Solvent-free synthesis of 4,4-bis-functionalized-1,6-dienes and 1,6-diynes on the surface of neutral alumina

Article abstract of DOI:10.1016/S0040-4020(01)00896-1

An improved procedure has been developed for the synthesis of structurally varied 4,4-bis-functionalized-1,6-dienes and 1,6-diynes through regioselective alkylation of active methylene compounds with several unsymmetrical allyl bromides and propargyl brom

Full text of DOI:10.1016/S0040-4020(01)00896-1

TETRAHEDRON
Pergamon
Tetrahedron 57=2001) 9011±9016
Solvent-free synthesis of 4,4-bis-functionalized-1,6-dienes
and 1,6-diynes on the surface of neutral alumina
Sanjay Bhar,p Subrata Kumar Chaudhuri, Santi Gopal Sahu and Chiradeep Panja
Department of Chemistry, Organic Chemistry Section, Faculty of Science, Jadavpur University, Kolkata 700032, India
Dedicated to Professor U. R. Ghatak on the occasion of his 70th birthday
Received 2 March 2001; revised 6 August 2001; accepted 30 August 2001
AbstractÐAn improved procedure has been developed for the synthesis of structurally varied 4,4-bis-functionalized-1,6-dienes and 1,6-
diynes through regioselective alkylation of active methylene compounds with several unsymmetrical allyl bromides and propargyl bromide
on the surface of neutral alumina impregnated with sodium ethoxide or potassium tert-butoxide in the absence of any solvent under
environmentally benign conditions. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
their homogeneous counterparts are ease of set-up and
work-up, mild experimental conditions, rapid reactions
and gain in yield and/or selectivity. Quite a few years ago,
reports of surface-mediated Michael reactions and highly
selective C-alkylation of 1,3-dicarbonyl compounds have
come out in the literature.7 As a part of our endeavour to
develop highly selective, operationally simple, economic-
ally viable and environmentally benign methodology for
important synthetic transformations8 we report herein a
regioselective diallylation and dipropargylation of active
methylene compounds in dry medium on the surface of
neutral alumina impregnated with sodium or potassium
alkoxide to generate functionally varied 4,4-disubstituted
1,6-dienes and 1,6-diynes.
4,4-bis-Functionalized-1,6-dienes and 1,6-diynes ®nd
immense applications for the construction of structurally
varied carbocycles via ring closing metathesis,1 Pauson±
Khand reaction2 and Pd-catalyzed cyclization/hydrosilyl-
ation3 protocols. The said compounds are commonly
prepared by diallylation of active methylene compounds
with allyl halides and propargyl halides under basic con-
ditions which are often complicated because of concomitant
O-alkylation, Claisen retrogression of 1,3-dicarbonyl
compounds and allylic rearrangement of propargyl and
unsymmetrical allyl halides.4 Although very recently,
during the synthesis of angularly fused tricyclic systems
via tandem ring closing metathesis reaction, DBU-mediated
zero-valent palladium-catalyzed allylation of 1,3-dicarbo-
nyl compounds has been reported,1d there is still a need
for a simple, cost-effective and more general method for
the regioselective C-dialkylation of active methylene
compounds with propargyl and unsymmetrical allyl halides.
The art of performing ef®cient chemical transformation in a
single operation by reusable catalyst avoiding toxic and
costly reagents, large amounts of solvents and expensive
puri®cation techniques, represents a fundamental target of
the modern organic synthesis.5 Reactions using reagents
and/or reactants on insoluble inorganic support in absence
of any solvent have stimulated considerable interest among
synthetic chemists worldwide.6 Advantages frequently
claimed in favour of supported reagents compared with
Keywords: regiocontrol; solid-phase synthesis; supported reagents; dienes
and diynes.
p
Corresponding author. Fax: 191-033-473-1484;
e-mail: sanjaybharin@yahoo.com
Scheme 1.
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020=01)00896-1

9012
S. Bhar et al. / Tetrahedron 57 )2001) 9011±9016
Table 1. Monoalkylation of active methylene compounds with unsymmetrical allyl bromides and propargyl bromide
Entry no.
Active methylene compound =1)
E2
Alkyl halide 2/3
Time =h)
Yield =%) of 4/6
Yield =%)a of 5/7
E1
a
1
2
3
4
MeCO
CO2Et
MeCO
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
1
1
2
2
7
0
5
±
±
±
±
68a
b
7
67a
b
5
4
1
7
8
7
±
±
a
6
MeCO
CO2Et
7
a
% by 1H NMR, remainder starting material.
Isolated pure product.
b
2. Results and discussion
As shown in Table 1, different 1,3-dicarbonyl compounds
=1) underwent highly regioselective mono-C-alkylation
with structurally varied unsymmetrical allyl bromides =2)
and propargyl bromide =3) at room temperature in good
yield and purity within a reasonably short period of time,
even when both the substrate and the allyl halide are
sterically congested =Table 1, entry 5). The most important
At the outset, to check the feasibility of the surface-
mediated alkylation technique with propargyl and unsym-
metrically substituted allyl bromides, the following mono-
alkylation study was undertaken =Scheme 1), results of
which has been furnished in Table 1.
Scheme 2.

S. Bhar et al. / Tetrahedron 57 )2001) 9011±9016
Table 2. Diallylation and dipropargylation of active methylene compounds
9013
Entry No.
E1
E2
Alkyl halide
Time =h)
Yield =%)a
1
2
MeCO
MeCO
CO2Et
CO2Et
1
3
81
80
3b
4
MeCO
MeCO
CN
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
2
1.5
1
69
85
80
7
5
6
CN
3
8
6
7b
8
CN
2
80
84
CN
1
9
CO2Et
CO2Et
CO2Et
CO2Et
1.5
3
79
7
10
11b
12
CO2Et
CO2Et
CO2Et
CO2Et
3.5
2.5
82
85
13
14
MeCO
MeCO
MeCO
MeCO
2
3
80
7
5
8
1
15b
16
a
MeCO
MeCO
MeCO
MeCO
2
1
7
7
1
Yield refers to isolated product puri®ed by column chromatography or short-path distillation and fully characterized by IR and H NMR spectroscopy.
KOBut was used instead of NaOEt to obtain better results.
b
feature of the present method seems to be the negligible
obtained using potassium tert-butoxide as base instead of
sodium ethoxide for methyl g-bromocrotonate, presumably
due to concomitant transesteri®cation and nucleophilic
addition by ethoxide, which is not very pronounced with
the relatively less nucleophilic base tert-butoxide. The
products are puri®ed by column chromatography over
neutral alumina or short path distillation. 1,6-Diynes having
various functionalities at C4-position prepared by this
method ®nd immense applications in various useful cyclo-
polymerisation reactions.10 This methodology can therefore
be applied for the synthesis of various 1,6-dienes and 1,6-
diynes having requisite substituents at 1- and 6-position
with the potential for constructing important substituted
carbocycles and spiro compounds related to important
natural product skeletons by suitable modi®cation and
elaboration of various functionalities located at 4-position.
formation of any product =maximum 2%) =5 or 7) arising
from allylic rearrangement in each case. Use of NaOEt in
place of NaOBut or KOBut led to the formation of con-
siderable amount of di-C-alkylated products along with
monoalkylated ones.
Inspired by the above results, attempts were made to synthe-
size a series of structurally different 4,4-bis-functionalized
1,6-dienes and 1,6-diynes by base-promoted surface-
mediated regioselective dialkylation of active methylene
compounds =1a±1d) with unsymmetrically substituted
allyl bromides =2a±2c) and propargyl bromide =3) on the
surface of neutral alumina impregnated with NaOEt or
KOBut in absence of any solvent, as shown in Scheme 2.
The results are shown in Table 2.
As evident from Table 2, several substituted 1,6-dienes =8a±
8l) and 1,6-diynes =9a±9d) have been synthesized by the
present method in good yield, high purity and with excellent
selectivity within the reasonable period of time using easily
available non-toxic materials. No Claisen retrogression of
the products =a very common side reaction9 for non-eno-
lizable 1,3-diketones, b-ketoesters and 1,3-diesters) was
observed in spite of the presence of excess nucleophilic
base =ethoxide). Negligible occurrence of allylic rearrange-
ment in the propargyl and allyl moieties =not more than 2%
as evident from 1H NMR studies) is manifested in the high
regioselectivity of the said process. The stereochemistry of
the double bond in the halide has also been found unaltered
in the product =as evident from the coupling constants of the
ole®nic protons in 1H NMR spectra). Better yields are
The present surface-mediated reactions in solvent-free
medium have been found to be more effective and ef®cient
than those in solution in terms of rate, yield and purity. The
said reactions are slower in solution than in dry state adsorp-
tion condition =DSAC). Reaction between ethyl aceto-
acetate and cinnamyl bromide in anhydrous dichloro-
methane in the presence of neutral alumina impregnated
with sodium ethoxide for 3 h led to the formation of a
mixture of 57% mono- and 43% dialkylated product =as
1
indicated by H NMR studies), whereas the same reaction
in DSAC leads to exclusive dialkylation =entry 2 in Table 2).
Ethyl acetoacetate reacts with propargyl bromide in
presence of sodium ethoxide in ethanol in absence of
alumina, but the product is obtained in much lower yield
=,55%) and considerable amount of side products are

9014
S. Bhar et al. / Tetrahedron 57 )2001) 9011±9016
Scheme 3.
formed, which decreases the purity of the alkylated product
to great extent. Sodium ethoxide in ethanol has been found
to be detrimental; with cinnamyl bromide and methyl
g-bromocrotonate, extensive polymerization of the double
bond occurs with very little alkylation of active methylene
compound. Clearly the basicity of ethoxide when impreg-
nated with alumina is so attenuated that it is suf®cient to
deprotonate the active methylenes but insuf®cient to
promote base-catalyzed polymerization of allyl halides
making the DSAC-methods more attractive than the
conventional ones. Stirring for 1 h after addition of crotyl
bromide =1.1 equiv.) to ethyl acetoacetate =1 equiv.)
adsorbed on alumina impregnated with NaOEt =3 equiv.)
followed by the addition of propargyl bromide =1.2 equiv.)
in the same pot and stirring for further 2 h led to the forma-
tion of dicrotyl =8a) and dipropargyl =9a) adducts, no trace
of crotyl-propargyl product was detected =Scheme 3).
=b) no allylic rearrangement of the unsymmetrical allyl
bromides and propargyl bromide;
=c) preservation of stereochemistry of the ole®nic
linkages;
=d) decreased polymerization of certain allyl halides,
especially cinnamyl bromide and methyl g-bromocroto-
nate under basic condition;
=e) reactions in DSAC are faster than in solution;
=f) good yield of the products obtained under relatively
mild conditions by an economically viable and environ-
mentally friendly method.
Further investigations on the mechanistic aspects of this
reaction and its applications in organic synthesis are
currently underway.
4. Experimental
General: 1H NMR spectra were recorded at 60 MHz on EM
360 spectrometer of Varian Associates in CCl4 solutions and
at 300 MHz on Bruker-300 spectrometer in CDCl3 solutions
using Me4Si as internal standard. IR spectra were recorded
on Perkin Elmer 298 spectrometer in CHCl3 solution.
Elemental analyses were performed on Perkin Elmer C,
H, N Autoanalyser. Alumina, supplied by SRL, India
=Aluminium oxide, neutral, Brockmann activity, grade 1
for column chromatography) was used in all the reactions.
The allyl and propargyl halides were prepared following
standard procedures. All the chemicals were distilled before
use.
3. Conclusions
The present surface-mediated solid-phase procedure on the
surface of neutral alumina provides an ef®cient method-
ology for the synthesis of a variety of 4,4-bis-functionalized
1,6-disubstituted dienes and 1,6-diynes from easily acces-
sible starting materials. The notable advantages of the
present procedure include =a) good yield =70±85%), =b)
reasonably rapid reactions =1±3 h), =c) mild reaction con-
ditions, =d) ease of set-up and work-up, =e) use of relatively
non-toxic reagents and solvents and =f) general applicability
accommodating a variety of substitution patterns. Alumina
recovered after the reaction can be recycled after washing
with methanol and activation with little variation of yield.
Therefore, this allylation approach has set out to minimize
the use of offensive materials and maximize the use of
renewable resources. For these reasons it can be considered
as a relatively green technology.
4.1. General procedure for the solvent-free synthesis of
4,4-bis-functionalized 1,6-dienes *8a±8l) and 1,6-diynes
*9a±9d)
To a solution of sodium ethoxide in dry ethanol =or potas-
sium tert-butoxide in dry tert-butanol as the case may be)
=15 mmol), neutral alumina =15 times the weight of
the active methylene sustrate, activated by heating at
1808C under vacuum for 2 h followed by cooling and
storage under argon) was added with stirring followed by
Essential features of this methodology are
=a) no O-allylation and Claisen retrogression of non-
enolizable 1,3-dicarbonyl compounds;

S. Bhar et al. / Tetrahedron 57 )2001) 9011±9016
9015
evaporation of the solvent under reduced pressure to obtain
an easy ¯owing powder. The substrate =5 mmol) was added
dropwise to the supported reagent under nitrogen with
vigorous stirring. Stirring was continued for 10 min at
room temperature. Then the reaction mixture was cooled
in ice and the alkyl halide =11 mmol) was added dropwise
under stirring condition. The reaction mixture was then
allowed to attain room temperature and left at room
temperature with intermittent stirring =to ensure complete
mixing) till completion of the reaction =monitored with
TLC). The product was extracted from the solid mass by
®ltration chromatography over a short plug of neutral
alumina using dichloromethane as solvent. Evaporation of
solvent under reduced pressure furnished the crude product,
which was further puri®ed by column chromatography over
neutral alumina or short path distillation.
=60 MHz, CCl4): d 1.18 =3H, t, Jˆ7Hz, ±OCH 2CH3); 1.28
=6H, d, Jˆ4 Hz, vCHCH3); 2.32 =4H, d, Jˆ5 Hz,
±CH2CHv); 4.12 =2H, q, Jˆ7Hz, ±OC H2CH3); 4.99±
5.87=4H, m, ±C HvCH±).
4.1.5. Ethyl 2-cyano-2-*3-phenylprop-2-enyl)-5-phenyl-
pent-4-ene-1-oate *8e). Colourless viscous oil; puri®ed by
column chromatography on neutral alumina =7% EtOAc/
petroleum ether), yield 78%; IR: 1730 cm21 =s), 2240
1
cm21 =vw); H-NMR =60 MHz, CCl4): d 1.49 =3H, t, Jˆ
7Hz, ±OCH 2CH3); 3.02 =4H, d, Jˆ7Hz, ±C H2CHv);
4.49 =2H, q, Jˆ7Hz, ±OC H2CH3); 6.20±6.73 =2H, m,
±CHvCHPh); 6.88 =2H, d, Jˆ16 Hz; ±CHvCHPh); 7.57
=10H, br.s, Aromatic ± H). Anal. Found C, 80.29; H, 6.39;
N, 4.23. C23H23O2N requires C, 80.01; H, 6.66; N, 4.05.
4.1.6. Dimethyl 5-cyano-5-ethoxycarbonylnona-2,7-di-
ene-1,9-dioate *8f). Colourlerss oil; distilled at 1608C at
0.03 mm of Hg, yield 80%; IR: 1715 cm21 =s), 1740 cm21
=s); 2240 cm21 =vw); 1H NMR =300 MHz, CDCl3): d
1.32 =3H, t, Jˆ7Hz; ±OCH 2CH3); 2.58±2.95 =4H, m,
±CH2CHv); 3.75 =6H, s, ±COOCH3); 4.30 =2H, q,
Jˆ7Hz, ±OC H2CH3); 6.00 =2H, d, Jˆ15.5 Hz,
±CHvCHCOOCH3); 6.86 =2H, td, J1ˆ15.5 Hz, J2ˆ
7.6 Hz, ±CHvCHCOOCH3) Anal. Found C, 57.98; H,
5.90; N, 4.28. C15H19O6N requires C, 58.25; H, 6.15; N,
4.53.
For solid alkyl halide =cinnamyl bromide), ethereal solution
was added to the reaction mixture at 08C followed by
evaporation of the solvent under reduced pressure and left
at room temperature till the completion of the reaction.
Reactions on a gram scale also furnished analogously
good yield.
The products were easily identi®ed by their spectral =IR
1
and H NMR) data which are presented here for ready
reference.
4.1.1. Ethyl 2,2-bis-*but-2-enyl)-3-oxo-butanoate *8a).1a
Colourless oil; puri®ed by column chromatography on
neutral alumina =3% EtOAc/petroleum ether); yield 81%;
IR: 1710 cm21 =s), 1740 cm21 =s); 1H NMR =60 MHz,
CCl4); d 1.20 =3H, t, Jˆ7Hz, ±OCH 2CH3); 1.58 =6H, d,
Jˆ6 Hz, CH3CHv); 1.95=3H, s, CH3CO±);2.36 =4H, d,
Jˆ7Hz, ±C H2CHv); 4.06 =2H, q, Jˆ7Hz, ±OC H2CH3);
4.77±5.67 =4H, m., ±CHvCH±).
4.1.7. Diethyl 2,2-bis-*but-2-enyl)-propane-1,3-dioate
*8g).1a,c Colourless oil; puri®ed by column chromatography
on neutral alumina =3% EtOAc/petroleum ether), yield 79%;
IR: 1725 cm21 =s); 1H-NMR =60 MHz, CCl4): d 1.23 =6H, t,
Jˆ7Hz, ±OCH 2CH3); 1.64 =6H, d, Jˆ6 Hz, CH3CHv)
2.43 =4H, d, Jˆ6 Hz, ±CH2CHv); 4.12 =4H, q, Jˆ7Hz;
±OCH2CH3); 4.93±5.69 =4H, m, ±CHvCH±).
4.1.8. Diethyl 2,2-bis-*3-phenylprop-2-enyl)-propane-
1,3-dioate *8h). Colourless oil; puri®ed by column chroma-
tography on neutral alumina =5% EtOAc/petroleum ether),
yield 76%; IR: 1725 cm21 =s); 1H NMR =60 MHz, CCl4): d
1.40 =6H, t, Jˆ7Hz, ±OCH 2CH3); 2.96 =4H, d, Jˆ7Hz;
±CH2CHv); 4.36 =4H, q, Jˆ7Hz, ±OC H2CH3); 5.97±
6.53 =2H, m, ±CHvCHPh); 6.70 =2H, d, Jˆ16 Hz,
±CHvCHPh); 7.47 =10H, br.s, Aromatic-H). Anal. Found
C, 76.34; H, 7.27. C25H28O4 requires C, 76.53; H, 7.14.
4.1.2. Ethyl 3-oxo-2,2-bis-*-3-phenylprop-2-enyl)-butano-
ate *8b). Colourless highly viscous oil; puri®ed by column
chromatography on neutral alumina =3% EtOAc/petroleum
1
ether); yield 80%; IR: 1710 cm21 =s), 1740 cm21 =s); H
NMR =60 MHz, CCl4);
d
1.16 =3H, t, Jˆ7Hz,
±OCH2CH3); 2.06 =3H, s, CH3CO±); 2.71=4H, d, Jˆ6 Hz,
CH2CHv); 4.15=2H, q, Jˆ7Hz, ±OC H2CH3); 5.93 =2H, td,
J1ˆ16 Hz, J2ˆ6 Hz, ±CHvCHPh); 6.39 =2H, d, Jˆ16 Hz,
±CHvCHPh); 7.26 =10H, br. s., Aromatic-H); Anal. Found
C, 79.34; H, 7.25. C24H26O3 requires C, 79.55; H, 7.18.
4.1.9. Dimethyl 5,5-bis-*ethoxycarbonyl)-nonane-2,7-
diene-1,9-dioate *8i). Colourless oil; distilled at 1608C at
0.06 mm of Hg, yield 82%; IR, 1715 cm21=s),
4.1.3. Dimethyl 5-ketomethyl-5-ethoxycarbonylnona-
2,7-diene-1,9-dioate *8c). Colourless oil; distilled at
1558C at 0.04 mm of Hg, yield 69%; IR: 1710 cm21 =s),
1
1740 cm21=s); H NMR =300 MHz, CDCl3), d 1.26 =6H, t,
Jˆ7Hz, ±OCH 2CH3); 2.78 =4H, d, Jˆ7.5 Hz, ±CH2CHv);
3.73 =6H, s, COOCH3); 4.22 =4H, q, Jˆ7Hz, ±OC H2CH3);
5.89 =2H, d, Jˆ15.5 Hz, ±CHvCHCOOCH3); 6.78 =2H,
td J1ˆ15.5 Hz, J2ˆ7.5 Hz, ±CH±CHCOOCH3) Anal.
Found C, 57.42; H, 6.79. C17H24O8 requires C, 57.30; H
6.74.
1
1740 cm21 =s) H NMR =60 MHz, CCl4): d 1.29 =3H, t,
Jˆ7Hz, ±OCH 2CH3); 2.16 =3H, s, CH3CO); 2.73 =4H,
d, Jˆ8 Hz, ±CH2CHv); 3.66 =6H, s, ±COOCH3); 4.28
=2H, q, Jˆ7Hz, ±OC H2CH3); 5.86 =2H, d, Jˆ16 Hz,
vCHCOOCH3); 6.17±6.99 =2H, m, ±CHvCHCOOCH3)
Anal. Found C, 58.61; H, 6.98. C16H22O7 requires C,
58.89; H, 6.75.
4.1.10. 3,3-bis-*But-2-enyl)-pentane-2,4-dione*8j).1b Colour-
less oil; puri®ed by column chromatography on neutral
alumina =5% EtOAc/petroleum ether) yield 80%; IR:
4.1.4. Ethyl 2-cyano-2-*but-2-enyl)-hex-4-ene-1-oate
*8d).1b Colourless viscous oil; puri®ed by column chroma-
tography on neutral alumina =7% EtOAc/petroleum ether),
1
1700 cm21=s); H NMR =60 MHz, CCl4): d 1.68 =6H, d,
Jˆ6 Hz, ±CH3); 2.03 =6H, s, CH3CO±), 2.53 =4H, d, Jˆ
1
yield 80%; IR: 1730 cm21 =s), 2240 cm21 =vw); H NMR
8 Hz, ±CH2); 4.87±5.87 =4H, m, ±CHvCH±).

9016
S. Bhar et al. / Tetrahedron 57 )2001) 9011±9016
4.1.11. 3,3-bis-*3-Phenylprop-2-enyl)-pentane-2,4-dione
*8k). Colourless highly viscous oil; distilled at 1658C at
=2H, t, Jˆ2.5 Hz, Acetylenic ±CH); 2.99 =4H, d, Jˆ2.5 Hz,
±CH2±).
1
0.03 mm of Hg, yield 75%; IR: 1710 cm21=s); H NMR
=60 MHz, CCl4): d 2.17=6H, s, CH3CO±); 2.83 =4H, d,
Jˆ8 Hz, ±CH2CHv); 5.63±6.37=2H, m, ±C HvCHPh);
6.49 =2H, d, Jˆ16 Hz, ±CHvCHPh); 7.27 =10H, br. s,
Aromatic-H). Anal. Found C, 82.91; H, 7.34. C23H24O2
requires C, 83.13; H, 7.23.
Acknowledgements
The authors express profound gratitude to Professor B. C.
Ranu and Mr N. Dutta of IACS and Professor R. N.
Banerjee of J.U. for helpful discussions, valuable advice
and instrumental assistance during the course of this investi-
gation. Financial support from DSA-UGC, UGC-minor
research grant =unassigned) and CSIR, New Delhi =Sanction
no.01=1673)/00/EMR-II) are also highly acknowledged.
4.1.12. Dimethyl 5,5-bis-*ketomethyl)-nonane-2,7-diene-
1,9-dioate *8l). White crystalline solid, crystallised from
dichloromethane/petroleum ether, yield 78%, mp 1268C;
IR: 1700 cm21=s), 1715 cm21=s); 1H NMR =300 MHz,
CDCl3): d 2.14 =6H, s, CH3CO±); 2.81 =4H, d, Jˆ7.5 Hz,
±CH2CHv); 3.73 =6H, s, ±COOCH3); 5.91 =2H, d, Jˆ
15.5 Hz, ±CHvCHCOOCH3); 6.61 =2H, td, J1ˆ15.5 Hz,
J2ˆ7.5 Hz, ±CHvCHCOOCH3). Anal. Found C, 60.88;
H, 6.81. C15H20O6 requires C, 60.81; H, 6.76.
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*9a).10a Colourless oil, puri®ed by column chromatography
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85%; IR: 1710 cm21=s), 1740 cm21=s), 2110 cm21=vw),
1
3300 cm21=s); H NMR =60 MHz, CCl4): d 1.27=3H, t,
Jˆ7Hz, ±OCH 2CH3); 1.92 =2H, t, Jˆ3 Hz, Acetylenic
CH); 2.12 =3H, s, CH3CO±); 2.84 =4H, d, Jˆ3 Hz, ±CH2±);
4.17=2H, q, Jˆ7Hz, ±OC H2CH3).
3. =a) Widenhoefer, R. A.; Perch, N. S. Org. Lett. 1999, 1, 1103±
1106. =b) Pei, T.; Widenhoefer, R. A. Org. Lett. 2000, 2,
1469±1472.
4.1.14. Ethyl 2-cyano-2-*prop-2-ynyl)-pent-4-yne-1-oate
*9b).10a Colourless oil, puri®ed by column chromatography
on neutral alumina =3% EtOAc/petroleum ether) yield 84%;
IR: 1735 cm21=s), 2100 cm21=vw); 2240 cm21 =vw);
4. March, J. Advanced Organic Chemistry, 4th ed., McGraw-
Hill; New York, 1999.
5. Mizuno, N.; Misono, M. Chem. Rev. 1998, 98, 199.
6. =a) Posner, G. H. Angew. Chem. Int. Ed. Engl. 1978, 17, 487±
496. =b) McKillop, A.; Young, D. W. Synthesis 1979, 401±
422. =c) Cornelis, A.; Laszlo, P. Synthesis 1985, 909±918.
=d) Laszlo, P. Science 1987, 235, 1473±1477. =e) Ranu,
B. C.; Bhar, S.; Chakrabarty, R.; Das, A. R.; Saha, M.; Sarkar,
A.; Chakraborty, R.; Sarkar, D. C. J. Indian Inst. Sci. 1994,
15±33 special issue.
1
3300 cm21=s) H NMR =60 MHz, CCl4): d 1.43 =3H, t,
Jˆ7Hz, ±OCH 2CH3); 2.33 =2H, t, Jˆ3 Hz, Acetylenic
±CH); 2.97=4H, d, Jˆ3 Hz, ±CH2±); 4.42 =2H, q, Jˆ
7Hz, ±OC H2CH3).
4.1.15. Ethyl 2,2-bis-*prop-2-ynyl)-propane-1,3-dioate
*9c).1a,10a,c Colourless oil, puri®ed by column chroma-
tography on neutral alumina =3% EtOAc/petroleum ether)
yield 85%; IR: 1725 cm21=s), 2110 cm21=vw), 3300
cm21=s); 1H NMR =300 MHz, CDCl3): d 1.26 =6H, t,
Jˆ7Hz, ±OCH 2CH3); 2.03 =2H, t, Jˆ2.6 Hz, Acetylenic
±CH); 2.99 =4H, d, Jˆ2.6 Hz, ±CH2±); 4.23 =4H, q, Jˆ
7Hz, ±OC H2OH3).
7. =a) Ranu, B. C.; Bhar, S. Tetrahedron 1992, 48, 1327±1332.
=b) Ranu, B. C.; Bhar, S.; Chakraborty, R. J. Org. Chem. 1992,
57, 7349±7352. =c) Ranu, B. C.; Bhar, S. J. Chem. Soc. Perkin
Trans. 1 1992, 365±368.
8. Bhar, S.; Panja, C. Green Chem. 1999, 1, 253±255.
9. House, H. O. Modern Synthetic Reactions; Benjamin/
Cummings; Reading, MA, 1972, pp 517±520.
4.1.16. 3,3-bis-*Prop-2-ynyl)-pentane-2,4-dione *9d).1a,10a
Colourless oil, puri®ed by column chromatography on
neutral alumina =5% EtOAc/petroleum ether) yield 71%;
IR: 1700 cm21=s), 2100 cm21=vw), 3300 cm21=s); 1H
NMR =300 MHz, CDCl3), d 2.18 =6H, s, CH3CO±); 2.56
10. =a) Jin, S. H.; Kim, S. H.; Cho, H. N.; Choi, S. K. Macro-
molecules 1991, 24, 6050±6052. =b) Koo, K. M.; Han, S. H.;
Kang, Y. S.; Kim, U. Y.; Choi, S. K. Macromolecules 1993,
26, 2485±2488. =c) Schrock, R. R. Pure Appl. Chem. 1994, 66,
1447±1454.