Room-temperature isolation of palladium(II) organocarbonyl intermediates in the synthesis of eight-membered lactams after alkyne/CO sequential insertions

Article abstract of DOI:10.1021/om301241n

The dinuclear complexes [Pd(C^{^}N)(μ-X)]₂ (C ^{^}N = C,N-C(Ph)=C(R′)ArCH₂CR₂NH ₂-2; Ar = C₆H₄, C₆H ₂(OMe)₂-4,5; R = H, Me; R′ = Ph, CO₂Me, Me; X = Cl, Br), arising from the monoinsertion of internal alkynes into the Pd-C bond of ortho-palladated phentermine or homoveratrylamine, react with CO at room temperature to afford the neutral mononuclear organocarbonyl complexes [Pd(C^{^}N)X(CO)]. When the reactions with CO are carried out in the presence of TlOTf, the triflato complexes [Pd(C^{^}N)(OTf)(CO)] are obtained. These organo-carbonyl complexes show an unexpected stability, in spite of containing CO and a σ-alkenyl ligand in mutually cis positions, and represent real intermediates in the insertion reactions of CO into the Pd-C bond. Indeed, they undergo decomposition under the proper conditions, behaving as CO-releasing molecules or yielding Pd(0) and the corresponding dihydro-3-benzazocinones, resulting from a C-N coupling process. Crystal structures of each type of compound have been determined by X-ray diffraction studies.

Full text of DOI:10.1021/om301241n

Article
pubs.acs.org/Organometallics
Room-Temperature Isolation of Palladium(II) Organocarbonyl
Intermediates in the Synthesis of Eight-Membered Lactams after
Alkyne/CO Sequential Insertions
†
†
,†
‡
́
́
Jose-Antonio Garcıa-Lopez, Marıa-Jose Oliva-Madrid, Isabel Saura-Llamas,* Delia Bautista,
́
́
́
and Jose Vicente*,†
́
†
́
́
́
Grupo de Quımica Organometalica, Departamento de Quımica Inorganica, Facultad de Quımica, Universidad de Murcia, E-30071
́ ́
Murcia, Spain
‡SAI, Universidad de Murcia, E-30071 Murcia, Spain
S
* Supporting Information
ABSTRACT: The dinuclear complexes [Pd(C∧N)(μ-X)]2
(C∧N = C,N-C(Ph)C(R′)ArCH2CR2NH2-2; Ar = C6H4,
C6H2(OMe)2-4,5; R = H, Me; R′ = Ph, CO2Me, Me; X = Cl,
Br), arising from the monoinsertion of internal alkynes into
the Pd−C bond of ortho-palladated phentermine or
homoveratrylamine, react with CO at room temperature to
afford the neutral mononuclear organocarbonyl complexes
[Pd(C∧N)X(CO)]. When the reactions with CO are carried
out in the presence of TlOTf, the triflato complexes
[Pd(C∧N)(OTf)(CO)] are obtained. These organo-carbonyl complexes show an unexpected stability, in spite of containing
CO and a σ-alkenyl ligand in mutually cis positions, and represent real intermediates in the insertion reactions of CO into the
Pd−C bond. Indeed, they undergo decomposition under the proper conditions, behaving as CO-releasing molecules or yielding
Pd(0) and the corresponding dihydro-3-benzazocinones, resulting from a C−N coupling process. Crystal structures of each type
of compound have been determined by X-ray diffraction studies.
In this paper, we describe (1) the synthesis of eight-
membered palladacycles through the regioselective mono-
insertion of symmetrical and nonsymmetrical alkynes into the
Pd−C bond of ortho-palladated phenethylamines, (2) the
isolation of neutral organocarbonyl Pd(II) complexes contain-
ing CO and an alkenyl ligand coordinated to the metal in cis
positions, and (3) the decomposition of the organometallic
complexes to afford the corresponding dihydro-3-benzazoci-
nones.
INTRODUCTION
■
It is well-known that organocarbonyl complexes of Pd(II) are
difficult to isolate because the organic groups bonded to Pd(II)
are prone to undergo migratory insertion reactions leading to
the formation of acyl complexes1−9 or organic derivatives upon
depalladation.7,10−13 This process constitutes the key step in
many palladium-catalyzed organic carbonylations14 and alkene/
CO copolymerizations.4,15,16 Usually, the [Pd(R)(CO)(L)2]
complexes can only be detected in NMR experiments at low
temperatures3,17 or at high pressures of CO,18 unless the CO-
insertion process is somehow prevented. Therefore, only a few
palladium(II) organocarbonyl compounds have been isolated
so far, which include (1) methyl complexes, isolated at low
temperature,16,19 (2) aryl complexes with the R group trans to
the CO ligand,20,21 (3) complexes with very strong R−Pd
bonds, for example, those in which R is a very electronegative
alkyl or aryl group,21−26 (4) rigid five-membered27−29 or pincer
palladacycles,2,9,30,31 and (5) complexes with bridging carbonyl
ligands.32 Among them, only a few have been characterized by
X-ray diffraction studies so far.9,16,19,23,29,31,33 Very recently, our
group has reported the synthesis of eight-membered
benzolactams through the insertion of CO into the Pd−C
bond of eight-membered palladacycles arising from the
monoinsertion of alkenes into ortho-palladated phenethyl-
amines12 or monoinsertion of alkynes into ortho-palladated
amides.13
RESULTS AND DISCUSSION
■
Monoinsertion of Alkynes into the Pd−C Bond of Six-
Membered Palladacycles. The ortho-palladated complexes
[Pd{C,N-C6H2CH2CH2NH2-2-(MeO)2-4,5)}(μ-Br)]2 (A) and
[Pd(C,N-C6H4CH2CMe2NH2-2)(μ-Cl)]2 (B), derived from
homoveratrylamine and phentermine, respectively, reacted
with alkynes PhCCR′ to give dimeric complexes arising
from the monoinsertion of the alkyne into the Pd−C bond,
[Pd{C,N-C(Ph)C(R′)C6H2CH2CR2NH2-2-(OMe)2-4,5}(μ-
X)]2 (R = H, R′ = Ph (1a), CO2Me (2a), Me (3a), X = Br; R =
Me, R′ = Ph (1b), CO2Me (2b), Me (3b), X = Cl), along with,
when R ≠ Ph, their regioisomers [Pd{C,N-C(R′)C(Ph)-
C6H2CH2CR2NH2-2-(OMe)2-4,5}(μ-X)]2 (R = H, R′ =
Received: December 20, 2012
Published: February 5, 2013
© 2013 American Chemical Society
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CO2Me (2′a), Me (3′a), X = Br; R = Me, R′ = CO2Me (2′b),
Me (3′b), X = Cl) (Scheme 1). The ratios of both isomers
Scheme 1. Synthesis of Eight-Membered Palladacycles 1−3
Figure 1. Thermal ellipsoid plot (50% probability) of 1b·1/2C6H14
along with the labeling scheme. The solvent molecule and hydrogen
atoms attached to carbon have been omitted for clarity. Selected bond
lengths (Å) and angles (deg): Pd(1)−Cl(1) = 2.3436(7), Pd(1)−
Cl(2) = 2.4754(7), Pd(1)−N(1) = 2.080(2), Pd(1)−C(8) = 1.976(3),
Pd(2)−Cl(1) = 2.4671(6), Pd(2)−Cl(2) = 2.3575(7), Pd(2)−N(2) =
2.081(2), Pd(2)−C(48) = 1.975(2); Cl(1)−Pd(1)−Cl(2) = 87.11(2),
Cl(2)−Pd(1)−N(1) = 96.03(7), N(1)−Pd(1)−C(8) = 86.32(10),
C(8)−Pd(1)−Cl(1) = 90.54(8), Cl(1)−Pd(2)−N(2) = 93.18(6),
N(2)−Pd(2)−C(48) = 87.63(10), C(48)−Pd(2)−Cl(2) = 92.20(7),
Cl(2)−Pd(2)−Cl(1) = 86.99(2).
(x:x′) ranged from 2.5 to 8.3 (Scheme 1). These ratios were
not affected when the reactions were carried out at low
temperature (0 °C). At high temperature (CHCl3, 60 °C),
diinsertion processes took place and complicated mixtures were
obtained. The major isomers 2b and 3b could be separated
from the mixtures by fractional recrystallization. However, the
mixtures 2a + 2′a and 3a + 3′a could not be separated by either
crystallization or chromatography, although they could be used
as starting materials for subsequent reactions.
Several NOESY experiments were carried out to determine
the regiochemistry of the inserted alkyne in complexes 2a,b and
3a,b. For complexes 3a,b, the 2D spectra clearly showed
correlations between the Me group of inserted 1-phenyl-1-
propyne and both H6 (Chart 1) and the o-H of the Ph ring,
supporting the proposed structures. In the case of complexes
2a,b, arising from the insertion of methyl phenylpropiolate, the
NOESY spectra did not offer relevant information about the
regiochemistry. Nevertheless, the geometry observed in the X-
ray crystal structures of 2b, the mononuclear complex 8b, and
the organic derivative 12b (see below) was in agreement with
the proposed structures. The observed regioselectivity was also
in agreement with that reported in the literature for the
insertion of nonsymmetrical alkynes into the Pd−C bond of
other palladacycles.8,13,34,35
Figure 2. Thermal ellipsoid plot (50% probability) of complex 2b
along with the labeling scheme. Hydrogen atoms attached to carbon
atoms have been omitted for clarity. Selected bond lengths (Å) and
angles (deg): Pd(1)−Cl(1) = 2.4406(11), Pd(1)−Cl(1A) =
2.3354(11), Pd(1)−N(1) = 2.058(4), Pd(1)−C(8) = 1.958(4);
Cl(1)−Pd(1)−Cl(1A) = 87.53(4), Cl(1)−Pd(1)−N(1) = 94.78(11),
N(1)−Pd(1)−C(8) = 88.03(15), C(8)−Pd(1)−Cl(1A) = 89.60(11).
perfect square-planar environment (mean deviation of the
plane Pd(1)−N(1)−C(8)−Cl(1)−Cl(1A) 0.0155 Å), becom-
ing part of an eight-membered ring that adopts a boat-chair
conformation. The structure confirms the proposed regiochem-
istry for the insertion reaction of methyl phenylpropiolate. The
molecules of complex 2b are associated through N−H···O
hydrogen bonds to give double chains along the a axis (see the
Supporting Information).
Although monoinserted compounds derived from the
reactions of arylpalladium complexes with internal alkynes
RCCR′ (mainly R/R′ = Ph, CF3, CO2Me) have been
isolated,6,8,13,34,36the synthesis of complexes 1−3 was surpris-
ing, as we had not been able to obtain monoinserted derivatives
The crystal structures of complexes 1b·1/2C6H14 and 2b have
been solved by X-ray diffraction studies. In 1b·1/2C6H14 (Figure
1), the palladium atoms are in a very slightly distorted square-
planar environment (mean deviation of the planes: Pd(1)−
N(1)−C(8)−Cl(1)−Cl(2), 0.0182 Å; Pd(2)−N(2)−C(48)−
Cl(1)−Cl(2), 0.0159 Å) and they form part of eight-membered
rings that adopt boat-chair and twist-boat-chair conformations.
The coordination planes of both palladium atoms form an angle
of 32.9°.
The crystal structure of complex 2b (Figure 2) shows a
centrosymmetric molecule. The palladium atom is in an almost
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from the reaction of similar palladacycles containing primary
benzylamines and symmetrical alkynes RCCR (R = Et, Ph).8
For instance, the reaction of palladacycles derived from α-
methylbenzylamine26 or 4-X-benzylamine (X = OMe, F, Cl,
NO2)8 with RCCR (Pd/alkyne = 1/1; R = Et, Ph) gave
mixtures of the starting materials and the di-inserted species,
whereas ortho-palladated phenethylamine derivatives afforded
uncharacterized mixtures. Recently, Urriolabeitia et al. have
described a seven-membered palladacycle derived from the
insertion of diphenylacetylene into the Pd−C bond of
cyclometalated methyl (R)-phenylglycinate.11 Therefore, com-
plexes 1−3 are the first of this kind obtained from a six-
membered palladacycle arising from an arylalkylamine.
In their IR spectra, complexes 7b and 8b exhibit strong
sulfonyl absorptions at 1302 and 1315 cm−1, respectively, near
the values reported in organometallic triflato complexes.38,39
The crystal structure of complex 8b (see below) confirmed this
feature. Although for complex 9b the ν(SO) band appears at
1287 cm−1 and could not be clearly assigned to an ionic or a
coordinated TfO group, we propose for it a structure similar to
that found for 8b. Additionally, complexes 7b−9b behaved as
nonconductors when they were dissolved in 1,2-dichloroethane
(molar conductivities 1−3 Ω−1 mol−1 cm2), although their
acetone solutions showed conductivities characteristic of 1/1
electrolytes (104−120 Ω−1 mol−1 cm2),40 likely because of the
replacement of the coordinated triflate by a solvent
molecule.41,42
Synthesis and Structure of Organocarbonyl Com-
plexes of Pd(II) 4−9. The reactions of dimers 1−3 with CO
in CH2Cl2 at room temperature afforded the surprisingly stable
organocarbonyl complexes 4−6 (Scheme 2). Even more
The carbonyl complexes 4−6 are stable in the solid state and
could be stored at room temperature for weeks. However,
complexes 4 and 6 decompose at room temperature in CH2Cl2
or CHCl3 solutions in the absence of a CO atmosphere to give
the lactam arising from the C−N coupling (Scheme 3; molar
Scheme 2. Synthesis of Carbonyl Complexes 4−9
Scheme 3. Decomposition of Complexes 4−9 in Solution
a
and Synthesis of Dihydro-3-benzazocinones 10−12
striking was that adding TlOTf to solutions of the dimers 1b
and 2b in acetone and bubbling CO through the resulting
suspensions afforded the triflato complexes 7b and 8b,
respectively, as isolable and stable species. The presence of
oxygen-containing substituents in the palladacycle fragments
(such as OMe or CO2Me) prevented us from using AgOTf
instead of the more toxic TlOTf, because silver(I) is easily
coordinated by O-donor groups. However, the corresponding
complex 9b is unstable, preventing us from recrystallizing it to
obtain an analytically pure sample. Analogous reactions with
1a−3a afforded a mixture of complex 4a and the corresponding
lactam (see below) or intractable mixtures.
The ν(CO) band in the IR spectrum of complexes 4−9
appears in the region 2095−2139 cm−1, which unambiguously
shows the terminal coordination of the carbon monoxide to the
palladium atom. These values were lower than that of ν(CO) in
the free ligand (2143 cm−1), which indicates the contribution of
the π-back-donation component to the Pd−CO bond.37 In
complexes 7b−9b, the replacement of the chloro ligand by
triflato (a weaker donor) strengthens the σ-donation
component of the Pd−CO bond and weakens the π-back-
bonding; therefore, ν(CO) is shifted to higher energies in the
IR spectra (4b−6b, 2104−2111 cm−1; 7b−9b, 2120−2139
cm−1; Δ = 16−28 cm−1).
a
Legend: (i) synthesis at room temperature of 10a,b and 12a,b from
4a,b and 6a,b, respectively; (ii) synthesis of 10a,b and 11a,b by
heating at 65 °C under CO (1 atm) CHCl3 solutions of 1a,b (+2 equiv
of Et3N), 2a (+2 equiv of Et3N), and 2b, respectively; (iii) synthesis of
12a,b by treating 3a,b at room temperature under CO (1 atm) + 2
equiv of Et3N.
ratio, time (h): 4a/10a, 2.7 (24); 4b/10b, 8 (24); 6a/12a, 2.0
(0.25); 6b/12b, 2.0 (0.25)). Under these conditions, 5a (R′ =
CO2Me) remained unchanged after 24 h, while 5b slowly
released carbon monoxide, regenerating the dimeric chloro-
bridged palladacycle 2b (Scheme 3; ratio 5b/2b 2, after 24 h).
Therefore, complex 5b behaves as a carbon monoxide releasing
molecule (CO-RM). This behavior has been found by other
authors in reported halo−carbonyl complexes.20,27,29 CO-RMs,
especially metal complexes,43,44 have attracted increasing
interest because of the therapeutic effects of CO in treatments
against organ transplant rejection or rheumatoid arthritis.44,45
The different behaviors of complexes 4−6 might be
attributed to the electronic effect of the R′ substituent: an
electron-releasing group (6, R′ = Me) facilitates the reductive
coupling, while the presence of a strong electron-withdrawing
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group (5, R′ = CO2Me) strengthens the Pd−C bond
preventing the insertion step. Complexes 4 (R′ = Ph) have
an intermediate behavior.
The 1H NMR spectra of complexes 4−6 showed the
diastereotopic nature of the NH2 (4−6) and CH2 (4b−6b)
protons and the CMe2 methyl groups (4b−6b), likely due to
the stable conformation of the eight-membered ring, which
does not change on the NMR time scale at room temperature.
In the 13C NMR of complexes 4−6, the CO group appeared at
ca. 173 ppm (172.8−174.2 ppm), which is in agreement with
the relatively few available data for carbonyl complexes.18,24,26,29
For complexes 4−6, we proposed that the coordinated CO was
located cis to the alkenyl fragment, in agreement with the well-
established transphobia among C-donor ligands5,42,46 and the
X-ray crystal structure of the triflato derivative 8b (see below).
Additionally, the structures of the cis and trans isomers of the
complex 4b were optimized through DFT calculations, and the
cis isomer was 9.8 kcal/mol more stable than the trans isomer
Figure 3. X-ray thermal ellipsoid plot (50% probability) of 8b showing
the labeling scheme. Selected bond lengths (Å) and angles (deg):
Pd(1)−O(2) = 2.149(3), Pd(1)−N(1) = 2.081(3), Pd(1)−C(8) =
1.994(3), Pd(1)−C(13) = 1.909(4), C(13)−O(1) = 1.109(4); O(2)−
Pd(1)−N(1) = 84.24(11), N(1)−Pd(1)−C(8) = 90.89(13), C(8)−
Pd(1)−C(13) = 84.55(15), C(13)−Pd(1)−O(2) = 100.37(13),
Pd(1)−C(13)−O(1) = 173.0(4).
1
(see the Supporting Information). The H NMR spectra of
complexes 7b−9b show features similar to those of complexes
4b−6b, although the signals corresponding to one of the
protons of the NH2 group appeared more deshielded (0.3−0.7
ppm).
The isolated complexes 4−6 are unique, as they are stable
enough to be isolated at room temperature but, under the
appropriate conditions, undergo CO insertion to afford
carbonylated derivatives; that is, for them CO migratory
insertion is retarded but not prevented. Moreover, they do not
belong to any of the groups of stable carbonyl complexes
reported so far and mentioned above because (1) they contain
fluxional eight-membered palladacycles and, therefore, the
migratory insertion process is not sterically prevented and (2)
the alkenyl group, which is located cis to the coordinated CO, is
only moderately electron withdrawing and, therefore, the
migratory insertion process is not electronically precluded.
Their unexpected stability could arise from the steric hindrance
of the phenyl group on the carbon bonded to the metal that
may enhance the difficulty of this metalated group to migrate to
the coordinated CO. It is known that ligands with high steric
demand sometimes stabilize species that are otherwise
inaccessible or difficult to obtain.38 Most other reported
organo-carbonyl Pd(II) complexes either (1) did not
decompose to give carbonylated organic derivatives20−30,33,47
or (2) were only detectable at low temperatures.3,17,24 In an
NMR experiment, Jordan el at. has described the complex
[L2Pd{CH(CN)Et}(CO)]+ (L2 = CH2(N-Me-imidazol-2-yl)2),
which underwent slow reversible CO insertion to yield an
equilibrium mixture of the starting compound and the acyl
organometallic complex.18
oxygen atom. The palladium atom was in a slightly distorted
square planar environment (mean deviation of the plane
Pd(1)−N(1)−C(8)−C(13)−O(2) 0.0342 Å), and it formed
part of an eight-membered ring that adopted a boat-chair
conformation. The Pd−CO bond distance (1.909 Å) is
comparable with that found in other structurally characterized
monoaryl complexes of Pd(II) containing carbonyl ligands.23,29
The molecules of complex 8b are connected through a N−
H···O hydrogen bond to give zigzag chains along the b axis
which, in turn, are connected through three C−H···O hydrogen
bonds to give layers parallel to the plane (001) (see the
Supporting Information).
Synthesis and Structure of Dihydro-benzazocinones.
When CO was bubbled through solutions of complexes 1−3 in
CHCl3 and the mixtures were stirred at 60−65 °C (1, 2a) or
room temperature (3) under a CO atmosphere, the eight-
membered lactams 10−12 were isolated (Scheme 3). These
lactams can also be obtained by stirring CHCl3 solutions of
complexes 4−6 at 60−65 °C (4, 5a) or room temperature (6)
under a CO atmosphere.
It was not possible to obtain the benzazocinone 11b in pure
1
form, although it was detected in the reaction mixture by H
NMR, along with the palladacycle 2b, the carbonyl complex 5b,
and other unidentified components. Several attempts were
carried out to isolate it, via decomposition of the organo-
carbonyl complex intermediate 5b under a CO atmosphere and
different reaction conditions (stirring at room temperature for
various times, heating at 70 °C in CHCl3, adding NEt3).
All of the organic derivatives were characterized by IR and
NMR spectroscopy and elemental analysis or exact mass. In
addition, the crystal structures of dihydrobenzazocinones 10b
and 12b were solved by X-ray diffraction studies (Figures 4 and
5). In both cases, the eight-membered lactam rings adopted a
boat conformation. For both compounds, two adjacent
molecules were connected through N−H···O hydrogen bonds
to give dimers. For lactam 10b, these dimers were connected
through C−H···O hydrogen bonds to give layers parallel to the
plane (100) (see the Supporting Information).
There have only been reported a couple of other isolated
carbonyl palladium(II) complexes containing an alkenyl
chelated ligand.25,26 These palladacycles were obtained by the
insertion reaction of hexafluorobut-2-yne and dimethyl
acetylenedicarboxylate (DMAD) in palladated 1-methoxy-
naphth-8-yl and α-methylbenzylamine, respectively. In both
cases, the carbon α-bonded to the metal bears a strongly (CF3)
or a moderately (CO2Me) electron withdrawing group, which
undoubtedly contributed to the strengthening of the Pd−C
bond.
The crystal structure of complex 8b was solved by X-ray
diffraction studies (Figure 3), confirming (1) the mutually cis
positions of the alkenyl moiety and the carbonyl group and (2)
the coordination of the triflate group to the metal through an
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insertion of alkynes and CO, whose stability is not based on the
rigidity of the metalated ligand or on the electron-withdrawing
effects of their substituents but on the moderate steric
hindrance effect of a phenyl ring bonded to the metalated
carbon. The carbonyl complexes can behave as CO-releasing
molecules or undergo decomposition processes under the
proper conditions, leading to the formation of Pd(0) and
interesting eight-membered dihydro-3-benzazocinones. The
sequential insertion of alkynes and CO constitutes a new
method to achieve the synthesis of eight-membered N-
heterocycles, types of compounds which have attracted
increasing interest because of their pharmacological properties.
EXPERIMENTAL SECTION
Caution! Special precautions should be taken in handling thallium(I)
compounds, which are toxic.
■
General Procedures. Infrared spectra were recorded on a Perkin-
Elmer 16F-PC-FT spectrometer. C, H, N, and S analyses, conductance
measurements, and melting point determinations were carried out as
described elsewhere.48 Unless otherwise stated, NMR spectra were
recorded in CDCl3 on Bruker Avance 300 and 400 spectrometers.
Chemical shifts are referenced to TMS (1H and 13C{1H}). Signals in
Figure 4. X-ray thermal ellipsoid plot (50% probability) of 10b
showing the labeling scheme. Selected bond lengths (Å) and angles
(deg): C(1)−C(2) = 1.5474(15), C(2)−N(3) = 1.4759(14), N(3)−
C(4) = 1.3293(14), C(4)−C(5) = 1.5090(14), C(5)−C(6) =
1.3513(15), C(6)−C(6A) = 1.4868(15), C(6A)−C(10A) =
1.4079(15), C(10A)−C(1) = 1.5089(15); C(1)−C(2)−N(3) =
112.60(9), C(2)−N(3)−C(4) = 130.57(9), N(3)−C(4)−C(5) =
122.37(9), C(4)−C(5)−C(6) = 121.12(10), C(5)−C(6)−C(6A) =
122.32(10), C(6)−C(6A)−C(10A) = 119.98(9), C(6A)−C(10A)−
C(1) = 120.64(10), C(10A)−C(1)−C(2) = 116.98(9).
1
the H and 13C NMR spectra of all complexes were assigned with the
help of HMQC and HMBC techniques. Mass spectra and exact masses
were recorded on an AUTOSPEC 5000 VG mass spectrometer.
Reactions were carried out at room temperature without special
precautions against moisture unless otherwise stated.
The complexes [Pd(C,N-C6H2(CH2)2NH2-2-(MeO)2-4,5)(μ-Br)]2
(A) and [Pd(C,N-C6H4(CH2CMe2NH2-2)(μ-Cl)]2 (B) were prepared
as previously reported.48,49 Diphenylacetylene, 1-phenyl-1-propyne,
and NEt3 (Sigma-Aldrich), methyl phenylpropiolate (Lancaster), CO
(Air Products), and Na2CO3 (Baker) were used as received. TlOTf
was prepared by reaction of Tl2CO3 and HTfO (1/2) in water and
recrystallized from acetone/Et2O. Chart 1 gives the numbering
schemes for the new palladacycles and the organic derivatives.
Chart 1. Numbering Schemes for the Eight-Membered
Palladacycles and the Dihydro-3-benzazocinones
Figure 5. X-ray thermal ellipsoid plot (50% probability) of 12b
showing the dimer formed through hydrogen-bond interactions, along
with the labeling scheme. Hydrogen atoms attached to carbon atoms
have been omitted for clarity. Details (including symmetry operators)
are given in the Supporting Information. Selected bond lengths (Å)
and angles (deg): C(1)−C(7) = 1.4920(17), C(7)−C(8) =
1.3445(17), C(8)−C(9) = 1.5077(16), C(9)−N(1) = 1.3348(15),
N(1)−C(10) = 1.4752(15), C(10)−C(11) = 1.5501(16), C(11)−
C(2) = 1.5042(17), C(2)−C(1) = 1.4092(17); C(1)−C(7)−C(8) =
121.18(11), C(7)−C(8)−C(9) = 120.66(11), C(8)−C(9)−N(1) =
121.85(10), C(9)−N(1)−C(10) = 130.76(10), N(1)−C(10)−C(11)
= 113.05(10), C(10)−C(11)−C(2) = 115.42(10), C(11)−C(2)−
C(1) = 119.78(11), C(2)−C(1)−C(7) = 119.88(11).
Synthesis of 1a. Diphenylacetylene (97 mg, 0.546 mmol) was
added to a suspension of palladacycle A (200 mg, 0.273 mmol) in
CH2Cl2 (20 mL), and the mixture was stirred for 2 h. The suspension
was filtered, and the solid was washed with Et2O (2 × 5 mL) and air-
dried to afford complex 1a as a yellow solid (257 mg). Yield: 265 mg,
0.243 mmol, 89%. Mp: 245 °C. Anal. Calcd for C48H48Br2N2O4Pd2
(1089.568): C, 52.91; H, 4.44; N, 2.57. Found: C, 52.94; H, 4.49; N,
1
2.62. IR (cm−1): ν(NH) 3310 m, 3255 m. H NMR (400.91 MHz,
DMSO-d6): δ 2.73−2.94 (m, 4 H, 1 H of CH2N + 2 H of CH2Ar + 1
CONCLUSIONS
We have prepared a family of neutral halo− and triflato−
organocarbonyl Pd(II) complexes derived from the sequential
■
H of NH2), 3.21 (br s, 1 H, 1 H of CH2N), 3.62 (s, 3 H, MeO), 3.81
2
(s, 3 H, MeO), 4.25 (br d, 1 H, NH2, JHH = 9.6 Hz), 6.55 (s, 1 H,
H6), 6.82 (d, 2 H, o-H, Ph, 3JHH = 7.2 Hz), 6.96−7.03 (m, 3 H, 1 H of
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p-H + 2 H of m-H, Ph), 7.04 (s, 1 H, H3), 7.13 (t, 1 H, p-H, Ph, 3JHH
= 7.2 Hz), 7.20 (t, 2 H, m-H, Ph, 3JHH = 7.2 Hz), 7.34 (d, 2 H, o-H, Ph,
3JHH = 7.2 Hz). 13C{1H} NMR (75.45 MHz, DMSO-d6): δ 33.2 (s,
CH2Ar), 48.0 (s, CH2N), 55.3 (s, MeO), 55.7 (s, MeO), 112.0 (s, CH,
C6), 113.5 (s, CH, C3), 125.4 (s, p-CH, Ph), 125.5 (s, p-CH, Ph),
127.5 (s, m-CH, Ph), 127.8 (s, o-CH, Ph), 128.4 (s, m-CH, Ph), 128.7
(s, o-CH, Ph), 132.9 (s, C2), 135.7 (s, C7), 137.7 (s, C1), 140.4 (s, i-
C, Ph), 144.4 (s, i-C, Ph), 146.6 (s, C5), 147.7 (s, C4), 154.8 (s, C-
Pd).
was filtered, and the solid was washed with n-pentane (2 × 5 mL) and
air-dried to give the complex 1b as a yellow solid. Yield: 420 mg, 0.448
mmol, 87%. Dec pt: 200 °C. Anal. Calcd for C48H48Cl2N2Pd2
(936.668): C, 61.55; H, 5.16; N, 2.99. Found: C, 61.17; H, 5.45; N,
2.95. IR (cm−1): ν(NH) 3309 w, 3202 w. The NMR data correspond
to a mixture of cisoid and transoid isomers. 1H NMR (400.91 MHz): δ
1.27−1.58 (br and overlapped singlets, CMe2 groups), 2.29 (br d, 1 H,
NH2, 2JHH = 8.0 Hz), 2.51 (br s, 1 H, NH2), 2.74 (d, 1 H, CH2Ar, 2JHH
2
= 14.0 Hz), 2.97 (d, 1 H, CH2Ar, JHH = 13.6 Hz), 6.72 (br m, 2 H,
Ph), 6.93−7.48 (m, 12 H, Ar + Ph). 13C{1H} NMR (75.45 MHz): δ
27.2 (s, Me, CMe2), 27.3 (s, Me, CMe2), 35.4 (br s, Me, CMe2), 44.5
(s, CH2Ar), 44.6 (s, CH2Ar), 56.4 (s, CMe2), 125.4 (s, CH), 125.5 (s,
CH), 126.0 (s, CH), 126.1 (s, CH), 127.2 (s, CH), 128.1 (br s, CH),
128.5 (br s, CH), 128.8 (s, CH), 129.0 (s, CH), 129.2 (s, CH), 130.7
(br s, CH), 131.0 (br s, CH), 131.4 (s, CH), 136.0 (s, C), 138.2 (br s,
C), 139.4 (br s, C), 139.7 (s, C), 143.5 (br s, C), 143.7 (s, C), 143.9
(br s, C), 145.6 (br s, C), 145.8 (br s, C). Single crystals of
1b·1/2C6H14 suitable for an X-ray diffraction study were obtained by
slow diffusion of n-hexane into a solution of 1b in CHCl3.
Synthesis of 2a and 2′a. Methyl phenylpropiolate (0.08 mL,
0.546 mmol) was added to a suspension of palladacycle A (200 mg,
0.273 mmol) in CH2Cl2 (20 mL), and the mixture was stirred for 1 h.
Formation of a small amount of palladium(0) was observed. The
resulting mixture was filtered through a plug of Celite, and the solvent
was removed from the filtrate. The residue was vigorously stirred in
Et2O (30 mL), and the yellow suspension was filtered, washed with
Et2O (2 × 5 mL), and air-dried to afford a mixture of regioisomers 2a
+ 2′a (ratio ca. 2.5/1, by 1H NMR). Yield: 200 mg, 0.198 mmol, 72%.
Anal. Calcd for C40H44Br2N2O8Pd2 (1053.446): C, 45.61; H, 4.21; N,
2.66. Found: C, 45.62; H, 4.11; N, 2.78. IR (cm−1): ν(NH) 3310 w,
Synthesis of 2b. A solution of methyl propiolate (154 μL, 1.04
mmol) in CH2Cl2 (5 mL) was added dropwise to a solution of
palladacycle B (300 mg, 0.517 mmol) in CH2Cl2 (15 mL), and the
resulting solution was stirred for 3 h. The solvent was removed. The
1H NMR spectrum of the residue corresponded to a mixture of the
two regioisomers 2b + 2′b (ratio ca. 8/1). Acetone (3 mL) was added
to the residue, the suspension was filtered, and the solid was washed
with a acetone/Et2O mixture (1/4; 5 mL) and air-dried to afford the
complex 2b as a yellow solid. Yield: 325 mg, 0.361 mmol, 70%. Dec pt:
220 °C. Anal. Calcd for C40H44Cl2N2O4Pd2 (900.546): C, 53.35; H,
4.92; N, 3.11. Found: C, 52.96; H, 5.16; N, 3.07. IR (cm−1): ν(NH)
1
3252 w; ν(CO2R) 1695 s. H NMR (400.91 MHz, DMSO-d6): 2a, δ
2.66 (m, 1 H, CH2Ar), 2.75−2.89 (m, 2 H, 1 H of CH2Ar + 1 H of
CH2N), 3.03 (m, 1 H, NH2), 3.15−3.19 (m, 1 H, CH2N), 3.30 (s, 3
H, MeO), 3.72 (s, 3 H, MeO), 3.80 (s, 3 H, MeO), 4.27 (br d, 1 H,
NH2, 2JHH = 10.8 Hz), 6.74 (s, 1 H, H6), 7.00 (s, 1 H, H3), 7.22 (m, 1
H, p-H, Ph), 7.29 (t, 2 H, m-H, Ph, 3JHH = 7.2 Hz), 7.37 (d, 2 H, o-H,
Ph, 3JHH = 7.2 Hz); 2′a (selected data), δ 3.60 (s, 3 H, MeO), 3.61 (s,
3 H, MeO), 3.79 (s, 3 H, MeO), 6.53 (s, 1 H, H6), 7.03 (s, 1 H, H3).
13C{1H} NMR (100.81 MHz, DMSO-d6): 2a, δ 32.9 (s, CH2Ar), 48.0
(s, CH2N), 50.7 (s, MeO), 55.8 (s, MeO), 55.8 (s, MeO), 112.3 (s,
CH, C6), 113.6 (s, CH, C3), 125.6 (s, p-CH, Ph), 125.8 (s, m-CH,
Ph), 127.1 (s, m-CH, Ph), 128.0 (s, o-CH, Ph), 128.1 (s, o-CH, Ph),
128.5 (s, C7), 133.1 (s, C2), 133.5 (s, C1), 144.7 (s, i-C, Ph), 146.3 (s,
C5), 148.1 (s, C4), 163.0 (s, CO), 176.8 (C−Pd); 2′a (selected data),
δ 51.5 (s, MeO), 55.5 (s, MeO), 55.6 (s, MeO), 111.0 (s, CH, C6),
113.5 (s, CH, C3).
1
3297 w, 3239 w; ν(CO2R) 1698 s. H NMR (400.91 MHz, DMSO-
d6): δ 1.23 (s, 3 H, Me, CMe2), 1.43 (s, 3 H, Me, CMe2), 2.33 (br d, 1
H, NH2, 2JHH = 11.6 Hz), 2.63 (d, 1 H, CH2Ar, 2JHH = 14.0 Hz), 2.93
(d, 1 H, CH2Ar, 2JHH = 14.0 Hz), 3.28 (s, 3 H, OMe), 4.32 (br d, 1 H,
2
NH2, JHH = 11.6 Hz), 7.23−7.27 (m, 2 H, H of C6H4 + p-H of Ph),
7.03−7.37 (m, 7 H, 3 H of C6H4 + 4 H of Ph). 13C{1H} NMR (100.81
MHz, DMSO-d6): δ 27.5 (s, Me, CMe2), 33.5 (s, Me, CMe2), 44.1 (s,
CH2Ar), 50.8 (s, OMe), 56.6 (s, CMe2), 125.3 (s, o-CH, Ph), 125.7 (s,
CH, C6H4), 126.1 (s, p-CH, Ph), 126.4 (s, CH, C6H4), 128.2 (s, m-
CH, Ph), 129.1 (s, C7), 129.2 (s, CH, C6H4), 132.4 (s, CH, C3), 137.3
(s, C2), 141.8 (s, C1). 144.4 (s, i-C, Ph), 162.9 (s, CO), 175.8 (s, C−
Pd). Selected 1H NMR data of the minor isomer 2′b from the mixture
(300.1 MHz, DMSO-d6): δ 1.26 (s, 3 H, Me, CMe2), 1.35 (s, 3 H, Me,
Synthesis of 3a and 3′a. 1-Phenyl-1-propyne (0.05 mL, 0.409
mmol) was added to a suspension of palladacycle A (150 mg, 0.205
mmol) in CH2Cl2 (20 mL), and the mixture was stirred for 1 h.
Formation of a small amount of palladium(0) was observed. The
resulting mixture was filtered through a plug of Celite, and the solvent
was removed from the filtrate. The residue was vigorously stirred in
́
Et2O (30 mL), the suspension was filtered, and the yellow solid was
2
CMe2), 2.74 (d, 1 H, CH2Ar, JHH = 16.4 Hz), 2.82 (d, 1 H, CH2Ar,
washed with Et2O (2 × 5 mL) and air-dried to afford a first crop of a
mixture of regioisomers 3a + 3′a (ratio ca. 5/1; 142 mg). The filtrate
was concentrated to ca. 2 mL, and n-pentane (20 mL) was added. The
suspension was filtered, and the yellow solid was washed with n-
pentane (2 × 5 mL) and air-dried to afford a second crop of a mixture
of regioisomers 3a + 3′a (ratio ca. 5/1; 26 mg). Yield: 168 mg, 0.174
mmol, 85%. Anal. Calcd for C38H44Br2N2O4Pd2 (965.426): C, 47.28;
H, 4.59; N, 2.90. Found: C, 47.14; H, 4.67; N, 2.89. IR (cm−1): ν(NH)
2JHH = 16.0 Hz), 3.63 (s, OMe), 4.35 (br d, partially obscured by the
resonance of the isomer 2b, 1 H, NH2), 6.97 (d, 2 H, o-H, Ph, 3JHH
=
7.2 Hz), 6.98 (d, 1 H, C6H4, 3JHH = 7.2 Hz). Single crystals suitable for
an X-ray diffraction study were obtained by slow diffusion of n-pentane
into a solution of 2b in CH2Cl2.
Synthesis of 3b. A solution of 1-phenylpropyne (128 μL, 1.02
mmol) in CH2Cl2 (5 mL) was added dropwise to a solution of
palladacycle B (300 mg, 0.517 mmol) in CH2Cl2 (15 mL), and the
resulting mixture was stirred for 4 h. The solution was concentrated to
ca. 4 mL, Et2O (10 mL) was added, the suspension was filtered, and
1
3314 w, 3248 w. H NMR (400.91 MHz, DMSO-d6): 3a, δ 1.81 (s, 3
H, Me), 2.59−2.75 (m, 2 H, CH2Ar), 2.83 (m, 1 H, CH2N), 2.94 (m,
1 H, NH2), 3.16 (br s, 1 H, CH2N), 3.74 (s, 3 H, MeO), 3.77 (s, 3 H,
MeO), 4.13 (br d, 1 H, NH2, 2JHH = 10.4 Hz), 6.76 (s, 1 H, H6), 6.94
(s, 1 H, H3), 7.22 (m, 1 H, p-H, Ph), 7.30 (t, 2 H, m-H, Ph, 3JHH = 7.3
Hz), 7.42 (d, 2 H, o-H, Ph, 3JHH = 7.6 Hz); 3′a (selected data), δ 2.01
(s, 3 H, Me), 3.60 (s, 3 H, MeO), 3.75 (s, 3 H, MeO), 6.48 (s, 1 H,
C6H2), 6.93 (s, 1 H, C6H2). 13C{1H} NMR (100.81 MHz, DMSO-d6):
3a, δ 21.4 (s, Me), 33.0 (s, CH2Ar), 47.8 (s, CH2N), 55.4 (s, MeO),
55.8 (s, MeO), 111.0 (s, CH, C6), 113.8 (s, CH, C3), 125.5 (s, p-CH,
Ph), 127.8 (s, m-CH, Ph), 128.3 (s, o-CH, Ph), 130.9 (s, C7), 131.5 (s,
C2), 138.7 (s, C1), 143.8 (s, i-C, Ph), 146.7 (s, C5), 147.4 (s, C4); 3′a
(selected data), 24.0 (s, Me), 55.6 (s, MeO), 112.0 (s, CH, C6H2),
113.3 (s, CH, C6H2).
1
the solvent was removed from the filtrate. The H NMR spectrum of
the residue corresponded to a mixture of the two regioisomers 3b +
3′b (ratio ca. 8/1). The residue was dissolved in CH2Cl2 (2 mL), and
Et2O (15 mL) was added. The suspension was filtered, and the solid
was washed with Et2O (2 × 5 mL) and air-dried to afford a first crop
of the complex 3b as a yellow solid (268 mg). The filtrate was
concentrated to ca. 5 mL, and n-pentane (20 mL) was added. The
suspension was filtered, and the solid was washed with n-pentane (2 ×
5 mL) and air-dried to afford a second crop of the complex 3b as a
yellow solid (48 mg). Yield: 316 mg, 0.389 mmol, 75%. Dec pt: 185
°C. Anal. Calcd for C38H44Cl2N2Pd2 (812.526): C, 56.17; H, 5.46; N,
3.45. Found: C, 56.16; H, 5.57; N, 3.34. IR (cm−1): ν(NH) 3192 w,
Synthesis of 1b. A solution of diphenylacetylene (185 mg, 1.034
mmol) in CH2Cl2 (10 mL) was added dropwise to a solution of
palladacycle B (300 mg, 0.517 mmol) in CH2Cl2 (10 mL), and the
mixture was strirred for 3.5 h. The yellow solution was concentrated to
ca. 1 mL, and n-pentane (20 mL) was added. The resulting suspension
1
3300 w. H NMR (400.91 MHz, DMSO-d6): δ 1.23 (s, 3 H, Me,
CMe2), 1.42 (s, 3 H, Me, CMe2), 1.81 (s, 3 H, MeC), 2.35 (br d, 1
H, NH2, 2JHH = 11.7 Hz), 2.59 (d, 1 H, CH2Ar, 2JHH = 13.5 Hz), 2.87
2
2
(d, 1 H, CH2Ar, JHH = 13.5 Hz), 4.18 (br d, 1 H, NH2, JHH = 10.8
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Hz), 7.23 (m partially obscured, 1 H, H6), 7.24−7.36 (m, 6 H, Ar +
Ph), 7.40 (m, 2 H, o-H, Ph). 13C{1H} NMR (75.45 MHz, DMSO-d6):
δ 21.6 (s, MeC), 27.6 (s, Me, CMe2), 33.8 (s, Me, CMe2), 44.1 (s,
CH2Ar), 56.2 (s, CMe2), 125.5 (s, CH, Ar), 125.6 (s, p-CH, Ph), 126.0
(s, CH, Ar), 127.7 (s, o-CH, Ph), 127.8 (s, CH, Ar), 128.5 (s, m-CH,
Ph), 131.2 (s, C(Me)Ar), 132.3 (s, CH, C6), 135.9 (s, C1), 143.5 (s, i-
C, Ph), 145.9 (s, C−Pd), 147.1 (s, C2). Selected 1H NMR data of the
minor isomer 3′b from the mixture (400.91 MHz, DMSO-d6): δ 1.09
(s, 3 H, Me, CMe2), 1.15 (s, 3 H, Me, CMe2), 2.04 (s, 3 H, MeC),
2.56 (br d, partially obscured by the signals of the isomer 3b, 1 H,
mL) and air-dried to afford complex 6a as a yellow solid. Yield: 62 mg,
0.121 mmol, 58%. Mp: 138 °C. ESI-HRMS: calcd for C19H21NO2Pd
402.0631 [(M − CO − HBr)+], found 402.0685. IR (cm−1): ν(NH)
1
3310 w, 3253 w; ν(CO) 2097 s. H NMR (400.91 MHz, −60 °C): δ
1.91−2.06 (m, 1 H, NH2), 2.11 (s, 3 H, Me), 2.69 (m, 1 H, CH2Ar),
2.94−3.02 (m, 1 H, CH2Ar), 3.15−3.28 (m, 1 H, CH2N), 3.51−3.53
(m, 1 H, CH2N), 3.96 (s, 3 H, MeO), 3.98 (s, 3 H, MeO), 6.70 (s, 1
H, H3), 6.84 (s, 1 H, H6), 7.23−7.57 (m, 5 H, o-H + m-H + p-H, Ph).
13C{1H} NMR (100.81 MHz, −60 °C): δ 22.3 (s, Me), 32.6 (s,
CH2Ar), 47.8 (s, CH2N), 55.7 (s, MeO), 55.9 (s, MeO), 55.8 (s,
MeO), 107.3 (s, CH, C6), 111.0 (s, CH, C3), 126.6 (s, p-CH, Ph),
128.8 (s, m-CH + o-CH, Ph), 129.9 (s, C2), 137.1 (s, C1), 137.6 (s, i-
C, Ph), 140.6 (s, C7), 147.8 (s, C4 + C5), 174.1 (s, CO). The 13C
NMR resonance corresponding to the C atom bonded to Pd(II) was
not observed.
2
2
CH2Ar, JHH = 13.8 Hz), 2.96 (d, 1 H, CH2Ar, JHH = 13.8 Hz), 7.06
3
(d, 2 H, o-H, Ph, JHH = 7.2 Hz).
Synthesis of 4a. CO was bubbled through a suspension of
complex 1a (120 mg, 0.110 mmol) in CH2Cl2 (20 mL) for 5 min, and
the resulting mixture was stirred for 30 min under a CO atmosphere.
Formation of a small amount of palladium(0) was observed. The
resulting mixture was filtered through a plug of Celite, the filtrate was
concentrated to ca. 1 mL, and n-pentane (30 mL) was added. The
suspension was filtered, and the solid was washed with n-pentane (2 ×
5 mL) and air-dried to afford complex 4a as a yellow solid. Yield: 82
mg, 0.143 mmol, 65%. Mp: 120 °C. ESI-HRMS: calcd for
C24H23NO2Pd 464.0788 [(M − CO − HBr)+], found 464.0841. IR
Synthesis of 4b. CO was bubbled through a solution of
palladacycle 1b (150 mg, 0.160 mmol) in CHCl3 (15 mL) for 5
min, and the mixture was strirred for 1 h under a CO atmosphere.
Formation of a small amount of palladium(0) was observed. The
suspension was filtered through a plug of Celite, the pale yellow filtrate
was concentrated to ca. 1 mL, Et2O (20 mL) was added, and the
mixture was cooled to 0 °C. The resulting suspension was filtered, and
the solid was washed with Et2O (2 × 5 mL) and air-dried to give 4b as
a colorless solid. Yield: 73 mg, 0.147 mmol, 46%. Dec pt: 180 °C. Anal.
Calcd for C25H24ClNOPd (496.344): C, 60.49; H, 4.87; N, 2.82.
Found: C, 60.35; H, 5.07; N, 2.86. IR (cm−1): ν(NH) 3277 m, 3229
1
(cm−1): ν(NH) 3305 w, 3253 w; ν(CO) 2100 s. H NMR (400.91
MHz): δ 1.78 (m, 1 H, NH2), 2.82 (m, 1 H, CH2Ar), 3.02 (dd, 1 H,
2
3
CH2Ar, JHH = 14.8 Hz, JHH = 4.4 Hz), 3.24−3.31 (m, 2 H, 1 H of
NH2 + 1 H of CH2N), 3.43−3.47 (m, 1 H, CH2N), 3.77 (s, 3 H,
MeO), 3.96 (s, 3 H, MeO), 6.46 (s, 1 H, H3), 6.87 (s, 1 H, H6), 6.90−
6.92 (m, 2 H, o-H, Ph), 7.09−7.27 (m, 8 H, 2 H of p-H + 4 H of m-H
+ 2 H of o-H, Ph). 13C{1H} NMR (100.81 MHz, −60 °C): δ 32.7 (s,
CH2Ar), 47.9 (s, CH2N), 55.8 (s, MeO), 55.9 (s, MeO), 108.5 (s, CH,
C6), 110.7 (s, CH, C3), 126.6 (s, p-CH, Ph), 126.7 (s, p-CH, Ph),
127.7 (s, m-CH, Ph), 128.6 (s, m-CH, Ph), 129.1 (s, o-CH, Ph), 129.3
(s, o-CH, Ph), 131.7 (s, C2), 136.8 (s, C1), 137.8 (s, i-C, Ph), 140.4
(s, C7), 141.6 (s, C−Pd), 144.5 (s, i-C, Ph), 147.8 (s, C5), 148.0 (s,
C4), 173.8 (s, CO).
1
m; ν(CO) 2109 s. H NMR (400.91 MHz): δ 1.46 (s, 3 H, Me,
2
CMe2), 1.49 (s, 3 H, Me, CMe2), 1.87 (br d, 1 H, NH2, JHH = 10.4
2
Hz), 2.83 (d, 1 H, CH2Ar, JHH = 14.0 Hz), 3.13 (“d”, 2 H, 1 H of
2
NH2 + 1 H of CH2Ar, JHH = 14.0 Hz), 6.81 (m, 2 H, o-H, Ph), 7.05
(m, 4 H, 2 m-H and p-H of Ph + H6), 7.19 (m, 2 H, o-H, Ph), 7.23
(m, 1 H, p-H, Ph), 7.28 (m, 2 H, m-H, Ph), 7.30−7.33 (m, 1 H, H5),
7.34−7.36 (m, 2 H, H4 + H3). 13C{1H} NMR (100.81 MHz): δ 27.5
(s, Me, CMe2), 35.7 (s, Me, CMe2), 44.4 (s, CH2Ar), 58.1 (s, CMe2),
126.7 (s, p-CH, Ph), 127.0 (s, p-CH, Ph), 127.2 (s, CH, C4), 127.8 (s,
m-CH, Ph), 128.2 (s, CH, C6), 128.4 (s, CH, C5), 129.0 (s, o-CH,
Ph), 129.2 (s, o-CH, Ph), 129.5 (s, m-CH, Ph), 132.3 (s, CH, C3),
136.3 (s, C2), 139.2 (s, i-C, Ph), 142.2 (s, C7), 142.3 (s, i-C, Ph),
143.0 (s, C-Pd), 146.2 (s, C1), 173.5 (s, CO).
Synthesis of 5b. CO was bubbled through a solution of
palladacycle 2b (100 mg, 0.111 mmol) in CH2Cl2 (10 mL) for 5
min, and the yellow solution was strirred for 30 min. The mixture was
filtered through a plug of Celite, the filtrate was concentrated to ca. 2
mL, and Et2O (20 mL) was added. The suspension was filtered, and
the solid was washed with Et2O (2 × 5 mL) and air-dried to afford 5b
as a bright yellow solid. Yield: 60 mg, 0.125 mmol, 56%. Mp: 195 °C.
Anal. Calcd for C21H22ClNO3Pd (478.283): C, 52.74; H, 4.64; N,
2.93. Found: C, 52.77; H, 4.84; N, 3.05. IR (cm−1): ν(NH) 3292 m,
3214 m; ν(CO) 2111 vs; ν(CO2R) 1696 vs 1H NMR (300.1 MHz): δ
1.42 (s, 3 H, Me, CMe2), 1.49 (s, 3 H, Me, CMe2), 1.94 (br d, 1 H,
NH2, 2JHH = 9.6 Hz), 2.75 (d, 1 H, CH2Ar, 2JHH = 14.4 Hz), 3.05 (d, 1
H, CH2Ar, 2JHH = 14.4 Hz), 3.20 (br d, 1 H, NH2, 2JHH = 8.6 Hz), 3.48
(s, 3 H, MeO), 7.18−7.21 (m, 2 H, o-H, Ph), 7.24−7.43 (m, 7 H,
C6H4). 13C{1H} NMR (75.45 MHz): δ 27.5 (s, Me, CMe2), 35.6 (s,
Me, CMe2), 44.2 (s, CH2Ar), 51.7 (s, MeO), 58.3 (s, CMe2), 126.7 (p-
H and m-H of Ph s, o-CH, Ph), 127.85 (s, partially obscured, CH),
127.88 (br s, CH), 128.0 (s, CH), 129.2 (s, m-CH, Ph), 132.6 (s, CH,
C3), 134.8 (s, C7), 136.3 (s, C2), 141.1 (s, C1), 142.2 (s, i-C, Ph),
162.5 (s, C−Pd), 164.0 (s, CO2Me), 172.4 (s, CO). The 13C signal
corresponding to one aromatic CH was not observed.
Synthesis of 5a·1/4CH2Cl2 + 5′a·1/4CH2Cl2. CO was bubbled
through a suspension of palladacycles 2a + 2′a (100 mg, 0.095 mmol)
in CH2Cl2 (20 mL) for 5 min, and the resulting mixture was stirred for
10 min under a CO atmosphere. Formation of a small amount of
palladium(0) was observed. The resulting suspension was filtered
through a plug of Celite, the filtrate was concentrated to ca. 1 mL, and
Et2O (30 mL) was added. The suspension was filtered, and the solid
was washed with Et2O (2 × 5 mL) and air-dried to afford a mixture of
regioisomers 5a·1/4CH2Cl2 + 5′a·1/4CH2Cl2 (ratio ca. 3/1) as a yellow
solid. Yield: 55 mg, 0.096 mmol, 50%. Anal. Calcd for
C21H22BrNO5Pd·1/4CH2Cl2 (575.183): C, 44.31; H, 3.94; N, 2.43.
Found: C, 44.55; H, 4.14; N, 2.60. ESI-HRMS: calcd for
C20H21NO4Pd 446.0530 [(M − CO − HBr)+], found 446.0586. IR
(cm−1): ν(NH) 3291 w, 3234 w; ν(CO) 2095 s; ν(CO2R) 1601 s. 1H
NMR (400.91 MHz): 5a, δ 1.89 (m, 1 H, NH2), 2.76 (m, 1 H,
CH2Ar), 2.92 (m, 1 H, CH2Ar), 3.19−3.25 (m, 1 H, CH2N), 3.35−
3.48 (m, 2 H, 1 H of CH2N + 1 H of NH2), 3.53 (s, 3 H, MeO), 3.89
(s, 3 H, MeO), 3.94 (s, 3 H, MeO), 6.71 (s, 1 H, H6), 6.82 (s, 1 H,
H3), 7.16−7.45 (m, 5 H, o-H + m-H + p-H, Ph); 5′a (selected data), δ
3.79 (s, 3 H, MeO), 3.81 (s, 3 H, MeO), 3.95 (s, 3 H, MeO), 6.52 (s, 1
H, H6), 6.83 (s, 1 H, H3). 13C{1H} NMR (100.81 MHz, −60 °C): 5a,
δ 32.2 (s, CH2Ar), 40.0 (s, CH2N), 52.3 (s, MeO), 55.7 (s, MeO),
56.0 (s, MeO), 108.4 (s, CH, C6), 111.3 (s, CH, C3), 126.2 (s, o-CH,
Ph), 128.0 (s, m-CH, Ph), 129.1 (s, p-CH, Ph), 131.7 (s, C2), 132.2 (s,
i-C, Ph), 132.4 (s, C1), 141.8 (s, C7), 147.6 (s, C5), 148.5 (s, C4),
163.1 (s, C-CO), 167.1 (s, CO2Et), 172.8 (s, CO); 5′a (selected data),
52.8 (s, MeO), 55.8 (s, MeO), 56.1 (s, MeO), 108.3 (s, CH, C6),
111.1 (s, CH, C3) ppm.
Synthesis of 6b. CO was bubbled through a solution of
palladacycle 3b (150 mg, 0.185 mmol) in CH2Cl2 (4 mL) for 1
min, and the resulting yellow solution was strirred for 1 min. n-
Pentane (25 mL) was added, the resulting suspension was filtered, and
the solid was washed with n-pentane (2 × 5 mL) and air-dried to
afford crude complex 6b as a yellow solid. Yield: 118 mg, 0.282 mmol,
76%. The instability of 6b in solution prevented us from recrystallizing
it to obtain an analytically pure sample. ESI-HRMS: calcd for
C19H21NPd 370.0733 [(M − CO − HCl)+], found 370.0829. IR
Synthesis of 6a. CO was bubbled through a solution of complexes
3a + 3′a (100 mg, 0.104 mmol) in CH2Cl2 (20 mL) for 5 min, and the
resulting mixture was stirred for 10 min under a CO atmosphere.
Formation of a small amount of palladium(0) was observed. The
resulting suspension was filtered through a plug of Celite, the filtrate
was concentrated to ca. 1 mL, and Et2O (30 mL) was added. The
suspension was filtered, and the solid was washed with Et2O (2 × 5
1
(cm−1): ν(NH) 3295 m, 3197 m, 3121 m; ν(CO) 2104 s. H NMR
1100
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(400.91 MHz, −60 °C): δ 1.32 (s, 3 H, Me, CMe2), 1.52 (s, 3 H, Me,
CMe2), 1.86 (br d, 1 H, NH2, 2JHH = 10.8 Hz), 2.04 (s, 3 H, Me), 2.72
suspension for 3 min, the mixture was filtered through a plug of Celite,
the filtrate was concentrated to ca. 5 mL, and Et2O (10 mL) was
added. The suspension was filtered, the filtrate was concentrated to ca.
5 mL, and n-pentane (20 mL) was added. The resulting suspension
was cooled in an ice bath and filtered. The solid was washed with n-
pentane (2 × 5 mL) and air-dried to afford crude 9b as a bright yellow
solid. Yield: 77 mg, 0.140 mmol, 38%. The instability of 9b in solution
prevented us from recrystallizing it to obtain an analytically pure
sample. ESI-HRMS: calcd for C19H21NPd 370.0733 [(M − CO −
HTfO)+], found 370.0808. ΛM (Ω−1 mol−1 cm2): 120 (6.75 × 10−4 M,
acetone); 3 (7.3 × 10−4 M, 1,2-dichloroethane). IR (cm−1): ν(NH)
3297 m, 3217 m; ν(CO) 2120 vs. 1H NMR (400.91 MHz, −5 °C): δ
1.32 (s, 3 H, Me, CMe2), 1.49 (s, 3 H, Me, CMe2), 1.92 (br d, 1 H,
2
2
(d, 1 H, CH2Ar, JHH = 14.4 Hz), 2.90 (d, 1 H, CH2Ar, JHH = 14.0
2
Hz), 3.50 (br d, 1 H, NH2, JHH = 7.6 Hz), 7.21 (m, 2 H, o-H, Ph),
7.24−7.45 (m, 7 H, C6H4 + p-H and m-H of Ph). 13C{1H} NMR
(100.81 MHz, −60 °C): δ 22.9 (s, Me), 27.0 (s, Me, CMe2), 35.2 (s,
Me, CMe2), 43.7 (s, CH2Ar), 57.6 (s, CMe2), 126.5 (s, CH), 126.68
(s, partially obscured, CH), 126.74 (s, partially obscured, CH), 127.6
(s, CH), 128.7 (s, o-CH, Ph), 129.0 (s, m-CH, Ph), 132.1 (s, CH, C3),
134.8 (s, C), 135.5 (s, C), 137.8 (s, C), 140.7 (s, i-C, Ph), 146.4 (s,
C1), 173.1 (s, CO).
Synthesis of 7b·1/4C5H12. TlOTf (113 mg, 0.325 mmol) was
added to a solution of complex 1b (150 mg, 0.160 mmol) in acetone
(5 mL), and the mixture was stirred for 15 min. CO was bubbled
through the suspension for 2 min, the mixture was filtered through a
plug of Celite, the solvent was removed from the filtrate, and CH2Cl2
(2 mL) and n-pentane (25 mL) were added. The suspension was
filtered, and the solid was washed with n-pentane (2 × 5 mL) and air-
dried to afford 7b·1/4C5H12 as a yellow solid. Yield: 153 mg, 0.243
m m o l , 7 6 % . D e c p t : 1 4 0 ° C . A n a l . C a l c d f o r
C26H24F3NO4PdS·1/4C5H12 (627.977): C, 52.12; H, 4.33; N, 2.23;
S, 5.11. Found: C, 52.11; H, 4.29; N, 2.37; S, 5.14. ΛM (Ω−1 mol−1
cm2): 119 (6.56 × 10−4 M, acetone); 1 (6.3 × 10−4 M, 1,2-
dichloroethane). IR (cm−1): ν(NH) 3295 m, 3219 m; ν(CO) 2124 vs
1H NMR (400.91 MHz): δ 0.88 (t, 1.5 H, CH3, n-pentane), 1.25 (m,
1.5 H, CH2, n-pentane), 1.41 (s, 3 H, Me, CMe2), 1.47 (s, 3 H, Me,
CMe2), 1.70 (br d, partially obscured by the resonance of H2O from
2
NH2, JHH = 9.6 Hz), 2.08 (s, 3 H, Me), 2.71 and 2.81 (AB system, 2
H, CH2Ar, 2JAB = 14.4 Hz), 3.82 (br d, 1 H, NH2, 2JHH = 8.0 Hz), 7.17
(d, 1 H, C6H4, 3JHH = 7.6 Hz), 7.27 (m, 2 H, o-H, Ph), 7.32−7.44 (m,
6 H, 3 H of C6H4 + p-CH and m-CH of Ph). 13C{1H} NMR (100.81
MHz, −5 °C): δ 22.5 (s, Me), 26.5 (s, Me, CMe2), 35.1 (s, Me,
1
CMe2), 44.4 (s, CH2Ar), 58.0 (s, CMe2), 119.5 (q, CF3, JCF = 318.8
Hz), 122.9 (s, C), 126.7 (s, CH), 127.2 (s, CH), 127.9 (s, CH), 128.2
(s, CH), 128.8 (s, o-CH, Ph), 129.5 (s, m-CH, Ph), 132.6 (s, CH, C3),
134.8 (s, C), 138.8 (s, C), 139.8 (s, C), 145.9 (s, C), 171.8 (s, CO).
Synthesis of 5,6-Diphenyl-8,9-dimethoxy-2,3-
dihydrobenzo[d]azocin-4(1H)-one (10a). CO was bubbled
through a suspension of complex 1a (100 mg, 0.092 mmol) in
CHCl3 (20 mL), and the resulting mixture was heated at 65 °C for 16
h under a CO atmosphere (1 atm). Decomposition to metallic
palladium was observed. The resulting suspension was filtered through
a plug of Celite, the filtrate was concentrated to ca. 2 mL, and Et2O
(30 mL) was added. The suspension was filtered, and the solid was
washed with Et2O (2 × 5 mL) and air-dried to afford a first crop of
compound 10a as an orange solid (45.5 mg). The filtrate was
concentrated to ca. 2 mL, and n-pentane (20 mL) was added. The
suspension was filtered, and the solid was washed with n-pentane (2 ×
5 mL) and air-dried to afford a second crop of compound 10a as a
yellow solid (10 mg). Yield: 55.5 mg, 0.144 mmol, 78%. Mp: 123 °C.
ESI-HRMS: calcd for C25H24NO3 386.1756 [(M + H)+]; found
386.1756. IR (cm−1): ν(NH) 3499 br w, 3366 w, 3300 w; ν(CO) 1632
m. 1H NMR (300.1 MHz): δ 2.96 (m, 1 H, CH2Ar), 3.26−3.36 (m, 1
H, CH2N), 3.52 (m, 1 H, CH2Ar), 3.61−3.72 (m, partially obscured
by the MeO signal, 1 H, CH2N), 3.68 (s, 3 H, MeO), 3.88 (s, 3 H,
MeO), 5.76 (m, 1 H, NH), 6.51 (s, 1 H, H7), 6.65 (s, 1 H, H10),
6.98−7.02 (m, 2 H, o-H Ph), 7.09−7.14 (m, 3 H, 2 H of m-H + 1 H of
p-H, Ph), 7.19−7.24 (m, 3 H, 2 H of m-H + 1 H of p-H, Ph). 13C{1H}
NMR (75.45 MHz): δ 33.5 (s, CH2Ar), 40.4 (s, CH2N), 55.8 (s,
MeO), 56.0 (s, MeO), 112.8 (s, CH, C7), 113.0 (s, CH, C10), 127.5
(s, p-CH, Ph), 127.7 (s, p-CH, Ph), 128.0 (s, m-CH, Ph), 128.3 (s,
C10a), 128.3 (s, m-CH, Ph), 129.2 (s, o-CH, Ph), 130.4 (s, o-CH, Ph),
134.1 (s, C6a), 135.2 (s, C5), 135.6 (s, i-C, Ph), 139.3 (s, i-C, Ph),
139.4 (s, C6), 147.9 (s, C8), 148.8 (s, C9), 173.6 (s, CO).
2
the deuterated solvent, 1 H, NH2, JHH = 10.0 Hz), 2.88 (d, 1 H,
2
2
CH2Ar, JHH = 14.4 Hz), 3.05 (d, 1 H, CH2Ar, JHH = 14.4 Hz), 3.75
2
(br d, 1 H, NH2, JHH = 10.0 Hz), 6.81(m, 2 H, o-H, Ph), 7.03−7.10
(m, 4 H, Ph + C6H4), 7.24 (m, 2 H, Ph + C6H4), 7.30−7.33 (m, 3 H,
Ph + C6H4), 7.38−7.42 (m, 3 H, Ph + C6H4). 13C{1H} NMR (75.45
MHz): δ 26.5 (s, Me, CMe2), 35.0 (s, Me, CMe2), 44.7 (s, CH2Ar),
58.4 (s, CMe2), 119.6 (q, CF3, 1JCF = 318.8 Hz), 127.2 (s, p-CH, Ph),
127.6 (s, CH), 128.0 (s, m-CH, Ph), 128.4 (s, CH), 129.1 (s, o-CH,
Ph), 129.2 (s, o-CH, Ph), 129.7 (s, CH, C6H4), 132.5 (s, CH, C3),
136.4 (s, C2), 138.3 (s, C), 140.6 (s, C), 142.5 (s, C), 145.5 (s, C1),
171.8 (s, CO). The 31C signals corresponding to one aromatic CH and
one quaternary carbon were not observed.
Synthesis of 8b. TlOTf (96 mg, 0.272 mmol) was added to a
suspension of complex 2b (120 mg, 0.134 mmol) in an acetone/
CH2Cl2 mixture (3/1, 20 mL), and the resulting suspension was
stirred for 15 min. CO was bubbled through the suspension for 3 min.
The mixture was filtered through a plug of Celite, the solvent was
removed from the filtrate, and CHCl3 (5 mL) and Et2O (10 mL) were
added. CO was bubbled again through the solution for 1 min, the
mixture was filtered through a plug of Celite, and n-pentane (30 mL)
was added. The suspension was filtered, and the solid was washed with
n-pentane (2 × 5 mL) and air-dried to afford 8b as an off-white solid.
Yield: 103 mg, 0.174 mmol, 65%. Dec pt: 150 °C. Anal. Calcd for
C22H22F3NO6PdS (591.893): C, 44.64; H, 3.75; N, 2.37; S, 5.42.
Found: C, 44.67; H, 3.91; N, 2.68; S, 4.95. ΛM (Ω−1 mol−1 cm2): 104
(4.79 × 10−4 M, acetone); 1 (6.0 × 10−4 M, 1,2-dichloroethane). IR
(cm−1): ν(NH) 3293 w, 3207 m; ν(CO) 2139 vs; ν(CO2R) 1691 vs.
1H NMR (300.1 MHz): δ 1.34 (s, 3 H, Me, CMe2), 1.50 (s, 3 H, Me,
Synthesis of 2,2-Dimethyl-5,6-diphenyl-2,3-dihydrobenzo-
[d]azocin-4(1H)-one (10b). Et3N (45 μL, 0.322 mmol) was added to
a solution of palladacycle 1b (150 mg, 0.160 mmol) in CHCl3 (10
mL) in a Carius tube, and CO was bubbled through the solution for 5
min. The pressure of CO was increased to 1 atm, the tube was sealed,
and the mixture was strirred at 60 °C for 12 h. Decomposition to
metallic palladium was observed. The resulting black suspension was
filtered through a plug of Celite, and the solvent from the pale yellow
filtrate was removed. Et2O (10 mL) was added, and the suspension
was filtered to separate the Et3NHCl. The filtrate was concentrated to
ca. 1 mL, and n-pentane (30 mL) was added. The suspension was
filtered, and the solid was washed with n-pentane (2 × 5 mL) and air-
dried to afford 10b as a colorless solid. Yield: 89 mg, 0.252 mmol, 77%.
Mp: 216 °C. ESI-HRMS: calcd for C25H24NO 354.1852 [(M + H)+],
found 354.1857. IR (cm−1): ν(NH) 3165 w; ν(CO) 1635 s. 1H NMR
(400.91 MHz): δ 1.21 (s, 3 H, Me, CMe2), 1.33 (s, 3 H, Me, CMe2),
2
CMe2), 1.86 (br d, 1 H, NH2, JHH = 10.5 Hz), 2.78 (d, 1 H, CH2Ar,
2
2JHH = 14.4 Hz), 2.98 (d, 1 H, CH2Ar, JHH = 14.7 Hz), 3.51 (s, 3 H,
2
MeO), 3.86 (br d, 1 H, NH2, JHH = 10.8 Hz), 7.26−7.29 (m, 3 H,
C6H4 or Ph), 7.34 (m, 1 H, C6H4 or Ph), 7.41−7.46 (m, 5 H, C6H4 or
Ph). 13C{1H} NMR (75.45 MHz): δ 26.5 (s, Me, CMe2), 35.0 (s, Me,
CMe2), 44.4 (s, CH2Ar), 52.1 (s, MeO), 58.6 (s, CMe2), 119.5 (q,
1
CF3, JCF = 318.4 Hz), 127.1 (s, o-CH, Ph), 128.0 (s, CH), 128.2 (s,
CH), 128.4 (s, CH), 129.1 (s, CH), 129.6 (s, m-CH, Ph), 132.9 (s,
CH, C3), 135.0 (s, C), 136.3 (s, C2), 140.3 (s, C1), 140.7 (s, C),
157.0 (br s, C), 162.9 (s, CO2Me), 170.6 (s, CO). Single crystals
suitable for an X-ray diffraction study were obtained by slow diffusion
of n-pentane into a solution of 8b in CHCl3.
2
2
2.81 (d, 1 H, CH2Ar, JHH = 13.2 Hz), 3.73 (d, 1 H, CH2Ar, JHH
=
Synthesis of 9b. TlOTf (131 mg, 0.370 mmol) was added to a
solution of complex 3b (150 mg, 0.185 mmol) in acetone (10 mL),
and the mixture was stirred for 20 min. CO was bubbled through the
13.6 Hz), 5.46 (s, 1 H, NH), 6.94 (m, 2 H, o-H, Ph), 7.05 (br d, 1 H,
H7, 3JHH = 8.0 Hz), 7.07−7.13 (m, 3 H, Ph), 7.17−7.21 (m, 4 H, 3 H
of Ph and H8), 7.22−7.30 (m, 2 H, H9 + H10), 7.52 (m, 2 H, o-H,
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Ph). 13C{1H} NMR (100.81 MHz): δ 30.0 (s, Me, CMe2), 31.6 (s,
Me, CMe2), 44.9 (s, CH2Ar), 54.3 (s, CMe2), 127.2 (s, CH, C8), 127.4
(s, p-CH, Ph), 127.5 (s, p-CH, Ph), 127.8 (s, CH, C9 + m-CH, Ph),
128.1 (s, m-CH, Ph), 129.1 (s, CH, C10), 129.7 (s, o-CH, Ph), 130.1
(s, CH, C7), 130.6 (s, o-CH, Ph), 135.6 (s, i-C, Ph), 136.2 (s, C5),
136.8 (s, C10a), 138.7 (s, C6), 140.2 (s, i-C, Ph), 142.4 (s, C6a), 171.4
(s, CO). Single crystals suitable for an X-ray diffraction study were
obtained by slow diffusion of n-pentane into a solution of 10b in
CHCl3.
tube was sealed, and the mixture was strirred at room temperature for
16 h. Decomposition to metallic palladium was observed. The
resulting suspension was filtered through a plug of Celite, and the
solvent was removed from the filtrate. The residue was vigorously
stirred in Et2O (30 mL), the suspension was filtered, and the solid was
washed with Et2O (2 × 5 mL) and air-dried to afford a mixture of
compund 12a and NHEt3Br as a pale yellow solid (94 mg). The
1
solvent was removed from the filtrate. The H NMR spectrum of the
residue corresponded to a mixture of regioisomers 12a + 12′a (ratio
ca. 3.3/1). The mixture 12a + NHEt3 was dissolved in CH2Cl2 (20
Synthesis of 5-Phenyl-6-methoxycarbonyl-8,9-dimethoxy-
2,3-dihydrobenzo[d]azocin-4(1H)-one (11a). Et3N (21 μL,
0.152 mmol) was added to a solution of 2a + 2′a (80 mg, 0.076
mmol) in CHCl3 (20 mL) in a Carius tube, and CO was bubbled
through the solution for 5 min. The pressure of CO was increased to 1
atm, the tube was sealed, and the mixture was strirred at 65 °C for 16
h. Decomposition to metallic palladium was observed. The resulting
suspension was filtered through a plug of Celite, and the solvent was
removed from the filtrate. The residue was vigorously stirred in Et2O
(30 mL), the suspension was filtered, and the solid was washed with
Et2O (2 × 5 mL) and air-dried to afford a mixture of compound 11a
and NHEt3Br as a pale yellow solid (50 mg). The filtrate was
concentrated to ca. 2 mL, and n-pentane (30 mL) was added. The
suspension was filtered, and the solid was washed with n-pentane (2 ×
5 mL) and air-dried to afford the compound 11a as a yellow solid (10
mg). The solvent was removed from the filtrate. The 1H NMR spectra
of the residue corresponded to a mixture of 11a + 11′a (ratio ca. 1/1).
The mixture 11a + NHEt3 was dissolved in CH2Cl2 (20 mL), and
Na2CO3 was added (100 mg, 0.943 mmol). The suspension was
stirred for 6 h and filtered through a plug of Celite. The filtrate was
concentrated to ca. 2 mL, and Et2O (30 mL) was added. The
suspension was filtered, and the solid was washed with Et2O (2 × 5
mL) and air-dried to afford the compound 11a as a yellow solid (25
mg). Yield: 35 mg, 0.095 mmol, 62%. Mp: 125 °C. EI-HRMS: calcd
for C21H21NO5 368.1420 [(M + H)+]; found 368.1428. IR (cm−1):
mL), and Na2CO3 was added (100 mg, 0.943 mmol). The suspension
́
was stirred for 6 h and filtered through a plug of Celite. The filtrate
was concentrated to ca. 2 mL, and Et2O (30 mL) was added. The
suspension was filtered, and the solid was washed with Et2O (2 × 5
mL) and air-dried to afford compound 12a as a yellow solid. Yield: 65
mg, 0.200 mmol, 81%. Mp: 115 °C. ESI-HRMS: calcd for C20H22NO3
324.1600 [(M + H)+], found 324.1605. IR (cm−1): ν(NH) 3361 w,
3191 m; ν(CO) 1646 s. 1H NMR (300.1 MHz): δ 2.09 (s, 3 H, Me),
2.84 (m, 1 H, CH2Ar), 3.20−3.37 (m, 2 H, 2 H 1 H of CH2Ar + 1 H
of CH2N), 3.76−3.82 (m, 1 H, CH2N), 3.87 (s, 3 H, MeO), 3.87 (s, 3
H, MeO), 5.58 (m, 1 H, NH), 6.60 (s, 1 H, H10), 6.80 (s, 1 H, H7),
7.32−7.43 (m, 3 H, 2 H of m-H + 1 H of p-H, Ph), 7.52−7.56 (m, 2
H, o-H, Ph). 13C{1H} NMR (75.45 MHz): δ 21.3 (s, Me), 33.3 (s,
CH2Ar), 40.5 (s, CH2N), 55.9 (s, MeO), 55.9 (s, MeO), 110.9 (s, CH,
C7), 113.2 (s, CH, C10), 126.6 (s, C10a), 127.7 (s, p-CH, Ph), 128.4
(s, m-CH, Ph), 128.9 (s, o-CH, Ph), 134.6 (s, C6a), 135.0 (s, C5),
135.8 (s, i-C, Ph), 136.7 (s, C6), 147.8 (s, C8), 148.3 (s, C9), 173.9 (s,
CO).
Synthesis of 2,2,6-Trimethyl-5-phenyl-2,3-dihydrobenzo[d]-
azocin-4(1H)-one (12b). Et3N (45 μL, 0.322 mmol) was added to a
solution of palladacycle 3b (130 mg, 0.160 mmol) in CHCl3 (15 mL)
in a Carius tube, and CO was bubbled through the solution for 5 min.
The pressure of CO was increased to 1 atm, the tube was sealed, and
the mixture was stirred at room temperature for 12 h. Decomposition
to metallic palladium was observed. The resulting suspension was
filtered through a plug of Celite, the filtrate was concentrated to ca. 1
mL, Et2O (20 mL) was added, and the suspension was filtered to
separate the Et3NHCl. The filtrate was concentrated to ca. 1 mL, and
n-pentane (30 mL) was added. The resulting suspension was filtered,
and the solid was washed with n-pentane (2 × 5 mL) and air-dried to
afford 12b as a colorless solid. Yield: 61 mg, 0.209 mmol, 65%. Mp:
230 °C. ESI-HRMS: calcd for C20H22NO 292.1701 [(M + H)+], found
1
ν(NH) 3310 w, 3244 w; ν(CO) 1721 s. H NMR (400.91 MHz): δ
2.88−2.92 (m, 1 H, CH2Ar), 3.34−3.50 (m, 3 H, 1 H of CH2Ar + 2 H
of CH2N), 3.59 (s, 3 H, MeO), 3.86 (s, 3 H, MeO), 3.88 (s, 3 H,
MeO), 5.71 (m, 1 H, NH), 6.63 (s, 1 H, H10), 6.88 (s, 1 H, H7),
7.37−7.41 (m, 3 H, 2 H of m-H + 1 H of p-H, Ph), 7.54−7.57 (m, 2
H, o-H, Ph). 13C{1H} NMR (100.81 MHz): δ 33.6 (s, CH2Ar), 40.5
(s, CH2N), 52.2 (s, MeO), 55.9 (s, MeO), 56.0 (s, MeO), 111.7 (s,
CH, C7), 113.7 (s, CH, C10), 127.7 (s, C6a), 128.0 (s, o-CH, Ph),
128.2 (s, C10a), 128.6 (s, m-CH, Ph), 129.0 (s, p-CH, Ph), 132.2 (s,
C6), 134.4 (s, i-C, Ph), 140.8 (s, C6), 147.7 (s, C8), 149.3 (s, C9),
168.6 (s, CO2Me), 171.3 (s, CO).
1
292.1696. IR (cm−1): ν(NH) 3389 w, 3169 w; ν(CO) 1645 s. H
NMR (400.91 MHz): δ 1.27 (s, 3 H, Me, CMe2), 1.32 (s, 3 H, Me,
CMe2), 2.04 (s, 3 H, MeC), 2.66 (d, 1 H, CH2Ar, 2JHH = 13.2 Hz),
3.45 (d, 1 H, CH2Ar, 2JHH = 12.8 Hz), 5.39 (s, 1 H, NH), 7.18 (dd, 1
H, H10, 3JHH = 7.2, 4JHH = 1.6 Hz), 7.22−7.40 (m, 6 H, CH, Ar + Ph),
7.65 (m, 2 H, o-H, Ph). 13C{1H} NMR (75.45 MHz): δ 22.2 (s,
MeC), 30.0 (s, Me, CMe2), 32.0 (s, Me, CMe2), 44.8 (s, CH2Ar),
54.3 (s, CMe2), 127.0 (s, CH, C8), 127.4 (s, CH, Ar), 127.5 (br s, p-
CH from Ph + CH from Ar), 128.2 (s, CH, m-CH, Ph), 129.2 (s, CH,
C10), 129.4 (s, o-CH, Ph), 135.4 (s, C10a), 135.7 (s, C5), 136.3 (s, i-
C, Ph), 136.6 (s, C6), 142.7 (s, C6a), 171.6 (s, CO). Single crystals
suitable for an X-ray diffraction study were obtained by slow diffusion
of n-pentane into a solution of 12b in CHCl3.
2,2-Dimethyl-5-methoxycarbonyl-6-phenyl-2,3-
dihydrobenzo[d]azocin-4(1H)-one (11b). CO was bubbled for 3
min through a solution of palladacycle 2b (75 mg, 0.083 mmol) in
CHCl3 (10 mL) in a Carius tube. The pressure of CO was increased to
1 atm, the tube was sealed, and the mixture was stirred for 12 h. A
slight decomposition to palladium black was observed. The mixture
was filtered through a plug of Celite, the filtrate was concentrated to
ca. 2 mL, and n-pentane (20 mL) was added. The suspension was
filtered, and the solid was air-dried to give a mixture of the starting
1
material 2b and the carbonyl complex 5b (45 mg; by H NMR). The
Single-Crystal X-ray Structure Determinations. Relevant
crystallographic data and details of the refinements for the structures
of compounds 1b·1/2C6H14, 2b, 8b, 10b, and 12b are given in Table 1
(Supporting Information).
Data Collection. Crystals suitable for X-ray diffraction were
mounted in inert oil on a glass fiber and transferred to a Bruker
SMART diffractometer. Data were recorded at 100(2) K, using
graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) and ω-
scan mode. Multiscan absorption corrections were applied for all
complexes.
solvent was removed from the filtrate to afford a small amount of a
colorless solid (12 mg), which H NMR proved to be a mixture of
1
lactam 11b (major component) and some unidentified compounds. In
the ESI-HRMS of this mixture, the peak corresponding to [(11b +
H)+] was observed: calcd for C21H22NO3 336.1599 [(M + 1)+], found
336.1594. 1H NMR data from the mixture (200.13 MHz): δ 1.33 (s, 3
H, Me, CMe2), 1.62 (s, 3 H, Me, CMe2), 2.46 (br s, 2 H, CH2Ar), 3.31
3
(s, 3 H, MeO), 4.46 (s, 1 H, NH), 7.19 (d, 1 H, Ar or Ph, JHH = 7.2
Hz), 7.28−7.49 (m, 7 H, Ar + Ph), 7.65 (d, 1 H, Ar or Ph, 3JHH = 7.2
Hz).
Structure Solution and Refinement. Crystal structures were solved
by direct methods, and all non-hydrogen atoms were refined
anisotropically on F2 using the program SHELXL-97.50 Hydrogen
atoms were refined as follows. Complexes 1b·1/2C6H14 and 2b: NH2,
free with SADI; methyl, rigid group; all others, riding. Complex 8b:
Synthesis of 8,9-Dimethoxy-6-methyl-5-phenyl-2,3-
dihydrobenzo[d]azocin-4(1H)-one (12a). Et3N (35 μL, 0.248
mmol) was added to a solution of 3a + 3′a (120 mg, 0.124 mmol) in
CHCl3 (20 mL) in a Carius tube, and CO was bubbled through the
solution for 5 min. The pressure of CO was increased to 1 atm, the
1102
dx.doi.org/10.1021/om301241n | Organometallics 2013, 32, 1094−1105

Organometallics
Article
NH2, free with DFIX; methyl, rigid group; all others, riding.
Compounds 10b and 12b: NH, free; methyl, rigid group; all others,
riding. Special features: for complex 1b·1/2C6H14, the relatively high
electron density, 2.69 e Å3, at 0.92 Å of Pd(1) can be ascribed to an
absorption error; for complex 8b, absolute structure (Flack)
parameter51 −0.013(5).
Computational Details. Density funtional calculations were
carried out using the Gaussian 03 package.52 The hybrid density
functional BP8653 was applied, employing the SDD basis set54 to
describe the Cl and Pd atoms and 6-31G* for N, C, and H.55 After
geometry optimizations, analytical frequency calculations were carried
out to determine the nature of the stationary points found and confirm
they were minima.
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era, C.;
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Botella-Segura, L. Organometallics 2005, 24, 5044.
́
ez-Serrano, J.; Jones, P. G.; Naj
́
ASSOCIATED CONTENT
* Supporting Information
Figures, tables, and CIF files giving a complete set of Cartesian
́
́
(8) Vicente, J.; Saura-Llamas, I.; Turpın, J.; Bautista, D.; Ramırez de
Arellano, C.; Jones, P. G. Organometallics 2009, 28, 4175.
(9) Subramanium, S. S.; M. Slaughter, L. M. Dalton Trans. 2009,
6930.
■
S
coordinates for all computed structures, details (including
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1984, 1165. Ryabov, A. D. Synthesis 1985, 233. Tollari, S.; Demartin,
F.; Cenini, S.; Palmisano, G.; Raimondi, P. J. Organomet. Chem. 1997,
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Consorti, C. S.; Spencer, J. Chem. Rev. 2005, 105, 2527. Vicente, J.;
1
symmetry operators) of hydrogen bonds, H and 13C-APT
spectra of compounds 4a, 6a,b, 9b, 10a,b, 11a, and 12a,b, and
crystallographic data for 1b·1/2C6H14, 2b, 8b, 10b, and 12b.
This material is available free of charge via the Internet at
http://pubs.acs.org.
́
́
Saura-Llamas, I.; Garcıa-Lopez, J. A.; Calmuschi-Cula, B.; Bautista, D.
́
Organometallics 2007, 26, 2768. Vicente, J.; Saura-Llamas, I.; Garcıa-
AUTHOR INFORMATION
Corresponding Author
*E-mail: jvs1@um.es (J.V.); ims@um.es (I.S.-L.).
Lopez, J.-A.; Bautista, D. Organometallics 2009, 28, 448.
(11) Nieto, S.; Arnau, P.; Serrano, E.; Navarro, R.; Soler, T.;
́
■
Cativiela, C.; Urriolabeitia, E. P. Inorg. Chem. 2009, 48, 11963.
́
(12) Garcıa-Lop
́
ez, J.-A.; Oliva-Madrid, M.-J.; Saura-Llamas, I.;
Notes
Bautista, D.; Vicente, J. Organometallics 2012, 31, 6351.
The authors declare no competing financial interest.
(13) Frutos-Pedreno, R.; Gonzal
G. Organometallics 2012, 31, 3361.
́
ez-Herrero, P.; Vicente, J.; Jones, P.
̃
(14) Ozawa, F.; Kawasaki, N.; Okamoto, H.; Yamamoto, T.;
Yamamoto, A. Organometallics 1987, 6, 1640. Negishi, E.; Zhang, Y.;
Shimoyama, I.; Wu, G. J. Am. Chem. Soc. 1989, 111, 8018. Grushin, V.
V.; Alper, H. Organometallics 1993, 12, 1890. Monteil, F.; Kalck, P. J.
Organomet. Chem. 1994, 482, 45. Yamamoto, Y. Bull. Chem. Soc. Jpn.
1995, 68, 433. Negishi, E.; Coperet, C.; Ma, S.; Mita, T.; Sugihara, T.;
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Tour, J. M. J. Am. Chem. Soc. 1996, 118, 5904. Lin, Y.-S.; Yamamoto,
A. Organometallics 1998, 17, 3466. Kadnikov, D. V.; Larock, R. C. Org.
ACKNOWLEDGMENTS
We thank Ministerio de Educacion
(CTQ2007-60808/BQU and CTQ2011-24016), and Funda-
■
́
y Ciencia (Spain), FEDER
cion
L. and M.-J.O.-M. are grateful to the Fundacion
(CARM, Spain) and Ministerio de Educacion y Ciencia
́
Sen
́
eca (04539/GERM/06) for financial support. J.-A.G.-
́
́
Seneca
́
(Spain), respectively, for their research grants.
́
Lett. 2002, 2, 3643. Trzeciak, A. M.; Ziołkowski, J. J. Coord. Chem. Rev.
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