Stereoselective hydrogenolysis of 1,1-dibromo-1-alkenes and stereospecific synthesis of conjugated (Z)-alkenyl compounds

Article abstract of DOI:10.1021/jo9812781

The Pd-catalyzed hydrogenolysis of 1,1-dibromoalkenes with Bu₃SnH occurs at room temperature stereoselectively to give (Z)-1-bromo-1-alkenes. We sought to determine the optimal reaction conditions and illustrate the scope of this method with 32 dibromoalkenes including alkenyl- and alkynyl- conjugated 1,1-dibromo-1-alkenes 7a-h and 2,2-disubstituted 1,1-dibromo-1- alkenes 9af. Triphenylphosphine was the best ligand for the Pd-catalyzed hydrogenolysis. A wide range of solvents can be used for this reaction excluding EtOH, AcOH, and CHCl₃. However, the reaction proceeds even in these solvents with the addition of a cosolvent or radical scavenger. The reaction of 1,1-diiodo-1-alkene (3) gave a mixture of (Z)-1-iodo-1-alkene (4), (Z)-1-tributylstannyl-1-alkene (5), and a terminal alkene 6, while that of 1,1-dichloroalkene did not occur. This selectivity can be explained by the stereoselective insertion of Pd(0) to a trans bromine-alkenyl carbon bond, successive transmetalation with Bu₃SnH, and reductive elimination. The Suzuki and Sonogashira couplings of the resulting (Z)-1-bromo-1-alkenes with alkenyl(dialkoxy)borane and terminal alkyne occurred to give conjugated polyenes and enynes stereospecifically. The Pd-catalyzed hydrogenolysis of 1,1-dibromo-1-alkene and successive cross-coupling can be carried out either in a stepwise manner or in one-pot under the same Pd catalysis. These two processes should be useful for the synthesis of geometrically pure polyene and enyne with a Z-alkenyl unit.

Full text of DOI:10.1021/jo9812781

J . Org. Chem. 1998, 63, 8965-8975
8965
Ster eoselective Hyd r ogen olysis of 1,1-Dibr om o-1-a lk en es a n d
Ster eosp ecific Syn th esis of Con ju ga ted (Z)-Alk en yl Com p ou n d s
J un’ichi Uenishi,*,† Reiko Kawahama, and Osamu Yonemitsu
Department of Chemistry, Okayama University of Science, Ridaicho, Okayama 700-0005, J apan
J iro Tsuji
Department of Chemical Technology, Kurashiki University of Science and the Arts,
Tsurajima-cho, Kurashiki 712-8505, J apan
Received J une 30, 1998
The Pd-catalyzed hydrogenolysis of 1,1-dibromoalkenes with Bu3SnH occurs at room temperature
stereoselectively to give (Z)-1-bromo-1-alkenes. We sought to determine the optimal reaction
conditions and illustrate the scope of this method with 32 dibromoalkenes including alkenyl- and
alkynyl-conjugated 1,1-dibromo-1-alkenes 7a -h and 2,2-disubstituted 1,1-dibromo-1-alkenes 9a -
f. Triphenylphosphine was the best ligand for the Pd-catalyzed hydrogenolysis. A wide range of
solvents can be used for this reaction excluding EtOH, AcOH, and CHCl3. However, the reaction
proceeds even in these solvents with the addition of a cosolvent or radical scavenger. The reaction
of 1,1-diiodo-1-alkene (3) gave a mixture of (Z)-1-iodo-1-alkene (4), (Z)-1-tributylstannyl-1-alkene
(5), and a terminal alkene 6, while that of 1,1-dichloroalkene did not occur. This selectivity can be
explained by the stereoselective insertion of Pd(0) to a trans bromine-alkenyl carbon bond,
successive transmetalation with Bu3SnH, and reductive elimination. The Suzuki and Sonogashira
couplings of the resulting (Z)-1-bromo-1-alkenes with alkenyl(dialkoxy)borane and terminal alkyne
occurred to give conjugated polyenes and enynes stereospecifically. The Pd-catalyzed hydrogenolysis
of 1,1-dibromo-1-alkene and successive cross-coupling can be carried out either in a stepwise manner
or in one-pot under the same Pd catalysis. These two processes should be useful for the synthesis
of geometrically pure polyene and enyne with a Z-alkenyl unit.
Dienes and polyenes have been the subject of great
interest due to their important roles in biologically active
compounds. Considerable progress has recently been
made in the regio- and stereocontrol of their synthesis.1
A Z-alkenyl unit conjugated with an alkene or alkyne is
often seen in structures of natural products, such as
arachidonic acids,2 retinoids,3 antibiotics,4 and marine
natural products.5 To prepare this conjugated Z-double
bonds, several synthetic methods including the Wittig
and related reactions,6 semihydrogenation of alkyne,7 and
metal-catalyzed cross-coupling reactions8 have been re-
ported. To prepare geometrically pure polyenes and
enynes bearing a conjugated Z-alkenyl group, metal-
catalyzed, particularly Pd-catalyzed, cross-coupling reac-
tions have been proven to be reliable,9 since such
reactions occur with high stereospecificity and give the
resulting alkenes with retention of the configuration of
the starting alkenyl halides or alkenylmetals. In such
cases, geometrically pure (Z)-alkenyl halides or (Z)-
alkenylmetals are required. Several methods for syn-
thesizing (Z)-1-haloalkenes have been reported, e.g.,
Wittig-type condensations,10 cis hydrogenations of 1-ha-
loalkynes with diimine,11 and hydrometalation of alkynes
followed by replacement of the metal with halide.12 Since
these methods sometimes give unsatisfactory results, a
more efficient and reliable method for the synthesis of
(Z)-1-halo-1-alkenes is desirable, particularly in the case
of conjugated 1-halodienes, such as (1Z,3E)-1-halo-1,3-
dienes. In a preliminary paper, we reported a new
method for synthesizing (Z)-1-bromo-1-alkenes and con-
† Tel: 81-86-256-9419. Fax: 81-86-256-9419. E-mail juenishi@
high.ous.ac.jp.
(1) The Chemistry of Dienes and Polyenes; Rappoport, Z., Ed.; J ohn
Wiley & Sons: New York, 1997.
(2) (a) Nicolaou, K. C.; Ramphal, J . Y.; Petasis, N. A.; Serhan, C. N.
Angew. Chem., Int. Ed. Engl. 1991, 30, 1100. (b) Rawlings, B. J . Nat.
Prod. Rep. 1997, 14, 335.
(3) (a) Yoshizawa, T.; Kuwata, O. In CRC Handbook of Organic
Photochemistry and Photobiology; Horspool, W. M., Song, P.-S., Eds.;
CRC Press: Boca Raton, FL, 1995; p 1493. (b) Balogh-Nair, V.;
Nakanishi, K. In Method in Enzymology; Packer, L., Ed.; Academic
Press: New York, 1982; Vol 88.
(8) Metal-Catalyzed Cross-coupling Reactions; Diederich, F., Stang,
P. J ., Eds.; Wiley-VCH: Weinheim, 1998.
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Tetrahedron 1996, 52, 6453. (c) Wang, K. K. Chem. Rev. 1996, 96, 207.
(d) Maier, M. E. Synlett. 1995, 13.
(5) Faulkner, D. J . Nat. Prod. Rep. 1998, 15, 113 and the same series
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B. M., Fleming, I., Eds.; Pergamon Press: New York, 1991; Vol. 3, p
481. (b) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457. (c) Stille,
J . K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508. (d) Sonogashira, K.
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Pergamon Press: New York, 1991; Vol. 3, p 521.
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Pergamon Press: New York, 1995; Vol. 1, p 719.
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Fleming, I., Eds.; Pergamon Press: New York, 1991; Vol. 8, p 417. (b)
Hudlicky, M. Reduction in Organic Chemistry; J ohn Wiley & Sons:
New York, 1984. (c) Rylander, P. N. Hydrogenation Methods; Academic
Press: Orlando, 1985.
(10) (a) Vedejs, E.; Peterson, M. J . Top. Stereochem. 1994, 21, 1. (b)
Chen. J .; Tao, W.; Zhao, K. Tetrahedron Lett. 1994, 35, 2827. (c) Zhang,
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10.1021/jo9812781 CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/11/1998

8966 J . Org. Chem., Vol. 63, No. 24, 1998
Uenishi et al.
Ta ble 1. Ster eoselective Hyd r ogen olysis of
Sch em e 1
1,1-Dibr om o-1-a lk en es 1a -r
Sch em e 2
jugated polyenes and enediynes with the Z-alkenyl unit,13
in which the Pd-catalyzed hydrogenolysis of 1,1-dibromo-
1-alkene with Bu3SnH gave (Z)-1-bromo-1-alkene stereo-
selectively, which coupled with alkenylboronic acid or
alkyne under Pd-catalyzed conditions. In this paper, we
describe the details of the hydrogenolysis of 1,1-dibromo-
1-alkenes, including its mechanism, scope, and limita-
tions and also its usefulness for the preparation of
conjugated polyenes and enediynes by the Pd-catalyzed
cross-coupling (Scheme 1).
Resu lts a n d Discu ssion
Ster eoselective Hyd r ogen olysis. Two examples of
the hydrogenolysis of 1,1-dibromo-1-alkene have been
reported in the literature.14 The reaction of dibromoal-
kene with diethyl phosphite in the presence of triethyl-
amine gave a mixture of E- and Z-isomers,14a and the
radical reaction with Bu3SnH initiated by a catalytic
amount of triethylborane also gave a mixture.14b How-
ever, in the preliminary paper, we have revealed the
stereoselective hydrogenolysis of 1,1-dibromo-1-alkene
with Bu3SnH catalyzed by Pd(PPh3)4 to give (Z)-1-
bromoalkene exclusively.13 For example, â,â-dibromo-4-
methylstyrene (1a , Scheme 2, R ) p-tolyl, and entry 1
in Table 1) was selectively reduced with 1.2 equiv of Bu3-
SnH in the presence of 4 mol % of Pd(PPh3)4 in benzene
a
b
Isolated yield. Pd(PPh3)4 was used as a catalyst. c Pd(0)
catalyst was generated in situ from Pd(OAc)2 and PPh3.
at room temperature to give (Z)-â-bromo-4-methylstyrene
(2a )15 in 79% yield. The proton NMR spectrum indicated
a coupling constant of 8.1 Hz due to the cis olefin of the
styryl protons, and none of the corresponding E-isomer
was detected in a NMR spectrum of the crude reaction
mixtures. Aliphatic dibromoalkene, e.g., 1,1-dibromo-4-
phenylbutene (1m ) (Scheme 2, R ) phenethyl, and entry
13 in Table 1), was also hydrogenolyzed under the same
conditions to provide (Z)-1-bromo-4-phenyl-1-butene (2m )16
(13) (a) Uenishi, J .; Kawahama, R.; Yonemitsu, O.; Tsuji, J . J . Org.
Chem. 1996, 61, 5716. (b) Uenishi, J .; Kawahama, R.; Shiga, T.;
Yonemitsu, O.; Tsuji, J . Tetrahedron Lett. 1996, 37, 6759.
(14) (a) Hirao, T.; Masunaga, T.; Ohshiro, Y.; Agawa, T. J . Org.
Chem. 1981, 46, 3745. (b) Miura, K.; Ichinose, Y.; Nozaki, K.; Fugami,
K.; Oshima, K.; Utimoto, K. Bull. Chem. Soc. J pn. 1989, 62, 143.
(15) Paquette, L. A.; Fristad, W. E.; Dime, D. S.; Bailey, T. R. J .
Org. Chem. 1980, 45, 3017.
(16) Pinhey, J . T.; Stoermer, M. J . J . Chem. Soc., Perkin Trans. 1
1991, 2455.

Hydrogenolysis of 1,1-Dibromo-1-alkenes
J . Org. Chem., Vol. 63, No. 24, 1998 8967
Ta ble 2. P d Ca ta lysts for th e Hyd r ogen olysis of 1a
Sch em e 3
in 79% yield. These results indicated that this reaction
can be used for the synthesis of both aromatic and
aliphatic (Z)-1-bromo-1-alkenes. The results for 18 di-
bromoalkenes are shown in Table 1. The starting dibro-
moalkenes were easily prepared from the corresponding
aldehydes with carbon tetrabromide and triphenylphos-
phine by the standard procedure.17
a
b
Pd catalyst (4 mol %) was used in toluene. Isolated yields.
c Stirred for 15 min before use. Stirred for 2 h before use.
d
lation of this σ-palladium complex with Bu3SnH to
generate alkenylpalladium hydride, and (iii) reductive
elimination to give (Z)-1-bromo-1-alkene and regenera-
tion of Pd(0) species. Eventually, this catalytic process
afforded the desired (Z)-1-bromo-1-alkene and consumed
Bu3SnH. The high selectivity of the hydrogenolysis may
be due to the oxidative addition as a key step, where
Pd(0) is inserted into the sterically less hindered carbon-
bromine bond. When an excess of Bu3SnH was used,
over-hydrogenolysis occurred to give a terminal alkene.
The rate of the oxidative addition of 1,1-dibromo-1-
alkenes to Pd(0) was estimated to be 5-20 times faster
than that of (Z)-1-bromo-1-alkenes. Usually, 1.1-1.2
equiv of Bu3SnH is required for the reaction, since a
slight excess of Bu3SnH is consumed in the formation of
(Bu3Sn)2 as discussed later.
P d Ca ta lyst a n d Liga n d . Initially, we used Pd-
(PPh3)4 as the catalyst, and it was a proper choice for
this reaction. Table 2 lists several Pd catalysts and the
results of the respective reactions. The reaction of 1a
with PdCl2(PPh3)2 gave 2a in 34% yield along with 50%
recovery of 1a . Surprisingly no hydrogenolysis of 1a took
place in the presence of PdCl2(CH3CN)2, PdCl2(dba)3‚
CHCl3, or bidentate catalysts PdCl2(dppf), even when an
excess of Bu3SnH was added. In these reactions, (Bu3Sn)2
was formed. Pd(0) has been reported to catalyze the
dimerization of Bu3SnH to generate hydrogen and (Bu3-
Sn)2.19 Thus, in these particular cases, Pd catalyzed the
dimerization of Bu3SnH, which competed with the oxida-
tive addition of alkenyl bromide to Pd(0), although the
dimerization proceeded much slower with Ph3P ligand.
Interestingly, both of these pathways depend on the
nature of the Pd catalyst. However, when Ph3P was
added to the reaction mixture using the above catalysts,
PdCl2(PPh3)2, PdCl2(CH3CN)2, or PdCl2(dba)3‚CHCl3, hy-
drogenolysis proceeded to give 2a in good yields with
excellent selectivity (entries 6, 7, and 8). With the
addition of Ph3P, Pd(0) may have characteristics similar
to those of Pd(PPh3)4. Due to their poor solubility in
â,â-Dibromostyrenes including naphthyl derivatives
1a -h were converted to the corresponding (Z)-â-bro-
mostyrenes 2a -h in excellent yields with exclusive
stereoselectivity (entries 1-8). Even in the presence of
acetoxy, hydroxyl, and dimethylamino groups in the
molecules, the reaction proceeded quite well (entries 4,
5, and 6). Although pyridyl-substituted dibromo- and
bromoethylenes were rather unstable, hydrogenolysis of
(dibromovinyl)pyridines gave the corresponding (Z)-bro-
movinylpyridines in 43-64% yields (entries 9, 10, and
11). In contrast, (Z)-(bromovinyl)quinoline 2l was much
more stable than pyridyl derivatives and obtained in 65%
yield. The reaction of 2-alkyl-, branched alkyl-, and
silyloxyalkyl-substituted 1,1-dibromoethylenes, 1m , 1n ,
1o, 1p , 1q, and 1r , gave the corresponding (Z)-1-bromo-
1-alkenes in good yields. The reactions of dibromoal-
kenes 1q and 1r , which have silyl ether and ester
moieties, occurred to give 2q and 2r in 56 and 80% yields,
respectively (entries 17 and 18). All of these results
indicate that this hydrogenolysis takes place in a general
and stereoselective manner to give Z-bromoalkenes.
Rea ction Mech a n ism s. When Bu3SnD was used as
a deuterium source instead of Bu3SnH for the reactions
of 1a and 1m , deuterium was introduced at the trans
position of the product. Since stereoselective hydro-
genolysis did not proceed in the absence of Pd catalyst,
palladium is essential for stereocontrol. On the other
hand, under radical conditions initiated with Et3B, a 1:1
mixture of E- and Z-isomers was obtained from 1a and
1m , respectively.
The reaction and its selectivity can be explained in
terms of the typical mechanism of Pd-catalyzed reac-
tions,18 as shown in Scheme 3; thus, (i) highly stereose-
lective oxidative addition of the carbon-bromine bond
located at the trans position of 1,1-dibromo-1-alkene to
Pd(0) forming alkenylpalladium bromide, (ii) transmeta-
(17) Ramirez, F.; Desai, N. B.; McKelvie, N. J . Am. Chem. Soc. 1962,
84, 1745.
(18) Tsuji, J . Palladium Reagents and Catalysts; J ohn Wiley & Sons
Ltd.: Chichester, 1995.
(19) Four, P.; Guibe, F. J . Org. Chem. 1981, 46, 4439.

8968 J . Org. Chem., Vol. 63, No. 24, 1998
Uenishi et al.
Ta ble 3. Liga n d s for P d Ca ta lysts a n d th e
Hyd r ogen olysis of 1a
Sch em e 4
Ta ble 4. Solven t Effect for th e Hyd r ogen olysis of 1a
a
Catalysts were generated for 4 mol % of Pd(OAc)2 and 16 mol
% of PPh3 by stirring in toluene for 15 min at room temperature.
b
Isolated yields. c Determined by 1H NMR.
toluene, the reaction with PdCl2 and Pd(OAc)2 gave
disappointing results (entries 9 and 10), which were also
improved dramatically by the addition of Ph3P (entries
11 and 12). When Pd(OAc)2 and PdCl2 were premixed
with 4 equiv of Ph3P at room temperature in benzene
for 15 and 120 min, respectively, the hydrogenolysis
occurred quite smoothly and stereoselectively. This in
situ preparation of the active Pd catalyst is convenient,
practical, and less expensive than the use of Pd(PPh3)4.
In particular, Pd(OAc)2 gave better results than PdCl2
due to its better solubility and to the shorter time needed
to generate the active catalyst.
a
b
Isolated yields. Determined by 1H NMR. c Recovery of the
starting material.
Next, we examined 14 phosphine and arsine ligands.
The results are summarized in Table 3. The Pd catalysts
were generated by stirring Pd(OAc)2 (4 mol %) and the
phosphines (16 mol %) in benzene for 15 min at room
temperature. The hydrogenolysis of 1a with arylphos-
phines except o-tolylphosphine (entry 4) gave 2a in very
good yields with excellent selectivity (entries 1, 2, and
3). When an electron-withdrawing group was introduced
to phosphines, e.g., as shown in entry 5, the reaction of
diphenyl(pentafluorophenyl)phosphine gave 2a in 23%
yield and 74% recovery of 1a . The use of tri(pentafluo-
rophenyl)phosphine gave no desired product (entry 6).
In these cases, Bu3SnH was consumed to give (Bu3Sn)2
instead of 2a (Scheme 4). The above results show that
sterically hindered or electron-deficient arylphosphines
are not appropriate for the hydrogenolysis catalyst. An
electron-donating phosphine may appear to be preferable.
However, when diphenyl(isopropyl or propyl)phosphines,
in which one of the phenyl groups of triphenylphosphine
was replaced with an isopropyl or propyl group, were
used, the yields and selectivities declined along with the
recovery of 1a (entries 7 and 8). Importantly, the
formation of E-isomers were observed considerably with
the use of these alkyl(aryl)phosphines. Other arylalkyl-
phosphines and trialkylphosphines gave similar results
(entries 9, 10, 11, and 12). Alkylphosphine may be a good
ligand for the formation of (Bu3Sn)2 and radical hydro-
genolysis with Bu3SnH. In fact, when some BHT (butyla-
ted hydroxytoluene; 2,6-di-tert-butyl-p-cresol) was added
in these reactions, the formation of E-isomer was com-
pletely inhibited, but nevertheless the yield did not
improve much. Tribenzylphoshine and triphenylarsine
were totally ineffective as ligands for hydrogenolysis
(entries 13 and 14).
Solven ts. We examined several common solvents in
this reaction. The results are listed in Table 4. A wide
range of solvents are available for the hydrogenolysis.
Benzene, toluene, ether, DME, THF, dioxane, and ethyl
acetate could be used and gave Z-alkene exclusively
(entries 1-7). Halogen-containing solvents generally
cannot be used for the reaction of Bu3SnH. In fact, the
reaction in CHCl3 did not give any 2a , because Bu3SnH
reacted with CHCl3 and was consumed very quickly
(entry 8). However, the radical reaction with CH2Cl2 was
slower than that with CHCl3 and gave the desired
hydrogenolysis (entry 9). The hydrogenolysis also oc-
curred under wet conditions. Since wet solvents, e.g., wet
CH2Cl2 (entry 10), gave yields similar to those under
anhydrous conditions, the presence of a small amount of
water did not influence the hydrogenolysis. The reaction
of 1a in ethanol and acetic acid took longer and gave 2a
in poor yields with unsatisfactory selectivities (entries
11 and 12). In these reactions, radical hydrogenolysis
might compete with Pd-catalyzed hydrogenolysis due to
the poor solubility of Pd(PPh3)4 in these solvents. This

Hydrogenolysis of 1,1-Dibromo-1-alkenes
J . Org. Chem., Vol. 63, No. 24, 1998 8969
Sch em e 5
Sch em e 6
problem was nicely solved by the addition of toluene to
the reaction mixture as a cosolvent (entries 13 and 14).
Furthermore, this radical hydrogenolysis was also com-
pletely inhibited by the addition of BHT. This radical
scavenger is effective when radical hydrogenolysis occurs.
Under these conditions, even CHCl3 can be used as a
solvent.
Hyd r id e Sou r ces. Since Bu3SnH is toxic, it is desir-
able to find other hydride sources. Despite our efforts
to examine other reducing reagents, such as a combina-
tion of HCOOH and triethylamine, silyl hydrides includ-
ing Et3SiH and (Me3Si)3SiH, and boranes including
catecholborane, 9-BBN, and BH3 complexes, they were
totally inactive for this hydrogenolysis. Only some metal
borohydrides gave the desired (Z)-1-bromo-1-alkene.
LiBEt3H was the best among them and gave (Z)-1-bromo-
1-alkenes in yields of 50-65%, but was less satisfactory
than Bu3SnH. NaBH4, Na(CN)BH3, and other sodium
alkoxyborohydrides were less reactive than Superhy-
dride. Although less-toxic Ph3SnH also gave the desired
Z-bromoalkene exclusively, the reaction rate was slower
than that with Bu3SnH. At this stage, Bu3SnH was
found to be the best hydride reagent and delivered its
hydrogen on Sn to Pd very smoothly. If this transmeta-
lation works for other Sn-X bonds to a Pd center and
the subsequent reductive elimination goes well, a new X
group would be introduced to an sp2 alkenyl carbon center
steroselectively instead of trans bromide, as shown in
Scheme 5. Although Bu3SnCN, (Bu3Sn)2, and Bu3Sn-
(allyl) were tested as other Bu3Sn-X species, substitution
did not take place.
Rea ctivity a n d Selectivity. The Pd-catalyzed trans-
formation of alkenyl halides to alkene has been reported
by Oshima et al.,20 in which hydrogenolysis proceeded
in the presence of Bu3SnH. Alkenyl iodide was suitable
as the substrate, while alkenyl bromide was not. No
reaction occurred with alkenyl chloride. The hydro-
genolysis of alkenyl bromide required slow addition of
Bu3SnH at a higher temperature and resulted in a poor
yield. The hydrogenolysis of 1,1-dibromoalkenes took
place much more mildly at room temperature, as we have
described above. The reaction of 1,1-dichloro-3-phenyl-
1-butene did not occur under the same reaction condi-
tions, even in refluxing benzene using the slow addition
of Bu3SnH. On the other hand, 1,1-diiodo-3-phenyl-1-
butene (3) reacted with Bu3SnH (1.2 equiv) in the
presence of Pd catalyst at room temperature. However,
this reaction gave a mixture of (Z)-1-iodo-1-butene (4) in
27% yield, (Z)-1-tributylstannyl-1-butene (5)16 in 11%
yield, 4-phenyl-1-butene (6) in 3% yield, and 27% recovery
of 3 (Scheme 6). The total yields improved slightly when
the reaction was carried out at 0 °C in toluene. The
formation of 5 was unexpected. This formation was
considered to be due to the reaction of 4 with (Bu3Sn)2
or Bu3SnI, but the yield of 5 did not increase when they
were added to the reaction mixtures. The iodoalkene 4
was obtained in 62% yield when the crude reaction
extract was treated with iodine in CHCl3 solution.
Nonetheless, the hydrogenolysis of 1,1-diiodo-1-alkene
was disappointing, and the mechanism of the formation
of (Z)-1-tributylstannyl-1-butene was not clear.
H yd r ogen olysis of Con ju ga t ed 1,1-Dib r om oa l-
k en es a n d 2,2-Disu bstitu ted 1,1-Dibr om oa lk en es.
Although (Z)-1-bromo-1-alkenes are certainly useful for
E,Z-diene synthesis as a geometrically pure building
block, 2-alkenyl- or 2-alkynyl-substituted (Z)-1-bromo-1-
alkenes would be much more valuable for the synthesis
of conjugated polyenes or enynes. The results of hydro-
genolysis of 1,1-dibromopolyenes and 1,1-dibromoenynes
are listed in Table 5. The reaction of (E)-1,1-dibromo-6-
phenyl-1,3-hexadiene (7a ) gave (1Z,3E)-1-bromo-6-phen-
yl-1,3-hexadine (8a ) in an 82% yield (entry 1). (3E,5E)-
1,1-Dibromo-1,3,5-triene 7b gave (1Z,3E,5E)-1-bromo-
1,3,5-triene 8b in 74% yield (entry 2). No other stereo-
isomers were formed in these reactions. The reactivity
of conjugated dibromoalkenes seemed to be greater than
that of simple 1,1-dibromo-1-alkenes. Therefore, to sup-
press over-hydrogenolysis, a slight excess of Bu3SnH
(1.02-1.05 equiv) should be used relative to the sub-
strates. Four additional dienes in entries 3-6, including
geometrical isomers, gave the corresponding 1-bromo-1,3-
dienes stereoselectively. Enynes 8g and 8h were ob-
tained in 63 and 69% yields from dibromoenynes 7g and
7h , respectively.
Next, we were interested in the hydrogenolysis of 2,2-
disubstituted 1,1-dibromoalkenes, which would give trisub-
stituted bromoolefines. The results for six dibromoal-
kenes are shown in Table 6. Due to steric hindrance of
the vicinal carbon-carbon bonds, the fully substituted
1,1-dibromoolefin was anticipated to show poor reactivity.
In fact, the yields of these reactions were unsatisfactory
except for that with 9a , from which 10a was obtained in
82% yield (entry 1). In this case, the carbon-bromine
bond was located gauche between the axial and equato-
rial carbon-hydrogen bonds. However, in other cases,
the reactions were influenced by large steric effect of the
substituent. The reaction of dialkyl-substituted com-
(20) Taniguchi, M.; Takeyama, Y.; Fugami, K.; Oshima, K.; Utimoto,
K. Bull. Chem. Soc. J pn. 1991, 64, 2593.

8970 J . Org. Chem., Vol. 63, No. 24, 1998
Uenishi et al.
Ta ble 5. Ster eoselective Hyd r ogen olysis of Con ju ga ted
Sch em e 7
1,1-Dibr om o-1-a lk en es 7a -h
NOE studies by NMR. The bulkiness of the phenyl group
might affect the reaction to give a selective ratio of 30:1
(Z:E). On the other hand, the coordinating effect of the
pyridine nitrogen atom contributed to the insertion of Pd,
resulting in the preferred formation of the E-isomer of
10f in a 2:1 ratio.
a
b
Isolated yield. Pb(PPh3)4 (4 mol %) was used as catalyst.
P d -Ca ta lyzed Cr oss-Cou p lin g Rea ction . Although
substitution of the Pd-bromine bond by Bu3SnCN or
Bu3Sn(allyl) failed for 1,1-dibromo-1-alkene, that of al-
kenylboronic acid has been reported by Roush et al.21 This
Suzuki reaction9b of 1,1-dibromo-1,3-diene also occurred
well under the TlOH-mediated conditions.22 Thus, a
mixture of 7a with (E)-isopentenylboronic acid (1.2 equiv)
in the presence of a catalytic amount of Pd(PPh3)4 and
aqueous TlOH gave bromotriene 11 in 74% yield as a
single stereoisomer (Scheme 7). On the other hand,
reaction of 7a with phenylacetylene (1.2 equiv) under
Sonogashira conditions23 gave a mixture of monoalkynyl-
and dialkynyldienes 12 and 13 in 36 and 33% yields,
along with 17% recovery of 7a . These results indicate
that the chemo- and stereoselectivites of 1,1-dibromo-1,3-
dienes are high in Suzuki coupling, but rather low in
Sonogashira coupling.
Ta ble 6. Hyd r ogen olysis of F u lly Su bstitu ted
1,1-Dibr om o-1-a lk en es 9a -f
Although the Suzuki reaction of 7a proceeded at room
temperature, the reaction of 8a with the same boronic
acid did not occur under the same conditions. On the
other hand, when the reaction was conducted in refluxing
benzene in the presence of sodium ethoxide under typical
Suzuki conditions,24 (E,Z,E)-triene 14 was formed exclu-
sively in 85% yield. If the bromotriene 11 can be
debrominated with Bu3SnH stereospecifically, (E,E,E)-
triene, which is an isomer of 14, would be produced.
Unfortunately, the hydrogenolysis of 11 was unsuccessful
due to the poor reactivity of the sterically hindered
carbon-bromine bond. Sonogashira coupling of 8a with
trimethylsilylacetylene took place very nicely to give
alkynyl E,Z-diene 15 in 93% yield stereospecifically.
However the Heck reaction of 8a with methyl acrylate
a
b
Isolated yield. Determined by 1H NMR. c Pd(PPh3)4 (4 mol
d
%) was used as catalyst. The structure of the predominant isomer
was indicated.
pound 9b did not occur (entry 2). Dibromodienes 9c and
9d gave bromodienes 10c and 10d in 40 and 58% yields
respectively, in which a carbon-bromine bond beside an
sp2 carbon of a cyclohexene ring is more favorably
hydrogenated than that beside an sp3 carbon (entries 3
and 4). In the case of 9e, the Z-isomer of 10e was
predominantly formed in 31% yield. The stereochemical
assignments of these alkenes were performed by careful
(21) (a) Roush, W. R.; Brown, B. B.; Drozda, S. E. Tetrahedron Lett.
1988, 29, 3541. (b) Roush, W. R.; Moriarty, K. J .; Brown, B. B.
Tetrahedron Lett. 1990, 31, 6509.
(22) Uenishi, J .; Beau, J .-M.; Armstrong, R. W.; Kishi, Y. J . Am.
Chem. Soc. 1987, 109, 4756.
(23) Sonogashira, K.; Tohda, Y. Hagihara,. N. Tetrahedron Lett.
1975, 4467.
(24) The typical Suzuki conditions: Organic Syntheses; Wiley: New
York, 1993; Collect. Vol. 8, 532.

Hydrogenolysis of 1,1-Dibromo-1-alkenes
J . Org. Chem., Vol. 63, No. 24, 1998 8971
Sch em e 8
polyenes containing a Z-alkenyl unit have been found in
natural products. Since they are mostly unstable, mild
and stereospecific conditions are essential for their
synthesis. With regard to the current method, we have
already demonstrated the potency of the combination of
selective hydrogenolysis and a mild Pd-catalyzed coupling
reaction for the synthesis of unstable polyene natural
products, e.g., (11Z)-retinal26 and (2Z,4E,6E)-dehydro-
dendrolasin.27
Exp er im en ta l Section
Gen er a l P r oced u r es. All air- or moisture-sensitive reac-
tions were carried out in flame-dried glassware under Ar
atmosphere. Solvents were distilled freshly over sodium/
benzophenone ketyl for THF, ether, and benzene, over P2O5
for CH2Cl2 and CHCl3, over CaH2 for hexane, toluene, DME,
dioxane, and EtOH under a nitrogen atmosphere. Thin-layer
chromatography (TLC) was performed with Merck 60F254
precoated silica gel plates. Column chromatography was
carried out using Wako neutral alumina (200 mesh) and Merck
silica gel 60 (70-230 mesh). Ph3P was added to the NMR
samples for stabilization of unstable 1-bromo-1-alkenes.
Typ ica l P r oced u r e of Hyd r ogen olysis. (i) P d (P P h 3)4-
Ca ta lyzed Rea ction . To a stirred solution of dibromoalkene
(1 mmol) in dry benzene or toluene (10 mL) were added Pd-
(PPh3)4 (4 mol %) and Bu3SnH (1.0-1.2 mmol) successively,
and the mixture was stirred at room temperature for the time
indicated in the tables. After the reaction was completed, it
was diluted with hexane (30-50 mL) and washed with water
and brine. The hexane extract was dried over MgSO4, and
the solvent was removed under reduced pressure. The residue
was purified by column chromatography. If it was not speci-
fied, the column chromatography was performed with alumina
using hexane as an eluent.
Sch em e 9
exclusively gave all-E-trienecarboxylic acid ester, where
the product might isomerize after the coupling.25
The hydrogenolysis, Suzuki, and Sonogashira cross-
coupling reactions proceeded under Pd catalysts with a
retention of configuration. If Pd(0) species are still alive
in the final stage of the hydrogenolysis, and its single
byproduct Bu3SnBr does not disturb the successive cross-
coupling, one-pot reaction may be possible. If these
processes work well, polyenes and enynes could be
obtained directly from 1,1-dibromo-1-alkenes without the
isolation of unstable bromopolyenes or bromoenynes.
Therefore, a one-pot reaction would be quite beneficial.
As soon as the hydrogenolysis of 7a was completed, the
reaction mixture was subjected to a one-pot Suzuki
reaction. The triene 14 was obtained in 54% stereose-
lectively. In the same manner, the one-pot Sonogashira
reaction of 7a via 8a gave dienyne 15 in 61% yield
(Scheme 8).
The success of the one-pot Sonogashira coupling from
dibromoenyne allows the facile preparation of (Z)-3-
hexene-1,5-diynes from (Z)-1,1-dibromo-1-hexen-3-yne
with a Pd catalyst. Thus, after the hydrogenolysis of 7g,
product 8g was coupled with trimethylsilylacetylene to
give enediyne 16 in 70% yield. Coupling reactions with
silyloxyalkyl- and hydroxyalkyl-substituted alkynes gave
enediynes 17 and 18 in 64 and 54% yields, respectively
(Scheme 9).
(ii) In Situ Gen er a tion of P d (0) Sp ecies by a Com bin a -
tion of P d (OAc)2 a n d P h 3P . An anhydrous toluene (8 mL)
was added to a mixture of PPh3 (0.16 mmol) and Pd(OAc)2 (0.04
mmol) at room temperature under an Ar atmosphere, and the
mixture was stirred for 15 min to generate a light yellow
solution. Dibromoalkene (1 mmol) in toluene (2 mL) and Bu3-
SnH (1.0-1.2 mmol) were added to the mixture. The reaction
was continued for the time indicated in the tables, and the
workup and purification were performed by the same proce-
dure as described in the use of Pd(PPh3)4 catalyst.
(Z)-â-Br om o-4-m eth ylstyr en e (2a ):15 colorless syrup; Rf
) 0.55 (hexane); 1H NMR (400 MHz, CDCl3) δ 2.36 (3H, s),
6.36 (1H, d, J ) 8.1 Hz), 7.02 (1H, d, J ) 8.1 Hz), 7.17 (2H, d,
J ) 8.1 Hz), 7.58 (2H, d, J ) 8.1 Hz).
(Z)-â-Br om ostyr en e (2b):28 colorless oil; Rf ) 0.55 (hex-
1
ane); H NMR (400 MHz, CDCl3) δ 6.43 (1H, d, J ) 8.1 Hz),
7.07 (1H, d, J ) 8.1 Hz), 7.30-7.40 (3H, m), 7.66-7.69 (2H,
m).
(Z)-â-Br om o-2-m et h ylst yr en e (2c):29 colorless oil; Rf )
1
0.47 (hexane); H NMR (300 MHz, CDCl3) 2.28 (3H, s), 6.53
(1H, d, J ) 7.8 Hz), 7.15 (1H, d, J ) 7.8 Hz), 7.18-7.26 (3H,
m), 7.56 (1H, m).
(Z)-4-Acetoxy-â-br om ostyr en e (2d ): purified by silica gel
column chromatography eluted with 10% EtOAc in hexane;
colorless crystals; mp 46-47 °C (hexane); Rf ) 0.53 (20%
In conclusion, we have reported a mild and highly
stereoselective hydrogenolysis of 1,1-dibromo-1-alkenes.
This reaction is potentially useful for the general prepa-
ration of (Z)-1-bromo-1-alkenes. Since (Z)-1-bromo-1-
alkenes including conjugated alkenes were obtained in
geometrically pure form, they could be used as a good
building block for Z-alkene synthesis. Pd-catalyzed cross-
coupling reactions of the (Z)-1-bromo-1-alkenes provided
polyenes or enynes bearing a Z-alkenyl unit in good to
excellent yields stereospecifically. Several conjugated
1
EtOAc in hexane); H NMR (300 MHz, CDCl3) δ 2.32 (3H, s),
6.44 (1H, d, J ) 8.1 Hz), 7.05 (1H, d, J ) 8.1 Hz), 7.10 (2H, dt,
J ) 8.7, 2.0 Hz), 7.72 (2H, dt, J ) 8.7, 2.0 Hz); 13C NMR (100
MHz, CDCl3) δ 21.1, 106.5, 121.4, 130.1, 131.4, 132.5, 150.3,
169.3; MS (EI) m/z (rel intensity) 242, 240 (M+, 15, 15), 200
(base), 198 (99), 119 (9), 78 (71). Anal. Calcd for C10H9O2Br:
C, 49.82; H, 3.76. Found: C, 49.86; H, 3.56.
(26) Uenishi, J .; Kawahama, R.; Yonemitsu, O.; Wada, A.; Ito, M.
Angew. Chem., Int. Ed. Engl. 1998, 37, 320.
(27) Uenishi, J .; Kawahama, R.; Tanio, A.; Wakabayashi, S.; Yone-
mitsu, O Tetrahedron 1997, 53, 2439.
(25) The chemical yield was less than 20% under J effery’s improved
conditions. See: J effery, T. Tetrahedron Lett. 1985, 26, 2667.
(28) Miller, R. B.; McGarvey, G. J . Org. Chem. 1978, 43, 4424.
(29) Galamb, V.; Alper, H. Tetrahedron Lett. 1983, 24, 2965.

8972 J . Org. Chem., Vol. 63, No. 24, 1998
Uenishi et al.
(Z)-â-Br om o-4-h yd r oxystyr en e (2e): purified by silica gel
column chromatography eluted with 10% EtOAc in hexane;
colorless crystals; mp 71-72 °C (hexane); Rf ) 0.42 (20%
(Z)-1-Br om o-3-cycloh exyleth ylen e (2o):28 colorless oil; Rf
) 0.80 (hexane); 1H NMR (300 MHz, CDCl3) δ 1.05-1.40 (5H,
m), 1.60-1.78 (5H, m), 2.50 (1H, m), 5.92 (1H, dd, J ) 8.7, 7.0
Hz), 6.04 (1H, d, J ) 7.0 Hz).
1
EtOAc in hexane); H NMR (300 MHz, CDCl3) δ 5.01 (1H, s),
(Z)-1-Br om o-4,8-d im eth yl-1,7-n on a d ien e (2p ):31 colorless
oil; Rf ) 0.85 (hexane); 1H NMR (300 MHz, CDCl3) δ 0.91 (3H,
d, J ) 6.7 Hz), 1.13-1.41 (2H, m), 1.61 (3H, s), 1.55-1.65 (1H,
m), 1.68 (3H, s), 1.92-2.25 (4H, m), 5.09 (1H, tm, J ) 7.1 Hz),
6.09 (1H, q, J ) 7.0 Hz), 6.19 (1H, dt, J ) 7.0, 1.5 Hz).
(Z)-1-Br om o-3-(ter t-bu tyld ip h en ylsilyl)oxy-5-p h en yl-1-
p en ten e (2q): eluted with 5% EtOAc in hexane on alumina;
6.31 (1H, d, J ) 8.1 Hz), 6.84 (2H, dm, J ) 8.7 Hz), 6.99 (1H,
d, J ) 8.1 Hz), 7.63 (2H, dm, J ) 8.7 Hz); 13C NMR (100 MHz,
CDCl3) δ 103.7, 114.8, 127.3, 130.4, 131.3, 155.5; MS (EI) m/z
(rel intensity) 200, 198 (M+, 92, 88), 76 (base). Anal. Calcd
for C8H7OBr: C, 48.27; H, 3.54. Found: C, 48.37; H, 3.36.
(Z)-â-Br om o-4-(N,N-d im eth yla m in o)styr en e (2f):30 elut-
ed with 5% EtOAc in hexane on alumina; pale yellow crystals;
1
1
colorless oil; Rf ) 0.41 (10% EtOAc in hexane); H NMR (400
mp 49-50 °C (hexane); Rf ) 0.36 (10% EtOAc in hexane); H
MHz, CDCl3) δ 1.07 (9H, s), 1.74-1.94 (2H, m), 2.54-2.65 (2H,
m), 4.70 (1H, qd, J ) 7.3, 1.1 Hz), 6.01 (1H, dd, J ) 7.3, 1.1
Hz), 6.20 (1H, t, J ) 7.3 Hz), 7.05-7.09 (2H, m), 7.14 (1H, m),
NMR (300 MHz, CDCl3) δ 2.98 (6H, s), 6.16 (1H, d, J ) 8.0
Hz), 6.70 (2H, d, J ) 9.1 Hz), 6.93 (1H, d, J ) 8.0 Hz), 7.65
(2H, d, J ) 9.1 Hz).
7.19-7.24 (2H, m), 7.31-7.44 (6H, m), 7.62-7.70 (4H, m); 13
C
(Z)-2-(â-Br om ovin yl)n a p h th a len e (2g): eluted with 5%
NMR (100 MHz, CDCl3) δ 19.3, 27.0, 30.9, 38.9, 71.6, 106.8,
125.7, 127.5, 127.6, 128.3, 128.3, 129.6, 129.6, 133.9, 135.8,
135.9, 137.7, 137.7, 142.1; MS (EI) m/z (rel intensity) 423, 421
(M+ - 57, 48, 45), 341 (25), 263 (18), 261 (16), 199 (base);
HRMS calcd for C23H22OSiBr M+ - C4H9 423.0603, 421.0623,
found m/z 423.0588, 421.0641.
EtOAc in hexane on alumina; Colorless crystals; mp 77-78
1
°C (MeOH); Rf ) 0.36 (5% EtOAc in hexane); H NMR (400
MHz, CDCl3) δ 6.52 (1H, d, J ) 8.1 Hz), 7.24 (1H, d, J ) 8.1
Hz), 7.46-7.54 (2H, m), 7.80-7.90 (4H, m), 8.17 (1H, s); 13C
NMR (75 MHz, CDCl3) δ 106.7, 126.3, 126.4, 126.5, 127.6,
127.7, 128.3, 128.6, 132.4, 133.0, 133.1, 136.9; MS (EI) m/z (rel
intensity) 234, 232 (M+, 93, 94), 153 (81), 152 (base). Anal.
Calcd for C12H9Br: C, 61.83; H, 3.89. Found: C, 61.74; H,
3.78.
Meth yl (Z)-11-br om o-10-u n d ecen oa te (2r ):34 eluted with
5% EtOAc in hexane on alumina; colorless oil; Rf ) 0.43 (10%
EtOAc in hexane); 1H NMR (300 MHz, CDCl3) δ 1.26-1.41
(10H, m), 1.58-1.64 (2H, m), 2.14-2.22 (2H, m), 2.30 (2H, t,
J ) 7.6 Hz), 3.66 (3H, s), 6.07 (1H, q, J ) 6.6 Hz), 6.13 (1H, d,
J ) 6.6 Hz).
(1Z,3E)-1-Br om o-6-p h en yl-1,3-h exa d ien e (8a ): colorless
oil; Rf ) 0.34 (hexane); 1H NMR (400 MHz, CDCl3) δ 2.47 (2H,
td, J ) 7.6, 6.9 Hz), 2.75 (2H, t, J ) 7.6 Hz), 5.96 (1H, dt, J )
15.2, 6.9 Hz), 6.05 (1H, d, J ) 7.1 Hz), 6.42 (1H, ddd, J ) 15.2,
10.1, 1.1 Hz), 6.58 (1H, dd, J ) 10.1, 7.1 Hz), 7.15-7.32 (5H,
m); 13C NMR (100 MHz, CDCl3) δ 34.7, 35.3, 106.0, 126.0,
126.5, 128.4, 128.4, 132.6, 138.3, 141.5; MS (EI) m/z (rel
intensity) 238, 236 (M+, 27, 23), 157 (42), 147 (2), 145 (2), 91
(base); HRMS calcd for C12H13Br M+ 238.0180, 236.0201, found
m/z 238.0188, 236.0185.
(1Z,3E,5E)-1-Br om o-8-p h en yl-1,3,5-octa tr ien e (8b): yel-
low oil; Rf ) 0.33 (hexane); 1H NMR (400 MHz, CDCl3) δ 2.44
(2H, td, J ) 7.4, 7.0 Hz), 2.72 (2H, t, J ) 7.4 Hz), 5.86 (1H, dt,
J ) 15.0, 7.0 Hz), 6.11 (1H, d, J ) 7.1 Hz), 6.18 (1H, ddt, J )
15.0, 9.9, 1.5 Hz), 6.36 (1H, dd, J ) 15.0, 9.2 Hz), 6.43 (1H,
dd, J ) 15.0, 9.2 Hz), 6.62 (1H, dd, J ) 9.9, 7.1 Hz), 7.16-
7.35 (5H, m); 13C NMR (100 MHz, CDCl3) δ 34.7, 35.4, 107.4,
125.9, 126.2, 128.3, 128.4, 130.7, 132.6, 136.5, 136.7, 141.5;
MS (EI) m/z (rel intensity) 264, 262 (M+, 96, 97), 183 (46), 173
(74), 171 (77), 156 (41), 91 (base); HRMS calcd for C14H15Br
M+ 264.0337, 262.0357, found m/z 264.0320, 262.0347.
(1Z,3E)-1-Br om o-3,5-d im et h yl-6-(2-t et r a h yd r op yr a n -
yl)oxy-1,3-h exa d ien e (8c): eluted with 2.5% EtOAc in hexane
on alumina; colorless oil; Rf ) 0.25 (5% EtOAc in hexane); 1H
NMR (400 MHz, CDCl3) δ 1.03 (3/2H, d, J ) 7.0 Hz) and 1.04
(3/2H, d, J ) 6.6 Hz), 1.46-1.88 (6H, m), 1.98 (3/2H, d, J )
1.5 Hz) and 1.99 (3/2H, d, J ) 1.5 Hz), 2.80 (1H, m), 3.26 (1H,
m), 3.50 (1H, m), 3.60 (1H, m), 3.86 (1H, m), 4.60 (1H, m),
5.51 (1/2H, d, J ) 9.2 Hz) and 5.53 (1/2H, d, J ) 8.8 Hz), 6.01
(1/2H, d, J ) 8.1 Hz) and 6.02 (1/2H, d, J ) 8.1 Hz), 6.53 (1/
2H, d, J ) 8.1 Hz) and 6.54 (1/2H, d, J ) 8.1 Hz); 13C NMR
(100 MHz, CDCl3) δ 16.0, 17.2 and 17.3, 19.4, 25.5, 30.6 and
30.6, 33.1 and 33.2, 62.1, 71.7 and 71.9, 98.7 and 98.8, 102.6
and 102.7, 131.6 and 131.7, 136.2, 137.9 and 138.1; MS (EI)
m/z (rel intensity) 290, 288 (M+, 2, 2), 209 (2), 167 (8), 148 (9),
146 (9), 101 (20), 85 (base); HRMS calcd for C13H21O2Br M+
290.0705, 288.0725, found m/z 290.0683, 288.0702.
(Z)-1-(â-Br om ovin yl)n a p h th a len e (2h ):31 eluted with
2.5% EtOAc in hexane on alumina; colorless oil; Rf ) 0.42
1
(hexane); H NMR (300 MHz, CDCl3) δ 6.75 (1H, d, J ) 8.0
Hz), 7.48-7.58 (3H, m), 7.60 (1H, d, J ) 8.0 Hz), 7.71 (1H, dt,
J ) 7.2, 1.1 Hz), 7.83-7.94 (3H, m).
(Z)-2-(â-Br om ovin yl)p yr id in e (2i):32 purified by silica gel
column chromatography eluted with 30% EtOAc in hexane;
light brown oil; Rf ) 0.25 (20% EtOAc in hexane); 1H NMR
(300 MHz, CDCl3) δ 6.67 (1H, d, J ) 8.5 Hz), 7.23 (1H, ddd, J
) 7.8, 4.8, 1.1 Hz), 7.26 (1H, d, J ) 8.5 Hz), 7.73 (1H, td, J )
7.8, 1.8 Hz), 8.04 (1H, dt, J ) 7.8, 1.1 Hz), 8.64 (1H, dt, J )
4.8, 1.2 Hz).
(Z)-3-(â-Br om ovin yl)p yr id in e (2j):32 purified by silica gel
column chromatography eluted with 20% EtOAc in hexane;
1
colorless oil; Rf ) 0.28 (30% EtOAc in hexane); H NMR (400
MHz, CDCl3) δ 6.58 (1H, d, J ) 8.2 Hz), 7.06 (1H, d, J ) 8.2
Hz), 7.31 (1H, dd, J ) 8.0, 4.8 Hz), 8.14 (1H, dt, J ) 8.0, 1.8
Hz), 8.54 (1H, dd, J ) 4.8, 1.5 Hz), 8.76 (1H, d, J ) 2.0 Hz).
(Z)-4-(â-Br om ovin yl)p yr id in e (2k ):32 purified by silica gel
column chromatography eluted with 40% EtOAc in hexane;
1
colorless oil; Rf ) 0.32 (40% EtOAc in hexane); H NMR (300
MHz, CDCl3) δ 6.68 (1H, d, J ) 8.3 Hz), 7.05 (1H, d, J ) 8.3
Hz), 7.56 (2H, dd, J ) 4.5, 1.7 Hz), 8.64 (2H, dd, J ) 4.5, 1.7
Hz).
(Z)-2-(â-Br om ovin yl)qu in olin e (2l): purified by silica gel
column chromatography eluted with 10% EtOAc in hexane;
yellow oil; Rf ) 0.36 (10% EtOAc in hexane); 1H NMR (400
MHz, CDCl3) δ 6.80 (1H, d, J ) 8.4 Hz), 7.46 (1H, d, J ) 8.4
Hz), 7.55 (1H, td, J ) 8.0, 0.9 Hz), 7.71 (1H, td, J ) 8.0, 1.4
Hz), 8.01 (1H, dd, J ) 8.0, 0.7 Hz), 8.08 (1H, d, J ) 8.0 Hz),
8.12 (1H, d, J ) 8.6 Hz), 8.19 (1H, d, J ) 8.6 Hz); 13C NMR
(100 MHz, CDCl3) δ 110.4, 121.3, 126.9, 127.3, 127.5, 129.3,
129.8, 133.8, 135.9, 148.0, 154.3; MS (EI) m/z (rel intensity)
235, 233 (M+, 20, 20), 154 (base), 128 (39); HRMS calcd for
C
11H8NBr M+ 232.9840, 234.9819, found m/z 232.9821,
234.9789.
(Z)-1-Br om o-4-p h en yl-1-bu ten e (2m ):16 colorless oil; Rf
) 0.45 (hexane); 1H NMR (300 MHz, CDCl3) δ 2.52 (2H, td, J
) 7.3, 6.9 Hz), 2.72 (2H, t, J ) 7.3 Hz), 6.11 (1H, q, J ) 6.9
Hz), 6.17 (1H, dt, J ) 6.9, 1.1 Hz), 7.17-7.32 (5H, m).
(Z)-1-Br om o-3-p h en yl-1-bu ten e (2n ):33 colorless oil; Rf )
0.48 (hexane); H NMR (300 MHz, CDCl3) δ 1.39 (3H, d, J )
7.3 Hz), 4.02 (1H, qd, J ) 7.3, 7.0 Hz), 6.19 (1H, q, J ) 7.0
Hz), 6.22 (1H, d, J ) 7.0 Hz), 7.19-7.33 (5H, m).
(1Z,3Z)-1-Br om o-3,5-d im et h yl-6-(2-t et r a h yd r op yr a n -
yl)oxy-1,3-h exa d ien e (8d ): eluted with 5% EtOAc in hexane
on alumina; colorless oil; Rf ) 0.30 (7.5% EtOAc in hexane);
1H NMR (300 MHz, CDCl3) δ 1.00 (3/2H, d, J ) 6.7 Hz) and
1.01 (3/2H, d, J ) 6.6 Hz), 1.46-1.86 (6H, m), 1.96 (3H, s),
1
(30) Akiyama, S.; Nakatsuji, S.; Yoshida, K.; Nakashima, K.; Hagi-
wara, T.; Tsuruta, H.; Yoshida, T. Bull. Chem. Soc. J pn. 1983, 56, 361.
(31) Matsumoto, M.; Kuroda, K. Tetrahedron Lett. 1980, 21, 4021.
(32) Benckova, M. Kovac, Chem. Pap-Chem. Zvesti 1989, 43, 439.
(33) Harada, T.; Katsuhira, T.; Hara, D.; Kotani, Y.; Maejima, K.;
Kaji, R.; Oku, A. J . Org. Chem. 1993, 58, 4897.
(34) Kabalka, G. W.; Sastry, K. A. R. Synth. Commun. 1983, 13,
1027.

Hydrogenolysis of 1,1-Dibromo-1-alkenes
J . Org. Chem., Vol. 63, No. 24, 1998 8973
2.65 (1H, m), 3.23 (1H, m), 3.48 (1H, m), 3.55 (1H, m), 3.84
(1H, m), 4.56 (1/2H, d, J ) 3.7 Hz) and 4.57 (1/2H, d, J ) 2.9
Hz), 5.25 (1H, m), 6.20 (1H, d, J ) 7.7 Hz), 6.81 (1H, d, J )
7.7 Hz); 13C NMR (100 MHz, CDCl3) δ 17.4 and 17.5, 19.4 and
19.4, 22.4, 25.5, 30.6 and 30.6, 33.8 and 33.9, 62.0 and 62.1,
71.7 and 71.9, 98.5 and 98.7, 106.8 and 106.8, 131.1 and 131.2,
132.4, 134.4 and 134.6; MS (EI) m/z (rel intensity) 290, 288
(M+, 3, 3), 209 (4), 189 (3), 187 (3), 85 (base); HRMS calcd for
9.8 Hz), 6.05 (1H, t, J ) 1.5 Hz);13C NMR (100 MHz, CDCl3)
δ 24.7, 28.5, 32.3, 35.7, 104.2, 124.6, 128.4, 140.4. Z-Isom er :
1H NMR (300 MHz, CDCl3) δ 1.04 (6H, s), 1.52 (2H, t, J ) 6.5
Hz), 2.36 (2H, td, J ) 6.5, 1.5 Hz), 5.77 (1H, dd, J ) 10.0, 1.7
Hz), 5.86 (1H, m), 6.35 (1H, dd, J ) 10.0, 0.9 Hz);13C NMR
(100 MHz, CDCl3) δ 28.0, 28.7, 32.6, 36.6, 100.4, 122.1, 137.8,
144.0.
(Z)-â-Br om o-r-m eth ylstyr en e (10e).35 Ma jor Z-isom er :
colorless oil; Rf ) 0.57 (hexane); 1H NMR (400 MHz, CDCl3) δ
2.12 (3H, d, J ) 1.4 Hz), 6.23 (1H, d, J ) 1.4 Hz), 7.18-7.40
(5H, m).
C
13H21O2Br M+ 290.0705, 288.0725, found m/z 290.0724,
288.0735.
(Z)-1-[2-(1-Br om ovin yl)]cycloh exen e (8e): colorless oil;
1
Rf ) 0.80 (hexane); H NMR (300 MHz, CDCl3) δ 1.53-1.70
(E)- a n d (Z)-1-Br om o-2-(2-p yr id yl)-p r op en e (10f): eluted
with 10% EtOAc in hexane on alumina. E-Isom er : colorless
oil; Rf ) 0.42 (15% EtOAc in hexane);1H NMR (400 MHz,
CDCl3) δ 2.28 (3H, d, J ) 1.1 Hz), 7.15 (1H, d, J ) 1.4 Hz),
7.19 (1H, ddd, J ) 7.8, 5.0, 0.9 Hz), 7.37 (1H, dt, J ) 7.8, 0.8
Hz), 7.66 (1H, td, J ) 7.8, 1.9 Hz), 8.57 (1H, dt, J ) 5.0, 0.9
Hz); 13C NMR (100 MHz, CDCl3) δ 17.7, 110.8, 120.0, 122.4,
136.6, 140.3, 149.2, 157.1; MS (FAB) m/z 200, 198 (MH+);
HRMS calcd for C8H9NBr MH+ 199.9898, 197.9918, found m/z
199.9910, 197.9947. Z-isom er : colorless oil; Rf ) 0.32 (15%
(4H, m), 2.05-2.15 (2H, m), 2.40-2.47 (2H, m), 5.97 (1H, d, J
) 8.4 Hz), 6.00 (1H, br s), 6.49 (1H, d, J ) 8.4 Hz); 13C NMR
(100 MHz, CDCl3) δ 21.8, 22.5, 25.8, 28.0, 101.4, 132.4, 134.1,
135.0; MS (EI) m/z (rel intensity) 188, 186 (M+, 23, 23), 107
(90), 79 (base); HRMS calcd for C8H11Br M+ 188.0024, 186.0044,
found m/z 187.9998, 186.0040.
(Z)-1-Br om o-4-cycloh exylid en e-1,3-bu ta d ien e (8f): col-
orless oil; Rf ) 0.65 (hexane); 1H NMR (300 MHz, CDCl3) δ
1.52-1.70 (6H, m), 2.17-2.24 (2H, m), 2.24-2.32 (2H, m), 6.06
(1H, d, J ) 7.1 Hz), 6.10 (1H, dd, J ) 10.6, 1.5 Hz), 6.86 (1H,
dd, J ) 10.6, 7.1 Hz); 13C NMR (100 MHz, CDCl3) δ 26.6, 27.7,
28.4, 30.1, 37.5, 106.3, 117.7, 128.0, 148.7; MS (EI) m/z (rel
intensity) 202, 200 (M+, 13, 13), 181 (40), 169 (45), 151 (10),
1
EtOAc in hexane); H NMR (400 MHz, CDCl3) δ 2.22 (3H, d,
J ) 1.5 Hz), 6.38 (1H, q, J ) 1.5 Hz), 7.22 (1H, ddd, J ) 7.7,
4.7, 1.0 Hz), 7.54 (1H, dt, J ) 7.7, 0.9 Hz), 7.70 (1H, td, J )
7.7, 1.7 Hz), 8.65 (1H, dt, J ) 4.7, 1.0 Hz); 13C NMR (100 MHz,
CDCl3) δ 23.4, 102.9, 122.5, 123.8, 135.9, 141.2, 149.4, 157.8;
MS (FAB) m/z 200, 198 (MH+); HRMS calcd for C8H9NBr MH+
199.9898, 197.9918, found m/z 199.9925, 197.9915.
131 (44), 121 (35), 119 (46), 69 (base); HRMS calcd for C9H13
-
Br M+ 202.0180, 200.0201, found m/z 202.0198, 200.0213.
(Z)-1-Br om o-4-p h en yl-1-bu ten -3-yn e (8g): colorless oil;
Rf ) 0.34 (hexane); 1H NMR (300 MHz, CDCl3) δ 6.53 (1H, d,
J ) 7.6 Hz), 6.65 (1H, d, J ) 7.6 Hz), 7.32-7.38 (3H, m), 7.48-
7.54 (2H, m); 13C NMR (100 MHz, CDCl3) δ 85.2, 97.1, 115.7,
117.8, 122.7, 128.4, 128.8, 131.7; MS (EI) m/z (rel intensity)
208, 206 (M+, 60, 62), 127 (76), 101 (5), 78 (base); HRMS calcd
for C10H7Br M+ 207.9711, 205.9731, found m/z 207.9736,
205.9745.
1,1-Diiod o-4-p h en yl-1-bu ten e (3). Finely grounded car-
bon tetraiodide (3.87 g, 7.44 mmol) was dissolved in CH2Cl2
(120 mL), to which was added PPh3 (3.9 g, 14.9 mmol) at 0 °C
all at once, and the mixture was stirred for 15 min at the same
temperature. Then hydrocinnamaldehyde (0.5 g, 3.72 mmol)
was added. The mixture was stirred for 10 min at 0 °C and
for an additional 15 min at room temperature. The reaction
was diluted with hexane (100 mL) and directly purified on
silica gel column chromatography. Elution with hexane gave
3 (1.0 g) in 70% yield: colorless oil; Rf ) 0.52 (hexane); 1H
NMR (400 MHz, CDCl3) δ 2.21-2.28 (2H, m), 2.73 (2H, t, J )
7.6 Hz), 6.98 (1H, t, J ) 7.0 Hz), 7.16-7.33 (5H, m); 13C NMR
(125 MHz, CDCl3) δ 12.5, 33.4, 41.2, 126.2, 128.4, 128.5, 140.4,
151.9; MS (EI) m/z (rel intensity) 384 (M+, 7), 257 (35), 130
(19), 91 (base); HRMS calcd for C10H10I2 M+ 383.8873, found
m/z 383.8864.
(Z)-1-Br om o-4-tr im eth ylsilyl-1-bu ten -3-yn e (8h ): color-
less oil; Rf ) 0.46 (hexane); 1H NMR (300 MHz, CDCl3) δ 0.23
(9H, s), 6.32 (1H, d, J ) 7.7 Hz), 6.60 (1H, d, J ) 7.7 Hz); 13
C
NMR (100 MHz, CDCl3) δ -0.3, 99.9, 103.5, 115.7, 118.8; MS
(EI) m/z (rel intensity) 204, 202 (M+, 4, 4), 122 (1), 107 (13),
69 (base); HRMS calcd for C7H11BrSi M+ 203.9793, 201.9813,
found m/z 203.9799, 201.9821.
1-(Br om om eth ylid en e)-4-p h en ylcycloh exa n e (10a ): col-
orless crystals; mp 27-28 °C; Rf ) 0.45 (hexane); 1H NMR (300
MHz, CDCl3) δ 1.45-1.60 (2H, m), 1.90-2.06 (3H, m), 2.21
(1H, m), 2.50 (1H, dm, J ) 13.7 Hz), 2.70 (1H, tt, J ) 12.2, 3.2
Hz), 3.03 (1H, dm, J ) 13.7 Hz), 5.93 (1H, t, J ) 1.8 Hz), 7.16-
7.33 (5H, m); 13C NMR (75 MHz, CDCl3) δ 30.9, 33.8, 35.0,
35.2, 44.1, 98.3, 126.2, 126.8, 128.4, 143.8, 146.1; MS (EI) m/z
(rel intensity) 252, 250 (M+, 19, 19), 171 (36), 91 (base). Anal.
Calcd for C13H15Br: C, 62.17; H, 6.02. Found: C, 62.34; H,
6.16.
Hyd r ogen olysis of 3. The hydrogenolysis of 1,1-diiodo-4-
phenyl-1-butene 3 (100 mg, 0.26 mmol) was performed by the
same procedure as described for 1,1-dibromo-1-alkenes. Pu-
rification was made by alumina column chromatography eluted
with hexane. The first elution gave (Z)-4-phenyl-1-(tributyl-
stannyl)butene (5)16 (12 mg) in 11% yield, the second elution
with the same eluent gave (Z)-4-phenyl-1-iodobutene (4) (18
mg) in 27% yield, and the third elution gave the recovery of
starting material in 27% yield. Phenyl-1-butene (6)35 was
identified from the proton NMR spectrum of the crude mixture,
but present in less than 5%. (Z)-4-p h en yl-1-(tr ibu tylsta n -
(1E,3E)- a n d (1Z,3E)-1-Br om o-2-m eth yl-4-p h en yl-1,3-
bu ta d ien e (10c): E- and Z-isomers were separated by HPLC
(silica gel, hexane). 1E,3E-isom er : colorless oil; Rf ) 0.51
1
(hexane); H NMR (400 MHz, CDCl3) δ 1.98 (3H, d, J ) 0.7
1
n yl)bu ten e (5):16 colorless oil; Rf ) 0.71 (hexane); H NMR
Hz), 6.34 (1H, s), 6.56 (1H, d, J ) 16.0 Hz), 6.71 (1H, d, J )
16.0 Hz), 7.16-7.38 (5H, m); 13C NMR (100 MHz, CDCl3) δ
15.4, 110.0, 126.5, 127.7, 128.7, 128.9, 129.0, 137.0, 139.8; MS
(FAB) m/z 225, 223 (MH+); HRMS calcd for C11H12Br MH+
225.0102, 223.0122, found m/z 225.0111, 223.0107. 1Z,3E-
isom er : colorless oil; Rf ) 0.51 (hexane); 1H NMR (300 MHz,
CDCl3) δ 2.02 (3H, d, J ) 1.5 Hz), 6.16 (1H, s), 6.74 (1H, d, J
) 16.2 Hz), 7.26-7.40 (4H, m), 7.49-7.54 (2H, m);13C NMR
(75 MHz, CDCl3) δ 19.5, 105.9, 126.2, 126.9, 128.1, 128.7,
132.1, 136.7, 136.9; MS (EI) m/z (rel intensity) 224, 222 (M+,
74, 76), 144 (24), 143 (base), 142 (58), 141 (50), 128 (99); HRMS
calcd for C11H11Br M+ 224.0024, 222.0044, found m/z 223.9986,
222.0007.
1-(Bromomethylidene)-4,4-dimethyl-2-cyclohexene (10d):
an inseparable mixture with 9d , E- and Z-isomers of 10d ;
colorless oil; Rf ) 0.77 (hexane); 1H and 13C NMR were
assigned from a mixture of the spectra. E-Isom er : 1H NMR
(300 MHz, CDCl3) δ 1.02 (6H, s), 1.54 (2H, t, J ) 6.5 Hz), 2.44
(2H, t, J ) 6.5 Hz), 5.58 (1H, d, J ) 9.8 Hz), 5.92 (1H, d, J )
(400 MHz, CDCl3) δ 0.80-0.90 (15H, m), 1.25-1.34 (6H, m),
1.40-1.50 (6H, m), 2.30-2.36 (2H, m), 2.68 (2H, t, J ) 7.6
Hz), 5.84 (1H, dt, J ) 12.3, 1.2 Hz), 6.55 (1H, dt, J ) 12.3, 7.0
Hz), 7.15-7.30 (5H, m). (Z)-4-P h en yl-1-iod obu ten e (4):
colorless oil; Rf ) 0.55 (hexane); 1H NMR (400 MHz, CDCl3) δ
2.44-2.50 (2H, m), 2.74 (2H, t, J ) 7.4 Hz), 6.21 (1H, m), 6.23
(1H, d, J ) 7.4 Hz), 7.16-7.33 (5H, m); 13C NMR (125 MHz,
CDCl3) δ 34.0, 36.3, 83.1, 126.0, 128.4, 128.4, 140.2, 141.0; MS
(EI) m/z (rel intensity) 258 (M+, 6), 257 (40), 131 (18), 130 (23),
91 (base); HRMS calcd for C10H11I M+ 257.9906, found m/z
257.9874.
Su zu k i Cou p lin g of 7a w ith Alk en ylbor on ic Acid . To
a degassed solution of 7a (26 mg, 0.082 mmol), (E)-1-(3-methyl-
1-butenyl)boronic acid (11 mg, 0.1 mmol), and Pd(PPh3)4 (9.5
mg, 8.2 µmol) in anhydrous THF (0.6 mL) was added TlOH
(35) Charreau, P.; J ulia, M.; Verpeaux, J .-N. J . Organomet. Chem.
1989, 379, 201.

8974 J . Org. Chem., Vol. 63, No. 24, 1998
Uenishi et al.
(0.44 mL, 10% solution in water) at room temperature. The
mixture was stirred for 1 h, diluted with hexane (30 mL), and
washed with water and brine. The extract was dried over
MgSO4, and the solvent was removed. The residual oil was
purified by column chromatography on silica gel eluted with
hexane to give 11 (18.6 mg) in 74% yield: colorless oil; Rf )
in anhydrous benzene (2 mL) and sodium ethoxide (2.0 M in
ethanol, 0.64 mL, 1.28 mmol) were added and heated for 30
min at 90 °C (bath temperature). The same workup and
purification described in the above experiment except column
chromatography using alumina gave 52% yield of 14 and (E)-
6-phenyl-1,3-hexadiene in 41% yield.
1
0.47 (hexane); H NMR (400 MHz, CDCl3) δ 1.06 (6H, d, J )
Syn th esis of (3Z,5E)-8-P h en yl-1-tr im eth ylsilyl-3,5-oc-
ta d ien -1-yn e (15). To a stirred degassed solution of 8a (100
mg, 0.42 mmol) in anhydrous benzene (2 mL) were added
trimethylsilylacetylene (92 µL, 0.64 mmol), diisopropylamine
(118 µL, 0.84 mmol), cuprous iodide (8 mg, 0.042 mmol), and
Pd(PPh3)4 (19.4 mg, 0.017 mmol) successively to the reaction
mixture. The reaction mixture was stirred at room temper-
ature for 1 h and then diluted with hexane and washed with
water and brine. The organic layer was dried over MgSO4,
and the solvent was evaporated. The residual oil was purified
by column chromatography on silica gel eluted with hexane
to give enyne 15 (100 mg) in 93% yield: colorless oil; Rf ) 0.19
(hexane); 1H NMR (400 MHz, CDCl3) δ 0.22 (9H, s), 2.50 (2H,
td, J ) 7.3, 7.0 Hz), 2.76 (2H, t, J ) 7.3 Hz), 5.36 (1H, d, J )
11.0 Hz), 5.94 (1H, dt, J ) 15.4, 7.0 Hz), 6.37 (1H, t, J ) 11.0
Hz), 6.63 (1H, ddd, J ) 15.4, 11.0, 1.1 Hz), 7.16-7.32 (5H, m);
13C NMR (100 MHz, CDCl3) δ 0.0, 34.6, 35.3, 100.4, 102.3,
107.2, 125.9, 128.2, 128.4, 128.4, 133.4, 138.1, 141.3; MS (EI)
m/z (rel intensity) 254 (M+, base), 239 (46), 181 (19), 180 (47),
163 (49), 150 (48), 135 (77); HRMS calcd for C17H22Si M+
254.1490, found m/z 254.1515. On e-P ot P r oced u r e of 15
fr om 7a . Hydrogenolysis of 7a was carried out under the
same conditions as described for the general procedure. After
the hydrogenolysis was complete, alkyne (1.5 equiv), diisopro-
pylamine (6 equiv), and cuprous iodide (0.3 equiv) were added
successively to the reaction mixture. The reaction was com-
pleted in 1 h. Workup of the reaction and purification
described in the above experiment except column chromatog-
raphy with alumina gave 61% yield of 15.
Syn th esis of En ed iyn es, 16, 17, a n d 18: Gen er a l On e-
P ot P r oced u r e fr om 1,1-Dibr om o-4-p h en yl-1-bu ten -3-
yn e. After the hydrogenolysis was complete, alkyne (1.5
equiv), diisopropylamine (6 equiv), and cuprous iodide (0.3
equiv) were added successively to the reaction mixture. The
reaction was monitored by TLC. It was complete in 10 min
with trimethylsilylacetylene, 15 min with 3-(tert-butyldimeth-
ylsilyl)oxy-5-phenyl-1-pentyne, and 3-hydroxy-5-phenyl-1-pen-
tyne. The mixture was diluted with hexane (ether for the case
of 18), washed with water and brine, and dried over MgSO4.
The solvent was evaporated, and the residual oil was purified
by alumina column chromatography.
7.0 Hz), 2.40-2.53 (3H, m), 2.75 (2H, t, J ) 7.3 Hz), 5.93 (1H,
dt, J ) 15.0, 7.0 Hz), 6.02 (1H, d, J ) 15.0 Hz), 6.10 (1H, dd,
J ) 15.0, 6.6 Hz), 6.37 (1H, d, J ) 10.3 Hz), 6.54 (1H, ddt, J
) 15.0, 10.3, 1.5 Hz), 7.17-7.32 (5H, m); 13C NMR (100 MHz,
CDCl3) δ 22.4, 31.0, 34.9, 35.5, 121.0, 123.4, 125.9, 126.8, 128.4,
128.9, 129.9, 137.5, 141.5, 142.8; MS (EI) m/z (rel intensity)
306, 304 (M+, 62, 61), 215 (81), 213 (82), 187 (8), 185 (9), 173
(20), 171 (19), 91 (base); HRMS calcd for C17H21Br M+
306.0806, 304.0827, found m/z 306.0815, 304.0801.
Son oga sh ir a Cou p lin g of 7a w ith P h en yla cetylen e. To
a mixture of 7a (77 mg, 0.24 mmol), phenylacetylene (30 mg,
0.29 mmol), Pd(PPh3)4 (14 mg, 0.012 mmol), and CuI (4.6 mg,
0.024 mmol) in anhydrous degassed benzene (2 mL) was added
diisopropylamine (68 µL, 0.48 mmol). After the reaction was
stirred for 1 h at room temperature, the mixture was diluted
with benzene (20 mL) and water (5 mL). The benzene layer
was washed with water and brine, dried over MgSO4, and
evaporated. The crude oil was purified by column chroma-
tography on silica gel. Elution with hexane gave the recovery
of 7a (13 mg) in 17% yield, elution with 4% benzene in hexane
gave 12 (29 mg) in 36% yield, and elution of 10% benzene in
hexane gave 13 (28 mg) in 33% yield. (3Z,5E)-3-Br om o-1,8-
d ip h en yl-3,5-octa d ien -1-yn e (12): unstable light yellow oil;
Rf ) 0.29 (hexane);1H NMR (400 MHz, CDCl3) δ 2.46-2.54
(2H, m), 2.77 (2H, t, J ) 8.0 Hz), 6.08 (1H, dtd, J ) 15.4, 7.0,
0.7 Hz), 6.45 (1H, ddt, J ) 15.4, 10.3, 1.5 Hz), 6.79 (1H, d, J
) 10.3 Hz), 7.17-7.47 (10H, m); 13C NMR (100 MHz, CDCl3)
δ 35.0, 35.2, 88.7, 91.7, 99.7, 122.1, 126.0, 128.4, 128.4, 128.4,
128.8, 131.6, 131.6, 137.0, 140.3, 141.2; MS (EI) m/z (rel
intensity) 338, 336 (M+, 24, 26), 257 (19), 247 (25), 245 (25),
229 (11), 165 (base); HRMS calcd for C20H17Br M+ 338.0493,
336.0514, found m/z 338.0500, 336.0494. (5E)-1,8-Dip h en yl-
3-[2-(1-p h en yleth yn yl)]-3,5-octa d ien -1-yn e (13): unstable
yellow oil; Rf ) 0.11 (hexane);1H NMR (400 MHz, CDCl3) δ
2.52-2.59 (2H, m), 2.79 (2H, t, J ) 7.3 Hz), 6.07 (1H, dt, J )
14.7, 7.3 Hz), 6.75 (1H, ddt, J ) 14.7, 11.4, 1.5 Hz), 6.83 (1H,
d, J ) 11.4 Hz), 7.17-7.55 (15H, m); 13C NMR (100 MHz,
CDCl3) δ 35.0, 35.3, 85.2, 88.4, 89.0, 94.1, 102.9, 122.9, 123.0,
126.0, 128.3, 128.3, 128.3, 128.4, 128.5, 128.6, 131.6, 131.6,
131.6, 139.9, 141.3, 144.6; MS (EI) m/z (rel intensity) 358 (M+,
49), 281 (15), 265 (base); HRMS calcd for C28H22 M+ 358.1722,
found m/z 358.1725.
(Z)-6-P h en yl-1-tr im eth ylsilyl-3-h exen -1,5-d iyn e (16):37
eluted with hexane in chromatographic purification; yield 70%;
colorless oil; Rf ) 0.20 (hexane); 1H NMR (400 MHz, CDCl3) δ
0.25 (9H, s), 5.90 (1H, d, J ) 11.0 Hz), 6.08 (1H, d, J ) 11.0
Hz), 7.32-7.36 (3H, m), 7.46-7.52 (2H, m); 13C NMR (100
MHz, CDCl3) δ -0.1, 87.1, 97.6, 102.2, 103.3, 119.3, 120.7,
123.0, 128.3, 128.6, 131.8; MS (EI) m/z (rel intensity) 224 (M+,
98), 209 (base), 194 (36), 170 (25), 165 (60); HRMS calcd for
Syn th esis of (3E,5Z,7E)-2-Meth yl-10-p h en yl-3,5,7-d ec-
a tr ien e (14). To a solution of 8a (50 mg, 0.21 mmol) and (E)-
2-(3-methyl-1-butenyl)-1,3,2-benzodioxaborole (59 mg, 0.32
mmol) in anhydrous benzene (1 mL) were added Pd(PPh3)4 (10
mg, 8.4 µmol) and sodium ethoxide (2.0 M in ethanol, 0.21 mL,
0.42 mmol). The mixture was degassed quickly by bubbling
with Ar and then heated for 10 min at 90 °C (bath tempera-
ture). After cooling, the mixture was diluted with hexane (30
mL), washed with water and brine, and dried over MgSO4.
The solvent was removed, and the residual oil was purified
by column chromatography on silica gel eluted with hexane
to give 14 (41 mg) in 85% yield: colorless oil; Rf ) 0.34
C
15H16Si M+ 224.1021, found m/z 224.1031.
(Z)-7-(ter t-Bu tyld im eth ylsilyl)oxy-1,9-d ip h en yl-3-n on -
en e-1,5-d iyn e (17): eluted with 2.5% EtOAc in hexane in
chromatographic purification; yield 64%; colorless oil; Rf ) 0.20
(2.5% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 0.11
(3H, s), 0.14 (3H, s), 0.90 (9H, s), 2.03-2.11 (2H, m), 2.83 (2H,
tm, J ) 8.4 Hz), 4.60 (1H, td, J ) 6.2, 1.8 Hz), 5.90 (1H, dd, J
) 11.0, 1.8 Hz), 6.03 (1H, d, J ) 11.0 Hz), 7.14-7.32 (8H, m),
7.41-7.45 (2H, m); 13C NMR (100 MHz, CDCl3) δ -5.0, -4.4,
18.2, 25.8, 31.4, 40.3, 62.9, 82.0, 86.9, 96.8, 98.9, 119.0, 119.5,
123.0, 125.8, 128.2, 128.3, 128.4, 128.5, 131.7, 141.6; MS (EI)
m/z (rel intensity) 400 (M+, 3), 343 (18), 269 (base), 209 (55);
HRMS calcd for C27H32OSi M+ 400.2222, found m/z 400.2242.
(Z)-1,9-Diph en yl-7-h ydr oxy-3-n on en -1,5-diyn e (18): elut-
ed with 10% EtOAc in hexane in chromatographic purification;
1
(hexane); H NMR (400 MHz, CDCl3) δ 1.03 (6H, d, J ) 6.8
Hz), 2.38 (1H, dqd, J ) 6.9, 6.8, 0.9 Hz), 2.45 (2H, td, J ) 7.3,
7.0 Hz), 2.73 (2H, t, J ) 7.3 Hz), 5.67 (1H, dd, J ) 15.1, 6.9
Hz), 5.73 (1H, dt, J ) 15.1, 7.0 Hz), 5.82-5.89 (2H, m), 6.42
(1H, ddd, J ) 15.1, 8.8, 1.5 Hz), 6.53 (1H, ddd, J ) 15.1, 8.8,
1.5 Hz), 7.16-7.32 (5H, m); 13C NMR (100 MHz, CDCl3) δ 22.4,
31.4, 34.8, 35.9, 122.7, 125.8, 126.3, 127.5, 128.3, 128.3, 128.4,
134.1, 141.8, 142.7; MS (EI) m/z (rel intensity) 226 (M+, base),
135 (99), 107 (55), 105 (17); HRMS calcd for C17H22 M+
226.1722, found m/z 226.1730. On e-P ot P r oced u r e of 14
fr om 7a . Hydrogenolysis of 7a (100 mg, 0.42 mmol) was
carried out under the same conditions as described for the
general procedure. After the reaction was complete, (E)-2-(3-
methyl-1-butenyl)-1,3,2-benzodioxaborole (120 mg, 0.64 mmol)-
1
yield 54%; colorless oil; Rf ) 0.25 (15% EtOAc in hexane); H
(36) Pilcher, A. S.; DeShong, P. J . Org. Chem. 1996, 61, 6901.
(37) Wang, K. K.; Wang, Z.; Gu, Y. G. Tetrahedron Lett. 1993, 34,
8391.

Hydrogenolysis of 1,1-Dibromo-1-alkenes
J . Org. Chem., Vol. 63, No. 24, 1998 8975
NMR (400 MHz, CDCl3) δ 1.95 (1H, d, J ) 5.1 Hz), 2.06-2.15
(2H, m), 2.86 (2H, t, J ) 7.7 Hz), 4.60 (1H, dm, J ) 5.1 Hz),
5.91 (1H, dd, J ) 11.0, 1.8 Hz), 6.08 (1H, d, J ) 11.0 Hz), 7.14-
7.33 (8H, m), 7.42-7.46 (2H, m); 13C NMR (100 MHz, CDCl3)
δ 31.4, 39.2, 62.4, 82.9, 86.8, 97.3, 97.9, 118.7, 120.2, 122.8,
126.0, 128.4, 128.4, 128.5, 128.7, 131.7, 141.0; MS (EI) m/z (rel
intensity) 286 (M+, 5), 268 (base), 267 (82), 253 (23), 252 (18);
HRMS calcd for C21H18O M+ 286.1358, found m/z 286.1346.
istered by the J apan Private School Promotion Founda-
tion and Chemipro Kasei Co ltd. are greatly acknowl-
edged.
Su p p or tin g In for m a tion Ava ila ble: 13C NMR spectra for
29 new compounds, general experimental procedures for 1,1-
dibromo-1-alkenes from aldehydes, and physical and spectro-
scopic data for the 31 new and known compounds (41 pages).
This material is contained in libraries on microfiche, im-
mediately follows this article in the microfilm version of the
journal, and can be ordered from the ACS; see any current
masthead page for ordering information.
Ack n ow led gm en t. We thank Mr. Yasuo Shiga and
Ms. Hitomi Maekawa for their technical assistance in
this project. This work was supported by a Grant-in-
Aid for Scientific Research on Priority Area No. 08245101
from Ministry of Education, Science, Sports and Culture
of J apanese Government. Cooperative Research admin-
J O9812781