New and stereoselective synthesis of 1,4-disubstituted buten-4-ols (homoallylic alcohol α-adducts) from the corresponding γ-isomers (3,4-disubstituted buten-4-ols) via an acid-catalyzed allyl-transfer reaction with aldehydes

Article abstract of DOI:10.1021/ja990057p

The γ-adducts of homoallylic alcohols 3, derived from aldehydes via the usual reaction with common allylic metals 1, were converted to the corresponding α-adducts 6 by an acid-catalyzed allyl-transfer reaction. In the allyl-transfer reaction, anti-and syn

Full text of DOI:10.1021/ja990057p

1310
J. Am. Chem. Soc. 2000, 122, 1310-1313
New and Stereoselective Synthesis of 1,4-Disubstituted Buten-4-ols
(Homoallylic Alcohol R-Adducts) from the Corresponding γ-Isomers
(3,4-Disubstituted Buten-4-ols) via an Acid-Catalyzed Allyl-Transfer
Reaction with Aldehydes
Shin-ichi Sumida, Masanori Ohga, Junji Mitani, and Junzo Nokami*
Contribution from the Department of Applied Chemistry, Okayama UniVersity of Science, 1-1 Ridai-cho,
Okayama 700-0005, Japan
ReceiVed January 6, 1999. ReVised Manuscript ReceiVed July 11, 1999
Abstract: The γ-adducts of homoallylic alcohols 3, derived from aldehydes via the usual reaction with common
allylic metals 1, were converted to the corresponding R-adducts 6 by an acid-catalyzed allyl-transfer reaction.
In the allyl-transfer reaction, anti- and syn-γ-adducts 3 gave E- and Z-R-adducts 6, respectively, and the optical
purity of the γ-adducts 3 was transferred to the R-adducts 6 with >98%ee. This suggests that the allyl-transfer
reaction proceeds stereoselectively via six-membered cyclic transition states [T]. The reaction was catalyzed
by various metal triflates as well as Lewis acids and Brønsted acids.
Introduction
Scheme 1
The allylation of aldehydes by allylic nucleophiles leading
to homoallylic alcohols is one of the most important and popular
C-C bond formation reactions. In widespread allylations of
aldehydes with allylic metals to afford homoallylic alcohols,1
much attention has focused on the stereoselectivity of the
pathway leading to the R- or γ-adducts that are produced
regioselectively, i.e., ratio of E- or Z-olefins in the R-adducts
and ratio of anti or syn isomers in the γ-adducts. The
diastereoselective allylation of aldehydes has already been
achieved by Lewis acid promoted allylation with allylic tin
reagents via acyclic transition states to give syn isomers 32 and
by reaction with E- and Z-allylic metals 1 (without Lewis acid)
via six-membered cyclic transition states 2 to give anti and syn
isomers 3, respectively.3 However, only a few methods for the
stereoselective synthesis of R-adducts have been reported,4
because almost all allylic metals react with aldehydes to give
the γ-adducts exclusively.
The R-selective allylations of aldehydes by allylic metals
explored to date have used common allylic metal reagents 1
(M ) Sn, Mg, Li) along with mediators 4, such as Sn(IV)
chlorides4a-e or AlCl3,4g,h as well as allylic barium reagents
prepared from active barium metal and allylic chlorides.5 In most
of these cases, it is assumed that transmetalation of the allylic
unit of the R-allylmetal nucleophile 1 to the mediator 4 gives
the γ-allylmetal nucleophile 5, which in turn reacts with
aldehyde to give the R-adduct 6 (Scheme 1). Support for this
scheme has been reported by Naruta, who showed via an NMR
study that the transmetalation of an allylic unit from 2-bute-
nyltributyltin (R1 ) Me, M ) Sn, Y ) Bu, n ) 3) 1a to SnCl4
(4a) gave (1-methyl-2-propenyl)trichlorotin 5a.6 It is, however,
generally rather difficult to perform the allylation of aldehydes
to give only R-adducts 6, due to isomerization of the γ-allylmetal
nucleophile 5 to the R-allylmetal species 1′. Furthermore, these
procedures are not very satisfactory in terms of practical use,
because the desired products 6, formed using 2-butenyltributyltin
1a, were contaminated with a large amount of tributyltin residues
(3) It is also well-known that (E)- and (Z)-2-butenylmetals predominantly
give anti and syn isomers, respectively, by allylations via a six-membered
cyclic transition state 2. For example: (a) Buse, C. T.; Heathcock, C. H.
Tetrahedron Lett. 1978, 1685. (b) Hiyama, T.; Kimura, K.; Nozaki, H.
Tetrahedron Lett. 1981, 22, 1037. (c) Sato, F.; Iida, K.; Moriya, H.; Sato,
M. J. Chem. Soc., Chem. Commun. 1981, 1140. (d) Hoffman, R. W.; Zeiss,
H.-J. Angew. Chem., Int. Ed. Engl. 1979, 18, 306. (e) Collum, D. B.;
McDonald, J. H., III; Still, W. C. J. Am. Chem. Soc. 1980, 102, 2118.
(1) For a recent review on allylation reactions using allylic metals, see:
Yamamoto, Y.; Asao, N. Chem. ReV. 1993, 93, 2207 and references therein.
(2) It is known that both (E)- and (Z)-2-butenylmetal reagents give syn-
γ-adducts predominantly by Lewis acid (L.A.) promoted reactions. For the
reaction mechanism, the following acyclic transition model was proposed.
(a) Yamamoto, Y.; Yatagai, H.; Naruta, Y.; Maruyama, K. J. Am. Chem.
Soc. 1980, 102, 7107. (b) Yamamoto, Y.; Maruyama, K. Heterocycles 1982,
18, 357.
10.1021/ja990057p CCC: $19.00 © 2000 American Chemical Society
Published on Web 02/05/2000

StereoselectiVe Synthesis of 1,4-Disubstituted Buten-4-ols
J. Am. Chem. Soc., Vol. 122, No. 7, 2000 1311
Scheme 4. Stereochemistry of the Allyl Transfera
Scheme 2
Scheme 3
a The absolute configurations (S and R) are shown as R )
CH2CH2Ph.
This is very different from the previously reported intramo-
lecular C-C bond formation reactions between an oxycarbenium
ion and π-nucleophile (CdC),8 in which six- and five-membered
cyclic ethers are obtained via an intramolecular Prins reaction.
In some of these cases, the 2-oxonia [3,3]-sigmatropic rear-
rangement is driven by a subsequent C-C bond-forming
event.8l,m
Based on the considerations outlined above, we performed
additional investigations of the R-selective allylation of alde-
hydes via allyl-transfer reactions of homoallylic alcohols,
derived from aldehydes.
that were not easy to separate. Therefore, there still remains a
great interest in the development of more practical and versatile
methods for the stereoselective synthesis of homoallylic alcohols
of type 6.
Results and Discussion
Allyl Transfer from Benzaldehyde to 3-Phenylpropanal.
First, we expected that 2-methyl-1-phenyl-3-buten-1-ol 3b,
prepared from benzaldehyde and 2-butenylmetal reagents,9
would serve as an allyl donor in the allyl-transfer reactions and
react with 3-phenylpropanal to give the corresponding R-adduct
6i. This is because (i) the benzyl cation 8B is more stable than
8A, (ii) 6i is less hindered than 3b, and (iii) the internal olefin
6i is more stable than the terminal olefin 3b. In view of this,
3a-g were treated with 3-phenylpropanal in the presence of
10 mol % of Sn(OTf)2 in CH2Cl2.
As shown in Table 1, the R-adducts 6h-l were obtained in
moderate yields, together with the byproducts 6b-e (entries
2-5), which were formed in the allyl-transfer reaction of 3b-e
to benzaldehyde liberated from the desired allyl-transfer of 3b-e
Recently, we reported a new method for the R-specific
allylation of aldehydes, in which an allylic unit was transferred
from the homoallylic alcohol 7, derived from a ketone (acetone),
to an aldehyde to give the R-adduct 6 in the presence of Sn-
(OTf)2.7 We proposed a reaction mechanism that proceeds via
an oxycarbenium ion intermediate that undergoes a 2-oxonia
[3,3]-sigmatropic rearrangement, as shown in Scheme 2. We
also suggested that the reaction could be driven toward products
deriving from the most stable cations or those containing
sterically less hindered homoallylic alcohols and/or thermody-
namically more stable olefins.
(4) For example, (a) 2-butenyltributyltin 1a (2-butenylmetal)/Bu2SnCl2
4c (mediator)/25 °C (reaction temperature): Gambaro, A.; Gains, P.; Marton,
D.; Peruzzo, V.; Tagliavini, G. J. Organomet. Chem. 1982, 231, 307. (b)
1a/BuSnCl3 4b/25 °C: Gambaro, A.; Boaretto, A.; Marton, D.; Tagliavini,
G. J. Organomet. Chem. 1984, 260, 255. (c) 1a/4a, 4b, or 4c, and then
HClO4 (4 M)/20 °C: Marton, D.; Tagliavini, G.; Vanzan, N. J. Organomet.
Chem. 1989, 376, 269. (d) 1a/SnCl4 4a/-78 °C: Keck, G. E.; Abbott, D.
E.; Boden, E. P.; Enholm, E. J. Tetrahedron Lett. 1984, 25, 3927. (e) (Z)-
1a/4b/room temperature or 0 °C: Miyake, H.; Yamamura, K. Chem. Lett.
1992, 1369. (f) E-allylic alcohols, Me3SiCl, NaI, H2O, Sn/room tempera-
ture: Kanagawa, K.; Nishiyama, Y.; Ishii, Y. J. Org. Chem. 1992, 57, 6988.
(g) 1a/AlCl3, i-PrOH/-78 °C: Yamamoto, Y.; Maeda, N.; Maruyama, K.
J. Chem. Soc., Chem. Commun. 1983, 742. (h) 2-butenylmagnesium
chloride/AlCl3/0 °C or room temperature: Yamamoto, Y.; Maruyama, K.
J. Org. Chem. 1983, 48, 1564. (i) 2-butenyllithium/CeCl3/-78 °C: Guo,
B.-S.; Doubleday: W.; Cohen, T. J. Am. Chem. Soc. 1987, 109, 4710. (j)
1a/CoCl2/room temperature: Iqbal, J.; Joseph, S. P. Tetrahedron Lett. 1989,
30, 2421. The degrees of both R-selectivity and E/Z selectivity in each of
these allylations were very variable, and would depend on the structure of
aldehydes, allylic metal reagents, meditators, and the reaction conditions.
(5) Among the various allylation reactions reported, the reaction of allylic
barium compounds is particularly useful, because it always gave R-adducts
selectively without using any mediators. However, the preparation of allylic
barium compounds required the reduction of barium iodide by 2 equiv of
lithium biphenylide: (a) Yanagisawa, A.; Habaue, S.; Yamamoto, H. J.
Am. Chem. Soc. 1991, 113, 8955. (b) Yanagisawa, A.; Habaue, S.; Yasue,
K.; Yamamoto, H. J. Am. Chem. Soc. 1994, 116, 6130.
(8) Synthesis of tetra- or dihydropyran derivatives: (a) Gambaro, A.;
Boaretto, A.; Marton, D.; Tagliavini, G. J. Organomet. Chem. 1983, 254,
293. (b) Boaretto, A.; Marton, D.; Tagliavini, G. Inorg. Chim. Acta 1983,
77, L153. (c) Gambaro, A.; Furlani, D.; Marton, D.; Tagliavini, G. J.
Organomet. Chem. 1986, 299, 157. (d) Wei, Z. Y.; Li, J. S.; Wang, D.;
Chan, T. H. Tetrahedron Lett. 1987, 28, 3441. (e) Wei, Z. Y.; Wang, D.;
Li, J. S.; Chan, T. H. J. Org. Chem. 1989, 54, 5768. (f) Coppi, L.; Ricci,
A.; Taddei, M. Tetrahedron Lett. 1987, 28, 973. (g) Coppi, L.; Ricci, A.;
Taddei, M. J. Org. Chem. 1988, 53, 911. (h) Mekhalfia, A.; Marko´, E. I.;
Adams, H. Tetrahedron Lett. 1991, 32, 4783. (i) Marko´, I. E.; Mekhalfia,
A. Tetrahedron Lett. 1992, 33, 1799. (j) Marko´, I. E.; Chelle´, F. Tetrahedron
Lett. 1997, 38, 2895. (k) Hoffman, R. W.; Giesen, V.; Fuest, M. Liebigs
Ann. Chem. 1993, 629. (l) Lolkema, L. D. M.; Hiemstra, H.; Semeyn, C.;
Speckamp W. N. Tetrahedron 1994, 50, 7115. (m) Lolkema, L. D. M.;
Semeyn, C.; Hiemstra, H.; Speckamp W. N. Tetrahedron 1994, 50, 7129.
(n) Nishizawa, M.; Shigaraki, T.; Takao, H.; Imagawa, H.; Sugihara, T.
Tetrahedron Lett. 1999, 40, 1153. Synthesis of 3-acyltetrahydrofuran
derivatives: (o) Hopkins, M. H.; Overman, L. E. J. Am. Chem. Soc. 1987,
109, 4748. (p) Hopkins, M. H.; Overman, L. E.; Rishton, G. M. J. Am.
Chem. Soc. 1991, 113, 5354.
(9) For selective preparation of anti-γ-adducts, we employed the methods
using 2-butenylchromium compounds reported by Hiyama and Nozaki, and
Heathcock; (a) Okude, Y.; Hirano, S.; Hiyama, T.; Nozaki, H. J. Am. Chem.
Soc. 1977, 99, 3179. (b) Buse, C. T.; Heathcock, C. H. Tetrahedron Lett.
1978, 1685. (c) Hiyama, T.; Kimura, K.; Nozaki, H. Tetrahedron Lett. 1981,
22, 1037. (d) Hiyama, T.; Okude, Y.; Kimura, K.; Nozaki, H. Bull. Chem.
Soc. Jpn. 1982, 55, 561.
(6) Naruta, Y.; Nishigaichi, Y.; Maruyama, K. Tetrahedron 1989, 45,
1067.
(7) Nokami, J.; Yoshizane, K.; Matsuura, H.; Sumida, S. J. Am. Chem.
Soc. 1998, 120, 6609.

1312 J. Am. Chem. Soc., Vol. 122, No. 7, 2000
Sumida et al.
Table 1. Allyl-Transfer Reaction from γ-Adducts Derived from Benzaldehyde to 3-Phenylpropanal
γ-adducts 3
γ-adducts 6, yielda/% (E/Z)b
run
R
R1
R2
anti/synb
T/°C
time/h
R ) CH2CH2Ph
R ) Ph
1
2
3
4
5
6
7
8i
3a
3b
3c
3d
3e
3f
Ph
Ph
Ph
Ph
H
Me
Ph
CO2Et
Me
H
Me
Me
H
H
H
H
Me
H
H
25
25
25
40
40
25
-25
-25
5
5
1
9
0.1
6
9
6h, 53c
20/1
33/1
1/1
6i, 62 (33/1)
6j, 47 (E)
6k, 47 (E)d
6l, 7
6b, 29 (17/1)
6c, 50 (E)
6d, 6 (E)e
6e, 29
Ph
Mesf
Mesf
Mesf
6h, 65g
3g
3g
3/1
3/1
6i, 58 (E)h
6i, 84 (E)
H
4
a Isolated yield. b Determined by 1H NMR. c 3a (37%) was recovered. d The Z isomer was obtained as the lactone 6k′ (18%). e The Z isomer was
obtained as the lactone 6d′ (10%). f Mes ) 2,4,6-Me3C6H2. g 3f (15%) was recovered. h 3g (37%, anti/syn ) 3/1) was recovered. i Performed with
Sn(OTf)2 (0.15 mmol).
Table 2. Catalytic Conversion of γ-Adducts to R-Adductsa
γ-adducts 3
R-adducts 6
entry
R
R1
R2
anti/synb
T/°C
time/h
yieldc/% (E/Z)b
1
2
3
4
5
6
7
8
9
b
c
d
e
i
i
j
j
l
Ph
Ph
Ph
Ph
Me
Ph
CO2Et
Me
Me
Me
Ph
CO2Et
Me
Me
H
H
H
Me
H
H
H
H
Me
H
(20/1)
(35/1)
(1/1.7)
0
0
40
25
2
0.5
40
0.1
3
2
1
24
22
2
b, 78 (49/1)d
c, 76 (E)e
d, 11 (E)f,g
e, 29
PhCH2CH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
CH3(CH2)8
CH3(CH2)8
(33/1)
(1/7.5)
(14/1)
(1/1.3)
0-25
i, 89 (25/1)
i, 90 (1/5.3)h
j, 82 (E)i
25
25
40
40
k, 41 (E)j
l, 16k
10
m
m
(12/1)
(12/1)
0
m, 72 (11/1)
m, 91 (11/1)
11l
Me
H
-25-0
9
a All reactions were performed with 3 (0.5 mmol), aldehyde (0.05 mmol), and Sn(OTf)2 (0.05 mmol) in CH2Cl2 (2.5 mL), unless otherwise
1
noted. b Determined by H NMR. c Isolated yield. d 4% (anti/syn ) 1/1) of 3b was recovered. e 8% (anti/syn ) 2/1) of 3c was recovered. f The Z
isomer was obtained as the lactone 6d′ (33%). g 19% (anti/syn ) 14/1) of 3d was recovered. h 3% (syn) of 3i was recovered. i 6% (anti/syn ) 1/23)
of 3j was recovered. j The Z isomer was obtained as the lactone 6k′ (51%). k 58% (syn) of 3l was recovered. l Performed with Sn(OTf)2 (0.15
mmol).
to 3-phenylpropanal (Scheme 3). To reduce the yield of the
byproducts, 1-mesityl-2-methyl-3-buten-1-ol 3g was employed
as the allyl donor, and the desired product 6i (84%) was obtained
without formation of the corresponding byproduct. It is likely
that steric hindrance due to the methyl groups at the 2,6-positions
suppresses the R-allylation of mesitaldehyde via allyl-transfer
with 3g.
Conversion of γ-Adduct to R-Adduct and a Possible
Reaction Mechanism. The results shown in Table 1 enabled
us to design a conversion of γ-adducts 3, easily derived from
normal allylation of aldehydes with allylic metal reagents, into
the corresponding R-adducts 6 by treatment with a very small
amount of the parent aldehyde used in the preparation of 3, as
summarized in Table 2.
The results in Table 2 clearly show that the conversion of
γ-adducts 3 to R-adducts 6 is very successful, although there is
a small limitation that hindered homoallylic alcohols, such as
3e,l (entries 4 and 9), are less reactive. The E selectivity of the
R-adducts 6 formed from the anti isomers of 3b,c,i,j,m (entries
1, 2, 5, 7, 10, and 11) can be explained by the transition-state
models T, as shown in Scheme 4. The E-isomers of the
R-adducts are obtained predominantly from anti homoallylic
alcohol precursors via the sterically favored transition state T1.
In contrast, when the syn isomer of 3i is used (entry 6), the
reaction proceeds via T3 to give the Z-isomer of 6i predomi-
nantly.
Stereochemistry in the Allyl Transfer from anti-γ to E-R.
To confirm the stereospecificity shown in Scheme 4, optically
pure (3R,4S)-3i10 was separated by preparative HPLC and treated
with 10 mol % of 3-phenylpropanal and Sn(OTf)2 in CH2Cl2
for 3 h to give (E)-6i in 85% yield with >98% ee (determined
by HPLC; DAISEL CHIRALCEL OD). The absolute config-
uration of 6i derived from (3R,4S)-3i was determined to be S
after hydrogenation of 6i to (3R)-1-phenyl-3-heptanol 14 by
identification with an authentic sample prepared as follows.
Preparation of Authentic Sample (R)-14. Ethyl 3-oxo-5-
phenylpentanoate 9 was treated with Ru2Cl4(S-BINAP)2‚NEt3
catalyst under 20 Kgf/cm2 hydrogen atmosphere at 30 °C to
give ethyl (3S)-3-hydroxy-5-phenylpentanoate 1011 (98%ee),
which was in turn converted to tert-butyldimethylsilyl (TBDMS)
ether 11 by treatment with TBDMS-Cl/imidazole in DMF. This
was then converted to the corresponding aldehyde 12 by

StereoselectiVe Synthesis of 1,4-Disubstituted Buten-4-ols
J. Am. Chem. Soc., Vol. 122, No. 7, 2000 1313
Scheme 5a
a Key: (i) Ru2Cl4[(S)-BINAP]‚2Et3N (cat.)/H2 (20 atm, 30 °C); (ii) t-BuMe2SiCl/imidazole/DMF; (iii) DIBAL/-78 °C/0.5 h/ether; (iv) Ph3P+
-CHCH3/-78 °C/15 min; (v) Bu4NF/3 h/0 °C/THF; (vi) H2/Pd-C/ethanol/2 h.
-
Table 3. Conversion of γ-Adducts to R-Adducts: Effect of
minor product, was shown to have an R configuration and
enantiomeric excess >98% by chiral HPLC analysis. This
clearly shows that in addition to T1 the transition models T2
and T3 are also reasonable.
Catalystsa
Effect of Catalysts. To clarify the effect of catalysts, further
studies of the reaction of 3i with 3-phenylpropanal to give 6i
were carried out in the presence of a variety of metal salts and
acids. The results are listed in Table 3.
yield of 6i recovery of 3i
run catalyst/mol% (anti/syn)b time h %c (E/Z)b %c (anti/syn)b
3i
In addition to metal triflates, most of the mediators 4, used
for the previously reported R-selective allylations by the allylic
metals, served as effective catalysts for this allyl-transfer reaction
(entries 1-11). Surprisingly, Brønsted acids, trifluoromethane-
sulfonic acid, and hydrogen chloride catalyzed this γ to R
conversion (entries 13 and 14).
1
2
3
4
5
Sn(OTf)2/10
Sn(OTf)2/10
Sn(OTf)2/10
Cu(OTf)2/10
Ag(OTf)/10
23/1
1/7.5
2
2
4
88 (25/1) N.D.d
90 (1/5.3) 3 (syn)
80 (20/1) 2 (2/1)
19/1
17/1
23/1
25/1
16/1
33/1
25/1
1/1
16/1
20/1
18/1
100/1
48 72 (25/1) 16 (6/1)
95 83 (25/1) 4 (3/1)
6
3
8
6e AlCl3/10
51 (50/1) 39 (10/1)
63 (20/1) 23 (12/1)
77 (23/1) 10 (4/1)
7
AlCl3‚3PriOH/33
Conclusion
8f SnCl4/2
9g Bu2SnCl2/100
10g CeCl3/100
11h CeCl3/100
12 BaCl2/100
13 CF3SO3H/10
14 HCl/100
24 56 (33/1) 35 (16/1)
24 37 (1.7/1) 51 (0.8/1)
36 44 (17/1) 15 (9/1)
The mehod described in this paper provides a new, efficient
procedure for the synthesis of R-homoallylic alcohols 6 via allyl
transfer from the normal γ-homoallylic alcohols 3. The allylation
of the anti and syn diastereomers of the γ-adducts 3 proceeds
in a highly stereoselective manner via the six-membered cyclic
transition states [T] to afford the E- and Z-R-adducts 6,
respectively. Moreover, the optical purities of both anti- and
syn-γ-adducts 3 are also transferred to the corresponding
R-adducts 6 with >98% ee. As compared with the previously
reported methods for the R-selective allylation via transmeta-
lation of allylic metal reagents 1 with mediators 4, the present
approach has several advantages. First, use of the γ-homoallylic
alcohols 3 as allyl-transfer reagents is a noteworthy advance in
synthetic methodology. Second, both the stereochemistry of the
product olefins and the absolute configuration of the R-adducts
6 is easily deduced from the starting γ-adducts 3. Finally, the
allyl-transfer reaction proceeds smoothly under mild reaction
conditions (at room temperature with catalytic amount of acids),
and the reaction products are easily purified.
Acknowledgment. We are grateful to Professor Tsuneo Sato
(Kurashiki University of Science and the Arts) for his kind and
helpful discussions during this work. We also thank Takasago
International Co. Ltd. for donating BINAP-Ru catalyst and Dr.
Noboru Sayo for helpful advice in the preparation of the
optically active â-hydroxy ester using the catalyst. This work
was financially supported by a Grant from the NOVARTIS
foundation (Japan) for the Promotion of Science, a Grant for
Cooperative Research administered by the Japan Private School
Promotion Foundation, and a Grant in Aid for Scientific Reserch
from the Ministry of Education, Science, Culture, and Sports,
Japan.
48 N.D.d
2
4
quant
89 (17/1) 1 (syn)
84 (100/1) 2 (syn)
a All reactions were performed with 3i (0.5 mmol) and 3-phenyl-
propanal (0.05 mmol), in CH2Cl2 (2.5 mL) at 25 °C, unless otherwise
noted. b Determined by 1H NMR. c After isolation by column chroma-
tography on silica gel. d Not detected. e Performed in ether (0.3 mL).
f Performed at 0-25 °C. g Performed in refluxing CH2Cl2 (0.5 mL).
h Performed in refluxing CH3CN (0.3 mL). i Performed in refluxing
CH2Cl2, CH3CN, and THF.
treatment with DIBAH in ether at -78 °C. The resulting
aldehyde 12 was combined with triphenylphosphoniumethylide
in THF at -78 °C to give (5S)-5-tert-butyldimethylsilyloxy-7-
phenyl-2-heptene 13, which was then treated with tetrabutyl-
ammonium fluoride to afford (3S)-1-phenyl-5-heptene-3-ol 6i
(E/Z ) 1/1.6). Finally, the authentic (3R)-1-phenylheptan-3-ol
14 was obtained by hydrogenation of (3S)-6i. Note that the
reactions used above were not optimized (Scheme 5).
Stereochemistry in the Allyl Transfer from syn-γ to Z-R.
Optically pure (3R,4R)-3i, isolated by preparative chiral HPLC
purification of (3R,4R)-3i (79% ee) that was prepared according
to the method reported by Roush,10 was allowed to react with
10 mol % of 3-phenylpropanal and Sn(OTf)2 in CH2Cl2 for 3 h
to give 6i in 80% yield (E/Z ) 1/18). The enantiomeric excess
of (Z)-6i was determined to be >98% ee, and the absolute con
figuration of the major isomer was identified as S by comparison
with the authentic sample (R)-14 after hydrogenation of (Z)-6i
to 14. In addition, (E)-6i, obtained here from (3R,4R)-3i as a
Supporting Information Available: Complete experimental
details, including characterization data for 3 and 6, stereochem-
ical correlations, and copies of 1H and 13C NMR spectra of 6d,
6d′, 6e, 6k, 6k′, 10, 12, and 14 (PDF). This material is available
free of charge via the Internet at http://pubs.acs.org.
(10) The absolute configuration of 3i was determined by comparison
with an authentic sample prepared by the reaction of 3-phenylpropanal with
(R,R)-diisopropyl tartrate (E)-2-butenylboronate: (a) Roush, W. R.; Ando,
K.; Powers, D. B.; Palkowitz, A. D.; Halterman, R. L. J. Am. Chem. Soc.
1990, 112, 6339. (b) Roush. W. R.; Ando, K.; Powers, D. B.; Halterman,
R. L.; Palkowitz, A. D. Tetrahedron Lett. 1988, 29, 5579.
(11) Noyori, R.; Ohkuma, T.; Kitamura, M.; Takaya, H.; Sayo, N.;
Kumobayashi, H.; Akutagawa, S. J. Am. Chem. Soc. 1987, 109, 5856.
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