Palladium(0) versus nickel(0) catalysis in selective functional- grouptolerant sp3-sp3 carbon-carbon bond formations

Article abstract of DOI:10.1002/chem.200902221

We have uncovered Pd°-catalyzed intermolecular nonsymmetrical Suzuki-Miyaura-type sp³-sp³ C-C bond formations between allyl carbonates and nontoxic allyl, allenyl, or propargyl boronates. This report represents the first use of these

Full text of DOI:10.1002/chem.200902221

FULL PAPER
DOI: 10.1002/chem.200902221
Palladium(0) versus Nickel(0) Cata
ACHTUNGTRENNlUNG ysis in Selective Functional-Group-
Tolerant sp3–sp3 Carbon–Carbon Bond Formations
Emmanuel Ferrer Flegeau, Uwe Schneider, and Shu Kobayashi*[a]
¯
Abstract: We have uncovered Pd0-cata-
lyzed intermolecular nonsymmetrical
Suzuki–Miyaura-type C–C
sp3–sp3
bond formations between allyl carbo-
nates and nontoxic allyl, allenyl, or
propargyl boronates. This report repre-
sents the first use of these types of bo-
with high selectivity under remarkably
mild conditions, and various functional
groups including an aldehyde function
proved to be compatible. In addition,
several boronates were found to dis-
play very unusual reactivity patterns;
the higher reactivity of boron as ap-
posed to silicon was clearly demon-
strated as well. Finally, the inherent
problem of b-hydride elimination asso-
ciated with intermediary allyl–Pd spe-
cies was addressed by employing a
commercially available Ni0 catalyst.
Keywords: boron
· carbonates ·
nickel · palladium · Suzuki–Miyaura
reaction
ACHTUNGTRENNUNGronic esters in this particular context.
The present transformations proceeded
Introduction
metal-free catalysis.[10] However, with only few exceptions,
an excess of toxic or harmful reagents and harsh conditions
are required. In addition, a major problem in palladium ca-
Catalytic formation of carbon–carbon bonds with high effi-
ciency and selectivity is of central importance in organic
synthesis,[1] in this context catalytic sp3–sp3 C–C bond forma-
tion is particularly challenging.[2] Among allyl–allyl cross-
coupling reactions, effective methods for intramolecular cy-
AHCTUNGTREGtNNNU alysis may be the propensity of allyl–Pd intermediates to
undergo undesired b-hydride elimination. Further, the effi-
ciency of nonsymmetrical allyl–allyl coupling typically suf-
fers from homocoupling and unsatisfactory regioselectivities,
such drawbacks may account for low yields and limited
scope.
To the best of our knowledge, nontoxic allyl boronates
have been exclusively employed for nucleophilic additions
to carbonyl compounds and their derivatives.[12] Herein, we
report palladium(0)-catalyzed intermolecular sp3–sp3 C–C
cross-coupling reactions between allyl carbonates and allyl,
allenyl, or propargyl boronates, which proceed selectively
under remarkably mild conditions. In addition, we propose
a nickel(0) catalytic approach as an effective tool to address
the intrinsic problem of b-hydride elimination associated
with palladium catalysis.
ACHTUNGTRENNUNG
clizations have been reported by using allyl stannanes[3,4] or
silanes[3b] with allyl acetates[3,4] or trifluoroacetates[3b] under
palladium(0),[3] gold(I),[4] or rhodium (I)[4] catalysis. These
reactions provide access to valuable 1,5-dienes, which are
abundant in naturally occurring terpenes.[5] In addition,
these compounds have proved to be highly versatile inter-
mediates and synthetic building blocks.[6] However, the in-
termolecular nonsymmetrical sp3–sp3 allyl–allyl coupling is
significantly more challenging.[7] Only sporadic examples of
C–C bond formation between allyl metal reagents including
magnesium,[8] indium,[9] silicon,[10] or tin[11] and stoichiomet-
ric p-allyl–Pd complexes,[8,11c] allyl ethers,[10] halides and ace-
tates,[11] or carbonates[9] have been reported. These reactions
proceed without catalyst[8] or under palladium(0)[9,11] or
Results and Discussion
Based on our earlier work on InI-catalyzed allylations of car-
bonyl derivatives with allyl boronates,[13] we envisioned the
use of in situ formed p-allyl–Pd species as electrophiles in a
Tsuji–Trost-type reaction[14] with allyl indium(I) nucleo-
philes, catalytically generated from allyl boronates through
boron-to-indium transmetalation. Thus, we initially com-
bined allyl carbonate 1a and allyl boronate 3 (pin=pinacol-
[a] Dr. E. Ferrer Flegeau, Dr. U. Schneider, Prof. Dr. S. Kobayashi
Department of Chemistry, School of Science
The University of Tokyo
The HFRE Division
ERATO, Japan Science and Technology Agency (JST)
Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
Fax : (+81)3-5684-0634
E-mail: shu_kobayashi@chem.s.u-tokyo.ac.jp
Chem. Eur. J. 2009, 15, 12247 – 12254
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
12247

yl)[13] in the presence of [Pd
at room temperature with or without indium(I) iodide
(20 mol%; Table 1). Unexpectedly, however, the latter reac-
(PPh3)4] (10 mol%) in toluene
found to decrease the catalytic activity of the palladium cat-
alyst (entries 10–13), the best concentration was determined
to be 0.1m (entry 13). Importantly, compared with 1a, the
regioisomeric carbonate 2a showed both identical reactivity
and identical selectivity (entry 13 vs. 14), which stands in
sharp contrast to the use of allyl–In species, in which sub-
stantially different linear/branched ratios were observed
with 1a and 2a.[9a] Finally, it is noted that homocoupling by-
products were not detected under the present mild condi-
tions.
Table 1. Pd0-catalyzed intermolecular allyl–allyl cross-coupling with allyl
boronate 3.
We then explored the scope for allyl carbonates 1 and 2
(Table 2). Gratifyingly, various carbonates, substituted in the
a-, b-, or g-positions, relative to the leaving group, were
Table 2. Scope for Pd0-catalyzed allylation of allyl carbonates 1 and 2
with 3.
Entry Carbonate Cat.
Solvent
t
Yield
[%][a]
Ratio
4a/5a
[mol%] [m]
[h]
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
2a
10
10
–
1
1
1
1
1
1
2
2
2
2
toluene [0.1]
toluene [0.1][b]
toluene [0.1]
toluene [0.1]
n-hexane [0.1]
CH2Cl2 [0.1]
THF [0.1]
DMF [0.1]
EtOAc [0.1]
EtOAc [1]
0.1 quant.
>32:1
19:1
–
>15:1
nd[d]
nd[d]
–
2
16
2
6
6
57[c]
no reaction
quant.
quant.
89
6
2
2
12
12
12
1
trace
94
nd[d]
>32:1
11:1
13:1
16:1
>32:1
>32:1
9
94 (85[c]
68
)
10
11
12
13
14
EtOAc [0.5]
EtOAc [0.2]
EtOAc [0.1]
EtOAc [0.1]
76
90
quant.
quant.
Entry
R1
R2
R3
Yield [%][a]
Ratio 4/5
1
2
3
1b: 4-MeO-C6H4
2c: 4-Br-C6H4
2d: 4-NC-C6H4
2d: 4-NC-C6H4
2d: 4-NC-C6H4
2e: 4-F3C-C6H4
2 f: Ph
2g: 4-F3C-C6H4
1h: CO2iPr
1i: Ph
H
H
H
H
H
H
Me
Me
H
H
H
H
H
H
H
H
H
H
Ph
93
88
79
76
82
86
93
89
70[d]
85
>32:1
5.2:1
1:2
1:7
1:15
4:1
>99:1
>32:1
1:>99
–
2
1
[a] Combined 1H NMR yields and ratios for 1,5-dienes 4a and 5a were
determined by using 4-methoxytoluene as internal standard. [b] Reaction
at 808C. [c] Isolated yields for 4a and 5a after purification on silica gel
(PTLC). [d] nd=not determined.
4[b]
5[c]
6
7
8
9
10
H
tion (without indium(I)) proceeded more smoothly and pro-
vided almost exclusively the linear 1,5-diene 4a in quantita-
tive yield (as judged by 1H NMR spectroscopy) after less
than 10 min (ratio 4a/5a >32:1, entry 1). The success of
allyl boronate 3 in this Pd0-catalyzed nonsymmetrical sp3–sp3
C–C coupling under these mild conditions is striking.[15,16]
Indeed, allyl magnesium bromide,[8] allyl trimethylsilane,[10]
or allyl trifluoroborate[17,18] provided, in our hands, under
the same mild conditions after 16 h reaction time, only the
corresponding 1,2-adduct, a complex mixture, or a trace
amount of desired product, respectively.
Further experiments dealt with the optimization of several
important reaction parameters (Table 1). The palladium-cat-
alyzed transformation at 808C proved to be both less effi-
cient and less selective (entry 2), whereas the uncatalyzed
C–C cross-coupling at room temperature did not proceed at
all, even after an extended reaction time (entry 3). Signifi-
cantly, the catalyst loading could be reduced down to
1 mol% (entry 4). A solvent screening revealed that this C–
C bond formation proved to be also very fast in n-hexane,
dichloromethane, N,N-dimethylformamide, and ethyl ace-
tate, whereas the reaction in THF essentially did not take
place (entries 5–9). Higher reaction concentrations were
[a] Isolated yields of 1,5-dienes 4 and/or 5 after purification on silica gel
(PTLC). [b] Reaction with 5 mol%, 08C. [c] Reaction with 5 mol%,
À208C. [d] 1H NMR yield: 70%; isolated yield: 47% (likely due to the
volatility of the branched 1,5-diene 5h).
smoothly and selectively converted into the desired 1,5-
dienes. In addition, several important functional groups,
such as methoxy, bromo, ester, cyano, and trifluoromethyl
were found to be compatible with the mild reaction condi-
tions. Aromatic substrates provided linear products 4 with
generally excellent selectivities (entries 1, 2, and 6–8). On
the other hand, the nitrile-substituted aromatic compound
2d and the a,b-unsaturated aliphatic ester 1h led predomi-
nantly to branched 1,5-diene products 5 (entries 3–5 and 9).
It is noted that, contrary to most reported procedures,[8–11]
the present catalytic cross-coupling can be selectively per-
formed at temperatures as low as À208C (entry 5). Finally,
carbonate 1i, substituted in both the a- and g-positions, also
proved to be an excellent substrate for this transformation
(entry 10).
In addition, more challenging carbonates 1 and 2 were ex-
amined (Table 3). Unfortunately, the heteroaromatic sub-
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Chem. Eur. J. 2009, 15, 12247 – 12254

Palladium(0) Versus Nickel(0) Catalysis
FULL PAPER
Table 3. Pd0 versus Ni0: Scope and limitation for challenging carbonates.
cessful. The inherent problem of b-hydride elimination asso-
ciated with intermediary allyl–Pd species has been well stud-
ied.[19] In this context, another Group 10 element, nickel,
was previously found to enhance the rate of reductive elimi-
nation relative to b-hydride elimination.[20] We therefore de-
cided to examine commercially available [NiACTHUNTRGNE(UNG PPh3)4] as a
catalyst in this reaction system and were pleased to find that
b-hydride elimination was effectively suppressed in most
cases to selectively provide the desired 1,5-dienes 6 in 68–
90% yields (entries 6–9). Particularly noteworthy is the high
selectivity observed with the challenging carbonate 1m
(ratio 6m/7m/8m >99:4:1, entry 8 vs. 4). Finally, the diffi-
cult pyridine-derived carbonate 1j was converted under our
nickel(0) catalysis[21] into the desired linear 1,5-diene 6j in
72% yield (ratio 6j/7j >99:1, entry 10 vs. 1). The compati-
bility of this reactive heterocycle with the present catalytic
protocol is remarkable and highlights the potential of this
carbon–carbon bond formation.
We then turned our attention to the use of allyl boronates
9–12, substituted in the a-, b-, or g-positions, relative to the
boron atom, to examine the scope for boronic esters
(Table 4). In principle, four constitutional isomers can be
formed in this transformation. Remarkably, however, the
Entry R1
R2
M
Yield [%][a]
Ratio 6/7/8
1
1j: 3-pyridyl
H
H
H
Me
Pd no reaction
Pd no reaction
Pd complex mixture
Pd quant.
–
–
–
2
3
4
1k: CH2OTBS
2l: nC10H21
1m: Ph
[b]
2.3:nd:1[e]
[b]
5
1n: PhCH2CH2 CH2CH2Ph Pd complex mixture
–
6
7
1k: CH2OTBS
2l: nC10H21
1m: Ph
1n: PhCH2CH2 CH2CH2Ph Ni 90
1j: 3-pyridyl Ni 72
H
H
Me
Ni 68
Ni 74
Ni 76
2.9:1:nd[e]
1.3:1:nd[e]
>99:4:1
8[c]
9[d]
10
5.7:nd:1[e]
>99:1:–
H
[a] Isolated yields of the indicated products after purification on silica gel
(PTLC). [b] Due to the complexity of the 1H NMR spectra, a precise de-
termination of the product distribution proved to be impossible. [c] Re-
action in MeCN, RT. [d] Reaction in THF, 408C. [e] nd=not detected.
R3: in 1,3-diene byproducts of type 8, which may be derived from 1, R3
corresponds to R2, but lacks one =CH unit as part of the newly formed
C=C double bond (entries 4–5 and 8–9).
iniACTHNUGRTENUNGtial experiment by using carbonate 1a and a-methylallyl
boronate 9 under palladium(0) catalysis furnished selectively
the desired 1,5-diene 13aa (linear-a), albeit in low yield
(entry 1). As indicated in the previous study, the reaction
may be hampered by b-hydride elimination of an intermedi-
ary allyl–Pd species, which may be derived from 9 in the
present case. Nevertheless, it is noted that the exclusive
formal a-addition of allyl boronate 9 is very unusual for pal-
strate 1j (R1 =3-pyridyl, R2 =H) decomposed under the
present conditions (entry 1). Moreover, allyl carbonates for
which the allyl–Pd derivatives are prone to undergo un-
ACHTUNGTRENNUNGdesired b-hydride elimination proved to be very difficult
(entries 2–5). Typically, the re-
action did not proceed (entry 2)
or provided a complex mixture
of inseparable products, includ-
ing the undesired 1,3-diene 8
due to b-hydride elimination
(entries 3 and 5). Only carbon-
ate 1m (R1 =Ph, R2 =Me)
proved to be accessible; howev-
er, an inseparable mixture of
the desired linear 1,5-diene 6m
and byproduct 8m was ob-
tained (ratio 6m/8m 2.3:1,
entry 4). The use of alternative
solvents, such as toluene, n-
hexane, or dichloromethane re-
sulted in significantly decreased
yields for the desired coupling
product 6m, along with more
pronounced byproduct forma-
tion (1,3-diene 8m). Unfortu-
nately, our efforts to improve
these unsatisfactory results
through careful examination of
the nature and the amount of
Table 4. Pd0 versus Ni0: Scope and limitation for allyl boronates.
Entry
R1
R2
R3
R4
M
Yield [%][a]
Ratio 13/14/15/16
1[b]
2
3
1a: Ph
1a: Ph
1b: 4-MeO-C6H4
1b: 4-MeO-C6H4
1b: 4-MeO-C6H4
1a: Ph
1a: Ph
1a: Ph
1a: Ph
9: H
9: H
9: H
9: H
10: Me
11: H
11: H
12: H
12: H
H
H
H
H
Me
Me
Me
Me
H
H
H
SiMe3
SiMe3
Pd
Ni
Pd
Ni
Ni
Pd
Ni
Pd
Ni
32[d]
58
>99:nd:1:nd[c]
1:nd:1.7:nd[c]
>99:nd:1:nd[c]
1:nd:1:nd[c]
57[d]
quant.
quant.
84
4
5
H
1:nd:1:nd[c]
>99:1:–:–
6[b]
7
Me
Me
H
84
78
87
>99:1:–:–
8[e]
9
>99:nd:1:nd[c]
1:nd:>32:nd[c]
H
[a] Isolated yields of the indicated products after purification on silica gel (PTLC). [b] Reaction with 2 mol%.
[c] nd=not detected. [d] As a side reaction, presumably b-hydride elimination of an intermediary allyl–Pd spe-
cies (derived from 9) took place to form 1,3-butadiene, and aromatic olefins were formed from 1 through re-
phosphine ligands were unsuc- ductive elimination of a palladium-hydride intermediate. [e] Reaction in n-hexane.
Chem. Eur. J. 2009, 15, 12247 – 12254
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12249

S. Kobayashi et al.
ladium(0) catalysis,[17] which may imply a mechanistically
distinct process. Further, it is noteworthy that, here again,
the corresponding Ni0-catalyzed reaction led to a significant-
ly higher yield, while maintaining the exclusive linear selec-
tivity, although with a lower a/g ratio (58% yield; entry 2).
The use of substrate 1b (R1 =4-MeO-C6H4) gave better
yields, with similar selectivities to 1a, for both palladium
and nickel catalysis (entries 3 and 4 vs. entries 1 and 2). In
this context, the Ni0-catalyzed reaction of 1b with (Z)-crotyl
boronate 10 provided an identical result as to the use of a-
methylallyl boronate 9, which suggests the same reactive in-
termediate (entry 5 vs. 4). The palladium- and nickel-cata-
lyzed cross-coupling between 1a and methallyl boronate 11
proceeded smoothly with exclusive linear selectivities (en-
tries 6 and 7). Finally, the use of a-(trimethylsilyl)allyl boro-
nate 12 was found to give exclusively the unusual a-adduct
13ac (linear-a)[17] or the g-adduct 15ac (linear-g) under pal-
ladium or nickel catalysis, respectively (entry 8 vs. 9). Here
again, distinct reactive intermediates may be considered to
explain the opposite regioselective outcome. In addition,
these results underscore the higher reactivity of boron as ap-
posed to silicon.
With the aim to selectively generate 1,4-enallenes of type
23, we examined the use of 1a with g-(trimethylsilyl)pro-
pargyl boronate 22 (Scheme 1). Gratifyingly, the desired
linear-g-adduct 23a was exclusively obtained in an accepta-
ble yield. It is noted that unsaturated compounds of type 18
and 23 are potentially interesting substrates for cyclization
processes.
Scheme 1. Pd0-catalyzed selective linear allenylation of 1a with 22 (Si=
SiMe3). Nd=not detected.
Next, we examined the use of allenyl boronate 17 under
palladium catalysis (Table 5). Surprisingly, carbonate 1a was
smoothly converted with excellent linear-g-selectivity into
1,5-enyne 18a (entry 1), which reveals a very unusual reac-
tivity pattern for 17.[22] It is noted that the observed g/a
ratio upon using this boron reagent is comparable with the
result when using the corresponding indium compound,[9b]
but is substantially better than in case of the allenyl stan-
nanes.[23] Further, it is interesting that our nickel(0) condi-
tions failed to give any reaction, which suggests again that
different mechanisms are at play in palladium and nickel
catalysis (entry 2). Further selected examples for linear
propargylation of allyl carbonates with 17 showed equally
good results in favor of linear 1,5-enynes 18 (entries 3–5).
Generally, allyl boronates of type 3 smoothly react with
aldehydes, even in the absence of catalysts, to form the cor-
responding homoallyl alcohols.[12,24] This typical reactivity
pattern of allyl boronates may be explained with internal ac-
tivation of the boron atom by the carbonyl group in a
closed, six-membered cyclic chairlike transition state.[12] In
this context, the remarkable turnover frequency observed
for the present Pd0-catalyzed C–C cross-coupling between
1a and 3 (cf. Table 1, entry 1) led us to devise a competition
experiment. Thus, allyl carbonate 1a, benzaldehyde, and
allyl boronate 3 (ratio 1:1:1) were combined in ethyl acetate
at room temperature in the presence of [PdACHTUNGTRENNUNG(PPh3)4]
(10 mol%; Scheme 2). After 15 min, the reaction was stop-
Table 5. Selected examples for Pd0-catalyzed linear propargylation of 1
and 2 with 17.
Scheme 2. Pd0-catalyzed C–C cross-coupling versus 1,2-allyl boration.
Entry
R1
R2
Yield [%][a]
Ratio 18/19/20/21
1[b]
2[d]
3
4
5
1a: Ph
1a: Ph
1b: 4-MeO-C6H4
2c: 4-Br-C6H4
1i: Ph
H
H
H
H
Ph
70
50:1:2.1:nd[c]
–
1
ped and H and 11B NMR spectroscopic analysis of an ali-
no reaction
quot revealed both complete consumption of 3 and full con-
version of 1a into the desired 1,5-dienes 4a and 5a (ratio
4a/5a >32:1), whereas benzaldehyde was recovered in an
essentially quantitative yield and the corresponding homo-
allyl alcohol was not detected. This surprisingly chemoselec-
tive reaction of allyl boronate 3[25] strongly suggests the com-
70
74
50
>99:1:5:nd[c]
>50:1:1.5:nd[c]
25:–:1:–
[a] Isolated yields of enynes 18 and 19 after purification on silica gel
(PTLC). [b] Reaction with 9 mol%. [c] nd=not detected. [d] Reaction
with [NiACHTUNGTRENNUNG(PPh3)4] (10 mol%), EtOAc (RT–508C, 48 h).
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Chem. Eur. J. 2009, 15, 12247 – 12254

Palladium(0) Versus Nickel(0) Catalysis
FULL PAPER
patibility of the present Pd0-catalyzed cross-coupling with al-
dehyde functional groups, which may be particularly useful
for the synthesis of complex molecules.
dried over MgSO4. After filtration, the organic phase was concentrated
in vacuo and the residue was purified by flash column chromatography
on silica gel.
Isopropyl 1-phenylallyl carbonate (2a): Prepared from 1-phenylprop-2-
en-1-ol (500 mg, 3.73 mmol) according to general procedure A (eluant
for flash column chromatography: n-hexane/ethyl acetate 19:1). Colorless
liquid; yield: 686 mg (83%); IR (neat): n˜ =1741, 1577, 1363, 1257, 911,
Conclusion
700 cmÀ1 1H NMR (400 MHz, [D1]chloroform, 208C, TMS): d=1.27 (d,
;
J=6.0 Hz, 3H,), 1.31 (d, J=6.0 Hz, 3H), 4.87 (sept, J=6.0 Hz, 1H),
5.25–5.39 (m, 2H), 6.00–6.09 (m, 2H), 7.29–7.40 ppm (m, 5H); 13C NMR
(100 MHz, [D1]chloroform, 208C, TMS): d=21.8 (2 C), 72.1, 79.8, 117.3,
127.0, 128.3, 128.6, 135.9, 138.4, 153.9 ppm; HRMS (ESI): m/z: calcd for
C13H16NaO3: 243.0986 [M+Na]+; found: 243.0977.
We have uncovered Pd0-catalyzed intermolecular sp3–sp3 C–
C cross-coupling reactions between allyl carbonates and
allyl, allenyl, or propargyl boronates. To the best of our
knowledge, these results represent the first use of allyl boro-
nates in this context.[15,16] These overlooked transformations
proceeded with high selectivities under remarkably mild
conditions, and various functional groups including an alde-
hyde function were found to be compatible. In addition, the
intrinsic problem of b-hydride elimination related to allyl–
Pd intermediates was addressed by employing a commercial-
ly available Ni0 catalyst. Considering the facile access to
both carbonates and boronic esters, the present Group 10
metal catalysis is expected to have a significant impact on
organic synthesis. Further synthetic investigations including
asymmetric catalysis and mechanistic studies are underway
in our laboratories.
1-(4-Bromophenyl)allyl isopropyl carbonate (2c): Prepared from 1-(4-
bromophenyl)prop-2-en-1-ol (500 mg, 2.35 mmol) according to general
procedure A (eluant for flash column chromatography: n-hexane/EtOAc
19:1). Colorless liquid; yield: 542 mg (79%); IR (neat): n˜ =1741, 1640,
1258, 1095 cmÀ1 1H NMR (400 MHz, [D1]chloroform, 208C, TMS): d=
;
1.27 (d, J=6.0 Hz, 3H), 1.31 (d, J=6.0 Hz, 3H), 4.87 (sept, J=6.0 Hz,
1H), 5.26–5.36 (m, 2H,), 5.95–6.04 (m, 2H), 7.25 (d, J=8.4 Hz, 2H),
7.49 ppm (d, J=8.4 Hz, 2H); 13C NMR (100 MHz, [D1]chloroform, 208C,
TMS): d=21.7 (2C), 72.3, 79.0, 117.8, 122.3, 128.8, 131.7, 135.4, 137.4,
153.7 ppm; HRMS (ESI): m/z: calcd for C13H1579BrNaO3
[M+Na]+; found: 321.0105.
: 321.0097
+
1-(4-Cyanophenyl)allyl isopropyl carbonate (2d): Prepared from 4-(1-hy-
droxy-allyl)benzonitrile (500 mg, 3.14 mmol) according to general proce-
dure A (eluant for flash column chromatography: n-hexane/EtOAc 4:1).
Colorless liquid; yield: 552 mg (72%); IR (neat): n˜ =1742, 1644, 1257,
1097, 911, 833 cmÀ1 1H NMR (400 MHz, [D1]chloroform, 208C, TMS):
;
d=1.28 (d, J=6.4 Hz, 3H), 1.32 (d, J=6.4 Hz, 3H), 4.88 (sept, J=
6.4 Hz, 1H), 5.32–5.39 (m, 2H), 5.93–6.02 (m, 1H), 6.09 (d, J=6.0 Hz,
1H), 7.49 (d, J=8.4 Hz, 2H), 7.67 ppm (d, J=8.4 Hz, 2H); 13C NMR
(100 MHz, [D1]chloroform, 208C, TMS): d=21.7 (2 C), 72.6, 78.7, 112.0,
118.5, 118.6, 127.5, 132.4, 134.8, 143.6, 153.6 ppm; HRMS (ESI): m/z:
calcd for C14H15NNaO3+: 268.0944 [M+Na]+; found: 268.0937.
Experimental Section
General: NMR spectra were recorded on a JEOL ECX-400, JEOL
ECA-500 spectrometer, or a JEOL ECA-600 spectrometer, operating at
400, 500, or 600 MHz for 1H NMR and at 100, 125, or 150 MHz for
13C NMR spectra. Chemical shifts were reported downfield from tetrame-
thylsilane (TMS). IR spectra were measured by using a JASCO FT/IR-
610 spectrometer. HRMS were recorded by using a BRUKER DAL-
1-[4-(Trifluoromethyl)phenyl]allyl isopropyl carbonate (2e): Prepared
from 1-[4-(trifluoromethyl)phenyl]prop-2-en-1-ol (400 mg, 2.31 mmol) ac-
cording to general procedure A (eluant for flash column chromatogra-
phy: n-hexane/EtOAc 19:1). Colorless liquid; yield: 383 mg (58%); IR
TONICS BioTOF II (ESI) spectrometer or
a JEOL JMS-T100TD
(neat): n˜ =1643, 1327, 1259, 1067 cmÀ1
;
1H NMR (600 MHz,
(DART). Preparative Thin Layer Chromatography (PTLC) was carried
out by using Wakogel B-5F from WAKO. All organic solvents used were
commercially available dry solvents, which were distilled appropriately
under an argon atmosphere and stored over molecular sieves prior in an
Ar box. Allyl boronate 3,[26] a-methylallyl boronate 9,[27] (Z)-crotyl boro-
nate 10,[26] methallyl boronate 11,[28] a-(trimethylsilyl)allyl boronate 12,[29]
allenyl boronate 17,[22b] and g-(trimethylsilyl)propargyl boronate 22[30]
were prepared by slightly modified procedures of reported methods.
Allyl carbonates 1a,[31] 1b,[31] 1h,[32] 1j,[32] 1k,[32] and 1m[33] were prepared
according to the reported procedures. All other allyl carbonates 1 and 2
are new compounds and were prepared according to general proce-
dure A; their analytical data are shown below (see also copies of NMR
spectra). The Pd0- and Ni0-catalyzed carbon–carbon cross-coupling reac-
tions with allyl carbonates 1 and 2 were performed according to general
procedure B. 1,5-Dienes 4a,[34] 5a,[35] 4b,[34] 5b,[34] 4c,[11d] 5c,[11d] 4e,[34] 5e,[34]
4i,[36] 5i,[36] 6k,[37] 7k,[37] 6l,[38] 7l,[38] 6m,[39] 7m,[39] 13aa,[34] 13ab,[34] 13ba,[34]
15ba,[34] 13ac,[34] and 1,5-enynes 18a,[23] 19a,[23] and 1,4-enallene 20a[23]
are literature-known compounds. Their analyses are in full agreement
with the reported data (see also copies of NMR spectra). The analytical
data for new C–C cross-coupling products are shown below (see also
copies of NMR spectra).
[D1]chloroform, 208C, TMS): d=1.27 (d, J=6.2 Hz, 3H), 1.32 (d, J=
6.2 Hz, 3H), 4.88 (sept, J=6.2 Hz, 1H), 5.30–5.37 (m, 2H), 5.98–6.03 (m,
1H), 6.11 (d, J=6.2 Hz, 1H), 7.50 (d, J=7.6 Hz, 2H), 7.63 ppm (d, J=
7.6 Hz, 2H); 13C NMR (150 MHz, [D1]chloroform, 208C, TMS): d=21.7
(2C), 72.5, 78.9, 118.2, 124.0 (q, J=272.2 Hz), 125.6 (d, J=4.4 Hz), 127.2,
130.4 (q, J=33.2 Hz), 135.3, 142.5, 153.7 ppm; HRMS (ESI): m/z: calcd
for C14H15F3NaO3+: 311.0866 [M+Na]+; found: 311.0720.
Isopropyl 2-methyl-1-phenylallyl carbonate (2 f): Prepared from 2-
methyl-1-phenyl-prop-2-en-1-ol (500 mg, 3.38 mmol) according to general
procedure A (eluant for flash column chromatography: n-hexane/EtOAc
15–16:1). Colorless liquid; yield: 619 mg (78%); IR (neat): n˜ =1740,
1
1653, 1455, 1376, 1115, 1087, 914, 790, 762, 699 cmÀ1; H NMR (400 MHz,
[D1]chloroform, 208C, TMS): d=1.20 (d, J=6.4 Hz, 3H), 1.23 (d, J=
6.4 Hz, 3H), 1.58 (s, 3H), 4.80 (sept, J=6.4 Hz, 1H), 4.93 (s, 1H), 5.10 (s,
1H), 5.91 (s, 1H, s), 7.21–7.32 ppm (m, 5H); 13C NMR (100 MHz,
[D1]chloroform, 208C, TMS): d=18.6, 21.7, 21.8, 72.1, 81.9, 112.7, 126.9,
128.1, 128.4, 137.9, 142.8, 153.9 ppm; HRMS (ESI): m/z: calcd for
C14H18NaO3+: 257.1148 [M+Na]+; found: 257.1145.
1-[4-(Trifluoromethyl)phenyl]-2-methallyl isopropyl carbonate (2g): Pre-
pared
from
1-[4-(trifluoromethyl)phenyl]-2-methylprop-2-en-1-ol
(400 mg, 1.85 mmol) according to general procedure A (eluant for flash
column chromatography: n-hexane/EtOAc 15–16:1). Colorless liquid;
yield: 395 mg (71%); IR (neat): n˜ =1637, 1327, 1260, 1125, 1067,
General procedure A (preparation of allyl carbonates): Isopropyl chloro-
formate (1.0m in toluene, 3 equiv) was slowly added to a solution of the
corresponding allyl alcohol (1 equiv), pyridine (2 equiv), and 4-(dimeth-
ylamino)pyridine (cat.) in dry THF at 08C under an Ar atmosphere. The
788 cmÀ1 1H NMR (600 MHz, [D1]chloroform, 208C, TMS): d=1.29 (d,
;
reaction mixture was then stirred at room temperature for 24–48 h,
before quenching with aqueous HCl (1m) and dilution with diethyl ether.
After phase separation, the organic phase was successively washed with
aqueous HCl (1m; twice), aqueous NaHCO3 (sat), and brine and was
J=6.0 Hz, 3H), 1.32 (d, J=6.0 Hz, 3H), 1.65 (s, 3H), 4.89 (sept, J=
6.0 Hz, 1H), 5.04 (s, 1H), 5.20 (s, 1H), 6.04 (s, 1H), 7.49 (d, J=8.0 Hz,
2H), 7.62 ppm (d, J=8.0 Hz, 2H); 13C NMR (150 MHz, [D1]chloroform,
208C, TMS): d=18.3, 21.7 (2C), 71.4, 72.4, 81.2, 114.0, 124.0 (q, J=
Chem. Eur. J. 2009, 15, 12247 – 12254
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12251

S. Kobayashi et al.
271.7 Hz), 125.3–125.4 (m), 127.1, 130.3 (q, J=31.8 Hz), 142.1,
procedure B with [Pd
ature for 3 h (eluant for PTLC: n-hexane). Colorless liquid; yield: 93%;
IR (neat): n˜ =1640, 1444, 912, 740, 698 cmÀ1 1H NMR (600 MHz,
ACHTUNGTRNEN(UNG PPh3)4] (2 mol%) in ethyl acetate at room temper-
+
153.8 ppm; HRMS (ESI): m/z: calcd for C15H17F3NaO3
: 325.1022
[M+Na]+; found: 325.1028.
;
[D1]chloroform, 208C, TMS): d=1.86 (d, J=0.8 Hz, 3H), 2.23–2.29 (m,
4H), 4.97–5.09 (m, 2H), 5.81–5.91 (m, 1H), 6.28 (s, 1H), 7.16–7.33 ppm
(m, 5H); 13C NMR (150 MHz, [D1]chloroform, 208C, TMS): d=17.8,
Isopropyl (E)-1,3-diphenylallyl carbonate (1i): Prepared from (E)-1,3-di-
phenylprop-2-en-1-ol (4.84 g, 23.0 mmol) according to general proce-
ACHTUNGTRENNUNG
32.3, 40.0, 114.6, 125.1, 125.8, 128.0, 128.8, 138.3, 138.4, 138.5 ppm;
+
HRMS (ESI): m/z: calcd for C13H16
:
172.1252 [M+H]+; found:
;
172.1240.
d=1.28 (d, J=6.0 Hz, 3H), 1.31 (d, J=6.0 Hz, 3H), 4.88 (sept, J=
6.0 Hz, 1H), 6.25 (d, J=7.0 Hz, 1H), 6.34–6.40 (m, 1H), 6.68 (d, J=
16.0 Hz, 1H), 7.22–7.45 ppm (m, 10H); 13C NMR (100 MHz,
[D1]chloroform, 208C, TMS): d=21.8 (2C), 72.2, 79.8, 126.7, 126.9, 127.0,
128.1, 128.3, 128.5, 128.6, 132.8, 136.0, 138.7, 153.9 ppm; HRMS (ESI):
m/z: calcd for C19H20NaO3+: 319.1305 [M<M+>Na]+; found: 319.1326.
1-(Trifluoromethyl)-4-[(E)-2-methylhexa-1,5-dienyl]benzene (4g)/1-(tri-
fluoromethyl)-4-(2-methylhexa-1,5-dien-3-yl)benzene (5g; cf. Table 2,
entry 8): Prepared from allyl carbonate 2g and allyl boronate 3 according
to general procedure B with [PdACHTNUGTRENUNG(PPh3)4] (2 mol%) in ethyl acetate at
room temperature for 3 h (eluant for PTLC: n-hexane). Colorless liquid;
yield: 89%; ratio 4g/5g >32:1); IR (neat): n˜ =1642, 1325, 1123,
Isopropyl tridec-1-en-3-yl carbonate (2l): Prepared from tridec-1-en-3-ol
(700 mg, 3.80 mmol) according to general procedure A (eluant for flash
column chromatography: n-hexane/EtOAc 19:1). Colorless liquid; yield:
1068 cmÀ1 1H NMR (600 MHz, [D1]chloroform, 208C, TMS): d=1.86 (d,
;
J=1.6 Hz, 3H), 2.22–2.32 (m, 4H), 4.99–5.10 (m, 2H), 5.76–5.93 (m,
1H), 6.29 (s, 1H), 7.32 (d, J=8.4 Hz, 2H), 7.55 ppm (d, J=8.4 Hz, 2H);
13C NMR (150 MHz, [D1]chloroform, 208C, TMS): d=111.4, 114.9 (2C),
116.4, 121.7, 122.6, 122.7, 123.5, 124.9 (4C), 125.0 (3C), 125.1, 125.2,
125.3, 125.7, 127.4, 127.5, 127.7, 127.9, 128.1, 128.2, 128.7, 128.8, 129.0,
130.1, 135.9, 137.8, 138.0 (2C), 138.9 (2C), 140.8, 141.0, 142.0, 142.1 ppm;
HRMS: mass spectroscopic analyses (DART, ESI, FAB, MALDI) failed
to give the desired molecular signal, resulting only in fragmentation; in
addition, preparation of a sample for elemental analysis failed due to the
volatility of these compounds.
933 mg (86%); IR (neat): n˜ =1740, 1640, 1261, 1100 cmÀ1 1H NMR
;
(400 MHz, [D1]chloroform, 208C, TMS): d=0.89–0.86 (m, 3H), 1.21–1.36
(m, 25H), 1.55–1.74 (m, 3H), 4.87, (sept, J=6.0 Hz, 1H), 5.00–5.05 (m,
1H), 5.18–5.31 (m, 2H), 5.75–5.84 ppm (m, 1H); 13C NMR (100 MHz,
[D1]chloroform, 208C, TMS): d=14.1, 21.7, 21.8, 22.7, 25.0, 29.3, 29.4,
29.5, 29.6, 31.9, 34.2, 71.6, 78.7, 117.2, 136.2, 154.1 ppm; HRMS (ESI):
m/z: calcd for C17H32O3Na+: 307.2238 [M+Na]+; found: 307.2237.
Isopropyl (E)-4-phenylbut-3-en-2-yl carbonate (1m): Prepared from (E)-
phenylbut-3-en-2-ol (10.3 g, 64.4 mmol) according to general procedure A
(eluant for flash column chromatography: n-hexane/EtOAc 19:1). Color-
less liquid; yield: 14.4 g (95%); IR (neat): n˜ =1735, 1648, 1262, 1113,
Isopropyl 2-vinylpent-4-enoate (5h; cf. Table 2, entry 9): Prepared from
allyl carbonate 1h and allyl boronate 3 according to general procedure B
with [PdACHTNUGTRNEUG(N PPh3)4] (2 mol%) in ethyl acetate at room temperature for 4 h
1036, 792, 749, 693 cmÀ1 1H NMR (400 MHz, [D1]chloroform, 208C,
;
TMS): d=1.31 (t, J=6.4 Hz, 3H), 1.47 (d, J 6.4 Hz, 3H), 4.88 (sept, J=
6.4 Hz, 1H), 5.33–5.39 (m, 1H), 6.18–6.23 (m, 1H), 6.65 (d, J=16 Hz,
1H), 7.23–7.40 ppm (m, 5H); 13C NMR (100 MHz, [D1]chloroform, 208C,
(eluant for PTLC: n-hexane/EtOAc 9:1). Colorless liquid; NMR yield:
70% (use of 4-methoxytoluene (0.1 equiv) as internal standard), isolated
yield: 42% (due to volatility of 5h); IR (neat): n˜ =1639 cmÀ1 1H NMR
;
TMS): d=20.5, 21.8 (2C), 71.7, 74.8, 126.6, 128.0, 128.2, 128.3, 128.4,
(600 MHz, [D1]chloroform, 208C, TMS): d=1.20 (d, J=6.4 Hz, 3H), 1.23
(d, J=6.4 Hz, 3H), 2.30–2.34 (m, 1H), 2.47–2.52 (m, 1H), 3.04–3.07 (m,
1H), 4.98–5.09 (m, 3H), 5.13–5.16 (m, 2H), 5.71–5.78 (m, 1H), 5.80–
5.86 ppm (m, 1H); 13C NMR (150 MHz, [D1]chloroform, 208C, TMS):
d=21.7, 21.8, 36.4, 50.1, 67.9, 116.9, 117.1, 135.0, 135.7, 172.9 ppm;
HRMS (ESI): m/z: calcd for C10H16NaO2+: 191.1043 [M+Na]+; found:
191.1047.
+
128.5, 132.0, 136.2, 153.9 ppm; HRMS (ESI): m/z: calcd for C14H18NaO3
:
257.1148 [M+Na]+; found: 257.1154.
General procedure B (Pd0- or Ni0-catalyzed sp3–sp3 C–C cross-coupling
reactions): The corresponding catalyst [Pd(PPh3)4] (1–10 mol%) or [Ni-
(PPh3)4] (5–10 mol%) and the indicated solvent (2 mL, 0.1m) were
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
added to an oven-dried 5 mL microwave-type vial with a magnetic stir-
ring bar in an Ar box. Under an Ar atmosphere (outside the Ar box),
the corresponding allyl carbonate 1 or 2 (0.20 mmol, 1.0 equiv) was intro-
duced into the vial at room temperature, before setting the indicated re-
action temperature. The corresponding boronate 3, 9–12, 17, or 22
(0.24 mmol, 1.2 equiv) was added dropwise to the stirred mixture and the
reaction was monitored by TLC on silica gel until complete conversion
of 1 or 2. The reaction mixture was filtered through Celite (when using
17 or 22) and concentrated in vacuo. The residue was purified by PTLC
on silica gel to afford the corresponding cross-coupling products 4–7, 13–
15, 18–20, or 23.
3-[(E)-Hexa-1,5-dienyl]pyridine (6j; cf. Table 3, entry 10): Prepared from
allyl carbonate 1j and allyl boronate 3 according to general procedure B
with [NiACHTNUGTRNEUG(N PPh3)4] (10 mol%) in THF at 408C for 4 h (eluant for PTLC: di-
ethyl ether). Additional purification: a solution of the obtained com-
pound in diethyl ether was successively washed with aqueous NaOH (1m,
twice) and brine. The organic phase was dried over MgSO4, filtered, and
concentrated in vacuo to afford the pure product 6j. Colorless liquid;
yield: 72%; IR (neat): n˜ =1640, 1444, 912, 740, 698 cmÀ1 1H NMR
;
(400 MHz, [D1]chloroform, 208C, TMS): d=2.22–2.28 (m, 2H), 2.38–2.31
(m, 2H), 5.00–5.10 (m, 2H), 5.81–5.91 (m, 1H), 6.26–6.41 (m, 2H), 7.20–
7.23 (m, 1H), 7.64–7.67 (m, 1H), 8.42–8.43 (m, 1H), 8.55–8.56 ppm (m,
1H); 13C NMR (100 MHz, [D1]chloroform, 208C, TMS): d=32.4, 33.2,
115.2, 123.3, 126.7, 132.4, 132.6, 133.2, 137.7, 147.9, 148.0 ppm; HRMS
(ESI): m/z: calcd for C11H14N+: 160.1121 [M+H]+; found: 160.1113.
4-[(E)-Hexa-1,5-dienyl]benzonitrile (4d)/4-(hexa-1,5-dien-3-yl)benzoni-
trile (5d; cf. Table 2, entry 5): Prepared from allyl carbonate 2d and allyl
boronate 3 according to general procedure B with [PdACTHNUTRGNE(UNG PPh3)4] (5 mol%)
in ethyl acetate at À208C for 4 h (eluant for PTLC: n-hexane/EtOAc
4:1). Colorless liquid; yield: 82%; ratio 4d/5d 1:15; IR (neat): n˜ =2227,
1639, 1606, 1503, 1412, 993, 917, 836, 560 cmÀ1 1H NMR (600 MHz,
;
(E)-5-Allyl-1,7-diphenylhept-3-ene (6n)/
diene (8n; cf. Table 3, entry 9): Prepared from allyl carbonate 1n and
allyl boronate according to general procedure B with [Ni(PPh3)4]
ACHTUNGTRNE(NUNG 2E,4E)-1,7-diphenylhepta-2,4-
[D1]chloroform, 208C, TMS): d=2.23–2.27 (m, 2H; 4d), 2.34–2.37 (m,
2H; 4d), 2.43–2.55 (m, 2H; 5d), 3.41–3.44 (m, 1H; 5d), 4.98–5.12 (m,
2H; 4d; m, 4H; 5d), 5.65–5.70 (m, 1H; 5d), 5.80–5.95 (m, 2H; 4d; m,
1H; 5d), 6.35–6.45 (m, 1H; 4d), 7.26–7.30 (m, 2H; 4d; m, 2H; 5d), 7.41
(d, J=8.2 Hz, 2H; 4d), 7.59 ppm (d, J=8.2 Hz, 2H; 5d); 13C NMR
(150 MHz, [D1]chloroform, 208C, TMS): d=32.4 (4d), 33.1 (4d), 39.3
(5d), 49.5 (5d), 110.0 (4d), 110.1 (5d), 115.3 (4d), 115.6 (5d), 116.9 (5d),
118.9 (5d), 119.1 (4d), 126.4 (4d), 128.6 (5d), 128.9 (4d), 132.2 (5d),
132.3 (4d), 134.4 (4d), 135.4 (5d), 137.5 (4d), 140.0 (5d), 142.1 (4d),
149.2 ppm (5d); HRMS (ESI): m/z: calcd for C13H14N+: 184.1121
[M+H]+; found: 184.1126.
3
ACHTUNGTRENNUNG
(10 mol%) in THF at 408C for 21 h (eluant for PTLC: n-hexane). Color-
less liquid; yield: 90%; ratio 6n/8n 5.7:1; IR (neat): n˜ =1638, 1495, 1454,
910, 745, 698 cmÀ1; H NMR (500 MHz, [D1]chloroform, 208C, TMS): d=
1
1.42–1.50 (m, 1H), 1.65–1.72 (m, 1H), 2.00–2.11 (m, 3H), 2.33–2.41 (m,
2H), 2.41–2.47 (m, 1H), 2.54–2.60 (m, 1H), 2.68–2.71 (m, 2H), 4.94–4.97
(m, 2H), 5.20–5.24 (m, 1H), 5.40–5.46 (m, 1H), 5.64–5.73 (m, 1H), 7.11–
7.20 (m, 5H), 7.23–7.28 ppm (m, 5H); 13C NMR (125 MHz,
[D1]chloroform, 208C, TMS): d=33.4, 34.4, 36.1, 36.4, 40.0, 42.1, 115.6,
125.5, 125.7, 128.2 (2 C), 128.4, 128.5, 130.0, 134.5, 137.1, 142.0,
142.8 ppm; HRMS: mass spectroscopic analyses (DART, ESI, FAB,
MALDI) failed to give the desired molecular signal, resulting only in
1-[(E)-2-Methylhexa-1,5-dienyl]benzene (4 f; cf. Table 2, entry 7): Pre-
pared from allyl carbonate 2 f and allyl boronate 3 according to general
12252
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 12247 – 12254

Palladium(0) Versus Nickel(0) Catalysis
FULL PAPER
fragmentation; in addition, preparation of a sample for elemental analy-
sis failed, because the two compounds could not be fully separated.
HRMS (ESI): m/z: calcd for C15H21Si+: 229.1407 [M+H]+; found:
229.1407.
Competition experiment: Pd0-catalzyed C–C coupling versus 1,2-allyl bo-
ration: [PdACHTNUGTRNEUNG(PPh3)4] (10 mol%), ethyl acetate (2 mL, 0.1m), dibenzyl ether
1-[(E)-Hex-1-en-5-ynyl]-4-methoxybenzene (18b)/1-(hex-1-en-5-yn-3-yl)-
4-metho-xybenzene (19b)/1-[(E)-hexa-1,4,5-trienyl]-4-methoxybenzene
(20b; cf. Table 5, entry 3): Prepared from allyl carbonate 1b and allenyl
(0.10 mmol, 0.50 equiv), allyl carbonate 1a (0.20 mmol, 1.0 equiv), and
benzaldehyde (0.20 mmol, 1.0 equiv) were added successively to an oven-
dried 5 mL microwave-type vial with a magnetic stirring bar in an Ar
box. Allyl boronate 3 (0.20 mmol, 1.0 equiv) was then added in one por-
tion to the vigorously stirred reaction mixture at room temperature.
After 15 min, TLC analysis showed complete conversion of allyl carbon-
ate 1a. The reaction mixture was quenched with aqueous HCl (1m,
1 drop) and an aliquot of the mixture (100 mL) was analyzed in CDCl3
(500 mL). 1H NMR spectral analysis showed full conversion of allyl car-
bonate 1a into the desired 1,5-dienes 4a and 5a (ratio 4a/5a >32:1;
quantitative NMR yield based on dibenzyl ether as internal standard). In
addition, benzaldehyde was recovered in essentially quantitative yield
and the potentially formed homoallylic alcohol or any related allyl borat-
ed materials were not detected.
boronate 17 according to general procedure B with [PdACHTNUTRGNE(UNG PPh3)4]
(10 mol%) in ethyl acetate at room temperature for 3 h (eluant for
PTLC: n-hexane/EtOAc 9:1). Colorless liquid; yield: 70%; ratio 18b/
19b/20b >99:1:5; 1,5-enynes 18b (linear-g) and 19b (branched-g) could
be separated from the minor byproduct 20b (linear-a); IR (neat): n˜ =
1642, 1252, 1030, 804 cmÀ1 1H NMR (500 MHz, [D1]chloroform, 208C,
;
TMS): d=1.98–1.99 (m, 1H), 2.32–2.36 (m, 2H), 2.40–2.44 (m, 2H), 3.79
(s, 3H), 6.08–6.14 (m, 1H), 6.39 (d, J=15.9 Hz, 1H), 6.84 (d, J=9.1 Hz,
2H), 7.29 ppm (d, J=9.1 Hz, 2H); 13C NMR (125 MHz, [D1]chloroform,
208C, TMS): d=18.8, 32.0, 55.2, 68.7, 83.9, 113.9, 126.2, 127.2, 130.2,
130.4, 158.8 ppm; HRMS: mass spectroscopic analyses (DART, ESI,
FAB, MALDI) failed to give the desired molecular signal, resulting only
in fragmentation; elemental analysis: calcd (%) for C13H14O: C 83.83, H
7.58; found: C 83.41, H 7.76.
1-Bromo[(E)-hex-1-en-5-ynyl]benzene (18c)/1-bromo-4-(hex-1-en-5-yn-3-
yl)benzene (19c)/1-bromo-4-[(E)-hexa-1,4,5-trienyl]benzene (20c; cf.
Table 5, entry 4): Prepared from allyl carbonate 2c and allenyl boronate
Acknowledgements
17 according to general procedure B with [PdACHTNURTGNEUNG(PPh3)4] (10 mol%) in ethyl
This work was partially supported by a Grant-in-Aid for Scientific Re-
search from the Japan Society for the Promotion of Science (JSPS) .
acetate at room temperature for 2 h (eluant for PTLC: n-hexane/EtOAc
9:1). Colorless liquid; yield: 74; ratio 18c/19c/20c >50:1:1.5; 1,5-enynes
18c (linear-g) and 19c (branched-g) could be separated from the minor
byproduct 20c (linear-a); IR (neat): n˜ =1643, 1487, 1072, 798, 639 cmÀ1
;
[1] a) Transition Metal Reagents and Catalysts: Innovations in Organic
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1H NMR (500 MHz, [D1]chloroform, 208C, TMS): d=1.95–2.01 (m, 1H),
2.34–2.37 (m, 2H), 2.41–2.45 (m, 2H), 6.22–6.28 (m, 1H), 6.39 (d, J=
15.9 Hz, 1H), 7.21 (d, J=8.5 Hz, 2H), 7.41 ppm (d, J=8.5 Hz, 2H);
13C NMR (125 MHz, [D1]chloroform, 208C, TMS): d=18.6, 31.9, 69.0,
83.6, 120.8, 127.6, 129.25, 130.0, 131.6, 136.3 ppm; HRMS: mass spectro-
scopic analyses (DART, ESI, FAB, MALDI) failed to give the desired
molecular signal, resulting only in fragmentation; elemental analysis:
calcd (%) for C12H11Br: C 61.30, H 4.72; found: C 61.59, H 4.85.
(E)-1,3-Diphenylhex-1-en-5-yne (18i)/(E)-4,6-diphenylhexa-1,2,5-triene
(20i; cf. Table 5, entry 5): Prepared from allyl carbonate 1i and allenyl
boronate 17 according to general procedure B with [PdACHTNUTRGNE(UNG PPh3)4]
(10 mol%) in ethyl acetate at room temperature for 3 h (eluant for
PTLC: n-hexane). Colorless liquid; yield: 50%; ratio 18i/20i 25:1; the
desired 1,5-enyne 18i (g) could be separated from the minor byproduct
20i (a); IR (neat): n=1645, 1494, 744, 695 cmÀ1 1H NMR (400 MHz,
;
[D1]chloroform, 208C, TMS): d=1.98–1.99 (m, 1H), 2.68–2.71 (m, 2H)
3.69–3.73 (m, 1H), 6.39–6.49 (m, 2H), 7.18–7.39 ppm (m, 10H);
13C NMR (100 MHz, [D1]chloroform, 208C, TMS): d=25.5, 47.6, 70.2,
82.3, 126.3, 126.8, 127.3, 127.7, 128.5 (2 C), 130.6, 131.7, 137.1, 142.6 ppm;
HRMS: mass spectroscopic analyses (DART, ESI, FAB, MALDI) failed
to give the desired molecular signal, resulting only in fragmentation; ele-
mental analysis: calcd (%) for C18H16: C 93.06, H 6.94; found: C 92.90, H
7.09.
Trimethyl[(E)-6-phenylhexa-1,2,5-trien-3-yl]silane (23a; cf. Scheme 1):
Prepared from allyl carbonate 1a and g-(trimethylsilyl)propargyl boro-
nate 22 according to general procedure B with [PdACTHNUTRGNE(UNG PPh3)4] (10 mol%) in
toluene at room temperature for 8 h (eluant for PTLC: n-hexane). Color-
less liquid; yield: 46%; the desired 1,4-enallene 23a (linear-g) was ob-
tained as a single isomer, but exists as a mixture of two rotamers in
CDCl3 at 408C (ratio major/minor 24:1); IR (neat): n˜ =1928, 1645, 1249,
962, 840, 745, 693 cmÀ1 1H NMR (600 MHz, [D1]chloroform, 408C,
;
TMS): d=0.02 (s, 9H; minor), 0.14 (s, 9H; major), 2.91–2.93 (m, 2H;
major), 2.98–2.99 (m, 2H; minor), 4.39 (t, J=2.8 Hz, 2H; major), 4.46 (t,
J=2.8 Hz, 2H; minor), 6.26 (dt, J=6.8, 15.8 Hz, 1H; major + minor),
6.43 (d, J=15.8 Hz, 1H; major + minor), 7.19–7.21 (m, 1H; major +
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Angew. Chem. Int. Ed. 2001, 40, 3208.
minor), 7.28–7.31 (m, 2H; major
+ minor), 7.35–7.36 ppm (m, 2H;
major + minor); 13C NMR (150 MHz, [D1]chloroform, 408C, TMS): d=
À1.53 (3C; major), 0.03 (3C; minor), 33.1 (major), 69.1 (major), 70.0
(minor), 86.3 (minor), 93.4 (major), 126.1 (major), 126.9 (major), 128.5
(major), 129.1 (major), 130.5 (major), 137.8 (major), 209.4 ppm (major);
Chem. Eur. J. 2009, 15, 12247 – 12254
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12253

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indium species (THF, reflux, 24 h), in situ generated from allyl bro-
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2ACTHNUTRGNE(UNG pin)2
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[22] Typically, allenyl boronate 17 has been shown to display other reac-
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Received: August 10, 2009
Published online: October 15, 2009
12254
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ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 12247 – 12254