Pentadienyl transfer reagents based on zirconium: Preparation and reactions with carbonyl compounds

Article abstract of DOI:10.1016/j.tet.2003.08.065

A variety of 2,4-pentadienylzirconiums were generated by reacting pentadienyl ethers with zirconocene 'Cp₂Zr'. These complexes underwent a highly γ-regioselective and anti-stereoselective in situ addition with carbonyl compounds to afford bis(h

Full text of DOI:10.1016/j.tet.2003.08.065

Tetrahedron 60 (2004) 1375–1383
Pentadienyl transfer reagents based on zirconium: preparation
and reactions with carbonyl compounds
*
Philippe Bertus, Ludovic Drouin, Christophe Laroche and Jan Szymoniak
´ ´ ´
Reactions Selectives et Applications (UMR 6519), CNRS and Universite de Reims, 51687 Reims Cedex 2, France
Received 26 June 2003; revised 28 August 2003; accepted 31 August 2003
Abstract—A variety of 2,4-pentadienylzirconiums were generated by reacting pentadienyl ethers with zirconocene ‘Cp2Zr’. These
complexes underwent a highly g-regioselective and anti-stereoselective in situ addition with carbonyl compounds to afford bis(homoallylic)
alcohols in good yields. The reversal of anti vs syn selectivity was simply achieved with BF3, thus expanding the synthetic potential of the
reaction.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
chemical outcome of the pentadienylation reactions is
shown in Scheme 1.
Allylmetals are important reagents for the stereoselective
carbon–carbon bond-forming reactions.1 Particularly, they
react with carbonyl compounds to produce homoallylic
alcohols, which are useful synthetic intermediates. In
contrast, the analogous 2,4-pentadienylmetals employing
reactions have been much less investigated.2 The regio-
When the reaction occurs at the 1 (or a)-carbon in the
complex, a linear alcohol is formed, whereas at the g-carbon
a branched alcohol is obtained. The regioselectivity of these
reactions has been demonstrated to vary with the metal.2
Whereas lithium, potassium and magnesium generally give
poor regioselectivity, the addition at the g-position
preferentially occurs with indium, titanium, boron, zinc or
chromium, and at the 1-position with silicon and tin.
Furthermore, the stereoselectivity of the pentadienylation
reactions have not been studied systematically. Both anti
Scheme 1.
Scheme 2.
Keywords: Homoallylic alcohols; Pentadienylation reaction; Stereocontrol; Zirconium.
*
Corresponding author. Fax: þ33-326-913-166; e-mail address: jan.szymoniak@univ-reims.fr
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.08.065

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P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
and/or syn diastereoselectivity have been observed depend-
ing on the metal.
2. Results and discussion
It is known that allylic ethers react with (1-butene)zircono-
cene5 to afford allylzirconium derivatives.6 The reaction
occurs through ligand exchange, formation of a zircona-
cyclopropane and the successive b-elimination of the
alkoxy group (Scheme 2, Eq. (1)).
Pentadienylmetals are typically prepared by transmetalation
from lithium or potassium pentadienyl precursors or by
Barbier-type reactions from the corresponding pentadienyl
bromides. The synthetic potential of pentadienylmetals
would be considerably enhanced if these complexes could
be prepared from chemically more stable and readily
available starting materials.3 With this aim in view we
have reported a preliminary work on a simple and
practical way of preparing pentadienylzirconocenes from
dienyl ethers.4 These complexes proved to react with
aldehydes in the g-selective manner. We disclose herein
a full account on the reactions involving pentadienyl-
zirconium reagents.
We have demonstrated that, analogously, pentadienylzirco-
nium compounds could be generated from dienyl ethers
(Scheme 2, Eq. (2)).7 It is noteworthy that the same complex
B was solely obtained from both the linear ether 1 and the
ramified ether 2. We assumed the zirconium fragment
(Cp2ZrOBn) would migrate in A to a less hindered site of
the allyl moiety, leading to the thermodynamically more
favorable complex B.8 Accordingly, both linear and
Table 1. Zr-mediated pentadienylation of carbonyl compounds
Entry
1
Ether
Carbonyl compound
PhCHO
T (8C)
Producta
Yield (%)b (anti/syn)c
4a
4b
4c
4d
4a
4a
20
5a
5a
5a
5a
5a
5b
96 (86:14)
2
3
4
5
6
PhCHO
20
20
55 (84:16)
94 (87:13)
93 (94:6)
78 (92:8)
83 (93:7)
PhCHO
PhCHO
20
PhCHO
278
278
MeCHvCHCHO
7
4a
PhCHvCHCHO
278
5c
93 (92:8)
8
4a
4a
4a
4a
EtCHO
278
278
278
278
5d
5e
5f
57 (.95:5)
64 (.95:5)
81 (2)
9
i-PrCHO
d
10
(HCHO)n
11
Me2CO
5g
70 (2)
a
Only the major stereoisomer is shown.
Isolated yield.
b
c
d
1
anti/syn Ratio determinated by H NMR.
Paraformaldehyde was used.

P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
1377
ramified pentadienyl ethers can be employed as starting
materials to form the unique penta-2,4-dienylzirconium
species.
conditions, a high anti/syn ratio remains almost constant
(92:8 to .95:5) for the aromatic, a,b-unsaturated as well as
the aliphatic aldehydes (entries 5–9). Both regio- and
stereochemistry of the reaction are consistent with a
conventional six-membered chair-like transition state, as
proposed for the simpler allylzirconation reactions.1 The
primary alcohol 5f and the tertiary alcohol 5g (a terpene,
santolina alcohol) can finally be obtained by employing
respectively paraformaldehyde and acetone (entries 10
and 11).
The pentadienylzirconocenes were typically formed from
the pentadienyl ether, Cp2ZrCl2 and 2n-BuLi by applying
the Taguchi protocol for the formation of allylzircono-
cenes6d or better by a modified procedure.4,9 The zirconium
species thus generated were further used for the penta-
dienylation reactions. In the first experiment, the preformed
complex B was reacted with benzaldehyde to produce the
alcohol 3 regioselectively, in 60–70% yield (Scheme 2).4
To investigate both the regio- and the stereoselectivity of the
reaction we next used the pentadienyl ethers 4a–d and
various carbonyl compounds as substrates. The results are
summarized in Table 1.
2.2. Ether components
The synthetic utility of the reaction is also displayed by the
possible use of various penta-1,4-dienyl ethers as substrates.
Both 1- and 2-substituted pentadienyl ethers were
employed, and the examples of these reactions are depicted
in Table 2.
2.1. Temperature and structure effects on
stereoselectivity
As for the non-substituted and 1,1-disubstituted pentadienyl
ether, also in these cases g-regioisomers were obtained
solely in good yields. All the reactions involving 1-substi-
tuted ethers (entries 1–4) proceeded with a high anti
diastereoselectivity (anti/synh 95:5). The high level of anti
selection appeared to be independent both of the nature of
the aldehyde (aromatic, a,b-unsaturated or aliphatic, entries
1–3, respectively), and of the alkoxy group in the ether
(X¼Sit-BuMe2 or Bn, entries 1–3 vs 4). We observed a
partial E to Z isomerization of the double bond in alcohols
7d and 7e derived from the ether 6b. Finally, only a
moderate decrease in anti selectivity has been noticed when
using a 2-substituted ether instead of the 1-substituted
analogue (alcohols 7d and 7f, entries 4 and 6).
In all cases the reaction occurred regioselectively at the
g-carbon of the complex to afford the branched alcohols
5a–g solely. Furthermore, the pentadienylation of the
aldehydes appeared to be markedly anti-stereoselective.10
The stereoselectivity of the reaction employing PhCHO can
slightly be increased by introducing a bulky OX group in
the ether. Whereas the diastereomeric ratio remains almost
constant for X¼Bn, Me and Sit-BuMe2 (entries 1–3), an
improvement in the anti diastereoselection was observed for
X¼Sit-BuPh2 (entry 4). The stereoselectivity of the reaction
was increased further by adding the aldehyde at 278 8C
rather than at 20 8C. Two examples employing the ether 4a
and benzaldehyde are given (entries 1 and 5). In these
Table 2. Zr-mediated pentadienylations (following)
Entry
1
Ether
Aldehyde
Producta
Yield (%)b (anti/syn)c
90 (.95:5)
6a
PhCHO
7a
2
3
6a
6a
PhCHvCHCHO
7b
7c
81 (.95:5)
EtCHO
90 (93:7)
4
5
6b
6b
PhCHO
7d
7e
85 (.95:5)d
62 (2)e
(HCHO)n
6
6c
PhCHO
7f
76 (88:12)
a
Only the major stereoisomer is shown.
Isolated yield.
b
c
d
e
anti/syn Ratio determinated by 1H NMR.
E/Z isomers¼80:20.
E/Z isomers¼71:29.

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P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
Scheme 3.
2.3. Reversal of anti to syn diastereoselectivity
At this stage, the synthetic limitation of the pentadienylation
reactions lied in their invariably predominant anti stereo-
chemistry. We made efforts to control the stereochemistry
of these reactions, i.e. to ensure that it could be reversed
leading mainly to the syn configurated alcohols. The anti
stereochemistry can be explained by assuming a conven-
tional six-membered chair-like transition state, as for the
simpler allylzirconation reactions (Scheme 3). We then
examinated whether it was possible to modify the reaction
conditions to favour a non-cyclic mechanism1 over the
cyclic one.
Scheme 4.
carbonyl compounds was observed by Reetz.11 The
predominant syn selectivity in the presence of a Lewis
acid was considered to be consistent with a non-cyclic
antiperiplanar transition state.14 We assumed tentatively,
that also in our case, the reversal of anti to syn selectivity
can be explained by a non-cyclic mechanism operating with
BF3 as presented in Scheme 4.15
Lewis acids11 and polar solvents, especially HMPA,12 have
been shown to affect the stereochemistry of the reactions
originally proceeding through a six-membered transition
state. We first examined the effect of HMPA as co-solvent
and noticed that no change in stereochemistry took place.
To promote a non-cyclic mechanism for the pentadienyla-
tion reactions, we then turned to the use of a Lewis acid.
After the complex had been generated, BF3·OEt2 (1 equiv.)
was added at 278 8C, followed by the aldehyde, and the
reaction mixture was allowed to warm to 20 8C. We noticed
that a reversal of anti to syn stereoselectivity took place by
applying this modified procedure (Procedure B, Section
3).13 The results of the reactions with or without BF3,
employing ethers 4a and 6a–c, as well as the aromatic,
a,b-unsaturated and aliphatic aldehydes are summarized in
Table 3.
A higher syn selectivity for the aromatic or unsaturated than
for the aliphatic aldehydes is not entirely clear at present.
This could possibly be rationalized by additional destabili-
zing p–p interactions in the transition structure C, thus
favouring all the more D. However, the mechanism of the
Lewis acid-mediated reactions could even be more
complicated.16 Systematic mechanistic studies are needed
to fully elucidate the effect of Lewis acids on the
stereoselectivity.
In summary, we have presented a practical procedure for
preparing bis(homoallylic) alcohols in a highly g-regio-
selective and anti-stereoselective manner. Furthermore, in
the presence of a Lewis acid, the stereochemistry can be
reversed leading predominantly to the syn-configurated
products.
We noticed that a spectacular reversal of anti to syn
stereoselectivity invariably took place when using the
aromatic or a,b-unsaturated aldehydes, i.e. benzaldehyde
(entries 1, 6, 9, and 10), cinnamaldehyde (entries 3 and 7)
and crotonaldehyde (entry 2). In contrast, the effect of
modifying the stereoselectivity was only moderate for the
aliphatic aldehydes (entries 4, 5, and 8).
3. Experimental
3.1. General
The Lewis acid-induced reversal of anti to syn stereo-
selectivity in the reactions of h1-allyltitaniums with
All reactions were conducted under an atmosphere of dry
Table 3. Effect of BF3·OEt2 on the anti vs syn diastereoselectivity
Entry
Ether
Carbonyl compound
Product
anti/syna
BF3·OEt2 anti/syna
1
2
3
4
5
6
7
8
9
10
4a
4a
4a
4a
4a
6a
6a
6a
6b
6c
PhCHO
5a
5b
5c
5d
5e
7a
7b
7c
7d
7f
92:8
93:7
92:8
.95:5
.95:5
.95:5
.95:5
93:7
26:74
18:82
20:80
68:32
57:43
16:84
18:82
50:50
21:79
35:65b
MeCHvCHCHO
PhCHvCHCHO
EtCHO
i-PrCHO
PhCHO
PhCHvCHCHO
EtCHO
PhCHO
.95:5
88:12
PhCHO
a
1
anti/syn Ratio determinated by H NMR.
1-Addition product, i.e. 3-methyl-1-phenylhexa-3,5-dien-1-ol (8), was also formed in 29% yield.
b

P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
1379
argon using standard Schlenk techniques. 1H and 13C NMR
140.7 (CH). IR (film): n (cm21)¼2947, 2864, 1466 cm21
.
spectra were recorded in CDCl3 on a Bruker AC-250 or
DRX-500 spectrometer. IR spectra were recorded on a
Nicolet Avatar 320 instrument. Mass spectra were recorded
on a ThermoFinnigan Trace MS spectrometer. Cp2ZrCl2
and vinylmagnesium bromide reagents were used as
received. n-BuLi was titrated with diphenylacetic acid in
THF prior to use. Tetrahydrofuran was distilled from
sodium benzophenone ketyl prior to use.
MS (EI): m/z (%)¼211 (3, M2Me), 169 (50, M2t-Bu), 95
(22), 75 (100).
3.2.4. 4-t-Butyldiphenylsilyloxy-2-methylhexa-2,5-diene
1
(4d). H NMR (250 MHz): d (ppm)¼1.05 (s, 9H), 1.14 (s,
3H), 1.57 (s, 3H), 4.76–4.84 (m, 1H), 4.99 (dt, J¼10.3,
1.5 Hz, 1H), 5.10–5.20 (m, 2H), 5.82 (ddd, J¼17.1, 10.3,
5.2 Hz, 1H), 7.30–7.46 (m, 6H), 7.65–7.74 (m, 4H). 13C
NMR (63 MHz): d (ppm)¼17.8 (CH3), 19.3 (C), 25.5
(CH3), 26.9 (CH3), 71.5 (CH), 112.7 (CH2), 127.0 (CH),
127.2 (CH), 127.4 (CH), 129.3 (CH), 129.4 (CH), 132.5 (C),
134.2 (C), 134.3 (C), 135.9 (CH), 136.0 (CH), 140.3 (CH).
IR (film): n (cm21)¼3072, 2926, 2844, 1676, 1641, 1591.
MS (EI): m/z (%)¼293 (30, M2t-Bu), 199 (100).
3.2. Preparation of ethers
3.2.1. 4-Benzyloxy-2-methylhexa-2,5-diene (4a). A solu-
tion of 3-methylbut-2-enal (7.7 mL, 80 mmol) in THF
(20 mL) was added dropwise at room temperature to a
solution of vinylmagnesium bromide (100 mL, 100 mmol,
1.0 M in THF) in THF (50 mL). After stirring for 1 h, 5 mL
of water was added to the reaction mixture to produce a
viscous paste in the walls of the flask. The organic layer was
separated. The paste was washed twice with Et2O. The
combined organic phases were dried over MgSO4. Filtration
and removal of the solvent gave 8.5 g (95%) of the crude
alcohol which was sufficiently pure (according to NMR) to
be used in the next step. NaH (0.87 g, 36 mmol, oil removed
by washing with pentane) was added to a solution of the
crude alcohol (3.36 g, 30 mmol) in THF (30 mL). After
stirring for 1 h, benzyl bromide (3.36 mL, 30 mmol) was
added. After stirring overnight, water was poured into the
mixture and extracted twice with Et2O. The combined
organic phases were dried over MgSO4. Filtration and
removal of the solvent gave a light yellow oil which was
purified by column chromatography (silica gel, petroleum
ether/ethyl acetate 99:1). Yield 4.36 g (72%). 1H NMR
(250 MHz): d (ppm)¼1.65 (s, 3H), 1.79 (s, 3H), 4.51 (s,
2H), 4.52–4.58 (m, 1H), 5.15–5.29 (m, 3H), 5.86 (ddd,
J¼17.3, 10.3, 6.7 Hz, 1H), 7.25–7.39 (m, 5H). 13C NMR
(63 MHz): d (ppm)¼18.3 (CH3), 25.9 (CH3), 69.3 (CH2),
76.5 (CH), 115.7 (CH2), 124.3 (CH), 127.3 (CH), 127.7
(CH), 128.2 (CH), 136.2 (C), 138.1 (CH), 138.7 (C). IR
(film): n (cm21)¼3064, 2859, 1672, 1454, 1380. MS (EI):
m/z (%)¼202 (1, Mþz), 108 (64), 94 (64), 79 (100).
3.2.5. 3-t-Butyldimethylsilyloxy-1-phenylpenta-1,4-diene
(6a). A solution of cinnamaldehyde (7.5 mL, 60 mmol) in
THF (20 mL) was added dropwise at room temperature to a
solution of vinylmagnesium bromide (80 mL, 80 mmol,
1.0 M in THF) in THF (15 mL). After stirring for 1 h, ca.
5 mL of water was added to the reaction mixture to produce
a viscous paste in the walls of the flask. The organic layer
was separated. The paste was washed twice with Et2O. The
combined organic phases were dried over MgSO4. Filtration
and removal of the solvent followed by purification by
column chromatography (silica gel, petroleum ether/ethyl
acetate 90:10) gave 14.6 g (89%) of 1-phenylpenta-1,4-
1
dien-3-ol. H NMR (250 MHz): d (ppm)¼1.83 (br s, OH),
4.78–4.85 (m, 1H), 5.21 (dd, J¼10.3, 1.0 Hz, 1H), 5.36 (dd,
J¼17.3, 1.0 Hz, 1H), 5.98 (ddd, J¼17.3, 10.3, 6.2 Hz, 1H),
6.25 (dd, J¼16.0, 6.5 Hz, 1H), 6.63 (d, J¼16.0 Hz, 1H),
7.20–7.45 (m, 5H). 13C NMR (63 MHz): d (ppm)¼73.5
(CH), 115.2 (CH2), 126.4 (CH), 127.6 (CH), 128.4 (CH),
130.3 (CH), 130.5 (CH), 136.4 (C), 139.1 (CH). IR (film): n
(cm21)¼3356, 1655, 1597, 1495, 1454. To the alcohol
(0.96 g, 6 mmol) in Et2O (20 mL) was added t-BuMe2SiCl
(1.0 g, 6.6 mmol) and 4-(dimethylamino)pyridine (0.85 g,
6.6 mmol). After stirring overnight, the precipitate was
eliminated by filtration. Removal of the solvent and
purification by column chromatography (silica gel, petro-
leum ether/ethyl acetate 99:1) furnished 1.38 g (84%) of 6a.
1H NMR (250 MHz): d (ppm)¼0.11 (s, 6H), 0.91 (s, 9H),
4.78 (br t, J¼5.6 Hz, 1H), 5.12 (d, J¼10.3 Hz, 1H), 5.29
(d, J¼17.1 Hz, 1H), 5.89 (ddd, J¼17.1, 10.3, 5.4 Hz, 1H),
6.18 (dd, J¼15.9, 5.9 Hz, 1H), 6.56 (d, J¼15.9 Hz, 1H),
7.20–7.41 (m, 5H). 13C NMR (63 MHz): d (ppm)¼24.7
(CH3), 24.6 (CH3), 18.4 (C), 25.9 (CH3), 74.4 (CH), 113.8
(CH2), 126.4 (CH), 127.4 (CH), 128.5 (CH), 129.0 (CH),
Ethers 4b–d were obtained following the procedure
described for the preparation of the ether 4a, by using
MeI, t-BuMe2SiCl and t-BuPh2SiCl, respectively, instead of
BnBr.
1
3.2.2. 4-Methoxy-2-methylhexa-2,5-diene (4b). H NMR
(250 MHz): d (ppm)¼1.70 (s, 3H), 1.77 (s, 3H), 3.28 (s,
3H), 4.32 (t, J¼7.7 Hz, 1H), 5.08–5.27 (m, 3H), 5.77 (ddd,
J¼17.2, 10.3, 6.8 Hz, 1H). 13C NMR (63 MHz): d
(ppm)¼18.3 (CH3), 25.8 (CH3), 55.4 (CH3), 79.0 (CH),
115.7 (CH2), 124.2 (CH), 136.3 (C), 137.9 (CH). IR (film): n
(cm21)¼2975, 1686, 1449, 1378. MS (EI): m/z (%)¼126 (6,
Mþz), 111 (28), 94 (85), 79 (100).
131.6 (CH), 136.9 (C), 140.1 (CH). IR (film):
n
(cm21)¼2956, 2857, 1472, 1252. MS (EI): m/z (%)¼217
(13, M2t-Bu), 143 (35), 142 (30), 81 (100).
3.2.6. (E)-3-Benzyloxyhexa-1,4-diene (6b). Ether 6b was
obtained in 82% yield from crotonaldehyde (two steps)
following the procedure described for the preparation of
ether 4a. 1H NMR (250 MHz): d (ppm)¼1.75 (d, J¼6.3 Hz,
3H), 4.23 (t, J¼6.8 Hz, 1H), 4.51 (s, 2H), 5.20 (d, J¼
10.3 Hz, 1H), 5.26 (d, J¼17.3 Hz, 1H), 5.50 (ddq, J¼15.4,
7.1, 1.5 Hz, 1H), 5.71 (dq, J¼15.4, 6.3 Hz, 1H), 5.85 (ddd,
J¼17.3, 10.3, 6.6 Hz, 1H), 7.25–7.35 (m, 5H). 13C NMR
(63 MHz): d (ppm)¼17.8 (CH3), 69.5 (CH2), 80.6 (CH),
116.3 (CH2), 127.3 (CH), 127.6 (CH), 128.2 (CH), 128.7
3.2.3. 4-t-Butyldimethylsilyloxy-2-methylhexa-2,5-diene
1
(4c). H NMR (250 MHz): d (ppm)¼0.05 (s, 6H), 0.89 (s,
9H), 1.65 (s, 3H), 1.71 (s, 3H), 4.80–4.87 (m, 1H), 4.99 (dd,
J¼10.3, 1.4 Hz, 1H), 5.08–5.22 (m, 2H), 5.80 (ddd, J¼
17.1, 10.3, 5.2 Hz, 1H). 13C NMR (63 MHz): d (ppm)¼
24.7 (CH3), 24.5 (CH3), 18.2 (CH3), 18.3 (C), 25.7 (CH3),
25.9 (CH3), 70.8 (CH), 112.4 (CH2), 127.6 (CH), 131.9 (C),

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P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
(CH), 130.5 (CH), 138.1 (CH), 138.6 (C). IR (film): n
(cm21)¼3029, 2857, 1668, 1454. MS (EI): m/z (%)¼170 (1,
M2H2O), 144 (6), 130 (10), 91 (90), 79 (100).
Syn-5a. 1H NMR (250 MHz): d (ppm)¼1.61 (s, 3H), 1.78 (s,
3H), 2.25 (br s, OH), 3.27 (br q, J¼7.7 Hz, 1H), 4.46 (d, J¼
7.5 Hz, 1H), 4.88–5.16 (m, 3H), 5.60 (ddd, J¼17.2, 10.4,
6.9 Hz, 1H), 7.20–7.35 (m, 5H). 13C NMR (125 MHz): d
(ppm)¼18.3 (CH3), 26.1 (CH3), 51.0 (CH), 77.0 (CH),
116.1 (CH2), 122.3 (CH), 127.0 (CH), 127.5 (CH), 128.0
(CH), 136.6 (C), 137.4 (CH), 141.9 (C).
3.2.7. 3-Benzyloxy-2-methylhexa-1,4-diene (6c). Ether 6c
was obtained in 78% yield from methacroleine (2 steps),
following the procedure described for the preparation of 4a.
1H NMR (250 MHz): d (ppm)¼1.72 (s, 3H), 4.24 (d, J¼
6.1 Hz, 1H), 4.46 (d, J¼12.0 Hz, 1H), 4.52 (d, J¼12.0 Hz,
1H), 4.98 (s, 1H), 5.05 (s, 1H), 5.23 (d, J¼10.4 Hz, 1H),
5.31 (d, J¼17.3 Hz, 1H), 5.84 (ddd, J¼17.3, 10.4, 6.1 Hz,
1H), 7.25–7.45 (m, 5H). 13C NMR (63 MHz): d (ppm)¼
17.6 (CH3), 69.6 (CH2), 83.5 (CH), 113.0 (CH2), 116.5
(CH2), 127.3 (CH), 127.5 (CH), 128.3 (CH), 137.3 (CH),
138.6 (C), 144.1 (C). IR (film): n (cm21)¼3070, 2859, 1644,
1454. MS (EI): m/z (%)¼170 (4, M2H2O), 97 (28), 91
(100).
4.2.2. (E)-7-Methyl-5-vinylocta-2,6-dien-4-ol
Procedure A. Yield 83% (anti/syn 93:7).
(5b).
Procedure B. Yield 93% (anti/syn 18:82). IR (film): n
(cm21)¼3405, 672, 1636, 1451, 1376. MS (EI): m/z (%)¼
148 (5, M2H2O), 133 (8), 96 (59), 81 (100).
1
anti-5b. H NMR (250 MHz): d (ppm)¼1.63 (s, 3H), 1.70
(d, J¼6.5 Hz, 3H), 1.74 (s, 3H), 1.78 (br s, OH), 3.06 (br q,
J¼8.0 Hz, 1H), 3.94 (t, J¼6.7 Hz, 1H), 5.03–5.13 (m, 3H),
5.47 (ddq, J¼15.3, 6.8, 1.6 Hz, 1H), 5.69 (dq, J¼15.3,
6.5 Hz, 1H), 5.69–5.77 (m, 1H). 13C NMR (63 MHz): d
(ppm)¼17.6 (CH3), 18.1 (CH3), 25.8 (CH3), 49.6 (CH), 74.8
(CH), 116.0 (CH2), 122.1 (CH), 127.2 (CH), 131.3 (CH),
134.3 (C), 137.9 (CH).
4. Zr-mediated pentadienylation of carbonyl compounds
4.1. General procedure for the preparation of
bis(homoallylic) alcohols (procedure A)
1
syn-5b. H NMR (250 MHz): d (ppm)¼1.66 (s, 3H), 1.71
To a solution of the dienyl ether (1 mmol) and Cp2ZrCl2
(321 mg, 1.1 mmol) in THF (5 mL) at 0 8C, was added
dropwise n-BuLi (2.2 mmol, 2–2.5 M in hexanes). After
stirring for 10 min at this temperature, the yellow solution
was refluxed for 0.5 h, and cooled to 278 8C (or 20 8C, see
Table 1). The carbonyl compound (1.5 mmol) was added,
and the mixture warmed slowly to room temperature (about
1 h). HCl 1N (5 mL) and Et2O (10 mL) were added to the
solution. The organic layer was separated and washed with
aq. NaHCO3, then dried over MgSO4. Filtration and
removal of the solvent gave a yellow oil, which was
purified by column chromatography (silica gel, petroleum
ether/ethyl acetate 92:8).
(d, J¼6.3 Hz, 3H), 1.73 (br s, OH), 1.78 (s, 3H), 3.06 (br q,
J¼7.8 Hz, 1H), 3.90 (t, J¼7.0 Hz, 1H), 5.01–5.15 (m, 3H),
5.48 (ddq, J¼15.3, 7.2, 1.4 Hz, 1H), 5.62–5.81 (m, 2H). 13C
NMR (63 MHz): d (ppm)¼17.5 (CH3), 18.0 (CH3), 25.8
(CH3), 49.2 (CH), 75.0 (CH), 115.5 (CH2), 122.3 (CH),
128.0 (CH), 131.3 (CH), 135.0 (C), 137.5 (CH).
4.2.3. (E)-6-Methyl-1-phenyl-4-vinylhepta-1,5-dien-3-ol
(5c). Procedure A. Yield 93% (anti/syn 92:8).
Procedure B. Yield 84% (anti/syn 20:80). IR (film): n
(cm21)¼3413, 1671, 1635, 1495, 1449, 1376. MS (EI): m/z
(%)¼228 (2, Mþz), 210 (9), 132 (58), 131 (100).
4.2. General procedure for the preparation of
bis(homoallylic) alcohols in the presence of BF3·OEt2
(procedure B)
1
anti-5c. H NMR (250 MHz): d (ppm)¼1.64 (s, 3H), 1.74
(s, 3H), 1.85 (br s, OH), 3.19 (br q, J¼7.9 Hz, 1H), 4.19 (t,
J¼6.4 Hz, 1H), 5.08–5.21 (m, 3H), 5.80 (ddd, J¼17.6, 9.7,
7.6 Hz, 1H), 6.23 (dd, J¼15.9, 6.0 Hz, 1H), 6.62 (d, J¼
15.9 Hz, 1H), 7.20–7.45 (m, 5H). 13C NMR (63 MHz): d
(ppm)¼18.3 (CH3), 25.9 (CH3), 49.8 (CH), 74.6 (CH),
116.5 (CH2), 121.7 (CH), 126.3 (CH), 127.4 (CH), 128.4
(CH), 129.8 (CH), 130.6 (CH), 135.0 (C), 136.8 (C), 137.7
(CH).
Procedure A was modified by the addition of BF3·OEt2
(125 L, 1 mmol) at 278 8C; the mixture was stirred for
15 min at this temperature before the addition of the
carbonyl compound.
4.2.1. 4-Methyl-1-phenyl-2-vinylpent-3-en-1-ol (5a).4
Procedure A. Yield 78% from 4a (anti/syn 92:8).
1
syn-5c. H NMR (250 MHz): d (ppm)¼1.68 (d, J¼1.3 Hz,
3H), 1.79 (d, J¼1.2 Hz, 3H), 1.96 (br d, J¼3.3 Hz, OH),
3.19 (br q, J¼7.7 Hz, 1H), 4.15 (td, J¼6.1, 3.3 Hz, 1H),
5.06–5.20 (m, 3H), 5.79 (ddd, J¼17.6, 9.8, 7.3 Hz, 1H),
6.23 (dd, J¼15.9, 6.6 Hz, 1H), 6.62 (d, J¼15.9 Hz, 1H),
7.20–7.45 (m, 5H). 13C NMR (63 MHz): d (ppm)¼18.2
(CH3), 25.9 (CH3), 49.6 (CH), 74.9 (CH), 116.0 (CH2),
122.1 (CH), 126.3 (CH), 127.3 (CH), 128.3 (CH), 129.9
(CH), 131.1 (CH), 135.4 (C), 136.7 (C), 137.4 (CH).
Procedure B. Yield 72% from 4a (anti/syn 26:74). IR (film):
n (cm21)¼3428, 1636, 1453, 1380. MS (EI): m/z (%)¼184
(4, M2H2O), 169 (10), 106 (48), 105 (52), 94 (39), 77
(100).
1
anti-5a. H NMR (500 MHz): d (ppm)¼1.33 (s, 3H), 1.61
(s, 3H), 2.25 (br s, OH), 3.24 (br q, J¼8.3 Hz, 1H), 4.49 (d,
J¼7.6 Hz, 1H), 5.02 (d, J¼9.4 Hz, 1H), 5.16 (d, J¼16.0 Hz,
1H), 5.17 (d, J¼11.3 Hz, 1H), 5.78 (ddd, J¼16.0, 11.3,
8.0 Hz, 1H), 7.20–7.35 (m, 5H). 13C NMR (125 MHz): d
(ppm)¼17.9 (CH3), 26.8 (CH3), 51.6 (CH), 76.4 (CH),
117.0 (CH2), 122.0 (CH), 126.7 (CH), 127.3 (CH), 127.8
(CH), 134.5 (C), 138.0 (CH), 142.1 (C).
4.2.4. 6-Methyl-4-vinylhept-5-en-3-ol (5d). Procedure A.
Yield 57% (anti/syn .95:5).
Procedure B. Yield 61% (anti/syn 68:32). IR (film): n

P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
1381
(cm21)¼3403, 1635, 1454, 1379. MS (EI): m/z (%)¼136 (1,
M2H2O), 107 (3), 96 (84), 81 (100).
(%)¼136 (18, M2H2O), 121 (65), 93 (81), 91 (65), 79
(100).
1
anti-5d. H NMR (250 MHz): d (ppm)¼0.96 (t, J¼7.4 Hz,
4.2.8. (E)-1,4-Diphenyl-2-vinylbut-3-en-1-ol (7a).2o Pro-
cedure A. Yield 90% (anti/syn .95:5).
3H), 1.28–1.36 (m, 1H), 1.56–1.65 (m, 1H), 1.63 (s, 3H),
1.71 (br s, OH), 1.73 (s, 3H), 2.97 (br q, J¼8.3 Hz, 1H), 3.35
(td, J¼7.9, 3.2 Hz, 1H), 5.05 (d, J¼9.4 Hz, 1H), 5.09–5.12
(m, 2H), 5.72 (ddd, J¼15.9, 10.7, 8.3 Hz, 1H). 13C NMR
(63 MHz): d (ppm)¼10.1 (CH3), 18.1 (CH3), 25.9 (CH3),
26.9 (CH2), 49.7 (CH), 75.1 (CH), 116.0 (CH2), 123.0 (CH),
133.6 (C), 138.3 (CH).
Procedure B. Yield 80% (anti/syn 16:84). IR (film): n
(cm21)¼3423, 1636, 1599, 1494, 1451. MS (EI): m/z (%)¼
232 (2, M2H2O), 144 (42), 129 (94), 128 (66), 77 (100).
1
anti-7a. H NMR (500 MHz): d (ppm)¼2.31 (br s, OH),
3.25 (br q, J¼7.4 Hz, 1H), 4.67 (d, J¼6.8 Hz, 1H), 5.22 (d,
J¼17.2 Hz, 1H), 5.26 (d, J¼10.2 Hz, 1H), 5.91 (ddd, J¼
17.2, 10.2, 8.1 Hz, 1H), 6.06 (dd, J¼16.0, 7.4 Hz, 1H), 6.33
(d, J¼16.0 Hz, 1H), 7.18–7.33 (m, 10H). 13C NMR
(125 MHz): d (ppm)¼55.4 (CH), 76.4 (CH), 118.4 (CH2),
126.1 (CH), 126.7 (CH), 127.3 (CH), 127.6 (CH), 128.1
(CH), 128.3 (CH), 128.4 (CH), 132.0 (CH), 136.9 (CH),
137.1 (C), 141.7 (C).
1
syn-5d. H NMR (250 MHz): d (ppm)¼0.96 (t, J¼7.4 Hz,
3H), 1.20–1.40 (m, 2H), 1.66 (s, 3H), 1.71 (br s, OH), 1.77
(s, 3H), 3.02 (br q, J¼8.2 Hz, 1H), 3.35 (td, J¼7.9, 3.2 Hz,
1H), 5.02–5.16 (m, 3H), 5.65–5.82 (m, 1H). 13C NMR
(63 MHz): d (ppm)¼10.0 (CH3), 18.1 (CH3), 26.0 (CH3),
26.8 (CH2), 48.9 (CH), 75.2 (CH), 115.4 (CH2), 122.4 (CH),
135.2 (C), 138.4 (CH).
4.2.5. 2,6-Dimethyl-4-vinylhept-5-en-3-ol (5e). Procedure
A. Yield 64% (anti/syn .95:5).
syn-7a. 1H NMR (250 MHz): d (ppm)¼2.26 (br d, J¼
3.0 Hz, OH), 3.27 (br q, J¼8.0 Hz, 1H), 4.69 (dd, J¼6.9,
3.0 Hz, 1H), 5.07 (d, J¼17.1 Hz, 1H), 5.09 (d, J¼10.8 Hz,
1H), 5.78 (ddd, J¼17.1, 10.8, 7.1 Hz, 1H), 6.23 (dd, J¼16.0,
8.0 Hz, 1H), 6.50 (d, J¼16.0 Hz, 1H), 7.20–7.41 (m, 10H).
13C NMR (63 MHz): d (ppm)¼55.4 (CH), 76.5 (CH), 117.2
(CH2), 126.3 (CH), 126.8 (CH), 127.5 (CH), 127.7 (CH),
128.0 (CH), 128.2 (CH), 128.5 (CH), 133.2 (CH), 136.9
(CH), 137.0 (C), 141.8 (C).
Procedure B. Yield 50% (anti/syn 57:43). IR (film): n
(cm21)¼3437, 1630, 1466, 1379. MS (EI): m/z (%)¼150
(12, M2H2O), 135 (24), 107 (50), 96 (52), 79 (100).
anti-5e. 1H NMR (250 MHz): d (ppm)¼0.85 (d, J¼6.7 Hz,
3H), 0.97 (d, J¼6.9 Hz, 3H), 1.58 (br s, OH), 1.62 (s, 3H),
1.71 (s, 3H), 1.65–1.80 (m, 1H), 3.03 (br q, J¼8.5 Hz, 1H),
3.22 (dd, J¼7.8, 4.0 Hz, 1H), 4.99–5.15 (m, 3H), 5.73 (ddd,
J¼17.7, 9.8, 8.3 Hz, 1H). 13C NMR (63 MHz): d (ppm)¼
15.6 (CH3), 18.1 (CH3), 20.2 (CH3), 25.9 (CH3), 30.0 (CH),
47.6 (CH), 77.9 (CH), 116.0 (CH2), 123.3 (CH), 132.9 (C),
138.5 (CH).
4.2.9. (1E,6E)-1,6-Diphenyl-4-vinylhexa-1,5-dien-3-ol
(7b). Procedure A. Yield 81% (anti/syn .95:5).
Procedure B. Yield 68% (anti/syn 18:82). IR (film): n
(cm21)¼3412, 1637, 1599, 1495, 1449. MS (EI): m/z
(%)¼276 (3, Mþz), 258 (3), 172 (6), 144 (16), 143 (100), 128
(75).
1
syn-5e. H NMR (250 MHz): d (ppm)¼0.94 (d, J¼6.6 Hz,
6H), 1.58 (br s, OH), 1.65 (d, J¼1.4 Hz, 3H), 1.77 (d, J¼
1.3 Hz, 3H), 1.65–1.82 (m, 1H), 3.12 (br q, J¼8.2 Hz, 1H),
3.20–3.28 (m, 1H), 4.99–5.17 (m, 3H), 5.72 (ddd, J¼17.0,
10.3, 7.2 Hz, 1H). 13C NMR (63 MHz): d (ppm)¼16.3
(CH3), 18.2 (CH3), 19.9 (CH3), 26.0 (CH3), 30.1 (CH), 46.8
(CH), 78.3 (CH), 115.3 (CH2), 122.3 (CH), 135.2 (C), 138.7
(CH).
1
anti-7b. H NMR (250 MHz): d (ppm)¼2.00 (br s, OH),
3.17 (br q, J¼7.3 Hz, 1H), 4.34 (br t, J¼5.7 Hz, 1H), 5.24
(d, J¼16.9 Hz, 1H), 5.26 (d, J¼10.5 Hz, 1H), 5.95 (ddd,
J¼16.9, 10.5, 7.7 Hz, 1H), 6.24 (dd, J¼15.9, 7.8 Hz, 1H),
6.28 (dd, J¼15.9, 6.3 Hz, 1H), 6.50 (d, J¼15.9 Hz, 1H),
6.64 (d, J¼15.9 Hz, 1H), 7.15–7.45 (m, 10H). 13C NMR
(63 MHz): d (ppm)¼54.2 (CH), 74.7 (CH), 118.1 (CH2),
126.2 (CH), 126.5 (CH), 127.4 (CH), 127.7 (CH), 127.9
(CH), 128.5 (CH), 128.5 (CH), 129.5 (CH), 131.6 (CH),
132.7 (CH), 136.6 (C), 136.8 (CH), 137.0 (C).
4.2.6. 4-Methyl-2-vinylpent-3-en-1-ol (5f). Procedure A.
Yield 81%. 1H NMR (250 MHz): d (ppm)¼1.52 (br s, OH),
1.67 (s, 3H), 1.74 (s, 3H), 3.18 (quint., J¼7.6 Hz, 1H), 3.45
(dd, J¼10.3, 6.9 Hz, 1H), 3.52 (dd, J¼10.3, 7.3 Hz, 1H),
5.00 (d, J¼9.1 Hz, 1H), 5.11 (d, J¼10.3 Hz, 1H), 5.12 (d,
J¼17.2 Hz, 1H), 5.69 (ddd, J¼17.2, 10.3, 7.2 Hz, 1H). 13C
NMR (63 MHz): d (ppm)¼18.1 (CH3), 25.9 (CH3), 45.7
(CH), 65.4 (CH2), 115.8 (CH2), 122.6 (CH), 135.3 (C),
138.1 (CH). MS (EI): m/z (%)¼126 (2, Mþz), 108 (23), 93
(65), 91 (68), 79 (100).
syn-7b. 1H NMR (250 MHz): d (ppm)¼2.04 (br s, OH), 3.16
(br q, J¼6.9 Hz, 1H), 4.30–4.38 (m, 1H), 5.17–5.25 (m,
2H), 5.94 (ddd, J¼17.7, 9.5, 7.5 Hz, 1H), 6.26 (dd, J¼ 16.0,
8.0 Hz, 1H), 6.27 (dd, J¼16.0, 6.4 Hz, 1H), 6.52 (d,
J¼16.0 Hz, 1H), 6.64 (d, J¼16.0 Hz, 1H), 7.18–7.41 (m,
10H). 13C NMR (63 MHz): d (ppm)¼54.2 (CH), 74.8 (CH),
117.7 (CH2), 126.3 (CH), 126.5 (CH), 127.5 (CH), 127.7
(CH), 127.9 (CH), 128.5 (CH), 128.5 (CH), 129.6 (CH),
131.6 (CH), 132.9 (CH), 136.6 (C), 136.8 (CH), 137.0 (C).
4.2.7. 2,5-Dimethyl-3-vinylhex-4-en-2-ol (5g).2i Procedure
A. Yield 70%. 1H NMR (250 MHz): d (ppm)¼1.17 (s, 3H),
1.18 (s, 3H), 1.65 (s, 3H), 1.70 (br s, OH), 1.78 (s, 3H),
2.98 (dd, J¼9.4, 8.8 Hz, 1H), 5.05–5.20 (m, 3H), 5.72–5.86
(m, 1H). 13C NMR (63 MHz): d (ppm)¼18.2 (CH3), 26.1
(CH3), 26.5 (CH3), 26.9 (CH3), 54.4 (CH), 72.5 (C), 116.3
(CH2), 122.5 (CH), 134.6 (C), 137.9 (CH). MS (EI): m/z
4.2.10. (E)-6-Phenyl-4-vinylhex-5-en-3-ol (7c). Procedure
A. Yield 90% (anti/syn 93:7).
Procedure B. Yield 80% (anti/syn 50:50). IR (film): n

1382
P. Bertus et al. / Tetrahedron 60 (2004) 1375–1383
(cm21)¼3415, 1637, 1599, 1495, 1449. MS (EI): m/z (%)¼
184 (2, M2H2O), 144 (91), 129 (100), 128 (96), 115 (85).
49.5 (CH), 76.7 (CH), 116.4 (CH2), 126.8 (CH), 127.5 (CH),
128.0 (3 CH), 137.0 (CH), 141.9 (C).
1
anti-7c. H NMR (250 MHz): d (ppm)¼1.00 (t, J¼7.4 Hz,
4.2.12. 2-Vinylpent-3-en-1-ol (7e). Procedure A. Yield
62% (E/Z 71:29). IR (film): n (cm21)¼3356, 1638, 1453,
1377. MS (EI): m/z (%)¼95 (2), 81 (54), 79 (100).
(E)-7e. 1H NMR (250 MHz): d (ppm)¼1.50 (br s, OH), 1.71
(d, J¼6.4 Hz, 3H), 2.91 (quint., J¼7.2 Hz, 1H), 3.46–3.55
(m, 2H), 5.11–5.17 (m, 2H), 5.36 (ddq, J¼15.4, 7.8, 1.5 Hz,
1H), 5.59 (dq, J¼15.4, 6.4 Hz, 1H), 5.66–5.76 (m, 1H). 13C
NMR (63 MHz): d (ppm)¼18.1 (CH3), 49.8 (CH), 65.1
(CH2), 116.4 (CH2), 128.2 (CH), 129.6 (CH), 137.9 (CH).
3H), 1.60–1.75 (m, 3H), 2.98 (br q, J¼8.0 Hz, 1H), 3.51–
3.60 (m, 1H), 5.21 (d, J¼17.0 Hz, 1H), 5.23 (d, J¼10.5 Hz,
1H), 5.90 (ddd, J¼17.0, 10.5, 8.0 Hz, 1H), 6.19 (dd, J¼16.0,
8.0 Hz, 1H), 6.47 (d, J¼16.0 Hz, 1H), 7.17–7.38 (m, 5H).
13C NMR (63 MHz): d (ppm)¼10.1 (CH3), 27.2 (CH2),
53.9 (CH), 74.9 (CH), 117.6 (CH2), 126.1 (CH), 127.3
(CH), 128.5 (CH), 129.1 (CH), 131.8 (CH), 137.2 (C), 137.2
(CH).
1
syn-7c. H NMR (250 MHz): d (ppm)¼1.00 (t, J¼7.4 Hz,
3H), 1.56–1.71 (m, 2H), 1.74 (br s, OH), 2.94–3.02 (m,
1H), 3.51–3.60 (m, 1H), 5.18 (d, J¼17.5 Hz, 1H), 5.22 (d,
J¼10.3 Hz, 1H), 5.89 (ddd, J¼17.5, 10.3, 8.4 Hz, 1H), 6.23
(dd, J¼16.0, 8.4 Hz, 1H), 6.49 (d, J¼16.0 Hz, 1H), 7.17–
7.38 (m, 5H). 13C NMR (63 MHz): d (ppm)¼10.1 (CH3),
27.2 (CH2), 53.6 (CH), 75.0 (CH), 116.9 (CH2), 126.2 (CH),
127.4 (CH), 128.2 (CH), 128.5 (CH), 132.6 (CH), 137.1 (C),
137.9 (CH).
(Z)-7e. 1H NMR (250 MHz): d (ppm)¼1.65 (br s, OH), 1.67
(dd, J¼6.8, 1.7 Hz, 3H), 3.33 (quint., J¼7.5 Hz, 1H), 3.46–
3.55 (m, 2H), 5.11–5.17 (m, 2H), 5.27 (ddq, J¼10.8, 9.4,
1.7 Hz, 1H), 5.66–5.76 (m, 2H). 13C NMR (63 MHz): d
(ppm)¼13.2 (CH3), 44.6 (CH), 65.3 (CH2), 116.6 (CH2),
127.4 (CH), 128.5 (CH), 137.5 (CH).
4.2.13. 3-Methyl-1-phenyl-2-vinylbut-3-en-1-ol (7f). Pro-
cedure A. Yield 76% (anti/syn 88:12).
4.2.11. 1-Phenyl-2-vinylpent-3-en-1-ol (7d).2o Procedure
A. Yield 85% ((E)-anti/(Z)-anti/(E)-syn/(Z)-syn 76:20:4:0).
Procedure B. Yield 48% (anti/syn 35:65) accompanied with
29% of the linear isomer 8. IR (film): n (cm21)¼3424, 1644,
1494, 1453. MS (EI): m/z (%)¼170 (3, M2H2O), 155 (8),
106 (98), 105 (99), 77 (100).
Procedure B. Yield 70% (20:1:60:19). IR (film): n (cm21)¼
3412, 1630, 1454. MS (EI): m/z (%)¼170 (4, M2H2O), 155
(10), 106 (61), 105 (61), 79 (80), 77 (100).
1
anti-7f. H NMR (500 MHz): d (ppm)¼1.61 (s, 3H), 2.18
1
(E)-anti-7d. H NMR (500 MHz): d (ppm)¼1.59 (d, J¼
(br d, J¼2.0 Hz, OH), 2.98 (t, J¼8.4 Hz, 1H), 4.70 (dd,
J¼7.8, 2.0 Hz, 1H), 4.73 (s, 1H), 4.77 (br s, 1H), 5.18 (d,
J¼17.1 Hz, 1H), 5.21 (dd, J¼10.2, 1.7 Hz, 1H), 6.01 (ddd,
J¼17.1, 10.2, 9.2 Hz, 1H), 7.25–7.34 (m, 5H). 13C NMR
(125 MHz): d (ppm)¼21.8 (CH3), 59.9 (CH), 74.9 (CH),
113.1 (CH2), 118.1 (CH2), 126.8 (CH), 127.6 (CH), 128.1
(CH), 137.1 (CH), 142.0 (C), 144.5 (C).
6.3 Hz, 3H), 2.32 (br s, OH), 3.02 (br q, J¼7.4 Hz, 1H), 4.57
(d, J¼6.9 Hz, 1H), 5.11 (d, J¼17.3 Hz, 1H), 5.16 (d, J¼
10.2 Hz, 1H), 5.28 (ddq, J¼15.4, 7.2, 1.3 Hz, 1H), 5.39 (dq,
J¼15.4, 6.3 Hz, 1H), 5.79 (ddd, J¼17.3, 10.2, 8.1 Hz, 1H),
7.24–7.32 (m, 5H). 13C NMR (125 MHz): d (ppm)¼18.0
(CH3), 55.1 (CH), 76.2 (CH), 117.6 (CH2), 126.8 (CH),
127.3 (CH), 127.8 (CH), 127.9 (CH), 129.1 (CH), 137.4
(CH), 141.9 (C).
syn-7f. 1H NMR (500 MHz): d (ppm)¼1.81 (s, 3H), 2.29 (br
d, J¼2.1 Hz, OH), 3.07 (t, J¼8.6 Hz, 1H), 4.64 (dd, J¼9.4,
2.1 Hz, 1H), 4.86 (d, J¼17.1 Hz, 1H), 4.91 (d, J¼10.3 Hz,
1H), 5.01 (s, 1H), 5.05 (br s, 1H), 6.01 (ddd, J¼17.1, 10.3,
8.1 Hz, 1H), 7.25–7.34 (m, 5H). 13C NMR (125 MHz): d
(ppm)¼20.0 (CH3), 60.3 (CH), 74.5 (CH), 114.1 (CH2),
117.1 (CH2), 127.0 (CH), 127.6 (CH), 128.0 (CH), 135.9
(CH), 141.9 (C), 145.0 (C).
1
(Z)-anti-7d. H NMR (500 MHz): d (ppm)¼1.38 (dd, J¼
6.8, 1.7 Hz, 3H), 2.25 (br s, OH), 3.41 (br q, J¼8.3 Hz, 1H),
4.53 (d, J¼7.7 Hz, 1H), 5.19–5.25 (m, 2H), 5.29 (ddq, J¼
10.7, 9.7, 1.7 Hz, 1H), 5.47 (dq, J¼10.7, 6.8 Hz, 1H), 5.80–
5.88 (m, 1H), 7.25–7.35 (m, 5H). 13C NMR (125 MHz): d
(ppm)¼12.8 (CH3), 50.2 (CH), 76.2 (CH), 117.1 (CH2),
126.3 (CH), 126.8 (CH), 127.4 (CH), 127.9 (CH), 128.0
(CH), 137.6 (CH), 142.0 (C).
4.2.14. 3-Methyl-1-phenylhexa-3,5-dien-1-ol (8). 1H
NMR (500 MHz): d (ppm)¼1.83 (s, 3H), 2.10 (br s, OH),
2.42 (dd, J¼13.7, 9.1 Hz, 1H), 2.45 (dd, J¼13.7, 4.4 Hz,
1H), 4.82 (dd, J¼9.1, 4.4 Hz, 1H), 5.07 (dd, J¼10.2, 1.5 Hz,
1H), 5.16 (dd, J¼16.9, 1.5 Hz, 1H), 5.97 (d, J¼10.0 Hz,
1H), 6.59 (dt, J¼16.9, 10.5 Hz, 1H), 7.25–7.34 (m, 5H). 13C
NMR (125 MHz): d (ppm)¼16.7 (CH3), 50.3 (CH2), 71.7
(CH), 116.3 (CH2), 125.7 (CH), 127.5 (CH), 128.4 (CH),
129.1 (CH), 132.7 (CH), 135.2 (C), 144.0 (C).
(E)-syn-7d. 1H NMR (500 MHz): d (ppm)¼1.74 (dd, J¼6.4,
1.5 Hz, 3H), 2.28 (br d, J¼2.5 Hz, OH), 3.02 (br q, J¼
7.7 Hz, 1H), 4.49 (dd, J¼7.5, 2.5 Hz, 1H), 4.92–5.01 (m,
1H), 5.45 (ddq, J¼15.4, 8.4, 1.5 Hz, 1H), 5.59–5.68 (m,
2H), 7.25–7.34 (m, 5H). 13C NMR (125 MHz): d (ppm)¼
18.2 (CH3), 55.4 (CH), 76.3 (CH), 116.5 (CH2), 126.9 (CH),
127.5 (CH), 128.0 (CH), 129.3 (CH), 129.6 (CH), 137.3
(CH), 141.9 (C).
(Z)-syn-7d. 1H NMR (500 MHz): d (ppm)¼1.59 (d, J¼
6.8 Hz, 3H), 2.23 (br s, OH), 3.44 (br q, J¼7.8 Hz, 1H),
4.53–4.57 (m, 1H), 4.92–5.02 (m, 2H), 5.40–5.46 (m, 1H),
5.60–5.65 (m, 1H), 5.75 (dq, J¼10.9, 6.8 Hz, 1H), 7.25–
7.35 (m, 5H). 13C NMR (125 MHz): d (ppm)¼13.2 (CH3),
References and notes
1. (a) Yamamoto, Y.; Asao, N. Chem. Rev. 1993, 93, 2207.
(b) Roush, W. Comprehensive Organic Synthesis; Trost, B. M.,

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´
2. Leading references for pentadienylmetals: Li: (a) Gerard, F.;
Tetrahedron Lett. 1989, 30, 5105. (c) Ito, H.; Taguchi, T.;
Hanzawa, Y. Tetrahedron Lett. 1992, 33, 1295. (d) Ito, H.;
Nakamura, T.; Taguchi, T.; Hanzawa, Y. Tetrahedron 1995,
51, 4507.
Miginiac, P. Bull. Soc. Chim. Fr. 1974, 1924. Li and K:
(b) Schlosser, M.; Zellner, A.; Leroux, F. Synlett 2001, 1830.
Mg: (c) Yasuda, H.; Yamauchi, M.; Nakamura, A.; Sei, T.;
Kai, Y.; Yasuoka, N.; Kasai, N. Bull. Chem. Soc. Jpn 1980, 53,
7. The pentadienyl ethers are stable compounds in comparison
with pentadienyl bromides.
8. For the 1,3-metallotropic rearrangement with Zr, see: (a) Ref.
5. (b) Wipf, P.; Jahn, H. Tetrahedron 1996, 52, 12853, and
references therein.
´
1089. Zn: (d) Gerard, F.; Miginiac, P. Bull. Soc. Chim. Fr.
1974, 2527. (e) Ghosez, L.; Marko, I.; Hesbain-Frisque, A. M.
Tetrahedron Lett. 1986, 27, 5211. (f) Jung, M. E.; Nichols, C. J.
Tetrahedron Lett. 1996, 37, 7667. (g) Fuijta, K.; Schlosser, M.
Helv. Chim. Acta 1982, 65, 1258. (h) Suginome, M.;
Yamamoto, Y.; Fujii, K.; Ito, Y. J. Am. Chem. Soc. 1995,
117, 9608. Ti: (i) Okamoto, S.; Sato, F. J. Organomet. Chem.
2001, 624, 151. (j) Zellner, A.; Schlosser, M. Synlett 2001,
1016. Cr: (k) Sodeoka, M.; Yamada, H.; Shimizu, T.;
Watanuki, S.; Shibasaki, M. J. Org. Chem. 1994, 59, 712.
Sn: (l) Nishigaichi, Y.; Fujimoto, M.; Takuwa, A. Synlett
1994, 731. Si: (m) Kobayashi, S.; Nishio, K. Chem. Lett. 1994,
9. We have noticed that this procedure is also useful for the
preparation of allylzirconocenes from allylic ethers.
10. The anti configuration was defined with reference to the
simpler allylmetalation reactions, by considering pentadienyl-
zirconiums as alkenyl-substituted allylmetals. The anti
configuration was undoubtedly assigned to the major isomers
by a cyclization method. For an example see Ref. 4.
11. Reetz, M. T.; Sauerwald, M. J. Org. Chem. 1984, 49, 2292.
12. (a) Ireland, R. E.; Mueller, R. H.; Willard, A. K. J. Am. Chem.
¨
Soc. 1976, 98, 2868. (b) Szymoniak, J.; Thery, N.; Moıse, C.
Synlett 1997, 1239.
´
´
1773. (n) Vallee, Y.; Pelloux-Leon, N.; Minassian, F. Synlett
2000, 242. In: (o) Hirashita, T.; Inoue, S.; Yamamura, H.;
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(p) Melekhov, A.; Fallis, A. G. Tetrahedron Lett. 1999, 40,
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13. Similar reversal of anti to syn stereoselectivity was also
obtained with TiCl4. The reversal of anti to syn selectivity was
found to be less stronger when the solution of the aldehyde and
BF3 in THF was added to the reaction mixture.
3. The use of alcohol derivatives, i.e. acetates or carbonates, for
preparing pentadienylmetals is limited to titanium and
chromium complexes, see Refs. 2i,k.
14. The predominant syn diastereoselection in the Lewis acid-
mediated allylic tin-aldehyde condensation reactions was
rationalized similarly, see Ref. 1.
4. Bertus, P.; Cherouvrier, F.; Szymoniak, J. Tetrahedron Lett.
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15. The formation of the 1-regioisomeric by-product 8 from the
ether 6c in the presence of a Lewis acid (see Table 3) also
corroborates a non-cyclic mechanism.
5. For reviews of ‘Cp2Zr’ chemistry, see: (a) Negishi, E.;
Takahashi, T. Bull. Chem. Soc. Jpn 1998, 71, 755. (b) Negishi,
E.; Kondakov, D. Y. Chem. Soc. Rev. 1996, 26, 417.
(c) Negishi, E.; Takahashi, T. Acc. Chem. Res. 1994, 27, 124.
6. (a) Negishi, E.; Huo, S. In Titanium and Zirconium in Organic
Synthesis; Marek, I., Ed.; Wiley-VCH: Weinheim, 2002; p 1.
(b) Rousset, C. J.; Swanson, D. R.; Lamaty, F.; Negishi, E.
16. For example, different open transition structures have been
considered for the Lewis acid-mediated allylmetalation
reactions, see: (a) Denmark, S. E.; Weber, E. J. Helv. Chim.
Acta 1983, 66, 1655. (b) Denmark, S. E.; Weber, E. J. J. Am.
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