Cyclization Reactions of Aryl Propargyl Acetates with Tethered Epoxide Induced by Ruthenium Complex

Article abstract of DOI:10.1002/asia.201701070

Reactions of the ruthenium complex [Ru]Cl ([Ru]=Cp(PPh₃)₂Ru; Cp=η⁵-C₅H₅) with several aryl propargyl acetates, each with an ortho-substituted chain of various length containing an epoxide on the aromatic ring and with or without methyl substitutents on the epoxide ring, bring about novel cyclizations. The cyclization reactions of HC≡CCH(OAc)(C₆H₄)CH₂(RC₂H₂O) (R=H, 6 a; R=CH₃, 6 b, where RC₂H₂O is an epoxide ring) in MeOH give the vinylidene complexes 5 a–b, respectively, each with the Cβ integrated into a tetrahydro-5H-benzo[7]annulen-6-ol ring. A C?C bond formation takes place between the propargyl acetate and the less substituted carbon of the epoxide ring. Further cyclizations of 5 a–b induced by HBF₄ give the corresponding vinylidene complexes 8 a–b each with a new 8-oxabicyclo-[3.2.1]octane ring by removal of a methanol molecule in high yield. For similar aryl propargyl acetates with a shorter epoxide chain, the cyclization gives a mixture of a vinylidene complex with a tetrahydronaphthalen-1-ol ring and a carbene complex with a tricyclic indeno-furan ring. For the cyclization of 18, with a longer epoxide chain, opening of the epoxide is required to afford the vicinal bromohydrin 22, then tandem cyclization occurs in one pot. Products are characterized by spectroscopic methods as well as by XRD analysis.

Full text of DOI:10.1002/asia.201701070

CHEMISTRY
AN ASIAN JOURNAL
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Accepted Article
Title: Cyclization Reactions of Aryl Propargyl Acetates with Tethered
Epoxide Induced by Ruthenium Complex
Authors: Yi-Jhen Feng, Yi-Hsin Chen, Shou-Ling Huang, Yi-Hung Liu,
and Ying Chih Lin
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Cyclization Reactions of Aryl Propargyl Acetates with Tethered
Epoxide Induced by Ruthenium Complex
Yi-Jhen Feng,[a] Yi-Hsin Chen,[a] Shou-Ling Huang,[a] Yi-Hung Liu,[a] and Ying-Chih Lin,*[a]
Dedication ((optional))
Abstract: Reactions of the ruthenium complex [Ru]Cl ([Ru] =
Cp(PPh3)2Ru; Cp = η5-C5H5) with several aryl propargyl acetates,
each with ortho-substituted chain of various length containing epoxide
on the aromatic ring and with or without methyl substitutents on the
epoxide ring, bring about novel cyclizations. The cyclization reactions
of HC≡CCH(OAc)(C6H4)CH2(RC2H2O) (R = H, 6a; R = CH3, 6b, where
RC2H2O is an epoxide ring) in MeOH give the vinylidene complexes
5a-b, respectively, each with the Cβ integrated into a tetrahydro-5H-
benzo[7]annulen-6-ol ring. A C-C bond formation takes place between
the propargyl acetate and the less substituted carbon of the epoxide
ring. Further cyclizations of 5a-b induced by HBF4 give the
corresponding vinylidene complexes 8a-b each with a new 8-
oxabicyclo-[3.2.1]octane ring by removal of a methanol molecule in
high yield. For similar aryl propargyl acetates 11a-c, each with a
shorter epoxide chain, the cyclization gives mixture of the vinylidene
complex 13 with a tetrahydronaphthalen-1-ol ring and the carbene
complex 14 with a tricyclic indeno-furan ring. In the direct reaction of
[Ru]Cl with aryl propargyl acetates 18, tethering a longer epoxide
chain, no cyclization involving C-C or C-O bond formation is observed.
However, if opening of the epoxide ring of 18 is first carried out to
afford the vicinal bromohydrin 22, then tandem cyclization of 22
induced by [Ru]Cl in MeOH generates the vinylidene complex 23 with
9-oxabicyclo[4.2.1]nonane ring in one pot. All of these reaction
products are characterized by spectroscopic methods. In addition, the
structures of six complexes 4, 5b, 8a, 8b, 14a and 15b have been
confirmed by X-ray diffraction analysis.
provides an useful method for the synthesis of many carbo- and
heterocycles derivatives.4 Metal-mediated intra and inter-
molecular carbon-carbon bond formations between alkynes and
double bonds such as alkene, allene, ketone, aldehyde and
imines have been extensively investigated.5,6 Various metal
carbene, vinylidene, allenylidene and acetylide complexes have
been verified to be key intermediates for many alkyne
transformations.7 It is now well established that metal vinylidene
complexes are readily formed from metal acetylides and
electrophiles.7g,h,i Metal-catalyzed cyclization of epoxide-alkyne
was recently found as an effective method to give complicated
cyclic products.8 Marson reported that Sn(OTf)2- or SnBr4 induced
alkyne-epoxide cyclization leading to carbocyclic compounds.8a
Several metal salts prompting the coupling of epoxide and alkyne
via a one-electron radical process have been reported in the
literature.9a,b However, these reactions generally require excess
amount of metal reagent. Gansauer found that catalytic amount
of Ti(III) is sufficient to perform radical epoxide-alkyne cyclization
in the presence of excess Mn powder.9c The metal-catalyzed
isomerization of alkynyl epoxides was found to give furan
derivatives10 and the inter- and intramolecular reductive coupling
of alkyne-epoxide catalyzed by Ni complex have been reported.11
The cascade alkyne-epoxide cyclization of (o-ethynyl)phenyl
epoxides catalyzed by Ru complex is known to proceed via a
metal-acyl or -ketene intermediates to give indene and cyclohexa-
2,4-dien-1-one derivatives.8c,12 Recently, Au- and Pt-catalyzed
cyclizations of alkyne epoxide were found to afford complicated
cyclic products.8d,e,f,h,i,l,m,n,13 Hashmi and Liu independently studied
the
gold-catalyzed
cycloisomerization
of
2-epoxy-1-
Introduction
alkynylbenzenes to afford indenyl ketones via gold α-
carbonylcarbenoids intermediate.8h,l,n,i Liu also reported that the
Pt-catalyzed aromatization of 2-oxiranyl-1-(methoxyalk-2-
ynyl)benzene formed 2-naphthyl aldehydes through a 1,3-
carbonyl shift. Similarly catalytic cyclizations of epoxide
substrates bearing an acyloxy group proceed via an initial 1,3-
acyloxy shift, followed by an intramolecular attack of an allenyl
acetate at the epoxide, giving 2-naphthyl ketones. However, the
reactions on epoxide substrates bearing a siloxy group gave
bicyclic ketals with high diastereoselectivity.13 We previously
studied the reaction of epoxide-alkyne with [Ru]Cl in alcohol
affording the bicyclic oxacarbene complexes via cascade
cyclization/ring expansion.14 Recently, we also reported the
ruthenium-mediated tandem cyclization reactions of aromatic
propargylic enynes with various methyl substituents on the
olefinic portion, which afforded tricyclic carbo- and heterocyclic
compounds.15 As the 8-oxabicyclo[3.2.1]octane system and its
fused analogues form a fundamental class of compounds which
include hydroazulenoid diterpene natural products,16 construction
of seven- or eight-membered oxabicyclic ring continues to
Compounds with carbo- or heterocyclic skeleton attract a great
deal of interest because these frame are important substructures
in many natural products and drugs.1,2 Developement of effective
strategies for the preparation of these cyclic compounds remains
a challenge for organic synthesis.3 During the past decade,
transition metal-catalyzed cyclization reactions have drawn
attention resulting in widespread scientific explorations because
the presence of the metal-containing nonclassical carbocations
[a]
Y. J. Feng, Y. H. Chen, S. L. Huang, Y. H. Liu Prof. Dr. Y. C. Lin,.
Department of Chemistry
National Taiwan University
Taipei, 106 (Taiwan)
Fax: (+886) 223636359
E-mail: yclin@ntu.edu.tw
Supporting information for this article is given via a link at the end of
the document.
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10.1002/asia.201701070
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present an appreciable challenge, particularly when stereo-
controlled placement of the multiple chiral centers is required.8a,17
The general methods to access the oxabicyclo[3.2.1.]-octane
system were via [3.4]cyclizations18 and annulations.19 As an
extension of our previous study, we explore ruthenium-mediated
reactions of aromatic propargylic acetate containing an epoxide
instead of an olefinic part. The cyclization is found to proceed via
generation of a metal acetylide intermediate, leading further to an
intramolecular cyclization with cleavage of the carbon-carbon or
carbon-oxygen bond of the epoxide.9,10a,20 Herein, we report our
results on the ruthenium-mediated cycloisomerizations of alkynyl
epoxide to give complexes with diversified carbo- and
heterocyclic ring. The tandem cyclization of a new propargylic
alcohol containing both hydroxyl and halo groups is also disclosed.
This reaction sequence leads to the development of allenylidene
cyclization and a general route to the bridged bicycle ethers.
mixture of 6a (diastereomer 1:1) and [Ru]Cl is heated to 50°C to
give 5a (diastereomer 1:0.12) in higher yield. Treatment of the
alkynyl epoxide 6b with [Ru]Cl in the presence of KF/KPF6 in
MeOH also affords the diastereoisomers of 5b in a ratio of 1:0.1,
as shown in Scheme 2.
[Ru] = Cp(PPh3)2Ru
[Ru]Cl, KF, KPF6,
MeOH, 50C
OAc
R
MeO
C
[Ru]
R
O
HO
6a
6b
5a
, R = H
5b, R = CH3
, R = H
, R = CH3
OMe
[Ru]
or
HBF4,
MeOH
NH4PF6,
CDCl3
NH4PF6,
CH2Cl2
[Ru]Cl
[Ru]
O
R
A
H
KF
H
MeOH
C
C
O
R
C
[Ru]
O
R
8a
, R = H
Results and Discussion
7a
, R = H
7b, R = CH3
8b
, R = CH3
Cyclization Raction of Alkynyl Epoxide. The reaction of aryl
propargyl alcohol 1a containing an ortho-substituted allyl group
on the aryl ring with m-chloroperbenzoic acid (mCPBA) gave the
epoxide product 3a together with a side product 2a in a ratio of
3.7:1, see Scheme 1. The epoxide 3a with a hydroxyl group is
isolable, but is unstable and slowly transforms to 2a, possibly by
attack of the hydroxyl group to cause opening of the epoxide ring.
Treatment of 3a with [Ru]Cl ([Ru] = Cp(PPh3)2Ru; Cp = η5-C5H5)
in the presence of KF/KPF6 in MeOH at 50°C for 1 day affords the
vinylidene complex 5a with a newly formed seven-membered ring
with two stereogenic centers. The diastereo-isomers are
observed in a ratio of 1:0.1.
Scheme 2. Cyclization of alkynyl epoxides 6a and 6b.
The structures of 5a, 5b and 4 are determined by NMR
spectroscopy and complexes 5b and 4 are further characterized
fully by single-crystal X-ray diffraction analysis. In the 2D-HMBC
NMR spectrum of the major isomer of 5a, the triplet peak at δ
2
349.08 with Jcp = 15.1 Hz, assigned to Cα, shows correlations
with the 1H resonances at δ 4.72, 2.85 and 2.52 assigned to the
CγH and the nearby methylene group, respectively. The multiple
peak at δ 3.76, assigned to CH(OH), shows correlations with the
13C resonances at δ 124.22 assigned to Cβ.21c,d The 2D-HMBC
NMR spectrum of 5b also displays similar correlations. In the 2D-
HMBC NMR spectrum of 4, the broad peak at δ 308.41, assigned
to Cα, shows correlations with the 1H resonances at δ 5.38, 3.50
and 3.28 assigned to CγH and to the nearby methylene group,
respectively. The triplet 1H peak at δ 5.38 also displays long-range
correlation with the resonance of the methyl substituted carbon
atom. Single crystals of complexes 5b and 4 are obtained
separately at 5°C. The structures are determined by single crystal
X-ray diffraction analysis. Two ORTEP type views of 5b and 4 are
shown in Figure 1. The structure of 5b with a tetrahydro-5H-
benzo[7]annulen-6-ol ring bonded at the vinylidene ligand
confirms the C-C bond formation. The vinylidene ligand is bound
to the ruthenium in a nearly linear fashion with a Ru-C(1)-C(2)
angle of 170.6(3)°. The Ru-C(1) (1.857(3) Å) and C(1)-C(2)
(1.311(5) Å) bond lengths compare well with those found in other
ruthenium-vinylidene complexes and support the vinylidene
formulation.21c,d Opening of the epoxide ring followed by a C-C
bond formation with addition of an OMe group at C(3) leads to the
seven-membered ring. As shown in the crystal structure of 4, the
dioxabicyclo[4.3.1]decane ring bound to the metal is a typical
alkoxy-carbene ligand.
OH
OH
CH2Cl2
R = H
O
OH
+
mCPBA
2a
R
O
3a
1a, R = H
1b
, R = CH3
[Ru]Cl
KPF6
[Ru] = Cp(PPh3)2Ru
CH2Cl2
mCPBA
R = CH3
MeO
C
[Ru]Cl,
KPF6
[Ru]
O
OH
O
[Ru]
O
H
HO
5a
4
2b
Scheme 1. Reactions of 3a and 2b obtained from epoxidation of 1a and 1b.
Treatment of the analogous propargyl alcohol 1b containing one
methyl group at the internal carbon of the olefinic group with
mCPBA yields only 2b, the expected epoxide analogous to 3a is
not observed. Reaction of 2b with [Ru]Cl in the presence of KPF6
in MeOH at 50°C for 1 day gives the carbene complex 4. In order
to better control the reaction by lowering the nucleophilicity, the
hydroxyl group is replaced by an acyloxy group. Acetylations of
1a and 1b followed by epoxidation give the corresponding
epoxide products 6a and 6b each with an acyloxy group. The
Interestingly, the diastereomeric mixture of 5a in the presence of
NH4PF6 in CDCl3 undergoes
a slow cyclization at room
temperature to give the vinylidene complex 8a with a new 8-
oxabicyclo-[3.2.1]octane ring by removal of a methanol molecule
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10.1002/asia.201701070
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in high yield. In the absence of NH4PF6, no cyclization is observed. hydroxy-vinylidene intermediate followed by dehydration to form
Complex 5b in the presence of NH4PF6 in CDCl3 is also converted
to the corresponding 8b. The rate of cyclization reactions of 5a
and 5b are enhanced upon heating. In addition, protonation of 5
with HBF4 in MeOH also yields 8. Namely, the cyclization of 5
requires acidic condition.
7. In MeOH, addition of a methoxide at Cγ generates the acetylide
intermediate A. Protonation at the epoxide then promotes
nucleophilic addition of Cβ of the acetylide ligand to the methylene
group of the epoxide ring leading to 5. The nucleophilic character
of Cβ of an acetylide ligand was previously reported.21 For the
transformation of 5 to 8, the presence of HBF4 or other acidic salt
might promote removal of a methanol molecule to afford 8.
Figure 1. Two ORTEP drawings of complexes 5b (a) and 4 (b). For clarity, aryl
groups of two PPh3 ligands on Ru, except the ipso carbons, are omitted (thermal
ellipsoids are set at the 50% probability level) for both complexes.
Figure 2. Two ORTEP drawings of complexes 8a (a) and 8b (b). For clarity, aryl
groups of the PPh3 ligands on Ru, except the ipso carbons, are omitted (thermal
ellipsoids are set at the 50% probability level).
The structures of both 8a and 8b are determined by NMR
spectroscopy and single crystal X-ray diffraction analysis. In the
2D-HMBC NMR spectrum of 8a, the triplet peak at δ 340.89 with
2Jcp = 15.3 Hz, assigned to Cα, shows correlation with the singlet
1H resonance at δ 5.82 assigned to the nearby bridgehead CH
group, which shows correlation with the 13C resonance at δ 75.72
assigned to the other bridgehead CH group on the ring. The triplet
peak at δ 4.80 with 3JHH = 6.3 Hz, assigned to the bridgehead CH
group, shows correlations with the 13C resonances at δ 131.27
assigned to Cβ. The 2D NMR data of 8b also display similar
correlations. Single crystals of 8a and 8b are obtained from
MeOH/hexanes at 5°C. Two ORTEP type views of 8a and 8b are
shown in Figure 2. In both cases, formation of the C‒O bond is
accompanied with removal of OMe group at Cγ. Interestingly, in
CH2Cl2, the reactions of 6a and 6b with [Ru]Cl in the presence of
NH4PF6 yields the allenylidene complexes 7a and 7b, respectively,
see Scheme 2. Further treatments of 7a and 7b with KF in MeOH
at 50°C then afford the corresponding 5a and 5b.
The cyclization mentioned above proceeds via nucleophilic
addition of Cβ to the less substituted methylene carbon of the
epoxide ring. Presumably, the steric crowd on this methylene
carbon could influence the addition, thus the epoxide 6c with two
gem-methyl groups on the epoxide ring is prepared, and the
nucleophilic addition is not expected to occur. Indeed, as shown
in Scheme 3, in the reaction of 6c with [Ru]Cl in the presence of
KF/KPF6 in MeOH, no cyclization reaction occurs, instead, the
acetylide complex 9 and the methoxycarbene complex 10 are
obtained in a ratio of 1.6:1. The reaction, carried out in
NH4PF6/CH2Cl2, gives the allenylidene complex 7c, which upon
heating to 50°C in MeOH for one day in the presence of KF gives
10 as the only product. Noticeably, the steric hindrance of two
gem-methyl groups on the epoxide ring inhibits the nucleophile
addition.
The pathway leading to the formation of 8 is proposed as shown
in Scheme 2. The reaction of 6 first proceeds via formation of a γ-
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OAc
OMe
resonances at δ 120.69 assigned to Cβ. These spectroscopic
data clearly reveal the C-C bond formation.
[Ru]Cl
[Ru]
10
KF, KPF6,
O
O
MeOH, 50C
OAc
9
6c
[Ru]Cl
OAc
H
[Ru]
C
C
[Ru]
[Ru]-Cl
[Ru]-Cl
O
OMe
NH PF ,
4
NH4PF6,
CH2Cl2
CH2Cl2
NH4PF6,
CH2Cl2
6
O
O
[Ru]
O
15b
H
12a
11a
11b
MeOH, 50C
C
O
C
[Ru]
MeOH KF
O
KF
KF, KPF6,
MeOH, 50C
KF, KPF6,
MeOH, 50C
[Ru]-Cl
[Ru]
[Ru]-Cl
13a
10
MeO
7c
OMe
MeO
C
[Ru]
C
[Ru]
O
Scheme 3. Reaction of dimethyl-substituted epoxide 6c with [Ru]Cl.
OH
OH
13a
14a
13b
Cyclization Reaction of Epoxide 11. Functionalized six-, seven-
and eight-membered ring fused to an aromatic ring and related
analogues found in natural products are known to display a broad
range of biological activities.22 With the protocol to prepare seven-
membered ring via Ru-mediated cyclization of alkynyl epoxide,
we reason that the chain length of the tethering epoxide could be
modified to vary the ring size of the product. Three epoxides 11a-
11c, see Scheme 4 and 6 below, each with a shorter chain
tethered on the aryl ring, are prepared. Treatment of 11a with
[Ru]Cl in the presence of KF/KPF6 in MeOH at 50°C affords the
vinylidene complex 13a and the carbene complex 14a in a ratio
of 5.8:1, see Scheme 4. Purification by passing the mixture
through an Al2O3 packed column yields the carbene complex 14a
as a yellow band, while 13a decomposes. Methanol is required
for the cyclization because, the reaction in CH2Cl2 produces only
the allenylidene complex 12a, which, in MeOH, is converted to
13a. The reaction of [Ru]Cl with the epoxide 11b, with a methyl
group on the epoxide ring in the presence of KF/KPF6 in MeOH at
50°C gives only the vinylidene complex 13b as a mixture of
diastereomers in a ratio of 1:0.8. Interestingly, the reaction of 11b
with [Ru]Cl in the presence of NH4PF6 in CH2Cl2 gives the carbene
complex 15b containing two fused five-membered rings like the
carbon ring skeleton of 14a. No allenylidene complex similar to
12a is observed. As mentioned above, complexes 5a and 5b each
with both methoxy and hydroxyl substitutents on the
benzo[7]annulene ring undergo further cyclization in acidic
environment. However, no further cyclization is observed for 13a
and 13b both also containing methoxy and hydroxyl groups on the
six-membered ring.
Scheme 4. Cyclization of 11a and 11b with [Ru]Cl.
The 2D-HMBC spectrum of 13b displays similar correlations
revealing the cyclic structure. In the 2D-COSY spectrum of 14a,
the resonance at δ 4.71 assigned to CβH, shows correlation with
the resonances at δ 5.50 and 2.92, assigned to the two adjacent
CH groups. In the 2D-HMBC spectrum of 14a, both 13C
resonances at δ 299.57 and 82.13 assigned to Cα and Cβ,
respectively, show correlations with the 1H resonances at δ 4.18
and 4.01 assigned to the methylene group.
The structures of 13a-b, 14a and 15b are also established by a
series of 2D NMR studies, mass spectra, and solid state
structures of 14a and 15b are determined by single crystal X-ray
diffraction analysis. For 13a with two stereogenic centers,
diastereoisomers in a ratio of 1:0.4 are observed. In the 2D-HMBC
spectrum of diastereomeric mixture of 13a, the two triplet peaks
at δ 345.66 and 343.78 both with 2Jcp = 15.1 Hz assigned to Cα of
the minor and major products, show correlations with 1H
resonances at δ 3.24, 2.93 and 3.20, 2.78, assigned to the
methylene group of the two products, respectively. The 13C
resonances at δ 72.85 and 72.12 assigned to the corresponding
Cγ show correlations with the related 1H resonances of
neighboring methylene groups. The triplet peak at δ 4.92 with 3JHH
= 4.5 Hz, assigned to CH(OH), shows correlations with the 13C
Figure 3. TwoORTEP drawings of 14a (a) and 15b (b). For clarity, aryl groups
of two PPh3 ligands on Ru, except the ipso carbons, are omitted (thermal
ellipsoids are set at the 50% probability level).
For 15b, the triplet peak at δ 271.57 with 2Jcp = 13.6 Hz assigned
1
to Cα shows correlations with the H resonances at δ 8.01 and
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10.1002/asia.201701070
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4.25, 2.97 assigned to CγH and the nearby methylene group,
respectively.
different indeno[2,1-c]furan units, and 17c are characterized by
2D NMR and mass spectroscopy. The NMR data of 14c and 14a
are similar. In the 2D-COSY spectrum of 14c, the multiplet
resonance at δ 5.08 assigned to CβH shows correlations with two
1H resonances at δ 5.65 and 3.19 assigned to the adjacent CγH
and bridgehead CH groups, thereby revealing the C-C bond
formation. In the 2D-HMBC spectrum of 16c, the long range cross
The structures of 14a and 15b, shown as two ORTEP type views
in Figure 3, are both with tricyclic indenofuran skeletons as the
carbene ligand bonded to the metal, testifying the C‒C and O‒C
bond formations. For 14a, the addition of an OMe group at C(3) is
clearly seen (Fig. 3a) and no OMe group is seen for 15b (Fig. 3b).
For 15b, the bond length 1.352(6) Å of C(2)‒C(3) indicates a
double bond, and the relatively short single bond distance
1.457(6) Å for C(1)‒C(2) suggests a contribution of zwitterionic
resonance form for a regular ruthenium oxo carbene complex.23
Rational mechanism for the formation of 13a-b, 14a and 15b is
shown in Scheme 5. The allenylidene intermediate 12a is first
formed from 11a, followed by an addition of a methoxy group at
Cγ to generate the acetylide intermediate B. Then, for the
conversion of 11a to 13a, a C-C bond formation takes place by
the pathway i, namely, a nucleophilic addition of Cβ of the
acetylide ligand to the methylene group of the epoxide ring,
forming 13a with a six-membered ring. However, the formation of
14a from 11a via B might proceed through a different pathway ii
with an altered nucleophilic addition triggering a C-C bond
formation between Cβand the methine carbon of the epoxide ring
yielding C with an –OH group. A subsequent nucleophilic attack
of the oxygen atom to Cα gives D. Protonation of D then leads to
14a with a tricyclic indeno-furan ring.
1
peak between the H resonance at δ 4.19 assigned to CH2 and
the 13C resonance at δ 171.44 assigned to Cd (see Scheme 6 for
labelling) also reveals the C-C bond formation. Nucleophilic
addition can only occur at the non-methyl substituted carbon of
the epoxide ring giving two carbene complexes 14c and 16c along
with the formation of 17c, retaining the epoxide ring. Because the
ring opening caused by nucleophilic addition to the dimethyl-
substituted carbon of the epoxide is now prohibited, a vinylidene
complex similar to 13b is not observed. For the formation of 14c,
the ring opening accompanied with a C-C bond formation at the
less substituted carbon of the epoxide ring, as mentioned above,
is followed by the second cyclization via nucleophilic addition of
oxygen to Cα of the vinylidene ligand. Subsequent removal of a
methanol molecule is followed by shift of the double bond at Cc
to give 16c. Complexes 14, 15 and 16 all contain different tricyclic
indenofuran skeletons, which are key substructures of GR-24,27
leucosceptroid A,28 ramelteon,29 Solanacol30 and (−)-
galiellalactone.31.
OAc
OMe
H
OMe
OMe
[Ru]
c
OAc
H
[Ru]
[Ru]
[Ru]Cl
[Ru]
a
O
11b
15b
[Ru]
b
11a
12a
13a
14a
KF, KPF6
O
H
O
O
e
d
MeOH
50C
G
D
i
O
17c
O
11c
14c
16c
OMe
MeO
AcO
OAc
[Ru]
[Ru]
HO
ii
i
C
C
[Ru]
[Ru]
ii
Scheme 6. Reaction of [Ru]Cl with 11c.
HO
O

HO
E
F
C
B
H
Scheme 5. Proposed Mechanism for Cyclization of 11a and 11b.
Tandem Cyclization of the Propargyl Acetate with Vicinal
Bromohydrins. To expand the scope of the cyclization, two
similar alkynyl compounds 18a and 18b both with a longer
tethered epoxide chain are prepared. Treatment of 18a with
[Ru]Cl in MeOH affords a mixture of the methoxycarbene complex
19a and the acetylide complex 20a. Similarly 18b gives 19b and
20b. However, in both cases, no epoxide ring opening thus
leading to cyclization product is observed, see Scheme 7.
In CH2Cl2, two reactions yield the allenylidene complexes 21a and
21b. In MeOH, complex 21 undergoes nucleophilic addition of the
OMe group from the solvent onto Cα and Cγ of the allenylidene
ligand to afford 19 and 20, respectively. The non-occurrence of
the ring-opening and cyclization could be attributed to a longer
thus more flexible carbon chain which makes the approach of the
nucleophilic Cβ carbon to the epoxide ring more difficult. In
addition, an eight-membered ring is harder to form than either a
six- or a seven-membered ring due to the increased torsional
strain.
In the reaction of 11b containing a methyl group on the epoxide
ring in the presence of NH4PF6, protonation at the epoxide oxygen
yields the intermediate E.24 Nucleophilic addition of Cβ to the
tertiary methyl-substituted carbon of the epoxide affords the
vinylidene intermediate F with a newly formed five-membered ring.
Electronic effect seems to play a crucial role in determining the
exclusive formation of F. Then nucleophilic addition of the oxygen
atom to Cα of the vinylidene ligand yields the intermediate G.
Deacetylation of G finally leads to 15b. The structural motifs of the
organic ligands of 13a and 13b are similar to that observed for
Conduritols,25 which derivatives have been found to possess
antibiotic, anti-leukemic, growth regulating4 and inhibitory activity
for glycosidases.26
The reaction of [Ru]Cl with the epoxide 11c, containing two gem-
methyl groups on the epoxide ring, in the presence of KF/KPF6 in
MeOH, yields three carbene products 14c:16c:17c in a ratio of
1:1.3:0.4, see Scheme 6. The mixture is passed through an Al2O3
column, giving 16c as the first olive band. The second band
contains a mixture of 14c and 17c. Complexes 14c, 16c, with
To achieve synthesis of compound analogous to 8 but with an
eight-membered ring, we take an altered tactic. It was previously
reported that vicinal bromohydrins can be obtained by opening of
an epoxide ring with dilithium tetrabromocuprate (Li2CuBr4) with
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10.1002/asia.201701070
Chemistry - An Asian Journal
FULL PAPER
nucleophilic addition of bromide at the less substituted epoxide
carbon.32 We therefore perform the ring opening reaction of the
epoxide 18a and 18b with Li2CuBr4 affording the corresponding
bromohydrins 22a and 22b both containing one hydroxyl group as
a nucleophile and one bromo group as a good leaving group.
such substructures are frequently found in bioactive natural and
non-natural products.33
OAc
OAc
[Ru]Cl
CuBr2, LiBr
O
C
n
[Ru]
KF, KPF6,
MeOH, 50C
THF
Br
n
OAc
n
OH
R
O
H
R
R
23a
, R = H, n = 1
[Ru]
O
C C
18a
18b
, R = H, n = 1
, R = CH3, n = 1
[Ru]-Cl
22a, R = H, n = 1
22b
23b, R = CH3, n = 1
8a, R = H, n = 0
, R = CH3, n = 1
NH4PF6,
CH2Cl2
6a, R = H, n = 0
24a,
R = H, n = 0
O
R
- Br-
R
18a, R = H
18b, R = CH3
21a, R = H
21b, R = CH3
H
C
C
[Ru]
R
KF, KPF6,
- H+
[Ru]Cl
n
[Ru]
OH
MeOH, 50C
n
O
OMe
R
OMe
Br
[Ru]
O
H
[Ru]
O
I
Br
R
Scheme 8. Cyclization of vicinal bromohydrins 22a, b and 24a with [Ru]Cl.
R
19a,
19b,
R = H
R = CH3
20a,
20b,
R = H
R = CH3
Esteruelas' group has shown that the Cβ=Cγ bond of electrophilic
allenylidenes undergoes Diels–Alder reactions to afford
vinylidenes with the Cβ incorporated into a ring.34a They also
reported that terminal alkynals are useful substrates for
generating such vinylidene complexes which are easily prepared
by dehydrative cyclization of these terminal alkynals in the
presence of several transition-metal compounds in a single
step.34b-c And we have reported that the nucleophilic addition of
propargyl Grignard reagents to Cγ of an allenylidene ligand and
subsequent cyclization of the resulting diyne catalyzed by gold
complex yielded a vinylidene with the Cβ incorporated into a five-
membered ring.35a-b Reported in this paper, vinylidene complexes
5, 8, 13 or 23 with the Cβ integrated into a ring structure are
readily prepared in high yield. We imagine that with even more
complicated ring structure motif, these complexes are expected
to display interesting bioactivity.
Scheme 7. Reaction of [Ru]Cl with alkynyl epoxides 18
Treatment of [Ru]Cl with 22a in the presence of KF/KPF6 in MeOH
at 50°C affords directly the vinylidene complex 23a via two
consecutive cyclization processes, Scheme 8. The structure of
23a is determined by NMR and mass spectroscopy. In the HMBC
2
spectrum of 23a, the triplet peak at δ 345.24 with Jcp = 15.8 Hz
assigned to Cα shows the correlation with the 1H resonances at δ
5.89, 3.71 and 3.49 assigned to the bridgehead CH and the
nearby methylene group, respectively. The multiple peak at δ 4.46,
assigned to the bridgehead CH group, shows correlations with the
13C resonances at δ 128.64 assigned to Cβ.The bridgehead H
1
resonance at δ 5.89 also shows correlation with the 13C
resonance at δ 81.38 assigned to another bridgehead CH, clearly
revealing the formation of both C-C and C-O bonds. The
resembling cyclization of 22b with an additional methyl group, with
[Ru]Cl under the same reaction condition affords the desired
cyclization product 23b in high yield, as shown in Scheme 8.
Interestingly, the reaction of the analogous bromohydrins 24a
containing a shorter tethering chain, obtained from 6a, with [Ru]Cl
also gives the vinylidene complex 8a directly. As mentioned
above, the ruthenium-assisted cyclization of 6a could also give 8a
but in two separate steps.
Conclusions
A facile and efficient method is developed for the synthesis of
organomtallic ruthenium complexes which ligands contain eight-
and seven-membered oxabicyclic ring by cascade intramolecular
C‒C/C‒O bond formation. These complexes are prepared from
the reactions of [Ru]Cl with aryl propargyl acetates with tethered
epoxide group at the ortho-position of the phenyl ring. In the
[Ru]Cl-induced cyclization reactions of several such compounds,
the propargyl acetate gives much better yields than the
corresponding propargyl alcohol. Two stepwise cyclizations are
observed. The first step involves a C-C bond formation of Cβ of
the propargyl unit and one of the carbon atoms of the epoxide ring,
followed by a C-O bond formation of the epoxide oxygen with Cα
or Cγ of the propargyl unit. For the first part, the reaction proceeds
via an acetylide ligand thus promoting nucleophilic addition of Cβ
to one of carbon atoms of the epoxide ring. Addition to the more
substituted carbon is only observed for the aryl propargyl
compounds with a shorter chain. Transformation of the epoxide
ring to bromohydrins by dilithium tetrabromocuprate facilitates the
The proposed pathway for the tandem cyclization is also shown
in Scheme 8. The reaction might proceed via the allenylidene
intermediate H, followed by nucleophilic addition of the hydroxyl
group to the electrophilic Cγ of the allenylidene ligand with a C-O
bond formation to give the acetylide intermediate I. Subsequent
intramolecular nucleophilic addition of Cβ to the electrophilic
bromo-substituted carbon, causing a C-C bond formation, affords
the vinylidene complex with the oxo-bridge seven- or eight-
membered ring. The bromo atom serves as a good leaving group
for electrophilic addition and assists the second cyclization
process.
Vinylidene complexes with the Cβ atom included in five- or six-
membered rings7i attracted a great of deal of interest because
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10.1002/asia.201701070
Chemistry - An Asian Journal
FULL PAPER
68.72 (CH(maj)), 65.63 (CH(min)), 56.32 (OCH3(min)), 55.99 (OCH3(maj)), 43.44
(CH2(maj)), 41.27 (CH2(min)), 30.15 (CH2(maj)), 29.57 (CH2(min)). 31P NMR (161
MHz, CDCl3): δ 42.12, 41.53 (2d, 2Jpp = 27.6 Hz, 2 PPh3(min)), 41.73, 40.29
(2d, 2Jpp = 27.4 Hz, 2 PPh3(maj)). Anal. Calcd for C54H49O2P2Ru: C, 72.63;
H, 5.53. Found: C, 72.71; H, 5.47. MS: m/z .893.2251 [M] +..
tandem cyclization of the bromohydrins with the propargyl unit
induced by [Ru]Cl in a single step directly.
Experimental Section
Synthesis of 5b. Complex 5b (211 mg, 86% yield) was similarly prepared
from [Ru]Cl (200 mg, 0.27 mmol), 6b (99 mg, 0.41 mmol), KPF6 (99 mg,
0.54 mmol) and KF (47 mg, 0.81 mmol) in MeOH at 50 ºC for 1day.
Spectroscopic data for 5b: 1H NMR (500 MHz, CDCl3): Mixture of
diastereomers (1/0.1): δ 7.37-6.73 (m, Ph), 5.17 (s, 5H, Cp(maj)), 5.07 (s,
5H, Cp(min)), 4.81 (s, 1H, CH(min)), 4.79 (s, 1H, CH(maj)), 3.55 (d, 2JHH = 13.3
General procedures: The manipulations were performed under an
atmosphere of dry nitrogen using vacuum-line and standard Schlenk
techniques. Solvents were dried by standard methods and distilled under
nitrogen before use. The ruthenium complex Cp(PPh3)2RuCl36 was
prepared by following the methods reported in the literature. The C and H
analyses and X-ray diffraction studies were carried out at the Regional
Center of Analytical Instrument at the National Taiwan University. Mass
spectra were recorded using a LCQ Advantage (ESI) and Finnigan MAT
95S (EI) Mass Spectrometers. NMR spectra were recorded on Bruker
AvanceIII-400 or DMX-500 FT-NMR spectrometers at room temperature
(unless stated otherwise). 1H NMR and 13C NMR spectra were obtained in
CDCl3 and CD2Cl2 at ambient temperature and chemical shifts are
expressed in parts per million (δ, ppm). Proton chemical shifts are
referenced to δ 7.26 (CDCl3), 5.32 (CD2Cl2), 7.15 (C6D6), and 2.05
(acetone-d6). Carbon chemical shifts are referenced to δ 77.1 (CDCl3),
53.92 (CD2Cl2), 127.69 (C6D6), and 205.36 and 28.99 (acetone-d6). The
31P NMR spectra were measured relative to external 85% phosphoric acid.
Both 13C and 31P spectra were proton decoupled spectra.
2
Hz, 1H, CH2(maj)), 3.41 (d, JHH = 14.0 Hz, 1H, CH2(min)), 3.24 (br, 1H,
2
OH(maj)), 3.09 (s, 3H, OCH3(min)), 2.95 (s, 3H, OCH3(maj)), 2.68 (d, JHH
=
13.3 Hz, 1H, CH2(maj)), 2.61 (d, 2JHH = 13.8 Hz, 1H, CH2(maj)), 2.24 (d, 2JHH
= 13.8 Hz, 1H, CH2(min)), 2.02 (m, 1H, CH2(maj)), 1.25 (s, 3H, CH3(min)), 1.08
(s, 3H, CH3(maj)). 13C NMR (125 MHz, CDCl3): δ 349.91 (t, 2Jcp = 14.6 Hz,
2
Cα(maj)), 347.20 (t, Jcp = 14.9 Hz, Cα(min)), 139.38-126.44 (Ph and =C),
124.07 (Cβ(maj)), 94.03 (Cp(maj)), 78.57 (CH(maj)), 70.70 (C(OH)(maj)), 68.58
(C(OH)(min)), 56.20 (OCH3(min)), 55.88 (OCH3(maj)), 47.45 (CH2(min)), 46.95
(CH2(maj)), 35.09 (CH2(maj)), 34.49 ( CH2(min)), 31.20 (CH3(min)), 27.65
(CH3(maj)). 31P NMR (161 MHz, CDCl3): δ 42.58, 41.66 (2d, 2Jpp = 27.3 Hz,
2 PPh3(min)), 41.86, 41.58 (2d, AB pattern, 2Jpp = 27.3 Hz, 2 PPh3(maj)). Anal.
Calcd for C55H51O2P2Ru: C, 72.83; H, 5.67. Found: C, 72.90; H, 5.61. MS:
m/z .907.2408 [M] +.
Synthesis of 4. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 2b (83 mg, 0.41
mmol) and KPF6 (99 mg, 0.54 mmol) in MeOH (40 mL) was stirred at 50
ºC for 1 day. Then the solvent was removed under vacuum and CH2Cl2
(20 mL) was used to extract the crude product and the mixture was filtered
through Celite to remove the insoluble precipitates. Volume of the filtrate
was reduced to ca. 5 mL and the residue was added to a stirred
hexanes/diethyl ether (40/40 mL) to produce the olive precipitates, which
were collected, washed with diethyl ether and dried under vacuum to give
complex 4 (212 mg, 88 % yield). Spectroscopic data for 4: 1H NMR (500
Synthesis of 7a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 6a (93 mg,
0.41 mmol) and NH4PF6 (88 mg, 0.54 mmol) in CH2Cl2 (40 mL) was stirred
at ambient temperature for 1 day. The mixture was filtered through Celite
to remove the insoluble precipitates. Volume of the filtrate was reduced to
ca. 5 mL and the residue was added to a stirred solution of diethyl ether
(60 mL) to produce brown precipitates, which were collected, washed with
diethyl ether and dried under vacuum to give complex 7a (176 mg, 76 %
yield). Spectroscopic data for 7a: 1H NMR (500 MHz, CDCl3): δ 9.71 (s,
1H, CγH), 7.66-7.06 (m, 34H, Ph), 5.08 (s, 5H, Cp), 3.40 (dd, 2JHH = 15.0
2
3
2
MHz, CDCl3): δ 7.41-6.71 (m, 34H, Ph), 5.38 (t, JHH = 7.1 Hz 1H, CH),
Hz, JHH = 3.5 Hz, 1H, CH2), 3.26 (m, 1H, CH(epo)), 3.13 (dd, JHH = 15.0
Hz, 3JHH = 6.3 Hz, 1H, CH2), 2.83 (t, 3JHH = 4.4 Hz, 1H, CH2(epo)), 2.58 (dd,
2JHH = 4.8 Hz, 3JHH = 2.6 Hz, 1H, CH2(epo)). 13C NMR (125 MHz, CDCl3): δ
2
4.87 (br, 1H, CH2), 4.83 (s, 5H, Cp), 3.50 (d, JHH = 12.6 Hz, 1H, CH2),
3.28 (d, 2JHH = 12.6 Hz, 1H, CH2), 2.70 (d, 2JHH = 17.4 Hz, 1H, CH2), 2.48
2
(br, 1H, CH2), 2.40 (d, JHH = 17.4 Hz, 1H, CH2), 0.62 (s, 3H, CH3). 13C
2
308.03 (t, Jcp = 18.0 Hz, Cα), 216.35 (Cβ), 149.66 (CγH), 141.19-128.26
(Ph), 93.81 (Cp), 51.85 (CH(epo)), 46.85 (CH2(epo)), 35.56 (CH2). 31P NMR
(161 MHz, CDCl3): δ 47.11 (s, PPh3). Anal. Calcd for C53H45OP2Ru: C,
73.94; H, 5.27. Found: C, 74.24; H, 5.39. MS: m/z 861.1989 [M] +.
NMR (125 MHz, CDCl3): δ 308.41 (br, Cα), 136.40-125.36 (Ph and =C),
91.47 (Cp), 79.34 (CH2), 69.26 (CH), 68.94 (CH), 67.73 (CH2), 43.83 (CH2),
25.92 (CH3). 31P NMR (161 MHz, CDCl3): δ 47.23, 42.96 (2d, 2Jpp = 28.9
Hz, 2 PPh3). Anal. Calcd for C54H49O2P2Ru: C, 72.63; H, 5.53. Found: C,
72.72; H, 5.49. MS: m/z .893.2251 [M] +.
Synthesis of 7b. Complex 7b (168 mg, ca. 71% yield) was similarly
prepared from [Ru]Cl (200 mg, 0.27 mmol), 5b (99 mg, 0.41 mmol),
NH4PF6 (88 mg, 0.54 mmol) in CH2Cl2 at ambient temperature for 1 day.
Spectroscopic data for 7b: 1H NMR (500 MHz, CDCl3): δ 9.69 (s, 1H, CγH),
Synthesis of 5a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 6a (93 mg,
0.41 mmol), KPF6 (99 mg, 0.54 mmol) and KF (47 mg, 0.81 mmol) in
MeOH (40 mL) was stirred at 50 ºC for 1 day. Then the solvent was
removed under vacuum and CH2Cl2 (20 mL) was used to extract the crude
product and the mixture was filtered through Celite to remove the insoluble
precipitates. Volume of the filtrate was reduced to ca. 5 mL and the residue
was added to a stirred hexanes/diethyl ether (40/40 mL) to produce the
olive precipitates, which were collected, washed with diethyl ether and
2
7.63-7.08 (m, 34H, Ph), 5.06 (s, 5H, Cp), 3.35 (d, JHH = 14.92 Hz, 1H,
2
2
CH2), 3.16 (d, JHH = 14.92 Hz, 1H, CH2), 2.63 (d, JHH = 4.45 Hz, 1H,
CH2(epo)), 2.54 (d, 2JHH = 4.45 Hz, 1H, CH2(epo)), 1.36 (s, 3H, CH3). 13C NMR
(125 MHz, CDCl3): δ 307.56 (t, 2Jcp = 18.04 Hz, Cα), 215.01 (Cβ), 150.50
(CγH), 141.62-128.20 (Ph), 93.75 (Cp), 56.57 (C(CH3)(epo)), 52.96 (CH2(epo)),
39.03 (CH2), 21.35 (CH3). 31P NMR (161 MHz, CDCl3): δ 47.18 (s, PPh3).
Anal. Calcd for C54H47OP2Ru: C, 74.13; H, 5.41. MS: m/z 875.2146 [M] +.
Pure complex 7b was not obtained.
dried under vacuum to give complex 5a (202 mg, 84
% yield).
Spectroscopic data for 5a: 1H NMR (500 MHz, CDCl3): Mixture of
diastereomers (1:0.12): δ 7.37-6.48 (m, 34H, Ph), 5.14 (s, 5H, Cp(maj)), 5.08
(s, 5H, Cp(min)), 4.83 (s, 1H, CH(min)), 4.72 (s, 1H, CH(maj)), 4.15 (m, 1H,
CH(mim)), 3.76 (m, 1H, CH(maj)), 3.43 (m, 1H, CH2(min)), 3.39 (m, 1H, CH2(maj)),
Synthesis of 7c. Complex 7c (163 mg, 68 % yield) was similarly prepared
from [Ru]Cl (200 mg, 0.27 mmol), 5c (105 mg, 0.41 mmol), NH4PF6 (88
mg, 0.54 mmol) in CH2Cl2 at ambient temperature for 1 day. Spectroscopic
data for 7c: 1H NMR (400 MHz, CDCl3): δ 9.58 (s, 1H, CγH), 7.74-6.94 (m,
34H, Ph), 5.09 (s, 5H, Cp), 3.21 (m, 2H, CH2 and CH(epo)), 2.98 (m, 1H,
CH2(epo)), 1.45 (s, 3H, CH3), 1.34 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3):
δ 307.56 (t, 2Jcp = 18.04 Hz, Cα), 215.01 (Cβ), 150.50 (CγH), 141.62-128.20
(Ph), 93.75 (Cp), 56.57 (C(CH3)(epo)), 52.96 (CH2(epo)), 39.03 (CH2), 21.35
3.13 (s, 3H, OCH3(maj)), 3.08 (s, 3H, OCH3(min)), 2.86 (m, 2H, CH2(maj)
,
CH2(min)), 2.84 (m, 1H, CH2(maj)), 2.76 (d, 2JHH = 14.0 Hz, 1H, CH2(min)), 2.58
(br, 1H, OH(maj)), 2.52 (dd, 2JHH = 13.5 Hz, 3JHH = 2.6 Hz, 1H, CH2(maj)), 2.42
2
3
(dd, JHH = 14.0 Hz, JHH = 4.8 Hz, 1H, CH2(min)). 13C NMR (125 MHz, C-
DCl3): δ 349.08 (t, 2Jcp = 15.1 Hz, Cα(maj)), 347.97 (t, 2Jcp = 15.1 Hz, Cα(min)),
139.11-126.50 (Ph and =C), 124.22 (Cβ(maj)), 94.11 (Cp), 77.26 (CH(maj)),
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10.1002/asia.201701070
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2
(CH3). 31P NMR (161 MHz, CDCl3): δ 46.82 (s, PPh3). Anal. Calcd for
C55H49OP2Ru: C, 74.31; H, 5.56. MS: m/z 889.2302 [M] +. Pure complex
7c was not obtained
51.16, 50.74 (2d, AB pattern, Jpp = 37.1 Hz, 2 PPh3). Anal. Calcd for
C56H52O2P2Ru: C, 73.11; H, 5.70. MS: m/z 921.2564 [M+1]+.
Spectroscopic data for 10: 1H NMR (400 MHz, CDCl3): δ 7.99-7.03 (m,
3
35H, Ph and =CH), 6.33 (d, JHH = 16.8 Hz, 1H, =CH), 4.88 (s, 5H, Cp),
3.65 (s, 3H, CH3), 2.76 (m, 2H, CH(epo) and CH2), 2.55 (dd, 2JHH = 13.6 Hz,
3JHH = 6.0 Hz, 1H, CH2), 1.29 (s, 3H, CH3), 1.21 (s, 3H, CH3). 13C NMR
(100 MHz, CDCl3): δ 298.51 (t, Jcp = 13.4 Hz, Cα), 139.19-127.51 (Ph),
126.20 (=CH), 123.99 (=CβH), 91.42 (Cp), 64.13 (CH(epo)), 63.81 (OCH3),
58.92 ((CH3)2C(epo)), 33.13 (CH2), 24.73 (CH3), 18.92 (CH3). 31P NMR (161
MHz, CDCl3): δ 46.25, 44.96 (2d, 2Jpp = 30.2 Hz, 2 PPh3). Anal. Calcd for
C56H53O2P2Ru: C, 73.03; H, 5.80. MS: m/z 921.2564 [M]+.
Synthesis of 8a. Method A: A solution of HBF4 (48%, 0.02 mL, 0.11 mmol)
in MeOH (20 mL) was added dropwise at 0 ºC to a stirred solution of 5a
(200 mg, 0.22 mmol) in 20 mL of MeOH. Immediately, insoluble solid
precipitated but the addition was continued until no further solid was
formed. The solution was then decanted, and the tangerine solid was
washed with diethyl ether and dried in vacuum to yield 8a (163 mg, 86%
yield). Method B: A mixture of [Ru]Cl (100 mg, 0.14 mmol), 6a (64 mg,
0.351 mmol) , KPF6 (50 mg, 0.28 mmol) and KF (24 mg, 0.41 mmol) in
MeOH (20 mL) was stirred at ambient temperature for 1 day. The mixture
was filtered through Celite to remove the insoluble precipitates. The filtrate
was concentrated to ca. 5 mL and added to a stirred diethyl ether (60 mL)
to produce the tangerine precipitates, which were collected, washed with
diethyl ether and dried under vacuum to give complex 8a (132 mg, 90%
yield). Spectroscopic data for 8a: 1H NMR (500 MHz, CDCl3): δ 7.37-6.75
(m, 33H, Ph), 5.82 (s, 1H, CH), 5.65 (d, 3JHH = 7.5 Hz, 1H, Ph), 5.05 (s, 5H,
Cp), 4.80 (t, 3JHH = 6.3 Hz, 1H, CH), 3.95 (dd, 2JHH = 14.4 Hz, 3JHH = 7.2
Hz, 1H, CH2), 3.26 (dd, 2JHH = 17.2 Hz, 3JHH = 5.4 Hz, 1H, CH2), 3.07 (d,
2JHH = 14.4 Hz, 1H, CH2), 2.57 (d, 2JHH = 17.2 Hz, 1H, CH2). 13C NMR (125
MHz, CDCl3): δ 340.89 (t, 2Jcp = 15.3 Hz, Cα), 139.77-123.17 (Ph and =C),
131.27 (Cβ), 94.45 (Cp), 75.72 (CH), 74.93 (CH), 35.70 (CH2), 34.80 (CH2).
31P NMR (161 MHz, CDCl3): δ 43.50, 40.41 (2d, 2Jpp = 26.8 Hz, 2 PPh3).
Anal. Calcd for C53H45OP2Ru: C, 73.94; H, 5.27. Found: C, 74.01; H, 5.33.
MS: m/z 861.1989 [M]+.
2
Synthesis of 13a and 14a. A mixture of [Ru]Cl (300 mg, 0.41 mmol), 11a
(133 mg, 0.62 mmol), KPF6 (151 mg, 0.82 mmol) and KF (72 mg, 1.23
mmol) in MeOH (40 mL) was stirred at 50 ºC for 1day. The solvent was
removed under vacuum and CH2Cl2 (20 mL) was used to extract the crude
product and the mixture was filtered through Celite to remove the insoluble
precipitates. The filtrate was concentrated to ca. 5 mL and added to a
stirred hexanes/diethyl ether (60 mL/60 mL) to produce the olive
precipitates, which were collected, washed with diethyl ether and dried
under vacuum to give a mixture of 13a (79 % NMR yield) and 14a (14 %
NMR yield). The ratio of 13a and 14a is about 5.8:1 and the ratio of major
and minor diastereomers of 13a is ca. 1:0.4 from the NMR spectrum. The
mixture was dissolved in CH2Cl2 and was passed through an acidic Al2O3
column eluted with diethyl ether/CH2Cl2. Collecting a yellow band followed
by drying under vacuum gave complex 14a (43 mg, 12% yield). Complex
13a decomposed in the column. Spectroscopic data for 13a: 1H NMR (500
MHz, CDCl3): Mixture of diastereomers (1/0.4): δ 7.54-6.73 (m, Ph), 5.19
3
(s, 5H, Cp(min)), 5.17 (s, 5H, Cp(maj)), 4.92 (t, JHH = 4.5 Hz, 1H, CH(maj)),
Synthesis of 8b. Complex 8b (172 mg, 89% yield) was similarly prepared
by adding dropwise a solution of HBF4 (48%, 0.02 mL, 0.11 mmol) in
MeOH (20 mL) to a stirred solution of 6b (200 mg, 0.22 mmol) in 20 mL of
MeOH at 0 ºC. Spectroscopic data for 8b: 1H NMR (500 MHz, CDCl3): δ
7.35-6.73 (m, 33H, Ph), 5.83 (s, 1H, CH), 5.64 (d, 3JHH = 7.6 Hz, 1H, Ph),
5.03 (s, 5H, Cp), 3.55 (d, 2JHH = 14.5 Hz, 1H, CH2), 3.22 (d, 2JHH = 14.5 Hz,
4.69 (s, 1H, CH(min)), 4.62 (s, 1H, CH(maj)), 4.59 (t, 3JHH = 4.9 Hz, 1H, CH(min)),
3.58 (br, 1H, OH(maj)), 3.24 (m, 1H, CH2(min)), 3.20 (dd, 2JHH = 14.1 Hz, 3JHH
= 4.4 Hz, 1H, CH2(maj)), 3.15 (s, 3H, OCH3(min)), 3.13 (s, 3H, OCH3(maj)), 2.93
(m, 1H, CH2(min)), 2.78 (dd, 2JHH = 14.1 Hz, 3JHH = 4.4 Hz, 1H, CH2(maj)). 13
NMR (125 MHz, CDCl3): 345.65 (t, 2Jcp = 15.1 Hz, Cα(min)), 343.78 (t, 2Jcp
C
=
1H, CH2), 2.97 (d, 2JHH = 17.2 Hz, 1H, CH2), 2.73 (d, 2JHH = 17.2 Hz, 1H,
15.1 Hz, Cα(maj)), 140.80-119.77 (Ph and =C), 120.69 (Cβ(min)), 119.77
(Cβ(maj)), 94.39 (2 Cp), 72.85 (CH(min)), 72.12 (CH(maj)), 67.79 (CH(min)),
65.22 (CH(maj)), 55.56 (2 OCH3), 27.51 (CH2(min)), 26.92 (CH2(maj)). 31P NMR
(161 MHz, CDCl3): δ 42.42, 41.58 (2d, 2Jpp = 27.2 Hz, 2 PPh3(maj)), 41.68,
2
CH2), 1.54 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3): δ 340.74 (t, Jcp
=
15.17 Hz, Cα), 139.24-122.86 (Ph and =C), 131.73 (Cβ), 94.27 (Cp), 81.77
(C(CH3)), 75.72 (CH), 41.03 (CH2), 40.76 (CH2), 26.16 (CH3). 31P NMR
(161 MHz, CDCl3): δ 43.61, 40.45 (2d, 2Jpp = 27.1 Hz, 2 PPh3). Anal. Calcd
for C54H47OP2Ru: C, 74.13; H, 5.41. Found: C, 74.19; H, 5.48. MS: m/z
875.2146 [M]+.
2
41.11 (2d, Jpp = 25.9 Hz, 2 PPh3(min)). Anal. Calcd for C53H47O2P2Ru: C,
72.42; H, 5.39. MS: m/z 879.2095 [M]+. No pure compound was obtained.
Spectroscopic data for 14a: 1H NMR (500 MHz, CDCl3): δ 7.51-6.72 (m,
34H, Ph), 5.50 (d, 3JHH = 6.2 Hz, 1H, CH), 4.93 (s, 5H, Cp), 4.71 (m, 1H,
CH), 4.18 (m, 1H, CH2), 4.01 (t, 3JHH = 9.1 Hz, 1H, CH2), 3.05 (s, 3H, OCH3),
2.93 (td, 3JHH = 9.0 Hz, 3JHH = 9.6 Hz 1H, CH). 13C NMR (125 MHz, CDCl3):
δ 299.57 (t, 2Jcp = 12.5 Hz, Cα), 140.92-125.93 (Ph, =C), 91.24 (Cp), 84.81
(CH), 84.03 (CH2), 82.13 (CH), 54.58 (OCH3), 47.34 (CH). 31P NMR (161
MHz, CDCl3): δ 45.12, 44.53 (2d, 2Jpp = 30.9 Hz, 2 PPh3). Anal. Calcd for
C53H47O2P2Ru: C, 72.42; H, 5.39. Found: C, 72.53; H, 5.48. MS: m/z
879.2095 [M]+.
Synthesis of 9 and 10. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 6c (105
mg, 0.41 mmol), KPF6 (99 mg, 0.54 mmol) and KF (47 mg, 0.81 mmol) in
MeOH (40 mL) was stirred at 50 ºC for 1 day. The solvent was removed
under vacuum and the crude product was extracted with CH2Cl2 (20 mL)
and the mixture was filtered through Celite to remove the insoluble
precipitates. The filtrate was reduced to ca. 5 mL and added to a stirred
hexanes (60 mL) to produce the olive precipitates and yellow filtrate. The
yellow filtrate was collected and dried under vacuum to give complex 9
(138 mg, 55% yield). The precipitates was also collected, washed with
diethyl ether and dried under vacuum to give complex 10 (86 mg, 35%
yield). The ratio of 9 and 10 is about 1.6:1 and the ratio of major and minor
diastereomers of 9 is ca. 1:0.9 from the NMR spectrum. Spectroscopic
data for 9: 1H NMR (400 MHz, d-acetone): Mixture of diastereomers
(1:0.9): δ 7.88-7.05 (m, Ph), 5.42 (s, 1H, CH(min)), 5.36 (s, 1H, CH(maj)), 4.27
(s, 5H, Cp(min)), 4.26 (s, 5H, Cp(maj)), 3.36 (s, 3H, OCH3(min)), 3.35 (s, 3H,
OCH3(maj)), 3.16 (m, 3H, 2 CH2), 3.06 (m, 1H, CH2), 2.97 (m, 2H, 2 CH(epo)),
1.37 (s, 6H, 2 CH3), 1.26 (s, 6H, 2 CH3). 13C NMR (125 MHz, d-acetone):
δ 142.09-126.65 (Ph), 109.57, 109.43 (2 Cβ), 108.02 (t, 2Jcp = 24.3 Hz, Cα),
Synthesis of 13b. Complex 13b (210 mg, 87% yield) was similarly
prepared from [Ru]Cl (200 mg, 0.27 mmol), 11b (94 mg, 0.41 mmol), KPF6
(99 mg, 0.54 mmol) and KF (47 mg, 0.81 mmol) in MeOH at 50 ºC for 1day.
Spectroscopic data for 13b: Mixture of diastereomers (1/0.8): δ 1H NMR
(500 MHz, CDCl3): δ 7.59-6.82 (m, Ph), 5.17 (s, 5H, Cp(maj)), 5.15 (s, 5H,
Cp(min)), 4.75 (s, 1H, CH(maj)), 4.74 (s, 1H, CH(min)), 4.08 (br, 1H, OH(maj)),
3.28 (s, 3H, OCH3(min)), 3.27 (d, 2JHH = 15.3 Hz, 1H, CH2(maj)), 3.02 (s, 3H,
OCH3(maj)), 2.93 (d, 2JHH = 14.2 Hz, 1H, CH2(min)), 2.77 (d, 2JHH = 15.3 Hz,
1H, CH2(maj)), 2.54 (d, 2JHH = 14.2 Hz, 1H, CH2(min)), 1.54 (s, 3H, CH3(min)),
1.50 (s, 3H, CH3(maj)). 13C NMR (125 MHz, CDCl3): δ 346.64 (t, 2Jcp = 15.2
Hz, Cα(maj)), 342.28 (t, 2Jcp = 14.9 Hz, Cα(min)), 142.86-124.84 (Ph and =C),
121.33 (=Cβ(maj)), 119.95 (=Cβ(min)), 94.54 (Cp(min)), 94.49 (Cp(maj)), 73.44
(CH(maj)), 72.90 (CH(min)), 69.28 (C(CH3)(min)), 68.64 (C(CH3)(maj)), 55.95
(OCH3(min)), 55.28 (OCH3(maj)), 34.26 (CH2(maj)), 32.25 (CH2(min)), 29.61
2
107.94 (t, Jcp = 24.3 Hz, Cα), 85.84 (2 Cp), 74.86, 74.34 (2 CH), 64.66,
64.61 (2 CH(epo)), 58.48, 58.45 (2 (CH3)2C (epo)), 55.38, 55.24 (2 OCH3),
32.35, 32.33 (2 CH2), 25.09 (2 CH3), 19.53, 19.43 (2 CH3). 31P NMR (161
MHz, d-acetone): δ 51.22, 50.81 (2d, AB pattern, 2Jpp = 37.1 Hz, 2 PPh3),
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10.1002/asia.201701070
Chemistry - An Asian Journal
FULL PAPER
(CH3(min)), 26.73 (CH3(maj)). 31P NMR (161 MHz, CDCl3): δ 42.42, 41.72 (2d,
2Jpp = 26.9 Hz, 2 PPh3(maj)), 41.50, 41.72 (2d, 2Jpp = 26.3 Hz, 2 PPh3(min)).
Anal. Calcd for C54H49O2P2Ru: C, 72.63; H, 5.53. Found: C, 72.71; H, 5.59.
MS: m/z 893.2251 [M]+.
give complex 20a (98 mg, 40% yield). The precipitates were collected,
washed with diethyl ether and dried under vacuum to give complex 19a
(105 mg, 43% yield). Spectroscopic data for 19a: 1H NMR (500 MHz, C-
3
DCl3): δ 7.76-6.94 (m, 35H, Ph and =CH), 6.15 (d, JHH = 16.8 Hz, 1H,
=CH), 4.77 (s, 5H, Cp), 3.66 (s, 1H, CH(epo)), 3.60 (s, 3H, OCH3), 3.35 (m,
2H, CH2(epo)), 2.56 (m, 2H, CH2), 1.55 (m, 2H, CH2). 13C NMR (125 MHz,
CDCl3): δ 297.87 (t, Jcp = 13.0 Hz, Cα), 141.59-127.15 (Ph), 125.78
Synthesis of 15b. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 11b (93 mg,
0.41 mmol) and NH4PF6 (88 mg, 0.54 mmol) in CH2Cl2 (40 mL) was stirred
at ambient temperature for 1day. The mixture was filtered through Celite
to remove the insoluble precipitates. The filtrate was concentrated to ca. 5
mL and added to a stirred diethyl ether (60 mL) to produce the tangerine
precipitates. The powder was collected, washed with diethyl ether and
2
(=CγH), 123.46 (=CβH), 91.05 (Cp), 69.87 (CH(epo)), 64.05 (OCH3), 49.62
(CH2(epo)), 35.69 (CH2), 28.56 (CH2). 31P NMR (161 MHz, CDCl3): δ 45.69,
45.32 (2d, 2Jpp = 30.2 Hz, 2 PPh3). Anal. Calcd for C55H51O2P2Ru: C, 72.83;
H, 5.67. Found: C, 73.23; H, 5.85. MS: m/z 907.2408 [M]+. Spectroscopic
data for 20a: 1H NMR (400 MHz, C6D6): Mixture of diastereomers (1/1): δ
8.18-6.89 (m, Ph), 5.72 (s, 1H, CH), 5.71 (s, 1H, CH), 4.41 (s, 10H, 2 Cp),
3.60 (s, 3H, OCH3), 3.59 (s, 3H, OCH3), 3.05 (m, 4H, 2 CH2), 2.76 (m, 2H,
2 CH(epo)), 2.37 (m, 2H, 2 CH2(epo)), 2.17 (m, 2H, 2 CH2(epo)), 1.87 (m, 4H,
2 CH2). 13C NMR (100 MHz, C6D6): δ 141.50-126.11 (Ph), 110.07 (2 Cβ),
106.32 (t, 2Jcp = 24.4 Hz, Cα), 106.27 (t, 2Jcp = 24.4 Hz, Cα), 85.58 (2 Cp),
73.77, 73.74 (2 CH), 55.31, 55.27 (2 OCH3), 51.77, 51.76 (2 CH(epo)), 46.77,
46.74 (2 CH2(epo)), 34.75, 34.69 (2 CH2), 29.42, 29.34 (2 CH2). 31P NMR
(161 MHz, C6D6): δ 50.74, 50.26 (2d, 2Jpp = 37.0 Hz, 2 PPh3). Anal. Calcd
for C55H50O2P2Ru: C, 72.91; H, 5.56. Found: C, 72.99; H, 5.49. MS: m/z
907.2330 [M+1]+..
dried under vacuum to give complex 15b (205 mg, 88
% yield).
Spectroscopic data for 15b: 1H NMR (500 MHz, CDCl3): δ 8.01 (s, 1H,
3
=CH), 7.89 (d, JHH = 7.00 Hz, 1H, Ph), 7.41-6.97 (m, 33H, Ph), 4.89 (s,
5H, Cp), 4.25 (d, 2JHH = 8.3 Hz, 1H, CH2), 2.97 (d, 2JHH = 8.3 Hz, 1H, CH2),
0.87 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3): δ 271.57 (t, 2Jcp = 13.6 Hz,
Cα), 148.10 (Cβ), 143.59-124.07 (Ph, =CH), 911.34 (Cp), 83.51 (CH2),
59.30 (CCH3), 22.21 (CH3). 31P NMR (161 MHz, CDCl3): δ 45.73, 44.16
2
(2d, Jpp = 30.5 Hz, 2 PPh3). Anal. Calcd for C53H45OP2Ru: C, 73.94; H,
5.27. Found: C, 74.03; H, 5.34. MS: m/z 861.1989 [M] +.
Synthesis of 14c, 16c and 17c. A mixture of [Ru]Cl (250 mg, 0.34 mmol),
11c (125 mg, 0.51 mmol), KPF6 (125 mg, 0.68 mmol) and KF (59 mg, 1.02
mmol) in MeOH (40 mL) was stirred at 50 ºC for 1day. The solvent was
removed under vacuum and CH2Cl2 (20 mL) was used to extract the crude
product and the mixture was filtered through Celite to remove the insoluble
precipitates. The filtrate was concentrated to ca. 5 mL and added to a
stirred hexanes/diethyl ether (60 mL/60 mL) to produce the olive
precipitates. The precipitates was collected, washed with diethyl ether and
dried under vacuum to give a mixture of 14c (33 % NMR yield), 16c (43 %
NMR yield) and 17c (13 % NMR yield). The ratio of 14c, 16c and 17c is
about 1:1.3:0.4. The mixture was dissolved in CH2Cl2 and was passed
through an acidic Al2O3 column eluted with diethyl ether/CH2Cl2. Collecting
yellow band follow by drying under vacuum to give complex 14c (119 mg,
39 % yield). Spectroscopic data for 14c: 1H NMR (500 MHz, CDCl3): δ
7.87-6.70 (m, Ph), 5.64 (d, 3JHH = 7.0, 1H, CH), 5.07 (m, 1H, CH), 4.93 (s,
5H, Cp), 3.17 (d, 3JHH = 9.4 Hz, 1H, CH), 3.16 (s, 3H, OCH3), 1.14 (s, 3H,
CH3), 0.55 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3): 294.57 (t, 2Jcp = 12.2
Hz, Cα), 140.23-125.52 (Ph), 102.99 (C(CH3)2), 91.31 (Cp), 84.37 (CH),
83.54 (CH), 55.97 (CH), 54.14 (OCH3), 28.64 (CH3), 24.67 (CH3). 31P NMR
(161 MHz, CDCl3): δ 47.02, 42.24 (2d, 2Jpp = 32.3 Hz, 2 PPh3). Anal. Calcd
for C55H51O2P2Ru: C, 72.83; H, 5.67. MS: m/z 907.2408 [M]+.
Spectroscopic data for 16c: 1H NMR (500 MHz, CDCl3): δ 7.86-6.70 (m,
34H, Ph), 48.4 (s, 5H, Cp), 4.19 (s, 2H, CH2), 1.04 (s, 6H, 2 CH3). 13C NMR
(125 MHz, CDCl3): 269.75 (t, 2Jcp = 13.6 Hz, Cα), 171.44 (=C), 158.31 (=C),
149.77-123.04 (Ph), 98.24 (C(CH3)2), 90.09 (Cp), 35.83 (CH2), 24.04 (2
CH3). 31P NMR (161 MHz, CDCl3): δ 45.87 (s, PPh3). Anal. Calcd for
C54H47OP2Ru: C, 74.13; H, 5.41. MS: m/z 875.2146 [M]+. Pure complex
16c was not obtained. Spectroscopic data for 17c: 1H NMR (500 MHz,
CDCl3): δ 6.23 (d, 3JHH = 16.8 Hz, 1H, =CH), 4.91 (s, 5H, Cp), 3.58 (s, 3H,
OCH3), 1.28 (s, 3H, CH3), 0.93 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3):
Synthesis of 19b and 20b. A mixture of complexes 19b (107 mg, 43%
yield) and 20b (97 mg, 39% yield) was similarly prepared from [Ru]Cl (200
mg, 0.27 mmol), 18b (91 mg, 0.351 mmol), KPF6 (99 mg, 0.54 mmol) and
KF (47 mg, 0.81 mmol) in MeOH at 50 ºC for 1 day. Spectroscopic data for
19b: 1H NMR (500 MHz, CDCl3): δ 7.83-6.96 (m, 35H, Ph and =CH), 6.09
3
(d, JHH = 16.8 Hz, 1H, =CH), 4.81 (s, 5H, Cp), 3.59 (s, 3H, OCH3), 2.47
(m, 3H, CH2, CH2(epo)), 2.36 (d, 3JHH = 4.5 Hz, 1H, CH2(epo)), 1.71 (m, 1H,
CH2), 1.51 (m, 1H, CH2), 1.78 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3): δ
2
298.14 (t, Jcp = 13.1 Hz, Cα), 141.13-126.07 (Ph, =CH), 123.15 (=CβH),
91.26 (Cp), 63.77 (OCH3), 56.39 ((CH3)C(epo)), 53.70 (CH2(epo)), 38.24
(CH2), 28.13 (CH2), 20.91 (CH3). 31P NMR (161 MHz, CDCl3): δ 46.10,
45.49 (2d, 2Jpp = 30.0 Hz, 2 PPh3). Anal. Calcd for C56H53O2P2Ru: C, 73.03;
H, 5.80. Found: C, 72.97; H, 5.88. MS: m/z 921.2564 [M]+. Spectroscopic
data for 20b: 1H NMR (400 MHz, C6D6): Mixture of diastereomers (1:1): δ
8.29-6.98 (m, Ph), 5.81 (s, 1H, CH), 5.78 (s, 1H, CH), 4.51 (s, 5H, Cp),
4.50 (s, 5H, Cp), 3.68 (s, 3H, OCH3), 3.66 (s, 3H, OCH3), 3.15 (m, 4H, 2
CH2), 2.54 (m, 2H, 2 CH2(epo)), 2.36 (m, 2H, 2 CH2(epo)), 2.07 (m, 4H, 2 CH2),
1.34 (s, 3H, CH3), 1.33 (s, 3H, CH3). 13C NMR (100 MHz, C6D6): δ 140.44-
125.06 (Ph), 109.10 (2 Cβ), 105.39 (t, 2Jcp= 24.5 Hz, 2 Cα), 84.60 (2 Cp),
72.96, 72.86 (2 CH), 55.48 (2 (CH3)C(epo)), 54.31, 54.24 (2 OCH3), 52.40,
52.30 (2 CH2(epo)), 38.07 (2 CH2), 27.84, 27.73 (2 CH2), 20.34, 20.27 (2
2
CH3). 31P NMR (161 MHz, C6D6): δ 51.49, 51.02 (2d, Jpp = 35.5 Hz, 2
PPh3). Anal. Calcd for C56H52O2P2Ru: C, 73.11; H, 5.70. Found: C, 73.16;
H, 5.64. MS: m/z 921.2486 [M+1]+.
Synthesis of 21a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 18a (86 mg,
0.351 mmol) and NH4PF6 (88 mg, 0.54 mmol) in CH2Cl2 (40 mL) was
stirred at ambient temperature for 1 day. The mixture was filtered through
Celite to remove the insoluble precipitates. The filtrate was concentrated
to ca. 5 mL and added to a stirred diethyl ether (60 mL) to produce the
brown precipitates. The powder was collected, washed with diethyl ether
and dried under vacuum to give complex 21a (175 mg, 74% yield).
Spectroscopic data for 21a: 1H NMR (500 MHz, CDCl3): δ 9.77 (s, 1H, CγH),
7.63-7.06 (m, 34H, Ph), 5.07 (s, 5H, Cp), 3.12 (m, 2H, CH2), 3.04 (m, 1H,
2
297.85 (t, Jcp = 12.5 Hz, Cα), 123.00 (=CH), 90.65 (Cp), 63.36 (OCH3),
62.61 (HC(epo)), 60.43 ((CH3)2C(epo)), 24.12 (CH3), 18.93 (CH3). 31P NMR
(161 MHz, CDCl3): δ 46.43, 44.83 (2d, 2Jpp = 30.3 Hz, 2 PPh3). Anal. Calcd
for C55H51O2P2Ru: C, 72.83; H, 5.67. MS: m/z 907.2408 [M]+.
Synthesis of 19a and 20a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 18a
(86 mg, 0.351 mmol), KPF6 (99 mg, 0.54 mmol) and KF (47 mg, 0.81
mmol) in MeOH (40 mL) was stirred at 50 ºC for 1 day. The solvent was
removed under vacuum and CH2Cl2 (20 mL) was used to extract the crude
product and the mixture was filtered through Celite to remove the insoluble
precipitates. The filtrate was concentrated to ca. 5 mL and added to a
stirred solution of hexanes (60 mL) to produce the olive precipitates and
yellow filtrate. The yellow filtrate was collected and dried under vacuum to
2
2
2
CH(epo)), 2.72 (t, JHH = 4.4 Hz, 1H, CH2(epo)), 2.49 (dd, JHH = 2.7, JHH
=
2.4 Hz, 1H, CH2(epo)), 2.00 (m, 1H, CH2), 1.80 (m, 1H, CH2). 13C NMR (125
MHz, CDCl3): δ 307.54 (t, 2Jcp = 17.7 Hz, Cα), 216.06 (Cβ), 148.81 (CγH),
145.19-128.56 (Ph), 93.74 (Cp), 51.37 (CH(epo)), 47.15 (CH2(epo)), 34.62
(CH2), 29.29 (CH2). 31P NMR (161 MHz, CDCl3): δ 47.29 (s, PPh3). Anal.
Calcd for C54H47OP2Ru: C, 74.13; H, 5.41. Found: C, 74.61; H, 5.65. MS:
m/z 875.2146 [M]+.
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10.1002/asia.201701070
Chemistry - An Asian Journal
FULL PAPER
Synthesis of 21b. Complex 21b (206 mg, 75% yield) was similarly
prepared from [Ru]Cl (200 mg, 0.27 mmol), 18b (91 mg, 0.351 mmol) and
NH4PF6 (88 mg, 0.54 mmol) in CH2Cl2 for 1 day. Spectroscopic data for
21b: 1H NMR (500 MHz, CDCl3): δ 9.71 (s, 1H, CγH), 7.62-7.06 (m, 34H,
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2
Ph), 5.09 (s, 5H, Cp), 3.03 (m, 2H, CH2), 2.71 (d, JHH = 4.6 Hz, 1H,
CH2(epo)), 2.65 (d, 2JHH = 4.6 Hz, 1H, CH2(epo)), 1.94 (m, 2H, CH2), 1.43 (s,
2
3H, CH3). 13C NMR (125 MHz, CDCl3): δ 307.76 (t, Jcp = 17.5 Hz, Cα),
216.28 (Cβ), 148.75 (CγH), 145.79-127.72 (Ph), 93.98 (Cp), 56.74
((CH3)C(epo)), 53.91 (CH2(epo)), 38.86 (CH2), 28.51 (CH2), 21.16 (CH3). 31
P
NMR (161 MHz, CDCl3): δ 47.26 (s, PPh3). Anal. Calcd for C55H49OP2Ru:
C, 74.31; H, 5.56. Found: C, 74.43; H, 5.63. MS: m/z 889.2302 [M]+.
[2]
Synthesis of 23a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 22a (114 mg,
0.351 mmol) , KPF6 (99 mg, 0.54 mmol) and KF (47 mg, 0.81 mmol) in
MeOH (40 mL) was stirred at ambient temperature for 1 day. The mixture
was filtered through Celite to remove the insoluble precipitates. The filtrate
was concentrated to ca. 5 mL and added to a stirred diethyl ether (60 mL)
to produce the brown precipitates. The powder was collected, washed with
diethyl ether and dried under vacuum to give complex 23a (208 mg, 88%
yield). Spectroscopic data for 23a: 1H NMR (500 MHz, CDCl3): δ 7.40-6.63
(m, 34H, Ph), 5.89 (s, 1H, CH), 4.86 (s, 5H, Cp), 4.46 (m, 1H, CH), 3.71
(m, 1H, CH2), 3.49 (dd, 2JHH = 14.2 Hz, 3JHH = 7.0 Hz, 1H, CH2), 3.18 (d,
2JHH = 14.2 Hz, 1H, CH2), 3.00 (m, 1H, CH2), 1.93 (m, 2H, CH2). 13C NMR
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2
(125 MHz, CDCl3): δ 345.24 (t, Jcp = 15.8 Hz, Cα), 143.98-125.93 (Ph),
128.64 (Cβ), 93.54 (Cp), 81.38 (CH), 80.38 (CH), 33.93 (CH2), 33.20 (CH2),
31.32 (CH2). 31P NMR (161 MHz, CDCl3): δ 43.13, 41.52 (2d, 2Jpp = 27.0
Hz, 2 PPh3). Anal. Calcd for C54H47OP2Ru: C, 74.13; H, 5.41. Found: C,
74.21; H, 5.48. MS: m/z 875.2146 [M]+.
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prepared from [Ru]Cl (200 mg, 0.27 mmol), 22b (119 mg, 0.351 mmol),
KPF6 (99 mg, 0.54 mmol) and KF (47 mg, 0.81 mmol) in MeOH (40 mL)
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6.66 (m, 34H, Ph), 5.95 (s, 1H, CH), 4.79 (s, 5H, Cp), 3.71 (m, 1H, CH2),
3.09 (m, 3H, 2 CH2), 2.01 (m, 1H, CH2), 1.74 (m, 1H, CH2), 1.25 (s, 3H,
CH3). 13C NMR (125 MHz, CDCl3): δ 344.79 (t, 2Jcp = 16.0 Hz, Cα), 143.95-
125.97 (Ph, =C), 129.38 (Cβ), 93.38 (Cp), 86.79 (CCH3), 80.09 (CH),
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889.2302 [M]+.
Single-crystal X-ray diffraction analyses: Single crystals of complexes
4, 5b, 8a, 8b, 14a and 15b suitable for X-ray diffraction study were grown
as mentioned above. Single crystals were glued to a glass fiber and
mounted on a SMART CCD diffractometer. The diffraction data were
collected by using a 3-kW sealed-tube Mo Kα radiation (T = 295 K).
Exposure time was 5 s per frame (Siemens area detector absorption).
SADABS37 absorption correction was applied, and decay was negligible.
Data were processed and the structure was solved and refined by the
SHELXTL38 program. Hydrogen atoms were placed geometrically by using
a riding model with thermal parameters set to 1.2 times that for the atoms
to which they are attached and 1.5 times for the methyl hydrogen atoms.
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Acknowledgements ((optional))
We thank the Ministry of Science and Technology, Taiwan, for
financial support.
Keywords: cyclization • epoxide • tandem cyclization • propargyl
acetates • ruthenium • vinylidene
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In MeOH, the cyclizations of propargyl
acetates epoxide 6a and 6b, with [Ru]Cl
give vinylidenes 5a and 5b, respectively,
each with the Cβ incoporated into a
tetrahydro-5H-benzo[7]annulen-6-ol ring.
Further cyclizations of 5a-b give
Yi-Jhen Feng, Yi-Hsin Chen, Shou-Ling
Huang, Yi-Hung Liu and Ying-Chih Lin,*
Page No. – Page No.
Cyclization Reactions of Aryl
Propargyl Acetates with Tethered
Epoxide Induced by Ruthenium
Complex
corresponding 8a-b each with a new 8-
oxabicyclo-[3.2.1]octane ring. For 18,
with longer epoxide chain, the
cyclizations require opening of the
epoxide ring first to afford vicinal
bromohydrin 22, then tandem cyclization
of 22 in MeOH yields 23 with 9-
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Title
Text for Table of Contents
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