.
(2) Chatani, N. Directed Metallation; Topics in Organometallic
Chemistry; Springer Verlag: Berlin, Germany, 2007; Vol. 24.
(3) Selected recent reviews on orthometalation: (a) Dupont, J.;
Consorti, C.; Spencer, J. Chem. Rev. 2005, 105, 2527. (b) Yu, J.-Q.;
Giri, R.; Chen, X. Org. Biomol. Chem. 2006, 4, 4041. (c) Fairlamb, I. J.
S. Chem. Soc. Rev. 2007, 36, 1036. (d) Omae, I. J. Organomet. Chem.
2007, 692, 2608. (e) Nishiyama, H. Chem. Soc. Rev. 2007, 36, 1133.
(f) Gagliardo, M.; Snelders, D. J. M.; Chase, P. A.; Klein Gebbink, R. J.
M.; van Klink, G. P. M; van Koten, G. Angew. Chem., Int. Ed. 2007, 46,
8558. (g) Horino, Y. Angew. Chem., Int. Ed. 2007, 46, 2144. (h) Ma, L.;
Wong, E. L.-M.; Che, C.-M. Dalton Trans. 2007, 4884. (i) Leis, W.;
Mayera, H. A.; Kaska, W. C. Coord. Chem. Rev. 2008, 252, 1787.
(j) Djukic, J. P.; Hijazi, A.; Flack, H. D.; Bernardinelli, G. Chem. Soc.
Rev. 2008, 37, 406. (k) Djukic, J. P.; Sortais, J. B.; Barloy, L.; Pfeffer,
M. Eur. J. Inorg. Chem. 2009, 817. (l) Albrecht, M. Chem. Rev. 2010,
(16) Selected cyclization reactions: (a) Tsang, W. C. P.; Zheng, N.;
Buchwald, S. L. J. Am. Chem. Soc. 2005, 127, 14560. (b) Muniz, K. J.
̃
Am. Chem. Soc. 2007, 129, 14542. (c) Wu, L.; Qiu, S.; Liu, G. Org. Lett.
2009, 11, 2707. (d) Yamashita, M.; Hirano, K.; Satoh, T.; Miura, M.
Org. Lett. 2009, 11, 2337. (e) Joyce, L. L.; Batey, R. A. Org. Lett. 2009,
11, 2792. (f) Xiao, Q.; Wang, W.-H.; Liu, G.; Meng, F.-K.; Chen, J.-H.;
Yang, Z.; Shi, Z.-J. Chem.Eur. J. 2009, 15, 7292. (g) Murai, M.; Miki,
K.; Ohe, K. Chem. Commun. 2009, 3466.
110, 576. (m) Wencel-Delord, J.; Droge, T.; Liu, F.; Glorius, F. Chem.
̈
(17) Examples of mechanistic studies: (a) Dick, A. R.; Kampf, J. W.;
Sanford, M. S. J. Am. Chem. Soc. 2005, 127, 12790. (b) Racowski, J. M.;
Dick, A. R.; Sanford, M. S. J. Am. Chem. Soc. 2009, 131, 10974.
(c) Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2009, 131, 9651.
(d) Deprez, N. R.; Sanford, M. S. J. Am. Chem. Soc. 2009, 131, 11234.
(18) General reviews: (a) Johnson, A. W. Ylides and Imines of
Phosphorus; John Wiley & Sons: New York, 1993; Chapter 14.
(b) Cristau, H. J. Chem. Rev. 1994, 94, 1299. (c) Belluco, U.; Michelin,
R. A.; Mozzon, M.; Bertani, R.; Facchin, G.; Zanotto, L.; Pandolfo, L. J.
Organomet. Chem. 1998, 557, 37. (d) Kolodiazhnyi, O. I. Phosphorus
Ylides; Wiley-VCH: Weinheim, Germany, 1999. (e) Vicente, J.;
Chicote, M. T. Coord. Chem. Rev. 1999, 193−195, 1143. (f) Navarro,
R.; Urriolabeitia, E. P. J. Chem. Soc., Dalton Trans. 1999, 4111.
(g) Chauvin, R. Eur. J. Inorg. Chem. 2000, 577. (h) Bertani, R.; Casarin,
M.; Pandolfo, L. Coord. Chem. Rev. 2003, 236, 15. (i) Taillefer, M.;
Soc. Rev. 2011, 40, 4740.
(4) (a) Pfeffer, M.; Dupont, J. Palladacycles; Wiley-VCH: Weinheim,
Germany, 2008. (b) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010,
110, 1147. (c) Sehnal, P.; Taylor, R. J. K.; Fairlamb, I. J. S. Chem. Rev.
2010, 110, 824. (d) Xu, L.-M.; Li, B.-J.; Yang, Z.; Shi, Z.-J. Chem. Soc.
Rev. 2010, 39, 712. (e) Sun, C.-L.; Li, B.-J.; Shi, Z.-J. Chem. Commun.
2010, 46, 677.
(5) Selected alkylation reactions: (a) Chen, X.; Goodhue, C. E.; Yu,
J.-Q. J. Am. Chem. Soc. 2006, 128, 12634. (b) Giri, R.; Maugel, N.; Li,
J.-J.; Wang, D.-H.; Breazzano, S. P.; Saunders, L. B.; Yu, J.-Q. J. Am.
Chem. Soc. 2007, 129, 3510. (c) Zhao, Y.; Chen, G. Org. Lett. 2011, 13,
4850.
(6) Selected acetoxylation and alkoxylation processes: (a) Desai, L.
V.; Malik, H. A.; Sanford, M. S. Org. Lett. 2006, 8, 1141. (b) Desai, L.
V.; Stowers, K. J.; Sanford, M. S. J. Am. Chem. Soc. 2008, 130, 13285.
402
dx.doi.org/10.1021/om201001c | Organometallics 2012, 31, 394−404

Organometallics
Article
Cristau, H. J. Top. Curr. Chem. 2003, 229, 41. (j) Kuhn, P.; Sem
D.; Matt, D.; Chetcuti, M. J.; Lutz, P. Dalton Trans. 2007, 515.
(k) Cantat, T.; Mezailles, N.; Auffrant, A.; Le Floch, P. Dalton Trans.
́
eril,
Lahoz, F. J.; Lop
́
ez, J. A. Inorg. Chem. 1991, 30, 3617. (d) Vicente, J.;
Chicote, M. T.; Lagunas, M. C.; Jones, P. G. Inorg. Chem. 1995, 34,
5441. (e) Vicente, J.; Chicote, M. T.; Beswick, M. A.; Ramírez de
Arellano, M. C. Inorg. Chem. 1996, 35, 6592. (f) Michelin, R. A.;
Facchin, G.; Braga, D.; Sabatino, P. Organometallics 1986, 5, 2265.
Ylides as reducing agents: (g) Wagner, G.; Pakhomova, T. B.; Bokach,
́
2008, 1957. (l) Urriolabeitia, E. P. Dalton Trans. 2008, 5673.
(m) Urriolabeitia, E. P. Top. Organomet. Chem. 2010, 30, 15.
(19) Selected examples of C-ylides: (a) Hoover, J. F.; Stryker, J. M.
Organometallics 1988, 7, 2082. (b) Pandolfo, L.; Paiaro, G.; Dragani, L.
K.; Maccato, C.; Bertani, R.; Facchin, G.; Zanotto, L.; Ganis, P.; Valle,
G. Organometallics 1996, 15, 3250. (c) Vicente, J.; Chicote, M. T.;
Guerrero, R.; Jones, P. G. J. Am. Chem. Soc. 1996, 118, 699.
(d) Ferguson, G.; Li, Y.; McAlees, A. J.; McCrindle, R.; Xiang, K.
Organometallics 1999, 18, 2428. (e) Spannenberg, A.; Baumann, W.;
Rosenthal, U. Organometallics 2000, 19, 3991.
N. A.; Frausto da Silva, J. J. R.; Vicente, J.; Pombeiro, A. J. L.;
́
Kukushkin, V. Y. Inorg. Chem. 2001, 40, 1683. (h) Bokach, N. A.;
Selivanov, S. I.; Kukushkin, V. Y.; Vicente, J.; Haukka, M.; Pombeiro,
A. J. L. Organometallics 2002, 21, 3744.
(26) Selected general contributions: (a) Falvello, L. R.; Fernan
S.; Navarro, R.; Urriolabeitia, E. P. Inorg. Chem. 1996, 35, 3064.
(b) Falvello, L. R.; Fernandez, S.; Navarro, R.; Pascual, I.; Urriolabeitia,
E. P. J. Chem. Soc., Dalton Trans. 1997, 763. (c) Falvello, L. R.;
Fernandez, S.; Navarro, R.; Urriolabeitia, E. P. Inorg. Chem. 1997, 36,
1136. (d) Falvello, L. R.; Fernandez, S.; Navarro, R.; Rueda, A.;
Urriolabeitia, E. P. Inorg. Chem. 1998, 37, 6007. (e) Falvello, L. R.;
Fernandez, S.; Navarro, R.; Urriolabeitia, E. P. Inorg. Chem. 1999, 38,
́
dez,
́
́ ́
(20) Selected examples of O-, N-ylides: (a) Uson, R.; Fornies, J.;
Navarro, R.; Espinet, P.; Mendívil, C. J. Organomet. Chem. 1985, 290,
125. (b) Albanese, J. A.; Staley, D. L.; Rheingold, A.; Burmeister, J. L.
Inorg. Chem. 1990, 29, 2209. (c) Facchin, G.; Zanotto, L.; Bertani, R.;
Canovese, L.; Uguagliati, P. J. Chem. Soc., Dalton Trans. 1993, 2871.
(d) Soulivong, D.; Wieser, C.; Marcellin, M.; Matt, D.; Harriman, A.;
Toupet, L. J. Chem. Soc., Dalton Trans. 1997, 2257.
́
́
́
2455. (f) Falvello, L. R.; Llusar, R.; Margalejo, M. E.; Navarro, R.;
Urriolabeitia, E. P. Organometallics 2003, 22, 1132. (g) Falvello, L. R.;
(21) Selected examples of C,X-chelating ylides: (a) Schmidbaur, H.;
Deschler, U.; Milewski-Mahrla, B. Angew. Chem., Int. Ed. Engl. 1981,
20, 586. (b) Uson, R.; Laguna, A.; Laguna, M.; Lazaro, I.; Jones, P. G.
́ ́
́ ́ ́
Gines, J. C.; Carbo, J. J.; Lledos, A.; Navarro, R.; Soler, T.;
Urriolabeitia, E. P. Inorg. Chem. 2006, 45, 6803. (h) Aguilar, D.;
Contel, M.; Navarro, R.; Urriolabeitia, E. P. Organometallics 2007, 26,
4604. (i) Aguilar, D.; Contel, M.; Navarro, R.; Soler, T.; Urriolabeitia,
E. P. J. Organomet. Chem. 2009, 694, 486. (j) Aguilar, D.; Contel, M.;
Urriolabeitia, E. P. Chem.Eur. J. 2010, 16, 9287.
Organometallics 1987, 6, 2326. (c) Vicente, J.; Chicote, M. T.; Lagunas,
M. C. Inorg. Chem. 1993, 32, 3748. (d) Viau, L.; Lepetit, C.;
Commenges, G.; Chauvin, R. Organometallics 2001, 20, 808.
(e) Zurawinski, R.; Donnadieu, B.; Mikolajczyk, M.; Chauvin, R.
Organometallics 2003, 22, 4810. (f) Vignolle, J.; Donnadieu, B.;
Bourissou, D.; Soleilhavoup, M.; Bertrand, G. J. Am. Chem. Soc. 2006,
128, 14810. (g) Vignolle, J.; Gornitzka, H.; Maron, L.; Schoeller, W.
W.; Bourissou, D.; Bertrand, G. J. Am. Chem. Soc. 2007, 129, 978.
(h) Canac, Y.; Lepetit, C.; Abdalilah, M.; Duhayon, C.; Chauvin, R. J.
Am. Chem. Soc. 2008, 130, 8046. (i) Zurawinski, R.; Lepetit, C.; Canac,
Y.; Mikolajczyk, M.; Chauvin, R. Inorg. Chem. 2009, 48, 2147.
(27) Specific studies on CH bond activation: (a) Falvello, L. R.;
Fernan
metallics 1998, 18, 5887. (b) Falvello, L. R.; Fernan
Llusar, R.; Navarro, R.; Urriolabeitia, E. P. Organometallics 2001, 20,
1424. (c) Gracia, C.; Marco, G.; Navarro, R.; Romero, P.; Soler, T.;
Urriolabeitia, E. P. Organometallics 2003, 22, 4910. (d) Aguilar, D.;
́
dez, S.; Navarro, R.; Rueda, A.; Urriolabeitia, E. P. Organo-
́
dez, S.; Larraz, C.;
Aragues, M. A.; Bielsa, R.; Serrano, E.; Navarro, R.; Urriolabeitia, E. P.
́
̈
Organometallics 2007, 26, 3541. (e) Bielsa, R.; Navarro, R.; Lledos
Urriolabeitia, E. P. Inorg. Chem. 2007, 46, 10133. (f) Aguilar, D.;
Aznarez, F.; Bielsa, R.; Falvello, L. R.; Navarro, R.; Urriolabeitia, E. P.
́
, A.;
(22) Selected examples of orthometalated ylides: (a) Illingsworth,
M. L.; Teagle, J. A.; Burmeister, J. L.; Fultz, W. C.; Rheingold, A. L.
Organometallics 1983, 2, 1364. (b) Vicente, J.; Chicote, M. T.;
Fernandez-Baeza, J. J. Organomet. Chem. 1989, 364, 407. (c) Onitsuka,
́
K.; Nishii, M.; Matsushima, Y.; Takahashi, S. Organometallics 2004, 23,
5630.
(23) Selected examples of chelating and bridging ylides and bis-
ylides: (a) Schmidbaur, H.; Adlkofer, J.; Buchner, W. Angew. Chem.,
Int. Ed. Engl. 1973, 12, 415. (b) Jandik, P.; Schubert, U.; Schmidbaur,
H. Angew. Chem., Int. Ed. Engl. 1982, 21, 73. (c) Schmidbaur, H.;
́
Organometallics 2007, 26, 6397. (g) Bielsa, R.; Navarro, R.; Soler, T.;
Urriolabeitia, E. P. Dalton Trans. 2008, 1203. (h) Bielsa, R.; Navarro,
R.; Soler, T.; Urriolabeitia, E. P. Dalton Trans. 2008, 1787. (i) Aguilar,
́
D.; Bielsa, R.; Contel, M.; Lledos, A.; Navarro, R.; Soler, T.;
Urriolabeitia, E. P. Organometallics 2008, 27, 2929. (j) Aguilar, D.;
Navarro, R.; Soler, T.; Urriolabeitia, E. P. Dalton Trans. 2010, 39,
10422. (k) Aguilar, D.; Fernandez, I.; Cuesta, L.; Yanez-Rodríguez, V.;
́
́
̃
Soler, T.; Navarro, R.; Urriolabeitia, E. P.; Lopez-Ortíz, F. J. Org. Chem.
́
2010, 75, 6452. (l) Aguilar, D.; Bielsa, R.; Soler, T.; Urriolabeitia, E. P.
Organometallics 2011, 30, 642.
Costa, T.; Milewski-Mahrla, B.; Kohler, F. H.; Tsay, Y.-H.; Kruger, C.;
̈
̈
Abart, J.; Wagner, F. E. Organometallics 1982, 1, 1266. (d) Vicente, J.;
Chicote, M. T.; Saura-Llamas, I.; Jones, P. G.; Meyer-Base, K.;
(28) Catalytic processes: (a) Larivee
B. J. Am. Chem. Soc. 2008, 130, 52. (b) Mousseau, J. J.; Larivee
́
, A.; Mousseau, J. J.; Charette, A.
̈
Erdbrugger, C. F. Organometallics 1988, 7, 997. (e) Raptis, R. G.;
́
, A.;
̈
Porter, L. C.; Emrich, R. J.; Murray, H. H.; Fackler, J. P. Jr. Inorg.
Charette, A. B. Org. Lett. 2008, 10, 1641. (c) Donohoe, T. J.;
Connolly, M. J.; Walton, L. Org. Lett. 2009, 11, 5562. (d) Xu, J.;
Cheng, G.; Su, D.; Liu, Y.; Wang, X.; Hu, Y. Chem.Eur. J. 2009, 11,
13105. (e) Mousseau, J. J.; Fortier, A.; Charette, A. B. Org. Lett. 2010,
12, 516. (f) Mousseau, J. J.; Bull, J. A.; Charette, A. B. Angew. Chem.,
Chem. 1990, 29, 4408. (f) Uson
J.; Jones, P. G. Angew. Chem., Int. Ed. Engl. 1991, 30, 198. (g) Men
L. A.; Jimenez, J.; Cerrada, E.; Mohr, F.; Laguna, M. J. Am. Chem. Soc.
́
, R.; Laguna, A.; Laguna, M.; Jimen
́
ez,
́
dez,
́
2004, 127, 852. (h) Canac, Y.; Duhayon, C.; Chauvin, R. Angew.
Chem., Int. Ed. 2007, 46, 6313.
Int. Ed. 2010, 49, 1115.
Orthopalladation of H5C6NNC(O)Ph:
(24) Structural and DFT studies on conformational preferences on
ylides: (a) Aitken, R. A.; Karodia, N.; Lightfoot, P. J. Chem. Soc., Perkin
(g) Dias, S. A.; Downs, A. W.; McWhinnie, W. R. Inorg. Nucl. Chem.
Lett. 1974, 10, 233. (h) Dias, S. A.; Downs, A. W.; McWhinnie, W. R.
J. Chem. Soc., Dalton Trans. 1975, 162.
Trans. 2 2000, 333. (b) Lledos
Inorg. Chem. 2001, 40, 4913. (c) Lledos
Urriolabeitia, E. P. Inorg. Chim. Acta 2004, 357, 1444. (d) Lledos
Carbo, J. J.; Navarro, R.; Serrano, E.; Urriolabeitia, E. P. Inorg. Chem.
2004, 43, 7622. (e) Serrano, E.; Valles, C.; Carbo, J. J.; Lledos, A.;
Soler, T.; Navarro, R.; Urriolabeitia, E. P. Organometallics 2006, 25,
4653. (f) Serrano, E.; Navarro, R.; Soler, T.; Carbo, J. J.; Lledos, A.;
Urriolabeitia, E. P. Inorg. Chem. 2009, 48, 6823.
(25) Addition of ylides to olefins: (a) Vicente, J.; Chicote, M. T.;
MacBeath, C.; Fernandez-Baeza, J.; Bautista, D. Organometallics 1999,
́
, A.; Carbo,
́
J. J.; Urriolabeitia, E. P.
J. J.; Navarro, R.;
, A.;
, A.; Carbo,
́
(29) General routes: (a) Phillips, W. G.; Ratts, K. W. J. Org. Chem.
1970, 35, 3144. (b) King, L. C. J. Am. Chem. Soc. 1944, 66, 894.
(c) Krohnke, F. Chem. Ber. 1935, 68, 1177. (d) Henrick, C. A.; Ritchie,
E.; Taylor, W. C. Aust. J. Chem. 1967, 20, 2441. Specific synthesis of
the ylides. (2a): (e) Dega-Szafran, Z.; Schroeder, G.; Szafran, M.;
Szwajca, A.; Leska, B.; Lewandowska, M. J. Mol. Struct. 2000, 555, 31.
See also ref 29d. (2b): (f) Kendurkar, P. S.; Tewari, R. S. J. Chem. Eng.
Data 1974, 19, 184. (2c): (g) Nguyen Van, T.; Kesteleyn, B.; De
Kimpe, N. Tetrahedron 2001, 57, 4213. (h) Aldersley, M. F.; Christi, S.
H.; Dean, F. M.; Douglas, M. E.; Ennis, D. S. J. Chem. Soc., Perkin
Trans 1 1990, 2163. (2d): See ref 29a. (1f): (i) Jemison, R. W.;
Mageswaran, S.; Ollis, W. D.; Sutherland, I. O.; Thebtaranonth, Y. J.
́
́
́
́
́
́
́
́
́
18, 2677. (b) Vicente, J.; Chicote, M. T.; MacBeath, C.; Jones, P. G.
Organometallics 2003, 22, 1843. Addition of ylides to nitriles and
́
isocyanides: (c) Vicente, J.; Chicote, M. T.; Fernandez-Baeza, J.;
403
dx.doi.org/10.1021/om201001c | Organometallics 2012, 31, 394−404

Organometallics
Article
Chem. Soc., Perkin Trans. 1 1981, 1154. (j) Pine, S. H.; Cheney, J. J.
Org. Chem. 1975, 40, 870. (2g): (k) Tsuge, O.; Kanemasa, S.;
Takenaka, S. Bull. Chem. Soc. Jpn. 1983, 56, 2073. (l) McGuinness, D.
S.; Cavell, K. J. Organometallics 2000, 19, 741. (2h): ref 29i. (2i):
(m) Bradsher, C. K.; Beavers, L. E. J. Am. Chem. Soc. 1955, 77, 453.
See also ref 28e. (n) Synthesis of the indolizine (3): Nayler, J. H. C.
The Patent Office of London GB1174124(A), 1969.
(30) Kawafune, I.; Matsubayashi, G.-E. Inorg. Chim. Acta 1983, 70, 1.
(31) CrysAlis RED, version 1.171.27p8; Oxford Diffraction Ltd.:
Oxford, U. K., 2005.
(32) Sheldrick, G. M. SADABS: Empirical Absorption Correction
Program; Gottingen University; Gottingen, Germany, 1996.
̈
̈
(33) Sheldrick, G. M. Acta Crystallogr., Sect. A. 1990, A46, 467.
(34) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
404
dx.doi.org/10.1021/om201001c | Organometallics 2012, 31, 394−404