Highly regioselective [3,3] rearrangement of aliphatic allyl vinyl ethers catalyzed by a metalloporphyrin complex, Cr(TPP)Cl

Article abstract of DOI:10.1016/j.tet.2006.07.051

The Claisen rearrangement of simple aliphatic allyl vinyl ethers catalyzed by a metalloporphyrin, Cr(TPP)Cl, is described. The porphyrin-based Lewis acid catalyst can effectively accelerate the rearrangement via a concerted [3,3] pathway with a minimal degree of bond ionization of the substrates, providing the corresponding Claisen products in moderate to high yields and almost perfect regioselectivity at low catalyst loading.

Full text of DOI:10.1016/j.tet.2006.07.051

Tetrahedron 62 (2006) 9467–9474
Highly regioselective [3,3] rearrangement of aliphatic allyl vinyl
ethers catalyzed by a metalloporphyrin complex, Cr(TPP)Cl
*
Toshikatsu Takanami, Mikiko Hayashi, Kazuhiro Iso, Hirose Nakamoto and Kohji Suda
Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan
Received 2 June 2006; accepted 4 July 2006
Available online 14 August 2006
Abstract—The Claisen rearrangement of simple aliphatic allyl vinyl ethers catalyzed by a metalloporphyrin, Cr(TPP)Cl, is described. The
porphyrin-based Lewis acid catalyst can effectively accelerate the rearrangement via a concerted [3,3] pathway with a minimal degree of bond
ionization of the substrates, providing the corresponding Claisen products in moderate to high yields and almost perfect regioselectivity at low
catalyst loading.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
bulky organoaluminum Lewis acids, such as MABR,
ATPH, and BINAL, developed by Yamamoto et al., are
known as indeed potential reagents capable of circumvent-
ing these problems associated with the Lewis acid-mediated
Claisen rearrangement. These aluminum Lewis acids are,
unfortunately, a stoichiometric reagent rather than a catalyst:
more than a stoichiometric amount of the reagent is usually
necessary to promote the rearrangement.5,11
The Claisen rearrangement, a [3,3] sigmatropic rearrange-
ment of allyl vinyl ether, is a powerful carbon–carbon
bond forming process1,2 and its catalytic version employing
a substoichiometric amount of metal catalysts is a topic of
ongoing interest.3 While the rearrangement using palladium-
and related transition metal-based catalysts has been well
developed,3,4 only a few reports have appeared in the litera-
ture that utilize Lewis acids, especially in a catalytic fash-
ion.3,5–7 To date, several Lewis acids, including Al(III),5
Sn(IV),6 Cu(II),7 and lanthanide(III)7 Lewis acids, have
been available for the Claisen rearrangement of aliphatic
allyl vinyl ethers. These examples, however, require stoi-
chiometric amounts of reagents or specific substrates such
as 2-alkoxycarbonyl-substituted allyl vinyl ethers. In addi-
tion, most of these Lewis acid-mediated methods appear to
suffer from a lack of regioselectivity, being troubled by the
formation of the regioisomeric [1,3] rearrangement prod-
ucts. The reason might be that, under Lewis acid conditions,
the rearrangement often proceeds through a process involv-
ing formation of an allyl cation and a metallo-enolate ion
pair, which diverges from the generally accepted concerted
mechanism, affording a regioisomeric mixture of [3,3]- and
[1,3]-rearrangement products (Scheme 1).8 Herein lies the
difficulty with the Lewis acid-catalyzed Claisen rearrange-
ment, as the ionic intermediates may be long-lived, to give
rise to undesired regioisomeric [1,3] products. Actually,
Rovis and Nasveschuk recently reported that an increase in
the strength of the Lewis acid and/or in stability of the allyl
cation results in increased [1,3] selectivity.9,10 Although
R2
R2
R1
O
R1
O
[3,3]
R2
R2
O
LA
R2
R1
R1
R1
O
O
LA
[1,3]
Scheme 1. Putative mechanistic scheme for the competitive formation of the
[3,3] and [1,3] adducts in the Lewis acid-mediated Claisen rearrangement of
aliphatic allyl vinyl ethers.
Recently, we have reported that a metalloporphyrin com-
plex, Cr(TPP)Cl, can be used as a mild and efficient Lewis
acid catalyst, and it enhances reversal E/Z selectivity in the
thermal Claisen rearrangement of 4,5- and 4,6-disubstituted
allyl vinyl ethers.12–14 The purpose of this paper is to de-
scribe our results concerning the reactivity, regioselectivity,
and scope of the Cr(TPP)Cl catalyst system in the Claisen
rearrangement of simple aliphatic allyl vinyl ethers. This
metalloporphyrin-based weak Lewis acid catalyst can
* Corresponding author. Tel./fax: +814248779; e-mail: suda@my-pharm.
ac.jp
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.07.051

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T. Takanami et al. / Tetrahedron 62 (2006) 9467–9474
effectively depress the formation of ionic intermediates, yet
enhances the concerted [3,3] process, exhibiting high regio-
selectivity over a broad range of substrates, exclusively pro-
viding the corresponding Claisen products in good to high
yields, in a fully catalytic fashion.
especially the chromium complex Cr(TPP)Cl, was found to
be effective to achieve high [3,3] selectivity in the Claisen
rearrangement of aliphatic allyl vinyl ethers, and these ob-
servations are consistent with the hypothesis that a weaker
Lewis acid is capable of accelerating the Claisen rearrange-
ment via a concerted [3,3] pathway, while stronger Lewis
acids result in bond ionization.9
2. Results and discussion
We initiated our studies by subjecting the vinyl ether of
4-phenyl-3-buten-2-ol 1a to 5 mol % of Cr(TPP)Cl in di-
chloroethane at 83 ꢀC for 7 h. While only moderate regiose-
lectivity ([3,3]:[1,3]¼1:1 to 1:2) has been reported for the
rearrangement of 1a with various Lewis acids, such as
Cu(OTf)2, SnCl4, TiCl4, and B(C6F5)3,9,10b under the present
catalytic conditions utilizing Cr(TPP)Cl catalyst, the sub-
strate 1a was cleanly converted to the [3,3] adduct 2a in
94% yield; no other products including [1,3] adduct 4a could
be identified via 1H NMR analysis of the crude reaction mix-
ture (Table 1, entry 1). In the absence of the metallopor-
phyrin catalyst, the rearrangement was quite sluggish, and
did not complete over 48 h, giving the [3,3] adduct 2a as
the sole product in only 40% yield (Table 1, entry 2).
Regioselective transformation of 1a to 2a could also be
accomplished with other metalloporphyrin catalysts, such
as Fe(TPP)Cl and Mn(TPP)Cl (Table 1, entries 3 and 4).
Likewise, metallosalen complexes, Cr(salen)Cl and Mn(sa-
len)Cl, could serve as a highly regioselective catalyst for
the rearrangement (Table 1, entries 5 and 6).15 In both cases,
however, the highest yield never exceeded 85%. On the other
hand, stronger Lewis acid catalysts, Cr(TPP)OTf and Fe(TP-
P)OTf, which may enhance bond ionization of the substrate,
proved less effective for the [3,3] selectivity, affording the
undesired [1,3] adducts 4a as the major products in 26 and
27% yields, respectively, along with the [3,3] adducts 2a
in less than 20% yield (Table 1, entries 7 and 8). Thus, the
use of porphyrin catalysts possessing weaker Lewis acidity,
To assess the inherent regioselectivity of the chromium por-
phyrin catalyst, Cr(TPP)Cl, we then explored the reactivity
of several cinnamyl vinyl ethers 1. Although these substrates
1 are known to be less suited for the [3,3] selectivity,9 the
presence of 5 mol % of Cr(TPP)Cl16 led to the formation
of the corresponding [3,3] adducts 2 in moderate to high
yields and excellent regioselectivity (Table 2). In the cata-
lytic process, substituents on the vinyl moiety in the sub-
strates did not affect the regioselectivity (Table 2, entries 2
and 3). Notably, even in the presence of an electron-donating
substituent on the ring, the rearrangements occurred with
high [3,3] selectivity, giving the Claisen adducts solely in
good yields (Table 2, entries 6 and 7).
As illustrated in Table 3, allyl vinyl ethers beyond those de-
rived from cinnamyl alcohol also underwent the catalytic
[3,3] rearrangement. For example, the Cr(TPP)Cl-catalyzed
rearrangement of the substrates 3a and 3b, which are the re-
gio isomers of 1a and 1d, respectively, took place smoothly
to give the corresponding [3,3] adducts, 4a and 4b, as the
sole products in high yields (Table 3, entries 1 and 2).
Replacing the Ph substituent of 1a, 1b, and 1c with a Bu
group (3c, 3d, and 3e) also produced the corresponding
Claisen products, 4c, 4d, and 4e, respectively, in high yields
and excellent regioselectivity (Table 3, entries 3–5).
To further explore the scope of the [3,3] rearrangement of
allyl vinyl ethers, the rearrangement of the substrates 5 bear-
ing trisubstituted alkenes in the allyl systems was examined.
It has been known that the rearrangement of trisubstituted
allyl vinyl ethers 5 generally provides high [1,3] selectivity
with a range of Lewis acids, such as Cu(OTf)2, SnCl4, TiCl4,
Me2AlCl, and EtAlCl2: under such ionizing conditions, re-
combination of the metallo-enolate and allyl cation at the
less hindered secondary position to give [1,3] adducts should
be fast compared with [3,3] recombination to form a quater-
nary carbon center at the tertiary cation (Fig. 1).9 However,
when the Cr(TPP)Cl catalyst was applied to the substrates 5,
moderate to high-yielding [3,3] rearrangement to create qua-
ternary carbon centers occurred without any formation of the
corresponding [1,3] products (Table 4). In addition, under
the present catalytic conditions, all the substrates examined
generally rearranged more rapidly and had higher yields of
the [3,3] products than those rearrangements performed un-
der non-catalytic thermal conditions (see footnotes in Tables
2–4). These findings, thus, should lend significant support to
our view that the Cr(TPP)Cl catalyst can exert its influence
on accelerating the rearrangement via a concerted [3,3] path-
way with a minimal degree of bond ionization (Scheme 1).
Table 1. Porphyrin-based Lewis acid-catalyzed Claisen rearrangement of
vinyl ether of 4-pheny1-3-buten-2-ol 1a
X
Ph
N
Ph
N
M
N
Ph
N
[1,3]
[3,3]
Ph
O
O
O
5 mol% M(TPP)X
Ph
Me
Me
ClCH2CH2Cl, 83°C
Ph
Me
Ph
1a
2a
4a
Entry
Catalyst
Time (h)
2a (%) (E/Z)a,b
4a (%)a
1
2
3
4
5
6
7
8
Cr(TPP)Cl
None
7
58
24
24
11
24
24
2
94 (15:85)
40 (94:6)
62 (94:6)
83 (95:5)
59 (85:15)
62 (94:6)
19 (77:23)
16 (>99:1)
—
—
—
—
—
—
26e
27e
Mn(TPP)Cl
Fe(TPP)Cl
Cr(salen)Clc
Mn(salen)Cld
Cr(TPP)OTf
Fe(TPP)OTf
a
Isolated yield.
E/Z ratios were determined by 300 MHz 1H NMR.
b
c
Cr(salen)Cl: (S,S)-(+)-N,N0-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclo-
hexanediamino chromium(III) chloride.
Mn(salen)Cl: (S,S)-(+)-N,N0-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclo-
hexanediamino manganese(III) chloride.
An inseparable complex mixture of by-products was also produced in the
catalytic rearrangement.
3. Conclusion
d
e
In summary, we have shown a regioselective Claisen rear-
rangement of simple aliphatic allyl vinyl ethers utilizing

T. Takanami et al. / Tetrahedron 62 (2006) 9467–9474
Table 2. Cr(TPP)Cl-catalyzed Claisen rearrangement of cinnamyl vinyl ethersa
9469
Entry
Substrates
Products
Time (h)
Yield (%) (E/Z)b,c,d
O
O
1
7
94 (15:85)
Ph
Me
Ph
Me
2a
Me
O
1a
Me
O
2
5
93 (69:31)
Ph
Ph
Me
Me
Ph
Ph
Me
Me
2b
Ph
O
1b
Ph
O
3
4
5
0.5
52
6
82 (76:24)
1c
2c
O
O
41
72
Ph
Ph
1d
2d
Me
Me
O
O
Ph
Ph
2e
1e
O
O
6
7
8
62 (38:62)
57 (39:61)
Me
Me
Me
Me
1f
2f
MeO
Me
MeO
Me
O
O
7
1g
2g
a
Conditions: 5 mol % Cr(TPP)Cl, ClCH2CH2Cl, 83 ꢀC.
Isolated yield.
b
c
d
E/Z ratios were determined by 300 MHz 1H NMR.
The reaction time, yields, and E/Z ratios obtained in the non-catalytic thermal rearrangement (ClCH2CH2Cl, 83 ꢀC) of 1a–g were as follows: 2a (58 h, 40%,
E/Z¼94:6); 2b (48 h, 74%, E/Z>99:1); 2c (4 h, 43%, E/Z>99:1); 2d (93 h, 15%); 2e (48 h, 10%); 2f (50 h, 76%, E/Z¼94:6); 2g (25 h, 54%, E/Z¼98:2).
a metalloporphyrin-based Lewis acid catalyst, Cr(TPP)Cl, at
low catalyst loading. This weak Lewis acid catalyst,
Cr(TPP)Cl, is believed to accelerate the rearrangement via
a concerted [3,3] pathway, and can provide the correspond-
ing Claisen adducts in good to high yields, with almost per-
fect regioselectivity. The sense of regioselectivity observed
in the catalytic process is hardly attainable with any other
Lewis acid reagents or catalysts thus far reported for the
Claisen rearrangement, where bond ionization of the sub-
strates usually takes place to give a regioisomeric mixture
of [3,3] and [1,3] adducts. Moreover, the present catalytic re-
action provides a complementary method to the [1,3] selec-
tivity obtained by Rovis and Nasveschuk.9 Current efforts
are directed at second-generation designs for the porphy-
rin-based Lewis acid catalysts that will lead to catalytic
asymmetric Claisen rearrangement of simple aliphatic allyl
vinyl ethers.
The chemical shifts were reported in parts per million rela-
1
tive to CHCl3 (d¼7.24) for H NMR and relative to the
central CDCl3 resonance (d¼77.0) for 13C NMR. IR spectra
were recorded on a JASCO FT/IR-7000 spectrophotometer.
The mass spectroscopic data were obtained on a JEOL
JNM-DX302 spectrometer. Column chromatography was
performed on Merck silica gel 60 (230–400 mesh). 1,2-Di-
chloroethane was distilled from CaH2. Chromium(III) and
iron(III) tetraphenylporphyrin complexes, Cr(TPP)Cl,17
Cr(TPP)OTf,13a and Fe(TPP)OTf,13a were prepared by the
literature methods. Fe(TPP)Cl was purchased from Aldrich
Chemical Co. Other chemicals were commercial products
and were used without further purifications.
4.2. General procedure for the preparation of vinyl
and isopropenyl ethers of allylic alcohols18
A mixture of allylic alcohol (30 mmol), mercury(II) acetate
(6.4 g, 20 mmol), and freshly distilled ethyl vinyl ether or 2-
methoxypropene (150 mL) was heated under reflux for 30 h
under an argon atmosphere. The reaction mixture was
quenched with 5% KOH aqueous solution (30 mL) and ex-
tracted with n-hexane. The organic layer was dried over
MgSO4 and concentrated in vacuo. The residue was purified
by column chromatography on alumina (Merck Aluminum
4. Experimental
4.1. General
1H and 13C NMR spectra were recorded on JEOL JNM-
EX270, JNM-AL300, and JNM-GSX400 spectrometers.

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T. Takanami et al. / Tetrahedron 62 (2006) 9467–9474
Table 3. Cr(TPP)Cl-catalyzed Claisen rearrangement of allyl vinyl ethersa
Entry
1
Substrates
Products
Time (h)
9
Yield (%) (E/Z)b,c,d
86 (>99:1)
O
O
Me
Ph
Me
Ph
4a
3a
O
O
2
3
2
93 (>99:1)
Ph
O
Ph
4b
3b
O
12
62 (28:72)
n-Bu
n-Bu
n-Bu
Me
Me
Me
n-Bu
n-Bu
n-Bu
Me
Me
Me
4c
3c
Me
Me
O
O
4
3
1
89 (77:23)
93 (80:20)
4d
3d
Ph
Ph
O
O
5
4e
3e
a
Conditions: 5 mol % Cr(TPP)Cl, ClCH2CH2Cl, 83 ꢀC.
Isolated yield.
b
c
d
E/Z ratios were determined by 300 MHz 1H NMR.
The reaction time, yields, and E/Z ratios obtained in the non-catalytic thermal rearrangement (ClCH2CH2Cl, 83 ꢀC) of 3a–e were as follows: 4a (30 h, 83%,
E/Z>99:1); 4b (24 h, 70%, E/Z>99:1); 4c (24 h, 22%, E/Z¼97:3); 4d (24 h, 59%, E/Z>99:1); 4e (6 h, 90%, E/Z>99:1).
1-phenyl-3-vinyloxyprop-1-ene (1d),5i (E)-1-phenyl-3-iso-
propenyloxyprop-1-ene (1e),19 (E)-1-(4-methoxyphenyl)-
3-vinyloxybut-1-ene (1f),9 (E)-1-(4-methylphenyl)-3-vinyl-
oxybut-1-ene (1g),9 (E)-4-phenyl-4-vinyloxybut-2-ene
(3a),9 3-phenyl-3-vinyloxyprop-1-ene (3b),5d (E)-4-methyl-
2-vinyloxyoct-3-ene (5a),9 and (E)-2-phenyl-4-vinyloxy-
pent-2-ene (5b).9
R2
R3
[3,3]
R1
[1,3]
O
LA
Figure 1. [1,3] Selective rearrangement of trisubstituted allyl vinyl ethers 6
under ionic conditions.
4.2.1. (E)-1-Phenyl-3-isopropenyloxybut-1-ene (1b). Col-
orless oil; 1H NMR (CDCl3, 300 MHz) d 7.31–7.12 (m, 5H),
6.45 (d, J¼16.1 Hz, 1H), 6.12 (dd, J¼16.1 and 6.2 Hz, 1H),
4.62 (dq, J¼6.2 and 6.2 Hz, 1H), 3.84 (br d, J¼3.3 Hz, 2H),
1.77 (s, 3H), 1.34 (d, J¼6.4 Hz, 3H); 13C NMR (CDCl3,
Oxide 90 active basic, activity III) using hexane as an eluent
to give the corresponding allyl vinyl ethers in 95–60%
yields. The following obtained allyl vinyl ethers are known
compounds: (E)-1-phenyl-3-vinyloxybut-1-ene (1a),9 (E)-
Table 4. Cr(TPP)Cl-catalyzed Claisen rearrangement of trisubstituted allyl vinyl ethersa
Entry
Substrates
Me
Products
Time (h)
20
Yield (%) (E/Z)b,c,d
57 (>99:1)
O
O
Me
1
n-Bu
Me
n-Bu
Me
6a
5a
Me
5b
O
O
Me
Ph
2
50
3
51 (>99:1)
Ph
Me
Me
6b
Ph
Me
O
Ph
O
3
78
Me
Me
Me
5c
6c
a
Conditions: 5 mol % Cr(TPP)Cl, ClCH2CH2Cl, 83 ꢀC.
Isolated yield.
b
c
d
E/Z ratios were determined by 300 MHz 1H NMR.
The reaction time, yields, and E/Z ratios obtained in the non-catalytic thermal rearrangement (ClCH2CH2Cl, 83 ꢀC) of 5a–c were as follows: 6a (70 h, 38%,
E/Z>99:1); 6b (98 h, 30%, E/Z>99:1); 6c (48 h, 27%).

T. Takanami et al. / Tetrahedron 62 (2006) 9467–9474
9471
100 MHz) d 157.9, 136.7, 130.8, 129.8, 128.4, 127.4, 126.3,
83.0, 73.0, 21.7, 21.3. Exact EIMS calcd for C13H16O:
188.1201. Found: 188.1198.
J¼15.6 and 6.2 Hz, 1H), 4.62 (d, J¼2.4 Hz, 1H), 4.60 (dq,
J¼6.2 and 6.2 Hz, 1H), 4.18 (d, J¼2.4 Hz, 1H), 1.99 (q,
J¼6.8 Hz, 2H), 1.36 (d, J¼6.2 Hz, 3H), 1.31–1.21 (m,
4H), 0.84 (t, J¼7.1 Hz, 3H); 13C NMR (CDCl3,
67.8 MHz) d 158.5, 137.2, 132.0, 130.9, 128.2, 128.0,
125.5, 84.4, 73.9, 31.9, 31.3, 22.2, 21.4, 13.9. Exact EIMS
calcd for C16H22O: 230.1671. Found: 230.1675.
4.2.2. (E)-2-Vinyloxyoct-3-ene (3c). Colorless oil; 1H NMR
(CDCl3, 300 MHz) d 6.30 (dd, J¼6.4 and 14.1 Hz, 1H),
5.58–5.67 (m, 1H), 5.44–5.35 (m, 1H), 4.28 (dd, J¼14.1
and 1.5 Hz, 1H), 4.26 (dq, J¼6.4 and 6.4 Hz, 1H), 3.97
(dd, J¼6.4 and 1.5 Hz, 1H), 2.05–1.99 (m, 2H), 1.27 (d,
J¼6.4 Hz, 3H), 1.40–1.26 (m, 4H), 0.88 (t, J¼7.0 Hz, 3H);
13C NMR (CDCl3, 100 MHz) d 150.2, 132.9, 130.7, 88.5,
76.6, 31.9, 31.3, 22.5, 21.3, 14.0. Exact EIMS calcd for
C10H18O: 154.1358. Found: 154.1356.
4.3.3. 2-Methyl-4-(a-styryl)oxybut-2-ene (5c). Colorless
oil; 1H NMR (CDCl3, 300 MHz) d 7.63–7.57 (m, 2H),
7.34–7.27 (m, 3H), 5.50 (br t, J¼6.6 Hz, 1H), 4.64 (d,
J¼2.6 Hz, 1H), 4.40 (br d, J¼6.6 Hz, 2H), 4.21 (d,
J¼2.6 Hz, 1H), 1.79 (s, 3H), 1.72 (s, 3H); 13C NMR
(CDCl3, 67.8 MHz) d 159.9, 137.2, 136.7, 128.3, 128.0,
125.4, 119.9, 82.4, 64.8, 25.7, 18.2. Exact EIMS calcd for
C13H16O: 188.1201. Found: 188.1200.
4.2.3. (E)-2-Isopropenyloxyoct-3-ene (3d). Colorless oil;
1H NMR (CDCl3, 300 MHz) d 5.59 (dt, J¼15.5 and
6.6 Hz, 1H), 5.41 (dd, J¼15.5 and 6.2 Hz, 1H), 4.46 (dq,
J¼6.3 and 6.3 Hz, 1H), 3.86 (br s, 1H), 3.82 (br s, 1H),
2.01 (q, J¼6.8 Hz, 2H), 1.78 (s, 3H), 1.41–1.28 (m, 4H),
1.27 (d, J¼6.4 Hz, 3H), 0.87 (t, J¼6.8 Hz, 3H); 13C NMR
(CDCl3, 67.8 MHz) d 158.6, 132.2, 131.5, 83.1, 73.5, 32.4,
31.8, 22.6, 22.1, 21.6, 14.4. Exact EIMS calcd for
C11H20O: 168.1514. Found: 168.1514.
4.4. General procedure for the Cr(TPP)Cl-catalyzed
Claisen rearrangements of allyl vinyl ethers to g,d-
unsaturated carbonyl compounds
The catalyst Cr(TPP)Cl was dried over silica gel for 10 h un-
der a reduced pressure (1 mmHg) at 100 ꢀC just before its
use. To a round bottle flask (5 mL) equipped with a three-
way stopcock and a stirring bar were successively added an
allyl vinyl ether (1 mmol), a freshly distilled 1,2-dichloro-
ethane (3 mL), and Cr(TPP)Cl (35 mg, 0.05 mmol). The
mixture was stirred at 83 ꢀC under an argon atmosphere.
After completion of the reaction (monitored by TLC analy-
sis), the solution was directly passed through a silica gel
column (AcOEt/n-hexane ¼ 1:50) to give the corresponding
Claisen rearrangement product. The configurations of the
double bonds in the products were established by compari-
son of their 1H and 13C NMR data with those of g,d-unsatu-
rated aldehydes or ketones with E-configuration, which were
prepared from non-catalytic thermal Claisen rearrangement
reactions of the corresponding allyl vinyl ethers in dichloro-
ethane at 83 ꢀC (the reaction time, yields, and E/Z ratios are
listed in the footnotes of Tables 2–4).21 The following
obtained g,d-unsaturated aldehydes and ketones are known
compounds: (E)-1,3-diphenylhex-4-en-1-one (E-2c),22 3-
phenylpent-4-enal (2d),5d 4-phenylhex-5-en-2-one (2e),23
(E)-5-phenylpent-4-enal (4b),5d (E)-4-propenyloctan-2-one
(E-4d),24 and 3,3-dimethyl-1-phenylpent-4-en-1-one (6c).25
4.3. Preparation of a-styryl ether of allylic alcohols by
methylenation of esters with a Zn–TiCl4–TMEDA
reagent system20
Under an argon atmosphere, 2.0 M solution of TiCl4
(4 mmol) in dichloromethane was added to THF (10 mL)
at 0 ꢀC. After the resulting yellow suspension was warmed
to 25 ꢀC, TMEDA (1.2 mL, 8 mmol) was added. The brown
solution was stirred for 10 min, and then acid washed zinc
powder (1.6 g, 9 mmol) was added at 25 ꢀC. After being
stirred at 25 ꢀC for 30 min, the color of the suspension
changed from dark brown to dark greenish blue. Dibromo-
methane (0.15 mL, 2.1 mmol) and a solution of the ester
(1.0 mmol) in THF (1 mL) were added to the mixture. The
color of the resulting mixture gradually turned to dark brown
while being stirred at 25 ꢀC for 2 h. After hydrolysis with a
saturated K2CO3 solution (1.3 mL) at 0 ꢀC, the reaction mix-
ture was diluted with ether (5 mL) and filtered through a
short column of alumina (Merck Aluminum Oxide 90 active
basic, activity III) using pentane as a solvent. The solvent
was removed under a reduced pressure and the residue was
purified by column chromatography on alumina (Merck
Aluminum Oxide 90 active basic, activity III) using n-hex-
ane/Et3N (200:1) as an eluent to give the corresponding allyl
vinyl ethers in 45–20% yields.
4.4.1. 3-Phenylhex-4-enal (2a) (E/Z¼15:85).12 Colorless
oil; 1H NMR (CDCl3, 300 MHz) d 9.71 (t, J¼2.2 Hz,
1Hꢁ0.85, CHO in (Z)-2a), 9.70 (t, J¼2.0 Hz, 1Hꢁ0.15,
CHO in (E)-2a), 7.33–7.17 (m, 5H), 5.64–5.46 (m, 2H,
CH]CH), 4.24 (q, J¼8.2 Hz, 1Hꢁ0.85, PhCH in (Z)-2a),
3.89 (q, J¼7.3 Hz, 1Hꢁ0.15, PhCH in (E)-2a), 2.87–2.69
(m, 2H), 1.67 (d, J¼5.1 Hz, 3Hꢁ0.85, CH3 in (Z)-2a),
1.67 (d, J¼5.9 Hz, 3Hꢁ0.15, CH3 in (Z)-2a); 13C NMR
(CDCl3, 100 MHz) for (E)-2a: d 201.3, 142.9, 132.9,
128.6, 127.3, 126.5, 125.9, 49.3, 42.9, 18.0; 13C NMR
(CDCl3, 100 MHz) for (Z)-2a: d 201.1, 143.2, 132.1,
128.6, 126.9, 126.4, 125.0, 50.1, 37.4, 14.3; IR (neat)
2866, 1725, 1603, 1493, 1454, 758, 719, 700 cmꢂ1. Exact
EIMS calcd for C12H14O: 174.1045. Found: 174.1047.
4.3.1. (E)-1-Phenyl-3-(a-styryl)oxybut-1-ene (1c). Color-
less oil; H NMR (CDCl3, 300 MHz) d 7.65–7.59 (m, 2H),
1
7.39–7.18 (m, 8H), 6.58 (d, J¼16.1 Hz, 1H), 6.27 (dd,
J¼16.1 and 6.2 Hz, 1H), 4.86 (dq, J¼6.2 and 6.2 Hz, 1H),
4.70 (d, J¼2.7 Hz, 1H), 4.29 (d, J¼2.7 Hz, 1H), 1.52 (d,
J¼6.4 Hz, 3H); 13C NMR (CDCl3, 100 MHz) d 158.2,
136.8, 136.5, 130.6, 130.1, 128.4, 128.2, 127.9, 127.5,
126.3, 125.4, 84.8, 73.9, 21.5. Exact EIMS calcd for
C18H18O: 250.1358. Found: 250.1357.
4.3.2. 2-(a-Styryl)oxyoct-3-ene (3e). Colorless oil; 1H
NMR (CDCl3, 300 MHz) d 7.58–7.53 (m, 2H), 7.29–7.22
(m, 3H), 5.61 (dt, J¼15.6 and 6.5 Hz, 1H), 5.46 (dd,
4.4.2. 4-Phenylhept-5-en-2-one (2b) (E/Z¼69:31). Color-
1
less oil; H NMR (CDCl3, 300 MHz) d 7.30–7.14 (m, 5H),
5.60–5.37 (m, 2H, CH]CH), 4.19 (q, J¼7.5 Hz,

9472
T. Takanami et al. / Tetrahedron 62 (2006) 9467–9474
1Hꢁ0.31, PhCH in (Z)-2b), 3.82 (q, J¼7.2 Hz, 1Hꢁ0.69,
PhCH in (E)-2b), 2.81–2.78 (m, 2H), 2.07 (s, 3Hꢁ0.31,
COCH3 in (Z)-2b), 2.06 (s, 3Hꢁ0.69, COCH3 in (E)-2b),
1.68 (d, J¼5.1 Hz, 3Hꢁ0.31, CH]CHCH3 in (Z)-2b),
4.4.6. (E)-3-Methyl-5-phenylpent-4-enal (4a). Colorless
1
oil; H NMR (CDCl3, 300 MHz) d 9.76 (t, J¼2.2 Hz, 1H,
CHO), 7.34–7.17 (m, 5H), 6.40 (d, J¼15.9 Hz, 1H, CH]
CH–Ph), 6.14 (dd, J¼15.9 and 7.3 Hz, 1H, CH]CH–Ph),
2.99–2.89 (m, 1H, MeCH), 2.59–2.38 (m, 2H), 1.16 (d,
J¼6.8 Hz, 3H, CH3); 13C NMR (CDCl3, 67.8 MHz)
d 202.1, 137.1, 133.9, 129.1, 128.5, 127.3, 126.1, 50.4,
31.9, 20.4; IR (neat) 694, 750, 969, 1073, 1450, 1493,
1601, 1725, 2968 cmꢂ1. Exact EIMS calcd for C12H14O:
174.1045. Found: 174.1048.
1.63 (d, J¼6.2 Hz, 3Hꢁ0.69, CH]CHCH3 in (E)-2b); 13
C
NMR (CDCl3, 100 MHz) for (E)-2b: d 207.0, 143.6,
133.3, 128.4, 127.3, 126.3, 125.3, 49.8, 44.0, 30.7, 18.0;
13C NMR (CDCl3, 100 MHz) for (Z)-2b: d 206.5, 143.6,
132.6, 128.5, 127.0, 126.2, 124.7, 50.5, 44.1, 31.2, 14.3;
IR (neat) 2920, 1717, 1603, 1493, 1454, 1359, 1162, 969,
754, 733, 540 cmꢂ1. Exact EIMS calcd for C13H16O:
188.1201. Found: 188.1199.
4.4.7. 3-Propenylheptanal (4c) (E/Z¼28:72).5d,12 Color-
1
less oil; H NMR (300 MHz, CDCl3) d 9.67 (t, J¼2.4 Hz,
4.4.3. 1,3-Diphenylhex-4-en-1-one (2c) (E/Z¼76:24). Col-
orless oil; 1H NMR (CDCl3, 300 MHz) d 7.93–7.89 (m, 2H),
7.56–7.40 (m, 3H), 7.30–7.14 (m, 5H), 5.68–5.38 (m, 2H,
CH]CH), 4.40 (dt, J¼8.3 and 6.3 Hz, 1Hꢁ0.24, PhCH in
(Z)-2c), 4.05 (dt, J¼7.0 and 7.0 Hz, 1Hꢁ0.76, PhCH in
(E)-2c), 3.42–3.25 (m, 2H), 1.65 (dd, J¼6.3 and 1.4 Hz,
3Hꢁ0.24, m, CH3 in (Z)-2c), 1.62 (ddd, J¼6.3, 1.5, and
1.1 Hz, 3Hꢁ0.76, CH3 in (E)-2c); 13C NMR (CDCl3,
100 MHz) for (E)-2c: d 198.2, 143.9, 137.1, 133.4, 132.8,
128.4, 128.0, 127.9, 127.4, 126.2, 125.4, 44.8, 43.9, 18.1;
13C NMR (CDCl3, 100 MHz) for (Z)-2c: d 197.7, 144.3,
137.1, 133.4, 132.7, 128.5, 128.4, 127.9, 127.1, 126.1,
124.8, 45.7, 38.9, 13.3; IR (neat) 2920, 1688, 1601, 1582,
1493, 1452, 971 cmꢂ1. Exact EIMS calcd for C18H18O:
250.1358. Found: 250.1361. Anal. calcd for C18H18O: C,
86.36; H, 7.25; O, 6.39. Found: C, 86.47; H, 7.33.
1Hꢁ0.28, CHO in (E)-4c), 9.66 (t, J¼2.4 Hz, 1Hꢁ0.72,
CHO in (Z)-4c), 5.49 (ddq, J¼10.4, 6.8, and 0.9 Hz,
1Hꢁ0.72, CH]CH–Me in (Z)-4c), 5.45 (ddq, J¼15.2,
5.9, and 0.7 Hz, 1Hꢁ0.28, CH]CH–Me in (E)-4c), 5.24
(ddq, J¼15.2, 8.3, and 1.5 Hz, 1Hꢁ0.28, CH]CH–Me in
(E)-4c), 5.13 (ddq, J¼10.4, 10.4, and 1.8 Hz, 1Hꢁ0.72,
CH]CH–Me in (Z)-4c), 2.97–2.84 (m, 1Hꢁ0.72, BuCH
in (Z)-4c), 2.58–2.48 (m, 1Hꢁ0.28, BuCH in (E)-4c),
2.44–2.23 (m, 2H), 1.63 (dd, J¼5.9 and 1.7 Hz, 3Hꢁ0.32,
CH]CH–CH3 in (E)-4c), 1.62 (dd, J¼6.8 and 1.6 Hz,
3Hꢁ0.72, CH]CH–CH3 in (Z)-4c), 1.36–1.14 (m, 6H),
0.86 (t, J¼6.8 Hz, 3H); 13C NMR (CDCl3, 100 MHz) for
(E)-4c: d 202.7, 133.6, 125.7, 49.2, 37.6, 35.1, 29.3, 22.7,
18.0, 14.2; 13C NMR (CDCl3, 100 MHz) for (Z)-4c:
d 202.4, 133.2, 124.7, 49.7, 37.6, 35.4, 29.4, 22.8, 18.0,
14.2; IR (neat) 1729, 1460, 1408, 1379, 1263, 1067, 969,
932, 803, 729 cmꢂ1. Exact EIMS calcd for C10H18O:
154.1358. Found: 154.1353.
4.4.4. 3-(4-Methoxyphenyl)hex-4-enal (2f) (E/Z¼38:62).
Colorless oil; 1H NMR (CDCl3, 300 MHz) d 9.68 (t,
J¼2.2 Hz, 1Hꢁ0.62, CHO in (Z)-2f), 9.67 (t, J¼2.2 Hz,
1Hꢁ0.38, CHO in (E)-2f), 7.13 (d, J¼8.7 Hz, 2H), 6.83
(d, J¼8.7 Hz, 2H), 5.58–5.46 (m, 2H, CH]CH), 4.18 (q,
J¼6.8 Hz, 1Hꢁ0.62, ArCH in (Z)-2f), 3.83 (q, J¼7.1 Hz,
1Hꢁ0.38, ArCH in (E)-2f), 3.76 (s, 3H, OCH3), 2.82–2.64
(m, 2H), 1.69 (d, J¼5.1 Hz, 3Hꢁ0.62, CH]CHCH3 in
(Z)-2f), 1.64 (d, J¼5.9 Hz, 3Hꢁ0.38, CH]CHCH3 in (E)-
2f); 13C NMR (CDCl3, 67.8 MHz) for (E)-2f: d 201.9,
158.3, 135.1, 133.3, 128.3, 125.7, 114.1, 55.3, 49.3, 42.0,
17.9; 13C NMR (CDCl3, 67.8 MHz) for (Z)-2f: d 201.7,
158.2, 135.5, 132.6, 128.0, 124.7, 114.0, 55.2, 50.2, 36.5,
13.1; IR (neat) 3828, 2840, 1725, 1611, 1584, 1514, 1251,
1180, 1036, 971, 830 cmꢂ1. Exact EIMS calcd for
C13H16O2: 204.1150. Found: 204.1149.
4.4.8. 4-Propenyloctan-2-one (4d) (E/Z¼77:23). Colorless
oil; 1H NMR (CDCl3, 300 MHz) d 5.51–5.34 (m, 1H,
CH]CH–Me), 5.19 (ddq, J¼15.2, 8.3, and 1.6 Hz,
1Hꢁ0.77, CH]CH–Me in (E)-4d), 5.08 (ddq, J¼9.9, 9.9,
and 1.8 Hz, 1Hꢁ0.23, CH]CH–Me in (Z)-4d), 2.93–2.80
(m, 1Hꢁ0.23, BuCH in (Z)-4d), 2.50–2.43 (m, 1Hꢁ0.77,
BuCH in (E)-4d), 2.42–2.26 (m, 2H), 2.09 (s, 3Hꢁ0.23,
COCH3 in (Z)-4d), 2.08 (s, 3Hꢁ0.77, COCH3 in (E)-4d),
1.61 (dd, J¼6.2 and 1.6 Hz, 3Hꢁ0.77, CH]CH–CH3 in
(E)-4d), 1.61 (dd, J¼7.0 and 1.5 Hz, 3Hꢁ0.23, CH]CH–
CH3 in (Z)-4d), 1.31–1.18 (m, 6H), 0.86 (t, J¼6.4 Hz,
3H); 13C NMR (CDCl3, 100 MHz) for (E)-4d: d 208.3,
133.9, 125.2, 49.9, 38.8, 35.1, 30.6, 29.4, 22.8, 18.0, 14.2;
13C NMR (CDCl3, 100 MHz) for (Z)-4d: d 208.2, 133.7,
124.4, 50.2, 38.8, 35.4, 30.7, 29.5, 22.9, 18.0, 13.3; IR
(neat) 729, 969, 1166, 1359, 1458, 1717, 2930 cmꢂ1. Exact
EIMS calcd for C11H20O: 168.1514. Found: 168.1514.
4.4.5. 3-(p-Tolyl)hex-4-enal (2g) (E/Z¼39:61). Colorless
oil; 1H NMR (CDCl3, 300 MHz) d 9.68 (t, J¼2.2 Hz,
1Hꢁ0.61, CHO in (Z)-2g), 9.68 (t, J¼2.2 Hz, 1Hꢁ0.39,
CHO in (E)-2g), 7.16–7.04 (m, 4H), 5.58–5.47 (m, 2H,
CH]CH), 4.19 (q, J¼6.6 Hz, 1Hꢁ0.61, ArCH in (Z)-2g),
3.84 (q, J¼7.3 Hz, 1Hꢁ0.39, ArCH in (E)-2g), 2.84–2.66
(m, 2H), 2.30 (s, 3H, ArCH3), 1.69 (d, J¼5.1 Hz,
3Hꢁ0.61, CH]CHCH3 in (Z)-2g), 1.64 (d, J¼5.9 Hz,
3Hꢁ0.39, CH]CHCH3 in (E)-2g); 13C NMR (CDCl3,
67.8 MHz) for (E)-2g: d 201.9, 140.0, 136.2, 133.2, 129.4,
127.2, 125.8, 49.2, 42.4, 21.0, 17.9; 13C NMR (CDCl3,
67.8 MHz) for (Z)-2g: d 201.7, 158.6, 135.9, 128.3, 128.0,
124.7, 114.1, 55.2, 50.2, 36.5, 13.1; IR (neat) 2924, 2728,
1721, 1516, 1452, 1417, 1381, 1112, 1044, 1021, 969,
816 cmꢂ1. Exact EIMS calcd for C13H16O: 188.1201.
Found: 188.1202.
4.4.9. 1-Phenyl-3-propenylheptan-1-one (4e) (E/Z¼
1
80:20). Colorless oil; H NMR (CDCl3, 300 MHz) d 7.92–
7.89 (m, 2H), 7.55–7.40 (m, 3H), 5.48–5.34 (m, 1H,
CH]CH–Me), 5.26 (ddq, J¼15.1, 7.9, and 1.5 Hz,
1Hꢁ0.8, CH]CH–Me in (E)-4e), 5.14 (ddq, J¼10.8,
10.8, and 1.8 Hz, 1Hꢁ0.2, CH]CH–Me in (Z)-4e), 3.11–
3.00 (m, 1Hꢁ0.2, BuCH in (Z)-4e), 2.91 (d, J¼7.4 Hz,
2H, PhCOCH2), 2.70–2.59 (m, 1Hꢁ0.8, BuCH in (E)-4e),
1.59 (dd, J¼6.2 and 1.3 Hz, 3Hꢁ0.8, CH]CH–CH3 in
(E)-4e), 1.54 (dd, J¼6.8 and 1.8 Hz, 3Hꢁ0.2, CH]CH–
CH3 in (E)-4e), 1.45–1.17 (m, 6H), 0.86 (t, J¼6.8 Hz, 3H);
13C NMR (CDCl3, 100 MHz) for (E)-4e: d 199.6, 137.4,
134.2, 132.6, 128.3, 128.0, 125.1, 44.7, 39.0, 35.0, 29.5,

T. Takanami et al. / Tetrahedron 62 (2006) 9467–9474
9473
22.8, 18.0, 14.2; 13C NMR (CDCl3, 100 MHz) for (Z)-4e:
d 199.5, 137.4, 134.1, 133.9, 132.5, 125.0, 124.3, 44.8,
38.9, 35.5, 29.5, 22.9, 18.0, 13.3; IR (neat) 3018, 2808,
1688, 1599, 1582, 1450, 967, 752, 690, 572 cmꢂ1. Exact
EIMS calcd for C16H22O: 230.1671. Found: 230.1672.
3. For a review, see: Hiersemann, M.; Abraham, L. Eur. J. Org.
Chem. 2002, 1461–1471.
4. For selected works, see: (a) Nevado, C.; Echavarren, A. M.
Tetrahedron 2004, 60, 9735–9744; (b) Akiyama, K.; Mikami,
K. Tetrahedron Lett. 2004, 45, 7217–7220; (c) Hiersemann,
M. Synlett 1999, 1823–1825; (d) Sugiura, M.; Nakai, T.
Chem. Lett. 1995, 697–698.
4.4.10. (E)-3-Methyl-3-propenylheptanal (6a). Colorless
1
5. (a) Maruoka, K. Lewis Acid Reagents; Yamamoto, H., Ed.;
Oxford: New York, NY, 1999; Chapter 2, pp 5–29; (b) Takai,
K.; Mori, I.; Oshima, K.; Nozaki, H. Bull. Chem. Soc. Jpn.
1984, 57, 446–451; (c) Maruoka, K.; Nonoshita, K.; Banno,
H.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 7922–7924;
(d) Nonoshita, K.; Banno, H.; Maruoka, K.; Yamamoto, H.
J. Am. Chem. Soc. 1990, 112, 316–322; (e) Saito, S.; Shimada,
K.; Yamamoto, H. Synlett 1996, 720–722; (f) Maruoka, K.;
Banno, H.; Yamamoto, H. J. Am. Chem. Soc. 1990, 112,
7791–7793; (g) Maruoka, K.; Saito, S.; Yamamoto, H. J. Am.
Chem. Soc. 1995, 117, 1165–1166; (h) Ooi, T.; Takahashi,
M.; Maruoka, K. J. Am. Chem. Soc. 1996, 118, 11307–
11308; (i) Tayama, E.; Saito, A.; Ooi, T.; Maruoka, K.
Tetrahedron 2002, 58, 8307–8312.
oil; H NMR (CDCl3, 300 MHz) d 9.69 (t, J¼3.2 Hz, 1H,
CHO), 5.46 (d, J¼15.6 Hz, CH]CH–Me), 5.38 (dq,
J¼15.6 and 4.9 Hz, CH]CH–Me), 2.32 (dd, J¼14.7 and
3.2 Hz, 1H), 2.22 (dd, J¼14.7 and 3.2 Hz, 1H), 1.67 (d,
J¼4.9 Hz, 3H, CH]CH–CH3), 1.36–1.08 (m, 6H), 1.08
(s, 3H), 0.87 (t, J¼6.9 Hz, 3H); 13C NMR (CDCl3,
67.8 MHz) d 204.1, 138.1, 123.2, 53.7, 41.8, 38.1, 26.1,
24.2, 23.3, 18.1, 14.1; IR (neat) 2934, 1723, 1458, 1381,
975 cmꢂ1. Exact EIMS calcd for C11H20O: 168.1514.
Found: 168.1510.
4.4.11. (E)-3-Methyl-3-phenylhex-4-enal (6b). Colorless
1
oil; H NMR (CDCl3, 300 MHz) d 9.56 (t, J¼3.0 Hz, 1H),
7.39–7.17 (m, 5H), 5.71 (dq, J¼15.5 and 1.5 Hz, 1H,
CH]CH–Me), 5.51 (dq, J¼15.5 and 6.3 Hz, 1H,
CH]CH–Me), 2.78 (dd, J¼15.2 and 2.9 Hz, 1H), 2.71
(dd, J¼15.2 and 2.9 Hz, 1H), 1.73 (dd, J¼6.3 and 1.5 Hz,
3H, CH]CH–CH3), 1.49 (s, 3H); 13C NMR (CDCl3,
67.8 MHz) d 203.3, 146.4, 138.0, 128.5, 126.4, 126.2,
123.7, 53.8, 42.1, 26.8, 18.1; IR (neat) 2972, 1721, 1448,
1495, 1379, 1035, 975, 762, 700 cmꢂ1. Exact EIMS calcd
for C13H16O: 188.1201. Found: 188.1200.
6. Nakamura, S.; Ishihara, K.; Yamamoto, H. J. Am. Chem. Soc.
2000, 122, 8131–8140.
7. (a) Trost, B. M.; Schroeder, G. M. J. Am. Chem. Soc. 2000,
122, 3785–3786; (b) Hiersemann, M.; Abraham, L. Org.
Lett. 2001, 3, 49–52; (c) Abraham, L.; Czerwonka, R.;
Hiersemann, M. Angew. Chem., Int. Ed. 2001, 40, 4700–
4703; (d) Helmboldt, H.; Hiersemann, M. Tetrahedron 2003,
59, 4031–4038.
8. For a mechanistic discussion, see: Gajewski, J. J. Acc. Chem.
Res. 1997, 30, 219–225.
Acknowledgements
9. Nasveschuk, C. G.; Rovis, T. Org. Lett. 2005, 7, 2173–2176.
10. For some examples of works on Lewis acid-mediated [1,3] re-
arrangement of allyl vinyl ethers, see: (a) Grieco, P. A.; Clark,
J. D.; Jagoe, C. T. J. Am. Chem. Soc. 1991, 113, 5488–5489; (b)
Gansauer, A.; Fielenbach, D.; Stock, C. Adv. Synth. Catal.
2002, 344, 845–848; (c) Gansaeuer, A.; Fielenbach, D.;
Stock, C.; Geich-Gimbel, D. C. Adv. Synth. Catal. 2003, 345,
1017–1030; (d) Nasveschuk, C. G.; Rovis, T. Angew. Chem.,
Int. Ed. 2005, 44, 3264–3267.
11. Yamamoto and Maruoka briefly mentioned in their paper
that these bulky organo aluminum-mediated Claisen rear-
rangements do not entirely proceed through a [3,3] concerted
pathway: certain substrates, such as 1-phenyl-2-propenyl
vinyl ether 3b, undergo the [1,3] rearrangement in competi-
tion to the normal [3,3] Claisen rearrangement (see Refs.
5b,c,e).
This work was supported by a Grant-in-Aid for Scientific
Research (KAKENHI) from JSPS and a Special Grant (GA-
KUCHO-GRANT) from Meiji Pharmaceutical University.
References and notes
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that can promote regio- and stereoselective isomerization
of epoxides to carbonyl compounds, see: (a) Suda, K.;
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ˇ
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