Palladium-catalyzed double-bond migration of unsaturated hydrocarbons accelerated by tantalum chloride

Article abstract of DOI:10.1039/c9cc00223e

The operationally simple palladium-catalyzed double-bond migration without heteroatom-containing coordinating functional groups is described. Addition of TaCl₅ as a second catalyst greatly enhanced the migration efficiency to provide β-alkylsty

Full text of DOI:10.1039/c9cc00223e

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Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
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DOI: 10.1039/C9CC00223E
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Palladium-Catalyzed Double-Bond Migration of Unsaturated
Hydrocarbons Accelerated by Tantalum Chloride
Masahito Murai,a,* Kengo Nishimura,a and Kazuhiko Takaia,*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
double bonds migrating toward heteroatom-containing functional
groups.2 Far less attention has been focused on catalytic double-
bond migration over alkyl chains without the aid of such functional
groups. Most of the previously reported this type of migration
proceeded over only one-carbon or gave a mixture of isomers, even
though the additional transposition would provide more
thermodynamically stable olefins (Scheme 1(b)).2c,d,5 An exception is
Kochi and Kakiuchi’s work on the cycloisomerization of 1,n-dienes
through chain-walking of terminal double bonds with palladium
hydride species followed by hydrogenation (Scheme 1(c)).4d,e,g With
stoichiometric amounts of Schwartz’s reagent, Cp2Zr(H)Cl,
generation of alkylzirconium species via migration of internal
olefinic double bonds of hydrocarbons has been also
accomplished.6 Another drawback for long-range migration
methods is the need for suitably functionalized phosphorus- or
nitrogen-based ligands, which are often commercially unavailable
(Scheme 1). Thus, operationally simple and selective migration
using commercially available catalysts under mild conditions is of
significant interest. The present report describes the palladium-
catalyzed double-bond migration of alkenes7 without the aid of
heteroatom-containing directing groups, which could be promoted
by the addition of a catalytic amount of second metal chlorides.8
Note that benzene rings were chosen as terminators of migration in
this study to evaluate the migration efficiency fairly without any
effects of heteroatoms.
The operationally simple palladium-catalyzed double-bond
migration without heteroatom-containing coordinating functional
groups is described. Addition of TaCl5 as a second catalyst greatly
enhanced the migration efficiency to provide -alkylstyrenes
through migration of up to a five-carbon chain. Both catalysts
were commercially available, and reaction occurred without
external ligands under neutral conditions. The reaction proceeded
via generation of -allyl palladium species, which enabled
chemoselective double-bond migration of hydrocarbons in the
presence of allylethers. Remote functionalization through double-
bond migration was also demonstrated using FeCl3 as a second
catalyst.
Functionalization of inexpensive and abundant unsaturated
hydrocarbon feedstocks for sustainable production of organic
chemicals is an important challenge.1 A well-established reliable
strategy involves preinstallation of heteroatom-containing directing
groups into a hydrocarbon skeleton to improve overall reaction
efficiency of functionalization and avoid siteselectivity issues. The
present study describes double-bond migration of hydrocarbons
without the aid of heteroatom-containing coordinating functional
groups as a strategy to increase the value of hydrocarbon resources.
This is a fundamental, but important reaction offering a convenient,
atom-efficient, and redox-neutral approach to synthesize
complicated olefins from readily available terminal olefins.2
Since the pioneering work by Shimizu on the isomerization of
allylbenzene to -methylstyrene in the presence of Ziegler-Natta
catalyst,3 a wide variety of migrations using transition metal
complexes, acids, and bases as promoters have been reported.
These efforts have increased efficiency of migration significantly,
confirmed by a recent study on the long-range migration of olefinic
double bonds (Scheme 1(a)).4 In contrast to the work by Shimizu,
alkenyl alcohols and amines have been used as substrates in most
of these studies to promote transposition reactions, with the
Cp
PF6
Ru complex
OH
O
Ru
N
PHiPr2
(30 mol%)
MeCN
tBu
(a)
H
H
28
28
acetone-d6
N
Me
81%
70 ºC, 3 d
Ru complex
[PdBr(PtBu3)]2
(5 mol%)
(b)
+
Ph
Ph
Ph
toluene, 80 ºC, 6 h
80%
20%
(phen)PdMeCl (2.5 mol%)
NaB[3,5-(CF3)2C6H3]4 (3 mol%)
MeO2C
MeO2C
CH2ClCH2Cl, 25 ºC , 24 h
8
a. Division of Applied Chemistry, Graduate School of Natural Science and
Technology, and Research Institute for Interdisciplinary Science, Okayama
University, 3-1-1 Tsushimanaka, Kita-ku, Okayama 700-8530, Japan.
E-mail: masahito.murai@okayama-u.ac.jp
†Electronic Supplementary Information (ESI) available: Experimental procedures,
spectroscopic data for all new compounds, and copies of 1H and 13C NMR spectra.
See DOI: 10.1039/x0xx00000x
H2 (1 atm), PtO2
MeO2C
(c)
MeO2C
75% (d.r. = 94 / 6)
MeOH, 25 ºC
8
Scheme 1. Previous double-bond migration of alkenes
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The present study was prompted by the unexpected finding of Heteroaromatic substituents, such as a benzo[b]thieVnieywl gArrtoiculepO,ndlinide
double-bond migration of 1-(tert-butyl)-4-(4-penten-1-yl)benzene not affect the migration efficiency (entry 5). Migration of the
DOI: 10.1039/C9CC00223E
double bond of alkenes with alkyl sidechains 1f and 1g proceeded
smoothly to yield 2f and 2g in good yields (entries 6 and 7).
Formation of a small amount of 2f’ implies that current migration
1a in the presence of PdCl2. -Alkylstyrene 2a, formed by the
migration over three-carbons, was obtained in 76% yield (E / Z =
>99 / 1) together with its constitutional isomer, 1-(tert-butyl)-4-(3-
penten-1-yl)benzene 4a, in 22% yield (E / Z = 70 / 30) at 60 °C (Table using TaCl5 proceeded via the generation of -allyl palladium
1, entry 1). Although palladium catalysts are known to be effective species (vide infra). Internal alkenes (E)-4a was also applicable to
for double-bond transposition,7 this was a surprising result because the reaction, and its stereochemistry did not affect the efficiency of
previous processes were limited to one-carbon migration and/or migration (entry 8). However, migration of internal alkene 1h,
required heteroatom-containing functional groups to facilitate the which has two longer alkyl chains attached to the double bond, was
migration, except for the reaction reported by Kochi and sluggish, and the expected 2h was obtained in 68% yield along with
Kakiuchi.4d,e,g Formation of 2a was observed with PdCl2 and PdBr2, a mixture of other internal olefin isomers (entry 9). Higher catalyst
and other metal complexes did not show any catalytic activity at loading was essential for migration of 1i over a five-carbon chain to
60 °C (Table 1, entries 2-5). Inspired by the Shimizu’s work using the
a
Table 2. Migration of double bonds with PdCl2 and TaCl5
Ziegler-Natta catalyst (i.e. combination of TiCl3 with Et3Al),3 the
effect of second metal catalysts combined with PdCl2 was
PdCl2 (2 mol%), TaCl5 (4 mol%)
n
n
Ar
Ar
investigated (Table 1, entries 6-9, and Table S1 in ESI, entries 7-13).9
Using TaCl5 as a second catalyst, we found the yield of 2a increased
to 96% (entry 6). The ratio of PdCl2 and TaCl5 was an important
factor, and the best results were obtained using a 1:2 ratio of the
two catalysts (Table S1 in ESI, entries 7, 14, and 15). Control
experiments demonstrated that migration of the double bond of 1a
did not occur in the absence of PdCl2 even at 100 °C, which clearly
suggests that TaCl5 adjusted the catalytic activity of PdCl2. Although
a longer reaction time (24 h) was required, catalyst loading could be
decreased to 2 mol% for PdCl2 and 4 mol% for TaCl5 to isolate 2a in
94% yield (Table 2, entry 1).
THF, 60 °C
time / h
1
2
(E selective)
entry
alkene
product
tBu
1a
tBu
2a
2b
1
24
94%
2b
24
65%c
1b
MeO
R
MeO
R
1c
1d
2c
2d
Table 1. Optimization of reaction conditions
3
4
R = Cl
CF3
12
12
89%
92%
catalyst (5 mol%)
additive (10 mol%)
tBu
1a
tBu
tBu
S
S
THF, 60 °C, 12 h
1e
1f
2e
5
12
12
94%
2a
(E-selective)
Ph
85% 2f
6d
tBu
3a
4a
Ph
2f'
7%
Ph
Ph
Yield / % (E / Z)a
3a
entry
catalyst
additive
2a
4a
Ph
1g
2g
7
8
12
24
85%
(E / Z =
1
2
3
4
5
6c
7
8
9
PdCl2
PdBr2
Pd(OAc)2
NiCl2
76
48
0
0
22 (70 / 30)
Ph
Ph
57 / 43)
11 (81 / 19) 26 (65 / 35)
0
0
0
tBu
tBu
0
0
4a
2a
(E / Z = >99 / 1) E-
Ph
92%
TaCl5
0
0
0
Ph
PdCl2
PdCl2
PdCl2
PdCl2
TaCl5
FeCl3
AgOTf
ZnCl2
96
89
16
65
<1
<1
<1
<1
4b
nC5H11
68%e
nC5H11
11 (71 / 29)
24 (71 / 29)
35 (70 / 30)
9b
24
24
(E / Z = 1 / >99) 1h
2h
2i
Ph
Ph
10b,e
74%f
84%
1i
1j
aDetermined by 1H NMR. bStereoselectivity could not be determined
accurately. cHydrogenated product, 1-tert-butyl-4-pentylbenzene was
also obtained in 3% yield.
2j
11
12
With the optimized reaction conditions in hand, a series of
alkenes was subjected to the migration reaction (Table 2).10
Conversion of arylolefin 1b, which contained with an electron-
donating methoxy group, was sluggish, and required a higher
temperature (100 °C) (entry 2). In contrast, double-bond migration
of 1c and 1d bearing electron-withdrawing chloro- and
trifluoromethyl groups on the benzene ring completed in 12 h to
give 2c and 2d in 89% and 92% yields, respectively (entries 3 and 4).
aIsolated as a mixture of other regioisomers (yield of other isomers was
less than 5% otherwise noted. See SI for details). b100 oC. c1-Methoxy-
4-(3-penten-1-yl)benzene was formed in 34% yield (E / Z = 74 / 26).
d120 oC in 2-MeTHF. ePdCl2 (5 mol%) and TaCl5 (10 mol%) were used.
fObtained as a mixture of other regioisomers. Isolated yield after
purification by HPLC was described.
2 | J. Name., 2012, 00, 1-3
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obtain an acceptable yield of -alkylstyrene 2i (entry 10). Double species into the double bond followed byView-AhryticdleroOgnleinne
migration of the terminal diene 1j proceeded smoothly to furnish 2j elimination.2d,4b,d-g The present migration follows a different
DOI: 10.1039/C9CC00223E
in 84% yield (entry 11).11
mechanism as discussed above, and similar transpositions via
generation of -allyl palladium species are rare. This novel
transposition enabled chemoselective migration of the double
bond of 1a in the presence of allylether 1l. Migration of pure
unsaturated hydrocarbon 1a occurred predominantly over that
of 1l using PdCl2 and TaCl5 as a catalyst (Table 3, entry 1). This
unique selective migration over a heteroatom-containing
alkene was not achieved with the previously reported catalyst
systems. For example, HPdCl(PtBu3)2, generated in situ from
Pd(dba)2, tBu3P, and isobutyryl chloride, catalyzed the
migration of both 1a and 1l unselectively to provide mixtures
of olefin derivatives (entry 2).7c
Reaction progress of 1a was monitored by 1H NMR, which
revealed that release of the isomerized olefins 3a and 4a from a
reactive palladium center was faster than the chain walking through
1a to 2a without dissociation, and transposition of the double bond
occurred mainly via stepwise migration (Figure 1).12 Conversion of
starting olefin 1a was complete within the first 3 h, and the
proportion of intermediate 4a was greater than that of 3a at all
reaction times. These results indicate that the second migration to
3a from 4a was reversible and relatively slow compared with the
first (1a to 4a) and third migration (3a to 2a), and required a
prolonged heating time. Note that an induction period and
sigmoidal reaction profile were observed using only PdCl2 without
TaCl5 (Figure 1). This is consistent with in-situ formation of the
chloro-bridged Pd/Ta heterodinuclear complexes, which possessed
greater Lewis acidity toward carboncarbon double bonds.13-15
Table 3. Chemoselective migration of terminal alkenes
tBu
tBu
1a
1l
2a
2l
O
O
24 h
resultsa
entry
conditions
2a
1a
2l
1l
1
PdCl2 (2 mol%), TaCl5 (4 mol%)
THF, 60 °C
.90%,
X0%,
78%
81%
2b Pd(dba)2 (2 mol%), tBu3P (2 mol%)
iPrCOCl, toluene, 80 °C
2a ?5%, 2l 52%
4a 71%
1a
1l
48%
21%,
aIsolated as a mixture of other regioisomers (yields of other isomers
were less than 5%). bReference 7c.
Utilizing the current strategy to control the migration of
double bonds by second metal catalysts, site-selective
functionalization of a remote CH bond of terminal alkenes
could be achieved.17 A typical example involved one-pot
sequential migration and regioselective hydroarylation with
electron-rich 1,4-dimethoxybenzene using the combination of
Figure 1. Reaction profile for migration of 1a under the conditions
in Table 2, entry 1 (1a (■), 2a (●), 3a (◆), 4a (▲)). Time change
curve for the formation of 2a using only PdCl2 is shown with 〇.
Two commonly accepted mechanisms for migration of olefinic
double bonds can be found in the literature: (1) insertion of metal
hydride species into double bonds followed by -hydrogen PdCl2 and FeCl3 as a catalyst (Scheme 2(a)). The reaction
provided 5a in 84% yield without formation of other
regioisomers. Both PdCl2 and FeCl3 were required for the
elimination (see eq S1 in ESI), and (2) formation of -allyl metal
species followed by protodemetallation at the opposite allyl
terminus along with the regeneration of catalytic active species
(Figure 2).2,16 Preliminary insights were obtained by migration
reaction of deuterated 1k-d (eq 1). Deuterium was incorporated
selectively into C1 and C3 position, suggesting that the current
olefin migration proceeded through an intramolecular 1,3-hydrogen
shift via formation of a -allyl palladium species.16
PdCl2 (5 mol%)
FeCl3 (10 mol%)
tBu
1a
tBu
THF, 100 °C, 24 h
OMe
84%
OMe
MeO
MeO
Ar
(a)
PdCl2
HCl
removal of THF
(10 equiv)
Ar
Ar
Pd
Ar
tBu
HCl
PdCl2
5a
under reduced pressure
100 °C, 24 h
Cl
HCl
Cl
PdCl2
Pd
PdCl2 (5 mol%)
FeCl3 (10 mol%)
Ar
Ar
HCl
PdCl2
THF, 100 °C, 24 h
Figure 2. Proposed reaction mechanism
78%-d
D
D 75%-d
PdCl2 (2 mol%)
TaCl5 (4 mol%)
D
D
removal of THF
(b)
(1)
5b
48%
0%-d
under reduced pressure ClCH2CH2Cl
80 °C, 24 h
THF, 60 °C, 12 h
Ph
Ph
1k
2k
-d 97%
-d (83%-d)
Scheme 2. PdCl2- and FeCl3-catalyzed site-selective functionalization
of a remote CH bond through one-pot sequential migration of a
double bond and hydroarylation
Most of the previously reported efficient double-bond
migration reactions proceeded via insertion of a hydride metal
This journal is © The Royal Society of Chemistry 20xx
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D. M. Ohlmann, N. Tschauder, J.-P. Stockis, K. Gooen, M.
migration as shown in Table 1, entry 7, while the second
hydroarylation proceeded with FeCl3.18 The current remote
functionalization was also demonstrated by one-pot migration
and arylative cyclization cascade of 2-(4-penten-1-yl)-1,1’-
biphenyl leading to 9-butyl-9H-fluorene 5b (Scheme 2(b)).
In conclusion, the current study demonstrates the
operationally simple migration of double bonds without the
aid of heteroatom-containing functional groups. Unsaturated
hydrocarbon feedstocks are abundant and inexpensive, and
represent ideal starting materials for the synthesis of
functional materials and pharmaceuticals. The current
protocol provides an atom-efficient and redox-neutral
approach to increase the value of such olefins. Although
aromatic rings were chosen to terminate the migration and
simplify site-selectivity without using heteroatoms, the current
process may offer novel methods for the construction of
olefins that are otherwise difficult to synthesize.
View Article Online
Dierker, L. J. Gooen, J. Am. Chem. Soc.D2O01I:21,0.1130439, /1C397C1C60;0(2e2)3EE.
Larionov, L. Lin, L. Guénée, C. Mazet, J. Am. Chem. Soc. 2014,
136, 16882; (f) L. T. N. Chuc, C.-S. Chen, W.-S. Lo, P.-C. Shen, Y.-
C. Hsuan, H.-H. G. Tsai, F.-K. Shieh, D.-R. Hou, ACS Omega 2017,
2, 698. See also refs. 2a, 2b, 2c, and 2e.
8
9
For reviews on transformation promoted by cooperative
bimetallic catalyst systems, see: (a) S. Kamijo, Y. Yamamoto, In
Multimetallic Catalysis in Organic Synthesis; M. Shibasaki, Y.
Yamamoto, Eds. Wiley-VCH: Weinheim, 2004, pp. 1-52; (b) J. M.
Lee, Y. Na, H. Han, S. Chang, Chem. Soc. Rev. 2004, 33, 302; (c) C.
Wang, Z. Xi, Chem. Soc. Rev. 2007, 36, 1395.
Double-bond migration promoted by a cationic palladium
species via the generation of a cationic intermediate followed
by protodepalladation cannot be ruled out (see eq S2 in ESI).
However, addition of AgOTf as a second catalyst significantly
decreased reaction efficiency (Table 1, entry 8). Thus, the
participation of cationic palladium species by the abstraction of
a chloro group by TaCl5 may be low.
10 The migrations in this study generally did not proceed to
completion, leaving a small amount (<5% yield, except for
migration of 1b and 1h) of other internal alkenes. Prolonged
reaction times with higher loadings of the catalyst did not
increase the conversion.
11 See eqs S3 and 4 in ESI for the reaction of other olefins.
12 Because the efficiency of double-bond transposition of internal
alkene 1h was lower than that of terminal alkenes, a certain
degree of migration might occur through a chain-walking
mechanism without dissociation of intermediate internal
alkenes. If the migration occurred only via stepwise olefin
isomerization, 1h should show comparable reactivity to that of
other terminal alkenes.
13 PdCl2 is known to present as a chloro-bridged polymeric
aggregate. Thus, another effect of TaCl5 is the dissociation of
(PdCl2)n to an oligomeric structure. Isolation and structural
determination of chloro-bridged hetero dinuclear palladium
complexes, see: (a) K. Severin, K. Polborn, W. Beck, Inorg. Chim.
Acta 1995, 240, 339; (b) T. Hosokawa, M. Takano, S.-I.
Murahashi, J. Am. Chem. Soc. 1996, 118, 3990; (c) G. G. Luo, R.-
B. Huang, D. Sun, L.-R. Lin, L.-S. Zheng, Inorg. Chem. Commun.
2008, 11, 1337; (d) M. Weiss, W. Frey, R. Peters,
Organometallics 2012, 31, 6365. Note that the addition of LiCl,
which is often used to dissociate chloro-bridged oligomeric
aggregates, in place of TaCl5 completely shut down the
migration reaction. Thus, an increase in Lewis acidity on the
palladium center by coordination of TaCl5 is another important
factor to promote the current migration reaction.
Notes and references
1
(a) A. George, A. M. Olah, Hydrocarbon Chemistry, 2nd ed.;
John Wiley & Sons, 2003. (b) H. A. Wittcoff, B. G. Reuben, J. S.
Plotkin, Industrial Organic Chemicals, 2nd ed.; John Wiley &
Sons, 2004. For our works on the regioselective
functionalization of unsaturated hydrocarbons, see: (c) M.
Murai, K. Takami, K. Takai, K. Chem. Eur. J. 2015, 21, 4566;
(d) M. Murai, C. Mizuta, R. Taniguchi, K. Takai, Org. Lett.
2017, 19, 6104.
For reviews on double-bond migration, see: (a) R. Uma, C.
Crévisy, R. Grée, Chem. Rev. 2003, 103, 27; (b) N. Kuznik, S.
Krompiec, Coord. Chem. Rev. 2007, 251, 222; (c) S. Krompiec,
M. Krompiec, R. Penczek, H. Ignasiak, Coord. Chem. Rev.
2008, 252, 1819; (d) E. Larionov, H. Li, C. Mazet, Chem.
Commun. 2014, 50, 9816; (e) M. Hassam, A. Taher, G. E.
Arnott, I. R. Green, W. A. L. van Otterlo, Chem. Rev. 2015,
115, 5462.
2
3
4
A. Shimizu, T. Otsu, M. Imoto, Bull. Chem. Soc. Jpn 1968, 41,
953.
(a) N. Iranpoor, E. Mottaghinejad, J. Organomet. Chem. 1992,
423, 399; (b) H. Wakamatsu, M. Nishida, N. Adachi, M. Mori,
J. Org. Chem. 2000, 65, 3966; (c) D. B. Grotjahn, C. R.; Larsen,
J. L. Gustafson, R. Nair, A. Sharma, J. Am. Chem. Soc. 2007,
129, 9592; (d) T. Kochi, T. Hamasaki, Y. Aoyama, J. Kawasaki,
F. Kakiuchi, J. Am. Chem. Soc. 2012, 134, 16544; (e) T.
Hamasaki, Y. Aoyama, J. Kawasaki, F. Kakiuchi, T. Kochi, J. Am.
Chem. Soc. 2015, 137, 16163; (f) L. Lin, C. Romano, C. Mazet,
C. J. Am. Chem. Soc. 2016, 138, 10344; (g) T. Hamasaki, F.
Kakiuchi, T. Kochi, Chem. Lett. 2016, 45, 297; (h) A. L. Kocen,
M. Brookhart, O. Daugulis, Chem. Commun. 2017, 53, 10010.
(a) M. Newcomb, R. S. Vieta, J. Org. Chem. 1980, 45, 4793;
(b) T. Kobayashi, H. Yorimitsu, K. Oshima, Chem. Asian J.
2009, 4, 1078; (c) S. Baader, M. D. Ohlmann, L. J. Gooen,
Chem. Eur. J. 2013, 19, 9807; (d) Q. Wu, L. Wang, R. Jin, C.
Kang, Z. Bian, Z. Du, X. Ma, H. Guo, L. Gao, Eur. J. Org. Chem.
2016, 5415; (e) A. L. Kocen, K. Klimovica, M. Brookhart, O.
Daugulis, Organometallics 2017, 36, 787; (f) D. P. Ojha, K.
Gadde, K. R. Prabhu, J. Org. Chem. 2017, 82, 4859.
14 Although heating a solution of TaCl5 (0.13 mmol) in THF at 60 oC
for 12 h gave an equivalent of 4-chlorobutanol (0.13 mmol), the
migration reaction was not accelerated using 4-chlorobutanol
as an additive in place of TaCl5. Thus, PdCl2 was likely activated
by TaCl5 or TaCl4(O(CH2)4Cl).
15 For recent reviews on the transformation catalyzed by hetero
dinuclear metal complexes, see: (a) P. Buchwalter, J. Rosé, P.
Braunstein, Chem. Rev. 2015, 115, 28; (b) I. G. Powers, C. Uyeda,
ACS Catal. 2017, 7, 936.
16 (a) R. H. Crabtree, In The Organometallic Chemistry of the
Transition Metals; John Wiley & Sons, Inc.: New Haven, CT,
2014; p 224; (b) S. Biswas, Comments Inorg. Chem. 2015, 35,
300.
17 For reviews on remote functionalization based on double bond
migration, see: (a) M. Vilches-Herrera, L. Domke, A. Börner, ACS
Catal. 2014, 4, 1706; (b) A. Vasseur, J. Bruffaerts, I. Marek, Nat.
Chem. 2016, 8, 209; (c) H. Sommer, F. Juliá-Hernández, R.
Martin, I. Marek, ACS Cent. Sci. 2018, 4, 153.
5
6
7
T. Gibson, L. J. Tulich, Org. Chem. 1981, 46, 1821.
Most of palladium-catalyzed double bond migration reaction
are limited to one-carbon migration and/or required a
heteroatom-containing directing group to facilitate the
migration. For representative examples, see: (a) H. J. Lim, C. R.
Smith, T. V. RajanBabu, J. Org. Chem. 2009, 74, 4565; (b) J. Fan,
C. Wan, Q. Wang, L. Gao, X. Zheng, Z. Wang, Org. Biomol. Chem.
2009, 7, 3168; (c) D. Gauthier, A. T. Lindhardt, E. P. K. Olsen, J.
Overgaard, T. Skrydstrup, J. Am. Chem. Soc. 2010, 132, 7998; (d)
18 J. Kischel, I. Jovel, K. Mertins, A. Zapf, M. Beller, Org. Lett.
2006, 8, 19. Using PdCl2/TaCl5 as a catalyst, 5a was obtained
in 28% yield.
4 | J. Name., 2012, 00, 1-3
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