Preparation and reactions of water stable hypervalent 10-Sn-5 allyl ate complexes

Article abstract of DOI:10.1002/hc.1064

Hypervalent 10-Sn-5 allyl and crotyl tin ate complexes bearing Martin ligands were prepared and found to be surprisingly stable in water. These compounds were found to react with aldehydes in the presence of weak Lewis acids such as LiBr to give the corresponding homoallyl alcohols. Product analysis of the reaction of the crotyl compounds indicated that the reaction occurred via a cyclic transition state unlike an acyclic transition state operative for widely utilized allyltrialkyltin reagents that are of ordinary valency.

Full text of DOI:10.1002/hc.1064

Heteroatom Chemistry
Volume 12, Number 5, 2001
Preparation and Reactions of Water Stable
Hypervalent 10-Sn-5 Allyl Ate Complexes
Satoshi Kojima, Fumihiro Kondoh, Jun-ya Kawakami,
Yohsuke Yamamoto, and Kin-ya Akiba
Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japan
Received 4 January 2001; revised 9 March 2001
[2]. Chiral allylic reagents have led to the stereocon-
trolled synthesis of chiral polypropionates and car-
bohydrates [3], and the development of catalytic
asymmetric reactions has widened the synthetic
scope of tin reagents [4]. Among allylmetal com-
pounds, it has been found that hypervalent allylsili-
cate compounds bearing oxygens or fluorines as the
remaining coordinating atoms also undergo the
ABSTRACT: Hypervalent 10-Sn-5 allyl and crotyl tin
ate complexes bearing Martin ligands were prepared
and found to be surprisingly stable in water. These
compounds were found to react with aldehydes in the
presence of weak Lewis acids such as LiBr to give the
corresponding homoallyl alcohols. Product analysis of
the reaction of the crotyl compounds indicated that the
reaction occurred via a cyclic transition state unlike
an acyclic transition state operative for widely utilized
allyltrialkyltin reagents that are of ordinary valency.
allylation reaction and in a manner (type I) differing
from that of the corresponding normal valent allyl-
silanes (type II) [5,6]. The utility of hypervalent
᭧ 2001 John Wiley & Sons, Inc. Heteroatom Chem
allylsilane compounds has been enhanced by the dis-
covery that allylsilyltrichloride reacts under mild
conditions in the presence of donor solvents [7]. Al-
though examples are still limited, hypervalent tin is
also gradually finding a place as a group of reagents
useful for organic synthesis. Notable examples are
as an anhydrous source of fluoride [8], and as aryl
and alkyl donors in cross coupling reactions [9]. As
for allylation reactions, there is little precedence,
and the only examples we are aware of are the uses
of ate complexes, bearing tartaric ester ligands gen-
erated in situ, in asymmetric allylation reactions
[10,11]. We have had a long interest in hypervalent
compounds, and during the course of the examina-
tion of the reactivity of water stable hypervalent 10-
Sn-5 compounds [12], we have found that hyperva-
lent 10-Sn-5 allyltin compounds bearing Martin’s
ligands as bidentates undergo allylation, while cor-
responding allylsilane reagents have been reported
to be inactive [5]. Herein we report the details.
12:425–431, 2001
INTRODUCTION
The allylation reaction has enjoyed widespread ap-
plication in organic synthesis as a means of intro-
ducing new C–C bonds, especially because the allyl
group can undergo further manipulation to provide
other functional groups [1]. The unique mode of re-
action (type II, acyclic transition state) differing
from that of other allylborane or allylmetal reagents
(type I, cyclic transition state) has made allyl and
crotylstannanes attractive complementary reagents
Dedicated to Prof. Naoki Inamoto on the occasion of his 72nd
birthday.
Correspondence to: Kin-ya Akiba. Present address: Advanced Re-
search Center for Science and Engineering, Waseda University, 3-
4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan; Tel., Fax: (ם81)
3-5286-3165; E-mail: akibaky@mn.waseda.ac.jp
᭧ 2001 John Wiley & Sons, Inc.
424

Preparation and Reactions of Water Stable Hypervalent 10-Sn-5 Allyl Ate Complexes 425
RESULTS AND DISCUSSION
structure in which the oxygen atoms of the bidentate
are located in apical positions, as expected for pen-
Preparation of allyl tin ate complex 2 was carried out
according to Scheme 1. Two equivalents of lithium 1,
1,1,3,3,3-hexafluoro-2-(2-lithiophenyl)-2-propoxide 1
(prepared by the method described by Martin et al.
[13]) was added to allyltin(IV) chloride (prepared ac-
cording to a reported disproportionation method
[14]) in tetrahydrofuran (THF) at מ78ꢀC, followed
by treatment with Et4NBr to give the allyl compound
tacoordinate compounds of ordinary structure. The
19F NMR spectra showed only a pair of quartets, im-
plying the presence of only two different fluorine
groups and they did not coalesce in the temperature
range of מ60ꢀC to 100ꢀC. This indicated that the
pseudorotation of the tin compounds was unobserv-
able on the NMR timescale, thereby giving a lower
ס|
מ1
DG
limit for the barrier as at least
ס 21 kcal mol
؀
2a-Et4N in 60% yield. Counterion exchange was re-
[18].
quired since the allylic compound with lithium as
the countercation was found to be rather unstable to
aqueous workup, whereas that with the ammonium
countercation was found to be perfectly stable at am-
bient temperatures. Since the same method could
not be used for the synthesis of crotyl compounds,
due to the expected facile isomerization of the crotyl
moiety [2], we used a modified method that does not
require heating for the preparation of allyltin(IV) tri-
halide, from allyl halide and tin(II) halide, to mini-
mize isomerization [15]. Immediately after mixing
crotyl chloride (ca. 9:1 mixture of E-Z isomers) and
tin dichloride in THF at 0ꢀC, the solution was added
to a THF solution of two equiv. of 1 at מ78ꢀC, af-
fording the crotyl compound (a mixture of E-Z iso-
mers in 80:20 ratio) in 51% yield after counterion
exchange with Et4NBr. The 119Sn NMR chemical
Initial investigations were carried out with the
allyl ate complex 2a-Li generated in situ without
؀
countercation exchange as tabulated in Table 1. The
ate complex was found to react with aromatic alde-
hydes (Table 1, entries 1 and 2) smoothly at room
temperature (rt) giving homoallylic alcohols along
with an insoluble substance likely to be hydroxylated
tin ate complex 3 or oligomeric material originating
from 3. The ␣-branched alkyl aldehyde, 2-phenylpro-
pionaldehyde, was also found to react (entry 3); how-
ever, the ␣-unbranched alkyl aldehyde, 3-phenylpro-
pionaldehyde, gave hardly any expected product,
even after prolonged reaction periods (entry 4). We
reasoned that this was due to undesired side reac-
tions induced by basic contaminants present be-
cause of incomplete transformation to the ate com-
plex. In order to minimize the affect of these species,
the ate complex solution was filtered through a bed
of Celite prior to use. The ate complex solution
treated in this way gave rise to the desired product
in an improved yield of 46% (entry 5). The reaction
of a ketone (acetophenone) proved to be sluggish
(entry 6), probably due to steric hindrance. The re-
action of 2-phenylpropionaldehyde gave rise to a
mixture of diastereomers in a ratio of 4:1 in favor of
the syn product. This complies with predictions from
the Felkin-Anh model, and, interestingly, the ratio is
؀
shift of the allyl compound 2a-Et4N was d מ105.0
؀
(CD3CN), while that of the crotyl mixture 2b-Et4N
was d מ104.9, מ105.3 (acetone-d6). These high-field
chemical shifts are a clear indication that the com-
1
pounds are pentacoordinate [16]. In H NMR spec-
tra, the protons of the aryl groups ortho to tin
showed characteristic downfield shifts also seen for
neutral pentacoordinate compounds [17], and the
spectra as a whole was indicative of a C2 symmetric
SCHEME 1

426 Kojima et al.
؀
TABLE 1 The Reactions of Allyl Ate Complex 2a-Li Pre-
pared In Situ
tion of benzaldehyde was also found to be activated
by Li (entries 12, 13).
ם
Allylation reactions of allyltin reagents generally
take place via one of two transition states. Water sta-
ble tetraorganotin reagents of ordinary valency are
believed to react via acyclic transition states (type
II), while tetravalent reagents with halogen substit-
uents [2d] and a hypervalent reagent [11], which are
all susceptible to water, have been suggested to pro-
ceed via cyclic transition states (type I). Discrepancy
between the two paths is usually examined by the
reaction of crotyl reagents, in which the former
group of reagents favor the syn product regardless
of the geometry of the reagent, whereas reagents of
the latter group undergo stereospecific reactions,
that is, the E-crotyl reagent leads to the anti product,
while the Z-crotyl reagent gives the syn product.
Thus, the reactions of the E-rich crotyl reagent were
examined more thoroughly.
In order to see whether the reagent was prone to
geometric isomerization, reagent mixtures of two
different ratios (E:Z ס 80:20 and 64:36) were sub-
jected to the standard reaction conditions of allyla-
tion (LiBr, reflux). Neither mixture underwent more
than 3% change in ratio over a period of 4 days, thus
establishing the reliability of the forthcoming reac-
tion stereochemical results.
Entry Carbonyl Compound
Conditionsa
Yield (%)
1
2
3
4
5
6
PhCHO
rt, 19 hours
rt, 20 hours
rt, 16 hours
rt, 8.5 days
rt, 19 hoursb
reflux, 67 hours
78
4-MeOC6H4CHO
PhCH(CH3)CHO
PhCH2CH2CHO
PhCH2CH2CHO
PhCOCH3
66
72 (4:1)c
6
46
5
aCarried out in THF.
bThe ate complex solution was passed through a bed of Celite prior
to use.
cThe syn:anti ratio is in parenthesis.
about the same as in the reaction of allyltributyltin
with the aldehyde promoted by Lewis acids at lower
temperatures [2a,b,19].
To eliminate the need to prepare the fresh re-
agent for every reaction, we decided to examine the
؀
storability of the ammonium salt 2a-Et4N . The re-
sults are given in Table 2. Contrary to expectation,
the ate complex was found to be inert and did not
react with 2-phenylpropionaldehyde even at reflux
temperature (Table 2, entry 1). This implied that
some ingredients in the solution of the in situ freshly
؀
prepared ate complex 2a-Li had activated the re-
action. To elucidate the components, several addi-
tives were examined with 2-phenylpropionaldehyde
as substrate. Since Li seemed to be the best candi-
As the substrate, 4-nitrobenzaldehyde was util-
ized to facilitate the reaction. Scheme 3 and Table 3
summarize the results. Reexamination of the reac-
tion under nonadditive conditions for this substrate
revealed that the reaction is actually accelerated as
expected to give the anticipated product in moderate
yield (Table 3, entry 1). However, the diastereomeric
ratio was low. The reaction in the presence of LiBr
was found to proceed even at rt, giving the anti prod-
uct in preference (entry 2). Indications were that the
reaction proceeded via a cyclic transition state. This
stereoselectivity also provided evidence that the ate
complex is the reacting species and not dissociated
crotyl lithium, which is reckoned to give unselective
product mixtures [1]. The use of less reactive aro-
matic aldehydes revealed that, although higher tem-
peratures were required, stereoselectivity was re-
tained to a high degree (entries 3–5) [20]. The use of
LiF, which is a fluorine source, and LiBF4, which is
a potential fluorine source, led to some decrease in
the diastereomeric ratio (entries 6 and 7). Unexpect-
edly, LiClO4 also led to a decrease (entry 8). The va-
lidity of MgBr2 was also revealed (entry 9). The use
of solvents with donor ability higher than THF led
to lower reactivity, and the diastereomeric ratio de-
creased, especially in the case of dimethylformamide
(DMF) (entries 10 and 11). The use of Lewis acids
usually employed in reactions of ordinary valent
ם
date, several lithium salts were examined. Although
reflux temperature was required, the reaction did
מ
מ
proceed, regardless of the counteranion (Cl , Br ,
מ
מ
F , BF4 ; entries 2–7). Since the result upon using
LiBF4 was comparable with the others, the main
ם
source of activation could be concluded to be Li .
An examination of the effects of two ammonium ha-
lides resulted in obvious acceleration, but to a lesser
ם
extent than with Li salts present, as indicated by
the required reaction times and lower yields (entries
8 and 9). A Lewis acid frequently used in allyltin
chemistry of ordinary valency, BF3 •OEt2, was found
to accelerate the reaction, but led to a somewhat
lower yield (entry 10). Since the reactivity attained
؀
for 2a-Li , prepared in situ, could not be reproduced
when the other additives were present, unreacted or
only partially transformed allyltin chloride became
the suspected cocatalyst. Addition of a catalytic
amount of allyltin chloride reproduced the results
obtained from the in situ reaction (entry 11). The
ם
effectiveness of Li as a promoter in the reaction of
the allyl ate complex was thus unveiled. The diaster-
eoselectivity ratio was found to be comparable with
؀
that of 2a-Li in some cases, although the reaction
was carried out at a higher temperature. The reac-

Preparation and Reactions of Water Stable Hypervalent 10-Sn-5 Allyl Ate Complexes 427
SCHEME 2
؀
TABLE 2 The Reactions of Isolated Allyl Ate Complex 2a-Et4N
Entry
Aldehyde
Solvent
Additive
Conditions
reflux
Yield (%)a
1
2
3
4
5
6
7
8
9
10
11
12
13
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCH(CH3)CHO
PhCHO
THF
THF
THF
CH2Cl2 ם THF
THF
THF
THF
CH2Cl2
CH2Cl2 ם THF
CH2Cl2
CHCl3
none
0
LiCl (4 equiv.)
LiCl (1 equiv.)
LiCl (1 equiv.)
LiBr (4 equiv.)
LiF (4 equiv.)
LiBF4 (4 equiv.)
reflux, 45 hours
reflux, 45 hours
reflux, 89 hours
reflux, 32 hours
reflux, 45 hours
reflux, 45 hours
reflux, 145 hours
reflux, 114 hours
rt, 44 hours
80 (4:1)
57 (3.7:1)
49 (5:1)
80 (nd)b
62 (nd)b
74 (2.4:1)
44 (1.6:1)
10 (2:1)
32 (2.4:1)
65 (nd)b
0
Et4NCl (1 equiv.)
Bu4NF (1 equiv.)
BF3 •OEt2
AllylSnCl3 (0.1 equiv.) ם LiBr (4 equiv.)
none
rt, 6 hours
reflux
rt, 15 hours
THF
CHCl3 ם THF
PhCHO
LiBr (4 equiv.)
88
aThe syn:anti ratio is in parenthesis.
bNot determined.
SCHEME 3
allyltin reagents was also examined. The reaction us-
ing BF3 •OEt2 proceeded at 0ꢀC and resulted in a re-
versal in selectivity in favor of the syn product (entry
12). In order to determine whether the product ratio
was dependent on the E:Z ratio of the ate complex,
a reagent with 64:36 composition was also exam-
ined, and the results turned out the same (entry 13).
This is an indication that, in the case of BF3 •OEt2,
the major pathway is via the acyclic path. The use of
other Lewis acids resulted in nearly 1:1 mixtures (en-
tries 14–16). In these instances, the involvement of
other active allyl species are implemented by the low
selectivity, as in the case of 2a-Li .
؀
The plausible transition state is depicted in
Scheme 4. Since a cyclic transition state is imple-
mented by the selectivity in the reaction of the crotyl
reagents, the carbonyl oxygen apparently interacts
with the Lewis acidic tin atom to form the chair form
ם
ring. The role of Li as activator can be rationalized
to be a chelating agent between the carbonyl oxygen
and one of the ligand oxygens, and, in turn, as an
activator of the Lewis acidic tin atom by withdraw-

428 Kojima et al.
؀a
TABLE 3 The Reactions of Isolated Crotyl Ate Complex 2b-Et4N
Entry
Aldehyde
Solvent
Additive
Conditions
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11c
12
13d
14
15
16
4-O2NC6H4CHO
4-O2NC6H4CHO
4-ClC6H4CHO
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CHCl3 ם THF
CH3CN
DMF
CH2Cl2
CH2Cl2
CH2Cl2
none
LiBr (4 equiv.)
LiBr (4 equiv.)
LiBr (4 equiv.)
LiBr (4 equiv.)
LiF (4 equiv.)
LiBF4 (4 equiv.)
LiClO4 (4 equiv.)
MgBr2 (4 equiv.)
LiBr (4 equiv.)
reflux, 168 hours
rt, 14 hours
reflux, 19 hours
reflux, 18 hours
reflux, 17 hours
40ꢀC, 4 hours
rt, 14 hours
53 (55/45)
88 (75/25)
85 (78/22)
96 (78/22)
64 (76/24)
71 (61/39)
85 (55/45)
91 (70/30)
93 (76/24)
91 (74/26)
81 (56/44)
93 (31/69)
88 (32/68)
80 (45/55)
93 (47/53)
89 (46/54)
PhCHO
4-MeOC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
4-O2NC6H4CHO
reflux, 4 hours
rt, 23 hours
reflux, 22 hours
50ꢀC, 45 hours
0ꢀC, 12 hours
0ꢀC, 12 hours
0ꢀC, 24 hours
0ꢀC, 12 hours
0ꢀC, 12 hours
LiBr (4 equiv.)
BF3 •OEt2 (1 equiv.)
BF3 •OEt2 (1 equiv.)
Me3SiOTf (1 equiv.)
SnCl4 (0.1 equiv.)
TiCl4 (0.1 equiv.)
CH2Cl2
CH2Cl2
؀
aThe E/Z ratio of the crotyl reagent 2b-Et4N was 80:20, unless otherwise noted.
bThe anti:syn ratio is in parenthesis.
cThe E/Z ratio of the crotyl reagent was 75:25.
dThe E/Z ratio of the crotyl reagent was 64:36.
1H NMR (400 MHz), 19F (376 MHz), and 119Sn (162
MHz) spectra were recorded on a JEOL EX-400
1
spectrometer. H NMR (90 MHz) and 19F NMR (85
MHz) spectra were also routinely recorded on a Hi-
1
tachi R-90H spectrometer. H NMR chemical shifts
(d) are given in ppm downfield from internal Me4Si,
or from residual chloroform (d ס 7.26), acetonitrile
(d ס 2.1), or acetone (d ס 2.0). 19F NMR chemical
shifts (d) are given in ppm downfield from external
CFCl3. 119Sn NMR chemical shifts (d) are given in
ppm downfield from external Me4Sn. Elemental
SCHEME 4 Plausible Transition State for the Reaction of
(E)-Crotyl Ate Complex 2b-Et4N Leading to the anti Product
ם
analyses were performed on
2400CHN elemental analyzer.
a Perkin Elmer
ing electron density from the atom. Thus, there is
probably some contribution in the transition state
from the limiting structure shown on the right. The
All reactions were carried out under N2. Tetra-
hydrofuran was freshly distilled from Na-benzophe-
none. CH2Cl2 and CHCl3 were freshly distilled from
CaH2 prior to use. All other solvents and liquid re-
agents were distilled from CaH2 and stored under
inert atmospheres. Inorganic salts were all of anhy-
drous grade and were used as received. Preparative
thin-layer chromatography was carried out on plates
of Merck silica gel 60 GF254.
ם
interaction of Li with one of the oxygen atoms of
the ligand bonded to the tin is also suggested by 119Sn
؀
NMR spectroscopy. The chemical shifts of 2b-Et4N
were found to shift downfield to מ103.5 from
מ104.9 and מ105.3 upon addition of 10 equiv. of
either LiClO4 or LiBr, whereas no shift was observed
for LiF, Bu4NF, or Et4NBr.
In summary, we have isolated the first water sta-
ble ammonium salts of allyltin ate complexes. The
allylation reaction of the ate complexes readily gave
allyl alcohols upon reaction with aldehydes provided
that the lithium cation was present, via what we be-
lieve to be a cyclic transition state involving activa-
tion by the lithium cation.
Tetraethylammonium Bis[␣,␣-bis(trifluoro-
methyl)benzenemethanolato(2-)-C2,O]
؀
allylstannate (2a-Et4N )
To n-BuLi (1.59 M in hexane, 9.40 mL, 14.9 mmol),
was added N,N,NЈ,NЈ-tetramethylethylenediamine
(0.23 mL, 1.52 mmol), and the resulting solution was
stirred for 20 minutes to allow the formation of a
suspension. Then, THF (1 mL) was added to dissolve
the precipitate, and 1,1,1,3,3,3-hexafluoro-2-phenyl-
EXPERIMENTAL
Melting points were measured with a Yanagimoto
micro melting point apparatus and are uncorrected.

Preparation and Reactions of Water Stable Hypervalent 10-Sn-5 Allyl Ate Complexes 429
2-propanol (1.20 mL, 7.18 mmol) was added drop-
(m, 1 H), 4.90–4.45 (m, 2 H), 2.54–2.50 (q, J ס 7.3
Hz, 8 H), 1.99 (d, J ס 8.1 Hz, 2 H), 1.18 (t of t, J ס
7.3 Hz, 3J14N-H ס 1.9 Hz, 12 H). 119Sn NMR (acetone-
wise at 0ꢀC. After the solution had been stirred over-
night at room temperature, THF (9 mL) was added
to dissolve the newly formed precipitate, followed by
the dropwise addition of allyltin(IV) chloride (0.50
mL, 3.56 mmol) at מ78ꢀC. The solution was allowed
to warm to rt, and stirring was continued for a few
hours. The solvent was removed in vacuo, and then
dry CH2Cl2 (10 mL) was added to give a suspension.
This was transferred to Et4NBr (0.76 g, 3.60 mmol)
in dry CH2Cl2 (10 mL), and the resulting mixture was
stirred overnight. After careful filtration through
Celite, the filtrate was concentrated, and the residue
was recrystallized (CH2Cl2-benzene) to give colorless
crystals containing one equivalent of benzene (1.83
g, 60%). A subsequent trial revealed that the product
was not amenable to aqueous workup. Benzene
could be removed by heating under reduced pres-
d6)
d
מ104.9,
מ105.3.
Calcd
for
C30H35F12NO2Sn•0.5xC6H6: C, 47.91; H, 4.63; N, 1.69.
Found C, 47.70; H, 4.52; N, 1.46.
General Procedure for the Allylation Reactions
To a solution of an allyltin reagent (0.54 mmol) and
LiBr (2.3 mmol) in a mixture of THF (9.3 mL) and
CH2Cl2 (9.3 mL) was added an aldehyde (0.54 mmol)
at rt. After having been stirred for the specified
amount of time at the specified temperature, the so-
lution was treated with aq NH4Cl. Extraction with
CH2Cl2 and treatment of the combined extracts with
anhydrous MgSO4, followed by removal of organic
solvents, gave an oily substance. This was redissol-
ved in hexane, and insoluble tin residues were re-
moved by filtration. The crude mixture was then sub-
jected to chromatographic treatment (SiO2, CH2Cl2)
to furnish the pure product.
؀
sure. 2a-Et4N m.p. 147–148ꢀC (dec); 1H NMR
(CD3CN) d 8.05–8.00 (m, 2 H), 7.7–7.6 (m, 2 H), 7.4–
7.2 (m, 4 H), 6.30–5.78 (m, 1 H), 4.90–4.45 (m, 2 H),
3.12 (q, J ס 7.3 Hz, 8 H), 1.99 (d, J ס 8.1 Hz, 2 H),
3
1.18 (t of t, J ס 7.3 Hz, J14
ס 1.9 Hz, 12 H). 19F
N-H
NMR (CD3CN) d מ74.6 (q, J ס 8.3 Hz, 6 F), מ74.7
(q, J ס 8.3 Hz, 6 F). 119Sn NMR (CD3CN) d מ105.0.
Calcd for C29H33F12NO2Sn: C, 44.99; H, 4.30; N, 1.81.
Found C, 44.90; H, 4.05; N, 2.11.
1-Phenyl-3-buten-1-ol. 1H NMR (CDCl3) d 7.43–
7.23 (m, 5H), 6.04–5.58 (m, 1H), 5.28–5.03 (m, 2H),
4.70 (t, J ס 7 Hz, 1H), 2.49 (t, J ס 7 Hz, 2H), 2.10
(s, 1H).
1-(4-Methoxyphenyl)-3-buten-1-ol.
1H NMR
Tetraethylammonium Bis[␣,␣-bis(trifluoro-
methyl)benzenemethanolato(2-)-C2,O]
(CDCl3) d 7.25 (d, J ס 9 Hz, 2H), 6.88 (d, J ס 9 Hz,
2H), 6.03–5.57 (m, 1H), 5.22–5.02 (m, 2H), 4.66 (t, J
ס 7 Hz, 1H), 3.78 (s, 3H), 2.48 (t, J ס 7 Hz, 2H),
2.08 (br s, 1H).
؀
crotylstannate (2b-Et4N )
To n-BuLi (1.68 M in hexane, 25.5 mL, 43.3 mmol)
was added N,N,NЈ,NЈ-tetramethylethylenediamine
(0.62 mL, 4.1 mmol), and the resulting solution was
stirred for 20 minutes to allow the formation of a
suspension. Then, THF (10 mL) was added to dis-
solve the precipitate, and 1,1,1,3,3,3-hexafluoro-2-
phenyl-2-propanol (3.17 mL, 20.6 mmol) was added
dropwise at 0ꢀC. After stirring of the solution over-
night at room temperature, THF (25 mL) was added
to dissolve the newly formed precipitate. To this mix-
ture was added at מ78ꢀC a THF solution of crotyl-
tin(IV) trichloride (16.9 mL, ca. 10.3 mmol content),
prepared from tin(II) chloride (2.47 g, 13.0 mmol)
and crotyl chloride (1.27 mL, 13.0 mmol) in THF (20
mL) at 0ꢀC. The resulting solution was allowed to
warm to rt and was stirred overnight. Countercation
exchange, aqueous workup, and recrystallization
(CH2Cl2-benzene) gave colorless crystals containing
benzene (4.52 g, 51%, E:Z ס 80:20). The amount of
benzene varied and excessive heating in attempts to
completely remove it led to partial decomposition.
1H NMR (CDCl3) d 8.01 (d, J ס 6.8 Hz, 3J119Sn-H ס 26.5
Hz, 2 H), 7.64 (m, 2 H), 7.39–7.24 (m, 4 H), 5.70–5.61
2-Phenyl-5-hexen-3-ol [2b,19]. 1H NMR (CDCl3)
d syn: 7.40–7.08 (m, 5H), 6.04–5.47 (m, 1H), 5.23–
4.95 (m, 2H), 3.82–3.55 (m, 1H), 2.77 (quint, J ס 7
Hz, 1H), 2.40–1.86 (m, 2H), 1.60 (br s, 1H), 1.35 (d,
J ס 7 Hz, 3H). anti: 7.40–7.08 (m, 5H), 6.04–5.47 (m,
1H), 5.23–4.95 (m, 2H), 3.82–3.55 (m, 1H), 2.77
(quint, J ס 7 Hz, 1H), 2.40–1.86 (m, 2H), 1.60 (br s,
1H), 1.30 (d, J ס 7 Hz, 3H).
1-Phenyl-5-hexen-3-ol. 1H NMR (CDCl3) d 7.40–
7.00 (m, 5H), 6.06–5.61 (m, 1H), 5.30–5.00 (m, 2H),
3.69 (quint, J ס 5 Hz, 1H), 3.10–2.60 (m, 2H), 2.34–
2.15 (m, 2H), 1.91–1.65 (m, 2H), 1.61 (s, 1H).
2-Phenyl-4-penten-2-ol.
1H NMR (CDCl3) d
7.52–7.18 (m, 5H), 5.88–5.41 (m, 1H), 5.25–4.98 (m,
2H), 2.82–2.37 (m, 2H), 2.03 (br s, 1H), 1.55 (s, 3H).
2-Methyl-1-(4-nitrophenyl)-3-buten-1-ol.
NMR (CDCl3) d anti: 8.22–8.20 (m, 2H), 7.52–7.48
1H

430 Kojima et al.
A. Tin in Organic Synthesis; Butterworths: London,
1987; (d) Nishigaichi, Y.; Takuwa, A.; Naruta, Y.; Ma-
ruyama, K. Tetrahedron 1993, 49, 7395.
(m, 2H), 5.83–5.70 (m, 1H), 5.34–5.07 (m, 2H), 4.52
(d, J ס 5 Hz, 1H), 2.50–2.28 (m, 1H), 2.28 (br s, 1H),
0.94 (d, J ס 7 Hz, 3H). syn: 8.22–8.20 (m, 2H), 7.52–
7.48 (m, 2H), 5.83–5.70 (m, 1H), 5.34–5.07 (m, 2H),
4.66 (d, J ס 6 Hz, 1H), 2.63–2.58 (m, 1H), 2.06 (br s,
1H), 0.96 (d, J ס 7 Hz, 3H).
[3] Marshall, J. A. Chem Rev 1996, 96, 31.
[4] (a) Costa, A. L.; Piazza, M. G.; Tagliavini, E.; Trom-
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1-(4-Chlorophenyl)-2-methyl-3-buten-1-ol.
1H
NMR (CDCl3) d anti: 7.33–7.23 (m, 4H), 5.81–5.70
(m, 1H), 5.23–5.19 (m, 2H), 4.35–4.33 (m, 1H), 2.58–
2.53 (m, 1H), 1.61 (br s, 1H), 0.87 (d, J ס 7 Hz, 3H).
syn: 7.33–7.23 (m, 4H), 5.81–5.70 (m, 1H), 5.10–5.04
(m, 2H), 4.63–4.60 (m, 1H), 2.83–2.78 (m, 1H), 1.97
(br s, 1H), 0.98 (d, J ס 7 Hz, 3H).
2-Methyl-1-phenyl-3-buten-1-ol [20]. 1H NMR
(CDCl3) d anti: 7.37–7.24 (m, 5H), 5.86–5.74 (m, 1H),
5.23–5.18 (m, 2H), 4.36 (d, J ס 8 Hz, 1H), 2.53–2.44
(m, 1H), 2.13 (br s, 1H), 0.87 (d, J ס 7 Hz, 3H). syn:
7.37–7.24 (m, 5H), 5.86–5.74 (m, 1H), 5.09–5.04 (m,
2H), 4.63 (d, J ס 6 Hz, 1H), 2.62–2.57 (m, 1H), 1.91
(br s, 1H), 1.01 (d, J ס 7 Hz, 3H).
[9] Martı´nez, A. G.; Barcina, J. O.; Heras, M. d. R. C.;
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Cerezo, A. d. F. Org Lett 2000, 2, 1377, and references
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1-(4-Methoxyphenyl)-2-methyl-3-buten-1-ol. 1H
NMR (CDCl3) d anti: 7.19 (d, J ס 8 Hz, 2H), 6.81 (d,
J ס 8 Hz, 2H), 5.76–5.62 (m, 1H), 5.16–5.10 (m, 1H),
4.99–4.95 (m, 1H), 4.23 (d, J ס 8 Hz, 1H), 3.74 (s,
3H), 2.41–2.35 (m, 1H), 2.03 (br s, 1H), 0.77 (d, J ס
7 Hz, 3H). syn: 7.15 (d, J ס 8 Hz, 2H), 6.80 (d, J ס
8 Hz, 2H), 5.76–5.62 (m, 1H), 5.16–5.10 (m, 1H),
4.99–4.95 (m, 1H), 4.48 (d, J ס 8 Hz, 1H), 3.74 (s,
3H), 2.51–2.46 (m, 1H), 1.79 (br s, 1H), 0.95 (d, J ס
7 Hz, 3H).
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ACKNOWLEDGMENTS
We are grateful to Central Glass Co. for supply-
ing us with 1,1-bis(trifluoromethyl)benzyl alcohol.
[17] (a) For example see: Ross, M. R.; Martin, J. C. J Am
Chem Soc 1981, 103, 1234; (b) Kojima, S.; Kajiyama,
K.; Nakamoto, M.; Akiba, K.-y. J Am Chem Soc 1996,
118, 12866; (c) Kojima, S.; Doi, Y.; Okuda, M.; Akiba,
K.-y. Organometallics 1995, 14, 1928.
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