Reaction of an oxaruthenacycle with DMAD. Stoichiometric transformations of 2,6-xylenol to allylic phenols and benzopyrans via sp3 C-H bond cleavage reaction

Article abstract of DOI:10.1039/b821179e

Insertion of a dimethyl acetylenedicarboxylate (DMAD) into the Ru-C bond in a cycloruthenated complex Ru[OC₆H₃(2-CH ₂)(6-Me)-κ²O,C](PMe₃)₄ (2) has been achieved to give a seven-membered oxa

Full text of DOI:10.1039/b821179e

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Reaction of an oxaruthenacycle with DMAD. Stoichiometric transformations
of 2,6-xylenol to allylic phenols and benzopyrans via sp3 C–H bond
cleavage reaction†‡
Masafumi Hirano,* Izirwan Bin Izhab, Naoki Kurata, Kaori Koizumi, Nobuyuki Komine and Sanshiro Komiya*
Received 26th November 2008, Accepted 18th February 2009
First published as an Advance Article on the web 14th March 2009
DOI: 10.1039/b821179e
Insertion of a dimethyl acetylenedicarboxylate (DMAD) into the Ru–C bond in a cycloruthenated
2
complex Ru[OC6H3(2-CH2)(6-Me)-k O,C](PMe3)4 (2) has been achieved to give a seven-membered
2
=
oxaruthenacycle Ru[OC6H3{2-CH2C(CO2Me) C(CO2Me)}(6-Me)-k O,C](PMe3)3 (3) in 47% yield.
The molecular structure of 3 by X-ray analysis shows an agostic interaction between the ruthenium and
one of the benzylic methylene protons. Complex 3 shows fluxional behaviour in solution and the
variable temperature NMR studies suggest this fluxionality to be responsible for the turnstile rotation
of three PMe3 ligands and the rotation of the a-methoxycarbonyl group. Heating of a toluene solution
◦
1
3
of 3 at 100 C for 2 h results in the 1,3-H shift reaction in 3 to give a k O,h -C,C¢,C¢¢ allylic complex
1
3
Ru[OC6H3{2-CHC(CO2Me)CH(CO2Me)}(6-Me)-k O,h C,C¢,C¢¢](PMe3)3 (6) (80–90%), whose
molecular structure is revealed by X-ray analysis. Acidolyses of 3 and 6 give 2-[(Z)-2¢,3¢-bis(methoxy-
carbonyl)allyl]-6-methylphenol (7) (88%) and 2-[(Z)-2¢,3¢-bis(methoxycarbonyl)propenyl]-6-
methylphenol (8) (47%), respectively, and iodolyses of 3 and 6 produce 2,3-bis(methoxycarbonyl)-8-
methyl-4H-benzopyran (9) (24%) and 2,3-bis(methoxycarbonyl)-8-methyl-2H-benzopyran (10) (48%),
respectively.
Introduction
The carbon–hydrogen bond cleavage reaction by transition-metal
complexes has attracted current attention because of its potential
for direct functionalization of organic molecules.1 Much effort has
been paid to such chemistries since Chatt and Davidson discovered
the first C–H bond cleavage reaction by a zerovalent ruthenium
complex.2 Among these studies, although several effective catalytic
(1)
the need to sacrifice any extra functional group is very limited,5
such a stoichiometiric study would provide useful information
for the reactivity of the oxaruthenacycle and the formation of
functionalized molecules at the molecular level. Herein we would
like to present a stepwise transformation of an oxaruthenacycle 2
as well as fluxional behaviours of the resulting complexes.
molecular transformations involving a sp2 C–H bond cleavage are
documented, those involving a sp3 C–H bond cleavage are still
limited to date.3 We have reported sp3 C–H bond cleavage reactions
of 2,6-xylenol and the related phenols by low valent ruthenium
complexes. For example, treatment of a zerovalent ruthenium
4
6
complex Ru(h -1,5-COD)(h -1,3,5-COT) (1) with 2,6-xylenol in
the presence of PMe3 produced an oxaruthenacycle complex 2 by
the sp3 C–H bond cleavage reaction [eqn. (1)].4
Results and discussion
As part of an extensive study of this chemistry, we tried to
develop the reaction of 2 with unsaturated compounds. During the
course of this study, we found that DMAD readily inserted into
the Ru–C bond in 2 under ambient conditions. Since chelation-
assisted catalytic insertion of alkynes into the C–H bond without
Reaction of oxaruthenacycle with DMAD and the molecular
strucutre of 3
Treatment of an oxaruthenacycle complex 2 with DMAD in a
mixture of benzene/hexane at room temperature followed by the
work up procedure resulted in the formation of the insertion
product in 47% yield [eqn. (2)].
Department of Applied Chemistry, Graduate School of Engineering, Tokyo
University of A & T, 2–24-16 Nakacho, Koganei, Tokyo, 184–8588, Japan.
E-mail: hrc@cc.tuat.ac.jp, komiya@cc.tuat.ac.jp; Fax: +81-42-388-7044;
Tel: +81-42-388-7044
† Electronic supplementary information (ESI) available: Variable-
temperature 31P{ H} NMR spectra of 3 in acetone-d6. CCDC reference
1
numbers 711077–711078. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/b821179e
(2)
‡ Abbreviations used in this article. COD = cyclooctadiene, C8H12.
COT = cyclooctatriene, C8H10. DMAD = dimethyl acetylenedicarboxy-
∫
=
late, MeO2CC CCO2Me. TCNE = tetracyanoethylene, (NC)2C C(CN)2.
3270 | Dalton Trans., 2009, 3270–3279
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
It is notable that when this reaction took place in the presence of
an excess amount of DMAD in benzene, a complex mixture was
obtained. To obtain a single product, we performed this reaction in
a mixture of benzene/hexane to promote deposition of the mono
insertion product.
Single crystals suitable for the X-ray structure analysis were
obtained by the recrystallisation of 3 from the cold CH2Cl2/hexane
solution. The molecular structure of 3 is given in Fig. 1 and selected
bond distances and angles are listed in Table 1.
2541 cm-1 assignable to the stretching vibration of the agostic
C–H bond in the IR spectrum.6 Agosctic Ru(II)–C bond distances
7,8
˚
are reported in the range 2.395(4)–3.445(4) A. Therefore, the
present Ru(1)–C(8) bond distance is good evidence for the agostic
interaction. By taking into account this interaction and the bond
angles P(1)–Ru(1)–P(2) [96.43(6)◦], P(1)–Ru(1)–P(3) [96.82(7)◦],
P(1)–Ru(1)–O(1) [83.22(12)◦] and P(3)–Ru(1)–O(1) [173.14(13)◦],
complex 3 is best regarded as a distorted octahedral geometry.
˚
The bond distance C(9)–C(10) [1.358(9) A] and the dihedral angle
The molecular structure of 3 shows that a DMAD molecule
is inserted into the Ru–C bond to form a seven-membered
oxaruthenacycle, which seems to be formally a coordinatively un-
C(8)–C(9)–C(10)–Ru(1) [2.4(6)◦] show the double bond character
between C(9)–C(10) and the C(8), C(9), C(10) and Ru(1) atoms
locate on almost the same plane. The dihedral angles C(10)–C(9)–
C(11)–O(2) [177.7(6)◦] and C(9)–C(10)–C(13)–O(4) [-93.0(9)◦]
indicate that while the carbonyl group of C(11)–O(2) locates on
the same plane to the C(9)–C(10) double bond, the carbonyl
˚
saturated complex. However, the distance Ru(1)–C(8) [2.730(5) A]
suggests the presence of an agostic interaction of the methylene
group (vide infra), which is also supported by a weak band at
Fig. 1 Molecular structure of 3 showing atomic numbering schemes. Ellipsoids represent 50% probability. All hydrogen atoms except the methylene
protons at C(8) and an incorporated CH2Cl2 molecule are omitted for clarity.
˚
Table 1 Selected bond distances (A) and angles (deg) of 3
Ru(1)–P(1)
Ru(1)–P(3)
Ru(1)–C(10)
O(3)–C(11)
O(4)–C(13)
C(8)–C(9)
2.3549(18)
Ru(1)–P(2)
Ru(1)–O(1)
O(2)–C(11)
O(3)–C(12)
C(6)–C(8)
C(9)–C(10)
C(10)–C(13)
2.2152(17)
2.128(4)
1.256(9)
1.435(19)
1.509(9)
1.358(9)
1.466(9)
2.2685(19)
2.098(6)
1.264(9)
1.198(8)
1.515(8)
1.477(9)
2.730(5)
C(9)–C(11)
Ru(1)–C(8)
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–O(1)
P(3)–Ru(1)–O(1)
C(6)–C(8)–C(9)
Ru(1)–C(10)–C(9)
C(9)–C(10)–C(13)–O(4)
96.43(6)
83.22(12)
173.14(13)
111.0(5)
105.9(4)
-93.0(9)
P(1)–Ru(1)–P(3)
P(1)–Ru(1)–C(10)
Ru(1)–O(1)–C(1)
C(8)–C(9)–C(10)
C(8)–C(9)–C(10)–Ru(1)
C(10)–C(9)–C(11)–O(2)
96.82(7)
160.85(18)
124.5(4)
118.0(5)
2.4(6)
177.7(6)
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3270–3279 | 3271
©

View Article Online
C(13)–O(4) is vertical. This fact suggests steric repulsion among
the a-methoxycarbonyl group, the equatorial and axial PMe3
ligands, and the b-methoxycarbonylcarbonyl group.
The methyl ester carbon C(12) was disordered and the alterna-
tive carbon C(25), which is not shown in Fig. 1, was bonded to
O(2). The best calculated population of C(12)/C(25) was 50/50.
On the other hand, no disorder was found for C(14). Ru(1)–
16.4.§ The signal at d 43.8 is assigned to the PMe3 trans to the
agostic hydrogen. This is also consistent with the shortest Ru(1)–
P(2) bond in the solid sate (Table 1). These three peaks become
sharper on further cooling to -40 ◦C to show an AMX spin system
2
2
at d -2.0 (t, JP–P = 23 Hz, 1P), 15.6 (dd, JP–P = 47, 23 Hz, 1P)
2
and 44.6 (br.dd, JP–P = 47, 23 Hz, 1P) but further cooling until
-60 ◦C results in the specific broadening of the signal at d 45.0
(half-width = 179 Hz), which is finally divided into two signals at
d 45.3 and 46.5 in a 7/3 ratio at -80 ◦C.
˚
P(1) [2.3549(18) A] which is remarkably longer than Ru(1)–P(2)
˚
˚
[2.2152(17) A] or Ru(1)–P(3) [2.2685(19) A], suggesting a strong
trans influence of C(10).
In the 1H NMR spectrum of 3 in acetone-d6 at 20 ◦C, a broad
signal assignable to the three PMe3 is observed around d 1.4–1.6
(27H) (Fig. 2). The most significant feature of 3 in the 1H NMR
spectrum is a doublet at d -1.40 (2JH–H = 15.6, 1H) and a doublet
of quartets at d 3.26 (2JH–H = 15.6, 5JH - P = 1.5, 1H). The 1H–1H
COSY suggests these signals being tied up with each other and
they are assigned as the geminal methylene protons.
A similar treatment of 2 with phenylacetylene quantitatively
released 2,6-xylenol,4b and neither reaction of diphenylacetylene
nor methyl propiolate with 2 did not proceed under the same
conditions.
Fluxional behaviour of 3 in a solution
This large splitting and the high-field shift of one of these
protons are due to the agostic interaction and the signal at d -1.40
is assignable to the agostic proton. It is notable that while the exo
(non-agostic) methylene proton has coupled to three equivalent
phosphorus atoms, the endo methylene proton apparently does
not have spin coupling to any phosphorus atoms despite the
◦
Complex 3 shows a fluxional behaviour in solution. At 20 C in
acetone-d6, no apparent signals assignable to 3 are observed in
the 31P{ H} NMR spectrum. On cooling the solution to 0 ◦C,
1
broad peaks are observed at d -3.0 (br, 1P), 14.8 (br, 1P) and
43.8 (br, 1P). The highest-field resonance at d -3.0 is assigned to
the PMe3 trans to C having a very strong trans influence,9 that is
also consistent with the longest Ru(1)–P(1) bond in the solid state
(Table 1). The signal at d 14.8 is assignable to the PMe3 ligands
trans to O. It is notable that the reported PMe3 resonances trans to
OAr in octahedral cis-RuH(OAr)(PMe3)4 are in the range d 15.2–
§ The reported PMe3 resonances for trans to OAr in RuH(OAr)(PMe3)4 in
1
the 31P{ H} NMR are as follows: d 15.2 (Ar = C6H4OMe-4, in C6D6) [ref.
23], d 15.2 (Ar = C6H4Me-2, in C6D6) [ref. 4b], d 15.3 (Ar = C6H4CHMe2–2,
in C6D6) [ref. 4b], d 15.3 (Ar = C6H4Me-4, in CD2Cl2) [ref. 24] and d 16.4
(Ar = Ph, in CD2Cl2) [ref. 24].
Fig. 2 Variable-temperature 1H NMR spectra of 3 in acetone-d6 (300 MHz). X indicates an impurity.
3272 | Dalton Trans., 2009, 3270–3279 This journal is The Royal Society of Chemistry 2009
©

View Article Online
agostic interaction. Therefore, the H–P spin coupling for the exo
methylene proton is considered to be transferred through the 5JH–P
bonds. On the other hand, the endo methylene proton does not
have any apparent H–P couplings probably because of the small
averaged three 2JH–P spin couplings through agostic interaction at
this temperature. On cooling the solution at -50 ◦C, these geminal
methylene signals changed to a doublet of doublets of triplets at
2
2
d -1.40 (2JH - H = 15.7, JH - P = 8.1, JH - P = 3.9 Hz, 1H) and
a doublet of doublets at d 3.24 (2JH - H = 15.7, JH - P = 6.0 Hz,
4
1H), without changing the chemical shift. Further cooling of the
solution results in the significant broadening of these methylene
signals. For the methoxy resonances in the ester groups sharp two
singlets are observed at d 3.42 (3H, half width = 0.96 Hz) and 3.57
(3H, half width = 0.96 Hz) at 20 ◦C. On cooling the solution, the
◦
latter signal causes broadening (half-width = 8.4 Hz) at -80 C,
while the former remains relatively sharp (half-width = 2.5 Hz).
Unfortunately, we do not know which methoxycarbonyl group is
assigned to this broadening signal.
It is no◦table that in the 13C NMR spectrum of 3 in chloroform-
1
d1 at 18 C, a doublet of doublets at d 26.9 (dd, JC–H = 126,
98 Hz) is assignable to the ortho-methylene carbon. The small 1JC–H
value (1JC–H = 98 Hz), being a typical diminished 1JC–H value (75–
100 Hz),10 suggests the presence of agostic interaction. In addition,
this fact supports the presence of agostic interaction even around
room temperature.
These fluxional behaviours can be explained as follows (Fig. 3).
Complex 3 has an agostic interaction at room temperature and the
fluxionality is due to the rapid site exchanging of the three PMe3
ligands. Since the JH - P spin coupling between one of the methylene
protons and three equivalent phosphorus atoms remains intact
throughout this temperature range at almost the same chemical
shift, the site exchange is operated in the octahedral geometry
by a turnstile mechanism.11 Around -40 ◦C, the site exchange of
the PMe3 ligands almost stopped. However, as described above,
further fluxional behaviour should be involved in this complex. At
-80 ◦C, the PMe3 ligand trans to the agostic ligand is separated into
Fig. 3 Possible behaviours of 3. At room temperature, PMe3 and
a-methoxycarbonyl groups rotate and the rotation of PMe3 was frozen
around -40 ◦C. Around -80 ◦C, the rotation of the a-methoxycar-
bonyl group slows down. In a crystal, X-ray analysis shows the a-methoxy-
carbonyl group locates in the vertical to the equatorial plane.
1
two broad resonances in the 31P{ H} NMR and one of the methoxy
beca◦use only the PMe3 cis to C shows significant change below
-40 C. These rotamers would be stabilized by conjugation with
resonances also shows significant broadening at the same time. The
fluxionality observed below -40 ◦C is independent from the agostic
interaction because the exo and endo methylene protons basically
do not change their chemical shifts in this temperature range (20
to -80 ◦C). The most probable reason for this fluxionality is a
slow down of the rotation of one of the methoxycarbonyl groups.
As described above, we have observed two orientations of the
b–methoxycarbonyl group by X-ray analysis. One may relate this
finding with the fluxionality. However, we believe this is a less likely
scenario because the orientation of the b–methoxycarbonyl group
would not perturb the PMe3 cis to C so much.¶ The more pertinent
explanation for this fluxionality is therefore attributable to the slow
down in rotation of the a–methoxycarbonyl group as depicted
in Fig. 3. The a–methoxycarbonyl resonance and the PMe3
resonance cis to C are separated into two peaks at low temperature,
although the frozen NMR spectum could not be obtained under
experimental conditions. Probably, the a–methoxycarbonyl group
has two stable orientations in the equatorial plane around -80 ◦C
=
the neighbouring C C bond.
1
The 1H and 31P{ H} NMR spectra would be affected by
the proximal/distal methyl ester group toward the PMe3 ligand
cis to C. However, X-ray analysis of 3 showed that the a-
=
methoxycarbonyl group takes from the C C plane despite loss of
the conjugated system in the solid state (Fig. 1). This may be caused
by the packing of 3 in a unit cell because of the steric repulsion by
the equatorial PMe3 and the b-methoxycarbonyl groups.
The fluxional complex 3 was instantly converted to a stable
complex by exposure to an atmosphere of CO. By exposure of an
acetone solution of 3 to CO (0.1 MPa) at room temperature, the
orange colour was immediately bleached. After evaporation of
the solution followed by washing with cold pentane, a mixture
of saturated carbonyl complexes was obtained as a colourless
powder of 4 (53%) and 5 (17%) [eqn. (3)]. Unfortunately the
1
31P{ H} NMR spectrum of these complexes did not give useful
structural information because of broadening. The 1H NMR
spectrum suggests the presence of two independent species. Since
both complexes have a virtual triplet assignable to the PMe3 ligand,
these compounds have a couple of mutually trans PMe3 ligands,
respectively. The presence of the third PMe3 is observed only for the
¶ Since the anisotropic displacement parameter Uani for P(1) [0.0301(4)] is
comparable to P(2) [0.0323(4)] and P(3) [0.0300(4)], the 50/50 disorder of
the b-methoxycarbonyl group does not affect the P(1) atom.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3270–3279 | 3273
©

View Article Online
major species in the 1H NMR spectrum in relatively high magnetic
field at d 1.07 (d), that is characteristic PMe3 trans to the carbon
having a strong trans influence. Therefore, overall structures for 4
and 5 are assigned as shown in eqn. (3). Consistently, the methylene
protons appeared at d 3.81 for 4 and d 3.71 for 5 as a singlet,
respectively, although they are observed as slightly broad signals,
probably due to flipping of the seven-membered oxaruthenacycle
ring. This fact also suggests the apparent Cs symmetry of 4 and 5
in solution. The IR spectrum of the mixture of 4 and 5 shows three
bands assignable to the metal carbonyls at 2052 (s, nCO), 1962 (s,
nCO) and 1922 (vs, nCO) cm-1 in KBr, suggesting the presence of
three different metal carbonyl groups.
(4)
Complex 6 shows an AXY pattern in the 31P{ H} NMR
1
suggesting the presence of three inequivalent phosphorus atoms.
The 1H NMR shows a terminal allylic proton at d 5.41 (s, 1H) and
an ortho methine proton at d 2.74 (d, 1H). However, the most direct
evidence for the molecular structure of 6 was obtained by X-ray
analysis (Fig. 4) and the selected molecular distances and angles
are listed in Table 2. The comparable bond distances Ru(1)–C(8),
˚
Ru(1)–C(9) and Ru(1)–C(10) (2.202–2.257 A), the almost equal
˚
˚
distances C(8)–C(9) [1.413(8) A] and C(9)–C(10) [1.429(8) A],
˚
Table 2 Selected bond distances (A) and angles (deg) of 6
(3)
Ru(1)–P(1)
Ru(1)–P(3)
Ru(1)–C(8)
Ru(1)–C(10)
C(9)–C(10)
2.3344(16)
2.3026(16)
2.252(5)
2.257(5)
1.429(8)
Ru(1)–P(2)
Ru(1)–O(1)
Ru(1)–C(9)
C(8)–C(9)
2.3277(16)
2.144(4)
2.202(6)
1.413(8)
1,3-Hydrogen shift to give an g3–allylic complex
Heating of the fluxional complex 3 due to agostic interaction
caused a unique 1,3-H shift reaction. Namely, the NMR study
for heating of a toluene solution of 3 at 100 ◦C for 2 h produced
an h -allylic complex 6 in 80% yield [eqn. (4)]. Complex 6 was also
prepared directly from 2 without isolation of 3 in 90% isolated
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–O(1)
P(2)–Ru(1)–C(9)
C(6)–C(8)–C(9)
C(9)–C(10)–C(13)
100.55(5)
83.22(13)
130.66(17)
124.3(5)
P(1)–Ru(1)–P(3)
P(1)–Ru(1)–C(9)
P(3)–Ru(1)–O(1)
C(8)–C(9)–C(10)
91.58(5)
128.20(17)
172.96(13)
122.0(5)
3
121.2(5)
yield.
Fig. 4 Molecular structure of 6 with numbering schemes. All hydrogen atoms except allylic protons and an incorporated CH2Cl2 molecule are omitted
for clarity. Ellipsoids represent 50% probability.
3274 | Dalton Trans., 2009, 3270–3279
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
and bond angles C(6)–C(8)–C(9) [124.3(5)◦], C(8)–C(9)–C(10)
[122.0(5)◦] and C(9)–C(10)–C(13) [121.2(5)◦] indicate formation of
an h -allylic fragment. The stereochemistry of the allyic moiety is
an sp2 C–H bond cleavage reaction of 2-phenylphenol followed
by an insertion alkyl acrylates/b–hydrogen elimination followed
by Michael type nucleophilic cyclisation,12 no cyclisation occurred
from 7 or 8 in the present system under these conditions.
3
anti to the aryl fragment and syn to the terminal methoxycarbonyl
group. The molecular structure of 6 is best regarded as a trigonal
Reductive elimination from a metallacycle-like present system
seems to be a promising way to produce heterocycles. However,
divalent ruthenium requires high energy for reductive elimination13
and reductive elimination between carbon and electronegative
atoms is difficult.14 Despite these facts, it is interesting to
introduce a rare example of Pfeffer and his co-workers, where
1
3
bipyramidal complex with k O and h -allylic bondings. Since a
benzylic methylene proton in complex 3 has an agostic interaction
with Ru, one of the most reasonable explanations for the formation
mechanism of 6 is the C–H bond cleavage reaction of the agostic
proton in 3 followed by the migration of the resulting hydride to
the terminal carbon to give 6.
6
2
a Ru(II) complex RuCl(h -C6H6)(NMe2CH2C6H4-k N,C) reacted
with internal alkynes to yield an isoquinolinium derivative and
Ru(0) at room temperature,15 where spontaneous C–N reductive
elimination was expected to be involved. Ryabov and his co-
workers demonstrated that Pfeffer’s reaction involved a C–N
bond reductive elimination step by kinetic studies.16 Therefore,
it is worth studying the production of benzopyran derivatives
from 3 and 6. However, they were thermally stable complexes
and treatments of them with TCNE or atmospheric oxygen
led to complex decomposition. When iodine was employed as
an oxidant, 2,3-bis(methoxycarbonyl)-8-methyl-4H-benzopyran
(9) and 2,3-bis(methoxycarbonyl)-8-methyl-2H-benzopyran (10)
were obtained from 3 and 6 in 24% and 48% yields, respectively.
In relation to the iodolysis of 6, we have briefly reported for-
Acidolysis and iodolysis of complexes 3 and 6
Acidolysis of 3 by dry HCl gas in acetone produced 2-[(Z)-
2¢,3¢-bis(methoxycarbonyl)allyl]-6-methylphenol (7) in 88% yield.
Compound 7 was characterised by 1H NMR, GLC and GC-MS.
Similar treatment of 3 with DCl/D2O resulted in the deuteration
of the methine proton at the 3¢-proton (Scheme 1). On the
other hand, acidolysis of 6 by dry HCl gas gave 2-[(Z)-2¢,3¢-
bis(methoxycarbonyl)propenyl]-6-methylphenol (8) in 47% yield
and treatment of 6 with DCl/D2O led to the deuteration of the
terminal methylene group at the 3¢-position.ꢀ Although Miura and
his coworkers reported formation of dibenzopyran derivatives by
3
mation of a similar h -allylic complex Ru[OC6H4(2-CHCHCH2)-
1
3
k O,h -C,C¢,C¢¢](PEt3)3 (11a) by the reaction of 1 with 2-
allylphenol in the presence of PEt3.4a It is interesting to compare
the iodolysis of 6 to that of 11a because they have a comparable
1
3
k ,h -structure. Reaction of 1 with 2-allyl-6-methylphenol and
2-allyl-6-methoxyphenol in the presence of PEt3 produced cor-
responding allylic complexes Ru[OC6H4(2-CHCHCH2)(6-Me)-
1
3
k O,h -C,C¢,C¢¢](PEt3)3 (11b) and Ru[OC6H4(2-CHCHCH2)(6-
1
3
OMe)-k O,h -C,C¢,C¢¢](PEt3)3 (11c) in 38% and 42% yields,
respectively. Iodolysis of 11a–c at room temperature also led
to the formation of 2H-benzopyrans in moderate yields (72–
74%) (Scheme 2). These benzopyrans were characterised by the
authentic samples prepared by literature methods.17,18
Scheme 2
Scheme 1
These reactions suggest that iodine is an effective oxidant to
promote reductive elimination between the terminal allylic carbon
and aryloxo oxygen and the C–O reductive elimination is a
common nature of these k O,h -allylic complexes. Although the
detailed mechanism for the reductive elimination is so far unclear,
ꢀ Selective incorporation of deuterium at the terminal methine and
methylene position suggests strong linkage between these carbons and
the Ru centre. However, the reason why their deuterium contents have
diminished is not clear at present.
1
3
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3270–3279 | 3275
©

View Article Online
intramolecular nucleophilic attack of the aryloxo oxgen to the
solution was stirred at room temperature for 5 h to give an orange
precipitate. The resulting precipitate was washed with hexane and
was recrystallised from cold CH2Cl2 to give an orange agos-
tic complex Ru[OC6H3{2-CH2C(CO2Me)=C(CO2Me)}(6-Me)-
3
h -allylic moiety is a possible pathway.14
Conclusions
2
k O,C](PMe3)3 (3) in 47% yield (70.3 mg, 0.119 mmol). 1H NMR
◦
2
In conclusion, the present work provides a stoichiometric trans-
formation reaction of 2,6-xylenol via a sp3 C–H bond cleavage
reaction of the ortho methyl group, where each step can be
unequivocally characterised in detail by NMR and X-ray analyses.
An insertion reaction of a ruthenacycle complex 3 with DMAD
followed by the 1,3-H shift reaction led to the formation of an
(300 MHz, acetone-d6, 20 C): d -1.40 (d, JH–H = 15.6 Hz, 1H,
agostic ortho-CH2), 1.4–1.5 (br, 27H, PMe3), 2.1 (overlapped,
2
5
ortho-Me), 3.26 (dq, JH–H = 15.6, JH - P = 1.5 Hz, 1H, ortho-
CH2), 3.42 (s, 3H, b-CO2Me), 3.57 (s, 3H, a-CO2Me), 5.96 (t,
3JH - H = 7.2 Hz, 1H, para-C6H3), 6.67 (d, JH–H = 7.2 Hz, 2H,
3
meta-C6H3). H NMR (300 MHz, acetone-d6, -50 ◦C): d -1.41
1
3
(ddt, 2JH–H = 15.9, 5JH–P = 7.8, 5JH–P = 3.9 Hz, 1H, agostic ortho-
CH2), 2.00 (br s, 9H, PMe3), 2.02–2.06 (overlapped with signals
due to acetone, PMe3), 2.07 (s, ortho-Me), 3.26 (dd, 2JH–H = 15.9,
5JH–P = 6.3 Hz, 1H, ortho-CH2), 3.38 (s, 3H, b-CO2Me), 3.53 (s,
3H, a-CO2Me), 5.95 (t, 3JH–H = 7.2 Hz, 1H, para-C6H3), 6.63 (d,
h -allylic complex 6. Although a strong oxidant such as iodine
is required for the reaction, this process gives 2H-benzopyran
derivatives suggesting reductive elimination between the terminal
allylic carbon and oxygen. Such C–O bond formation by reductive
elimination is generally rare, although reductive elimination be-
tween acyl and alkoxo/aryloxo groups is well documented.4a These
stoichiometric reactions represent production of benzopyran
derivatives from 2,6-xylenol or 2-allylphenol via an sp3 C–H bond
cleavage reaction.
3JH - H = 7.2 Hz, 2H, meta-C6H3). 13C{ H} NMR (100.5 MHz,
1
chloroform-d1, 18 ◦C): d 17.4 (s, ortho-CH3),18–27 (br.m, PCH3),
26.9 (s, ortho-CH2), 50.9 (s, CO2CH3), 51.1 (s, CO2CH3), 109.9
(s, aromatic), 120.2 (s, aromatic), 125.5 (s, aromatic), 127.4 (s,
aromatic), 127.9 (s, aromatic), 129.2 (s, aromatic), 162.7 (s, C=O
or C=C), 169.9 (s, C=O or C=C), 178 (br, C=C), 179.1 (s, C=O
or C=C). 13C NMR (100.5 MHz, chloroform-d1, 18 ◦C): d 17.4 (q,
Experimental
1JC–H = 130 Hz, ortho-CH3), 15–27 (m, PCH3), 26.9 (dd, 2JC–H
=
General procedures
1
126, 98 Hz, ortho-CH2),50.9 (q, JC–H = 145 Hz, CO2CH3), 51.1
(q, 1JC–H = 145 Hz, CO2CH3), 110.0 (d, 1JC–H = 159 Hz, aromatic),
120.3 (s, aromatic), 125.5 (s, aromatic), 127.4 (d, 1JC–H = 155 Hz,
aromatic), 127.9 (s, aromatic), 129.2 (d, 1JC–H = 160 Hz, aromatic),
All manipulations were carried out under dry nitrogen using
standard Schlenk and vacuum line techniques. Benzene, toluene,
hexane and Et2O were dried over anhydrous calcium chloride and
then distilled from sodium wire under nitrogen with benzophe-
none ketyl as an indicator. Acetone and dichloromethane were
dried over anhydrous Drierite and distilled over Drierite under
nitrogen. Complex 1 was prepared according to the reported
method.4a,b DMAD was used as received. Compound 12a was
prepared according to the literature method by the reduction of
4-chromanone with LiAlH4 followed by dehydration.17 Com-
pounds 12b and 12c were prepared according to the literature
method by the Claisen rearrangement reactions of 2-methylphenyl
propargyl ether derived from ortho-cresol and 2-methoxyphenyl
proargyl ether derived from 2-methoxyphenol.18 PMe3 and PEt3
were prepared by the reaction of P(OPh)3 with MeMgI or
EtMgBr.19 Aluminium oxide was purchased from Merck (90 active
neutral, active stage I, 70–230 mesh) and was used as received.
Deuterated solvents for use in NMR experiments were pur-
chased from Kanto Chemical and dried with sodium wire for
benzene-d6 and Drierite for acetone-d6 and were directly vacuum
transferred into an NMR tube. NMR spectra were recorded
on a JEOL LA-300 or ECX-400 spectrometers (300.4 MHz or
399.8 MHz for 1H) with chemical shifts reported in ppm downfield
162.6 (s), 169.9◦(s), 178 (br), 179.1 (s). 31P{ H} NMR (121 MHz,
1
acetone-d6, 20 C): no apparent peak. 31P{ H} NMR (121 MHz,
1
acetone-d6, -50 ◦C): d -1.6 (t, 2JP–P = 23 Hz, 1P), 15.9 (dd, 2JP–P
=
47, 23 Hz, 1P) and 45.0 (br, 1P). IR (KBr, cm-1): 3044 (w), 2969
(w), 2905 (m), 2541 (w), 1681 (vs), 1575 (s), 1457 (s), 1424 (s), 1299
(s), 1218 (s), 1123 (s), 969 (s), 942 (vs), 856 (m), 740 (s), 721 (m),
672 (m). Anal. Calcd for C23H41O5P3Ru: C, 46.70; H, 6.99. Found:
C, 46.74; H, 6.81.
Reaction of 3 with CO. Complex 3 (27.5 mg, 0.0464 mmol)
was placed in a 25 ml Schlenk tube into which acetone (2 ml) was
added to give an orange solution. Carbon monoxide (0.1 Mpa)
was exposed to the solution at room temperature and the
colour was instantly bleached within 1–2 min. The solution
was evaporated to give a white solid which was washed with
cold pentane to give colourless solid (17.8 mg). The NMR
analyses of this product suggests a mixture of mer-Ru[OC6H3{2-
2
CH2C(CO2Me)=C(CO2Me)}(6-Me)-k O,C](PMe3)3(CO) (4) and
cis,trans,cis-Ru[OC6H3{2-CH2C(CO2Me)=C(CO2Me)}(6-Me)-
2
k O,C](PMe3)2(CO)2 (5) in 53% and 17% yields, respectively. 4: 1H
1
from TMS for H and from 85% H3PO4 in D2O for 31P NMR.
2
NMR (300 MHz, benzene-d6, r.t.): d 1.07 (d, JH–P = 7 Hz, 9H,
IR spectra were recorded on a JASCO FT/IR-410 spectrometer
using KBr disks. Elemental analyses were carried out using a
Perkin-Elmer 2400 series II CHN analyzer. GC-MS spectra were
performed on a Shimadzu QP2000 equipped with a capillary
column (TC-1, 0.25 mm ¥ 30 m).
4
PMe3), 1.14 (vt, 2JH–P = JH–P = 3.9 Hz, 18H, mutually trans PMe3),
2.25 (s, 3H, 6-Me), 3.57 (s, 3H, CO2Me), 3.75 (s, 3H, CO2Me), 3.81
3
(br.s, 2H, 2-CH2), 6.78 (t, JH–H = 7 Hz, 1H, aromatic), 7.1–7.2
1
(overlapped with signal due to benzene). 31P{ H} NMR (121 MHz,
benzene-d6, r.t.): d -16.3 (t, 2J = 28 Hz, 1P, PMe3), -10.5 (br, 2P,
Reaction of
2
with DMAD. Ru[OC6H3(2-CH2)(6-Me)-
PMe3). 5: 1H NMR (300 MHz, benzene-d6, r.t.): d 1.09 (vt, 2JH–P
=
2
k O,C](PMe3)4 (2) (133.1 mg, 0.2535 mmol) was placed in a 25 ml
Schlenk tube, into which hexane (4 ml) and benzene (2 ml) were
added to give a yellow solution. DMAD (52.8 ml, 0.431 mmol)
was added and the solution turned red instantly. The resulting
4JH–P = 3.9 Hz, 18H, mutually trans PMe3), 2.41 (s, 3H, 6-Me),
3.50 (s, 3H, CO2Me), 3.66 (s, 3H, CO2Me), 3.77 (br.s, 2H, 2-CH2),
3
7.1–7.2 (overlapped with signal due to benzene), 7.4 (d, JH–H
=
1
7 Hz, 1H, aromatic). 31P{ H} NMR (121 MHz, benzene-d6, r.t.):
3276 | Dalton Trans., 2009, 3270–3279
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
d -9.0 (s, 2P, PMe3). IR spectrum of a mixture of 4 and 5 in
KBr (cm-1): 2982 (m), 2944 (m), 2914 (m), 2052 (s, nCO), 1962 (s,
nCO), 1922 (vs, nCO), 1703 (vs, nC O), 1587 (m), 1558 (m), 1421
(s), 1286 (s), 1196 8 s), 1167 (s), 1101 (s), 1085 (s), 1020 (m), 949
(vs), 851 (s), 755 (s), 671 (m).
Acidolysis of 6. Complex 6 (67.4 mg, 0.114 mmol) was placed
in a 25 ml Schlenk tube into which acetone (3 ml) was added.
Dry HCl gas was exposed to the solution using a manometer
(0.228 mmol, 2 equiv) and the solution was instantly bleached with
deposition of precipitate. The liquid phase was separated from the
precipitate and volatile matter was removed under vacuum to give
2-[(Z)-2¢,3¢-bis(methoxycarbonyl)propenyl]-6-methylphenol (8) in
=
Preparation of 6.
1
(Method A). Complex 2 (79.9 mg, 0.1349 mmol) was placed
in a 25 ml Schlenk tube into which hexane (5 ml) and benzene
(3 ml) were added. DMAD (55.0 ml, 0.449 mmol) was added
to the solution and the reaction mixture was stirred at room
temperature for 5 h. The resulting precipitate was collected and
washed with hexane. Then, toluene (3 ml) was added and the
solution was heated at 100 ◦C for 10 h. After the reaction,
the product was separated through column chromatography
using neutral alumina and the yellow band was collected. The
resulting yellow fraction was evaporated to give analytically pure
yellow solid of Ru[OC6H3{2-CHC(CO2Me)CH(CO2Me)}(6-Me)-
47% yield. H NMR (300 MHz, benzene-d6, r.t.): d 2.13 (s, 3H,
6-Me), 3.25 (s, 3H, CO2Me), 3.34 (s, 2H, CH2CO2Me), 3.36 (s,
3H, CO2Me), 6.18 (br, 1H, OH), 6.70 (t, 3JH–H = 7 Hz, 1H, 4-CH),
6.90 (d, 3JH–H = 7 Hz, 1H, 3- or 5-CH), 6.93 (d, 3JH–H = 7 Hz, 1H,
5- or 3-CH), 8.00 (s, 1H, CH=C). GC-MS (EI): m/z = 264 (M+).
Acidolysis of 6 (7.0 mg, 0.012 mmol) with 3 drops of DCl/D2O
(37 wt%) in benzene-d6 caused incorporation of D atoms at 80%
at the terminal methine in 8 and no incorporation was observed
at the benzylic position.
Iodolysis of 3. Complex 3 (17.0 mg, 0.0287 mmol) was placed
in a 25 ml Schlenk tube into which acetone (3 ml) was added.
Addition of iodine (12.4 mg, 0.0488 mmol) to the solution caused
an immediate colour change to dark brown. The solution was
stirred at room temperature for 12 h during which deposition
of precipitate was observed. After removal of the precipitate, all
volatile matter was removed under reduced pressure to give 2,3-
bis(methoxycarbonyl)-8-methyl-4H-benzopyran (9) in 24% yield.
1H NMR (300 MHz, benzene-d6, r.t.): d 2.06 (s, 3H, 8-Me), 3.09
(s, 3H, CO2Me), 3.32 (s, 3H, CO2Me), 3.89 (s, 2H, 4-CH2), 6.70
1
3
k O,h -C,C¢,C¢¢](PMe3)3 (6) in 90% yield (71.8 mg, 0.121 mmol).
(Method B). Complex 3 (1.4 mg, 0.0024 mmol) was dis◦solved
in toluene-d8 (0.6 ml) and the solution was heated at 100 C for
2 h. The NMR spectrum showed formation of 6 in 80% yield.
1H NMR (300 MHz, benzene-d6, r.t.): d 1.02 (d, 2JH–P = 8.4 Hz,
2
2
9H, PMe3), 1.15 (d, JH–P = 8.4 Hz, 9H, PMe3), 1.28 (d, JH–P
=
8.4 Hz, 9H, PMe3), 2.26 (s, 3H, ortho-Me), 2.74 (d, 3JH–P = 3.3 Hz,
1H, syn-CHAr), 3.43 (s, 3H, CO2Me), 3.59 (s, 3H, CO2Me), 5.41
(s, 1H, anti-CHCO2Me), 6.54 (t, 3JH–H = 7.4 Hz, 1H, para-C6H3),
7.04 (d, 3JH–H = 6.9 Hz, 1H, meta-C6H3), 7.14 (overlapped, meta-
3
3
(t, JH–H = 7 Hz, 1H, 6-CH), 6.88 (d, JH–H = 7 Hz, 1H, 5- or 7-
CH), 7.22 (d, 3JH–H = 7 Hz, 1H, 7- or 5-CH). GC-MS (EI): m/z =
262 (M+).
C6H3). 13C{ H} NMR (74.5 MHz, benzene-d6, r.t.): d 17.15 (s, 6-
1
Me), 19.4 (dd, 1JC–P = 22, 3JC–P = 8 Hz, PMe3), 20.78 (dd, 1JC–P
=
Preparation of 11a. Preparation of 11a was briefly reported in
a previous communication.4a Complex 1 (383 mg, 1.21 mmol) was
placed in a 25 ml Schlenk tube into which benzene (4 ml), PEt3
(540 ml, 3.65 mmol) and 2-allylphenol (160 ml, 1.22 mmol) were
added in this order. The solution was stirred at 50 ◦C for 12 h,
during which the yellow solution turned orange. After removal of
volatile matter, the resulting solid was dried under vacuum. The
solid was extracted with Et2O and purified by a chromatography
with neutral alumina. The yellow fraction was collected and the
solution was concentrated. Setting aside the solution at -20 ◦C
for a night gave yellow blocks of 11a in 39% yield (227.4 mg). 1H
21, 3JC–P = 6 Hz, PMe3), 22.7 (d, 1JC–P = 28 Hz, PMe3), 50.18 (s,
2
OMe), 52.50 (s, OMe), 52.77 (d, JC–P = 18 Hz, CH), 80.17 (d,
2JC–P = 17 Hz, CH), 110.58 (s, CCO2Me), 112.42 (s, C6H3), 126.5
(d, 4JC–P = 3 Hz, 3-C6H3), 127.2 (s, 2- or 6-C6H3), 129.02 (s, 6- or
2-C6H3), 129.78 (s, 5-C6H3), 168.9 (d, 3JC–P = 8 Hz, 1-C6H3), 172.4
(d, 3JC–P = 5 Hz, CO2Me), 174.2 (s, CO2Me). 31P{ H} (121 MHz,
1
benzene-d6, r.t.): d 3.03 (dd, 2JP–P = 38, 26 Hz, 1P, PMe3), 3.18 (dd,
2JP–P = 38, 26 Hz, 1P, PMe3), 7.93 (t, JP–P = 38 Hz, 1P, PMe3).
2
Anal. Calcd for C23H41O5P3Ru: C, 46.70; H, 6.99. C, 46.87; H,
6.68.
Acidolysis of 3. Complex 3 (4.8 mg, 0.0081 mmol) was placed
in a 25 ml Schlenk tube into which acetone (3 ml) was added.
Dry HCl gas was exposed to the solution using a manometer
(0.139 mmol, 17.1 equiv) and the solution colour instantly turned
pale yellow with deposition of precipitate. The liquid phase was
separated form the precipitate and volatile matter was removed
under vacuum to give 2-[(Z)-2¢,3¢-bis(methoxycarbonyl)allyl]-6-
NMR (300 MHz, benzene-d6, r.t.): d 0.72 (dt, 3JH–P = 12.2, 3JH–H
=
7.6 Hz, 9H, PCH2CH3), 1.01 (dt, 3JH–P = 12.2, 3JH–H = 7.6 Hz, 9H,
PCH2CH3), 1.10 (dt, 3JH–P = 12.2, 3JH–H = 7.6 Hz, 9H, PCH2CH3),
1.25 (dq, 2JH–P = 14.6, 3JH–H = 7.6 Hz, 3H, PCH2CH3), 1.57 (dq,
3
2
2JH–P = 14.6, JH–H = 7.6 Hz, 3H, PCH2CH3), 1.73 (dq, JH–P
=
14.6, 3JH–H = 7.6 Hz, 3H, PCH2CH3 and overlapped 1H), 1.88 (dq,
3
2
2JH–P = 14.6, JH–H = 7.6 Hz, 3H, PCH2CH3), 2.01 (dq, JH–P
=
1
methylphenol (7) in 88% yield. H NMR (300 MHz, benzene-
14.6, 3JH–H = 7.6 Hz, 9H, PCH2CH3), 3.03 (m, 1H, benzylic C3H4),
3
d6, r.t.): d 1.90 (s, 3H, 6-Me), 3.22 (s, 3H, CO2Me), 3.40 (s, 3H,
4.63 (dq, 3JH–P = 19.7, 3JH–H = JH–P = 7.4 Hz, 1H, central-C3H4),
4
4
3
3
CO2Me), 3.46 (d, JH–H = 1.5 Hz, 2H, 2-CH2), 5.78 (t, JH–H
=
5.60 (dt, JH–H = 7.4, JH–P = 3.5 Hz, 1H, terminal-anti-C3H4),
3
1.5 Hz, 1H, CHCO2Me), 6.69 (t, JH–H = 7.5 Hz, 1H, 4-CH),
6.77 (dd, 3JH–H = 7.2, 4JH–H = 2.1 Hz, 1H, 3- or 5-CH), 6.85 (dd,
3JH–H = 7.2, 4JH–H = 2.1 Hz, 1H, 5- or 3-CH). GC-MS (EI): m/z =
264 (M+).
6.67 (td, 3JH–H = 7.2, 4JH–H = 1.2 Hz, 1H, C6H4), 6.80 (d, 3JH–H
=
8.1 Hz, 1H, C6H4), 7.16 (overlapped with benzene, C6H4), 7.46 (dd,
3JH–H = 7.5, 4JH–H = 1.8 Hz, 1H, C6H4). 13C{ H} NMR (74.5 MHz,
1
benzene-d6, r.t.): d 9.0 (d, J = 4 Hz), 9.4 (d, J = 4 Hz), 9.6 (d, J =
4 Hz), 21.2 (d, J = 18 Hz), 22.4 (d, J = 18 Hz), 22.9 (d, J = 18 Hz),
47.1 (dd, J = 23, 3 Hz), 71.4 (dd, J = 23, 3 Hz), 92.5 (s), 111.8
(s), 118.2 (d, J = 5 Hz), 127.2 (s), 130.7 (s), 172.2 (d, J = 8 Hz).
Acidolysis of 3 (4.3 mg, 0.0072 mmol) with 3 drops of DCl/D2O
(37 wt%) in benzene-d6 caused incorporation of D atoms at 52%
at the terminal methine in 7 and no incorporation was observed
at the benzylic position.
31P{ H} NMR (122 MHz, benzene-d6, r.t.): d 21.0 (dd, 2JP–P = 32,
1
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3270–3279 | 3277
©

View Article Online
2
12 Hz, 1P, PEt3), 22.6 (dd, JP–P = 32, 12 Hz, 1P, PEt3), 32.8 (t,
presence of 1,4-dioxane as an internal standard. The product was
identified as 8-methyl-2H-benzopyran (12b) by comparison with
an authentic sample and the yield was estimated as 74%. 1H NMR
2JP–P = 32 Hz, 1P, PEt3). Anal. Calcd for C27H53OP3Ru: C, 55.18;
H, 9.09. Found: C, 55.10; H, 8.92.
(300 MHz, benzene-d6, r.t.): d 2.19 (s, 3H, 8-Me), 4.42 (dd, 3JH–H
=
Preparation of 11b. Similar to 11a, 11b was prepared by the
reaction of 1 (242.0 mg, 0.767 mmol), 2-allyl-6-methylphenol
(126.0 ml, 0.843 mmol) in the presence of PEt3 (340.0 ml,
2.302 mmol) at 50 ◦C for 12 h. Complex 11b was obtained as
yellow blocks from cold Et2O in 38% yield (177.6 mg). 1H NMR
3, 4JH–H = 2 Hz, 2H, 2-CH2), 5.20 (dt, 3JH–H = 10, 3 Hz, 1H, 3-CH),
6.15 (dt, 3JH–H = 10, 4JH–H = 2 Hz, 1H, 4-CH), 6.69–6.89 (m, 3H,
aromatic).
3
3
(300 MHz, benzene-d6, r.t.): d 0.72 (dt, JH–P = 11.7, JH–H
=
Iodolysis of 11c. Complex 11c (38.5 mg, 0.0623 mmol) reacted
with iodine (24.2 mg, 0.0954 mmol) in benzene-d6 (0.6 ml) in
the presence of 1,4-dioxane as an internal standard. The product
was identified as 8-methoxy-2H-benzopyran (12c) by comparison
with an authentic sample and the yield was estimated as 72%. 1H
NMR (300 MHz, benzene-d6, r.t.): d 3.39 (s, 3H, 8-OMe), 4.42
7.5 Hz, 9H, PCH2CH3), 0.98 (dt, 3JH–P = 12.6, 3JH–H = 7.5 Hz, 9H,
PCH2CH3), 1.10 (dt, 3JH–P = 12.3, 3JH–H = 7.5 Hz, 9H, PCH2CH3
2
3
and overlapped 3H), 1.29 (dq, JH–P = 14.3, JH–H = 7.5 Hz, 3H,
PCH2CH3), 1.57 (dq, 2JH–P = 14.3, 3JH–H = 7.5 Hz, 3H, PCH2CH3),
1.75 (dq, 2JH–P = 14.3, 3JH–H = 7.5 Hz, 3H, PCH2CH3), 1.92 (dq,
2JH–P = 14.3, JH–H = 7.5 Hz, 3H, PCH2CH3), 2.06 (dq, JH–P
=
(dd, JH–H = 3, JH–H = 2 Hz, 2H, 2-CH2), 5.20 (dt, JH–H = 10,
3
2
3
4
3
3
14.3, JH–H = 7.5 Hz, 3H, PCH2CH3), 2.39 (s 3H, 6-Me), 2.96
3 Hz, 1H, 3-CH), 6.15 (dt, 3JH–H = 10, 4JH–H = 2 Hz, 1H, 4-CH),
3
3
3
3
3
(m, 1H, benzylic C3H4), 4.64 (dq, JH–P = 11.8, JH–H = JH–P
=
6.49–6.55 (d, JH - H = 8 Hz, 2H, 5- and 7-CH), 6.70 (t, JH - H
8 Hz, 1H, 6-CH).
=
7.7 Hz, 1H, central- C3H4), 5.59 (dt, 3JH–H = 7.7, 3JH–P = 3.3 Hz,
1H, terminal-anti-C3H4), 6.65 (t, 3JH - H = 7.2 Hz, 1H, C6H3), 7.10
(d, 3JH–H = 7.2 Hz, 1H, C6H3), 7.37 (d, 3JH–H = 7.2 Hz, 1H, C6H3).
X-Ray analyses of 3 and 6. A rigaku AFC-7R diffractometer
31P{ H} NMR (122 MHz, benzene-d6, r.t.): d 21.4 (dd, 2JP–P = 31,
1
˚
with graphite-monochromated Mo-Ka (l = 0.71069 A) was used
2
14 Hz, 1P, PEt3), 23.4 (dd, JP–P = 31, 14 Hz, 1P, PEt3), 32.6 (t,
for data collection. Single crystals of 3 suitable for X-ray analysis
were obtained by the recrystallisation of analytically pure solid
of 3 from cold CH2Cl2/hexane. The single crystals of 3 were
sensitive to X-ray irradiation and they decomposed during the
data collection regardless of the measurement temperature. The
best crystallographic data were collected as follows. A selected
crystal of 3 was mounted in a flame-sealed glass capillary (GLASS,
0.7 mm f) under argon. During the data collection, -55.5% decay
of the standard reflections were observed. The collected data
were solved by Direct methods (SIR92), and refined by a full-
matrix least-square procedure using SHELXL9720 on the Crystal
Structure ver.3.8 package program.21 A Psi-Scan was applied
for absorption collections. In the differential Fourier map, C(12)
was found to be disordered, where the alternative methyl group
C(25) was connecting to O(2). The occupancy of C(12)/C(25)
was refined [C(12)occ + C(25)occ = 1.00] and the final population
was estimated to be 0.500/0.500. Although O(2) and O(3) must
also disorder around O(3) and O(2) positions, respectively, they
cannot be found from the differential Fourier-map and they were
treated as virtually ordered oxygen atoms. All non-hydrogen atoms
except C(12) and C(25) were refined with anisotropic displacement
parameters. All hydrogen atoms were added theoretically, riding
on the concerned atoms and were not refined. The crystallographic
data is summarized in Table 3.
2JP - P = 31 Hz, 1P, PEt3). Anal. Calcd for C28H55OP3Ru: C, 55.89;
H, 9.21. Found: C, 56.12; H, 9.50.
Preparation of 11c. Similar to 11a, 11c was prepared by the
reaction of 1 (199.5 mg, 0.632 mmol), 2-allyl-6-methoxyphenol
(107.0 ml, 0.696 mmol) in the presence of PEt3 (280.0 ml,
1.896 mmol) at 50 ◦C for 12 h. Complex 11b was obtained as
yellow blocks from cold Et2O in 42% yield (164.7 mg). 1H NMR
3
3
(300 MHz, benzene-d6, r.t.): d 0.72 (dt, JH–P = 11.7, JH–H
=
7.6 Hz, 9H, PCH2CH3), 1.03 (dt, 3JH–P = 12.6, 3JH–H = 7.6 Hz, 9H,
PCH2CH3), 1.23 (dt, 3JH–P = 14.8, 3JH–H = 7.6 Hz, 9H, PCH2CH3),
1.60 (dq, 2JH–P = 14.9, 3JH–H = 7.6 Hz, 3H, PCH2CH3), 1.79 (dq,
2JH - P = 14.9, JH–H = 7.6 Hz, 3H, PCH2CH3 and overlapped
3
1H), 1.93 (dq, 2JH–P = 14.9, 3JH–H = 7.6 Hz, 3H, PCH2CH3), 2.11
2
3
(dq, JH–P = 14.9, JH–H = 7.6 Hz, 3H, PCH2CH3), 3.12 (m, 1H,
benzylic C3H4), 3.68 (s, 3H, OMe), 4.63 (dq, 3JH–P = 12.0, 3JH–H
3JH - P = 7.4 Hz, 1H, central-C3H4), 5.58 (dt, 3JH–H = 7.4, 3JH–H
=
=
3JH–P = 3.4 Hz, 1H, terminal-anti-C3H4), 6.68 (t, 3JH–H = 7.5 Hz,
3
4
1H, C6H3), 6.74 (dd, JH–H = 7.5, JH–H = 1.5 Hz, 1H, C6H3),
7.21 (dd, 3JH–H = 7.5, 4JH–H = 1.5 Hz, 1H, C6H3). 31P{ H} NMR
1
(122 MHz, benzene-d6, r.t.): d 21.3 (dd, 2JP–P = 31, 13 Hz, 1P, PEt3),
22.7 (dd, 2JP–P = 31, 13 Hz, 1P, PEt3), 32.9 (t, 2JP–P = 31 Hz, 1P,
PEt3). Anal. Calcd for C28H55O2P3Ru: C, 54.44; H, 8.97. Found:
C, 54.70; H, 8.77.
Single crystals of 6 were also obtained from recrystallisation of
6 from a cold CH2Cl2/hexane solution. A selected single crystal
of 6 was mounted on the top of glass capillary by use of Paraton
N oil. The reflection data were collected at 200 K under a cold
nitrogen stream. The collected data were solved by Direct methods
(SIR92), and refined by a full-matrix least-square procedure using
SHELXL9720 on the Crystal Structure ver. 3.8 package program.21
The solved crystal belonged to a chiral space group (Pna21) and
the absolute structure of 6 was determined on the basis of the
anomalous dispersion effect of Friedel pairs.22 All non-hydrogen
atoms were refined with anisotropic displacement parameters.
Hydrogen atoms were added theoretically, riding on the concerned
atoms and were not refined.
Iodolysis of 11a. Complex 11a (74.8 mg, 0.127 mmol) was dis-
solved in benzene (2 ml) into which iodine (48.5 mg, 0.191 mmol)
was added. The yellow solution instantly turned red. After stirring
the solution at room temperature for 12 h, the product was purified
by column chromatography using neutral alumina with Et2O as
eluent to give 2H-benzopyran (12a) in 72% yield. The product
was identified by comparison with an authentic sample. 1H NMR
(300 MHz, benzene-d6, r.t.): d 4.39 (dd, 3JH–H = 3, 4JH–H = 2 Hz,
2H, 2-CH2), 5.17 (dt, 3JH–H = 10, 3 Hz, 1H, 3-CH), 6.10 (dt, 3JH–H
10, 4JH–H = 2 Hz, 1H, 4-CH), 6.75–6.89 (m, 3H, aromatic).
=
Iodolysis of 11b. Complex 11b (41.5 mg, 0.0689 mmol) reacted
with iodine (30.2 mg, 0.118 mmol) in benzene-d6 (0.6 ml) in the
3278 | Dalton Trans., 2009, 3270–3279
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Table 3 Crystallographic data and refinement details for 3 and 6
4 (a) M. Hirano, N. Kurata, T. Marumo and S. Komiya, Organometallics,
1998, 17, 501; (b) M. Hirano, N. Kurata and S. Komiya, J. Organomet.
Chem., 2000, 607, 18; (c) S. Komiya and M. Hirano, J. Chem. Soc.
Dalton Trans., 2003, 1439; (d) M. Hirano, Y. Sakaguchi, T. Yajima,
N. Kurata, N. Komine and S. Komiya, Organometallics, 2005, 24,
4799; (e) M. Hirano, H. Sato, N. Kurata, N. Komine and S. Komiya,
Organometallics, 2007, 26, 2005.
5 V. Ritleng, C. Sirlin and M. Pfeffer, Chem. Rev., 2002, 102, 1731.
6 J. P. Collman, L. S. Hegedus, J. R. Norton, and R. G. Finke, in Principles
and Applications of Organotransition Metal Chemistry, University
Science, 1982, p. 130.
3·CH2Cl2
6·CH2Cl2
Formula
C24H43Cl2O5P3Ru
676.50
monoclinic
P21/n (No.14)
C24H43Cl2O5P3Ru
676.50
orthorhombic
Pna21 (No.33)
Formula weight
Crystal system
Space group
Unit cell dimensions
˚
a (A)
22.265(8)
15.629(14)
9.049(3)
91.11(3)
3143(3)
1.427
298.1
1400.00
0.850
17.068(3)
13.970(3)
13.023(3)
˚
b (A)
7 P. Dani, M. A. M. Toorneman, G. P. M. von Klink and G. van Koten,
Organometallics, 2000, 19, 5287; A. J. Toner, S. Gru¨ndemann, E. Clot,
H.-H. Limbach, B. Donnadieu, S. Sabo-Etienne and B. Chaudret, J.
Am. Chem. Soc., 2000, 122, 6777; Y. Takahashi, S. Hikichi, M. Akita
and Y. Moro-oka, Organometallics, 1999, 18, 2571; A. R. Cowley, J. R.
Dilworth and C. A. M. von Beckh W., Acta Crystal. Sec. E, 2005, 61,
m1237.
˚
c (A)
b (deg)
3
˚
V (A )
3105.1(10)
1.447
200.0
1400.00
0.862
4281
Dcalcd (g cm-1)
Temp (K)
F(000)
m (mm-1)
˚
8 Ru(II)–H distances are suggested in the range 2.86–3.06 A: R.-M.
Unique reflections
No. of observed reflections
[F2>2s(F2)]
Crystal size (mm)
No. of variables in LS
Flack parameter
Goodness of fit
R1(wR2)
7233
2968
Catala, D. Cruz-Garritz, P. Terreros, H. Torrens, A. Hills, D. L. Hughes
and R. L. Richards, J. Organomet. Chem., 1987, 328, C37; R.-M.
Catala, D. Cruz-Garritz, P. Terreros, H. Torrens, A. Hills, D. L. Hughes
and R. L. Richards, J. Organomet. Chem., 1989, 359, 219; M. Okazaki,
N. Yamahira, J. J. G. Minglana, T. Komuro, H. Ogino and H. Tobita,
Organometallics, 2008, 27, 918.
3035
0.40 ¥ 0.20 ¥ 0.10
315
0.35 ¥ 0.20 ¥ 0.10
329
-0.06(3)
1.025
0.0318(0.0810)
0.946
0.0502 (0.1539)
9 A. Yamamoto, in Organotransition Metal Chemistry, Fundamental
Concepts and Application, Wiley, New York, 1986, p. 179.
10 M. Brookhart and M. L. H. Green, J. Organomet. Chem., 1983, 250,
395.
11 R. Ugi, D. Marquading, K. Klusacek, P. Gillespie and F. Ramirez, Acc.
Acknowledgements
Chem. Res., 1971, 4, 288.
12 M. Miura, T. Tsuda, T. Satoh and M. Nomura, Chem. Lett., 1997,
1103.
13 M. I. Bruce, in Comprehensive Organometallic Chemistry, ed. G.
Wilkinson, F. G. A. Stone, E. W. Abel, Pergamon, Oxford, 1982, Vol.
4, p 651.
The authors are grateful to Prof. H. Uekusa (Tokyo Institue of
Technology) for tips on the X-ray crystallography of 6. We also
thank Ms. S. Kiyota for elemental analyses and Prof. K. Noguchi
for installation of the SHELXL-97 program. This work was
financially supported by a Grant-in-Aid for Scientific Research
from the Ministry of Education, Culture, Sports, Science and
Technology, Japan and Japan Society for the Promotion of
Science.
14 G. Mann, D. Baranano, J. F. Hartwig, A. L. Rheingold and I. A. Guzei,
J. Am. Chem. Soc., 1998, 120, 9205; M. S. Driver and J. F. Hartwig, J.
Am. Chem. Soc., 1997, 119, 8332; G. Mann and J. F. Hartwig, J. Am.
Chem. Soc., 1996, 118, 13109; D. Baranano and J. F. Hartwig, J. Am.
Chem. Soc., 1995, 117, 2937; R. A. Widenhoefer and S. L. Buchwald,
J. Am. Chem. Soc., 1998, 120, 6504; R. A. Widenhoefer, H. A. Zhong
and S. L. Buchwald, J. Am. Chem. Soc., 1997, 119, 6787.
15 H. C. L. Abbenhuis, M. Pfeffer, J.-P. Sutter, A. de Cian, J. Fischer, H.
L. Ji and J. H. Nelson, Organometallics, 1993, 12, 4464.
16 W. Ferstl, I. K. Sakodinskaya, N. Beydoun-Sutter, G. Le Borgne, M.
Pfeffer and A. D. Ryabov, Organometallics, 1997, 16, 411.
17 W. E. Parthan and L. D. Huestis, J. Am. Chem. Soc, 1962, 84, 813.
18 K. Anderson and E. J. Lavoie, J. Org. Chem., 1973, 22, 3832.
19 G. M. Kosolapoff and L. Maier, in Organic Phosphorus Compounds,
Wiley, New York, 1972, Vol. 1, p. 32.
Notes and references
1 A. S. Goldman, and K. I. Goldberg, in Activation and Functionalization
of C–H Bonds, ACS symposium series, 885, American Chemical
Society, Washington, DC, 2004S. Murai, in Activation of Unreactive
Bonds and Organic Synthesis, Springer, Berlin, 1999; B. A. Arndtsen,
R. G. Bergman, T. A. Mobley and T. H. Peterson, Acc. Chem. Res,
1995, 28, 154; R. H. Crabtree, Chem. Rev, 1985, 85, 254; E. Shilov and
A. A. Shteinman, Coord. Chem. Rev, 1977, 24, 97.
20 G. M. Sheldrick, SHELXL97, A program for Crystal Structure Refine-
ment, University of Go¨ttingen, Germany, 1997.
21 Rigaku Americas and Rigaku Corporation (2007). Crystal Structure
(Version 3.8). Single Crystal Structure Analysis Software. Rigaku
Americas, 9009 TX, USA 77381–5209. Rigaku, Tokyo 196–8666,
Japan.
2 J. Chatt and J. M. Davidson, J. Chem. Soc., 1965, 843.
3 For examples, D. Rabinovich, R. Zelman and G. Parkin, J. Am. Chem.
Soc., 1990, 112, 9632; D. Rabinovich, R. Zelman and G. Parkin, J. Am.
Chem. Soc., 1992, 114, 4611; T. Hascall, V. J. Murphy and G. Parkin,
Organometallics, 1996, 15, 3910; W. D. Jones and W. P. Kosar, J. Am.
Chem. Soc., 1986, 108, 5640; G. C. Hsu, W. P. Kosar and W. D. Jones,
Organometallics, 1994, 13, 385.
22 H. D. Flack, Acta Cryst., 1983, A39, 876.
23 M. J. Burn and R. G. Bergman, J. Organomet. Chem., 1994, 472, 43.
24 K. Osakada, K. Ohshiro and A. Yamamoto, Organometallics, 1991,
10, 404.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3270–3279 | 3279
©