Cobalt-catalyzed allylzincations of internal alkynes

Article abstract of DOI:10.1246/bcsj.79.1271

Cobalt salts such as cobalt(II) chloride catalyze allylzincation reactions of 1-aryl-1-alkynes. The allylzincations proceed in a syn fashion to form 2-allyl-1-aryl-1-alkenylzinc species. Other internal alkynes such as 6-dodecyne or 2-nonyn-1-ol are much l

Full text of DOI:10.1246/bcsj.79.1271

Ó 2006 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 79, No. 8, 1271–1274 (2006) 1271
Cobalt-Catalyzed Allylzincations of Internal Alkynes
ꢀ
ꢀ
Hiroto Yasui, Toshihiro Nishikawa, Hideki Yorimitsu, and Koichiro Oshima
Department of Material Chemistry, Graduate School of Engineering, Kyoto University,
Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510
Received February 14, 2006; E-mail: yori@orgrxn.mbox.media.kyoto-u.ac.jp
Cobalt salts such as cobalt(II) chloride catalyze allylzincation reactions of 1-aryl-1-alkynes. The allylzincations
proceed in a syn fashion to form 2-allyl-1-aryl-1-alkenylzinc species. Other internal alkynes such as 6-dodecyne or
2-nonyn-1-ol are much less reactive than 1-aryl-1-alkynes.
Due to the importance of allylic groups, allylmetalation re-
actions of alkynes and alkenes represent powerful methods for
the construction of complex organic molecules.1 Among them,
allylzincation reactions of internal alkynes are rather difficult
processes.1f,2 We have been interested in allylation reactions
under cobalt catalysis.3 Here, we report cobalt-catalyzed allyl-
zincation reactions of internal alkynes.4
A variety of internal alkynes were subjected to the cobalt-
catalyzed allylzincation reaction (Table 1). An electron-donat-
ing substituent on the aromatic ring rendered the reaction less
efficient (Entry 1). On the other hand, 1-aryl-1-alkynes having
electron-withdrawing groups underwent the allylzincation to
yield the corresponding products in high yields (Entries 2–5).
Unfortunately, an attempted allylzincation reaction of 1,2-di-
phenylacetylene (1g) provided the desired product 2g in only
41% yield (Entry 6). The allylzincation reaction of 6-dodecyne
(1h) and the homopropargyl methyl ether 1i afforded the cor-
responding products in only 18 and 34% yields, respectively
(Entries 7 and 8). The allylzincation reaction of 3-phenyl-2-
propyn-1-ol (1j) gave a mixture of the allylzincation products
3a and 4a, albeit the yield was low (Eq. 2). The formation
of 4a was often observed in the previous allylmetalation reac-
tions.1a,5 Similarly, a mixture of 3b and 4b was formed in the
reaction of 2-nonyn-1-ol (1k).
Results and Discussion
As a model substrate, 1-phenyl-1-octyne (1a) was subjected
to various conditions for cobalt-catalyzed allylzincation reac-
tion (Eq. 1). Treatment of 1a with 4 equiv of allylzinc bromide
in the presence of 5 mol % of cobalt(II) chloride in THF at
room temperature for 48 h provided the corresponding allyl-
ated product 2a in 64% yield. No traces of regio- or stereoiso-
mers were obtained. The formation of 2-allyl-1-aryl-1-alkenyl-
zinc species was confirmed by quantitative deuterium incorpo-
ration upon quenching with deuterated hydrochloric acid. THF
was chosen as the solvent. Other solvents such as toluene, hex-
ane, and Et2O resulted in a slight decrease of the yield of 2a.
Cobalt(II) bromide, (8-quinolinolato)cobalt(II), and acetylace-
tonatocobalt(III) also catalyzed the reaction to provide 2a in
64, 59, and 53% yields, respectively. Cobalt(II) fluoride did
not promote the allylzincation reaction. In the presence of a
phosphine ligand, the yield of 2a was significantly decreased
(13% with 5 mol % of PPh3). The reaction did not go to com-
pletion when the reaction was carried out for 24 h (53% yield).
A smaller amount, 3.0 equiv for instance, of allylzinc bromide
also furnished a 56% yield of 2a. The use of 10 equiv of allyl-
zinc bromide slightly increased the yield of 2a to 73%. Reac-
tion at 40 ꢁC gave rise to a lower conversion of 1a (43% recov-
ery) and 30% of 2a was obtained, probably because the cobalt
catalyst lost its activity upon heating. In the absence of a
cobalt(II) catalyst, the reaction did not occur and the starting
material remained untouched. It is noteworthy that the use of
allylmagnesium bromide instead of allylzinc bromide resulted
in no conversion of 1a.
5 mol% CoCl
5 equiv
2
R
OH
H
R
OH
ZnBr
R
C C
+
H
THF, r. t., 48 h
+
OH
ð2Þ
then H O
3
3
4
1j : R = Ph
from 1j : 37% yield (3a/4a = 87:13)
from 1k: 24% yield (3b/4b = 89:11)
n
1k : R = C H
6
13
The reaction of 1f with substituted allylic zinc reagents was
studied. 2-Methyl-2-propenylzinc bromide reacted with 1f
Table 1. Cobalt-Catalyzed Allylzincation Reactions of In-
ternal Alkynes
5 mol% CoCl
4 equiv
2
1
2
R
R
ZnBr
1
2
R
C C R
THF, r. t., 48 h
+
H
1
2
then H O
3
Entry
1
R1
R2
Yield of 2/%
1
2
3
4
5
6
7
8
1b
1c
1d
1e
1f
1g
1h
1i
nC6H13
nC6H13
nC6H13
nC6H13
nC6H13
Ph
4-MeO-C6H4
4-Cl-C6H4
4-F-C6H4
4-CF3-C6H4
3,5-(CF3)2-C6H3
Ph
nC5H11
CH2CH2OMe
2b, 51
2c, 67
2d, 70
2e, 73
2f, 73
2g, 41
2h, 18
2i, 34
5 mol% CoCl
4 equiv
2
n
ZnBr
C H
Ph
H
6
13
n
ð1Þ
C H
C
C Ph
6
13
nC5H11
nC6H13
THF, r. t., 48 h
+
1a
then H O
3
2a 64%
Published on the web August 7, 2006; doi:10.1246/bcsj.79.1271

1272 Bull. Chem. Soc. Jpn. Vol. 79, No. 8 (2006)
Cobalt-Catalyzed Allylzincations
the conventional Sonogashira coupling reaction or were commer-
cially available. Allylic zinc reagents were prepared and titrated
according to the literature.3a
Typical Procedure for the Cobalt-Catalyzed Allylzincation
of Internal Alkynes. The synthesis of 7 is representative. Co-
balt(II) chloride (3.2 mg, 0.025 mmol) was placed in a 20 mL re-
action flask under argon. A solution of 1f (161 mg, 0.50 mmol
in 1 mL of THF) was added to the reaction flask. A solution of
allylzinc bromide (1.50 mL, 1.34 M THF solution, 2.0 mmol) was
added at room temperature. The mixture was stirred for 48 h at
5 mol% CoCl
4 equiv
2
n
C H
Ar
1c
or
1f
6
13
ZnBr
ZnX
THF, r. t., 48 h
20 mol% CuCN•2LiCl
Br
5 equiv I
2
5 equiv
CF
3
n
C H
Ar
I
6
13
CF
3
room temperature. Allyl bromide (0.22 mL, 2.5 mmol) and CuCN
ꢂ
n
C H
6
13
2LiCl (0.1 mL, 1.0 M THF solution, 0.1 mmol) were then added.
The resulting mixture was stirred for an additional 3 h. The mixture
was poured into 1 M hydrochloric acid. The organic compounds
were extracted with ether three times. The combined organic part
was dried and concentrated in vacuo. Chromatographic purifica-
tion on silica gel afforded 7 (142 mg, 0.35 mmol) in 70% yield.
Characterization Data: The spectral data of the products 2g,6
2i,7 3a,8 3b,7 and 4a9 can be found in the literature. The stereo-
chemistry of 2a6,9,10 and 2h11 was determined by comparison with
their closely related analogues. The stereochemistry of 2b–2f are
tentatively assigned compared to that of 2a.
from 1f:
7 70%
from 1c : 6a 56%
from 1f : 6b 60%
Scheme 1. Reactions of alkenylzinc intermediates.
under catalysis of CoCl2 to afford 5 in 52% yield (Eq. 3). An
attempt to use a 2-butenylzinc reagent resulted in the forma-
tion of a complex mixture.
CF
3
5 mol% CoCl
4 equiv
2
1-[3,5-Bis(trifluoromethyl)phenyl]-1-octyne (1f): IR (neat)
2936, 2862, 2232, 1464, 1385, 1279, 1234, 1180, 1138, 1106,
896, 848, 701, 684 cmꢃ1; 1H NMR (CDCl3) ꢀ 0.91 (t, J ¼ 7:5 Hz,
3H), 1.31–1.35 (m, 4H), 1.42–1.48 (m, 2H), 1.62 (tt, J ¼ 7:5,
7.5 Hz, 2H), 2.43 (t, J ¼ 7:5 Hz, 2H), 7.74 (s, 1H), 7.81 (s, 2H);
13C NMR (CDCl3) ꢀ 14.04, 19.34, 22.53, 28.34, 28.62, 31.31,
78.05, 94.65, 120.83 (m), 123.02 (q, J ¼ 271:5 Hz), 126.39,
131.47 (m), 131.66 (q, J ¼ 33:4 Hz); Found: C, 59.63; H, 5.02%.
Calcd for C16H16F6: C, 59.63; H, 5.00%.
CF
3
n
ð3Þ
ZnBr
C H
6
13
1f
THF, r. t., 48 h
H
+
5 52%
then H O
3
The intermediary alkenylzinc compounds obtained by the
allylzincation reaction reacted with electrophiles (Scheme 1).
The cobalt-catalyzed allylzincations of 1c and 1f followed
by the addition of iodine provided the corresponding tetrasub-
stituted alkenes 6 in moderate yields. Copper(I) cyanide medi-
ated a carbon–carbon bond formation reaction with allyl bro-
mide.
In conclusion, cobalt salts such as cobalt(II) chloride proved
to catalyze the allylzincation reaction of 1-aryl-1-alkynes effi-
ciently. The cobalt catalysis did not efficiently promote the
allylzincation reactions of other internal alkynes such as 6-
dodecyne and propargylic alcohols.
(E)-2-Hexyl-1-phenyl-1,4-pentadiene (2a): IR (neat) 2956,
1
2927, 2857, 1466, 995, 913, 748, 699 cmꢃ1; H NMR (CDCl3) ꢀ
0.87 (t, J ¼ 7:0 Hz, 3H), 1.22–1.31 (m, 6H), 1.44–1.50 (m, 2H),
2.22 (t, J ¼ 6:0 Hz, 2H), 2.91 (d, J ¼ 7:0 Hz, 2H), 5.07–5.14 (m,
2H), 5.88 (ddt, J ¼ 17:0, 10.0, 7.0 Hz, 1H), 6.28 (s, 1H), 7.17–
7.21 (m, 3H), 7.29–7.32 (m, 2H); 13C NMR (CDCl3) ꢀ 14.07,
22.60, 28.10, 29.38, 30.83, 31.62, 41.73, 116.25, 125.82, 125.94,
128.03, 128.56, 136.70, 138.41, 141.95; Found: C, 89.54; H,
10.67%. Calcd for C17H24: C, 89.41; H, 10.59%.
(E)-2-Hexyl-1-(4-methoxyphenyl)-1,4-pentadiene (2b): IR
Experimental
General. 1H NMR (500 MHz) and 13C NMR (125.7 MHz)
spectra were taken on a Varian UNITY INOVA 500 spectrometer
(neat) 2955, 2929, 1609, 1511, 1464, 1249, 1176, 1039, 911 cmꢃ1
;
1H NMR (CDCl3) ꢀ 0.89 (t, J ¼ 7:5 Hz, 3H), 1.21–1.34 (m, 6H),
1.44–1.51 (m, 2H), 2.22 (t, J ¼ 8:0 Hz, 2H), 2.90 (d, J ¼ 6:5 Hz,
2H), 3.82 (s, 3H), 5.08–5.15 (m, 2H), 5.89 (ddt, J ¼ 17:5, 10.0,
6.5 Hz, 1H), 6.23 (s, 1H), 6.87 (d, J ¼ 8:5 Hz, 2H), 7.16 (d, J ¼
8:5 Hz, 2H); 13C NMR (CDCl3) ꢀ 14.09, 22.62, 28.10, 29.43,
30.81, 31.65, 41.83, 55.20, 113.44, 116.10, 125.22, 129.65,
130.97, 136.88, 140.59, 157.75; Found: C, 83.45; H, 9.98%. Calcd
for C18H26O: C, 83.67; H, 10.14%.
1
unless otherwise noted. H NMR and 13C NMR spectra were ob-
tained in CDCl3 with tetramethylsilane as an internal standard.
Chemical shifts (ꢀ) are in parts per million relative to tetramethyl-
silane at 0.00 ppm for 1H and relative to CDCl3 at 77.2 ppm
2
for 13C unless otherwise noted. H NMR (46 MHz) spectra were
measured on a Varian Mercury 300 spectrometer in CHCl3 with
1,1,2,2-tetrachloroethane-d2 as an internal standard. IR spectra
were determined on a Shimadzu FTIR-8200PC spectrometer.
Mass spectra were determined on a JEOL Mstation 700 spectrom-
eter. TLC analyses were performed on commercial glass plates
bearing 0.25-mm layer of Merck silica gel 60F254. Silica gel
(Wakogel 200 mesh) was used for column chromatography. The
analyses were carried out at the Elemental Analysis Center of
Kyoto University.
Unless otherwise noted, materials obtained from commercial
suppliers were used without further purification. THF and ether
were purchased from Kanto Chemical Co., stored under nitrogen,
and used as provided. The starting materials 1 were prepared by
(E)-1-(4-Chlorophenyl)-2-hexyl-1,4-pentadiene (2c):
;
IR
(neat) 2958, 2927, 2857, 1490, 1093, 1015, 914 cmꢃ1 1H NMR
(CDCl3) ꢀ 0.87 (t, J ¼ 7:5 Hz, 3H), 1.21–1.31 (m, 6H), 1.42–
1.48 (m, 2H), 2.18 (t, J ¼ 8:0 Hz, 2H), 2.90 (dd, J ¼ 7:0, 1.5 Hz,
2H), 5.08–5.14 (m, 2H), 5.86 (ddt, J ¼ 17:0, 10.0, 7.0 Hz, 1H),
6.21 (s, 1H), 7.12 (d, J ¼ 8:0 Hz, 2H), 7.27 (d, J ¼ 8:0 Hz, 2H);
13C NMR (CDCl3) ꢀ 14.07, 22.59, 28.01, 29.34, 30.82, 31.59,
41.67, 116.48, 124.63, 128.17, 129.86, 131.60, 136.40, 136.84,
142.81; Found: C, 77.96; H, 8.81%. Calcd for C17H23Cl: C, 77.69;
H, 8.82%.
(E)-1-(4-Fluorophenyl)-2-hexyl-1,4-pentadiene (2d):
IR
;
(neat) 2928, 2858, 1603, 1505, 1229, 1156, 913, 837, 823 cmꢃ1

H. Yasui et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 8 (2006) 1273
1H NMR (CDCl3) ꢀ 0.87 (t, J ¼ 7:0 Hz, 3H), 1.20–1.32 (m, 6H),
1.42–1.48 (m, 2H), 2.18 (t, J ¼ 8:5 Hz, 2H), 2.89 (dd, J ¼ 7:0,
1.5 Hz, 2H), 5.07–5.14 (m, 2H), 5.87 (ddt, J ¼ 17:0, 10.0, 7.0
Hz, 1H), 6.22 (s, 1H), 6.97–7.02 (m, 2H), 7.13–7.16 (m, 2H);
13C NMR (CDCl3) ꢀ 14.27, 22.80, 28.23, 29.55, 30.92, 31.80,
41.81, 115.05 (d, J ¼ 21:0 Hz), 116.56, 124.92, 130.24 (d, J ¼
7:6 Hz), 134.58 (d, J ¼ 3:4 Hz), 136.76, 142.19, 161.37 (d, J ¼
243:4 Hz); Found: C, 82.76; H, 9.42%. Calcd for C17H23F: C,
82.88; H, 9.41%.
3.18 (dt, J ¼ 6:5, 1.5 Hz, 2H), 5.13–5.16 (m, 1H), 5.18–5.22 (m,
1H), 5.84 (ddt, J ¼ 17:0, 10.0, 6.5 Hz, 1H), 7.14 (d, J ¼ 8:5 Hz,
2H), 7.28 (d, J ¼ 8:5 Hz, 2H); 13C NMR (CDCl3) ꢀ 14.01, 22.45,
28.26, 28.88, 31.36, 32.28, 45.38, 95.28, 116.65, 128.38, 129.90,
133.17, 134.09, 143.20, 146.29; HRMS (FAB) Found: 388.0459.
Calcd for C17H2235ClI: 388.0455 [Mþ].
(Z)-1-[3,5-Bis(trifluoromethyl)phenyl]-2-hexyl-1-iodo-1,4-
pentadiene (6b): IR (neat) 2930, 1376, 1278, 1178, 1140, 917,
1
684 cmꢃ1; H NMR (CDCl3) ꢀ 0.81 (t, J ¼ 7:5 Hz, 3H), 1.09 (m,
(E)-2-Hexyl-1-[4-(trifluoromethyl)phenyl]-1,4-pentadiene
4H), 1.18–1.21 (m, 2H), 1.34–1.37 (m, 2H), 1.99 (t, J ¼ 7:0 Hz,
2H), 3.22 (d, J ¼ 9:5 Hz, 2H), 5.18–5.26 (m, 2H), 5.85 (ddt, J ¼
17:0, 10.0, 7.0 Hz, 1H), 7.65 (s, 2H), 7.75 (s, 1H); 13C NMR
(CDCl3) ꢀ 14.08, 22.53, 28.45, 29.00, 31.47, 32.74, 45.53, 91.97,
117.47, 121.44, 123.26 (q, J ¼ 271:1 Hz), 129.07, 131.80 (q, J ¼
33:4 Hz), 133.69, 146.62, 148.90; HRMS (FAB) Found: 490.0593.
Calcd for C19H21F6I: 490.0592 [Mþ].
(2e): IR (neat) 2930, 1615, 1326, 1165, 1127, 1069, 1017 cmꢃ1
;
1H NMR (CDCl3) ꢀ 0.87 (t, J ¼ 7:0 Hz, 3H), 1.20–1.33 (m, 6H),
1.44–1.50 (m, 2H), 2.20 (t, J ¼ 8:0 Hz, 2H), 2.93 (dt, J ¼ 6:0,
1.0 Hz, 2H), 5.10–5.16 (m, 2H), 5.88 (ddt, J ¼ 17:0, 10.5, 6.0 Hz,
1H), 6.28 (s, 1H), 7.29 (d, J ¼ 8:0 Hz, 2H), 7.56 (d, J ¼ 8:0 Hz,
2H); 13C NMR (CDCl3) ꢀ 14.22, 22.81, 28.26, 29.54, 31.13,
31.81, 41.90, 116.89, 124.58 (q, J ¼ 270:0 Hz), 124.89, 125.14–
125.23 (m), 128.20 (q, J ¼ 32:0 Hz), 128.99, 136.37, 142.32,
144.51; Found: C, 72.81; H, 7.68%. Calcd for C18H23F3: C, 72.95;
H, 7.82%.
(E)-4-[3,5-Bis(trifluoromethyl)phenyl]-5-hexyl-1,4,7-octa-
triene (7): IR (neat) 2960, 2930, 2860, 1383, 1278, 1177, 1138,
992, 916, 897, 847, 711, 683, 684 cmꢃ1; 1H NMR (CDCl3) ꢀ 0.82
(t, J ¼ 7:0 Hz, 3H), 1.09–1.14 (m, 4H), 1.18–1.22 (m, 2H), 1.30–
1.36 (m, 2H), 1.82 (t, J ¼ 8:0 Hz, 2H), 2.99 (dt, J ¼ 6:0, 1.5 Hz,
2H), 3.11 (d, J ¼ 6:0 Hz, 2H), 4.93–5.01 (m, 2H), 5.09–5.16 (m,
2H), 5.69 (ddt, J ¼ 17:0, 10.0, 6.0 Hz, 1H), 5.85 (ddt, J ¼ 17:5,
10.0, 6.0 Hz, 1H), 7.55 (s, 2H), 7.75 (s, 1H); 13C NMR (CDCl3)
ꢀ 14.08, 22.63, 28.74, 29.36, 31.66, 33.30, 35.78, 38.79, 116.04,
116.44, 120.25–120.43 (m), 123.68 (q, J ¼ 271:1 Hz), 126.94,
129.35–129.37 (m), 131.44 (q, J ¼ 32:9 Hz), 135.00, 135.92,
138.33, 145.70; Found: C, 65.10; H, 6.52%. Calcd for C22H26F6:
C, 65.34; H, 6.48%.
(E)-1-[3,5-Bis(trifluoromethyl)phenyl]-2-hexyl-1,4-pentadi-
ene (2f): IR (neat) 2932, 2861, 1387, 1368, 1279, 1177, 1138,
918, 897, 708, 683 cmꢃ1; 1H NMR (CDCl3) ꢀ 0.88 (t, J ¼ 7:0 Hz,
3H), 1.23–1.33 (m, 6H), 1.48–1.54 (m, 2H), 2.19 (t, J ¼ 8:0 Hz,
2H), 2.96 (dd, J ¼ 7:5, 1.5 Hz, 2H), 5.14–5.18 (m, 2H), 5.84–
5.92 (m, 1H), 6.31 (s, 1H), 7.64 (s, 2H), 7.71 (s, 1H); 13C NMR
(CDCl3) ꢀ 13.96, 22.53, 28.06, 29.20, 31.02, 31.49, 41.59, 117.19,
119.65 (m), 123.14, 123.42 (q, J ¼ 271:6 Hz), 128.54 (m), 131.29
(q, J ¼ 33:0 Hz), 135.62, 140.30, 146.17; Found: C, 62.90; H,
6.11%. Calcd for C19H22F6: C, 62.63; H, 6.09%.
(E)-4-Pentyl-1,4-decadiene (2h): IR (neat) 2958, 2927, 2858,
1467, 994, 910 cmꢃ1
This work was supported by Grants-in-Aid for Scientific
Research, Young Scientists, and COE Research from the Min-
istry of Education, Culture, Sports, Science and Technology,
Japan. We thank Mr. Eiji Morita for the preparation of some
of the starting materials.
;
1H NMR (CDCl3) ꢀ 0.82 (t, J ¼ 7:5 Hz,
6H), 1.16–1.31 (m, 12H), 1.49–1.94 (m, 4H), 2.65 (d, J ¼ 7:0 Hz,
2H), 4.91–4.97 (m, 2H), 5.07 (t, J ¼ 7:0 Hz, 1H), 5.72 (ddt, J ¼
17:0, 10.0, 7.0 Hz, 1H); 13C NMR (CDCl3) ꢀ 14.07, 14.09, 22.59,
22.60, 27.77, 27.95, 29.74, 30.00, 31.62, 31.90, 41.52, 115.34,
126.14, 137.57, 137.70; HRMS(EI) Found: 208.2194. Calcd for
C15H28: 208.2192 [Mþ].
References
(E)-1-Deuterio-2-hexyl-1-phenyl-1,4-pentadiene (2a-d): IR
(neat) 2956, 2926, 2857, 1494, 1467, 1443, 995, 913, 754, 698
1
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cmꢃ1
;
1H NMR (CDCl3) ꢀ 0.87 (t, J ¼ 7:0 Hz, 3H), 1.22–1.32
(m, 6H), 1.46–1.50 (m, 2H), 2.22 (t, J ¼ 9:0 Hz, 2H), 2.91 (d, J ¼
7:0 Hz, 2H), 5.08–5.14 (m, 2H), 5.89 (ddt, J ¼ 17:0, 10.0, 7.0 Hz,
1H), 7.17–7.22 (m, 3H), 7.29–7.32 (m, 2H); 13C NMR (CDCl3)
ꢀ 14.07, 22.60, 28.09, 29.38, 30.82, 31.63, 41.71, 116.24, 125.48
(t, J ¼ 22:9 Hz), 125.94, 128.03, 128.56, 136.70, 138.33, 141.85;
2H NMR (CHCl3) ꢀ 6.32 (br). Found: C, 89.21; H and D, 10.73%.
Calcd for C17H23D: C, 89.02; H and D, 10.99%.
(E)-1-[3,5-Bis(trifluoromethyl)phenyl]-2-hexyl-4-methyl-1,4-
pentadiene (5): IR (neat) 2960, 2932, 1387, 1365, 1279, 1174,
1138, 896, 705, 683 cmꢃ1
;
1H NMR (CDCl3) ꢀ 0.87 (t, J ¼ 7:5
a) E. Negishi, J. A. Miller, J. Am. Chem. Soc. 1983, 105,
Hz, 3H), 1.22–1.32 (m, 6H), 1.46–1.55 (m, 2H), 1.74 (s, 3H), 2.15
(t, J ¼ 8:0 Hz, 2H), 2.91 (s, 2H), 4.82 (s, 1H), 4.90 (s, 1H), 6.33 (s,
1H), 7.64 (s, 2H), 7.70 (s, 1H); 13C NMR (CDCl3) ꢀ 14.15, 22.18,
22.73, 28.31, 29.45, 30.66, 31.68, 46.47, 113.49, 119.83–119.89
(m), 123.64 (q, J ¼ 271:5 Hz), 124.14, 128.70, 131.53 (q, J ¼
33:0 Hz), 140.47, 143.17, 145.76; Found: C, 63.74; H, 6.47%.
Calcd for C20H24F6: C, 63.48; H, 6.39%.
a) H. Yasui, K. Mizutani, H. Yorimitsu, K. Oshima, Tetra-
1-(4-Chlorophenyl)-2-hexyl-1-iodo-1,4-pentadiene (6a): IR
(neat) 2955, 2926, 2857, 1486, 1091, 1016, 914, 815 cmꢃ1
;
1H NMR (CDCl3) ꢀ 0.83 (t, J ¼ 7:5 Hz, 3H), 1.09–1.13 (m, 4H),
4 A part of this work was communicated: T. Nishikawa, H.
Yorimitsu, K. Oshima, Synlett 2004, 1573.
1.18–1.23 (m, 2H), 1.29–1.34 (m, 2H), 2.02 (t, J ¼ 8:0 Hz, 2H),

1274 Bull. Chem. Soc. Jpn. Vol. 79, No. 8 (2006)
Cobalt-Catalyzed Allylzincations
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