Reactions of 1,4-enynes with the system CH2I2-Et 3Al

Article abstract of DOI:10.1007/s11172-011-0347-9

Reactions of alk-1-en-4-ynes with an excess of the system CH ₂I₂-Et₃Al give 1-cyclopropylmethyl-1,2- diethylcyclopropanes. A decrease in the amount of either component of the system to two equivalents results in cyclopropanation of the double bond only. Under such conditions, conjugated enynes yield a complex mixture of products, while conjugated diynes are inert to the system CH₂I₂-Et ₃Al.

Full text of DOI:10.1007/s11172-011-0347-9

Russian Chemical Bulletin, International Edition, Vol. 60, No. 11, pp. 2275—2278, November, 2011
2275
Reactions of 1,4ꢀenynes with the system CH2I2—Et3Al
I. R. Ramazanov,a A. V. Yaroslavova,a U. M. Dzhemilev,a and O. M. Nefedovb
aInstitute of Petrochemistry and Catalysis, Russian Academy of Sciences,
141 prosp. Oktyabrya, 450075 Ufa, Russian Federation.
Fax: +7 (347 2) 84 2750. Eꢀmail: iramazan@inbox.ru
bN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328
Reactions of alkꢀ1ꢀenꢀ4ꢀynes with an excess of the system CH2I2—Et3Al give 1ꢀcycloꢀ
propylmethylꢀ1,2ꢀdiethylcyclopropanes. A decrease in the amount of either component of the
system to two equivalents results in cyclopropanation of the double bond only. Under such
conditions, conjugated enynes yield a complex mixture of products, while conjugated diynes
are inert to the system CH2I2—Et3Al.
Key words: cyclopropanation, 1,3ꢀenynes, 1,3ꢀdiynes, 1,4ꢀenynes, diiodomethane, triethylꢀ
aluminum.
Reactions of unsaturated compounds with the system
CH2I2—Zn/Cu have found wide use in the synthesis of
cyclopropane derivatives.1,2 Recently, we have proposed
the novel system CH2I2—R3Al that favors transformations
of alkynes and allenes into substituted cyclopropanes3,4
and spiropentanes,5 respectively. In the present work, we
further studied the behavior of enynes and diynes in reacꢀ
tions with CH2I2—R3Al.
Preliminary experiments revealed that substituted
vinylacetylenes (2ꢀmethyloctꢀ1ꢀenꢀ3ꢀyne and 1ꢀethynylꢀ
cyclohexene) are completely consumed in reacꢀ
tions with CH2I2 and Et3Al (the molar ratio
[1,3ꢀenyne] : [CH2I2] : [Et3Al] is 1 : 4 : 6) at room temꢀ
perature for 30 h to give a complex, difficultꢀtoꢀidentify
mixture of oligomeric hydrocarbons containing no cycloꢀ
propane derivatives. At the same time, substituted 1,3ꢀdiꢀ
ynes (decaꢀ4,6ꢀdiyne and hexadecaꢀ7,9ꢀdiyne) proved to
be inert to this system of reagents.
In contrast to 1,3ꢀenynes and 1,3ꢀdiynes, reactions of
allylacetylenes (nonꢀ1ꢀenꢀ4ꢀyne and decꢀ1ꢀenꢀ4ꢀyne)
with the system CH2I2—Et3Al under the above conditions
followed by deuterolysis selectively yielded monodeuterꢀ
ated products of the conjectural formulas C15H27D and
C16H29D, respectively (GCꢀMS data, Scheme 1). Based
on known experimental data,3—5 we assumed that the reꢀ
action products are dicyclopropylmethanes 1a and 1´a or
1b and 1´b containing monoꢀ and tetrasubstituted cycloꢀ
propane rings. The 13C NMR spectra of the deuterated
products show two highꢀfield pairs of signals for the groups
CH2D and CH3 of the deuteroethyl and ethyl fragments.
This suggests the simultaneous formation of regioisomers
1a and 1´a or 1b and 1´b in equal proportions, which is
evident from the integral intensities of the signals for the
carbon atoms (C(9) and C(26) for 1a and 1´a and C(10)
and C(28) for 1b and 1´b). At the same time, we ruled out
the formation of cisꢀ and transꢀisomers since the 13C NMR
spectra contain no double signals for the asymmetric
C atoms and their neighbors as observed in the spectrum
of a product obtained from decꢀ5ꢀyne.4 The signals in the
NMR spectra of compounds 1a, 1b, 1´a, and 1´b were
assigned from COSY, HSQC, and HMBC data, as well as
by comparison of their spectra with those of 1,2ꢀdibutylꢀ
1,2ꢀdiethylcyclopropane obtained earlier.4 The presence
of signals at δ 4.32 and 4.49 for the methylene group in the
13C NMR spectrum of a mixture of regioisomers 1a and
1
1´a and a multiplet at δ 0.1—0.4 in their H NMR specꢀ
trum suggests that these compounds contain a monosubꢀ
stituted or 1,1ꢀdisubstituted cyclopropane ring. The APT
and DEPT 135 spectrum exhibits signals for three CH3, one
CH, and eleven CH2 groups and signals for two quaternary
carbon atoms. The HMBC experiment revealed couplings
of the methylene H atoms of the tetrasubstituted cycloꢀ
propane ring with the methylene C atoms of the cyclopropylꢀ
methyl fragment, the C atoms of the αꢀmethylene group
of the butyl substituent, and two quaternary C atoms. Apꢀ
parently, the nonequivalence of the CH2 groups in the
monosubstituted cyclopropane ring results from their diꢀ
asteretopic character. Available spectroscopic data are inꢀ
sufficient for making a conclusion about the stereoconfigꢀ
urations of compounds 1a and 1´a or 1b and 1´b. In conꢀ
nection with this, it is interesting to note the difference of
1,4ꢀenynes from symmetrical dialkylacetylenes (octꢀ4ꢀyne
and decꢀ5ꢀyne), which react with the system Et3Al—CH2I2
to give cisꢀ and transꢀisomers in a ratio of ~1 : 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2233—2236, November, 2011.
1066ꢀ5285/11/6011ꢀ2275 © 2011 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Ramazanov et al.
Scheme 1
R = nꢀC4H9 (a), nꢀC5H11 (b)
Reagents, conditions, and yields: CH2I2 (4 equiv.), Et3Al (6 equiv.), CH2Cl2, ~20 °C, 30 h; 83% (1a + 1´a), 77% (1b + 1´b).
Earlier,4 we have demonstrated that the stereoconfigꢀ
Scheme 2
uration of tetrasubstituted cyclopropane is formed in the
transition state during the rearrangement of 1,1ꢀdisubstiꢀ
tuted cyclopropane and depends on the size of substituꢀ
ents at the triple bond of acetylenes. When the substituꢀ
ents are close in size to each other and to the ethyl group,
one can expect that the rearrangement will be nonstereoꢀ
selective and yield both cisꢀ and transꢀisomers. Otherwise
(as, e.g., in the case of octꢀ2ꢀyne), only one stereoisomer
is produced.3 Therefore, the formation of only one stereoꢀ
isomer from the alkylallylacetylenes studied is indicative
of a large difference in size between the substituents at the
triple bond. Based on this, we assumed that alkylallylacetꢀ
ylenes are initially transformed into alkyl(cyclopropylꢀ
methyl)acetylenes.
Comꢀ
pound
R
R´
Yield
(%)
45
43
49
a
b
c
d
e
nꢀC4H9
nꢀC5H11
nꢀC4H9
Ph
H
H
Me
H
51
58
Ph
Me
Reagents and conditions: CH2I2 (2 equiv.), Et3Al (2 equiv.),
CH2Cl2, ~20 °C, 6 h (R = allyl) and 3 h (R = methallyl).
To identify possible intermediates, we studied the time
dependence of the composition of the reaction products
and found that, indeed, the first step involves selective
cyclopropanation of the double bond in the starting
1,4ꢀenyne and the formation of (cyclopropylmethyl)ꢀ
acetylenes 2a—c (Scheme 2). Therefore, the double bond
is more nucleophilic than the triple bond in a reaction
with a methylenating Al intermediate. Methallylacetylenes
were even more reactive in this reaction than allylacetyꢀ
lenes (the halfꢀconversion time of 2ꢀmethylnonꢀ1ꢀenꢀ4ꢀ
yne is about half that of nonꢀ1ꢀenꢀ4ꢀyne), which is conꢀ
sistent with the concept of the electrophilic nature of the
methylenating Al intermediate. The reactivities were comꢀ
pared using the competitive reaction method. For the ratio
[1,4ꢀenyne] : [CH2I2] : [Et3Al]=1 : 2 : 2, (cyclopropylꢀ
methyl)acetylenes 2a—e were selectively obtained in
43—58% yields. When the reaction time is extended to
6 h, the final reaction mixture contains, along with the
nonconsumed alkylallylacetylene, tetrasubstituted cycloꢀ
propanes 1a and 1a´ or 1b and 1´b in 7—9% yields
(GLC data).
Apparently, the next steps of the reactions of (cycloꢀ
propylmethyl)acetylenes with the system CH2I2—Et3Al
follow the pattern proposed earlier for similar reactions
with monoacetylenes.4
To sum up, we discovered that the system CH2I2—Et3Al
affords cyclopropane derivatives in reactions with
1,4ꢀenynes only, not with 1,3ꢀenynes or 1,3ꢀdiynes.
Experimental
1,3ꢀEnynes (1ꢀethynylcyclohexene and 2ꢀmethyloctꢀ1ꢀenꢀ
3ꢀyne) were prepared by dehydration of appropriate propargylic
alcohols with POCl3 (see Ref. 6). 1,3ꢀDiynes (decaꢀ4,6ꢀdiyne
and hexadecaꢀ7,9ꢀdiyne) were prepared by the CuClꢀcatalyzed
oxidative Glaser coupling of terminal acetylenes under the acꢀ
tion of atmospheric oxygen. 1,4ꢀEnynes (nonꢀ1ꢀenꢀ4ꢀyne, decꢀ
1ꢀenꢀ4ꢀyne, 2ꢀmethylnonꢀ1ꢀenꢀ4ꢀyne, 5ꢀphenylpentꢀ1ꢀenꢀ4ꢀ
yne, and 2ꢀmethylꢀ5ꢀphenylpentꢀ1ꢀenꢀ4ꢀyne) were prepared by
crossꢀcoupling of magnesium acetylenides with allyl bromide or
methallyl bromide in THF in the presence of catalytic amounts
of CuCl.7 Reactions with organoaluminum compounds were carꢀ

Reactions of 1,4ꢀenynes with CH2I2—Et3Al
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2277
ried out under argon. Dichloromethane was distilled over P2O5
before use. Reaction products were analyzed on a Carlo Erba
chromatograph (Ultraꢀ1 glass capillary column (Hewlett Packꢀ
ard), 25 000×0.2 mm, flame ionization detector, programmed
thermostat temperature 50—170 °C, helium as a carrier gas).
Mass spectra were measured on a Finnigan 4021 instrument
(ionization potential 70 eV, ionization chamber temperature
200 °C). Elemental analysis was carried out on a Carlo Erba 1106
J = 19 Hz); 10.97 (t, C(12), J = 19 Hz); 11.20 (C(10)); 11.25
(C(28)); 14.14 (2 C, C(8) and C(24)); 22.79 (2 C, C(7) and
C(23)); 24.43 (2 C, C(3) and C(19)); 24.55 (2 C, C(9) and C(25));
24.72 (2 C, C(11) and C(27)); 26.65 (2 C, C(5) and C(21)); 29.86
(2 C, C(2) and C(18)); 30.89 (2 C, C(1) and C(17)); 32.48 (2 C,
C(6) and C(22)); 35.68 (2 C, C(13) and C(29)). MS, m/z
(Irel (%)): 223 [M]+ (1), 194 [M – C2H5]+ (10), 168 (14), 152 (12).
Synthesis of (cyclopropylmethyl)acetylenes 2a—e (general
procedure). A 50ꢀmL glass reaction vessel immersed in an ice
bath and equipped with a magnetic stirring bar was charged in an
inert atmosphere at 0 °C with CH2Cl2 (15 mL), an enyne
(2 mmol), CH2I2 (0.32 mL, 4 mmol), and Et3Al (4 mmol). The
mixture was stirred for 3 h for methallylacetylenes and for 6 h for
allylacetylenes. Then the reaction mixture was cooled on the ice
bath, diluted with hexane (50 mL), and treated with aqueous
15% HCl. The product from the aqueous layer was extracted
with diethyl ether (3×10 mL). The organic layers were comꢀ
bined, washed with a saturated solution of NaHCO3 and dried
over CaCl2. The solvent was removed in vacuo and the residue
was distilled to give compounds 2a—e as oily products.
1
analyzer. H and 13C NMR spectra were recorded on a Bruker
Avance 400 spectrometer (400 (1H) and 100 MHz (13C)) with
SiMe4 and CDCl3, respectively, as the internal standards. The
yields of the products were determined by gas chromatography
with nꢀundecane and nꢀhexadecane as the internal standards.
Reactions of 1,4ꢀenynes with the system Et3Al—CH2I2 (genꢀ
eral procedure). A 50ꢀmL glass reaction vessel immersed in an
ice bath and equipped with a magnetic stirring bar was charged
in an inert atmosphere at 0 °C with CH2Cl2 (15 mL), an enyne
(2 mmol), CH2I2 (0.64 mL, 8 mmol), and Et3Al (12 mmol). The
mixture was stirred at ~20 °C for 30 h, cooled on the ice bath,
and subjected to deuterolysis with D2O (3 mL). The precipitate
of Al(OD)3 that formed was filtered off. The product from the
aqueous layer was extracted with diethyl ether (3×10 mL). The
organic layers were combined, washed with a saturated solution
of NaHCO3, and dried over CaCl2. The solvent was removed
in vacuo and the residue was distilled to give compounds 1a, 1a´,
1b, and 1b´.
1ꢀCyclopropylheptꢀ2ꢀyne (2a). Yield 45%, b.p. 65—69 °C
(15 Torr). Found (%): C, 88.01; H, 11.75. C10H16. Calculatꢀ
ed (%): C, 88.16; H, 11.84. 1H NMR, δ: 0.1—0.7 (m, 5 H, C(9)H2,
C(10)H2, C(8)H); 0.89 (t, 3 H, C(1)H3, J = 6.7 Hz); 1.1—1.9
(m, 4 H, C(3)H2, C(4)H2); 2.0—2.7 (m, 4 H, C(4, 7)H2).
13C NMR, δ: 3.64 (2 C, C(9), C(10)); 9.63 (C(8)); 13.60 (C(1));
18.46 (C(4)); 21.97 (C(7)); 22.88 (C(2)); 31.29 (C(3)). MS, m/z
(Irel (%)): 136 [M]+ (9), 121 [M – CH3]+ (5), 107 [M – C2H5]+
(16), 94 (22), 93 [M – C3H7]+ (43), 91 (33), 79 (100).
1ꢀCyclopropyloctꢀ2ꢀyne (2b). Yield 43%, b.p. 72—74 °C
(10 Torr). Found (%): C, 87.80; H, 12.14. C11H18. Calculatꢀ
ed (%): C, 87.93; H, 12.07. 1H NMR, δ: 0.1—0.7 (m, 5 H, C(10)H2,
C(11)H2, C(9)H); 0.88 (t, 3 H, C(1)H3, J = 6.8 Hz); 1.1—1.8
(m, 6 H, C(2)H2, C(3)H2, C(4)H2); 2.0—2.4 (m, 4 H, C(5)H2,
C(8)H2). 13C NMR, δ: 3.67 (2 C, C(10), C(11)); 9.60 (C(8));
13.96 (C(1)); 18.45 (C(5)); 22.14 (C(2)); 28.84 (s, C(4)); 31.09
(C(3)). MS, m/z (Irel (%)): 150 [M]+ (1), 135 [M – CH3]+ (2),
121 [M – C2H5]+ (6), 107 [M – C3H7]+ (19), 94 (20), 93 [M –
C4H9]+ (40), 91 (34).
A mixture of 2ꢀbutylꢀ1ꢀcyclopropylmethylꢀ1ꢀdeuteroethylꢀ2ꢀ
ethylcyclopropane (1a) and 2ꢀbutylꢀ1ꢀcyclopropylmethylꢀ2ꢀdeuꢀ
teroethylꢀ1ꢀethylcyclopropane (1´a). Yield 83%, b.p. 68—72 °C
(1 Torr). Found (%): C, 86.21. C15H27D. Calculated (%): C, 86.04.
13C NMR, δ: 4.32 (2 C, C(15) and C(30)); 4.49 (2 C, C(14) and
C(29)); 9.11 (2 C, C(13) and C(28)); 10.81 (t, C(24), J = 19 Hz);
10.95 (t, C(11), J = 19 Hz); 11.13 (C(9)); 11.22 (C(26)); 14.19 (2 C,
C(7) and C(22)); 23.28 (2 C, C(6) and C(21)); 24.48 (2 C, C(3) and
C(18)); 24.61 (2 C, C(10) and C(25)); 24.84 (2 C, C(8) and
C(23)); 29.30 (2 C, C(5) and C(20)); 29.91 (2 C, C(2) and C(17));
30.83 (2 C, C(1) and C(16)); 35.81 (2 C, C(12) and C(27)). MS, m/z
(Irel (%)): 209 [M]+ (1), 180 [M – C2H5]+ (10), 154 (18), 152 (11).
A mixture of 1ꢀcyclopropylmethylꢀ1ꢀdeuteroethylꢀ2ꢀethylꢀ2ꢀ
pentylcyclopropane (1b) and 1ꢀcyclopropylmethylꢀ2ꢀdeuteroethylꢀ
1ꢀethylꢀ2ꢀpentylcyclopropane (1´b). Yield 77%, b.p. 80—84 °C
(1 Torr). Found (%): C, 86.31. C16H29D. Calculated (%):
C, 86.02. 13C NMR, δ: 4.30 (2 C, C(16) and C(31)); 4.45 (2 C,
C(15) and C(32)); 9.09 (2 C, C(14) and C(30)); 10.81 (t, C(26),

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Ramazanov et al.
1ꢀ(Heptꢀ2ꢀynꢀ1ꢀyl)ꢀ1ꢀmethylcyclopropane (2c). Yield 49%,
b.p. 81—84 °C (15 Torr). Found (%): C, 87.68; H, 11.88. C11H18.
Calculated (%): C, 87.93; H, 12.07. 1H NMR, δ: 0.1—0.6 (m, 4 H,
C(9)H2, C(10)H2); 0.91 (s, 3 H, C(1)H3, J = 7.2 Hz); 1.12
(s, 3 H, C(11)H3); 1.3—1.7 (m, 4 H, C(2)H2, C(3)H2); 2.1—2.3
(m, 4 H, C(4)H2, C(7)H2). 13C NMR, δ: 11.91 (2 C, C(9),
C(10)); 13.60 (C(1)); 18.36 (C(4)); 22.94 (C(2)); 23.21 (C(11));
28.49 (C(7)); 31.29 (C(3)).
(1 mmol), 2ꢀmethylnonꢀ1ꢀenꢀ4ꢀyne (1 mmol), nonꢀ1ꢀenꢀ4ꢀyne
(1 mmol), CH2I2 (0.32 mL, 4 mmol), and Et3Al (4 mmol). The
hydrolysis products were analyzed by gas chromatography 10,
15, 30, 60, 90, 120, 180, 240, and 480 min after the addition of
the reagents. The bath temperature was maintained at 0 °C
throughout the experiment.
This work was financially supported by The Ministry
of Science and Education of the Russian Federation
(Grant NShꢀ4105.2010.3) and the Division of Chemistry
and Materials Science of the Russian Academy of Sciences
(Program No. 1).
3ꢀCyclopropylꢀ1ꢀphenylpropꢀ1ꢀyne (2d). Yield 51%, b.p.
61—65 °C (1 Torr). Found (%): C, 92.05; H, 7.83. C12H12. Calꢀ
1
culated (%): C, 92.26; H, 7.74. H NMR, δ: 0.2—0.9 (m, 4 H,
C(1)H2, C(2)H2); 2.55 (s, 2 H, C(4)H2); 7.1—8.0 (m, Ph).
13C NMR, δ: 3.87 (2 C, C(1), C(2)); 9.47 (C(3)); 23.57 (C(4));
127.67 (C(10)); 128.32 (2 C, C(9), C(11)); 131.77 (2 C, C(8),
C(12)). MS, m/z (Irel (%)): 156 [M]+ (50), 155 [M – 1]+ (30),
141 [M – CH3]+ (28), 128 (66), 115 (100).
References
3ꢀ(1ꢀMethylcyclopropyl)ꢀ1ꢀphenylpropꢀ1ꢀyne (2e). Yield
58%, b.p. 77—80 °C (1 Torr). Found (%): C, 91.56; H, 8.13.
C13H14. Calculated (%): C, 91.71; H, 8.29. 1H NMR, δ: 0.3—0.8
(m, 4 H, C(1)H2, C(2)H2); 1.23 (s, 3 H, C(13)H3); 2.46 (s, 2 H,
C(4)H2); 7.1—7.9 (m, Ph). 13C NMR, δ: 12.14 (2 C, C(1), C(2));
14.74 (C(3)); 23.28 (C(13)); 29.14 (C(4)); 127.64 (C(10)); 128.29
(2 C, C(9), C(11)); 131.77 (2 C, C(8), C(12)). MS, m/z (Irel (%)):
170 [M]+ (23), 155 [M – CH3]+ (41), 141 [M – C2H5]+ (39),
128 (66), 115 (100).
Reactions of 1,3ꢀenynes (1ꢀethynylcyclohexene and 2ꢀmethylꢀ
octꢀ1ꢀenꢀ3ꢀyne) and 1,3ꢀdiynes (decaꢀ4,6ꢀdiyne and hexadecaꢀ
7,9ꢀdiyne) with the system Et3Al—CH2I2 were carried out as deꢀ
scribed above for 1,4ꢀenynes.
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Comparison of the relative reactivities of 2ꢀmethylnonꢀ1ꢀenꢀ
4ꢀyne and nonꢀ1ꢀenꢀ4ꢀyne by the competitive reaction method.
A 50ꢀmL glass reaction vessel immersed in an ice bath and
equipped with a magnetic stirring bar was charged in an inert
atmosphere at 0 °C with CH2Cl2 (15 mL), nꢀhexadecane
Received February 18, 2011;
in revised form June 8, 2011