Iron Catalyzed Isomerization of α-Alkyl Styrenes to Access Trisubstituted Alkenes

Article abstract of DOI:10.1002/cjoc.202000492

Stereoselective isomerization of α-alkyl styrenes is accomplished using a new iron catalyst supported by phosphine-pyridine-oxazoline (PPO) ligand. The protocol provides an atom-efficient and operationally simple approach to trisubstituted alkenes in high

Full text of DOI:10.1002/cjoc.202000492

Chinese Journal
of Chemistry
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中 国 化 学 - An International Journal
Accepted Article
Title: Iron Catalyzed Isomerization of α-Alkyl Styrenes to Access Trisubstituted
Alkenes
Authors: Songgen Xu, Guixia Liu,* and Zheng Huang*
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This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.202000492.
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Chinese Journal
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catalysis, iron, isomerization, trisubstituted alkenes, stereoselective
CJC
中
国 化 学 - An International Journal
Iron Catalyzed Isomerization of α-Alkyl Styrenes to Access Trisubstituted
Alkenes
Songgen Xu,a Guixia Liu,*,a and Zheng Huang*,a,b,c
a.State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of
Chinese Academyof Sciences, Chinese Academyof Sciences,345LinglingRoad,Shanghai200032, China.
b Chang-Kung Chuang Institute, EastChinaNormalUniversity, Shanghai 200062, China.
c School of Chemistry and Material Sciences, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane Xiangshan,
Hangzhou 310024,China
Cite this paper: Chin.J. Chem.2019,37, XXX—XXX. DOI: 10.1002/cjoc.201900XXX
Stereoselective isomerization of α-alkyl styrenes is accomplished using a new iron catalyst supported by phosphine-pyridine-oxazoline (PPO) ligand. The
protocol provides anatom-efficientand operationally simple a pproach to trisubstituted alkenes in high yields with excellent regio- and stereoselectivities
under mild conditions. The results of deuterium-la belling a nd ra dical trap experiments are consistent with a n iron-hydride pathwa y involving reversible
alkene insertion a nd β-H elimination.
La te r, de Vries et. al. found a well-defined pinceriron complexwas
highly effective for the isomerization of allylic alcohols to ketones
Background and Originality Content
Trisubstituted alkenes are important skeletons in both natural
using tBu OK as the a cti va to r wi th b road subs trate s co pe (Scheme
and synthetic molecules, and act as versatile intermediates in
various transformations.[1] Since efficient procedures are n ow
available for the synthesis of terminal alkenes with high
re gioselecti ti y,[2] was te-free isomerization of readily a ccessible
terminal alkenes[3] provides an attractive rou te to valuable
trisubs ti tu ted alkenes. Such a transformation is conceptually
simple, but controlling regio- and stereoselectivity poses a large
challenge. Catalysts based on p re cious transition metals, such as
Rh,[4] Pd,[5] and Ru,[6] have been developed to effect the
isomerization of α-alkyl styrenes to trisusbtituted alkenes, whi ch
usually suffers from poor stereoselectivity and limited substrate
s cope . In this context, it is highly desirable to develop efficient
catal ys ts , espe cially those with low-cost a nd hi gh sustainability,
for this transformation. During the preparation of this manuscript,
three Co catalysts were independently disclosed by the groups of
Lu, Findlater and Xia, for chemo and stereoselective alkene
isomerization to afford trisubstituted alkenes.[7] In contrast,
catalyst systems using the most earth-abundant metal, iron, which
has a minimal environmental and toxicological impact, ha ve
received little attention in this area.[8]
1c).[11] In addition to the isomerization driven by the stabilizing
effe cts exerted by the heteroatoms, unfunctionalized alkenes
could also be isomerized under iron catalysis. In 2011,
Early studies showed that iron carbonyl complexes Fe(CO)5,
Fe2(CO)9, and Fe3(CO)12, are versatile catalysts for isomerization of
unsaturated alcohols, esters, ethers and amines in to
corresponding carbonyl compounds, conjugated esters, ethers
and amines, respectively (Scheme 1a).[9] However, these carbonyl
iron complexes need thermal or photo-a cti va tion to release CO
ligand and generate catalytically active metal species, limiting
their practicability. In 2013, Cahard and Renaud et. al.
demonstrated tha t a tetra(isonitrile) i ron(II) comple x co uld replace
toxic iron carbonyls for the isomerization of trifluoromethylated
allylic alcohols into the corresponding ketones (Scheme 1b).[10]
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10.1002/cjoc.202000492
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First author et al.
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Scheme 1Iron Catalysed Alkene isomerization
Results and Discussion
iron carbonyl
Table 1 Evaluation of IronCatalyst for Isomerization of α-Ethylstyrene a
compounds
a) iron carbonyl compounds
a)
OH
OH
O
O
mol
%)
mol
R
[Fe]
R
R
(2
NaHBEt
R
cat.
+
R'
R'
cat. Fe(0)
Fe(0)
%)
+
R'
R'
3 (4
n
n
n
n
Ar
Ar
Ar
Ar
or
1a
irradiation heat
solvent, rt, 2 h
irradiation or heat
R
R
R
R
-2a
Z
≥
-2a
3a
E
n
0
n ≥ 0
X
X
=
Ar 4-MeOC6H4
X
X
n
n
n
n
=
X
ester, ether, amine
X = ester, ether, amine
Fe
Fe
33(CO)1122
,
,
Fe(0): Fe(CO) , Fe (CO) , Fe (CO)
Fe(0): Fe(CO)55
22(CO)99
O
N
N
N
complex
b) Fe(II) complex
b) Fe(II)
tBu2P
tBu
Fe
PtBu2
tBu2P
Fe
N
tBu2P
Fe
N
Cl Cl
Cl Cl
cat.
cat.
Cl Cl
FeCl
FeCl22
Ar
Ar OH
N
N
OH
Ar
Ar
O
O
C
C
Fe-2
Fe-1
Fe-3
4
4
F
Ph
Ph
C
F
Ph
Ph
C
F33C
Cs CO
Cs2CO (1 equiv)
F33C
equiv)
33 (1
2
Fe
O
N
complex
c) pincer Fe complex
pincer
c)
iPr
N
O
H
H
N
Fe
Br Br
N
N
N
tBu2P
Fe
Br Br
N
O
O
PNP-Fe
OH
mol%)
(1 mol%)
OH PNP-Fe
(1
i
iPr) P Fe
iPr
(Pr) P Fe P(iPr)
(
P(iPr)22
Br
Br
2
2 Br
t
iPr
tBuOK mol%)
Br
R
R
R'
R'
Fe-4
Fe-5
R
R
R'
R'
BuOK (1 mol%)
(1
CO
CO
PNP-Fe
PNP-Fe
complex
d) Fe(III) complex
d) Fe(III)
Yield (%)b
Z-2a 3a
entrya
Cat.
solvent
Conv. (%)b
mol%)
Fe(acac) (5 mol%)
Fe(acac)33 (5
E-2a
96
R
R
R
R
mol%)
PhMgBr (50 mol%)
PhMgBr (50
1
2
3
4
5
6
7
8
Fe-1
Fe-2
Fe-3
Fe-4
Fe-5
Fe-1
Fe-1
Fe-1
pentane
pentane
pentane
pentane
pentane
THF
97
79
76
77
<5
96
96
0
ND
ND
ND
ND
1
3
1
1
76
work:
This
e) This work:
e)
mol
%)
75
(PPO)FeCl (2 mol %)
(PPO)FeCl22 (2
NaBHEt 4 mol%)
NaBHEt3 (4 mol%)
(
3
76
R
R
R
R
Ar
Ar
hexane, rt, 2 h
hexane, rt, 2 h
Ar
Ar
ND
ND ND
to 98%
>
up
up to 98% yield
yield
14:1 E/Z
95
95
ND
ND
ND
1
1
O
O
> 14:1 E/Z
examples
N
N
27
27 examples
tBu P
tBu22P
Fe
Fe
N
N
toluene
Et2O
Cl Cl
Cl Cl
tBu
tBu
ND ND
aReaction condition: 1a (0.5 mmol), [Fe] (0.01 mmol, 2 mol %) and
Na HBEt3 (0.02 mmol, 4 mol %) in solvent (2 mL) at room temperature for
2h. bDetermined by GC a na lysis using mesitylene a s the interna l sta nda rd.
ND = not detected.
von Wangelin and coworkers developed a catalytic system of
Fe (a ca c)3/ArMgBr combination for the isomerization of 1-alkenes
to 2-alkenes (Scheme 1d).[12] Despite these achievements, iron
catalyzed stereoselective alkene isomerization to access
trisubstituted alkenes without the aid of heteroatoms [9c] remains
underdeveloped.
Scheme 2. Synthesis and Molecular Structure of Fe-1
FeCl2 4H2O
Driven by our interest in the development of base metal
O
O
N
N
catalysis,[13] we re po rt he rein
a catal yti c isomerization of
rt
THF,
tBu2P
Fe
N
tBu2P
N
α-su bsti tu te d s tyre nes to trisu bsti tu ted olefins with an i ron
complex of phosphine-pyridine-oxazoline (PPO) ligand (Scheme
1e). Preliminary mechanistic experiments revealed that the
isomerization event likely occurs through an alkene insertion and
β-H elimination pathway.
Cl
Cl
86%
tBu
tBu
L-1
Fe-1
,
(PPO)
We initiated our studyby evaluating the catalytic efficiency of
several iron complexes bearingdiffere nt pincer ligands for alkene
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Running title
Chin. J. Chem.
Scheme 3. Scope of Iron-Catalyzed Alkene Isomerization.
a t roo m tempe ra tu re in pentane to gi ve 2a in high yield (96%)
with striking E-selectivity when (PPO)Fe complex Fe-1 was used as
the p re ca tal ys t (en try 1). In this case, the Z-isomer and the
hydrogenation product 3a were barely observed. Replacing the
oxazoline arm with phosphino or pyridine arm, Fe-2[14] and
Fe-3[13a] exhibited excellent selectivity but the yields decreased
significantly, with substantial amount of starting material
mol
Fe-1
%)
Fe-1 (2 mol %)
(2
NaBHEt 4 mol%)
NaBHEt3 (4 mol%)
R
R
(
R
R
3
Ar
Ar
Ar
Ar
hexane, rt, 2 h
hexane, rt, 2 h
2
2
1
1
OMe
OMe
recovered (entries
2
and 3). Similarly, the use of
R
R
imino-pyridine-oxazoline (IPO) iron complex (Fe-4)[13c] afforded
isomerization product E-2a in 76% yield with trace amount of Z-2a
and 3a (entry 4). An iron complex Fe-5[13b] b ea ring
phosphinite-iminopyridine ligand was proved to be inactive for
the isomerization (entry 5). The influence of the solvent on the
isomerization reaction was investigated with Fe-1 as the
precatalyst. While the use of pentane, toluene, THF gave
comparable reaction outcomes, no reaction happened in ether
(entries 6-8). The coordination ability of ether to the metal center
may poison the catalytically active species and deactivate the
catalyst.
b
2jb
2j
>
=
2a
R
95%
20:1
OMe,
E/Z
)
,
R = OMe, 2a, 95% yield, >20:1 (E/Z)
yield,
(
>
93%
>20:1(E/Z)
93% yield, >20:1(E/Z)
yield,
2b
Me,
95%
20:1 E/Z
,
2b
Me, , 95% yield, >20:1 (E/Z)
yield,
(
)
>
2c
Et,
92%
20:1 E/Z
,
Et, 2c, 92% yield, >20:1 (E/Z)
yield,
(
)
>
2d
tBu,
95%
20:1
E/Z
tBu, , 95% yield, >20:1 (E/Z)
)
,
F
F
2d
yield,
(
>
20:1 E/Z
( )
2e
OTBS,
93%
,
OTBS, 2e, 93% yield, >20:1 (E/Z)
yield,
E/Z c
>
20:1
yield,
(
c
2f
Ph,
94%
,
2f
Ph, , 94% yield, >20:1 (E/Z)
)
2k
2k
2g
OCF
95%
,
>20:1 E/Z
,
OCF , 2g, 95% yield, >20:1 (E/Z)
yield,
(
)
3
3
d
d
>
2h
CF
94%
,
20:1 E/Z
,
2h
CF3, , 94% yield, >20:1 (E/Z)
yield,
>
(
)
92%
>20:1(E/Z)
92% yield, >20:1(E/Z)
3
yield,
2i
92%
20:1 E/Z
,
H
H
,
,
2i, 92% yield, >20:1 (E/Z)
yield,
( )
Me
Me
MeO
MeO
F
F
The substrate scope of the (PPO)Fe catalyzed alkene
isomerization was explored (Scheme 3). A wide range of geminal
disubstituted arylalkenes were successfully isomerized to furnish
the desired trisubstituted (E)-alkene in high yields wi th
remarkable re gio- and stereo-control. The ca tal yti c s yste m was
effe cti ve for α-ethyl styrenes wi th bo th ele ctron –dona tin g (2a, 2e,
2j, 2m, 2p-2r) and -withdrawing groups (2h, 2k, 2n, 2o) on the a ryl
ring. Various functionalities such as methoxy, silyl ether, CF3, OCF3
and fluoro grou ps were well tolerated. The substituents at para-,
ortho, and meta-position of the phenyl ring had little impact on
the isomerization (2a-2q). Naphthyl alkene could be readily
isomerized to afford the corresponding trisubstituted alkene 2r in
90% yield with excellent E-selectivity. The α-alkyl styrenes in
which the R group is larger than a methyl group underwent
isomerization smoothly to gain sa tisfied ou tp u ts. The
isomerization of alkene 1u with a bulky propyl group in the
homoallylic position gave the trisubstituted alkene 3u in 88% yield
wi th 10% of 1u recovered.[15] To be note, this iron based catalytic
system was compatible with α-benzyl styrene, affording diaryl
subs ti tu ted alkene 2x in 96% yield with E/Z ratio more than 20:1.
Moreover, e xo cyclic alkenes were suitable substrates, producing
the endocyclic alkenes (2y-2aa) in excellent yields with exclusive
regioselectivity.
2l
2m
2m
2n
2n
2l
>
>
96%
20:1 E/Z
96% yield, >20:1 (E/Z)
yield,
( )
>
93%
20:1 E/Z
93%
20:1 E/Z
93% yield, >20:1 (E/Z)
yield,
(
)
93% yield, >20:1 (E/Z)
yield,
(
)
F
F
O
O
O
O
2q
2q
2o
2o
O
O
2p
2p
F
F
93%
>20:1(E/Z)
93% yield, >20:1(E/Z)
94%
>20:1(E/Z)
94% yield, >20:1(E/Z)
yield,
94%
yield,
94% yield, 14:1(E/Z)
yield, 14:1(E/Z)
n-C
H
n-C
n-C33H77
H
n-C66H1133
c
2rc
MeO
MeO
2s
2s
2t
2t
2r
90%
>20:1(E/Z)
90% yield, >20:1(E/Z)
yield,
91%
>20:1(E/Z) 92%
91% yield, >20:1(E/Z) 92% yield, 17:1(E/Z)
yield, yield, 17:1(E/Z)
OTBS
OTBS
O
O
,
b d
2ub,d
2w
2w
2v
2v
2u
92%
>20:1(E/Z)
92% yield, >20:1(E/Z)
yield,
90%
>20:1(E/Z)
90% yield, >20:1(E/Z)
yield,
88%
>20:1(E/Z)
88% yield, >20:1(E/Z)
yield,
,
b d
2xb,d
2x
,
,
2z
2aa
97%
>20:1(E/Z)
96%
2y,
98%
95%
97% yield, >20:1(E/Z) 2y, 96% yield 2z, 98% yield 2aa, 95% yield
yield,
yield
yield
yield
aRea ction condition: 1 (0.5 mmol), Fe-1 (0.01 mmol) and NaHBEt3 (0.02
mmol) in pentane (2 mL) at room temperature for 2h. Isolated yields. b1h
(0.2 mmol). cToluene was used as solvent. d8h.
isome ri za tion using me tho xy subs ti tu te d α-ethylstyrene 1a as the
model substrate and NaHBEt3as the a cti va to r (table 1). No te that
the pincer ligands investigated here can be readily prepared in
two-to -three steps from commercially available starting materials.
A new iron complex Fe-1 was synthesized by treatment of a
phosphine-pyridine-oxazoline (PPO) ligand[13d] with iron dichloride
in THF, and its solid structure was established by X-ra y diffra ction
analysis. To our delight, isomerization of 1a proceeded smoothly
Chin. J. Chem. 2019, 37, XXX－XXX
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First author et al.
Report
Scheme 4. Mechanistic studies
Scheme 5. Plausible Mechanism
H
Deuterium-labelling
experiment
a) Deuterium-labelling experiment
a)
34% D
34% D
[Fe]
CH
CH (D)
33(D)
R
R
Ar
Ar
CH
CH (D)
33(D)
alkene insertion
H
Fe-1
Fe-1
mol%
(2 mol% )
(2
)
D
5%
5% D
D
D
D
D
NaHBEt 4 mol%)
NaHBEt3 (4 mol%)
(
3
H(D)
H(D)
rt, 2h
97%
D
pentane,
pentane, rt, 2h
94% D
94% D
97% D
-
-
NaBHEt3
1i
1i
d
-d22
>
2i
d
92%
Z/E 20:1
,
2i
-d , 92% yield, Z/E > 20:1
yield,
[Fe]-H
2
2
(PPO)FeCl2
[Fe]
Ar
R
Crossover
experiment
b) Crossover experiment
b)
H
19% D
19% D
17% D
17% D
D
5%
D
6%
5% D
6% D
CH
CH (D)
33(D)
R
CH
CH (D)
33(D)
-H elimination
β
Ar
-
R
CH
CH (D)
33(D)
CH
CH (D)
33(D)
1i
d
1i
Ar
-d22
Fe-1
Fe-1
mol%
(2 mol% )
(2
)
+
+
+
+
H
NaHBEt 4 mol%)
NaHBEt3 (4 mol%)
pentane, rt, 2h
pentane,
H(D)
H(D)
[Fe]
(
H(D)
H(D)
3
1a
1a
-
MeO
MeO
rt, 2h
86% D
86% D
D
9%
9% D
D-2i
Z/E 20:1
Z/E > 20:1
D-2a
94%
,
, 94% yield
91%
>
,
Conclusions
D-2i
D-2a
Z/E 20:1
Z/E > 20:1
, 91% yield
yield
yield
>
In summa ry, we successfully developed an iron catalyzed
stereoselective isomerization of α-alkyl styrenes to trisubs ti tu ted
alkenes with phosphine-pyridine-oxazoline(PPO) as the ligand. A
broad scope of substrates compatible with many common
functional groups were readily isomerized under mild conditions.
Deuterium labelling and radical trapping experiments support a
stepwise H-transfer pathway with an intermediacy of Fe-H spe cies,
involving an alkene insertion and β-H elimination sequence.
Radical trap
experiment
c) Radical trap experiment
c)
1,1-diphenylethylene
1,1-diphenylethylene
equiv)
(1.0 equiv)
(1.0
Fe-1
Fe-1
NaHBEt 4 mol%)
NaHBEt3 (4 mol%)
ppeennttaannee,, rt, 2h
mol%
(2 mol% )
(2
)
2a
2a
MeO
MeO
MeO
MeO
(
3
>
1a
1a
20:1
94%, Z/E
yield 94%, Z/E > 20:1
yield
rt, 2h
Deuterium-labelling and radical trap experiments we re ca rried
out to provi de insigh ts in to the mechanism. The deuterated
substrate 1i-d2 containing an allylic CD2 unit was submitted to the
standard catalytic conditions, affording trisubstituted alkene 2i-d2
in 92% yield with 34% D-co nte n t in the newl y fo rmed me th yl
group, 94% D in the vinyl group and 5% D in the methyl group
trans to the phenyl group (Sche me 4a ). The intramolecular H/D
scrambling indicates that the formation and cleavage of C-H bond
during isomerization is reversible. To probe the possibility of
intermolecular H/D scrambling, a 1:1 mixture of 1i-d2 and 1a was
sub je cted to the rea ction (Scheme 4b ). The NMR analysis of the
Experimental
General Description. All manipulations were carried out in a
ni tro gen -filled glovebox or under an atmosphere of dry argon
using standard Schlenk techniques, unless stated otherwise.
Pentane, tetrahydrofuran (THF) and ether were purchased from
Sinopharm Group Chemical Co., Ltd. and dried over LiAlH4
overnight under an atmosphere of dry argon, then distilled prior
to use and stored in an argon atmosphere glovebox. Toluene was
distilled from sodium benzophenone ketyl prior to use. I ron
complexes were prepared according to previously reported
procedures.[13-14] All other reagents and solvents used in this study
were purchased from commercial sources and used as received.
NMR spectra were recorded on Agilent 400 MHz, Varian 400 MHz
and Bruker 400 MHz at ambient temperature. The residual peak
of deuterated solvent was used as a reference for 1H and 13C
chemical shifts. GC analysis was acquired on Agilent 7890A gas
chromatograph equipped with a flame-ionization detector.
General procedure for isomerization of α-Alkyl styrenes. In an
ni tro gen -filled glove-box, an oven-dried 10 mL thin-wall glass tube
was charged wi th Fe-1 (10 µmol, 4.8 mg), pentane (2 mL), α-alkyl
styrenes (0.5 mmol). The resulting solution was added NaHBEt3
(20 µmol, 1 M in THF). The tube was sealed with a Teflon plug,
and the rea ction mi xtu re was s ti rred a t ro om tempe ra tu re fo r 2h .
The reaction was quenched by exposing the rea ctio n mi xtu re to
air. The solvent was removed under vacuum and the residue was
purified by flash silica gel column chromatography to gi ve the
product, which was analyzed by 1H NMR to de te rmine the
stereoselectivity.
two isolated isomerization products revealed
a decreased
deuterium incorporation in D-2i along with a crossover deuterium
incorporation into D-2a. The intermolecular H/D scrambling ruled
out the concerted H-transfer pathways such as 1,3-H shift
mechanism vi a allylic metal species and oxidative cyclization
mechanism. Fu rthe rmo re , the rea ction o f 1a in the presence of a
radical scavenger 1,1-diphenylethylene proceeded smoothly
without ob vi ous influence on the reaction outputs (Scheme 4c),
indicatinga radical pathwaymaynot be an operative pathway.
Based on all these experimental observations and previous
lite ra tu re ,[8a] the (PPO)Fe catalyzed alkene isomerization most
likely occurred via a stepwise H-transfe r path wa y involving a
Fe-hydride intermediate, which undergoes reversible alkene
insertion and β-H elimination to produce the isomerized alkene
and regenerate the catalytically active Fe-H spe cies (Sche me 5).
The additive NaBHEt3 reduces the p re ca tal yst to fo rm Fe-H species
to initiate the catalytic cycle. However, the exact structure of Fe-H
intermediate is unclear at present.
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Running title
Chin. J. Chem.
Pathways. Comments Inorg. Chem. 2015, 6, 300-330; (d) Hassam, M.;
Taher, A.; Arnott, G. E.; Green, I. R. van Otterlo, W. A. L.
Isomerization of Allylbenzenes. C h em . Rev. 2015, 11, 5462-5569; (e)
Vasseur, A.; Bruffaerts, J. Marek, I. Remote functionalization through
alkene isomerization. Nat Chem. 2016, 3, 209-219; (f) Molloy, J. J.;
Morack, T. Gilmour, R. Positional and Geometrical Isomerisation of
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Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
Acknowledgement (optional)
Financial support from National Natural Science Foundation of
China (21825109, 21821002, 21732006), National Basic Research
Program of China (2016YFA0202900), the Strategic Priority
Research Program of Chinese Academy of Sciences
(XDB20000000), Chinese Academy of Sciences Key Research
Pro gram o f F ro n tie r S cien ces (QYZD B-SSW-SLH016) and K.C.Wong
Education Foundation, and Science and Technology Commission
of Shanghai Municipality (17JC1401200) is gratefully
acknowledged.
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© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

First author et al.
Report
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(The following willbe filled in by the editorialstaff)
Manuscriptreceived: XXXX, 2019
Manuscriptrevised: XXXX,2019
Manuscriptaccepted: XXXX, 2019
Accepted manuscript online: XXXX,2019
Version of recordonline:XXXX, 2019
www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
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Running title
Chin. J. Chem.
Entry for the Table of Contents
Page No.
Iron Catalyzed Isomerization of α-Alkyl Styrenes
to Access Trisubstituted Alkenes
Fe
R
R
Ar
O
N
Ar
tBu2P
Fe
N
=
or
to
up
98%
Cl Cl
R
H
tBu
aryl,
yield
akyl
>
14:1
E/Z
(PPO)FeCl2
examples
27
A
well defined iron complex of phosphine-pyridine-oxa zoline catalyzes stereoselective
isomerization of α-alkyl styrenes, providing an atom-efficient and opera tiona l simple approa ch to
trisubstituted alkenes in highyields with excellentregio- and stereoselectivities.
Songgen Xu, Guixia Liu,* and Zheng Huang*
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.