One post stereoselective synthesis of chiral αω-diynes from bromoallenes and organobis(heterocuprates)

Article abstract of DOI:10.1016/S0022-328X(01)01438-3

Organobis(heterocuprates), 7 and 8, have been prepared reacting in situ 1,4-dilithiobutane and di-Grignard reagents, obtained from 1,4-dibromobutane and 1,4-dibromobenzene, respectively, with CuSPh and LiCuBr₂. The cross-coupling reaction of these di-cuprate reagents with 3-alkyl and 3,3-dialkyl 1-bromo-1,2-dienes (1) provides a general method for selective synthesis of 1,9-decadiynes (5) and 1,4-bis(2-propynyl)benzenes (6), characterized by two identical chiral centres in the α position to the triple bonds. The high 1,3-anti stereoselectivity of the coupling process allows us to obtain enantiomerically enriched α,ω-diynes 5 and 6 starting from optically active allenic substrates 1.

Full text of DOI:10.1016/S0022-328X(01)01438-3

Journal of Organometallic Chemistry 648 (2002) 109–118
www.elsevier.com/locate/jorganchem
One pot stereoselective synthesis of chiral a,v-diynes from
bromoallenes and organobis(heterocuprates)
Anna Maria Caporusso *, Laura Antonella Aronica, Roberto Geri, Marco Gori
Dipartimento di Chimica e Chimica Industriale, Centro di Studio del CNR per le Macromolecole Stereordinate ed Otticamente Atti6e,
Uni6ersita` degli Studi di Pisa, Via Risorgimento, 35-56126 Pisa, Italy
Received 12 July 2001; accepted 7 November 2001
Dedicated to Professor L. Lardicci on the occasion of his 75th birthday and in recognition of his important contributions
to organometallic chemistry and its applications to organic synthesis
Abstract
Organobis(heterocuprates), 7 and 8, have been prepared reacting in situ 1,4-dilithiobutane and di-Grignard reagents, obtained
from 1,4-dibromobutane and 1,4-dibromobenzene, respectively, with CuSPh and LiCuBr2. The cross-coupling reaction of these
di-cuprate reagents with 3-alkyl and 3,3-dialkyl 1-bromo-1,2-dienes (1) provides a general method for selective synthesis of
1,9-decadiynes (5) and 1,4-bis(2-propynyl)benzenes (6), characterized by two identical chiral centres in the a position to the triple
bonds. The high 1,3-anti stereoselectivity of the coupling process allows us to obtain enantiomerically enriched a,v-diynes 5 and
6 starting from optically active allenic substrates 1. © 2002 Published by Elsevier Science B.V.
Keywords: Copper; 1,4-Butanedicuprates; 1,4-Benzenedicuprates; Coupling reactions; Bromoallenes; Chiral a,v-diynes
1. Introduction
sensitive to steric interactions; an increase of the bulki-
ness of the substituent in the copper species favours the
competitive formation of the allenic derivatives (4)
(Scheme 1) [6]. However, an appropriate selection of
the structure of both the allenic substrate and the
copper reagent provides, with good yields, even quite
hindered terminal alkynes 3 [6].
The possibility of extending this method to the
preparation of chiral acetylenic compounds exhibiting
an even higher synthetic versatility appeared particu-
larly appealing. Recently [7] we emphasized the applica-
tion of our procedure to the preparation of a large
variety of functionalized acetylenic systems by employ-
ing zinc-based cuprates (Knochel reagents [8])
[FGꢀRCu(CN)ZnCl·2LiCl; FG=protected CHO, CO,
OH groups, CHꢁCH2, Me3SiCꢂC, COOEt]. In this
paper we wish to describe the first examples of the
selective synthesis of 1,9-decadiynes (5) and 1,4-bis(2-
propynyl) benzenes (6) (Fig. 1), characterized by two
identical chiral centres, which involves the reaction of
bromoallenes 1 with organobis(heterocuprates) 7 and 8,
respectively, obtained from 1,4-dihalobutanes (Cl, Br)
and 1,4-dibromobenzene, via the corresponding di-
It is well known that the application of acetylene
chemistry is one of the key tools of modern organic
synthesis [1]. The acetylenic moiety provides a conve-
nient unity which may be converted into a variety of
functionalities, and optically active alkynyl compounds
are employed as versatile building blocks for the design
and construction of more complex chiral molecules [2].
In previous papers [3–6] we reported that the cross-
coupling reaction of allenic bromides (1) with the com-
plex bromocuprates (2), obtained from equimolar
amounts of Grignard reagents and LiCuBr2 in THF,
provides one of the most convenient methods for the
synthesis of chiral 1-alkynes (3) with a tertiary or a
quaternary stereogenic centre in the a position to the
triple bond (Scheme 1). The reaction proceeds, in gen-
eral, in a high 1,3-anti stereoselective pattern even if the
regioselectivity of the coupling process appears to be
* Corresponding author. Tel.: +39-050-918-298; fax: +39-050-
918-260.
E-mail address: capored@dcci.unipi.it (A.M. Caporusso).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(01)01438-3

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A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
Scheme 1.
Grignard or dilithium reagents, 9–11. These chiral
a,v-diacetylenic compounds might provide access to a
variety of hitherto inaccessible, novel and theoretically
interesting molecules by transition-metal-mediated
transformations such as cyclizations [9–12], cy-
clodimerizations and cyclotrimerizations [13–16], cocy-
clization with monoalkynes [17], nitriles [18,19], isoni-
triles [20], carbon dioxide [21], carbonyl compounds
[22], and so on.
dimerization processes of the allenic substrate (com-
pounds 15 and 16); compounds 14–16 should probably
be due to halogen–metal exchange reactions. The pro-
gress of the reactions was monitored by GLC analysis
and all products were characterized by analytical and
spectroscopic methods. The results obtained (Table 1,
entries 1–3) showed, however, that the nature of the
copper reagent plays a prominent role in determining
both the reaction rate and the chemoselectivity of the
reaction; in particular, it is noteworthy that with the
thiophenoxydicuprate 7c the substrate conversion was
complete within 1 h at −70 to 20 °C and compound 5a
was obtained as the main product (75%), which was
isolated chemically pure in good yield (Table 1, entry
3). In order to define the usefulness of 7c for the
synthesis of 1,9-decadiynes (5), we reacted this
dicuprate reagent with 3-substituted 1-bromoallenes,
such as (R)(S)-1-bromo-1,2-butadiene (1b), and (R)(S)-
1-bromo-4,4-dimethyl-1,2-pentadiene (1c). The results,
listed in Table 1 (entries 4 and 5), show that 7c affords,
quickly and in very mild experimental conditions, the
diacetylenic compounds 5 with generally high yields,
2. Results and discussion
2.1. 1,9-Decadiynes (5)
Our first experiments were carried out with 1,4-bu-
tanedicuprates 7a–c1 and (R)(S)-1-bromo-3-methyl-
1,2-pentadiene (1a) as model substrate. Reagents 7 were
obtained from 1,4-bis(bromomagnesio)butane (9), and
1,4-dilithiobutane (10) (Scheme 2), according to well
established procedures for the formation of the corre-
sponding monocuprates from organomagnesium [23]
and organolithium precursors [24,25]. In general, the
organodimetallic reagent was added to a solution, or a
suspension, of a copper(I) salt, in diethyl ether or THF,
at the appropriate temperature (−78 °C} −30 °C);
the mixture was stirred for 20–30 min and used imme-
diately. The bis-Grignard 9 was prepared from readily
available 1,4-dibromobutane in THF solution (87%
yield) [26] and the dilithiobutane 10 was obtained (82%
yield) by reaction of 1,4-dichlorobutane with lithium
(1% Na) in diethylether at 0 °C [25] (Scheme 2).
Fig. 1.
When the organocopper reagents (7) were allowed to
react with the bromoallene (1a) (molar ratio 1:2), the
desired 3,8-diethyl-3,8-dimethyl-1,9-decadiyne (5a) was
obtained, but, in general, together with substantial
amounts of several by-products (Scheme 3, Table 1,
entries 1–3). Such products, separated for identification
by bulb-to-bulb distillation and/or column silica gel
chromatography, derive from: (i) a reversal of regiose-
lectivity of the coupling process (compound 12), (ii) a
single coupling reaction (compound 13), (iii) a dimer-
ization of the cuprate reagents followed by two regiose-
lective coupling steps (compound 14), (iv) two possible
1 The reagent structures given in this paper follow the convention
established for the monocuprate analogous and do not necessarily
reflect their structures in solution.
Scheme 2.

A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
111

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A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
Scheme 3.
Scheme 4.
although the steric hindrance at C-3 of the bromoal-
lenic substrate can determine the regioselectivity of the
coupling processes. Pure samples of 3,8-dimethyl-1,9-
decadiyne (5b) (fractional distillation) and 3,8-bis(1,1-
dimethylethyl)-1,9-decadiyne (5c) (silica gel chroma-
tography, hexane as eluant) were so obtained with
excellent to satisfactory yields and characterized with
analytical and spectroscopic data.
To establish the synthetic value of this method for
the preparation of enantiomerically enriched diynes 5,
we checked further the anti stereochemical outcome of
the involved coupling reactions. Thus, samples of (S)-1-
bromo-1,2-butadiene ((S)-1b), prepared in 92% ee ac-
cording to the procedure described by Vermeer and
co-workers [27], were converted, with highly repro-
ducible chemical and optical yields, into pure dextroro-
tatory 5b by treatment with the dicuprate 7c (Scheme
4). The enantiomeric purity and the (S) absolute
configuration of the stereogenic centres of (+)-5b were
evaluated by conversion, via hydroalumination with
diisobutylaluminium hydride (DIBAH), of the diyne
compound into the levorotatory 3,8-dimethyldecane
((−)-17) of known (3R,8R) stereochemistry [28]
(Scheme 4). This result and the very high enantiomeric
purity of recovered (3R,8R)-17 (87% ee; 97.4% of anti
stereoselectivity for the coupling reaction) confirm that
our reaction between bromoallenes 1 and aliphatic het-
erocuprates to give acetylenic products proceeds in an
almost complete anti stereochemical fashion [3–7].
2.2. 1,4-Bis(2-propynyl)benzenes (6)
As previously emphasized, the synthesis of 3-aryl-1-
alkynes (3) via the coupling reaction between 1-bromo-
1,2-dienes and arylcopper reagents proceeds with
satisfactory results only when arylbromocuprates [(Ar-

A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
113
Table 2
Reactions of 1,4-benzenedicuprate (8) with 1-bromo-1,2-dienes
R1R2CꢁCꢁCHBr (1b–d) a
Entry
1
R1
R2
Reaction mixture composition (%) b
6
18
19
20
Scheme 5.
1
2
3
1b
1c
1d
H
H
Me
Me
tBu
tBu
b
c
d
63(38)
67(37)
77(49)
23
17
4
14
12
17
–
4
–
CuBr)MgBr·LiBr], prepared reacting in THF a Grig-
nard reagent, ArMgBr, with LiCuBr2, are employed
(Scheme 1) [3,4,7]. Heterocuprates of different nature,
such as lithium cyanocuprates [RCu(CN)Li] and zinc
cyanocuprates [RCu(CN)ZnCl·2LiCl], which appear
somewhat attractive for preparation of aliphatic
acetylenic compounds, mainly afford allenes 4 when R
is a phenyl or an aryl group [3,4,7] (Scheme 1). Thus,
for the preparation of compounds 6, we attempted to
synthesize, as key intermediate, the 1,4-benzenedibro-
mocuprate (8) starting from 1,4-bis(bromomagnesio)
benzene (11).2
a All reactions were performed by treating the organocopper
reagent with the allenic substrate 1 (molar ratio 1:2) in THF at −70
°C and allowing the mixture to warm to room temperature (12 h).
b Determined by GLC analyses of the reaction mixture after hy-
drolysis; isolated yields by silica gel chromatography (hexane) are
shown in parentheses.
prepared by reduction, in boiling THF, of MgCl2 with
potassium in the presence of KI [31] (Scheme 5).
The di-Grignard 11 was reacted, at 0 °C, with two
equivalents of a well-stirred THF solution of LiCuBr2
and the so obtained bis-cuprate reagent 8 was succes-
sively treated, at −70 °C, with 1-bromo-1,2-dienes
1b–d (Scheme 6). The mixture was allowed to warm to
room temperature and the progress of the reaction
monitored by GLC. In any case, after 12 h, the bro-
moallenic substrate was completely converted leading
to the corresponding 1,4-bis(2-propynyl)benzenes (6b–
d), as main products, together with minor amounts of
the isomeric allenynes (18) and compounds derived
from a single coupling reaction, as the 3-phenyl-1-alky-
According to reported procedures [31,32], the bis-
Grignard reagent was obtained in a quantitative way by
oxidative metalation, in THF at room temperature, of
1,4-dibromobenzene with activated magnesium slurries,
2 Several attempts to selectively obtain 1-alkynes by using in the
coupling reaction with bromoallenes 1 aryl lithium thiophenoxy
cuprates and, in particular, the 1,4-benzene bisthiophenoxycuprate,
obtained from p-phenylen dilithium [29,30], were really unsuccessful
according to the reactivity previously reported for other lithium
heterocuprates [3,4,7].
Scheme 6.

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A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
Scheme 7.
racemization, which is consistent with our previous
data for the formation of (S)-3-phenyl-1-butyne from
the phenyl monocuprate (PhCuBr)MgBr.LiBr [3], can
be related to the mobility, in the reaction conditions, of
the hydrogen atoms (benzylic and also propargylic)
bound to the stereogenic centres. In fact, when we
reacted optically active 3,3-disubstituted allenic bro-
mides 1 with arylbromocuprates for the synthesis of
chiral 3-aryl-1-alkynes characterized by quaternary
stereogenic centres we observed a complete (100%)
stereoselectivity [34].
nes (19) and the substituted allenes (20) (Scheme 6,
Table 2). While compounds 19 and 20 were identified
by comparison of their GLC retention times with those
of authentic samples [3], column silica gel chromatogra-
phy (n-hexane) afforded samples of diynes 6 and alleny-
nes 18 which were characterized by spectroscopic data.
The desired 1,4-bis(2-propynyl)benzenes were recovered
chemically pure with satisfactory yields (40–50%), tak-
ing into account the not optimized purification proce-
dure (Table 2).
These data suggest that the method can be really
useful for the preparation of the aromatic a,v-diynes 6
having also bulky alkyl substituents in the a position to
the triple bonds; interestingly the 6/18 molar ratio
increases when the bulkiness of the above substituents
increases [3]. The 1,3-anti stereoselectivity, widely
proved for the coupling process between heterocuprates
and 1-bromo-1,2-dienes (1) [3–7] (see also Scheme 4),
makes easily accessible the synthesis of compounds 6
enantiomerically enriched too. Thus, chemically pure
levorotatory 1,4-bis[(R)-1-methyl-2-propynyl]benzene
((R)-6b), was obtained in 42% yield starting from a
sample of (S)-1-bromo-1,2-butadiene ((S)-1b) (92% ee)
(Scheme 7). To evaluate the stereoselectivity extent of
the double coupling reaction carried out with the aryl
bis-cuprate, the diyne (R)-6b was converted via hydroa-
lumination with DIBAH into the corresponding 1,4-
bis[(R)-1-methylpropyl]benzene which was related, by
reductive ozonolysis [33], to (R)-2-methyl-1-butanol
((R)-21), of 77% enantiomeric purity (Scheme 7). This
result confirms that once again the coupling process
occurs with high 1,3-anti stereoselectivity (\92%) even
if it shows significant racemization phenomena. This
3. Concluding remarks
The reported results confirm that the procedures
usually employed for the preparation of mono-hetero-
cuprates from organomagnesium and organolithium
precursors can be successfully extended to obtain
organodicuprate reagents, at least as far as aliphatic
and aromatic di-bromocuprates (7a and 8), and di-tio-
phenoxycuprates (7c) are concerned. The cross-cou-
pling reaction of these copper reagents with
3-substituted 1-bromo-1,2-dienes 1 represents a suitable
and general synthetic procedure for chiral 1,9-decadiy-
nes (5), and 1,4-bis(2-propynyl)benzenes (6), which oc-
curs with high regio- and stereoselectivity. As concerns
the meso/dl diastereoselectivity possibly related to the
double cross-coupling reactions, we observed that, in all
cases we employed racemic bromoallenic substrates, we
obtained products 5 and 6 which showed only one
gas-chromatographic signal and 1H- and 13C-NMR
spectra characterized by single resonances (apart from

A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
115
the obvious multiplicity) for non equivalent hydrogens
and carbons (see Section 4). These findings seem to
make the formation of diastereomeric mixtures improb-
able, suggesting a high diastereoselectivity for the dou-
dard methods, redistilled and stored under argon. 1,4-
Dichlorobutane and 1,4-dibromobutane, purchased
from Fluka A.G. Co., Buchs, were distilled before use.
The racemic 1-bromo-1,2-dienes (1a–d), were prepared
and purified as previously described (70–85% yield)
[27,35], starting from the appropriate propargylic alco-
hols. (S)-1-Bromo-1,2-butadiene ((S)-1b) (92% ee), was
obtained from optically active (R)-1-butyn-3-ol [36], by
reacting the corresponding methanesulfonate ester with
LiCuBr2, according to the procedure described by Ver-
meer and co-workers [27]. Commercial (Fluka) 1,4-di-
bromobenzene, lithium bromide, magnesium chloride,
cuprous bromide, cuprous iodide and cuprous cyanide
were used without purification. Cuprous thiophenoxide
was obtained in situ reacting equimolar quantities of
lithium thiophenoxide and cuprous iodide, at 25 °C in
THF–hexane solution [37]. The dilithiobutane 10 was
prepared in Et2O (0.84 M, 82% yield) by reaction of
1,4-dichlorobutane with lithium (ca. 1% sodium con-
tent) [25]. 1,4-Bis(bromomagnesio)butane (9), was pre-
pared (0.34 M, 87% yield) from the corresponding
dibromide by using an excess of magnesium turnings in
anhydrous THF, according to a previously reported
procedure [26].
ble coupling process. However,
a more careful
structural investigation with more sophisticated instru-
ments must be necessary to clarify this point.
As previously emphasized, the given dicuprate struc-
tures do not necessarily reflect the real structure in
solution, however, on the bases of the shown reactivity
with bromoallenes,2 reagents 7a,c and 8 would be struc-
turally very similar to the analogous monocuprates [6].
The anomalous results obtained for the reaction be-
tween 1a and reagent 7b (Table 1, entry 2) can be
attributed to the incomplete transformation of 1,4-
dilithiobutane 10 to the corresponding di-cyanocuprate.
In fact, the dilithium reagent 10, in analogous experi-
mental conditions, reacts with 1a affording, after hy-
drolysis, products mainly from halogen–metal
exchange reactions (bromobutane, 1,4-dibromobutane,
and, in particular, 3-methyl-1,2-pentadiene). Several at-
tempts to optimize the preparation of bis-cyanocuprate
7b modifying experimental conditions, such as reaction
temperature, reaction time, or nature of the reaction
solvent (THF in place of diethyl ether) were
unsuccessful.
4.2. 1,4-Butanedicuprates (7a–c)
4. Experimental
Typically, the organobis(cuprate) (7a) was prepared
by adding, at −50 °C over a 15-min period, 1,4-bis-
(bromomagnesio)butane (15 ml of a 0.34 M THF solu-
tion, 5.1 mmol) to a well-stirred solution of LiCuBr2
(10.2 mmol) obtained in THF (25 ml) from stoichio-
metric amounts of cuprous bromide and lithium bro-
mide [23]. Stirring was continued at −50 °C for 30
min, and the mixture then used immediately.
Cyanocuprate (7b) was prepared by treating a sus-
pension of cuprous cyanide (7.7 mmol) in anhydrous
Et2O (40 ml) at −30 °C with 1,4-dilithiobutane (4.6 ml
of a 0.84 M Et2O solution, 3.9 mmol); the mixture was
stirred at −30 °C for 30 min and the solution then
used [24].
Lithiumtiophenoxy dicuprate (7c) was obtained by
adding, at −78 °C over a 30-min period, 1,4-
dilithiobutane (16.1 ml, 13.5 mmol) to a solution of
cuprous thiophenoxide (27 mmol) in THF (90 ml) [25].
The mixture was allowed to warm to −20 °C over a
20-min period, during which the colour changed from
yellow to red, and then used immediately.
4.1. General
IR spectra were recorded on a Perkin–Elmer FTIR
1710 spectrophotometer as neat films. 1H- and 13C-
NMR spectra were recorded on a Varian Gemini 200
instrument in CDCl3 solution at 200 and 50.29 MHz,
respectively. Chemical shifts were determined relative to
internal Si(CH3)4 (l=0 ppm); coupling constants J are
in Hz. GLC-MS spectra were recorded on a Perkin–
Elmer Q-Mass 910 spectrometer connected with a
Perkin–Elmer 8500 gas chromatograph. GLC analyses
were performed on a Perkin–Elmer 8600 gas chro-
matograph, equipped with a flame ionization detector
(FID), using a SiO2 ‘Wide Bore’ column (DB1, 30
m×0.53 mm, 5 mm) and helium as carrier gas. Optical
rotations were measured with a Perkin–Elmer 142 au-
tomatic polarimeter, using standard cuvettes (l=0.1
and 1 dm). Analytical thin-layer chromatography
(TLC) was performed on aluminium sheets precoated
with silica gel (Merck, Kieselgel 60 F254) and prepara-
tive column chromatography on Fluka Silica gel 60
(230–400 mesh). Microanalyses were carried out by the
Laboratorio di Microanalisi, Facolta` di Farmacia, Uni-
versita` di Pisa, Italy.
4.3. Reaction of 1-bromo-1,2-dienes (1a–c) with 1,4-
butanedicuprates (7a–c). General procedure
All reactions were carried out at least in duplicate. In
a typical experiment, a solution of 1-bromo-1,2-diene
(1) (10–30 mmol), in THF or Et2O (5–20 ml) was
All operations were performed under dry Argon.
Solvents were reagent-grade materials, purified by stan-

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A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
added, at −70 °C during 5–10 min, to the cuprate
reagent (5–15 mmol) prepared by the procedures de-
scribed above. The progress of the reactions was moni-
tored by GLC analysis until they were complete; if
necessary, after stirring was continued at −70 °C for
30 min, the mixture was allowed to warm to 20 °C
(Table 1). The reaction mixture was quenched with
saturated ammonium chloride solution (50 ml), and the
organic materials were extracted with ether (3×50 ml).
The combined extracts were washed with additional
ammonium chloride (2×50 ml) and water (50 ml), then
dried (Na2SO4) and analyzed by GLC and GLC–MS.
Fractional bulb-to-bulb distillation and/or column sil-
ica gel chromatography afforded pure samples of diy-
nes 5 and compounds 12–16 (Scheme 3, Table 1) which
were identified and characterized by spectroscopic and
analytical data.
4.3.5. 3-Methyl-8,9-undecadien-1-yne (12b)
1H-NMR: l 1.18 (3H, d, J=7.0 Hz, CH3), 1.44 (6H,
m, CH2), 1.65 (3H, dd, J=4.9 and 5.2 Hz, ꢁCꢀCH3),
1.99 (2H, m, ꢁCꢀCH2), 2.03 (1H, d, J=2.4 Hz, ꢂCH),
2.42 (1H, m, ꢂCꢀCH), 5.05 (2H, m, CHꢁCꢁCH). 13C-
NMR: l 14.6, 20.9, 25.7, 26.6, 28.7, 28.9, 36.6, 68.0,
85.5, 89.2, 90.1, 204.7. MS: m/z 161 (M+−1), 147(3%),
133(2), 119(7), 105(15), 41(100).
4.3.6. 3-(1,1-dimethylethyl)-11,11-
dimethyl-8,9-dodecadien-1-yne (12c)
1H-NMR: l 0.98 (9H, s, CH3), 1.03 (9H, s, CH3),
1.20–1.40 (6H, m, CH2), 1.96 (2H, m, ꢁCꢀCH2), 2.03
(1H, m, ꢂCꢀCH), 2.05 (1H, d, J=2.1 Hz, ꢂCH), 5.15
(2H, m, CHꢁCꢁCH). MS: m/z 161 (M+−1), 147(3%),
133(2), 119(7), 105(15), 41(100).
The products 5 and 12–16 of the reactions summa-
rized in Table 1 were as follows.
4.3.7. 3-Ethyl-3-methyl-1-heptyne (13a)
1H-NMR: l 0.92 (3H, t, J=7.1 Hz, CH3), 0.97 (3H,
t, J=6.8 Hz, CH3), 1.13 (3H, s, CH3), 1.39 (8H, m,
CH2), 2.05 (1H, s, ꢂCH). MS: m/z 137 (M+−1),
123(5%), 109(56), 96(16), 95(11) 81(100), 67(69).
4.3.1. 3,8-Diethyl-3,8-dimethyl-1,9-decadiyne (5a)
1
IR: w (cm−1) 3309, 2109, 628. H-NMR: l 0.89 (6H,
t, J=7.2 Hz, CH3), 1.06 (6H, s, CH3), 1.36 (12H, m,
CH2), 2.00 (2H, s, ꢂCH). 13C-NMR: l 8.8, 25.1, 25.7,
33.9, 35.0, 40.9, 68.6, 91.0. MS: m/z 217 (M+−1), 203,
189(10%), 161(13), 147(16), 105(45) 81(100). Anal.
Found: C, 88.07; H, 11.93. Calc. for C16H26: C, 87.99;
H, 12.01%.
4.3.8. 3,12-Diethyl-3,12-dimethyl-1,13-tetradecadiyne
(14a)
1H-NMR: l 0.97 (6H, t, J=7.4 Hz, CH3), 1.14 (6H,
s, CH3), 1.2–1.6 (20H, m, CH2), 2.08 (2H, s, ꢂCH).
13C-NMR: l 8.8, 24.6, 25.7, 29.5, 30.0, 33.9, 35.0, 41.0,
68.5, 91.1. MS: m/z 259 (M+−15, 1%), 245(4), 189(2),
175(5), 161(6), 147(10), 135(12), 121(20), 95(48),
81(100), 67(48).
4.3.2. 2,8-Dimethyl-1,9-decadiyne (5b)
1
IR: w (cm−1) 3306, 2112, 631. H-NMR: l 1.18 (6H,
d, J=7.0 Hz, CH3), 1.44 (8H, m, CH2), 2.03 (2H, d,
J=2.4 Hz, ꢂCH), 2.42 (2H, m, CHCꢂ). 13C-NMR: l
20.7, 25.4, 26.8, 36.4, 68.1, 89.1. MS: m/z 147 (M+−
15), 133(1%), 119(7), 105(21), 91(22), 41(100). Anal.
Found: C, 88.95; H, 11.05. Calc. for C12H18: C, 88.81;
H, 11.19%.
4.3.9. 3-Ethyl-3,6-dimethyl-4,5-ottadien-1-yne (15a)
1H-NMR: l 1.02 (6H, t, J=7.0 Hz, CH3), 1.27 (3H,
s, CH3), 1.57 (2H, m, CH2), 1.73 (3H, d, J=3 Hz,
ꢁCꢀCH3), 1.90 (2H, m, ꢁCꢀCH2), 2.12 (1H, s, ꢂCH),
5.13 (1H, m, ꢁCꢁCH). MS: m/z 162 (M+, 19%),
147(77), 133(67), 119(64), 105(98), 91(79), 81(74),
67(41), 41(100).
4.3.3. 3,8-Bis(1,1-dimethylethyl)-1,9-decadiyne (5c)
IR: w (cm−1) 3310, 2109, 630. 1H-NMR: l 0.98 (18H,
s, CH3), 1.21–1.78 (8H, m, CH2), 2.04 (2H, d, J=2.1
Hz, ꢂCH), 2.05 (2H, m, CHCꢂ). 13C-NMR: l 27.4,
28.4, 29.4, 33.1, 43.6, 70.4, 86.6. MS: m/z 231 (M+−
15), 189(1%), 175(2), 161(2), 147(2), 57(100). Anal.
Found: C, 87.85; H, 12.14. Calc. for C18H30: C, 87.72;
H, 12.28%.
4.3.10. 3,8-Dimethyl-3,4,6,7-decatetraene (16a)
1H-NMR: l 0.93 (6H, t, J=7.3 Hz, CH3), 1.64 (6H,
m, CH3), 1.88 (4H, m, CH2), 5.47 (2H, m, ꢁCꢁCH).
13C-NMR: l 12.0, 18.8, 27.0, 90.8, 103.0, 203.2. MS:
m/z 162 (M+, 98%), 147(47), 133(19), 119(40), 105(84),
91(74), 81(100).
4.4. (3S,8S)-3,8-Dimethyl-1,9-decadiyne ((3S,8S)-5b)
4.3.4. 3-Ethyl-3,10-dimethyl-8,9-dodecadien-1-yne
(12a)
According to the general procedure, a solution of
4.0g (30 mmol) of (+)(S)-1-bromo-1,2-butadiene ((S)-
1b), (92% ee) in THF (20 ml) was added during 15 min
at −70 °C to a stirred suspension of lithium tiophe-
noxy dicuprate 7c (15 mmol). After stirring was contin-
ued at −70 °C for 30 min, the reaction mixture was
quenched with saturated NH4Cl solution. Usual work
1H-NMR: l 0.97 (6H, m, CH3), 1.13 (3H, s, CH3),
1.20–1.50 (8H, m, CH2), 1.67 (3H, d, J=3 Hz,
ꢁCꢀCH3), 1.90 (4H, m, ꢁCꢀCH2), 2.05 (1H, s, ꢂCH),
5.06 (1H, m, ꢁCꢁCH). MS: m/z 189 (M+−29, 10%),
161(7), 147(10), 133(14), 119(16), 105(17), 96(96),
81(100).

A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
117
up gave a crude product which was purified by column
chromatography (n-hexane) affording chemically pure
(GLC) (3S,8S)-5b (1.7 g, 70% yield), having h2D5(l=1)
+45.6° and characteristic spectroscopic data fully con-
sistent with those reported for the racemic compound.
A second analogous experiment gave chemically pure
(3S,8S)-5b (1.83 g, 75% yield) having h2D5(l=1) +45.2°.
(1) (10 mmol) in THF (10 ml) was added, at −70 °C
during 5 min, to the bis-cuprate reagent (5 mmol)
prepared by the above described procedure. After stir-
ring was continued at −70 °C for 5 min, the mixture
was allowed to warm to 20 °C and stirred for 12 h. The
progress of the reactions was monitored by GLC analy-
sis (Table 2). The reaction mixture was quenched with
saturated ammonium chloride solution (50 ml), and
worked-up as previously described for experiments with
1,4-butane-dicuprates. Column silica gel chromatogra-
phy (n-hexane) afforded pure samples of diynes 6 and
allenynes 18 which were identified and characterized by
spectroscopic and analytical data. 3-Phenyl-1-alkynes 19
and phenylallenes 20 (Scheme 6, Table 2) were identified
by comparison of their GLC retention times with those
of authentic samples [3].
4.5. (3R,8R)-3,8-Dimethyldecane ((3R,8R)-17)
(3S,8S)-5b (0.94g, 5.8 mmol), h2D5(l=1) +45.6°, was
added at 0 °C to diisobutylaluminium hydride (DIBAH)
(8.5 g, 60 mmol). The mixture was stirred at room
temperature (r.t.) for 24 h and then heated at 80 °C for
12 h. After hydrolysis at 0 °C with water and dilute
sulphoric acid (5%), the organic materials were ex-
tracted with ether and the combined extracts washed
with water and dried (Na2SO4). Fractional distillation
gave chemically pure (3R,8R)-17 (0.81 g, 82% yield):
b.p. 83 °C at 17 mmHg, [h]2D5 −15.57. 1H-NMR: l 0.78
(12H, m, CH3), 0.96–1.36 (14H, m, CH2 and CH).
13C-NMR: l 11.4, 19.2, 27.5, 29.6, 34.5, 36.8. MS: m/z
141 (M+−29, 1%), 113(4), 111(1), 99(2), 85(6), 71(6),
57(63), 56(20), 43(65), 41(100). (Lit. [28], [h]2D5 +17.9
for optically pure (3S,8S)-17.)
The products 6 and 18 of the reactions summarized in
Table 2 were as follows.
4.8.1. 1,4-Bis(1-methyl-2-propynyl)benzene (6b)
1H-NMR: l 1.49 (6H, d, J=6.2 Hz, CH3), 2.24 (2H,
d, J=2.5 Hz, ꢂCH), 3.75 (2H, dq, J=2.5 and 6.2 Hz,
CHPh), 7.35 (4H, s, PhH). 13C-NMR: l 24.1, 31.2, 70.0,
87.1, 127.0, 141.1. MS: m/z 182 (M+, 37%), 173(3),
167(61), 165(40), 152(46), 129(100). Anal. Found: C,
92.43; H, 7.57. Calc. for C14H14: C, 92.25; H, 7.75%.
4.6. 1,4-Bis(bromomagnesio)benzene (11)
In a typical run, freshly cut potassium (1.55 g, 40
mmol), MgCl2 (2.02 g, 21 mmol), KI (1.4 g, 8.4 mmol)
and THF (50 ml) were stirred and heated to reflux for
1 h [29]. To the dark grey mixture, cooled at r.t., was
added 1,4-dibromobenzene (1.25 g, 5.3 mmol) in THF
(5 ml). The resulting mixture was stirred at r.t. for 30
min and then used immediately. GLC analysis of a
NH4Cl solution hydrolysed sample showed a 100% yield
of bis(bromomagnesio)benzene 11, detected as benzene.
MS-GLC analyses of the reaction mixture after
deuterolitic work-up confirmed the presence of the bis-
organometallic reagent.
4.8.2. 1,4-Bis(1-ethynyl-2,2-dimethylpropyl)benzene (6c)
1H-NMR: l 0.96 (18H, s, CH3), 2.23 (2H, d, J=2.5
Hz, ꢂCH), 3.39 (2H, d, J=2.5 Hz, CHCꢂ), 7.22 (4H, s,
PhH). 13C-NMR: l 27.5, 34.9, 49.2, 71.3, 85.5, 128.8,
137.3. MS: m/z 266 (M+, 3%), 251, 210(11), 209(5),
195(3), 179(1), 167(1), 154(8), 115(1), 57(100). Anal.
Found: C, 90.30; H, 9.70. Calc. for C20H26: C, 90.16; H,
9.84%.
4.8.3. 1,4-Bis(1-ethynyl-1,2,2-trimethylpropyl)benzene
(6d)
1
IR: w (cm−1) 3300, 2960, 2880, 900, 780. H-NMR: l
0.96 (18H, s, CH3), 1.65 (6H, s, CH3), 2.23 (2H, s, ꢂCH),
7.43 (4H, s, PhH). 13C-NMR: l 23.3, 26.3, 36.9, 47.0,
71.0, 90.2, 127.2, 140.4. MS: m/z 237 (M+−57, 21%),
207(4), 181(53), 165(16), 152(3), 115(4), 77(3), 57(100).
Anal. Found: C, 89.79; H, 10.20. Calc. for C22H30: C,
89.72; H, 10.28%.
4.7. 1,4-Benzenedicuprate (8)
Typically, the organobis(cuprate) 8 was prepared by
adding, at 0 °C over a 15-min period, a THF solution
of 1,4-bis(bromomagnesio)benzene (5 mmol, 50 ml) to a
well-stirred solution of LiCuBr2 (10 mmol) obtained in
THF (40 ml) from stoichiometric amounts of CuBr
(1.45 g) and LiBr (0.87 g) [23]. Stirring was continued at
0 °C for 30 min, and the mixture then used immediately.
4.8.4. 1-(1-Methyl-2-propynyl)-4-(1,2-butadienyl)-
benzene (18b)
1H-NMR: l 1.45 (3H, d, J=7.0 Hz, CH3), 1.73 (3H,
dd, J=3.2 and 7.0 Hz, ꢁCꢀCH3), 2.12 (1H, d, J=2.8
Hz, ꢂCH), 3.73 (1H, dq, J=2.8 and 7.0 Hz, ꢂCꢀCH),
5.45 (1H, m, ꢁCꢁCH), 6.03 (1H, m, ꢁCꢁCH), 7.10–7.30
(4H, m, PhH). MS: m/z 182 (M+, 56%), 167(100),
129(2), 115(3), 41(70).
4.8. Reaction of 1-bromo-1,2-dienes (1b–d) with
1,4-benzenedicuprate (8). General procedure.
All reactions were carried out at least in duplicate. In
a typical experiment, a solution of 1-bromo-1,2-diene

118
A.M. Caporusso et al. / Journal of Organometallic Chemistry 648 (2002) 109–118
4.8.5. 1-(1-Ethynyl-2,2-dimethylpropyl)-4-
(4,4-dimethyl-1,2-pentadienyl)benzene (18c)
Tecnologica (MURST), Roma (National Project no.
9903558918).
1H-NMR: l 0.97 (9H, s, CH3), 1.12 (9H, s, CH3),
2.22 (1H, d, J=2.5 Hz, ꢂCH), 3.38 (1H, d, J=2.5 Hz,
ꢂCꢀCH), 5.56 (1H, d, J=6.3 Hz, ꢁCꢁCH), 6.16 (1H, d,
J=6.3 Hz, ꢁCꢁCH), 7.10–7.35 (4H, m, PhH). 13C-
NMR: l 27.5, 30.3, 32.8, 34.9, 49.5, 71.3, 85.4, 95.7,
106.8, 125.6, 129.6, 133.8, 138.6, 202.4. MS: m/z 266
(M+,16%), 251(1), 210(20), 209(15), 195(4), 179(3),
165(2), 153(9), 115(3), 57(100).
References
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4.8.6. 1-(1-Ethynyl-1,2,2-trimethylpropyl)-4-(3,4,4-
trimethyl-1,2-pentadienyl)benzene (18d)
1H-NMR: l 0.99 (9H, s, CH3), 1.13 (9H, s, CH3),
1.63 (3H, s, CH3), 1.79 (3H, d, J=2.7 Hz, ꢁCꢀCH3),
2.30 (1H, s, ꢂCH), 6.04 (1H, q, J=2.7 Hz, ꢁCꢁCH),
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47.2, 71.1, 90.1, 93.7, 112.5, 125.0, 128.9, 134.2, 140.6,
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According to the general procedure, a solution of
4.17 g (31.4 mmol) of (+)(S)-1-bromo-1,2-butadiene
((S)-1a), (92% ee) in THF (15 ml) was added during 15
min at −70 °C to 1,4-benzenedicuprate 8 (15.7 mmol).
After stirring was continued at −70 °C for 5 min, the
reaction mixture was heated at r.t. for 12 h and then
quenched with saturated NH4Cl solution. Usual work-
up gave a crude product which was purified by column
chromatography (n-hexane) affording chemically pure
(GLC) (R)-6b (1.2 g, 42% yield), having [h]2D5 −8.80
(c=5.98, CHCl3) and spectroscopic data fully consis-
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A sample of (R)-6b (1.0 g, 5.5 mmol) was added, at
0 °C, to diisobutylaluminium hydride (DIBAH, 60
mmol) and the resulting mixture was heated at 50–80
°C for 24 h. After hydrolysis, the crude product recov-
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methyl-1-butanol ((R)-21), having [h]2D5 +5.10 (c=
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Acknowledgements
This work was in part financially supported by the
Ministero dell’Universita` e della Ricerca Scientifica e
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