Coupling reactions of N -propargyl semi-salen compounds induced by ruthenium complex

Article abstract of DOI:10.1021/om500268x

The coupling reaction of N-propargyl semi-salen compound 1d on [Ru]-Cl ([Ru] = Cp(PPh₃)₂Ru) generates the carbene complex 3d containing a substituted 2H-chromene unit in 7 d. The precursor vinylidene complex 2d is isolated from the reaction of the propargyl group of 1d with [Ru]-Cl in 12 h. Addition of an o-cresol moiety to Cα and Cβ of the vinylidene ligand of 2d takes place in a longer reaction time to yield 3d. Reactions of [Ru]-Cl with other analogous compounds 1a, 1b, and 1c, in excess, also afford carbene complexes 3a, 3b, and 3c, respectively, in 48 h via a similar coupling process. Their precursor vinylidene complexes 2a, 2b, and 2c are also observed in 12 h. Structures of 2 and 3 are determined on the basis of spectroscopic data. The solid state structure of the dppe analogue 3a' is further confirmed by X-ray diffraction analysis. The added o-cresol part comes from compounds 1, instead of aldehyde which is confirmed by the cross-coupling reactions of 2 and 1 using mass spectrometry. For comparison, treatment of [Ru]Cl with the amine analogue 13b retaining the propargyl and phenol moieties yields no coupling product.

Full text of DOI:10.1021/om500268x

Article
pubs.acs.org/Organometallics
Coupling Reactions of N‑Propargyl Semi-Salen Compounds Induced
by Ruthenium Complex
Hsin-Tzu Hsu, Fu-Yuan Tsai, Ying-Chih Lin,* and Yi-Hong Liu
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
S
* Supporting Information
ABSTRACT: The coupling reaction of N-propargyl semi-salen compound 1d on [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) generates the
carbene complex 3d containing a substituted 2H-chromene unit in 7 d. The precursor vinylidene complex 2d is isolated from the
reaction of the propargyl group of 1d with [Ru]-Cl in 12 h. Addition of an o-cresol moiety to Cα and Cβ of the vinylidene ligand
of 2d takes place in a longer reaction time to yield 3d. Reactions of [Ru]-Cl with other analogous compounds 1a, 1b, and 1c, in
excess, also afford carbene complexes 3a, 3b, and 3c, respectively, in 48 h via a similar coupling process. Their precursor
vinylidene complexes 2a, 2b, and 2c are also observed in 12 h. Structures of 2 and 3 are determined on the basis of spectroscopic
data. The solid state structure of the dppe analogue 3a′ is further confirmed by X-ray diffraction analysis. The added o-cresol part
comes from compounds 1, instead of aldehyde which is confirmed by the cross-coupling reactions of 2 and 1 using mass
spectrometry. For comparison, treatment of [Ru]Cl with the amine analogue 13b retaining the propargyl and phenol moieties
yields no coupling product.
Schiff base, these N-propargyl semi-salen compounds display
distinctive reactivity. Intermolecular coupling of two molecules
via the triple bond and the semi-salen unit on the ruthenium
metal center affords the alkoxy carbene complexes with
polycyclic structure containing the related skeleton of coumarin
with the feature of one Schiff base retained (Scheme 1).
Coumarins, a class of fused ring heterocycles, occur widely in
nature and show interesting biological activity.14 In addition to
their biosynthesis in plants, coumarins could be prepared by
other approaches such as Pechmann condensation.15,16
Coumarin is also used as gain medium in dye lasers; it is well
documented that fluorescence of coumarin-type dyes displays
excellent quantum yield.17 In this paper, we report our
investigation on the ruthenium complex-mediated coupling of
these N-propargyl semi-salen compounds to yield carbene
complexes.
INTRODUCTION
■
During the past decade, chemistry of ruthenium vinylidene
complexes has experienced important developments due to
their involvement as key intermediates in the stoichiometric
reaction as well as catalytic transformation of terminal alkynes.1
These complexes generally play key roles in many carbon−
carbon and carbon−heteroatom coupling processes.2,3 Reac-
tions of MC bond of carbene complexes with organic
compounds with NC double bond were found to take place
in different ways.4 Hegedus reported that in the presence of
imines, β-lactams formed upon photolysis of (CO)5M[C-
(R)R′].5 Imines are normally prepared by a condensation
reaction of primary amine with aldehyde and, less commonly,
with ketone.6 Among extensively studied reactions of imine, the
aza-Baylis−Hilman reaction7 and the aza Diels−Alder reaction8
are well documented. Treatment of imine with mCPBA could
further give oxaziridine.9 Also, various imine compounds are
widely used in organic reactions.10−12 Aromatic Schiff-base,
containing an imine functionality and a hydroxyl group, is a
ligand commonly used in coordination chemistry.13 Much less
is known on the chemical property of molecules containing
both imine and alkynyl groups.
RESULTS AND DISCUSSION
■
N-Propargyl Semi-Salen. The N-propargyl semi-salen
compound 1a is prepared from the condensation reaction of
1
2-hydroxy benzaldehyde and propargyl amine. The H NMR
We prepare a series of Schiff base compounds, each tethering
a propargyl group on the imine nitrogen atom and explore their
reactions with Cp(PPh3)2RuCl. Unlike a simple nonsubstituted
Received: March 13, 2014
Published: June 26, 2014
© 2014 American Chemical Society
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[Ru′]-Cl ([Ru′] = Cp(dppe)Ru) with 1a and 1b at 45 °C in
MeOH result in formation of 3a′ and 3b′, respectively.
Single crystals of 3a′ are obtained from a bilayer solution of
ether/CH2Cl2, and the structure is confirmed by an X-ray
diffraction analysis. An ORTEP drawing of 3a′ is shown in
Figure 1. The bond length of Ru(1)−C(1) (1.986(2)Å) lies in
Scheme 1. Reactions of 1a−1d with [Ru]-Cl
Figure 1. ORTEP drawing of the cationic complex 3a′. For clarity,
−
hydrogens, PF6 , and aryl groups of dppe on Ru except the ipso
carbons are omitted. Thermal ellipsoid is set at the 50% probability
level. Selected distances (Å) and angles (deg): Ru(1)−C(1), 1.986(2);
C(1)−C(2), 1.462(3); C(2)−C(3), 1.358(3); O(1)−C(1), 1.374(3);
N(1)−C(11), 1.269(3). C(2)−C(1)−Ru(1), 132.01(17).
signal at δ 8.66 is assigned to the imine NCH proton of 1a.
Three analogous compounds 1b, 1c, and 1d are prepared
similarly, using different aldehydes. As shown in Scheme 1,
treatment of [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) with excess 1a
and NH4PF6 in CH2Cl2 for 2 d at room temperature affords the
carbene complex 3a in 83% yield. The same reaction in 12 h
gives 3a as the major product and the predecessor vinylidene
complex 2a and the acetylide complex 12 with a phosphonium
group as two minor products. Addition of an o-cresol moiety to
Cα and Cβ of the vinylidene ligand of 2a yields 3a containing a
substituted 2H-chromene unit. Interestingly, the reaction of 1a
in the presence of salicylaldehyde yields 2a as the major
product and a small amount of 3a, but attempts to purify 2a by
chromatography fail. Spectroscopic data of 2a are obtained
from the crude products. The two singlet 31P NMR signals at δ
42.97 and 49.00 are assigned to 2a and 3a, respectively.
Treatment of 1b and 1c with [Ru]-Cl for 2 days similarly yields
complexes 3b and 3c, respectively. Addition of salicylaldehyde
in the reaction mixture also hinders formation of 3.
the range of 1.82−1.99 Å found for many other ruthenium
carbene complexes.19 The bond lengths of the newly formed
C(2)−C(3) bond and O(1)−C(1) bond are 1.358(3) Å and
1.374(3) Å, respectively. In addition, the six-membered
heterocyclic ring is nearly a plane. The bond length of
N(1)−C(11) (1.269(3) Å) reveals the double bond of an imine
group.
In order to better understand the formation of 3 from 2,
attempts were thus made to prepare the acetylide complexes 4
from 2. As expected, the deprotonation at Cβ−H of a
vinylidene ligand can be easily achieved with base.20 When
NH4PF6 was first used as a salt in the presence of K2CO3 in the
+
reaction of 1, the cationic complex [Ru]-NH3 formed as the
major product from free NH3 released from deprotonation of
+
Slightly lower yield of 3c is possibly attributed to the
presence of the electron-withdrawing NO2 group that may
decrease the nucleophilicity of phenol. The electron-donating
OMe group in 1b, on the other hand, enhances the nucleophilic
addition of the O atom onto Cα of the vinylidene ligand of 2b,
giving higher yield of 3b. Moreover, the reaction of 1d with
[Ru]-Cl in 12 h affords only 2d. Further cycloaddition requires
7 d to afford 3d, most likely because of the steric effect of the
naphthalene moiety. Previously, the reaction of resorcinal with
metal alkenylcarbyne complex was reported to yield a cyclic
carbene complex.18
NH4 cation.21 Replacement of NH4PF6 by KPF6 in MeOH
resulted in formation of [Ru]-H. Probably O-coordination of
MeOH to the ruthenium center was followed by a β-hydrogen
elimination to give [Ru]-H and formaldehyde.22 Finally, in the
presence of K2CO3 and KPF6 in CH2Cl2, syntheses of two
stable acetylide complexes 4a and 4b were achieved from 1a
and 1b, respectively, as shown in Scheme 1. Complexes 4a and
4b are identified on the basis of spectroscopic data. Aiming at
isolation of 2a and 2b, protonations of 4a and 4b, however,
generate the corresponding complexes 3a and 3b both in about
30% yield as the final products. It is clear that the vinylidene
complex 2 with an imine group is reactive, readily forming the
corresponding complex 3 with a substituted 2H-chromene unit.
We carried out a few experiments in order to find the source of
the added o-cresol moiety in this cyclization reaction.
Possible Pathways for Formation of 3. Several possible
pathways are considered feasible for the formation of 3 from 2.
For example, 3 could be formed by addition of a simple
salicylaldehyde molecule to 2. Presumably hydrolysis of the
imine group of 1 could generate the aldehyde. However, as
shown in Scheme 2, addition of salicylaldehyde to 2b resulted
in no mixed carbene complex, i.e. no cross addition was
1
In the H NMR spectrum of 3b, two resonances at δ 3.82
and 3.75 clearly reveal the presence of two methoxy-substituted
aromatic rings, and the relatively downfield singlet peak at δ
8.83 is assigned to the iminyl NCH proton. The Cα
resonance of the carbene ligand in the 13C NMR spectrum of
2
3b appears as a triplet at δ 260.70 with JCP = 14.5 Hz. In the
mass spectrum, the parent peak at m/z 1014.24 reveals the
composition of the ligand on the metal complex which
apparently results from dimerization of 1b on the metal
accompanied by loss of the propargyl imine group. Character-
istic NMR data of 3a and 3c are similar. Separate reactions of
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Scheme 2. Formations of the cross addition products
Scheme 3. Imine metathesis reactions
considered not feasible. A direct imine metathesis in the
presence of Lewis acid, previously observed by Meyer et al.,24 is
regarded as a reasonable route to give 2a from the mixture of
2b/3b and 7a or 8a. The metathesis process explains the
presence of 3a in the reactions of 2d or 2b with 7a or with 8a,
with no N-propargyl group.
observed. Instead, 3b was isolated as the only product.
Therefore, aldehyde seems to have no effect in the formation
of 3. However, when 1a was added to the mixture of 2b/3b, the
new mixed carbene complex 5, in addition to 3b, see Scheme 2,
was detected by mass spectra, and 3a was also observed.
Treatment of a mixture of 2a/3a with 1b also afforded the
other mixed carbene complex 6 and 3a/3b. On the basis of
these results, it is clear that the imine compound, not aldehyde,
plays the vital role for the formation of the coupling products.
Two possible imine sources exist in our reaction system i.e. the
organic imine compounds 1 and the organometallic vinylidene
complexes 2.
Formation of 3a in the reaction of 2b/3b with 1a is
reasonably explained by the exchange of the whole vinylidene
ligand of 2b with 1a generating 2a then give 3a. To further
explore the reaction, compound 7a, also a semi-salen but with
no propargyl group instead, with an N-allylic group, was reacted
with 2b/3b to yield two expected products 5 and 3b, Scheme 2.
However, 3a is also observed in low yield. The ratio of 5:3b:3a
is approximately 54:42:4. The more stable vinylidene complex
2d was also reacted separately with 7a and an ethyl analogue
8a.23 In both cases, all three carbene complexes 9, 3a, 3d were
detected from mass spectra, with 9 being the major product, see
lower part of Scheme 2.
Indeed, as shown in Scheme 3, exchange reaction between
two Schiff-base-type organic imine compounds 1b and 8a in the
presence of RuCl3 in CDCl3 gives new imine compounds 10
and 1a in 32% conversion in 3 days. The direct imine
metathesis reaction also occurs for the vinylidene complex 2d
and 8a giving 11 and 2a. The quartet and triplet 1H signals at δ
3
3.65 and 1.40 with JHH = 7.34 Hz are assigned to the ethyl
group of 11. The reaction of 2d and 7a forms complex 3a,
albeit in low yield, and 3a is believed to come from the same
imine metathesis reaction. Probably the ruthenium portion
plays the role of Lewis acid.
The requirement of the imine moiety in the vinylidene is
checked by running the following experiments. Two different
vinylidene complexes25 with no imine group, as shown in
Scheme 4, are separately reacted with imine 1b to yield only 2b
Scheme 4. Vinylidene Complexes with No Imine Group
Imine Metathesis. It is interesting that 3a is also observed
in both reactions of 2b with 7a and with 8a. Compounds 7a
and 8a contain no N-propargyl group. Apparently with the
whole vinylidene ligand exchange process it would not be
possible to generate 2a in the reaction. However, 3a is always
observed in addition to the anticipated products 5, 3b, 9 and
3d. Formation of 3a should require 2a, which could form from
exchange of the whole vinylidene ligand of 2b with 1a, or
alternatively, via hydrolysis of the imine bond of 2b followed by
condensation or a direct imine exchange process. The
hydrolysis pathway should require formation of the vinylidene
complex A with an amine group, see Scheme 3. Our attempts to
prepare A by directly treating propargyl amine with [Ru]-Cl
afford a complicated mixture. Complex A is thus believed to be
unstable. Therefore, the hydrolysis pathway leading to 2a is
and 3b. If the imine group on the vinylidene ligand is not
required, cyclization between the vinylidene ligand and 1b
should give the mixed carbene complex H, which is not
observed, indicating that the coupling reaction also requires the
imine functionality on the vinylidene ligand.
In the reaction of 1a with [Ru]-Cl, mentioned above, in
addition to 2a and 3a, the minor side product 12, see Scheme
1, is detected by NMR and mass spectra in the crude product.
In the 31P NMR spectrum of 12, the triplet and doublet signals
at δ 15.79 and 49.73 are assigned to the phosphonium group
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and two phosphine ligands, respectively, showing the pattern of
an acetylide product with a cationic phosphonium group. The
parent peak in the mass spectrum at m/z 991.23 is consistent
with the structure of 12.
The proposed mechanism for the formation of 3 and 12 is
shown in Scheme 5. Complex 3 should be formed mainly from
After purification, the desired vinylidene complex with the
amine group was not observed; instead, a mixture containing
[Ru]-NH3 as the major product was isolated, and the 31P
+
NMR spectrum of the minor product 15 shows a triplet signal
at δ 14.92 and a doublet signal at δ 52.64, expected for a
1
cationic complex with a phosphonium group. In the H NMR
spectrum of 15, a multiplet signal at δ 8.22 is assigned to CαH.
The mass spectrum displays the parent peak at m/z 993.25
consistent with 15. Formation of [Ru]-NH3+ is probably due to
the deprotonation of the ammonium NH4+ salt. In addition, as
expected, 5-methoxy-2-hydroxy-benzaldehyde was also ob-
served in the 1H NMR spectrum. In KPF6, instead of
NH4PF6, and with excess free phosphine added, the reaction
gave 15 and 5-methoxy-2-hydroxybenzaldehyde, 16, in high
yield. As shown in Scheme 6, the vinylidene complex C
probably forms first, then a 1,5-hydrogen shift takes place to
give the imine compound D and complex E.27 Free phosphine
in solution attacks Cγ of E to give 15, and hydrolysis of D gives
16.
Scheme 5. Formation of 3: Two Possible Pathways
CONCLUSIONS
■
In summary, reactions of [Ru]-Cl with N-propargyl semi-salen
compounds first yield vinylidene complexes 2, followed by an
addition reaction, which adds an o-cresol moiety across Cα and
Cβ of the vinylidene ligand of 2, to give carbene complexes 3 as
the final product. The added cresol portion comes from a
molecule with an imine functionality, instead of an aldehyde
group. This is confirmed by observation of various cross
carbene complexes when 2 is reacted with 1. The major
pathway to yield 3 is the reaction of 2 with excess 1. The minor
route is via a dimerization of two vinylidene complexes 2, which
also yield the acetylide complex 12 with a phosphonium group.
In addition, the reaction of [Ru]-Cl with the amine analogue
13b, which retains the propargyl group and phenol moiety, is
also explored. The cationic phosphine addition product 15 is
obtained. Cyclization reaction is observed only in the reaction
of imine.
2 and a semi-salen molecule both with imine functionality. The
coupling is followed by removal of the nitrogen moiety.
Formation of the minor product 12 can be suitably explained
by coupling of two vinylidene complexes. Dimerization of 2
involving the vinylidene ligand and the imine/phenol groups
gives the dinuclear complex B, which undergoes elimination of
the metal vinylidene moiety to afford 3 and A. Deamination of
A is accompanied by addition of a phosphine molecule to give
12. Previously, [2 + 2] cycloaddition between a tungsten
vinylidene complex and an imine compound leading to a C−C
bond formation has been reported.26 Nitrogen atom of the
imine could serve as a nucleophile. The much lower yield of 12
indicates that this coupling pathway using two organometallic
complexes should be a minor route.
Propargyl Amine. As the addition/cyclization reaction of 2
to give 3 requires two imine groups, it is interesting to compare
the chemical reactivity of the corresponding propargyl amine.
Transformation of the imine group into an amine group was
readily achieved by a simple reduction as shown in Scheme 6.
Sodium borohydride is used to reduce 1b to give the
corresponding amine 13b, which was then reacted with [Ru]-
Cl in CH2Cl2 at 40 °C for 12 h in the presence of NH4PF6.
EXPERIMENTAL SECTION
■
General Information. The manipulations were performed under
an atmosphere of dry nitrogen using a vacuum-line and standard
Schlenk techniques unless mentioned otherwise. Solvents were dried
by standard methods and were distilled under nitrogen before use. All
reagents were obtained from commercial suppliers and were used
without further purification. NMR spectra were recorded at room
temperature and are reported in units of δ with residual protons in the
solvents as a standard. Electrospray ionization mass spectrometry,
elemental analysis and X-ray diffraction studies were carried out at the
Regional Center of Analytical Instrument located at the National
Taiwan University. According to the literature methods, [Ru]-Cl
([Ru] = Cp(PPh3)2Ru)28 was prepared from RuCl3·xH2O, which was
purchased from Steam Chemicals. [Ru′]-Cl ([Ru′] = Cp(dppe)Ru)29
was prepared from [Ru]-Cl. Preparation of the imine compounds 7a,
8a and 11 followed the methods in the literature.30−32
Scheme 6. Reactions of the Amine Analogue
Synthesis of 1a. To a Schlenk flask charged with salicylaldehyde
(1.98 g, 16 mmol), propargyl amine (1.07 g, 19 mmol) and MgSO4,
was added 30 mL of toluene under nitrogen. The resulting solution
was stirred at room temperature overnight. The reaction mixture was
extracted with ethyl acetate, and the organic phase was washed with
aqueous NH4Cl and dried over MgSO4. Solvent was then removed
under reduced pressure to give compound 1a (2.45 g, 95% yield).
1
Spectroscopic data for 1a: H NMR (δ, CDCl3): 12.87 (s, 1H, OH);
4
8.66 (t, JHH = 1.79 Hz, 1H, NCH); 6.86−7.33 (m, 4H, Ph); 4.52
4
4
4
(dd, JHH = 1.79 Hz, JHH = 2.45 Hz, 2H, CH2); 2.55 (t, JHH = 2.45
Hz, 1H, CH). 13C NMR (δ, CDCl3): 165.73 (NC); 160.65 (Ph−
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3
OH); 132.53, 131.70, 118.75, 116.99 (Ph, C); 77.47, (C); 76.51
(CH); 45.38 (CH2). MS (EI) m/z: 159.07
7.84 (m, 36H, Ph); 5.14 (s, 5H, Cp); 5.00 (t, JHH = 8.00 Hz, 1H,
CβH); 4.38 (d, JHH = 8.00 Hz, 2H, CH2). 31P NMR (δ, CDCl3):
3
Compound 1b (1.31 g, 94% yield) was similarly prepared from 5-
methoxy salicylaldehyde (1.12 g, 7.4 mmol) and propargyl amine (0.47
42.72 (s, PPh3). MS (ESI+) m/z: 880.20.
Complex 3b (0.059 g, 85% yield) was prepared from 1b (0.031 g,
0.164 mmol), [Ru]-Cl (0.048 g, 0.066 mmol) and NH4PF6 (0.028 g,
0.17 mmol) in CH2Cl2. Spectroscopic data for 3b: 1H NMR (δ,
CDCl3): 12.71 (s, 1H, OH); 8.83 (s, 1H, NCH); 7.64 (s, 1H,
1
g, 8.5 mmol) in toluene. Spectroscopic data for 1b: H NMR (δ,
4
CDCl3): 12.38 (s, 1H, OH); 8.62 (t, JHH = 1.81 Hz, 1H, NCH);
6.82−6.94 (m, 3H, Ph); 4.52 (dd, 4JHH = 1.81 Hz, 4JHH = 2.44 Hz, 2H,
4
CH2); 3.77 (s, 3H, OCH3); 2.56 (t, JHH = 2.44 Hz, 1H, CH). 13C
3
CγH); 6.62−7.67 (m, 48H, Ph); 5.92 (d, JHH = 9.26 Hz, 1H, Ph);
5.13 (s, 2H, CH2); 4.73 (s, 5H, Cp); 3.82, 3.75 (2 s, 6H, 2 OCH3). 13
C
NMR (δ, CDCl3): 165.44 (NC); 154.80, 152.09, 119.64, 118.33,
117.76, 115.16 (Ph, C); 77.45 (C); 76.60 (CH); 55.94
(−OCH3); 45.43 (CH2). MS (EI) m/z: 189.08
2
NMR (δ, CDCl3): 260.63 (t, JCP = 14.7 Hz, Cα); 169.58 (NC);
156.99, 156.64, 154.98, 152.45 (Ph−OH, Ph−OCα, 2Ph−OMe);
147.57 (Ph, C); 136.49−135.91 (PPh3, P−C); 133.31, 130.12,
128.20 (PPh3, C); 107.64−136.49 (Ph, C); 88.72 (Cp); 63.06
(CH2); 55.99, 55.81 (2 OCH3). 31P NMR (δ, CDCl3): 48.72 (s,
PPh3). MS (ESI+) m/z: 1014.24. Anal. Calcd for C60H52F6NO4P3Ru:
C, 62.18; H, 4.52; N, 1.21. Found: C, 61.97; H, 4.24; N, 1.16.
A mixture of 2c/3c (4.1:1, total weight 0.16 g) was prepared from
1c (0.085 g, 0.42 mmol), 5-nitro-salicylaldehyde (0.14 g, 0.82 mmol)
and [Ru]-Cl (0.148 g, 0.20 mmol), NH4PF6 (0.088 g, 0.54 mmol) in
Compound 1c (1.21 g, 95% yield) was prepared from 5-nitro
salicylaldehyde (1.04 g, 6.2 mmol) and propargyl amine (0.41 g, 7.4
mmol). Spectroscopic data for 1c: 1H NMR (δ, CDCl3): 13.98 (s, 1H,
OH); 8.78 (t, 4JHH = 1.82 Hz, 1H, NCH); 8.32 (d, 4JHH = 2.72 Hz,
3
1H, Ph); 8.22 (dd, JHH = 9.16 Hz, 4JHH = 2.72 Hz, 1H, Ph); 7.03 (d,
4
4
3JHH = 9.16 Hz, 1H, Ph); 4.60 (dd, JHH = 1.82 Hz, JHH = 2.45 Hz,
2H, CH2); 2.65 (t, 4JHH = 2.45 Hz, 1H, CH). 13C NMR (δ, CDCl3):
170.09 (Ph−OH); 165.90 (NC); 138.70, 129.95, 129.32, 120.14,
117.97 (Ph, C); 79.63, (C); 78.87 (CH); 44.77 (CH2). MS
(EI) m/z: 204.05
1
CH2Cl2. Spectroscopic data for 2c (from the mixture): H NMR (δ,
CDCl3): 14.00 (s, 1H, OH); 8.78 (s, 1H, NCH); 6.89−7.40 (m,
3
33H, Ph); 5.19 (s, 5H, Cp); 5.08 (t, JHH = 7.95 Hz, 1H, CβH); 4.45
Compound 1d (1.17 g, ∼89% yield) was similarly prepared from 2-
hydroxy-1-naphthaldehyde (1.08 g, 6.3 mmol) and propargyl amine
(0.42 g, 7.6 mmol). After column chromatography, a small amount of
starting material, about 8%, remained in the mixture. Spectroscopic
(d, 3JHH = 7.95 Hz, 2H, CH2). 31P NMR (δ, CDCl3): 42.69 (s, PPh3).
MS (ESI+) m/z: 895.18.
Complex 3c (0.138 g, ∼66% yield) was similarly prepared from 1c
(0.105 g, 0.52 mmol), [Ru]-Cl (0.146 g, 0.20 mmol) and NH4PF6
(0.091 g, 0.56 mmol) in CH2Cl2. Complex 3c decomposed in
chromatographic column. Pure complex 3c was not obtained.
1
data for 1d: H NMR (δ, CDCl3): 14.68 (s, 1H, OH); 9.57 (br, 1H,
4
4
NCH); 7.04−9.57 (m, 6H, Ph); 4.65 (dd, JHH = 2.44 Hz, JHH
=
1.44 Hz, 2H, CH2); 3.11 (t, 4JHH = 2.44 Hz, 1H, CH). 13C NMR (δ,
CD2Cl3): 166.44 (NC); 161.59 (Ph−OH); 135.62, 133.62, 129.65,
128.35, 127.94, 123.79, 121.40, 119.62, 108.85 (Ph, C); 78.27
(C); 76.59(CH); 44.88 (CH2). MS (EI) m/z: 209.08
1
Spectroscopic data for 3c: H NMR (δ, (CD34)2CO): 14.38 (s, 1H,
OH); 9.08 (s, 1H, NCH);8.75, 8.55 (2d, JHH = 2.77 Hz, 2H,
Ph);8.30 (m, 1H, Ph); 8.13 (s, 1H, CγH); 7.05−8.04 (m, 32H, Ph);
6.37 (d, 3JHH = 9.26 Hz, 1H, Ph); 5.63 (s, 2H, CH2); 5.17 (s, 5H, Cp).
Reaction of 1a/Salicylaldehyde with [Ru]-Cl. To a Schlenk flask
charged with [Ru]-Cl (0.097 g, 0.13 mmol) and NH4PF6 (0.054 g,
0.33 mmol), were added 1a (0.025 g, 0.16 mmol), salicylaldehyde
(0.041 g, 0.33 mmol), and 10 mL of CH2Cl2 under nitrogen. The
resulting solution was stirred at room temperature overnight. Then the
solution was filtered through Celite to remove the insoluble
precipitates, and the volatiles of the filtrate were removed under
vacuum. The solid residue was extracted with a small volume of
CH2Cl2 followed by filtration. Addition of 70 mL of diethyl ether and
hexane (1:1) to the filtrate gave precipitates which were collected in a
glass frit, washed with diethyl ether, and dried under vacuum to give a
mixture of 2a and 3a in a ratio of ∼3.6:1. (0.104 g). Complex 2a
underwent further reaction to give 3a. Spectroscopic data for 2a
obtained from the mixture: 1H NMR (δ, CDCl3): 13.22 (s, 1H, OH);
8.14 (s, 1H, NCH); 6.83−7.75 (m, 34H, Ph); 5.15 (s, 5H, Cp);
5.00 (t, 3JHH = 8.12 Hz, 1H, CβH); 4.40 (d, 3JHH = 8.12 Hz, 2H, CH2).
31P NMR (δ, CDCl3): 42.68 (s, PPh3). MS (ESI+) m/z: 850.20.
Reaction of 1a with [Ru]-Cl. Complex 3a (0.15 g, 83% yield) was
similarly prepared from 1a (0.067 g, 0.42 mmol), [Ru]-Cl (0.14 g, 0.19
mmol), and NH4PF6 (0.083 g, 0.51 mmol) in CH2Cl2 but with no
salicylaldehyde added. Spectroscopic data of 3a: 1H NMR (δ, CDCl3):
13.18 (s, 1H, OH); 8.83 (s, 1H, NCH); 6.92−7.67 (m, 38H, Ph);
5.99 (d, 3JHH = 8.49 Hz, 1H, Ph); 5.18 (s, 2H, CH2); 4.75 (s, 5H, Cp).
13C NMR (δ, CDCl3): 268.12 (t, JCP = 13.9 Hz, Cα); 169.08 (N
2
C); 167.53, 161.03 (Ph−OH, Ph−OCα); 148.86, 144.31 (Ph);
135.65−134.93 (PPh3, P−C); 133.12, 130.54, 128.53 (PPh3, C);
115.82−139.53 (Ph, C); 90.49 (Cp); 61.96 (CH2). 31P NMR (δ,
CDCl3): 48.27 (s, PPh3). MS (ESI+) m/z: 1044.19.
Synthesis of 2d. To a Schlenk flask charged with [Ru]-Cl (0.097
g, 0.13 mmol) and NH4PF6 (0.058 g, 0.36 mmol) were added 1d
(0.070 g, 0.335 mmol) and 10 mL of CH2Cl2 under nitrogen. The
resulting solution was stirred at room temperature. Similar procedures
were used to obtain the final product 2d (0.104 g, 84% yield) as an
orange powder. Spectroscopic data for 2d: 1H NMR (δ, CDCl3):
3
14.37 (s, 1H, OH); 8.62 (s, 1H, NCH); 7.75 (d, JHH = 8.25 Hz,
3
3
1H, Ph); 7.69 (d, JHH = 9.27 Hz, 1H, Ph); 7.58 (d, JHH = 8.25 Hz,
3
1H, Ph); 6.93−7.76 (m, 32H, Ph); 6.95 (d, JHH = 9.27 Hz, 1H, Ph);
3
3
5.17 (s, 5H, Cp); 5.08 (t, JHH = 8.11 Hz, 1H, CβH); 4.42 (d, JHH
=
8.11 Hz, 2H, CH2). 13C NMR (δ, CDCl3): 345.72 (t, JCP = 15.3 Hz,
Cα); 158.53 (NC); 134.01−133.20 (PPh3, P−C); 133.00, 130.98,
128.45 (PPh3, C); 107.00−133.61 (Ph, C); 94.85 (Cp); 44.42
(CH2). 31P NMR (δ, CDCl3): 42.07 (s, PPh3). MS (ESI+) m/z:
900.21. Anal. Calcd for C55H46F6NOP3Ru: C, 63.22; H, 4.44; N, 1.34.
Found: C, 63.33; H, 4.21; N, 1.31.
2
Complex 3d (0.090 g, ∼43% yield) was prepared from 1d (0.109 g,
0.52 mmol), [Ru]-Cl (0.145 g, 0.20 mmol) and NH4PF6 (0.110 g, 0.67
mmol) in CH2Cl2 for 7 days. Complex 3d decomposed in the
chromatographic column. No pure complex 3d was obtained.
Spectroscopic data for 3d: 1H NMR (δ, CDCl3): 14.94 (s, 1H,
OH); 9.58 (s, 1H, NCH); 8.45 (s, 1H, CγH); 6.78−7.79 (m, 41H,
Ph); 6.05 (d, 3JHH = 9.06 Hz, 1H, Ph); 5.32 (s, 2H, CH2); 4.78 (s, 5H,
2
13C NMR (δ, CDCl3): 264.40 (t, JCP = 14.7 Hz, Cα); 169.71 (N
C); 160.91, 160.29 (Ph−OH, Ph−OCα); 147.63 (Ph, C); 136.27−
135.84 (m, PPh3, P−C); 133.42, 130.20, 128.24 (PPh3, C); 114.97−
136.41 (Ph, C); 89.21 (Cp); 62.91 (CH2). 31P NMR (δ, CDCl3):
48.93 (s, PPh3). MS (ESI+) m/z: 954.22. Anal. Calcd for
C58H48F6NO2P3Ru: C, 63.39; H, 4.40; N, 1.27. Found: C, 62.46; H,
4.32; N, 1.21. The minor side product 12 was observed in the crude
Cp). 13C NMR (δ, CDCl3): 258.31 (t, JCP = 15.4 Hz, Cα); 171.12
(NC); 163.16, 162.27 (Ph−OH, Ph−OCα); 147.31 (Ph); 114.66−
136.64 (Ph, C); 88.94 (Cp); 59.35 (CH2). 31P NMR (δ, CDCl3):
48.69 (s, PPh3). MS (ESI+) m/z: 1054.25.
Synthesis of 3a′. To a Schlenk flask charged with NH4PF6 (0.068
g, 0.417 mmol) and Cp(dppe)RuCl (0.097 g, 0.16 mmol) were added
1a (0.064 g, 0.402 mmol) and 10 mL of MeOH under nitrogen. The
reaction at 45 °C overnight yielded product 3a′ (0.112 g, 84% yield) as
a red powder. Single crystals were grown from a CH2Cl2/diethyl ether
2
1
product without purification. Spectroscopic data for 12: H NMR (δ,
2
CDCl3): 5.91 (d, JHP = 9.28 Hz); 4.00 (s, 5H, Cp). 31P NMR (δ,
CDCl3): 49.73 (d, JPP = 5.6 Hz, 2P, 2Ru−PPh3); 15.79 (t, JPP = 5.6 Hz,
1P, PPh3). MS (ESI+) m/z: 991.23.
A mixture of 2b/3b (1.8:1, total weight 0.18 g) was prepared from
1b (0.047 g, 0.25 mmol), 5-methoxy-salicylaldehyde (0.079 g, 0.52
mmol), [Ru]-Cl (0.152 g, 0.21 mmol) and NH4PF6 (0.091 g, 0.56
1
mmol) in CH2Cl2. Spectroscopic data for 2b (from the mixture): H
1
NMR (δ, CDCl3): 12.70 (s, 1H, OH); 8.17 (s, 1H, NCH); 6.62−
solution. Spectroscopic data of 3a′: H NMR (δ, CDCl3): 13.13 (s,
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1H, OH); 8.72 (s, 1H, NCH); 6.85−7.49 (m, 26H, Ph); 6.33 (d,
3JHH = 8.53 Hz, 1H, Ph); 4.96 (s, 5H, Cp); 4.89 (d, 2H, CH2); 3.22,
2.98 (two m, 4H, 2 dppe CH2). 13C NMR (δ, CDCl3): 264.86 (t, 2JCP
= 13.2 Hz, Cα); 169.43 (NC); 141.21−140.91, 136.44−136.14
(dppe, P−C); 115.21−133.63 (Ph, C; dppe, C); 89.35 (Cp);
64.31 (CH2). 31P NMR (δ, CDCl3): 90.59 (s, dppe). MS (ESI+) m/z:
828.17. Anal. Calcd for C48H42F6NO2P3Ru: C, 59.26; H, 4.35; N, 1.44.
Found: C, 59.33; H, 4.33; N, 1.42.
6.61 (m, 1H, Ph); 5.99 (d, 3JHH = 8.33 Hz, 1H, Ph); 4.76 (s, 5H, Cp).
31P NMR (δ, CDCl3): 49.04 (s, PPh3). MS (ESI+) m/z: 984.22.
Reaction of 2a with 1b. A mixture of 2a/3a in a ratio of 3.1:1.
(0.113 g) was reacted with 1b (0.023 g, 0.12 mmol) at room
temperature. The final product was similarly obtained as a mixture of
1
3a, 3b, and 6 in a ratio of 0.6:0.4:1. Attempts to obtain the H NMR
data of 6 failed due to the same reason mentioned above. Partial
spectroscopic data for 6: 1H NMR (δ, CDCl3): 8.82 (s, 1H, NCH);
3
6.00 (d, JHH = 8.64 Hz, 1H, Ph); 4.75 (s, 5H, Cp); 3.76 (s, 3H,
Complex 3b′ (0.179 g, 82% yield) was prepared from 1b (0.116 g,
0.613 mmol), Cp(dppe)RuCl (0.147 g, 0.245 mmol), and NH4PF6
(0.102 g, 0.626 mmol) in MeOH at 45 °C. Spectroscopic data for 3b′:
1H NMR (δ, CDCl3): 12.72 (s, 1H, OH); 8.70 (s, 1H, NCH);
OCH3). 31P NMR (δ, CDCl3): 48.89 (s, PPh3). MS (ESI+) m/z:
984.22.
Synthesis of 9. To a Schlenk flask charged with 2d (0.062 g, 0.069
mmol) was added 8a (0.024 g, 0.16 mmol) in 1.5 mL of CDCl3 at
room temperature. Similar procedures were used to obtain the final
crude products including 9 and trace amount of 3a and 3d.
Recrystallization from diethyl ether/CH2Cl2 gave 9 (0.052 g, 75%
3
6.66−7.72 (m, 27H, Ph); 6.25 (d, JHH = 9.14 Hz, 1H, Ph); 5.00 (s,
5H, Cp); 4.85 (s, 2H, CH2); 3.81, 3.68 (2 s, 2H, 2 OCH3); 3.16, 2.96
2
(two m, 4H, 2 dppe CH2). 13C NMR (δ, CDCl3): 260.13 (t, JCP
=
13.2 Hz, Cα); 168.87 (NC); 139.74−139.38, 135.06−134.67 (dppe,
P−C); 131.56−128.61 (dppe, C); 121.54−107.64 (Ph, C);
107.63−139.74 (Ph, C); 87.61 (Cp); 63.07 (CH2); 55.88, 55.64 (2
1
yield) as an orange powder. Spectroscopic data for 9: H NMR (δ,
3
CDCl3): 14.77 (s, 1H, OH); 9.40 (s, 1H, NCH); 8.32 (d, JHH
=
3
8.40 Hz, 1H, Ph); 7.77 (d, JHH = 9.20 Hz, 1H, Ph); 7.65 (s, 1H,
2
OCH3); 28.97 (t, JCP = 22.1 Hz, dppe).31P NMR (δ, CDCl3): 90.34
3
CγH); 6.92−7.63 (m, 37H, Ph); 6.02 (d, JHH = 8.40 Hz, 1H, Ph);
(s, dppe). MS (ESI+) m/z: 888.20. Anal. Calcd for C50H46F6NO4P3Ru:
C, 58.14; H, 4.49; N, 2.69. Found: C, 57.97; H, 4.24; N, 2.59.
Synthesis of 4a. To a Schlenk flask charged with [Ru]-Cl (0.147 g,
0.19 mmol), K2CO3 (0.052 g, 0.38 mmol), and KPF6 (0.095 g, 0.52
mmol) were added 1a (0.048 g, 0.30 mmol) and 15 mL of CH2Cl2
under nitrogen. The resulting solution was stirred at room temperature
for 3 days, and then CH2Cl2 was removed under vacuum. The product
was redissolved in CH2Cl2, and the mixture was filtered through Celite
to remove the insoluble precipitates followed by reprecipitation by
addition of 50 mL of MeOH. Precipitates thus formed were collected
in a glass frit, washed with MeOH, and dried under vacuum to give the
final product 4a (0.105 g, 61% yield) as light-yellow powder.
Spectroscopic data for 4a: 1H NMR (δ, CDCl3): 14.20 (s, 1H,
OH); 8.80 (t, 4JHH = 1.80 Hz, 1H, NCH); 7.06−7.46 (m, 31H, Ph);
6.90 (d, 3JHH = 8.31 Hz, 1H, Ph); 6.61 (m, 1H, Ph); 6.50 (m, 1H, Ph);
5.16 (s, 2H, CH2); 4.80 (s, 5H, Cp). 13C NMR (δ, CDCl3): 264.16 (t,
2JCP = 14.5 Hz, Cα); 172.12 (NC); 163.00, 160.33 (Ph−OH, Ph−
OCα); 147.21 (Ph, C); 136.23−135.80 (PPh3, P−C); 133.39,
130.23, 128.72 (PPh3, C); 136.95−108.28 (Ph, C); 89.35 (Cp);
58.55 (CH2). 31P NMR (δ, CDCl3): 48.44 (s, PPh3). MS (ESI+) m/z:
1004.25. Anal. Calcd for C62H50F6NO2P3Ru: C, 64.81; H, 4.39; N,
1.22. Found: C, 64.97; H, 4.43; N, 1.26.
Metathesis of Imine. To an NMR tube charged with 1b (0.045 g,
0.24 mmol) and 8a (0.036 g, 0.24 mmol) were added RuCl3 (12 mg,
0.046 mmol) and 1.5 mL of CDCl3. The resulting solution was kept at
room temperature for 3 days. Four compounds 1a, 1b, 8a, and 10 were
observed in the final mixture. The 1b:10 ratio of 2.1:1 is determined
by the 1H NMR spectrum. Spectroscopic data for 10 from the mixture:
1H NMR (δ, CDCl3): 12.87 (br, 1H, OH); 8.29 (br, 1H, NCH);
6.74−7.33 (m, 4H, Ph); 3.76 (s, 3H, OCH3); 3.61 (q, 3JHH = 7.30 Hz,
4
4.74 (d, JHH = 1.80 Hz, 2H, CH2); 4.31 (s, 5H, Cp). 13C NMR (δ,
3
2H, CH2); 1.30 (t, JHH = 7.30 Hz, 3H, CH3). MS (EI) m/z: 179.12.
CDCl3): 164.16 (NC); 161.73 (Ph−OH); 139.32−138.50 (PPh3,
Synthesis of 13b. To a Schlenk flask charged with 1b (0.026 g,
1.38 mmol), were added NaBH4 (0.11g, 2.89 mmol) and 20 mL of
EtOH under nitrogen. The resulting solution was stirred at room
temperature overnight. The solution was extracted with a mixture of
ether/aqueous NH4Cl solution, and the organic phase was separated
and dried over MgSO4. After filtration, solvent was then removed
under reduced pressure to give 13b (0.23 g, 87% yield). Spectroscopic
data for 13b: 1H NMR (δ, CDCl3): 6.52−6.76 (m, 3H, Ph); 5.34 (br,
2H, OH and NH); 4.02 (s, 2H, Ph−CH2); 3.72 (s, 3H, OCH3); 3.43
P−C); 133.79, 130.20, 127.17 (PPh3, C); 119.07−116.79 (Ph, 
2
C); 109.39 (t, JCP = 24.5 Hz, Cα); 103.66 (Cβ); 84.94 (Cp); 48.80
(CH2). 31P NMR (δ, CDCl3): 50.63 (s, PPh3). MS (ESI+) m/z:
850.19. Anal. Calcd for C51H43NOP2Ru: C, 72.16; H, 5.11; N, 1.65.
Found: C, 72.13; H, 5.09; N, 1.63.
Complex 4b (0.114 g, 62% yield) was similarly prepared from 1b
(0.059 g, 0.31 mmol), [Ru]-Cl (0.152 g, 0.21 mmol), K2CO3 (0.050 g,
0.37 mmol), and KPF6 (0.102 g, 0.55 mmol) in CH2Cl2 at room
1
4
4
temperature. Spectroscopic data for 4b: H NMR (δ, CDCl3): 13.57
(d, JHH = 2.41 Hz, 2H, CH2); 2.28 (t, JHH = 2.41 Hz, 1H, CH).
13C NMR (δ, CDCl3): 152.51, 151.57 (Ph−OH, Ph−OCH3); 122.26,
116.69, 114.60, 113.80 (Ph, C); 80.15 (C); 72.71 (CH); 55.66
(OCH3); 50.73 (Ph−CH2); 36.44 (CH2). MS (EI) m/z: 191.11
Synthesis of 15. To a Schlenk flask charged with [Ru]-Cl (0.097
g, 0.13 mmol) and KPF6 (0.068 g, 0.37 mmol) were added 13b (0.031
g, 0.16 mmol), PPh3 (0.18 g, 0.69 mmol), and 10 mL of CH2Cl2 under
nitrogen. After 6 days the resulting solution was filtered through Celite
to remove the insoluble precipitates, then the volatiles were removed
under vacuum, and the solid residue was extracted with a small volume
of CH2Cl2 followed by reprecipitation by adding 70 mL of Et2O.
Precipitates thus formed were collected and dried under vacuum to
give yellow powder 15 (0.095 g, 72% yield). Spectroscopic data for 15:
1H NMR (δ, CDCl3): 8.21 (m, 1H, Cα−H); 6.96−7.77 (m, H, Ph);
(s, 1H, OH); 8.72 (s, 1H, NCH); 6.74−7.48 (m, 32H, Ph); 5.86 (d,
4JHH = 2.96 Hz, 1H, Ph); 4.77 (s, 2H, CH2); 4.30 (s, 5H, Cp); 3.37 (s,
3H, OCH3). 13C NMR (δ, CDCl3): 163.99 (NC); 155.43 (Ph−
OH); 151.24 (Ph−OMe); 139.39−138.56 (PPh3, P−C); 133.77,
128.49, 127.18 (PPh3, C); 118.87−114.15 (Ph, C); 109.14 (t,
2JCP = 24.3 Hz, Cα); 103.89 (Cβ); 85.05 (Cp); 55.64 (CH2); 48.92
(OCH3). 31P NMR (δ, CDCl3): 50.40 (s, PPh3). MS (ESI+) m/z:
880.20. Anal. Calcd for C52H45NO2P2Ru: C, 71.06; H, 5.16; N, 1.59.
Found: C, 71.02; H, 5.13; N, 1.56.
Protonations of 4a and 4b by excess HBF4 for 1 d gave 3a and 3b in
31% and 34% yields, respectively, as determined by NMR.
Reaction of 2b with 1a. To a mixture of 2b/3b in a ratio of 2.6:1
(0.155 g) in CH2Cl2, prepared as mentioned before, was added 1a
(0.024 g, 0.15 mmol), and the solution was stirred at room
temperature overnight. The solution was filtered through Celite to
remove the insoluble precipitates followed by precipitation by addition
of 60 mL of diethyl ether/hexane (1:1). Precipitates thus formed were
collected in a glass frit, washed with diethyl ether, and dried under
vacuum. The final product was obtained as a mixture of 3a, 3b, and 5
in a ratio of 0.08:0.8:1. Three complexes are not separable by
chromatography. Due to extensive overlaps, no attempt was made to
obtain complete 1H NMR data of 5 from the mixture. Partial
spectroscopic data for 5: 1H NMR (δ, CDCl3): 8.83 (s, 1H, NCH);
2
5.24 (m, 1H, Cβ−H); 4.06 (s, 5H, Cp); 3.83 (dd, JHP = 12.59 Hz,
3JHH = 6.35 Hz, 2H, CH2). 13C NMR (δ, CDCl3): 165.27 (m, Cα);
138.75 (m, Cβ); 139.14−138.34 (PPh3, P−C); 134.82−118.56 (PPh3,
2
C); 85.60 (Cp); 33.25 (d, JCP = 42.4 Hz, CH2). 31P NMR (δ,
CDCl3): 52.64 (d, JPP = 4.3 Hz, 2P, 2Ru−PPh3); 14.93 (t, JPP = 4.3
Hz, 1P, PPh3). MS (ESI+) m/z: 993.25. Anal. Calcd for
C62H54F6P4Ru: C, 65.43; H, 4.78. Found: C, 65.80; H, 4.97.
Single-Crystal X-ray Diffraction Analyses. Single crystals of 3a′
suitable for X-ray diffraction study were grown as mentioned above. A
single crystal of dimensions 0.25 × 0.20 × 0.15 mm3 was glued to a
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glass fiber and mounted on a CCD diffractometer. The diffraction data
were collected using 3-Kw sealed-tube Mo Kα radiation (T = 295 K).
Exposure time was 5 s per frame. SADABS33 (area detector
absorption) absorption correction was applied, and decay was
negligible. Data were processed, and the structure was solved and
refined by the SHELXTL34 program. Hydrogen atoms were placed
geometrically using riding model with thermal parameters set to 1.2
times that for the atoms to which the hydrogen is attached.
(12) List, B.; Pojarliev, P.; Biller, W. T.; Martin, H. J. J. Am. Chem.
Soc. 2002, 124, 827−833.
(13) (a) Qin, D.-D.; Yang, Z.-Y.; Zhang, F.-H.; Du, B.; Wang, P.; Li,
T.-R. Inorg. Chem. Commun. 2010, 13, 727−729. (b) Rezaeifard, A.;
Sheikhshoaie, I.; Monadi, N.; Alipour, M. Polyhedron 2010, 29, 2703−
2709. (c) Thakurta, S.; Butcher, R. J.; Pilet, G.; Mitra, S. J. Mol. Struct.
2009, 929, 112−119.
(14) Kotali, A.; Nasiopoulou, D. A.; Harris, P. A.; Helliwell, M.; Joule,
J. A. Tetrahedron 2012, 68, 761−766.
(15) (a) Daru, J.; Stirling, A. J. Org. Chem. 2011, 76, 8749−8755.
(b) Kuarm, B. S.; Madhav, J. V.; Rajitha, B. Synth. Commun. 2012, 42,
1770−1777.
ASSOCIATED CONTENT
* Supporting Information
■
S
CIF file giving crystallographic data of compound 3a′. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(16) Raju, B. C.; Tiwari, A. K.; Kumar, J. A.; Ali, A. Z.; Agawane, S. B.
Bioorg. Med. Chem. 2010, 18, 358−365.
(17) (a) Jang, Y.-J.; Syu, S.; Chen, Y.-J.; Yang, M.-C.; Lin, W. Org.
Biomol. Chem. 2012, 10, 843−847. (b) Suzuki, K.; Ubukata, T.;
Yokoyama, Y. Chem. Commun. 2012, 48, 765−767.
AUTHOR INFORMATION
Corresponding Author
*E-mail: yclin@ntu.edu.tw
■
(18) (a) Bustelo, E.; Jimenez-Tenorio, M.; Puerta, M. C.; Valerga, P.
Organometallics 2007, 26, 4300−4309. (b) Pino-Chamorro, J. A.;
Bustelo, E.; Puerta, M. C.; Valerga, P. Organometallics 2009, 28, 1546−
1557.
Notes
(19) (a) Cadierno, V.; Díez, J.; Gamasa, M. P.; Gimeno, J.; Lastra, E.
Coord. Chem. Rev. 1999, 193 − 195, 147−205. (b) Gamasa, M. P.;
Gimeno, J.; Martin-Vaca, B. M.; Isea, R.; Vegas, A. J. Organomet. Chem.
2002, 651, 22−33. (c) Louie, J.; Grubbs, R. H. Organometallics 2002,
21, 2153−2164.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research is supported by the National Science Council,
(now the Department of Science and Technology), the
Republic of China.
(20) (a) Lichtenberger, D. L.; Renshaw, S. K.; Bullock, R. M. J. Am.
Chem. Soc. 1993, 115, 3276−3285. (b) Touchard, D.; Haquette, P.;
Pirio, N.; Toupet, L.; Dixneuf, P. H. Organometallics 1993, 12, 3132−
3139. (c) Hudson, D. M.; Valente, E. J.; Schachner, J.; Limbach, M.;
Mueller, K.; Schanz, H.-J. ChemCatChem. 2011, 3, 297−301.
(21) (a) Conroy-Lewis, F. M.; Simpson, S. J. J. Organomet. Chem.
1990, 396, 83−94. (b) Faller, J. W.; Ma, Y.; Smart, C. J.; DiVerdi, M. J.
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