Regio- and diastereocontrol in carbonyl allylation by 1-halobut-2-enes with tin(II) halides

Article abstract of DOI:10.1021/jo991403o

Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with tin(II) halides are described. Tin(II) bromide in a dichloromethane- water biphasic system is an effective reagent for unusual α-regioselective carbonyl allylation of 1-bromobut-2

Full text of DOI:10.1021/jo991403o

494
J . Org. Chem. 2000, 65, 494-498
Regio- a n d Dia ster eocon tr ol in Ca r bon yl Allyla tion by
1-Ha lobu t-2-en es w ith Tin (II) Ha lid es
Akihiro Ito, Masayuki Kishida, Yasuhiko Kurusu, and Yoshiro Masuyama*
Department of Chemistry, Faculty of Science and Technology, Sophia University, 7-1 Kioicho,
Chiyoda-ku, Tokyo 102-8554, J apan
Received September 7, 1999
Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with tin(II) halides are
described. Tin(II) bromide in a dichloromethane-water biphasic system is an effective reagent for
unusual R-regioselective carbonyl allylation of 1-bromobut-2-ene to produce 1-substituted pent-3-
en-1-ols. The addition of tetrabutylammonium bromide (TBABr) to the biphasic system produces
1-substituted 2-methylbut-3-en-1-ols via usual γ-addition which is opposite to the R-addition without
TBABr. The γ-addition to aromatic aldehydes exhibits anti-diastereoselectivity, while that to
aliphatic aldehydes is not diastereoselective. The allylation of benzaldehyde by 1-chlorobut-2-ene
in 1,3-dimethylimidazolidin-2-one (DMI) does not occur with tin(II) chloride or bromide but does
proceed with tin(II) iodide and exhibits γ-syn selectivity which is unusual for a Barbier-type carbonyl
allylation. In the carbonyl allylation by 1-chlorobut-2-ene with any tin(II) halide, the addition of
tetrabutylammonium iodide (TBAI) accelerates the reaction and enhances γ-syn selectivity. The
use of tin(II) iodide and TBAI produces 2-methyl-1-phenylbut-3-en-1-ol with high yield and high
syn-diastereoselectivity. The syn-diastereoselective carbonyl allylation of 1-chlorobut-2-ene using
tin(II) iodide, a catalytic amount of TBAI, and NaI in DMI-H2O is applied to various aldehydes.
In tr od u ction
lection nor γ-syn selection has been described for a
Barbier-type carbonyl allylation system. In the course of
the development of our γ-anti-selective palladium-
catalyzed carbonyl allylation of allylic alcohols with tin-
(II) chloride under Barbier-type conditions,2,4 we have
found that nonpolar solvents lead to R-regioselection,11
and a solvent such as DMSO which is strongly coordinat-
ing to the tin of an allylic tin leads to γ-syn selection.12
However, in those reactions the rates are slow and the
yields are low. Here, we report that a but-2-enyltin
intermediate, prepared from 1-bromobut-2-ene with Sn-
Br2 at the interface of a nonpolar solvent such as CH2-
Cl2 and water, causes R-regioselective carbonyl allylation,
while that prepared from 1-chlorobut-2-ene with tin(II)
iodide, tetrabutylammonium iodide, and sodium iodide
in polar solvents causes γ-syn- selective carbonyl allyla-
tion (Scheme 1).13,14
The addition of γ-substituted allylmetal reagents to
carbonyl compounds (carbonyl allylation) has been widely
developed with regio- and stereocontrol in a conforma-
tionally nonrigid acyclic system.1 Barbier-type carbonyl
allylation is particularly useful due to ease of operation
and the availability and tractability of allylic substrates,
such as allylic halides,1 esters,2,3 and alcohols.2,4 Carbonyl
allylation via (E)-γ-substituted allylmetal reagents usu-
ally proceeds with γ-anti selectivity. Thus, it is important
to develop conditions for carbonyl allylation which ex-
hibits either R-regioselectivity or γ-syn selectivity, using
(E)-γ-substituted allylmetal reagents. R-Regioselective
carbonyl allylation has been achieved either with γ-sub-
stituted allylic halidessMg/AlCl3 or Ba6 or with R- or
5
γ-substituted allylic alcoholssMe3SiCl/NaI/Sn.7 γ-Syn
selection has been attained by use of either γ-substituted
allylic trialkylsilanes8 and stannanes9 in the presence of
Lewis acids or (Z)-γ-substituted allylic metal reagents
which are troublesome to prepare.10 Neither R-regiose-
Resu lts a n d Discu ssion
r-Regioselective Ca r bon yl Allyla tion on Dich lo-
r om eth a n e-Wa ter Bip h a sic System . The regioselec-
tivity (R and γ) for producing homoallylic alcohols in
palladium-catalyzed carbonyl allylation of but-2-en-1-ol
with tin(II) chloride correlates with the dielectric constant
of solvents; the lower the polarity of the solvents, the
higher is the R-regioselectivity.11,12 However, no allyla-
tions with tin(II) chloride occur in nonpolar solvents such
as CH2Cl2 and CHCl3. The results are probably attribut-
(1) For a review, see; Yamamoto, Y.; Asano, N. Chem. Rev. 1993,
93, 2207.
(2) Masuyama, Y. In Advances in Metal-Organic Chemistry; Liebe-
skind, L. S.; J AI Press: Greenwich, CT, 1994; Vol. 3, p 255.
(3) Tamaru, Y. J . Organomet. Chem. 1999, 576, 215.
(4) Masuyama, Y. J . Synth. Org. Chem., J pn. 1992, 50, 202.
(5) Yamamoto, Y.; Maruyama, K. J . Org. Chem. 1983, 48, 1564.
(6) Yanagisawa, A.; Habaue, S.; Yasue, K.; Yamamoto, H. J . Am.
Chem. Soc. 1994, 116, 6130.
(7) Kanagawa, Y.; Nishiyama, Y.; Ishii, Y. J . Org. Chem. 1992, 57,
6988.
(8) Hayashi, T.; Kabeta, K.; Hamachi, I.; Kumada, M. Tetrahedron
Lett. 1983, 24, 2865.
(9) Yamamoto, Y.; Yatagai, H.; Naruta, Y.; Maruyama, K.; Matsu-
moto, K. J . Am. Chem. Soc. 1980, 102, 7107.
(11) Masuyama, Y.; Hayakawa, A.; Kurusu, Y. J . Chem. Soc., Chem.
Commun. 1992, 1102; Masuyama, Y.; Hayakawa, A.; Kishida, M.;
Kurusu, Y. Inorg. Chim. Acta 1994, 220, 155.
(10) Hoffmann, R. W.; Zeiss, H. J . Angew. Chem., Int. Ed. Engl.
1982, 21, 372; Koreeda, M.; Tanaka, Y. J . Chem. Soc., Chem. Commun.
1982, 845; Yamamoto, Y.; Maruyama, K.; Matsumoto, K. J . Chem. Soc.,
Chem. Commun. 1983, 742; Hoppe, D.; Lichtenberg, F. Angew. Chem.,
Int. Ed. Engl. 1984, 23, 239; Kobayashi, S.; Nishino, K. J . Org. Chem.
1994, 59, 6620.
(12) Takahara, J . P.; Masuyama, Y.; Kurusu, Y. J . Am. Chem. Soc.
1992, 114, 2577.
(13) Preliminary report: Masuyama, Y.; Kishida, M.; Kurusu, Y.
J . Chem. Soc., Chem. Commun. 1995, 1405.
(14) Preliminary report: Masuyama, Y.; Kishida, M.; Kurusu, Y.
Tetrahedron Lett. 1996, 37, 7103.
10.1021/jo991403o CCC: $19.00 © 2000 American Chemical Society
Published on Web 12/31/1999

Carbonyl Allylation by 1-Halobut-2-enes
J . Org. Chem., Vol. 65, No. 2, 2000 495
Sch em e 1
did not lead to a remarkable inversion in regioselection
(entries 18 and 20). The dependence of R-regioselection
upon reaction temperature (10-35 °C) was thus inves-
tigated in the allylation of benzaldehyde by 1 (X ) Br)
on a dichloromethane-water biphasic system; as the
reaction temperature rose, the R-regioselectivity was
enhanced (10 °C, R:γ ) 35:65; 23 °C, R:γ ) 68:32; 35 °C,
R:γ ) 92:8). The R-regioselection using an aliphatic
aldehyde, heptanal, was not influenced by reaction tem-
perature over the range studied.
Sch em e 2
Plausible mechanisms, which explain the R-regiose-
lection observed without TBABr and the γ-regioselection
observed with TBABr are shown in Scheme 3. In the
presence of more than one equimolar amount of TBABr,
SnBr2 is transformed into nucleophilic tetrabutylammo-
nium tribromostannate (Bu4N+ SnBr3-) in H2O. The
tribromostannate probably reacts with 1-bromobut-2-ene
in CH2Cl2 to produce but-2-enyltribromotin, which causes
γ-addition to aldehyde via a six-membered cyclic chair
transition state (B). On the other hand, in the absence
of TBABr, slightly nucleophilic µ-bromoditin [Br2Sn-Br-
SnBr2]- may be derived from 3SnBr2.15 The reaction of
the µ-bromoditin with 1-bromobut-2-ene at the CH2Cl2-
H2O interface may form a but-2-enyl(µ-bromo)ditin in-
termediate which causes R-regioselective carbonyl ally-
lation via a chair-formed six-membered cyclic transition
state (A) containing µ-bromoditin.
In flu en ce of Ha logen s of Bu t-2-en yltr ih a lotin s
u p on Dia ster eoselection . The γ-regioselective carbonyl
allylation by 1 (X ) Br) with SnBr2 and TBABr led to
modest syn-diastereoselection, in contrast to usual anti-
diastereoselection in the carbonyl allylation with SnCl2,12
as shown in Table 1. The influence of halogens on the
tin of actual allylic reagents, but-2-enylpolyhalotins, upon
the diastereoselection of the γ-regioselective allylation of
benzaldehyde (2, R ) Ph) by 1-halobut-2-enes 1 with tin-
(II) halides (SnX′2) and tetrabutylammonium halides
(TBAX′′) was thus investigated.16 The results are sum-
marized in Table 2. The carbonyl allylation by 1 (X )
Br, E:Z ) 85:15) with SnCl2 led to usual anti-selection
(entry 1), and that with SnI2 led to unusual syn-selection
(entry 5). By adding the result of the carbonyl allylation
with SnBr2 (entry 3), the diastereoselection was pre-
sumed to be dependent upon the electronegativity of
halogens of but-2-enyltrihalotins. Addition of TBABr
enhanced the syn-selectivity in the carbonyl allylation
with any SnX′2 (entries 1-6). These results suggest that
but-2-enyltin intermediates in the presence of TBABr are
different from usual but-2-enyltrihalotins in the absence
of TBABr; but-2-enyltin intermediates in the presence
of TBABr may be pentacoordinated anionic but-2-enyltet-
rahalostannates. The use of TBAI instead of TBABr
moreover enhanced the syn-selectivity (entries 7 and 8).
Plausible mechanisms for either γ-syn- or γ-anti-selective
carbonyl allylation by 1 (X ) Br) are illustrated in
Scheme 4.17 The γ-anti-selective carbonyl allylation with
SnCl2 likely proceeds via the usual six-membered cyclic
chair transition state (C) between (E)-but-2-enylbromo-
dichlorotin and benzaldehyde (R ) Ph), because the tin
able to the insolubility of tin(II) chloride in CH2Cl2 or
CHCl3. Tin(II) halides are soluble in water. Thus, we
aimed at carbonyl allylation on biphasic system; the
preparation of but-2-enyltin intermediate from 1-halobut-
2-ene 1 and tin(II) halide at the interface of a nonpolar
solvent, such as CH2Cl2, and water followed by the
carbonyl allylation by the but-2-enyltin intermediate in
CH2Cl2. The results of the allylation of heptanal on the
biphasic system are illustrated with Scheme 2. No
allylation of heptanal by 1-bromobut-2-ene (1; X ) Br)
with tin(II) bromide was observed at 25 °C in CH2Cl2. A
dichloromethane-water biphasic system allowed the
allylation by 1 (X ) Br) with tin(II) bromide to proceed
with high R-regioselectivity (method A), in contrast to the
γ-regioselectivity in polar solvents such as DMF and 1,3-
dimethylimidazolidin-2-one (DMI). Addition of tetrabut-
ylammonium bromide (TBABr) promoted the biphasic
allylation and reversed the regioselection (method B). The
use of either tin(II) chloride instead of tin(II) bromide
(25%, 3R:3γ ) 81:19) or the use of 1-chlorobut-2-ene (1;
X ) Cl) instead of 1-bromobut-2-ene (1; X ) Br) (28%,
3R:3γ ) 65:35) depressed the reactivity and the R-regi-
oselectivity in the biphasic allylation. The allylation also
occurred in only water without a cosolvent and was
R-regioselective (36%, 3R:3γ ) 77:23). The use of chlo-
roform (78%, 3R:3γ ) 56:44) or ether (73%, 3R:3γ ) 13:
87) instead of dichloromethane in the biphasic system
enhanced the yield and lowered the R-regioselectivity.
The regioselective allylation of various aldehydes 2 by
1 (X ) Br) with tin(II) bromide was carried out at 25 °C
in dichloromethane-water either in the absence of
TBABr (method A) or in the presence of TBABr (method
B), as shown in Table 1. Most of the aldehydes, such as
benzaldehyde, aromatic aldehydes bearing an electron-
donating group, and aliphatic aldehydes can be used for
both R- and γ-regioselective allylations (entries 1-14).
This biphasic system is a method of greater utility for
achieving R-regioselection since it is rarer than γ-regi-
oselection. The allylation of benzaldehydes bearing elec-
tron-withdrawing groups such as chloro, methoxycarbo-
nyl, and cyano groups exhibited no R-regioselection even
in the absence of TBABr (entries 15, 17, and 19).
4-Chlorobenzaldehyde completely underwent γ-regiose-
lective allylation without TBABr at 10 °C. On the other
hand, the allylation of 4-chlorobenzaldehyde at 32-35
°C exhibited R-regioselectivity (entry 16). Strongly electron-
withdrawing groups such as methoxycarbonyl and cyano
(15) Donaldson, J . D. Prog. Inorg. Chem. 1967, 8, 287.
(16) For the γ-syn-selective carbonyl allylation by 1 (X ) Br), see
ref 14.
(17) For reaction mechanisms in γ-syn- or γ-anti-selective carbonyl
allylations by but-2-enyltins, see reviews: Nishigaichi, Y.; Takuwa,
A.; Naruta, Y.; Maruyama, K. Tetrahedron 1993, 49, 7395; Marshall,
J . A. Chem. Rev. 1996, 96, 31.

496 J . Org. Chem., Vol. 65, No. 2, 2000
Ta ble 1. Regioselective Allyla tion of Va r iou s Ald eh yd es by 1 (X ) Br ) w ith Sn Br 2
Ito et al.
a
entry
R
methodb
time (h)
yieldc (%)
R (E:Z):γ(syn:anti)d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
C6H5
C6H5
A
24
24
24
24
24
24
75
24
24
25
50
26
31
24
68
48
46
48
46
48
60
83
66
70
61
99
98
83
68
75
76
79
60
38
83
38
75
33
95
36
94 (85:15):6 (90:10)
5 (89:11):95 (33:67)
86 (97:3):14 (36:64)
10 (93:7):90 (31:69)
92 (58:42):8(79:21)
7 (62:38):93 (57:43)
87 (64:36):13 (62:38)
9 (62:38):91 (51:49)
92 (66:34):8 (79:21)
1g:99 (53:47)
Be
A
4-CH3C6H4
4-CH3C6H4
C6H5CH2CH2
C6H5CH2CH2
C6H13
Be
A
B
A
B
C6H13
H2CdCH(CH2)8
H2CdCH(CH2)8
c-C6H11
c-C6H11
(CH3)3C
(CH3)3C
4-ClC6H4
4-ClC6H4
4-CH3OOCC6H4
4-CH3OOCC6H4
4-NCC6H4
4-NCC6H4
A
Bf
A
92 (80:20):8 (28:72)
Bf
A
2g:98 (30:70)
89 (18:82):11g
Be
A
31 (37:63):69 (76:24)
11 (50:50):89 (15:85)
87 (83:17):13 (37:63)
18 (77:23):82 (8:92)
52 (61:39):48 (74:26)
0:∼100 (11:89)
Ah
A
Ah
A
Ah
25 (81:19):75 (51:49)
a
The allylation of aldehydes (1 mmol) by 1-bromobut-2-ene (2 mmol) was carried out with SnBr2 (2 mmol) in CH2Cl2 (3 mL) and H2O
(3 mL) at 25 °C. bA: Without TBABr. B: After the solution of 1 and SnBr2 was stirred with TBABr (1 mmol) for 2 h, 2 was added.
cIsolated yields. dThe ratio was determined by 1H NMR (J EOL GX-270) and by GC (capillary column PEG 20M, 0.25 mm × 30 m). H2O
e
(6 mL) was used as a solvent. fCH2Cl2 (1 mL) and H2O (5 mL) were used as solvents. gThe ratio (E:Z or syn:anti) was not confirmed. hThe
reaction was carried out at 32-35 °C.
Sch em e 3
Sch em e 4
of but-2-enylbromodichlorotin is Lewis acidic.12 In con-
trast, the γ-syn-selection with SnI2 does not suggest a
six-membered cyclic transition state, but rather an acyclic
antiperiplanar transition state (D), because no (Z)-but-
2-enyltin intermediate has been prepared from (E)-rich
1-bromobut-2-ene.1 That is to say, the weak Lewis acidity
of tin in but-2-enylbromodiiodotin, which is based on low
electronegativity of iodine, probably disfavors the forma-
tion of the six-membered cyclic transition state.18 The
enhancement of the syn-selectivity by the addition of
TBAI can be explained by non-Lewis acidity of tin in
pentacoordinated anionic but-2-enylbromotriiodostan-
nate.19
selectivity (entries 9, 12, and 15). The addition of TBABr
or TBAI to the reaction conditions of entries 9 and 12
enabled the carbonyl allylation by 1 (X ) Cl); TBAI
particularly accelerated the allylation (entries 10, 11, 13,
and 14). The combination of SnI2 and TBAI led to high
reactivity and high syn-selectivity in the carbonyl ally-
lation by 1 (X ) Cl) (entry 17). The allylation with a
catalytic amount of TBAI and an equimolar amount of
NaI to 1 (X ) Cl) exhibited the same reactivity and syn-
selectivity as those stoichiometric in TBAI (entry 18). The
absence of water decreased both the yield and the syn-
selectivity (entry 19). The allylation by 1 (X ) Cl) with
The carbonyl allylation by 1 (X ) Cl) did not occur with
SnCl2 or SnBr2 but with SnI2 accompanied by syn-
(18) Tin(IV) compounds, prepared in the initial stage by the hy-
drolysis of products, 2-methyl-1-phenylbut-3-enyloxybromodiiodotin,
may function as a Lewis acid in the reaction of but-2-enylbromodi-
iodotin which is hard to form by the six-membered cyclic transition
state.
(19) Pentacoordination of aromatic diolate or fluoride to silicon or
tin of allylic silanes and tins usually promotes carbonyl allylations to
lead to γ-anti-selection via six-membered cyclic transition states:
Sakurai, H. Synlett 1989, 1. Denmark, S. E.; Coe, D. M.; Pratt, N. E.;
Griedel, B. D. J . Org. Chem. 1994, 59, 6161.

Carbonyl Allylation by 1-Halobut-2-enes
J . Org. Chem., Vol. 65, No. 2, 2000 497
Ta ble 2. Syn -Dia ster eoselective Allyla tion of
Ta ble 3. Syn -Dia ster eoselective Ca r bon yl Allyla tion by 1
(X ) Cl)a
Ben za ld eh yd e by 1 w ith Tin (II) Ha lid esa
entry
X
X′
Br Cl none THF
Br Cl Br THF
Br Br none THF
Br Br Br THF
none THF
X′′
solvent time (h) yieldb (%) syn:antic
entry
R
time (h)
yieldb (%)
syn:antic
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
24
24
23
22
15
15
17
18
72
72
48
72
53
45
64
48
40
41
91
94
92
70
43
43
63
58
75
68
55
78
90
88
N.R.
14
80
N.R.
39
80
53
56
80
83
60
10
70
84
82
85
16:84
52:48
42:58
77:23
73:27
84:16
81:19
87:13
-
1
2
3
4
5
6
7
8
9
4-ClC6H4
4-NCC6H4
42
50
72
50
42
50
47
45
40
47
90
94
93
85
82
85
81
65
76
76
91:9
91:9
93:7
85:15
92:8
83:17
68:32
77:23
77:23
60:40
4-CH3OOCC6H4
4-CH3OC6H4
4-CH3C6H4
C6H5CHdCH
C6H5CH2CH2
H2CdCH(CH2)8
C6H13
Br
Br
Br
Br
I
I
I
I
Br
Br
I
THF
DMI
DMI
Cl Cl none DMI
Cl Cl Br
Cl Cl
Cl Br none DMI
Cl Br Br
Cl Br
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
DMI
DMI
40:60
59:41
-
10
c-C6H11
I
a
The allylation of aldehydes (1 mmol) by 1-chlorobut-2-ene (2
mmol) was carried out with SnI2 (2 mmol), TBAI (0.2 mmol), and
NaI (2 mmol) in DMI (3 mL) and H2O (0.1 mL) at 25 °C. bIsolated
DMI
DMI
47:53
82:18
82:18
85:15
90:10
89:11
69:31
81:19f
75:25g
83:17
87:13
78:22
I
I
I
I
I
I
I
I
I
I
I
none DMI
c
yield. The ratio was determined by 1H NMR (J EOL Λ-500) and/
Br
I
DMI
DMI
DMI
or GC (capillary column PEG 20M, 0.25 mm × 30 m).
Id
I
DMIe
Et2Oe
CH2Cl2
THF
1:3-bromobut-1-ene ) ca. 73:13:14]. (E)-1-chlorobut-2-ene (1,
X ) Cl) was also purchased from Tokyo Chemical Industry
Co., Ltd. The 1-halobut-2-enes and aldehydes used were
commercial samples purified by distillation or recrystallization.
Diastereomer ratios were determined by 1H NMR and GC
analysis (accuracy (1%).
Id
Id
Id
Id
Id
e
DMF
DMSO
a
The allylation of benzaldehyde (1 mmol) by 1-halobut-2-ene
(2 mmol) was carried out with SnX′2 (2 mmol) and TBAX′′ (2 mmol)
in solvent (3 mL) and H2O (0.1 mL) at 25 °C. bIsolated yield. cThe
ratio was determined by 1H NMR (J EOL GX-270 or Λ-500) and
by GC (capillary column PEG 20M, 0.25 mm × 30 m). dThe
reaction was carried out with TBAI (0.2 mmol) and NaI (2.0 mmol).
r-Regioselective Ca r bon yl Allyla tion by 1-Br om obu t-
2-en e w ith Sn Br 2. A typical procedure is as follows: To a
solution of SnBr2 (0.56 g, 2 mmol) and 1-bromobut-2-ene (0.27
g, 2 mmol) in CH2Cl2 (3 mL)-H2O (3 mL) was added heptanal
(0.11 g, 1 mmol) at ambient temperature under a nitrogen
atmosphere. After being stirred for 24 h, the mixture was
diluted with 120 mL of a mixed solvent (ether:dichloromethane
) 2:1) and washed successively with aqueous 10% HCl solution
(10 mL), aqueous NaHCO3 solution (10 mL), water (10 mL),
and brine (10 mL). The extracts were dried over anhydrous
MgSO4. Then evaporation of solvent and purification by
column chromatography on silica gel (hexane:ethyl acetate )
7:1) afforded 0.082 g (0.48 mmol, 48%) of undec-2-en-5-ol as a
colorless oil.
eThe reaction was carried out without H2O. γ:R ) 98:2. gγ:R )
95:5.
f
SnI2 and TBAI occurred in nonpolar solvents such as
diethyl ether and CH2Cl2, despite the low solubility of
SnI2 (entries 20 and 21). Polar solvents such as THF,
DMF, and DMSO can be used for the γ-syn-selective
carbonyl allylation (entries 22-24).
γ-Syn -Selective Ca r bon yl Allyla tion . As shown in
Table 3, the syn-selective allylation of various aldehydes
2 was investigated under the same conditions as those
which gave highest syn-selectivity in the allylation of
benzaldehyde by 1 (X ) Cl) (entry 17 in Table 2).
Aromatic aldehydes, bearing either an electron-donating
group or an electron-withdrawing group, and R,â-
unsaturated aldehydes can be used in the syn-selective
allylation. Aliphatic aldehydes, especially 3-phenylpro-
panal and cyclohexanecarbaldehyde, underwent allyla-
tion but syn-selectivity was poor (entries 7 and 10).
γ-syn -Select ive Ca r bon yl Allyla t ion by 1-Ch lor ob u t -
2-en e w ith Sn I2 a n d TBAI. A typical procedure is as
follows: To a solution of SnI2 (0.74 g, 2.0 mmol), TBAI (0.074
g, 0.20 mmol), and NaI (0.30 g, 2.0 mmol) in DMI (3 mL)-H2O
(0.1 mL) was added 1-chlorobut-2-ene (0.19 mL, 2.0 mmol)
followed by benzaldehyde (0.10 mL, 1.0 mmol) at ambient
temperature under a nitrogen atmosphere. After being stirred
for 41 h, the mixture was diluted with CH2Cl2 (100 mL) and
was washed successively with aqueous 10% HCl solution (10
mL), aqueous NaHCO3 solution (10 mL), water (10 mL), and
brine (10 mL). The extracts were dried over anhydrous MgSO4.
Then evaporation of CH2Cl2 and purification by column
chromatography on silica gel (hexane:ethyl acetate ) 10:1)
afforded 0.13 g (0.83 mmol, 83%) of 2-methyl-1-phenylbut-3-
en-1-ol as a colorless oil.
In summary, the carbonyl allylation by 1-bromobut-2-
ene with SnBr2 in CH2Cl2-H2O at 25-32 °C proceeds
with R-regioselection to produce 1-substituted pent-3-en-
1-ols, while that by 1-chlorobut-2-ene with SnI2, TBAI,
and NaI in DMI-H2O at 25 °C undergoes γ-syn-selection
to produce syn 1-substituted 2-methylbut-3-en-1-ols.
The structures of the following alcohols were confirmed by
the comparison of spectroscopic values with those of authentic
samples in the literature: 1-phenylpent-3-en-1-ol,20 2-methyl-
(20) Yamamoto, Y.; Yatagi, H.; Ishihara, Y.; Maeda, N.; Maruyama,
K. Tetrahedron 1983, 40, 2239.
(21) Yamamoto, Y.; Yatagi, H.; Maruyama, K. J . Am. Chem. Soc.
1981, 103, 1969.
(22) Auge, J .; David, S. Tetrahedron Lett. 1983, 24, 4009.
(23) Wilson, S. R.; Guazzaroni, M. E. J . Org. Chem. 1989, 54, 3087.
(24) Gambaro, A.; Gain, P.; Marton, D.; Peruzzo, V.; Tagliavini, G.
J . Organomet. Chem. 1982, 231, 307.
Exp er im en ta l Section
Gen er a l. All solvents had been dried over desiccant and
had been distilled before being used. 1-Bromobut-2-ene (1, X
) Br), which has been purchased from Tokyo Chemical
Industry Co., Ltd., contains 14% 3-bromobut-1-ene [(E)-1:(Z)-

498 J . Org. Chem., Vol. 65, No. 2, 2000
Ito et al.
1-phenylbut-3-en-1-ol,21 1-(4-chlorophenyl)-2methylbut-3-en-
1-ol,12 1-[4-(methoxycarbonyl)phenyl]-2-methylbut-3-en-1-ol,12
1-(4-methoxyphenyl)-2-methylbut-3-en-1-ol,12 4-methyl-1-phen-
ylhex-1(E),5-dien-3-ol,22 1-cyclohexyl-2-methylbut-3-en-1-ol,12
1-cyclohexylpent-3-en-1-ol,12 3-methyldec-1-en4-ol,23 2,2-di-
methylhept-5-en-3-ol.24 The characterization data of new
compounds are present in the Supporting Information: R and
γ mixtures of 3 [R ) C6H13, 4-CH3C6H4, C6H5CH2CH2, and
H2CdCH(CH2)8] in Table 1.
Su p p or tin g In for m a tion Ava ila ble: Characterization
data for compounds 3 [RdC6H13, 4-CH3C6H4, C6H5CH2CH2,
and H2CdCH(CH2)8] in Table 1, and details of R-regioselection
depending upon reaction temperature (10-35 °C) in the
allylation of benzaldehyde by 1 (X ) Br) on a dichloromethane-
water biphasic system. This material is available free of charge
via the Internet at http://pubs.acs.org.
J O991403O