(E,E)-1,2,3,4-tetracyclopropylbuta-1,3-diene: Synthesis and some of its properties

Article abstract of DOI:10.1002/ejoc.201201054

(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene (3) and (Z,Z)-1,4-diodo-1,2,3, 4-tetracyclopropylbuta-1,3-diene (4) were prepared from dicyclopropylacetylene via an intermediate 2,3,4,5-tetracyclopropyltitanacyclopentadiene (2) in 91 and 77 % yield, respectively. In the crystal, 3 adopts a conformation with an almost coplanar (I = 163°) 1,3-diene core, with the inner vinylcyclopropane units in an orthogonal and the outer vinylcyclopropane moieties in an s-trans orientation. This diene, like 2,3-cyclopropylbuta-1,3-diene (5), undergoes facile concerted [4+2] cycloadditions at 130 °C with dimethyl acetylenedicarboxylate as well as N-phenylmaleimide and at 0°C with N-phenyltriazolinedione. An X-ray crystal structure analysis of 2,3-dicyclopropylbuta-1,3-diene (5) also reveals a coplanar inner core with the vinylcyclopropane units in essentially orthogonal (I_av = 89.3°) orientation. Differential scanning calorimetry (DSC) measurements indicate that 3 undergoes significant internal reorganization on going from the liquid to the crystalline phase, and a gauche conformer of 3 may well be favored over the s-trans conformer in the liquid. Copyright

Full text of DOI:10.1002/ejoc.201201054

FULL PAPER
DOI: 10.1002/ejoc.201201054
(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene: Synthesis and Some of Its
Properties[‡]
Armin de Meijere,*[a] Stefan Redlich,[a] Sergei I. Kozhushkov,[a] Dmitry S. Yufit,[b]
[c]
[c]
[a]
[d]
´
Jörg Magull, Denis Vidovic, Heiko Schill, and Henning Menzel
Dedicated to Professor Dr. Philip J. Parsons on the occasion of his 60th birthday
Keywords: Small ring systems / Structure elucidation / Conformation analysis / Conjugation / Diels–Alder reactions /
Titanium
(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene (3) and (Z,Z)-
1,4-diodo-1,2,3,4-tetracyclopropylbuta-1,3-diene (4) were
prepared from dicyclopropylacetylene via an intermediate
2,3,4,5-tetracyclopropyltitanacyclopentadiene (2) in 91 and
77% yield, respectively. In the crystal, 3 adopts a conforma-
tion with an almost coplanar (φ = 163°) 1,3-diene core, with
the inner vinylcyclopropane units in an orthogonal and the
outer vinylcyclopropane moieties in an s-trans orientation.
This diene, like 2,3-cyclopropylbuta-1,3-diene (5), undergoes
facile concerted [4+2] cycloadditions at 130 °C with dimethyl
acetylenedicarboxylate as well as N-phenylmaleimide and at
0 °C with N-phenyltriazolinedione. An X-ray crystal struc-
ture analysis of 2,3-dicyclopropylbuta-1,3-diene (5) also re-
veals a coplanar inner core with the vinylcyclopropane units
in essentially orthogonal (φav = 89.3°) orientation. Differential
scanning calorimetry (DSC) measurements indicate that 3
undergoes significant internal reorganization on going from
the liquid to the crystalline phase, and a gauche conformer
of 3 may well be favored over the s-trans conformer in the
liquid.
the structure of 2,3-dicyclopropylbuta-1,3-diene (5)[6] and
the previously unknown (E,E)-1,2,3,4-tetracyclopro-
pylbuta-1,3-diene (3) as well as the Diels–Alder reactivities
of both.
Introduction
1,3-Butadiene is known to exist predominantly as an s-
trans conformer (ψ = 180°)[2] with a very minor fraction in
a gauche orientation (φ = 35°).[2h] In spite of this, 1,3-buta-
diene undergoes [4+2] cycloadditions (Diels–Alder reac-
tions) with reasonable facility. Bulky substituents such as
tert-butyl groups in the 2- and 3-position, however, force
the 1,3-diene unit out of planarity.[3] Although the cy-
clopropyl group is considerably smaller than tert-butyl and
even isopropyl substituents,[4] two cyclopropyl groups in the
2,3-positions might also influence the conformation of the
buta-1,3-diene unit[5] and thus the facility of its undergoing
a [4+2] cycloaddition. We therefore set out to investigate
Results and Discussion
Adopting the protocol of Sato et al.,[7] dicyclopro-
pylacetylene (1)[8] was treated with isopropylmagnesium
bromide in the presence of titanium tetraisopropoxide. Sub-
sequent methanolysis of the intermediately formed titana-
cyclopentadiene 2 gave (E,E)-1,2,3,4-tetracyclopropylbuta-
1,3-diene (3) as a single diastereomer in 90% yield
(Scheme 1). Its configuration was established by an X-ray
crystal-structure analysis (see Figure 1).[9] Addition of ele-
mental iodine to a solution of the initially formed interme-
diate 2 furnished (Z,Z)-1,4-diiodo-1,2,3,4-tetracyclopro-
pylbuta-1,3-diene (4) in 77% yield (Scheme 1).[10] The latter
may be useful for various transition-metal-catalyzed cross-
coupling reactions,[11] which would provide facile accesses
to further 1,4-disubstituted 1,2,3,4-tetracyclopropylbuta-
1,3-dienes.[12]
[‡] See ref.[1]
[a] Institut für Organische und Biomolekulare Chemie der Georg-
August-Universität Göttingen,
Tammannstrasse 2, 37077 Göttingen, Germany
Fax: +49-551-399475;
E-mail: Armin.deMeijere@chemie.uni-goettingen.de
Homepage: http://www.adm.chemie.uni-goettingen.de/
[b] Department of Chemistry, Durham University,
South Rd., Durham DH1 3L, UK
[c] Institut für Anorganische Chemie der Georg-August-Uni-
versität Göttingen,
Tammannstrasse 4, 37077 Göttingen, Germany
[d] Institut für Technische Chemie der Technischen Universität
Braunschweig,
Crystal structure analysis revealed that the 1,3-diene unit
in 3 is almost coplanar, with a dihedral angle φ = 163° in a
close to s-trans (ap) conformation. Both of the outer ethen-
ylcyclopropane moieties are also in an s-trans orienta-
Hans-Sommer-Str. 10, 38106 Braunschweig, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201054
Eur. J. Org. Chem. 2012, 6953–6958
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FULL PAPER
same as that in the liquid, in which an equilibrium of s-
trans and a gauche conformer may exist.[2,14]
As in the cases of other molecules,[14] structures close to
s-trans or s-trans conformations preferred in the crystals of
3 and 5 may be due to energetically favorable crystal pack-
ings (Figure 2), since differential scanning calorimetry
(DSC) measurements indicate that the molecules undergo a
significant internal reorientation on going from the liquid
to the crystalline phase.
Scheme 1. Synthesis of (E,E)-1,2,3,4-tetracyclopropylbuta-1,3-
diene (3) and (Z,Z)-1,2,3,4-tetracyclopropyl-1,4-diiodobuta-1,3-
diene (4).
Figure 2. Fragments of the molecular packing of (E,E)-1,2,3,4-
tetracyclopropylbuta-1,3-diene (3; top) and 2,3-dicyclopropylbuta-
1,3-diene (5; bottom) in the crystals.[9]
Upon slow cooling (10 Kmin–1) of a sample of 3, no
crystallization occurs, but solidification into a glass takes
place at –75 °C (see the Supporting Information). The glass
transition is also visible at –71 °C upon re-warming, and
crystallization becomes evident at –28 °C. The crystalli-
zation temperature varies slightly from one cycle to the
next, e.g., in the third cycle it was –26 °C, but overall these
events were well reproducible. In an isothermal experiment,
the crystallization of 3 can be recorded as an exothermal
event occurring at approximately –27 °C within about
20 min (see the Supporting Information). This behavior of
severe supercooling and formation of a glass is somewhat
Figure 1. Molecular structures of (E,E)-1,2,3,4-tetracycloprop-
ylbuta-1,3-diene (3; top) and 2,3-dicyclopropylbuta-1,3-diene (5;
bottom) in the crystals.[9]
tion,[13] while the two inner ethenylcyclopropane units unusual for a low molecular weight compound, but is well-
adopt a virtually perpendicular gauche conformation with known for polymers and is related to a slow crystalli-
an average φ = 89.3° (Figure 1, upper part; φ is the torsion zation.[15]
angle C=C–C···center of the opposite C–C bond in the cy-
Although cyclopropyl groups are much less bulky than
clopropane ring). As far as the inner part is concerned, this tert-butyl groups,[16] two of them at the inner carbon atoms
is essentially the same conformation as that in 2,3-dicy- of the butadiene derivative 3 apparently create enough con-
clopropylbuta-1,3-diene (5) (Figure 1, lower part). The lat- gestion to slow down the conformational reorganization
ter was prepared for comparison with 3 according to a around –30 °C on going from the liquid to the crystalline
known method[6a] but using an improved protocol for the state.
preparation of the precursor, the 2,3-dicyclopropylbutane-
In spite of the overall steric congestion in (E,E)-1,2,3,4-
2,3-diol.[6b] It should be noted that the observed single con- tetracyclopropylbuta-1,3-diene (3), it readily undergoes
former of a molecule in the crystal is not necessarily the Diels–Alder reactions with dimethyl acetylenedicarboxylate
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(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene
(DMAD; 6) and N-phenylmaleimide (7), albeit only after
extended heating (22 h) in toluene at 130 °C (Scheme 2).
For comparison, butadiene[17a] and 2,3-dimethylbutadi-
ene[17b,17c] react with DMAD at ambient temperature or at
70–80 °C, respectively. The products 8 and 9 were isolated
in 70% yield each, and both were formed as single dia-
stereomers, as indicated by their NMR spectra as well as
by an X-ray crystal structure analysis of 9 (Scheme 2).[9]
Scheme 3. [4+2] Cycloadditions of cyclopropyl-substituted butadi-
enes 5 and 3 to N-phenyltriazolindione (10) and crystal structure
of the product 11.[9]
favored over the s-trans conformer in the liquid, whereas a
conformation with an almost coplanar (φ = 163°) 1,3-diene
core is preferred in the crystal.
Experimental Section
General Remarks: All operations in anhydrous solvents were per-
formed under argon in flame-dried glassware. Anhydrous diethyl
ether, toluene, and THF were obtained by distillation from sodium
benzophenone ketyl, anhydrous CH2Cl2 by distillation from cal-
cium hydride, and methanol by distillation from magnesium meth-
oxide. All other chemicals were used as commercially available. Or-
ganic extracts were dried with MgSO4. NMR spectra were recorded
with Bruker AM 250 (250 MHz for 1H and 62.9 MHz for 13C
NMR) or Bruker DPX 300 (300.13 MHz for 1H and 75.54 MHz
for 13C NMR) instruments in CDCl3 solutions, if not otherwise
specified. Multiplicities were determined by DEPT (Distortionless
Enhancement by Polarization Transfer) measurements. Chemical
shifts refer to δTMS = 0.00 ppm according to the chemical shifts of
residual CHCl3 signals. IR spectra were recorded with a Bruker
IFS 66 FTIR on KBr pellets or oils between NaCl plates. Mass
spectra were measured with a Finnigan MAT 95 (EI and HR-EI,
at 70 eV, using preselected ion peak matching at R ϾϾ 10000 to
be within Ϯ2 ppm of the exact masses) spectrometer. Melting
points were determined with a Büchi 510 capillary melting point
apparatus; values are uncorrected. TLC analyses were performed
on precoated sheets (0.25 mm Sil G/UV254; Macherey–Nagel). Sil-
ica gel grade 60 (230–400 mesh) (Merck) was used for column
chromatography.
Scheme 2. Diels–Alder reactions of (E,E)-1,2,3,4-tetracyclopro-
pylbuta-1,3-diene (3) with dimethyl acetylenedicarboxylate (6) as
well as N-phenylmaleimide (7) and the crystal structure of the
product 9.[9]
On the other hand, the highly reactive dienophile N-
phenyltriazolindione (10; PTAD),[18,19] instantaneously re-
acted with both 2,3-dicyclopropylbuta-1,3-diene (5) and
(E,E)-1,2,3,4-tetracyclopropylbuta-1,3-diene (3) even at
0 °C (Scheme 3). The products 11 and 12 were isolated in 95
and 81% yield, respectively, and 12, according to its NMR
spectra, was obtained as a single diastereomer with the 3,6-
cyclopropyl groups in cis orientation. This indicates a con-
certed [4+2] cycloaddition of 3 and 10 (PTAD)[18d] rather
than a stepwise reaction via a zwitterionic intermediate.[18b]
The latter reaction mode is well-known for PTAD, which
can act as an oxidant.[19] However, the oxidation potential
of (E,E)-1,2,3,4-tetracyclopropylbuta-1,3-diene (3) is appar-
ently too high, so that it cannot transfer an electron to
PTAD.[20]
Dicyclopropylacetylene[8] (1) and 2,3-Dicyclopropylbuta-1,3-diene[6]
(5): Prepared according to previously published protocols. Data for
5: 1H NMR (300 MHz, CDCl3): δ = 0.43–0.48 (m, 4 H, cPr-H),
0.65–0.72 (m, 4 H, cPr-H), 1.45–1.56 (m, 2 H, cPr-H), 4.91 (br. s,
2 H, =CH2), 5.38 (br. s, 2 H, =CH2) ppm. 13C NMR (75.5 MHz,
CDCl3, DEPT): δ = 6.0 (4 CH2), 14.6 (2 CH), 109.9 (2 CH), 149.1
(2 C) ppm.
Conclusions
(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene (3): To a solution of
dicyclopropylethyne (1; 1.0 g, 9.42 mmol) and Ti(OiPr)4 (2.67 g,
9.42 mmol) in anhydrous Et2O (70 mL), kept at –78 °C, was added
dropwise a solution of isopropylmagnesium bromide (1.41 m in
(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene (3) as well
as its 1,4-diiodo derivative 4 are easily accessible from dicy-
clopropylacetylene (1) by one-pot procedures. According to
DSC measurements, a gauche conformer of 3 may well be Et2O, 20.7 mmol, 14.7 mL), upon which the reaction mixture
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1
turned yellow. After 1.5 h stirring at –50 to –40 °C, the black reac-
tion mixture was cooled to –78 °C, and a mixture of anhydrous
MeOH (5 mL) and anhydrous Et2O (7 mL) was added dropwise.
The mixture was warmed to ambient temperature and poured into
3 m aq. HCl (50 mL). The two phases were separated and the aque-
ous solution was extracted with Et2O (3ϫ15 mL). The combined
organic phases were washed with brine (30 mL), dried, and concen-
trated under reduced pressure. Column chromatography of the resi-
due (55 g of silica gel; 3ϫ20 cm column; pentane; Rf = 0.73) af-
forded 3 (906 mg, 90%) as a colorless oil, which solidified at low
831, 795, 761, 747, 667, 561 cm–1. H NMR (250 MHz, CDCl3): δ
= 0.25–0.60 (m, 14 H, cPr-H), 0.52–0.71 (m, 2 H, cPr-H), 0.75–0.91
(m, 2 H, cPr-H), 1.63–1.72 (m, 2 H, cPr-H), 2.45 (d, J = 8.1 Hz, 2
H, 3,6-H), 3.75 (s, 6 H, OMe) ppm. 13C NMR (62.9 MHz, C6D6,
DEPT): δ = 4.0 (2 CH2), 4.6 (2 CH2), 6.1 (2 CH2), 7.2 (CH2), 8.1
(CH2), 10.3 (CH), 13.7 (CH), 17.8 (2 CH), 43.2 (2 C), 51.6 (CH3),
52.7 (CH3), 132.4 (C), 135.2 (C), 138.5 (C), 152.0 (C), 168.7 (2
C) ppm. MS (EI, 70 eV): m/z (%) = 356 (97) [M]+, 325 (36), 297
(63) [M – C2H3O2], 283 (100), 265 (72), 255 (42), 237 (84), 195 (39),
181 (37), 165 (44), 155 (39), 128 (32), 91 (22), 77 (11), 59 (24)
[C2H3O2]+, 41 (41) [C3H5]+. C22H28O4 (356.47): calcd. C 74.13, H
7.92; found C 74.48, H 7.70.
temperature to a glassy solid. IR (film): ν = 3080, 3003, 2868, 1457,
˜
1428, 1387, 1292, 1174, 1097, 1044, 1018, 978, 965, 945, 891, 809,
736, 668, 600, 572, 518 cm–1. 1H NMR (250 MHz, CDCl3): δ =
0.22–0.50 (m, 8 H, cPr-H), 0.57–0.87 (m, 8 H, cPr-H), 1.51 (mc, 2
H, cPr-H), 1.77 (mc, 2 H, cPr-H), 4.75 (d, J = 9.5 Hz, 2 H, 1-H, 4-
H) ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ = 6.1 (4 CH2),
7.2 (4 CH2), 10.3 (2 CH), 11.0 (2 CH), 133.1 (2 CH), 139.2 (2
C) ppm. MS (EI, 70 eV): m/z (%) = 214 (28) [M]+, 199 (4) [M –
CH3]+, 185 (18), 173 (22) [M – C3H5]+, 157 (44), 143 (52), 129 (72),
117 (56), 105 (45), 91 (100), 79 (58), 67 (30), 55 (24), 41 (29)
[C3H5]+. C16H22 (214.35): calcd. C 89.65, H 10.35; found C 89.68,
H 10.25. Its configuration was established by X-ray crystal struc-
ture analysis.[9]
syn-4,5,6,7-Tetracyclopropyl-2-phenyl-3a,4,7,7a-tetrahydro-1H-
isoindole-1,3-dione (9): Column chromatography (110 g of silica gel;
3.5ϫ35 cm column; pentane/Et2O, 5:1; Rf = 0.31) of the residue
obtained from diene 3 (1.00 g, 4.67 mmol) and N-phenylmaleimide
(7) (815 mg, 4.71 mmol) in toluene (8 mL) according to GP1 fur-
nished 9 (1.26 g, 70%) as a colorless amorphous solid; m.p. 152 °C.
IR (KBr): ν = 3078, 3002, 2835, 1770, 1707, 1598, 1500, 1456, 1428,
˜
1379, 1322, 1243, 1166, 1105, 1028, 909, 880, 869, 821, 754, 733,
1
703, 690, 624, 615, 583, 463 cm–1. H NMR (300 MHz, CDCl3): δ
= 0.13 (mc, 4 H, cPr-H), 0.42 (mc, 2 H, cPr-H), 0.53 (mc, 2 H, cPr-
H), 0.62–0.89 (m, 8 H, cPr-H), 1.23 (d, J = 10.6, 3.7 Hz, 2 H, 4,7-
3
(Z,Z)-1,2,3,4-Tetracyclopropyl-1,4-diiodobuta-1,3-diene (4): To
a
H), 1.31–1.45 (m, 2 H, cPr-H), 1.76 (mc, 2 H, cPr-H), 3.21 (dd, J
solution of dicyclopropylethyne (1; 1.0 g, 9.42 mmol) and
Ti(OiPr)4 (2.67 g, 9.42 mmol) in anhydrous Et2O (70 mL), kept at
–78 °C, was added dropwise a solution of isopropylmagnesium
bromide (1.41 m in Et2O, 20.7 mmol, 14.7 mL), upon which the re-
action mixture became yellow. After 1.5 h stirring at –50 to –40 °C,
the black reaction mixture was cooled to –78 °C, and iodine pow-
der (7.19 g, 28.3 mmol) was added in one portion. The mixture was
warmed to ambient temperature and poured into sat. aq. Na2S2O3
(50 mL). The two phases were separated, and the aqueous solution
was extracted with Et2O (3ϫ20 mL). The combined organic phases
were washed with brine (30 mL), dried, and concentrated under
reduced pressure. Column chromatography of the residue (55 g of
silica gel; 3ϫ20 cm column; pentane; Rf = 0.45) afforded 4 (1.68 g,
77%) as a colorless oil. 1H NMR (250 MHz, CDCl3): δ = 0.58–
0.80 (m, 8 H, cPr-H), 0.80–1.08 (m, 8 H, cPr-H), 1.68–1.95 (m, 4
H, cPr-H) ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ = 6.7 (2
CH2), 7.5 (2 CH2), 10.8 (2 CH2), 11.0 (2 CH2), 15.1 (2 CH), 19.2
(2 CH), 112.6 (2 C), 148.0 (2 C) ppm. MS (EI, 70 eV): m/z (%) =
466 (36) [M]+, 339 (100) [M – I]+, 283 (6), 212 (11) [M – 2 I]+, 169
(28), 155 (42), 128 (40), 91 (34), 77 (25), 65 (12), 41 (16) [C3H5]+.
HRMS (EI): calcd. for C16H20I2 [M]+ 465.9654; found 465.9654.
= 3.7, J = 1.9 Hz, 2 H, 3a,7a-H), 7.12–7.19 (m, 2 H, Ar-H), 7.29–
7.37 (m, 1 H, Ar-H), 7.29–7.37 (m, 2 H, Ar-Ha) ppm. 13C NMR
(75 MHz, CDCl3, DEPT): δ = 4.4 (2 CH2), 8.1 (2 CH2), 8.3 (2
CH2), 8.7 (2 CH2), 10.4 (2 CH), 12.5 (2 CH), 45.5 (2 CH), 48.2 (2
CH), 126.3 (2 CH), 128.3 (CH), 128.9 (2 CH), 131.9 (C), 138.9 (2
C), 177.3 (2 C) ppm. MS (EI, 70 eV): m/z (%) = 387 (50) [M]+, 358
(60), 344 (21), 330 (10), 316 (9), 302 (4), 268 (3), 228 (18), 212 (28)
[C16H20]+, 199 (38), 169 (45), 159 (82), 145 (90), 131 (100), 117
(93), 91 (79), 77 (36) [C6H5]+, 67 (22), 41 (28) [C3H5]+. C26H29NO2
(387.53): calcd. C 80.59, H 7.54, N 3.61; found C 80.83, H 7.30, N
3.75. Its configuration was established by X-ray crystal structure
analysis.[9]
General Procedure for [4+2] Cycloadditions of Cyclopropyl-Substi-
tuted Buta-1,3-dienes 3 and 5 to N-Phenyl-1,3,4-triazoline-2,5-dione
(PTAD; 10) (GP2): A solution of PTAD (1 mmol) in anhydrous
dichloromethane (10 mL) was added dropwise to a stirred solution
of respective diene (1.1 mmol) in CH2Cl2 (10 mL) at 0 °C at such
a rate that the reaction mixture decolorized before the addition of
the next drop. After stirring for an additional 10 min, the reaction
mixture was concentrated under reduced pressure. The product was
purified as indicated below.
General Procedure for the Diels–Alder Reactions of (E,E)-1,2,3,4-
Tetracyclopropylbuta-1,3-diene (3) with Dienophiles 6 and 7 (GP1):
Diene 3 and the respective dienophile were weighed into a thick-
walled screw-capped Pyrex ampoule with a magnetic stirring bar.
Anhydrous toluene was added, the ampoule was flushed with ar-
gon, sealed with the screw-cap and heated at 130 °C with magnetic
stirring for 22 h. After cooling to ambient temperature, the solvent
was removed under reduced pressure, and the residue was subjected
to column chromatography on silica gel (pentane/Et2O).
6,7-Dicyclopropyl-2-phenyl-5,8-dihydro-1H-[1,2,4]triazolo[1,2-a]-
pyridazine-1,3(2H)-dione Hemihydrate (11·0.5H2O): The residue,
obtained from PTAD (10; 200.0 mg, 1.14 mmol) and 2,3-dicy-
clopropyl-1,3-butadiene (5; 169.0 mg, 1.26 mmol) according to
GP2, was taken up with THF (5 mL), filtered through a 5-mm pad
of silica gel and the solution was concentrated again. The oily resi-
due solidified upon addition of hexane (2 mL). Slow evaporation
of its solution in octane/CH2Cl2 at 4 °C was accompanied by ab-
sorption of atmospheric moisture and furnished the pure cycload-
duct 11·0.5H2O (344.8 mg, 95%) as a hemihydrate in the form of
long colorless needles. Upon heating, these needles “jump” at
60 °C, partially loose water at 92 °C, and melt at 102 °C, however,
they immediately solidify again to form a new phase (also needles),
which melt at 129–130 °C. 1H NMR (250 MHz, CDCl3): δ = 0.55–
0.61 (m, 4 H, Cpr-H), 0.77–0.81 (m, 4 H, Cpr-H), 1.83–1.92 (m, 2
H, Cpr-H), 3.85 (s, 4 H, 2 CH2), 7.33–7.39 (m, 1 H, Ar-H), 7.43–
7.53 (m, 4 H, Ar-H) ppm. 13C NMR (250 MHz, CDCl3): δ = 4.6
Dimethyl
cis-3,4,5,6-Tetracyclopropylcyclohexa-1,4-diene-1,2-di-
carboxylate (8): Column chromatography (110 g of silica gel;
3.5ϫ35 cm column; pentane/Et2O, 10:1; Rf = 0.30) of the residue
obtained from diene 3 (1.00 g, 4.67 mmol) and DMAD 6 (663 mg,
4.67 mmol) in toluene (8 mL) according to GP1 furnished 8 (1.16 g,
70%) as a colorless amorphous solid; m.p. 65 °C. IR (KBr): ν =
˜
3433, 3082, 3005, 2949, 2903, 2841, 1722, 1663, 1636, 1457, 1387,
1348, 1264, 1196, 1153, 1116, 1061, 1022, 972, 947, 916, 888, 862,
6956
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Eur. J. Org. Chem. 2012, 6953–6958

(E,E)-1,2,3,4-Tetracyclopropylbuta-1,3-diene
(4 CH2), 11.6 (2 CH), 43.7 (2 CH2), 125.4 (2 CH), 126.4 (CH),
128.1 (2 C), 129.1 (2 CH), 131.1 (C), 152.4 (2 C) ppm.
(2 ϫ 11) ϫ H2O: C36H40N6O5 (636.74): calcd. C 67.91, H 6.33;
found C 67.66, H 6.19. Its structure was confirmed by an X-ray
crystal structure analysis.[9]
Acknowledgments
This work was supported by the Federate State of Niedersachsen,
the Fonds der Chemischen Industrie, and the British Engineering
and Physical Sciences Research Council (EPSRC). We are grateful
to the company Chemetall GmbH for generous gifts of chemicals,
to Prof. Burkhard König, Regensburg, for an attempt to measure
the oxidation potential of compound 3, to Dr. Sebastian Dechert,
Institut für Anorganische Chemie der Georg-August-Universität
Göttingen, for his help with compound 9, and to Dr. Ol’ga Chet-
ina, University of Durham, for growing crystals of compound 11.
5,6,7,8-Tetracyclopropyl-2-phenyl-5,8-dihydro-1H-[1,2,4]triazolo-
[1,2-a]pyridazine-1,3(2H)-dione (12): Column chromatography (80 g
of silica gel; 30ϫ2.8 cm column; hexane/THF, 5:1; Rf = 0.33) of the
residue obtained from PTAD (10; 175.2 mg, 1 mmol) and 1,2,3,4-
tetracyclopropyl-1,3-butadiene (3; 235.8 mg, 1.1 mmol) afforded 12
(317.0 mg, 81%) as a colorless oil. 1H NMR (250 MHz, CDCl3): δ
= 0.59–0.95 (m, 16 H, Cpr-H), 1.13–1.15 (m, 2 H, Cpr-H), 1.74–
1.83 (m, 2 H, Cpr-H), 3.82 (d, J = 8.0 Hz, 2 H, 2 CH), 7.28–7.55
(m, 5 H, Ar-H) ppm. 13C NMR (250 MHz, CDCl3): δ = 3.3 (2
CH2), 4.9 (2 CH2), 5.7 (2 CH2), 7.6 (2 CH2), 12.5 (2 CH), 16.9 (2
CH), 57.7 (2 CH), 125.2 (2 CH), 127.4 (CH), 128.7 (2 CH), 131.7
(C), 133.6 (2 C), 149.1 (2 C) ppm. C24H27N3O2 (389.49): calcd. C
74.01, H 6.99; found C 73.90, H 7.14.
[1] Cyclopropyl Building Blocks for Organic Synthesis 163. For
part 162, see: M. Arndt, G. Hilt, A. F. Khlebnikov, S. I.
Kozhushkov, A. de Meijere, Eur. J. Org. Chem. 2012, 3112–
3121. Part 161: A. F. Khlebnikov, S. I. Kozhushkov, D. S. Yufit,
H. Schill, M. Reggelin, V. Spohr, A. de Meijere, Eur. J. Org.
Chem. 2012, 1530–1545.
[2] a) A. A. Bothner-By, D. F. Koster, J. Am. Chem. Soc. 1968,
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Crystal Structure Determinations: Suitable crystals of compounds
9 and 11 were grown by slowly concentrating their diluted solu-
tions; the crystals of hydrocarbons 3 and 5 were grown in situ in
glass capillaries of 0.5 mm diameter. Single-crystal X-ray data were
collected with a Bruker SMART CCD 6000 (for 3 and 5) and a
Stoe–Siemens–Huber IPDS-II (for 9) diffractometer (graphite
monochromator, Mo-Kα radiation), equipped with Cryostream
(Oxford Cryosystems) low-temperature devices. The structures were
solved by direct methods and refined by full-matrix least-squares
on F2. All non-hydrogen atoms were refined anisotropically. The H
atoms in the structures of 3 and 5 were located in the difference
Fourier map and refined isotropically; in the structure 9 they were
placed in the calculated positions and refined in riding mode. The
parameters of crystal data collections and structure refinements are
presented in Table 1.[9]
Table 1. Crystal and data collection parameters for compounds 3,
5, and 9.
3
5
9
Empirical formula
Molecular mass
Temperature [K]
Crystal system
Space group
a [Å]
C16H22
214.34
120(2)
C10H14
134.21
200(2)
C26H29NO2
387.50
133(2)
orthorhombic monoclinic orthorhombic
P212121
8.3232(2)
9.2129(2)
16.9630(3)
90
P21c
P212121
7.7020(6)
15.2195(11)
17.5981(16)
90
6.3375(8)
8.555(1)
8.147(1)
90.06(3)
441.7(1)
2
b [Å]
c [Å]
β [°]
[5] For example, whereas 2,3-dimethylbuta-1,3-diene exists vir-
tually quantitatively as the s-trans conformer, the diene system
in 2,3-dineopentyl-1,3-butadiene is significantly twisted, and
only about 30% of its s-trans conformer coexists with the
twisted conformer, see: R. B. Bates, B. Gordon III, T. K.
Highsmith, J. J. White, J. Org. Chem. 1984, 49, 2981–2987.
[6] a) U. M. Dzhemilev, R. I. Khusnutdinov, V. A. Dokichev, S. I.
Lomakina, L. M. Khalilov, G. A. Tolstikov, O. M. Nefedov,
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Org. Chem. 1989, 54, 877–884.
V [Å3]
1300.74(5)
4
2062.9(3)
4
Z
F(000)
472
1.094
0.061
18008
148
832
1.248
0.078
7185
D [gcm–3]
1.009
0.056
3012
μ [mm–1]
Reflections collected
Reflections independent 2182
1141
3533
Rint
0.0271
0.0414
0.0435
0.1271
74
0.0567
0.0401
0.0957
262
R1 [IՆ2σ(I)]
wR2(all data)
Parameters refined
GOOF
0.0316
0.0909
233
[7] a) H. Urabe, T. Hata, F. Sato, Tetrahedron Lett. 1995, 36, 4261–
4264; b) H. Urabe, F. Sato, J. Org. Chem. 1996, 61, 6756–6757;
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1.128
1.020
1.046
[8] Dicyclopropylacetylene (1) was prepared from commercially
available cyclopropylacetylene and 1-bromo-3-chloropropane
via 5-chloro-1-cyclopropylpent-1-yne adopting a published
procedure for the conversion of 1,8-dichlorooct-4-yne into di-
Supporting Information (see footnote on the first page of this arti-
cle): NMR spectra of all new compounds and DSC recordings for
3.
Eur. J. Org. Chem. 2012, 6953–6958
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6957

A. de Meijere et al.
FULL PAPER
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See ref.[4a]
[14]
[15]
[9] CCDC-900666 (for 3), -900667 (for 5), and -900668 (for 9) con-
tain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_r-
equest/cif. The X-ray crystal structure analyses of 11 does es-
tablish its relative configuration, but the poor quality of the
crystals of this compound led to unsatisfactorily high R values
and inaccurate geometrical parameters, which neither permits
a discussion of any structural peculiarities of this compound
nor to save the results of these measurements in the Cambridge
Crystallographic Data Centre.
[16]
[17]
[10] The transformation is completely analogous to those reported
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voltammetry did not reveal any reversible oxidation event.
Received: August 4, 2012
Published Online: October 30, 2012
6958
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 6953–6958