Ru(0)-Catalyzed Straightforward Synthesis of Conjugated Tetraenes: An Approach using Two Internal Alkynes with 1,3-Butadiene

Article abstract of DOI:10.1021/acs.organomet.7b00801

The Ru(0)-catalyzed straightforward synthesis of conjugated tetraenes has been achieved in up to 85% yield by coupling of 2 equiv of internal alkynes with 1,3-butadiene at room temperature. The stoichiometric reaction of [Ru(?⁴-cisoid-1,3-butadiene)(?⁴-1,5-COD)(NCMe)] with 2 equiv of 3-hexyne produces a tetraene complex of Ru(0), [Ru{3-6-?⁴-(3E,5E,7E,9E)-4,9-diethyldodeca-3,5,7,9-Tetraene}(?⁴-1,5-COD)(NCMe)], in 98% yield, which releases the conjugated tetraene ligand in 92% yield by exposure to 1,3-butadiene.

Full text of DOI:10.1021/acs.organomet.7b00801

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Ru(0)-Catalyzed Straightforward Synthesis of Conjugated Tetraenes:
An Approach using Two Internal Alkynes with 1,3-Butadiene
Sayori Kiyota and Masafumi Hirano*
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16
Nakacho, Koganei, Tokyo 184-8588, Japan
S
* Supporting Information
ABSTRACT: The Ru(0)-catalyzed straightforward synthesis of con-
jugated tetraenes has been achieved in up to 85% yield by coupling of 2
equiv of internal alkynes with 1,3-butadiene at room temperature. The
stoichiometric reaction of [Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)-
(NCMe)] with 2 equiv of 3-hexyne produces a tetraene complex of
Ru(0), [Ru{3−6-η4-(3E,5E,7E,9E)-4,9-diethyldodeca-3,5,7,9-tetraene}-
(η4-1,5-COD)(NCMe)], in 98% yield, which releases the conjugated
tetraene ligand in 92% yield by exposure to 1,3-butadiene.
Scheme 1. Catalytic Approaches to Conjugated Tetraenes
INTRODUCTION
■
Conjugated tetraenes are important substructures of many
biologically active and natural products.1 Wittig and Horner−
Wadsworth−Emmons reactions2 are conventional methods of
choice for their preparation. However, these reactions require
repetition of the subsequent reduction of the resulting ester to a
primary alcohol and partial oxidation to the corresponding
aldehyde to expand further CC bonds. Takahashi and co-
workers reported stoichiometric synthesis of conjugated
tetraenes from zirconacyclopentadiene.3 The catalytic ap-
proaches involve combination of Sonogashira coupling and
subsequent reduction of the alkynyl fragment (Scheme 1a).4
This method contains the (Z)-CC substructure resulting
from the partial hydrogenation of the CC bond. The most
used catalytic approach is presumably Suzuki−Miyaura
coupling (Scheme 1b).5 This method employs trienyl halide,
which is normally prepared by a stoichiometric Wittig reaction,
or dienyl halide, with an alkenyl- or dienylborane. Therefore,
the overall step and atom efficiency are limited. Satoh, Miura,
and co-worker documented an interesting three-component
coupling among dienyl bromide, diphenylacetylene, and an
acrylate (Scheme 1c).6 Because they showed only one synthetic
example, the scope and limitation of this reaction are not clear.
In 1977, Pauson and Khand reported the stoichiometric
reaction of [Co2(μ-PhCCPh)(CO)6] with 3-sulfolene to
produce 1,2,7,8-tetraphenyloctateteraene in 12% yield (eq 1).7
In this paper, we report the catalytic approach to conjugated
tetraenes from two internal alkynes with 1,3-butadiene
catalyzed by a Ru(0) complex (Scheme 1d).
RESULTS AND DISCUSSION
■
We recently reported the direct coupling of internal alkenes
with 1-substituted 1,3-dienes to give conjugated trienes
catalyzed by [Ru(η6-naphthalene)(η4-1,5-COD)] (1).8 When
this strategy was extended to 1,3-butadiene, the terminal C1
Received: November 2, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
and C4 carbons in 1,3-butadiene both reacted with internal
alkynes to give conjugated tetraenes with perfect regio- and
stereoselectivity (Table 1).9
dominantly produced tetraenes (entries 7−9), the reaction
using 2-butyne (2e) gave the coupling products in modest yield
and the concomitant [2 + 2 + 2] cyclotrimerization product
was observed (entry 10). This fact shows the cyclotrimerization
of alkynes to be a potential side reaction in this process. With
diphenylacetylene (2f), the tetraene product (1Z,3E,5E,7Z)-
1,2,7,8-tetraphenylocta-1,3,5,7-tetraene (4f) exclusively depos-
ited from the reaction mixture (entry 11). Electron-deficient
diarylacetylene gave the coupling product in low yield (entries
13 and 14). Note that reactions using 1-substituted butadiene
such as 1,3-pentadiene produced conjugated trienes and those
using 2-substituted butadiene such as isoprene and 2,3-
dimethylbutadiene shut down the catalysis.8 Reactions using
terminal alkynes gave complex mixtures. These are limitations
of the present catalysis.
Table 1. Reactions of Internal Alkyes 2 with 1,3-Butadiene
a
(3) Catalyzed by 1
yield/%
Treatment of 3-hexyne (2d) with 3 in a 1/1 ratio in the
presence of a catalytic amount of 1 (10 mol %) produced a
mixture of tetraene 4d (17%) and triene 5d (43%). Further
addition of 1 equiv of 2d to this mixture increased 4d (50%)
with a decrease in 5d (5%). This experiment suggests that the
conjugated triene does react with an added alkyne to produce
tetraene.
entry
1
R
4a−i
5a−i
isopentyl
isopentyl
isopentyl
isopentyl
isopentyl
isopentyl
butyl
85 (4a)
65 (4a)
50 (4a)
71 (4a)
19 (4a)
23 (4a)
60 (4b)
57 (4c)
64 (4d)
11 (4e)
41 (4f)
41 (4g)
23 (4h)
2 (4i)
13 (5a)
7 (5a)
bc
,
2
3
4
cd
,
21 (5a)
4 (5a)
ce
,
fg
5 ,
53 (5a)
59 (5a)
13 (5b)
11 (5c)
13 (5d)
13 (5e)
8 (5f)
fh
6 ,
When [1,1,4,4-2H4]-1,3-butadiene (3-d4) was employed in
the reaction with 2a, [5,7,10,12-2H4]-4a-d4 was observed by 1H
7
8
propyl
i
9
ethyl
j
10
11
12
13
14
methyl
phenyl
k
l
4-tolyl
0 (5g)
m
m
n
4-chlorophenyl
8 (5h)
4-trifluoromethylphenyl
0 (5i)
a
Typical conditions: 1 (20 mol %), 2 (0.24 mmol), 3 (0.11 mmol),
1
room temperature, time 1 day. Yields were estimated by H NMR
using triphenylmethane or dibenzyl as an internal standard. Solvent
b
c
d
toluene-d8. Temperature 30 °C. Solvent dichloromethane-d2.
e
f
g
Solvent acetone-d6. 1 (5 mol %). Temperature 18 °C.
h
i
j
k
Temperature 50 °C. Time 5 days. Time 3 days. 1 (10 mol %),
l
m
time 14 h. 1 (10 mol %), 2 (0.13 mmol), 3 (0.055 mmol). 2 (0.13
mmol), 3 (0.055 mmol), time 3 days. NMR resonances for 5h were
n
obscured by overlapping with unidentified resonances. 5h was
tentatively identified by the characteristic terminal dienyl resonances.
and 2H{1H} NMR along with the triene (eq 2 and Figure 1). In
1H NMR spectrum of 4a-d4, the AA′BB′ pattern assignable to
7- and 10-CH almost completely disappeared, and the 8- and 9-
CH resonances appeared as a singlet. Consistently, the 4- and
13-CH2 protons, which were observed as a doublet of triplets
for 4a, changed to a triplet. The deuterium contents were
estimated to be up to 98 atom % D for 7- and 10-CH and 87
atom % D for 5- and 12-CH in 4a-d4.
Treatment of 2 equiv of 2,9-dimethyldeca-5-yne (2a) with
1,3-butadiene (3) in the presence of a catalytic amount of 1 (20
mol % based on 3) at room temperature in benzene produced
(5E,7E,9E,11E)-2,15-dimethyl-6,11-isopentylhexadeca-5,7,9,11-
tetraene (4a) in 85% yield along with (3E,5E)-9-methyl-5-
isopentyldeca-1,3,5-triene (5a) in 13% yield (Table 1, entry 1).
Compounds 4a and 5a can be separated by recycling HPLC
(GPC) using chloroform as the eluent. Conjugated tetraene 4a
This result is regarded as a formal syn addition of the C−H
bond in butadiene to internal alkynes.
1
was fully characterized by H and 13C{1H} NMR and HRMS
(APCI), and the stereochemistry was confirmed by a pNOESY
experiment. This reaction also proceeded in toluene, dichloro-
methane, and acetone, but benzene was the most promising
solvent among them (entries 2−4). With low catalyst loading
(5 mol %), the formation of 5a was promoted and no
significant improvement was observed at 50 °C (entries 5 and
6). Although the reason for the catalysis with low catalyst
loading to encourage the formation of conjugated triene 5a is
not clear, one of the possible explanations is that the conjugated
triene ligand is liberated from an intermediate but the low
catalyst concentration discourages the subsequent reaction to
give a tetraene. Although similar reactions using alkylacetylenes
A stoichiometric reaction of [Ru(η4-cisoid-1,3-butadiene)(η4-
1,5-COD)(NCMe)] (6)10 with 2d in benzene-d6 quickly gave a
transient intermediate at room temperature, which was
supposed to be a conjugated triene complex along with the
tetraene complex [Ru{3−6-η4-(3E,5E,7E,9E)-4,9-diethyldode-
ca-3,5,7,9-tetraene}(η4-1,5-COD)(NCMe)] (7), and all species
were eventually converted into 7 in 98% yield within 5 min
(Scheme 2). Complex 7 has a conjugated tetraene ligand,
whose stereochemistry was unequivocally determined by a
pNOESY experiment. The methine resonances in the tetraene
ligand are observed in benzene-d6 at δ 0.78 (dd, J = 7.4, 4.6 Hz,
3-CH), 1.78 (dd, J = 9.7, 8.0 Hz, 6-CH), 5.06 (d, J = 8.0 Hz, 5-
B
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 3. Formation of supine,prone-8 by the Oxidative
Coupling between cisoid- and transoid-Butadiene Ligands on
Ru(0)
All of these catalytic and stoichiometric reactions and
isotopic labeling experiments are consistent with the mecha-
nism shown in Scheme 4, for the reaction of 3-hexyne (2d)
with 3 as a typical example.8,12
Scheme 4. Possible Mechanism for Conjugated Tetraene
Synthesis Catalyzed by a Ru(0) Complex
1
Figure 1. H NMR spectra in the region of alkenyl and methylene
protons for 4a (a) and 4a-d4 (b) in C6D6.
Scheme 2. Stoichiometric Reaction of Butadiene Complex 6
with 2-Hexyne (2d)
CH), 5.38 (t, J = 7.4 Hz, 10-CH), 5.94 (dd, J = 15.5, 9.7 Hz, 7-
CH), and 6.18 (d, J = 15.5 Hz, 8-CH). The methylene protons
in the 2-position and in the 4-ethyl group were observed as
diastereotopic protons, consistent with the coordination of the
tetraene fragment to Ru.
A 3H broad resonance at δ 0.83−0.88 suggests coordination
of an acetonitrile ligand. Further treatment of 7 with 2.5 equiv
of 1,3-butadiene (3) released conjugated tetraene 4d in 92%
yield along with supine,prone-bis(η3-allylic)ruthenium(II) com-
plex 8. Because 8 is formed by the independent reaction of 6
with 3 (Scheme 3),11 the observation of 8 suggests regeneration
of 6 from 7.
On the other hand, the tetraene complex 7 did not release 4d
even when 5 equiv of 3-hexyne (2d) was added. 7 gradually
decomposed at room temperature; after 10 h it became an
unidentified complex mixture, in which conjugated tetraene 4d
was not observed.
First of all, the 6π naphthalene ligand in 1 was readily
displaced by 4π butadiene (3) and 2π 3-hexyne (2d), giving A
to satisfy the 18e rule. The excellent substrate selectivity in this
reaction comes from this identification on the basis of
coordination numbers. Then, the oxidative coupling reaction
occurs to give B.13 The subsequent β-hydride elimination
selectively occurs from the Hendo methylene protons by rotation
of the resulting C−C single bonds. This diastereotopic
selectivity determines the stereoselectivity to give the (E)-
CC bond. After the reductive elimination giving D, the
second 2d comes to the Ru center to produce E probably by
the same mechanism noted in the processes from A to D.
Because Fukumoto and Mashima have documented facile
migration of the RuClCp fragment on the conjugated
polyenes,14 migration of the coordinated Ru(η4-1,5-COD)
fragment on the conjugated tetraene ligand is probably facile
C
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
and it finally settles into the most stable position. Note that we
observed 7, which strongly supports E. Finally, reaction of 2d
and 3 with E liberates the conjugated tetraene 4d with
regeneration of A.
Conjugated triene, a side product in this reaction, is probably
liberated from D. According to the stoichiometric reaction
shown in Scheme 2, there is presumably no need to liberate the
conjugated triene ligand from D, although a coupling reaction
using a bulky alkyne such as 2,9-dimethyldeca-5-yne (2a) may
be prone to liberate the conjugated triene ligand. In either
event, the present study shows that the conjugated triene can
get back in the catalytic cycle again.
1H NMR (400 MHz, C6D6, room temperature): δ 0.88 (d, 3JH−H
=
3
6.8 Hz, 12H, 1-, 16-, 17- and 28-CH3), 0.93 (d, JH−H = 6.8 Hz, 12H,
21-, 22-, 26- and 27-CH3), 1.27 (dt, 3JH−H = 8.8, 6.8 Hz, 4H, 3- and 14-
2
3
CONCLUDING REMARKS
CH2), 1.48 (AA′XX′Y, JH−H = −10 Hz, JH−H = 8.7, 6.5 Hz, 4H, 19-
■
3
and 24-CH2), 1.53 (n, JH−H = 6.8 Hz, 2H, 20- and 25-CH) 1.58 (n,
In summary, we have developed a new protocol for conjugated
tetraene synthesis by the Ru(0)-catalyzed direct coupling of
internal alkynes with 1,3-butadiene. This is the most direct
approach to conjugated tetraene ever reported, which can start
from commercially available reagents.
3JH−H = 6.8 Hz, 2H, 2- and 15-CH), 2.16 (dt, 3JH−H = 8.4, 7.2 Hz, 4H,
2
3
4- and 13-CH2), 2.36 (AA′XX′, JH−H = −10 Hz, JH−H = 8.7, 6.5 Hz,
4H, 18- and 23-CH2), 5.50 (t, JH−H = 7.2 Hz, 2H, 5- and 12-CH),
3
3
4
5
6.37 (AA′BB′, JH−H = 17.5, JH−H = 0.5 Hz, JH−H = 0.1 Hz, 2H, 7-
and 10-CH), 6.53 (AA′BB′, 3JH−H = 17.5, 10.5 Hz, 4JH−H = 0.1 Hz, 2H,
8- and 9-CH). 13C{1H} NMR (100.5 MHz, C6D6, room temperature):
δ 22.67, 22.69, 25.2, 26.6, 28.0, 28.8, 38.8, 39.3, 127.4, 133.1, 136.3,
139.4. HRMS(APCI): C28H50 (386.39) m/z 387.3972 (M + 1H)+,
calcd for C28H51 387.3951.
EXPERIMENTAL SECTION
■
General Procedures. All procedures described in this paper were
carried out under a nitrogen or argon atmosphere by use of Schlenk
and vacuum line techniques. Benzene was dried and purified using a
Glass Contour Ultimate Solvent System. Benzene-d6 and toluene-d8
were dried over sodium wire and stored under vacuum, and they were
transferred into an NMR tube or a 25 mL Schlenk tube by vacuum
distillation prior to use. Chloroform-d was used as received.
Dichloromethane-d2 and acetone-d6 were deried over Drierite and
P2O10, respectively, and were distilled under reduced pressure. 2,9-
Dimethyldeca-5-yne (2a), 5-decyne (2b), 4-octyne (2c), 3-hexyne
(2d), 2-butyne (2e), and diphenylacetylene (2f) were purchased from
the commercial suppliers and stored under a nitrogen atmosphere after
three freeze−pump−thaw cycles. 1,3-Butadiene (3) was purchased
from commercial suppliers and was used as received. [Ru(η6-
naphthalene)(η4-1,5-COD)] (1) and diarylacetylenes 2g−i were
1H NMR (400 MHz, C6D6, room temperature): δ 0.85 (12H, 10-,
14-, 15- and 16-CH3, overlapped with signals for 4a), 1.2−1.3 (m, 4H,
8- and 12-CH2, overlapped with signals for 4a), 1.5−1.7 (2H, 9- and
13-CH2, overlapped with signals for 4a), 2.1 (2H, 7-CH2, overlapped
prepared according to literature procedures.15−19 1H, H{1H}, 13C-
2
3
with signals for 4a), 2.25 (m, 2H, 11-CH2), 5.01 (dd, JH−H = 9.8 Hz,
{1H}, and 19F{1H} NMR spectra were measured on a JEOL ECX-
3
2
2JH−H = 1.6 Hz, 1H, 1-CH), 5.18 (dd, JH−H = 16.0, JH−H = 1.6 Hz,
1H, 1-CH), 5.44 (t, 3JH−H = 7.4 Hz, 1H, 6-CH), 6.21 (d, 3JH−H = 15.0
Hz, 1H, 4-CH), 6.3−6.5 (2H, 3- and 2-CH, overlapped with signals for
4a).
1
400P spectrometer (400 MHz for H). Some coupling constants for
multiplet resonances were estimated by gNMR.20 GC and GC-MS
were performed on Shimadzu GC-2014 (FID) and Shimadzu GCMS-
2010 (EI) instruments, respectively, equipped with a TC-1 column
(0.25 mm i.d. × 30 m). HRMS(APCI) analysis was performed on a
Bruker Daltonics micrOTOF-QII instrument. Preparative scale HPLC
was performed with a Japan Analytical Industry LaboACE LC-5060
instrument equipped with JAIGEL-1H and JAIGEL-2HR tandem
columns using chloroform as the eluent.
Reaction of 5-Decyne (2b) with 1,3-Butadiene (3).
(5E,7E,9E,11E)-6,11-Dibutylhexadeca-5,7,9,11-tetraene (4b): pale
brown oil, 60% yield.
Typical Reaction of 2,9-Dimethyldeca-5-yne (2a) with 1,3-
Butadiene (3). Complex 1 (7.43 mg, 0.0220 mmol) was placed in an
NMR tube under a nitrogen atmosphere, and 2,9-dimethyldeca-5-yne
(2a; 52.0 μL, 0.242 mmol) and C6D6 (600 μL) were added. To the
solution was added 1,3-butadiene (3; 2.44 mL, 0.109 mmol) by a
hypodermic syringe at room temperature. The mixture was allowed to
react at room temperature for 1 day, during which time the reaction
1
was monitored by H NMR spectroscopy. In order to determine the
yield of the product, dibenzyl (6.35 mg, 0.0348 mmol) was added to
the reaction mixture as an internal standard. The yield of
(5E,7E,9E,11E)-2,15-dimethyl-6,11-isopentylhexadeca-5,7,9,11-tet-
raene (4a) was estimated as 85% along with (3E,5E)-9-methyl-5-
isopentyldeca-1,3,5-triene (5a) in 13% yield. The reaction mixture was
purified by a recycle HPLC to obtain a pale brown oil of 4a (18.5 mg,
0.0478 mmol) in 44% yield.
Similar treatments using 5 mol % of 1 in benzene-d6 at 18 and 50
°C and treatments using 20 mol % of 1 in toluene-d8, dichloro-
methane-d2, acetone-d6 at 30 °C produced 4a and 5a, as shown in
Table 1.
3
1H NMR (400 MHz, C6D6, room temperature): δ 0.88 (t, JH−H
=
7.6 Hz, 6H, 1- and 16-CH3), 0.90 (t, 3JH−H = 7.2 Hz, 6H, 20- and 24-
CH3), 1.24−1.40 (m, 12H, 2-, 3-, 14-, 15-, 19- and 23-CH2), 1.52
3
(pseudo quint, 4H, 18- and 22-CH2), 2.13 (q, JH−H = 7.4 Hz, 4H, 4-
3
and 13-CH2), 2.33 (pseudo t, 4H, 17- and 21-CH2), 5.50 (t, JH−H
=
=
=
3
4
7.4 Hz, 2H, 5- and 12-CH), 6.33 (AA′BB′, JH−H = 16.5 Hz, JH−H
5
3
0.1 Hz, JH−H = 0.1 Hz, 2H, 7- and 10-CH), 6.49 (AA′BB′, JH−H
16.5, 11.0 Hz, JH−H = 0.1 Hz, 2H, 8- and 9-CH). 13C{1H} NMR
4
(100.5 MHz, C6D6, room temperature): δ 14.21, 14.24, 22.8, 23.3,
D
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
27.0, 28.4, 31.8, 32.3, 127.5, 133.2, 136.4, 139.2. HRMS(APCI):
C24H42 (330.33) m/z 331.3351 (M + H)+, calcd for C24H43 331.3365.
(3E,5E)-5-butyldeca-1,3,5-triene (5b): 13% yield.
3
1H NMR (400 MHz, C6D6, room temperature): δ 0.92 (t, JH−H
=
7.6 Hz, 6H, 1- and 12-CH3), 1.04 (t, 3JH−H = 7.6 Hz, 6H, 14- and 16-
CH3), 2.03 (quint, 3JH−H = 7.6 Hz, 4H, 2- and 11-CH2), 2.23 (q, 3JH−H
= 7.6 Hz, 4H, 13- and 15-CH2), 5.43 (t, 3JH−H = 7.6 Hz, 2H, 3- and 10-
CH), 6.25 (AA′BB′, 3JH−H = 16.5 Hz, 4JH−H = 0.5 Hz, 5JH−H = 0.1 Hz,
2H, 5- and 8-CH), 6.40 (AA′BB′, JH−H = 16.5, 11.0 Hz, JH−H = 0.1
Hz, 2H, 7- and 6-CH). 13C{1H} NMR (100.5 MHz, C6D6, room
temperature): δ 14.1, 14.5, 20.2, 21.7, 127.4, 134.0, 135.8, 140.3.
HRMS(APCI): C16H26 (218.20) m/z 219.2103 (M + H)+, calcd for
C16H27 219.2107.
3
4
3
1H NMR (400 MHz, C6D6, room temperature): δ 0.86 (t, JH−H
=
7.6 Hz, 3H, 10-CH3), 0.86 (t, 3JH−H = 7.6 Hz, 3H, 14-CH3), 1.20−1.38
(m, 6H, 8-, 9- and 13-CH2), 1.44 (quint, 3JH−H = 7.6 Hz, 2H, 12-CH2),
2.07 (q, 3JH−H = 7.2 Hz, 2H, 7-CH2), 2.19 (t, 3JH−H = 7.6 Hz, 2H, 11-
3
2
CH2), 5.02 (dd, JH−H = 10.0 Hz, JH−H = 1.6 Hz, 1H, 1-CH), 5.18
(dd, 3JH−H = 16.4, 2JH−H = 1.6 Hz, 1H, 1-CH), 5.45 (t, 3JH−H = 7.2 Hz,
(3E,5E)-5-Ethylocta-1,3,5-triene (5d): 13% yield.
3
3
1H, 6-CH), 6.21 (d, JH−H = 15.6 Hz, 1H, 4-CH), 6.33 (dd, JH−H
=
15.6, 10.4 Hz, 1H, 3-CH), 6.43 (dt, 3JH−H = 16.4, 10.4 Hz, 1H, 2-CH).
Reaction of 4-Octyne (2c) with 1,3-Butadiene (3).
(4E,6E,8E,10E)-5,10-Dipropyltetradeca-4,6,8,10-tetraene (4c): pale
brown oil, 57% yield.
3
1H NMR (400 MHz, C6D6, room temperature): δ 0.88 (t, JH−H
=
7.4 Hz, 3H, 8-CH3), 0.99 (t, 3JH−H = 7.4 Hz, 3H, 10-CH3), 2.03 (quint,
3JH−H = 7.4 Hz, 2H, 7-CH2), 2.18 (q, 3JH−H = 7.4 Hz, 2H, 9-CH2), 5.01
3
2
3
(dd, JH−H = 10.9 Hz, JH−H = 1.4 Hz, 1H, 1-CH), 5.16 (dd, JH−H
=
16.6, 2JH−H = 1.4 Hz, 1H, 1-CH), 5.35 (t, 3JH−H = 7.4 Hz, 1H, 6-CH),
3
6.14 (d, JH−H = 15.5 Hz, 1H, 4-CH), 6.2−6.4 (2H, 2- and 3-CH,
overlapped with signals for 4d).
3
1H NMR (400 MHz, C6D6, room temperature): δ 0.88 (t, JH−H
=
Reaction of 2-Butyne (2e) with 1,3-Butadiene (3).
(2E,4E,6E,8E)-3,8-Dimethyldeca-2,4,6,8-tetraene (4e): pale gray sticky
solid, 11% yield.
7.2 Hz, 6H, 1- and 14-CH3), 0.92 (t, 3JH−H = 7.2 Hz, 6H, 17- and 20-
3
CH3), 1.35 (sext, JH−H = 7.5 Hz, 4H, 2- and 13-CH2), 1.53 (sext,
3JH−H = 7.5 Hz, 4H, 16- and 19-CH2), 2.07 (q, 3JH−H = 7.4 Hz, 4H, 3-
3
and 12-CH2), 2.28 (t, JH−H = 7.5 Hz, 4H, 15- and 18-CH2), 5.50 (t,
3JH−H = 7.4 Hz, 2H, 4- and 11-CH), 6.27 (AA′BB′, JH−H = 15.8 Hz,
3
4JH−H = 0.5 Hz, JH−H = 0.1 Hz, 2H, 6- and 9-CH), 6.43 (AA′BB′,
5
3JH−H = 15.8, 10.5 Hz, JH−H = 0.1 Hz, 2H, 7- and 8- CH). 13C{1H}
4
NMR (100.5 MHz, C6D6, room temperature): δ 14.1, 14.4, 22.7, 23.3,
29.2, 30.8, 127.5, 133.2, 136.3, 139.1. HRMS(APCI): C20H34 (274.27)
m/z 275.2737 (M + H)+, calcd for C20H35 275.2739.
1H NMR (400 MHz, C6D6, room temperature): δ 1.59 (d, 3JH−H
=
6.8 Hz, 6H, 1- and 10-CH3), 1.69 (s, 6H, 11- and 12-CH3), 5.52 (qq,
(3E,5E)-5-Propylnona-1,3,5-triene (5c): 11% yield.
4
3JH−H = 6.8 Hz, JH−H = 0.8 Hz, 2H, 2- and 9-CH), 6.33 (AA′BB′,
4
5
3JH−H = 15.5, 10.0 Hz, JH−H = −1.0 Hz, JH−H = 3 Hz, 2H, 4- and 7-
CH), 6.36 (AA′BB′, 3JH−H = 15.5, 10.0 Hz, 4JH−H = −1.0 Hz, 5JH−H = 3
Hz, 2H, 5- and 6-CH). 13C{1H} NMR (100.5 MHz, C6D6, room
temperature): δ 12.1, 14.0, 126.7, 127.4, 135.4, 137.1.
(3E,5E)-5-Methylhepta-1,3,5-triene (5e): 13% yield.
3
1H NMR (400 MHz, C6D6, room temperature): δ 0.85 (t, JH−H
=
7.6 Hz, 3H, 9-CH3), 0.86 (t, 3JH−H = 7.6 Hz, 3H, 12-CH3), 1.31 (sext,
3JH−H = 7.6 Hz, 2H, 8-CH2), 1.44 (sext, 3JH−H = 7.6 Hz, 2H, 11-CH2),
2.00 (q, 3JH−H = 7.6 Hz, 2H, 7-CH2), 2.19 (t, 3JH−H = 7.6 Hz, 2H, 10-
1H NMR (400 MHz, C6D6, room temperature): δ 1.59 (d, 3JH−H
=
3
2
CH2), 5.01 (dd, JH−H = 10.0 Hz, JH−H = 1.6 Hz, 1H, 1-CH), 5.17
(dd, 3JH−H = 16.6, 2JH−H = 1.6 Hz, 1H, 1-CH), 5.43 (t, 3JH−H = 7.6 Hz,
7.4 Hz, 3H, 7-CH3), 1.68 (s, 3H, 8-CH3, overlapped with signals for
4e), 5.01 (d, 3JH−H = 9.7 Hz, 1H, 1-CH), 5.16 (d, 3JH−H = 16.6, 1H, 1-
3
3
1H, 6-CH), 6.18 (d, JH−H = 16.0 Hz, 1H, 4-CH), 6.29 (dd, JH−H
=
3
3
16.0, 10.0 Hz, 1H, 3-CH), 6.42 (dt, 3JH−H = 16.6, 10.0 Hz, 1H, 2-CH).
HRMS(APCI): C12H20 (164.16) m/z 165.1647 (M + H)+, calcd for
C12H21 165.1643.
CH), 5.45 (q, JH−H = 7.4 Hz, 1H, 6-CH), 6.18 (d, JH−H = 16.6 Hz,
1H, 4-CH), 6.2−6.3 (1H, 3-CH, overlapped with signals for 4e), 6.39
3
(dt, JH−H = 16.6, 9.7 Hz, 1H, 2-CH).
Reaction of Diphenylacetylene (2f) with 1,3-Butadiene (3).
(1Z,3E,5E,7Z)-1,2,7,8-Tetraphenylocta-1,3,5,7-tetraene (4f): yellow
powder, 41% yield.
Reaction of 3-Hexyne (2d) with 1,3-Butadiene (3).
(3E,5E,7E,9E)-4,9-Diethyldodeca-3,5,7,9-tetraene (4d): pale gray
solid, 64% yield.
E
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1H NMR (400 MHz, CDCl3, room temperature): δ 5.93 (AA′XX′,
3JH−H = 15.0, 6.0 Hz, 4JH−H = −1.0 Hz, 5JH−H = 0.0 Hz, 2H, 3- and 6-
3
4
5
CH), 6.48 (AA′XX′, JH−H = 15.0, 6.0 Hz, JH−H = −1.0 Hz, JH−H
=
0.0 Hz, 2H, 4- and 5-CH), 6.50 (s, 2H, 1- and 8-CH), 6.81 (dd, 3JH−H
= 7.2 Hz, 4JH−H = 2.0 Hz, 4H, o-C6H5), 7.01−7.06 (m, 6H, m- and p-
C6H5), 7.14 (dd, 3JH−H = 7.2 Hz, 4JH−H = 1.6 Hz, 4H, o-C6H5), 7.36−
7.43 (m, 6H, m- and p-C6H5). 13C{1H} NMR (100 MHz, CDCl3,
room temperature): δ 126.8, 127.4, 127.9, 128.9, 129.3, 129.4, 131.5,
131.9, 136.8, 138.3, 138.7, 142.0. HRMS(APCI): C32H36 (410.20) m/z
411.2113 (M + H)+, calcd for C32H27 411.2113. (1Z,3E,5E,7Z)-4f was
reported in the literature, but it was characterized only by melting
point and elemental analysis.7
1H NMR (400 MHz, CDCl3, room temperature): δ 5.89 (AA′BB′,
3JH−H = 15.0, 6.0 Hz, JH−H = −1.0 Hz, 5JH−H = 0.0 Hz, 2H, 3- and 6-
4
3
4
5
CH), 6.45 (AA′XX′, JH−H = 15.0, 6.0 Hz, JH−H = −1.0 Hz, JH−H
=
=
0.0 Hz, 2H, 4- and 5-CH), 6.46 (s, 2H, 1- and 8-CH), 6.74 (d, 3JH−H
3
8.6 Hz, 4H, o-C6H4), 7.04 (d, JH−H = 8.6 Hz, 4H, m-C6H4), 7.06 (d,
3JH−H = 8.6 Hz, 4H, o-C6H4), 7.39 (d, JH−H = 8.6 Hz, 4H, m-C6H4).
3
13C{1H} NMR (100.5 MHz, CDCl3, room temperature): δ 128.3,
129.4, 130.4, 130.8, 130.8, 132.1, 133.0, 133.6, 134.9, 136.2, 138.3,
141.0. HRMS(APCI): C32H22Cl4 (546.05) m/z 547.0527 (M + H)+,
calcd for C32H23Cl4 547.0554.
(1Z,3E)-1,2-Diphenylhexa-1,3,5-triene (5f): 8% yield.
(1Z,3E)-1,2-Bis(4-chlorophenyl)hexa-1,3,5-triene (5h): 8% yield.
1H NMR (400 MHz, C6D6, room temperature): δ 5.05 (d, 3JH−H
=
10.0 Hz, 1H, 1-CH), 5.08 (d, 3JH−H = 17.0, 1H, 1-CH), 5.83 (dd, 3JH−H
= 15.2, 10.8 Hz, 1H, 4-CH), 6.4−6.5 (3H, 1-, 3- and 5-CH, overlapped
with signals for 4f), 6.8−6.9 (m, 2H, o-C6H5), 7.0−7.1 (m, 3H, m- and
p-C6H5), 7.1−7.2 (m, 2H, o-C6H5), 7.3−7.5 (m, 3H, m- and p-C6H5).
Reaction of 1,2-Bis(4-methylphenyl)acetylene (2g) with 1,3-
Butadiene (3). (1Z,3E,5E,7Z)-1,2,7,8-Tetrakis(4-methylphenyl)octa-
1,3,5,7-tetraene (4g): yellow powder, 41% yield.
1H NMR (400 MHz, acetone-d6, room temperature): δ 5.08 (d,
3JH−H = 10.4 Hz, 1H, 1-CH), 5.14 (d, 3JH−H = 16.0, 1H, 1-CH), 6.51(s,
1H, 1-CH), 6.9−7.6 (8H, C6H4, overlapped with signals for 4h).
Reaction of 1,2-Bis(4-trifluoromethylphenyl)acetylene (2i).
(1Z,3E,5E,7Z)-1,2,7,8-Tetrakis(4-trifluoromethylphenyl)octa-1,3,5,7-
tetraene (4i): 2% yield.
1H NMR (400 MHz, CDCl3, room temperature): δ 2.20 (s, 6H,
CH3), 2.41 (s, 6H, CH3), 5.92 (AA′BB′, 3JH−H = 15.0, 6.0 Hz, 4JH−H
=
1H NMR (400 MHz, CDCl3, room temperature): δ 5.80 (m, 2H, 3-
and 6-CH), 6.46 (m, 2H, 4- and 5-CH), 6.53 (s, 2H, 1- and 8-CH),
6.80 (d, 3JH−H = 8.8 Hz, 4H, o-C6H4), 7.20 (d, 3JH−H = 8.8 Hz, 4H, m-
C6H4), 7.22 (d, 3JH−H = 8.8 Hz, 4H, o-C6H4), 7.61 (d, 3JH−H = 8.8 Hz,
4H, m-C6H4). 19F{1H} NMR (376 MHz, C6D6, room temperature): δ
−62.6 (s, 3F, CF3), −62.4 (s, 3F, CF3).
5
−1.0 Hz, JH−H = 0.0 Hz, 2H, 3- and 6-CH), 6.43 (s, 2H, 1- and 8-
3
4
5
CH), 6.45 (AA′XX′, JH−H = 15.0, 6.0 Hz, JH−H = −1.0 Hz, JH−H
=
0.0 Hz, 2H, 4- and 5-CH), 6.73 (d, 3JH−H = 8.2 Hz, 4H, o-C6H4), 6.86
3
3
(d, JH−H = 8.2 Hz, 4H, m-C6H4), 7.01 (d, JH−H = 8.2 Hz, 4H, o-
C6H4), 7.20 (d, JH−H = 8.2 Hz, 4H, m-C6H4). 13C{1H} NMR (100.5
3
MHz, CDCl3, room temperature): δ 21.1, 21.4, 128.7, 129.2, 129.3,
129.6, 131.2, 131.5, 134.2, 135.4, 136.6, 136.8, 138.7, 141.2.
HRMS(APCI): C36H34 (466.27) m/z 467.2718 (M + H)+, calcd for
C36H35 467.2739.
Reaction of 1,2-Bis(4-chlorophenyl)acetylene (2h) with 1,3-
Butadiene (3). (1Z,3E,5E,7Z)-1,2,7,8-Tetrakis(4-chlorophenyl)octa-
1,3,5,7-tetraene (4h): yellow powder, 23% yield.
Reaction of 2a with [1,1,4,4-2H4]-1,3-Butadiene (3-d4).
[1,1,4,4-2H4]-1,3-Butadiene (3-d4, >98 atom % D) was prepared by
pyrolysis of 3-sulfolene-d4 according to the literature method.21 Into a
frozen mixture of 2a (57.0 μL, 0.265 mmol) and 1 (2.19 mg, 0.00649
mmol) in C6D6 (600 μL) was introduced 3-d4 (2.9 mL, 0.13 mmol) by
vacuum line/mercury manometer techniques. The mixture was reacted
F
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
at room temperature for 4 days to give [5,7,10,12-2H4]-4a-d4 in 11%
yield and [1,1,4,6-2H4]-5a-d4 in 26% yield (96 atom % D for 4-CD, 81
atom % D for 6-CD, 94 atom % D for 1-CD). This compound was
purified by recycle HPLC.
7.4 Hz, 1H, 2-CH2), 1.41 (t, 3JH−H = 7.4 Hz, 3H, 14-CH3), 1.70 (dqd,
3
3
2JH−H = 14.4 Hz, JH−H = 7.4, 4.6 Hz, 1H, 2-CH2), 1.78 (dd, JH−H
=
3
9.7, 8.0 Hz, 1H, 6-CH), 2.03 (quint, JH−H = 7.4 Hz, 2H, 11-CH2),
3
2.1−2.2 (m, 5H, 1H for 13-CH2 and 4H for COD), 2.29 (q, JH−H
=
7.4 Hz, 2H, 15-CH2), 2.3−2.4 (m, 3H, 1H for 13-CH2 and 2H for
COD), 2.56−2.69 (m, 2H, COD), 2.8−2.85 (m, 1H, COD), 3.10−
3.14 (m, 1H, COD), 3.18−3.22 (m, 1H, COD), 3.82−3.97 (m, 1H,
3
3
COD), 5.06 (d, JH−H = 8.0 Hz, 1H, 5-CH), 5.38 (t, JH−H = 7.4 Hz,
1H, 10-CH), 5.94 (dd, 3JH−H = 15.5, 9.7 Hz, 1H, 7-CH), 6.18 (d, 3JH−H
= 15.5 Hz, 1H, 8-CH). This compound was characterized by
spectroscopic methods.
Reaction of Complex 7 with 3-Hexyne (3d). Treatment of 6
(6.37 mg, 0.0221 mmol) with 2 equiv of 3d (5.0 μL, 0.044 mmol) in
the presence of p-xylene (2.0 μL, 0.016 mmol) as an internal standard
in C6D6 (0.6 mL) at 18 °C generated 7 in 99% yield. Further addition
of 5 equiv of 3d (12.5 μL, 0.110 mmol) to the reaction mixture gave
no additional reaction. However, 7 gradually decomposed at room
temperature and a complex mixture was obtained after 10 h.
Compound (3E,5E,7E,9E)-4d was not observed in the complex
mixture.
1H NMR (400 MHz, C6D6, room temperature): δ 0.88 (d, 3JH−H
=
3
6.4 Hz, 12H, 1-, 16-, 17- and 28-CH3), 0.93 (d, JH−H = 6.4 Hz, 12H,
3
21-, 22-, 26- and 27-CH3), 1.27 (q, JH−H = 6.8 Hz, 4H, 3- and 14-
CH2), 1.48 (m, 4H, 19- and 24-CH2), 1.53 (n, 3JH−H = 6.8 Hz, 2H, 20-
3
ASSOCIATED CONTENT
* Supporting Information
and 25-CH) 1.58 (n, JH−H = 6.8 Hz, 2H, 2- and 15-CH), 2.15 (t,
■
3
3JH−H = 7.6 Hz, 4H, 4- and 13-CH2), 2.36 (AA′XX′, JH−H = 8.7, 6.5,
S
2JH−H = −10 Hz, 4H, 18- and 23-CH2), 6.52 (s, 2H, 8- and 9-CH). 2H
NMR (61.4 MHz, C6H6, room temperature): δ 5.5 (br s, 5- and 12-
CD), 6.3 (br s, 7- and 10-CD).
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00801.
Spectroscopic and physical data (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail for M.H.: hrc@cc.tuat.ac.jp.
■
ORCID
Masafumi Hirano: 0000-0001-7835-1044
Funding
1H NMR (400 MHz, C6D6, room temperature): δ 0.91 (d, 3JH−H
=
Japan Science and Technology Agency (JST) ACT-C
(JPMJCR12Z2). Grant-in-Aid for Scientific Research (B)
17H03051.
6.3 Hz, 6H, 10- and 16-CH3), 0.93 (d, 3JH−H = 6.8 Hz, 6H, 14- and 15-
3
CH3), 1.27 (q, JH−H = 7.7 Hz, 2H, 8-CH2), 1.36−1.46 (m, 2H, 12-
CH2), 1.46−1.64 (m, 2H, 9- and 13-CH), 2.14 (t, 3JH−H = 7.7 Hz, 2H,
Notes
3
3
7-CH2), 2.31 (t, JH−H = 8.0 Hz, 2H, 11-CH2), 6.39 (d, JH−H = 10.6
3
The authors declare no competing financial interest.
Hz, 1H, 3-CH), 6.48 (d, JH−H = 10.6 Hz, 1H, 2-CH).
Reaction of Ru(η4-butadiene)(η4-1,5-COD)(NCMe) (6) with 3-
Hexyne (2d) To Give 7. [Ru(η4-butadiene)(η4-1,5-COD)(NCMe)]
(6; 13.0 mg, 0.0428 mmol) was treated with 2d (9.8 μL, 0.086 mmol)
in C6D6 at room temperature for 5 min. On the basis of p-xylene (3.0
μL, 0.024 mmol) as an internal standard, [Ru{3−6-η4-(3E,5E,7E,9E)-
4,9-diethyldodeca-3,5,7,9-tetraene}(η4-1,5-COD)(NCMe)] (7) was
obtained in 98% yield. After 2 h, to the reaction mixture was added
3 (2.44 mL, 0.109 mmol) to give (3E,5E,7E,9E)-4d in 92% yield and
the bis(η3-allylic)ruthenium(II) complex supine,prone-[Ru(1−3-η3:6−
8-η3-C8H12)(η4-1,5-COD)] (8)11 in 92% yield.
ACKNOWLEDGMENTS
■
We acknowledge financial support by the Japan Science and
Technology Agency and the Ministry of Education, Culture,
Sports, Science and Technology of Japan.
ABBREVIATIONS
COD, cyclooctadiene (C8H12)
■
REFERENCES
■
(1) Thirsk, C.; Whiting, A. J. Chem. Soc., Perkin Trans. 1 2002, 999−
1023. Petroski, R. J.; Bartet, R. J. J. Agric. Food Chem. 2007, 55, 2282−
2287.
(2) Spangler, C. W.; McCoy, R. K.; Dembek, A. A.; Sapochak, L. S.;
Gates, B. D. J. Chem. Soc., Perkin Trans. 1 1989, 151−154. Maryanoff,
B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863−927. Wadsworth, W. S., Jr.
Org. React. 1977, 25, 73−253.
(3) Kanno, K.; Igarashi, E.; Zhou, L.; Nakajima, K.; Takahashi, T. J.
Am. Chem. Soc. 2008, 130, 5624−5625.
(4) Crousse, B.; Alami, M.; Linstrumelle, G. Tetrahedron Lett. 1995,
36, 4245−4248.
(5) Suzuki, A. Angew. Chem., Int. Ed. 2011, 50, 6722−6737. Wang, Y.;
Dai, W.-M. Eur. J. Org. Chem. 2014, 2014, 323−330. Woerly, E. M.;
Cherney, A. H.; Davis, E. K.; Burke, M. D. J. Am. Chem. Soc. 2010, 132,
6941−6943. Crudden, C. M.; Ziebenhaus, C.; Rygus, J. P. G.; Ghozati,
1H NMR (400 MHz, C6D6, room temperature): δ 0.78 (dd, 3JH−H
=
=
7.4, 4.6 Hz, 1H, 3-CH), 0.83−0.88 (br, 3H, CH3CN), 0.94 (t, 3JH−H
3
7.4 Hz, 3H, 12-CH3), 1.05 (t, JH−H = 7.4 Hz, 3H, 1-CH3), 1.12 (t,
2
3
3JH−H = 7.4 Hz, 3H, 16-CH3), 1.27 (dquint, JH−H = 14.4 Hz, JH−H
=
G
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
K.; Unsworth, P. J.; Nambo, M.; Voth, S.; Hutchinson, M.; Laberge, V.
S.; Maekawa, Y.; Imao, D. Nat. Commun. 2016, 7, 11065 and
references cited therein.
(6) Shibata, K.; Satoh, T.; Miura, M. Adv. Synth. Catal. 2007, 349,
2317−2325.
(7) Pauson, P. L.; Khand, I. U. Ann. N. Y. Acad. Sci. 1977, 295, 2−14.
(8) Kiyota, S.; In, S.; Komine, N.; Hirano, M. Organometallics 2016,
35, 4033−4043.
(9) Pd-catalyzed coupling among 2 equiv of butadiene, terminal
alkyne, and Et3B giving a nonconjugated triene has been reported:
Kimura, M.; Takushima, D.; Fukushima, M.; Satomura, H.; Onodera,
G. Heterocycles 2012, 86, 171−180.
(10) Bennett, M. A.; Wang, X.-Q. J. Organomet. Chem. 1992, 428,
C17. Hirano, M.; Sakate, Y.; Inoue, H.; Arai, Y.; Komine, N.; Komiya,
S.; Wang, X.-Q.; Bennett, M. A. J. Organomet. Chem. 2012, 708−709,
46−57.
(11) Hirano, M.; Sakate, Y.; Komine, N.; Komiya, S.; Wang, X.-Q.;
Bennett, M. A. Organometallics 2011, 30, 768−777. Hirano, M.; Inoue,
H.; Okamoto, T.; Ueda, T.; Komine, N.; Komiya, S.; Wang, X.-Q.;
Bennett, M. A. New J. Chem. 2013, 37, 3433−3439.
(12) Hirano, M.; Komiya, S. Coord. Chem. Rev. 2016, 314, 182−200.
(13) Detailed kinetic and computational studies of an oxidative
coupling mechanism for diene/alkene coupling have been reported:
Hirano, M.; Ueda, T.; Komine, N.; Komiya, S.; Nakamura, S.;
Deguchi, H.; Kawauchi, S. J. Organomet. Chem. 2015, 797, 174−184.
(14) Fukumoto, H.; Mashima, K. Eur. J. Inorg. Chem. 2006, 2006,
5006−5011.
(15) Bennett, M. A.; Neumann, H.; Thomas, M.; Wang, X.-Q.;
Pertici, P.; Salvadori, P.; Vitulli, G. Organometallics 1991, 10, 3237−
3245.
(16) Kottas, G. S.; Brotin, T.; Schwab, P. F. H.; Gala, K.; Havlas, Z.;
Kirby, J. P.; Miller, J. R.; Michl, J. Organometallics 2014, 33, 3251−
3264.
(17) Wettach, H.; Jester, S. S.; Colsmann, A.; Lemmer, U.; Rehmann,
N.; Meerholz, K.; Hoger, S. Synth. Met. 2010, 160, 691−700.
̈
(18) Ravera, M.; D’Amato, R.; Guerri, A. J. Organomet. Chem. 2005,
690, 2376−2380.
(19) Liu, J.; Zhang, S.; Zhang, W.-X.; Xi, Z. Organometallics 2009, 28,
413−417.
(20) Budzelar, P. H. M. gNMR: NMR simulation program ver. 5.0.6.0;
IvorySoft, 2006.
(21) Cope, A. C.; Berchtold, G. A.; Ross, D. L. J. Am. Chem. Soc.
1961, 83, 3859−3861.
H
DOI: 10.1021/acs.organomet.7b00801
Organometallics XXXX, XXX, XXX−XXX