Carbenoid rearrangement in the series of substituted gem- dibromospiropentanes

Article abstract of DOI:10.1134/S1070428008070038

A series of new substituted gem-dibromospiropentanes was studied in a reaction with methyllithium at -55...-50°C. This reaction is a carbenoid rearrangement that leads to the formation of monomeric and dimeric bromocyclobutenes and also to the products of

Full text of DOI:10.1134/S1070428008070038

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 7, pp. 950−957. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © K.N. Sedenkova, E.B. Averina, Yu.K. Grishin, T.S. Kuznetsova, N.S. Zefirov, 2008, published in Zhurnal Organicheskoi Khimii,
2008, Vol. 44, No. 7, pp. 962−969.
Carbenoid Rearrangement in the Series of Substituted
gem-Dibromospiropentanes
K. N. Sedenkova, E. B. Averina, Yu. K. Grishin, T. S. Kuznetsova, and N. S. Zefirov
Lomonosov Moscow State University, Moscow, 119992 Russia
e-mail: elaver@org.chem.msu.ru
Received November 20, 2007
Abstract—A series of new substituted gem-dibromospiropentanes was studied in a reaction with methyllithium
at –55...–50°C. This reaction is a carbenoid rearrangement that leads to the formation of monomeric and dimeric
bromocyclobutenes and also to the products of cyclobutylidene insertion into a C–H bond of the solvent depending
on the character of substituents in the dibromospiropentane fragment.
DOI: 10.1134/S1070428008070038
We formerly found that some gem-dibromo-substitut-
ed spiropentanes abnormally reacted with alkyllithium
reagents: Depending on the conditions alongside the
expected allenes products were obtained resulted from
an uncommon dibromotriangulane rearrangement, mono-
meric or dimeric bromocyclobutenes [1–3]. Based on the
experimental findings obtained [4] and also on the known
data on the reaction of dihalocyclopropanes with alkyl-
litium reagents [5, 6] we suggested a general scheme of
the reaction between dibromospiropentanes and methyl-
lithium (Scheme 1).
In keeping with this scheme the key stage of the
rearrangement is the reaction of dibromide I with
methyllithium leading to a lithium derivative II followed
Scheme 1.
Li
Li
Br
Li
R1
R2
R1
R2
R1
R2
R1
R2
Br
R3
Br
R3
1
a
R3
R3
4
+
CH3Li
_MeBr
3
_Br_
b
5
+
2
R3
R3
R3
II
R1
R3
IV
III
I or MeBr
I
Li
R1
R2
R1
R2
Br
Br
Br_
4
5
1
Br
3
2
R2
R3
R3
R3
Li
Br
R3
R3
R3
VIII
V
VI
_LiBr
Et2O
R3 = H
Br
VI
Br
R1
R2
R1
R2
R1
R2
O
R3
R3
VII
IX
950

CARBENOID REARRANGEMENT
951
by a nucleophilic attack of the C–C bond of the three-
membered ring on the carbenoid center with the forma-
tion of the corresponding cyclobutylidene intermediate
V that can further either insert into the C–H bond of the
solvent giving ether VII or isomerize into intermediate
VI, a precursor of compounds VIII and IX. In the case
of an unsym-metrically substituted dibromospiropentane
I a migration of the bond a or b to the carbenoid center
may occur with the formation of regioisomers of
compounds VIII and IX.
In reaction with methyllithium of dibromides XVIII–
XX as expected the main reaction products were dimeric
bromocyclobutenes XXVI–XXVIII (Scheme 3).
Compounds XXVI–XXVIII can form as two possible
regioisomers with substituents in positions 3 or 4 of the
cyclobutene ring. Besides the molecules of rearrangement
products XXVI and XXVII contain each two asymmetric
centers therefore each of these compounds should exist
as a mixture of two diastereomers. According to the
spectral data the formation of dimeric bromocyclobutenes
XXVI and XXVIII occurred regioselectively, and
compound XXVII was obtained as a mixture of four
isomers.
Apparently the character of substituents in the spiro-
pentane moiety governs the reaction pathway, the forma-
tion of rearrangement products or the insertion into the
C–H bond of the solvent. Therefore a number of problems
arises concerning the relationships in the dibromotri-
angulane rearrangement whose solution requires addi-
tional experimental research. In this connection we report
here on the investigation of the reaction with methyl-
lithium of a series of new substituted gem-dibromospiro-
pentanes containing a terminal or internal dibromocyclo-
propane fragment.
In the 13C NMR spectrum of dimer XXVI two sets of
signals were observed with very close chemical shift
values (Δδ 0.04–0.18 ppm). Consequently, compound
Scheme 2.
R4
Br
R4
R3
R1
R3
R1
R5
R6
1
4
,
CHBr3, t-BuOK
Br
R5
By the reaction of [1+2]-cycloaddition of dibromo-
carbene to alkenes of methylenecyclopropane series X–
XVII along the Doering−Hoffmann procedure [7] we
prepared in fair yields the corresponding dibromospiro-
pentanes XVIII–XXV (Scheme 2).
2
3
5
Petroleum ether
R2
X_XVII
R2
R6
XVIII_XXV
R2 = R3 = R4 = R5 = R6 = H, R1 = Ph (X, XVIII), n-C6H13
(XI, XIX); R1,R2 = (CH2)5, R3 = R4 = R5 = R6 = H (XII,
XX); R1 = R2 = R3 = R4 = H, R5,R6 = (CH2)5 (XIII, XXI),
(CH2)4 (XIV, XXII), (CH2)3 (XV, XXIII), (CH2)2 (XVI,
The reaction of gem-dibromospiropentanes with
methyllithium was carried out in ether at –55...–50°C
for just in these conditions the maximum yield of rear-
rangement products compared to allenes was attained as
we had established before [4].
XXIV); R1,R3 = (CH2)4, R2 = R4 = H, R5,R6
spirobicyclo[4.0.1]heptane (XVII, XXV).
=
Scheme 3.
Br
Br
Ph
Ph
3
2
4
1
XXVI
C6H13
Br
Br
Br
Br
Br
Br
2
H13C6
3
3
4
MeLi
Et2O, _55..._50oC
2
4
1
R1
1
R2
XVIII_XX
H13C6
C6H13
XXVIIa
XXVIIb
Br
Br
3
2
4
1
XXVIII
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 7 2008

SEDENKOVA et al.
952
XXVI formed as one of two possible regioisomers that
was a mixture of two diastereomers in an approximately
equal ratio. The NMR spectra of compound XXVI did
not permit the establishment what regioisomer formed
in the reaction of dibromospiropentane XVIII with
methyllithium, therefore we converted dibromide XXVI
into the corresponding hydrocarbon XXIX by the use of
a known reduction system lithium–t-BuOH [8, 9]. It was
established by NOE experiment (Scheme 4) that in
molecule XXIX the proton at the double bond is
contiguous to the proton in the CHPh moiety. The
additional confirmation of the formation of 3-phenyl-
substituted regioisomer XXVI was the considerable
upfield shift of proton and carbon signals of the CHPh
group in the spectra of reduction product XXIX compar-
ed to the spectra of initial dibromide XXVI (ΔδH ~0.2,
and ΔδC ~7.5 ppm respectively). The signals of carbon
atoms from the methylene groups of the cyclobutene
fragment have close values of the chemical shifts both
in dibromide XXVI (δ 40.4 and 40.5 ppm) and
hydrocarbon XXIX (δ 40.9 ppm).
As was shown in [4], dimer XXVIII formed as
a single regioisomer. To establish the substituent position
in the cyclobutene ring we reduced dibromide XXVIII
into hydrocarbon XXX. In favor of the formation of
regioisomer XXVIII substituted in the position 4 testified
the considerable upfield shift in the 13C NMR spectrum
of hydrocarbon XXX of the carbon signal belonging to
the CH2 group of the cyclobutene (δ39.4 ppm) compared
to the spectrum of dibromide XXVIII (δ 48.0 ppm);
therewith the chemical shifts of the quaternary carbon
atoms in the spectra of compounds XXVIII and XXX
had similar values (δ 50.4 and 49.2 ppm respectively).
Hence in the reaction of phenyl-substituted dibromo-
spiropentane X with methyllithium rearrangement
product XXVI formed through a migration to the
carbenoid center of intermediate II of the more
substituted bond a (Scheme 1). In the case of
dispirocompound XII the bond b migrates to the
carbenoid center leading to the formation of regioisomer
XXVIII substituted in the position 4.According to NMR
spectra the reaction of dibromospiropentane XI with
methyllithium was nonselective: The formed dimeric
bromocyclobutene XXVII was a mixture of two
regioisomers each of which contained two diastereomers.
We presumed that the presence in the initial dibromo-
spiropentanes of substituents stabilizing the transition
state in the course of the formation of intermediate III
should favor the migration of the more substituted bond
to the carbenoid center of intermediate II as was really
observed with dibromide XVIII. However it turned out
that with the growing bulk of the substituent the reaction
pathway was strongly affected by steric factors; as a result
either a regioisomers mixture formed (reaction of
dibromide XIX with methyllithium), or the regiodirection
was totally changed (reaction of dibromide XX with
methyllithium).
As shown in Scheme 1 the reaction of internal
dibromospiropentans with methyllithium led to the
formation of monomeric products of dibromotriangulane
rearrangement VIII or to the products of insertion into
the C–H bond of the solvent VII. To reveal the effect of
the volume of cyclic substituents in the spiropentane
fragment on the direction of the reaction we studied the
reaction with methyllithium of a series of polycyclic
dibromides XXI–XXIV.
Scheme 4.
1.6%
43.5 ppm
Ph
51.1 ppm
Br
H
H
Br
Ph
Ph
3
Li_i-BuOH
3
2
2
Ph
H
4
Et2O
1
0
4
1
%0%
H
40.9 ppm
39.4 ppm
40.4 ppm
48.0 ppm
XXIX, 90%
XXVI
Br Br
3
3
2
2
Li_i-BuOH
4
4
1
1
Et2O
50.4 ppm
XXVIII
49.2 ppm
XXX, 83%
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 7 2008

CARBENOID REARRANGEMENT
953
It proved that dibromides XXI–XXIII notwith-
standing the size of the substituent in the three-membered
ring provided in the reaction with methyllithium
exclusively the products of cyclobutylidene insertion into
the C–H bond of ether (Scheme 5), whereas from
dibromide XXIV formed solely substituted bromocyclo-
butene XXXIV. Inasmuch as the difference in the bulk
of substituents in the spiropentane fragment of
dibromides XXIII and XXIV was insignificant, it was
possible to expect in the reaction of compound XXIV
with methyllithium a formation of a mixture of substances
VII and VIII. However the analysis of the NMR spectra
of the reaction mixture showed that the treatment of
dibromodispiroheptane XXIV with methyllithium
resulted in the formation in a high yield of a single
reaction product, monomeric bromocyclobutene XXXIV
in agreement with the data of [1].
Evidently the dibromotriangulane rearrangement
under study possesses a carbocationic character and is a
rare example of the manifestation of the electrophilic
nature of the bromolithium carbenoids of the spiro-
pentane structure. In the most events the carbene carbon
atom of intermediate II is subjected to the nucleophilic
attack of the C–C bond resulting in the formation of
cyclobutylidene carbenoid V that further depending on
the bulk and apparently on the electronic character of
the substituents may either insert into the C–H bonds of
the solvent or undergo a [1,3]-sigmatropic migration of
the C–Li bond giving intermediate VI. It is also evident
that if in the course of the rearrangement the energy of
intermediates III and IV increases due to the growing
structural strain (reaction of dibromide XXV with
methyllithium) carbenoid II is stabilized by allene
formation.
An unexpected result was obtained in the reaction of
tetra-substituted dibromodispiroheptane XXV with
methyllithium (Scheme 6): Instead of monomeric bromo-
cyclobutene VIII or insertion product VII in this reaction
formed in a good yield even at –60°C exclusively allene
XXXV apparently because the isomerization of inter-
mediate II into cyclobutylidene V was impossible due
to steric factors.
Thus the data on the reaction of dihalospiropentanes
with methyllithium demonstrate the dual nature of lithium
carbenoids of the polyspirocyclopropane structure that
can react not only with electrophilic reagents (traditional
path) but also with nucleophiles, even so weak as the C–
C bond.
EXPERIMENTAL
The results obtained are consistent with the general
scheme of reaction between dibromospiropentanes with
methyllithium (Scheme 1) and indirectly confirm the
existence of intermediates II–VI.
1H and 13C NMR spectra were registered on a spec-
trometer BrukerAvance-400 at operating frequencies 400
and 100 MHz respectively from solutions of compounds
Scheme 5.
Br
Br
Br
(CH2)n
H3C
MeLi, Et2O
_50... _55oC
(CH2)n
CH
CH2CH3
(CH2)n
Br
XXXIV (70%)
O
XIII_XVI
XXXI (89%), XXXII (30%), XXXIII (58%)
n = 4 (XIII, XXXI), 3 (XIV, XXXII), 2 (XV, XXXIII), 1 (XVI, XXXIV).
Scheme 6.
Br
Br
MeLi, Et2O
_50... _60oC
C
XXXV, 60%
XXV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 7 2008

SEDENKOVA et al.
954
in CDCl3. The chloroform signal (δH 7.24, δC 77.10 ppm)
1,1-Dibromo-4-hexylspiro[2.2]pentane (XIX). The
reaction mixture was stirred for 20 h. Yield 52%, Rf 0.8
(petroleum ether). 1H NMR spectrum, δ, ppm: 0.88–
0.92 m (3H, CH3), 0.98 d.d (1H, CH2, cyclo-Pr, 2J 6.2, 3J
5.6 Hz), 1.26–1.40 m (11H, cyclo-Pr + hexane), 1.49 d.d
(1H, cyclo-Pr, 3J 5.6, 3J 8.0 Hz), 1.89 d (1H, CH2, cyclo-
served as internal reference.
Mass spectra were obtained on an instrument MS
Finnigan MAT ITD-700 at the energy of ionizing
electrons 70 eV. Mass spectra MALDI of positive ions
were recorded on a mass spectrometer Bruker Daltonics
Ultraflex using as a matrix 1,8,9-trihydroxyanthracene.
2
2
Pr, J 6.4 Hz), 1.96 d (1H, CH2, cyclo-Pr, J 6.4 Hz).
13C NMR spectrum, δ, ppm: 14.10 (CH3, 1JCH 124 Hz),
The progress of reactions was monitored and the
purity of the chemical substances was checked by TLC
on Silufol UV-254 plates. In the preparative column
chromatography silica gel Merck 40/60 was used. GLC
analyses were carried out on a chromatograph Chrom-5
equipped with a flame-ionization detector, column
3000×5 mm, stationary phase 10% SE-30, operating
temperature range 130–180°C. The preparative separa-
tion of low-boiling compounds was performed on
a PAKhV-08 device equipped with a katharometer as
a detector, column 3000×5 mm, stationary phase 15%
Ε-301 on Inerton AW, carrier gas helium, flow rate 80–
120 ml/min.
1
17.94 (CH2, cyclo-Pr, JCH 163 Hz), 22.64 (CH2,
1
1JCH 126 Hz), 23.82 (CH, JCH 163 Hz), 27.12 (CH2,
cyclo-Pr, 1JCH 165 Hz), 28.64 (CH2, 1JCH 126 Hz), 29.09
1
(CH2, JCH 124 Hz), 30.86 (Cspiro), 31.78 (CH2,
1JCH 122 Hz), 31.95 (CH2, 1JCH 120 Hz), 33.07 (CBr2).
Found, %: C 42.32; H 6.10. C11H18Br2. Calculated,
%: C 42.61; H 5.85.
1,1-Dibromodispiro[2.0.5.1]decene (XX). The
reaction mixture was stirred for 6 h. Yield 52%, bp 92–
93°C (2 mm Hg). 1H NMR spectrum, δ, ppm: 0.84 d
(1H, cyclo-Pr, 2J 4.5 Hz), 0.95 d (1H, cyclo-Pr, 2J 4.5 Hz),
1.15–1.42 m (2H, cyclohexane), 1.43–1.68 m (6H,
cyclohexane), 1.72–1.88 m (2H, cyclohexane), 1.80 d
Bicyclopropylidene XXIV was synthesized by
procedure [10]. Initial alkenes XVIII–XX were obtained
by methods [11–14], compounds XXI–XXIII, by [15–
17], alkene XXV, by [18, 19].
2
(1H, cyclo-Pr, J 6.2 Hz), 1.92 d.d (1H, cyclo-Pr,
4
2J 6.2, J 0.8 Hz). 13C NMR spectrum, δ, ppm: 22.76
(CH2, cyclo-Pr), 25.27 (CH2, cyclohexane), 25.70 (CH2,
cyclohexane), 26.01 (CH2, cyclohexane), 27.70 (CH2,
cyclo-Pr), 30.36 (Cspiro), 32.24 (Cspiro), 32.32 (CH2,
cyclohexane), 33.99 (CH2, cyclohexane), 36.19 (CBr2).
Found, %: C 40.87; H 4.75. C10H14Br2. Calculated, %:
C 40.82; H 4.76.
Addition of dibromocarbene to olefins X–XVII.
To 4.6 g (41 mmol) of t-BuOK and 21 mmol of olefin in
20 ml of petroleum ether while stirring and cooling to
0°C was added 6.15 g (2.2 ml, 25 mmol) of bromoform.
Then the reaction mixture was warmed to room
temperature, and the stirring was continued for 17–72 h.
The reaction mixture was treated with an equal volume
of ice water, the organic layer was separated, and the
products were extracted from the water layer into ether
(3× 20 ml). The combined organic extracts were washed
with water (3× 20 ml) and dried with MgSO4. The solvent
was distilled off, the residue was distilled in a vacuum
or subjected to chromatography.
10,10-Dibromodispiro[2.0.5.1]decene (XXI) [21].
The reaction mixture was stirred for 48 h. Yield 76%,
1
Rf 0.8 (petroleum ether), mp 49–50°C. H NMR spec-
trum, δ, ppm: 0.98–1.05 m (2H, cyclo-Pr), 1.11–1.17 m
(2H, cyclo-Pr), 1.33–1.62 m (6H, cyclohexane), 1.66–
1.83 m (4H, cyclohexane). 13C NMR spectrum, δ, ppm:
9.91 (2CH2, cyclo-Pr), 24.98 (2CH2, cyclohexane), 25.56
(CH2, cyclohexane), 33.70 (2CH2, cyclohexane), 33.73
(Cspiro), 35.33 (Cspiro), 49.56 (CBr2).
1,1-Dibromo-4-phenylspiro[2.2]pentane (XVIII)
9,9-Dibromodispiro[2.0.4.1]nonane (XXII). The
[20]. The reaction mixture was stirred for 18 h. Yield
1
reaction mixture was stirred for 23 h. Yield 32%, bp 49–
52%, bp 120°C (5 mm Hg). H NMR spectrum, δ, ppm:
1
1.65 d.d (1H, CH2, 2J 5.3, 3J 6.1 Hz), 1.91 d.d (1H, CH2,
50°C (1 mm Hg). H NMR spectrum, δ, ppm: 1.05–
3
2
2J 5.3, J 8.8 Hz), 1.94 d (1H, CH2, J 6.7 Hz), 2.11 d
1.20 m (4H, cyclo-Pr), 1.46–1.56 m (2H, cyclopentane),
1.60–1.70 m (2H, cyclopentane), 1.77–1.82 m (2H, cyclo-
pentane), 2.06–2.16 m (2H, cyclopentane). 13C NMR
spectrum, δ, ppm: 11.92 (2CH2, cyclo-Pr), 27.14 (2CH2,
cyclopentane), 34.17 (2CH2, cyclopentane), 36.66
(Cspiro), 40.34 (Cspiro), 48.37 (CBr2). Found %: C 38.50;
H 4.43. C9H12Br2. Calculated %: C 38.61; H 4.32.
2
3
(1H, CH2, J 6.7 Hz), 2.71 d.d (1H, CH, J 6.1,
3J 8.8 Hz), 7.14 d (2H, H°, 3J 7.6 Hz), 7.25–7.29 m (1H,
Hp), 7.32–7.38 m (2H, Hm). 13C NMR spectrum, δ, ppm:
20.29 (CH2), 27.76 (CH2), 28.04 (CH, cyclo-Pr), 29.72
(Cspiro), 35.52 (CBr2), 126.45 (2CH, Ph), 126.51 (CH,
Ph), 128.54 (2CH, Ph), 139.50 (C, Ph).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 7 2008

CARBENOID REARRANGEMENT
955
8,8-Dibromodispiro[2.0.3.1]octane (XXIII). The
reaction mixture was stirred for 24 h. Yield 42%, bp 60–
64°C (15 mm Hg). 1H NMR spectrum, δ, ppm: 1.05–
1.18 m (4H, cyclo-Pr), 1.80–2.05 m (4H, cyclo-Bu), 2.34–
2.49 m (2H, cyclo-Bu). 13C NMR spectrum, δ, ppm:
11.59 (2CH2, cyclo-Pr, 1JCH 165 Hz), 14.10 (CH2, cyclo-
Bu, 1JCH 136 Hz), 27.25 (2CH2, cyclo-Bu, 1JCH 138 Hz),
35.85 (Cspiro), 38.18 (Cspiro), 46.17 (CBr2). Mass spectrum
MALDI-TOF: m/z 264 [M]+. Found %: C 36.30; H 3.81.
C8H10Br2. Calculated %: C 36.13; H 3.79.
1,1'-Ethane-1,2-diylbis(2-bromo-3-hexylcyclo-
butene) (XXVIIa), 1,1'-ethane-1,2-diylbis(2-bromo-
4-hexylcyclobutene) (XXVIIb).* Yield 77%, Rf 0.7
(petroleum ether). 1H NMR spectrum, δ, ppm: 0.89–
0.92 m (6H, 2CH3), 1.25–1.49 m (20H), 1.61–1.67 m
(3H), 2.07–2.31 m (4H), 2.53–2.55 m (1H), 2.76–2.90
m (2H). 13C NMR spectrum, δ, ppm: 14.08 (4 isomers,
2CH3), 22.63 (4 isomers, 2CH2); 24.25, 24.33, 24.24,
24.49 (4 isomers, 1CH2); 25.03 (CH2), 25.08 (CH2),
25.13 (CH2); 26.66, 26.72, 26.79, 26.86 (4 isomers, CH2),
27.56 (2CH2); 29.40 (4 isomers, 2CH2), 29.70 (4 isomers,
2CH2), 31.80 (4 isomers, 2CH2); 32.32, 32.36, 32.47,
32.74 (4 isomers, CH2); 36.14, 36.18, 36.25, 36.34 (4
isomers, CH2); 41.74 (2CH2), 43.54, 43.60, 43.37, 43.88
(4 isomers, CH); 47.07 (4 isomers, CH); 109.12 (2C=),
114.37 (C=), 114.43 (=C), 145.41 (2C=), 151.24 (C=),
151.32 (C=). Mass spectrum MALDI-TOF: m/z 460 [M]+.
7,7-Dibromodispiro[2.0.2.1]heptane (XXIV) [22].
The reaction mixture was stirred for 24 h. Yield 79%,
mp 70°C (from hexane). 1H NMR spectrum, δ, ppm:
1.07–1.14 m (4H, cyclo-Pr), 1.23–1.27 m (4H, cyclo-Pr).
3',3'-Dibromodispiro(bicyclo[4.1.0]heptane-7,1'-
cyclopropane-2',7'’-bicyclo[4.1.0]heptane) (XXV)
[23]. The reaction mixture was stirred for 72 h. Yield
71%. 1H NMR spectrum, δ, ppm: 1.34–1.41 m (8H),
1.47–1.56 m (4H), 1.68–1.72 m (4H), 1.98–2.07 m (4H).
Mass spectrum MALDI-TOF: m/z 284 [M]+.
1,1'-Ethane-1,2-diylbis(2-bromospiro[3.5]non-1-
ene (XXVIII). Yield 75%, Rf 0.6 (petroleum ether).
1H NMR spectrum, δ, ppm: 1.09–1.24 m (2H), 1.25–
1.41 m (4H), 1.44–1.77 m (14H), 2.23 s (4H), 2.47 s
(4H). 13C NMR spectrum, δ, ppm: 23.37 (2CH2,
1JCH 130 Hz), 24.36 (4CH2, 1JCH 123 Hz), 25.48 (2CH2,
1JCH 119 Hz), 34.42 (4CH2, 1JCH 124 Hz), 48.03 (2CH2,
cyclo-Bu, 1JCH 141 Hz), 50.40 (2Cspiro), 109.43 (2CBr=),
155.33 (2C=). Found, %: C 56.00; H 6.02. C20H28Br2.
Calculated, %: C 56.07; H 6.54.
Reaction of gem-dibromocyclopropanes XVIII–
XXV with methyllithium. To a solution of 5.1 mmol of
dibromospiropentane in 10 ml of ether under an argon
atmosphere was added at –55°C within 1 h 6.85 ml (7.6
mmol) of 1.5 N solution of methyllithium. The reaction
mixture was warmed to 0°C and treated with an equal
volume of ice water. The organic layer was separated,
and the products were extracted from the water layer
into ether (3 × 5 ml). The combined organic solution
was washed with 10 ml of water and dried with MgSO4.
The solvent was distilled off, and the residue was purified
by preparative column chromatography.
[2-(1-Ethoxyethyl)cyclobutylidene]cyclohexane
1
(XXXI) [21]. Yield 89%. H NMR spectrum, δ, ppm:
3
1.15 d.d (3H, CH3, J 6.8, 6.3 Hz), 1.19 d (3H, CH3,
3J 5.5 Hz), 1.39–1.53 m (6H), 1.61–1.76 m (2H), 1.88–
1.94 m (2H, cyclo-Bu), 1.99–2.07 m (2H, cyclo-Bu),
2.40–2.56 m (2H), 3.14–3.22 m (1H, CH, cyclo-Bu),
3.39–3.53 m (2H, CH2O), 3.53–3.61 m (1H, CHO).
13C NMR spectrum, δ, ppm: 15.65 (CH3, 1JCH 126 Hz),
1,1'-[Ethane-1,2-diylbis(2-bromocyclobut-2-ene-
3,1-diyl)]dibenzene (XXVI) was obtained as a mixture
of two diastereomers A and B, 1.1:1. Yield 67%, Rf 0.1
1
(petroleum ether). H NMR spectrum, δ, ppm, A+B:
1
15.87 (CH3, JCH 126 Hz), 17.84 (CH2, cyclo-Bu,
2.51–2.53 m [6H, CH2 (A) + 6H, CH2 (B)], 3.10–3.11 m
[(2H, CH2, cyclo-Bu (A) + 2H, CH2, cyclo-Bu (B)],
4.19 br.s [2H, CH, cyclo-Bu (A) + 2H, CH, cyclo-Bu
(B)], 7.30–7.45 m [10H, Ph (A) + 10H, Ph (B)]. 13C NMR
spectrum, δ, ppm (A+B): 25.40 [CH2, 1JCH 130 Hz (A)],
25.44 [CH2, 1JCH 130 Hz (B)], 40.48 [2CH2, cyclo-Bu,
1JCH 142 Hz (B)], 40.41 [2CH2, cyclo-Bu, 1JCH 142 Hz
(A)], 51.06 [2CH, 1JCH 143 Hz (A) + 2CH, 1JCH 143 Hz
(B)], 113.44 [2CBr (B)], 113.48 [2CBr (A)], 126.96
(2CH, Ph), 127.01 (2CH, Ph), 127.09 [4CH, Ph (A)],
127.15 [2CH+2CH, Ph (A+B)], 128.67 [4CH+4CH, Ph
(A+B)], 139.90 [2C, Ph (B)], 139.99 [2C, Ph (A)], 147.65
[2C= (B)], 147.78 [2C= (A)]. Found, %: C 59.65; H 4.80.
C22H20Br2. Calculated, %: C 59.49; H 4.54.
1JCH 136 Hz), 26.59 (CH2), 26.79 (CH2), 27.57 (CH2),
1
27.70 (CH2), 29.19 (CH2, cyclohexane, JCH 124 Hz),
1
29.68 (CH2, cyclohexane, JCH 125 Hz), 46.26 (CH,
1
1
cyclo-Bu, JCH 134 Hz), 63.88 (CH2O, JCH 140 Hz),
1
76.58 (CHO, JCH 139 Hz), 129.35 (C=), 131.90 (C=).
Mass spectrum, m/z (Irel, %): 209 (2) [M + 1]+, 208 (1)
* Compound XXVII was obtained as a mixture of two regioisomers
at a ratio ~1:1, and each of them consisted of two diastereomers at
a ratio ~1:1. Due to a large number of overlapping signals of
aliphatic protons 1H NMR spectrum is reported without assignment
to isomers. In the 13C NMR spectrum the signals of carbon atoms
of four isomers are indicated without assignment to individual
isomers.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 7 2008

SEDENKOVA et al.
956
[M]+, 207 (1) [M – 1]+, 179 (2), 149 (65) [M – CH2OEt]+,
134 (13) [M – Et2O]+, 133 (22), 121 (44), 107 (68), 93
(70), 81 (78), 73 (100), 67 (73), 55 (80), 45 (96).
metal. Then the reaction mixture was quenched with
20 ml of ice water and extracted with ether (3×10 ml).
The combined ether solution was washed with water
(3×10 ml). The solvent was distilled off, and the residue
was purified by preparative column chromatography.
[2-(1-Ethoxyethyl)cyclobutylidene]cyclopentane
1
(XXXII). Yield 30%. H NMR spectrum, δ, ppm: 1.14 d
(3H, CH3, 3J 6.7 Hz), 1.18 d.d (3H, CH3, 3J 7.0, 6.8 Hz),
1.45–2.60 m (12H), 3.08–3.16 m (1H, CH, cyclo-Bu),
3.39–3.48 m (1H, CH2O), 3.50–3.65 m (1H, CH2O +
1H, CHO). 13C NMR spectrum, δ, ppm: 15.68 (CH3),
15.93 (CH3), 18.82 (CH2), 26.28 (CH2), 26.92 (CH2),
27.84 (CH2), 29.45 (CH2), 29.91 (CH2), 47.66 (CH,
cyclo-Bu), 63.77 (CH2O), 76.44 (CHO), 129.85 (C=),
134.71 (C=). Mass spectrum, m/z (Irel, %): 194 (1) [M]+,
148 (18) [M – OEtH]+, 133 (12),119 (6), 105 (10), 91
(20), 79 (14), 73 (100) [MeCH(OEt)]+, 67 (9), 45 (64),
43 (10), 29 (3).
1,1'-[Ethane-1,2-diylbis(cyclobut-2-ene-3,1-diyl)]-
dibenzene (XXIX). Yield 90%, Rf 0.8 (petroleum ether).
1H NMR spectrum, δ, ppm: 2.42 d (2H, CH2, cyclo-Bu,
2J 13.1 Hz), 2.44 br.s (4H, CH2), 3.06 d.d (2H, CH2,
2
3
cyclo-Bu, J 13.1, J 4.5 Hz), 3.96 br.d (2H, 2CHPh,
3J 4.5 Hz), 6.12 br.s (2H, 2CH=), 7.27–7.43 m (10H,
2Ph). 13C NMR spectrum, δ, ppm: 28.32 (2CH2,
1
1JCH 127 Hz), 40.94 (2CH2, cyclo-Bu, JCH 138 Hz),
1
43.52 (2CHPh, JCH 139 Hz), 126.09 (2CH, Ph,
1
1JCH 159 Hz), 126.70 (4CH, Ph, JCH 156 Hz), 128.34
1
1
(4CH, Ph, JCH 161), 130.32 (CH=, JCH 168), 144.35
(2C, Ph), 150.34 (2C=). Mass spectrum MALDI-TOF:
m/z 287 [M + 1]+.
[2-(1-Ethoxyethyl)cyclobutylidene]cyclobutane
1
(XXXIII). Yield 58%. H NMR spectrum, δ, ppm: 1.12 d
(3H, CH3, 3J 6.1 Hz), 1.19 d.d (3H, CH3, 3J 7.1, 6.8 Hz),
1.67–2.75 m (10H), 3.01–3.09 m (1H, CH, cyclo-Bu),
3.44–3.54 m (3H, CH2O + CHO). 13C NMR spectrum,
δ, ppm: 15.71 (CH3), 16.17 (CH3), 17.35 (CH2), 19.42
(CH2), 26.19 (CH2), 29.24 (CH2), 29.70 (CH2), 47.62
(CH, cyclo-Bu), 63.75 (CH2O), 77.01 (CHO), 126.27
(C=), 128.31 (C=). Mass spectrum, m/z (Irel, %): 181 (1)
[M + 1]+, 164 (5), 138 (7), 137 (13), 123 (6), 122 (8),
121 (5) [M – CH2OEt]+, 109 (8), 108 (6), 95 (10), 93 (9),
81 (5), 79 (8), 73 (100), 45 (46), 41 (11), 29 (5).
1,1'-Ethane-1,2-diylbisspiro[3.5]non-1-ene (XXX).
1
Yield 83%. H NMR spectrum, δ, ppm: 1.11–1.54 m
(20H), 2.03 br.s (4H, CH2), 2.06 br.s (4H, CH2),
5.65 br.s (2H, 2CH=). 13C NMR spectrum, δ, ppm: 23.60
(2CH2, 1JCH 127 Hz), 24.20 (4CH2, 1JCH 126 Hz), 25.85
(2CH2, 1JCH 124 Hz), 34.87 (4CH2, 1JCH 124 Hz), 39.38
1
(2CH2, cyclo-Bu, JCH 135 Hz), 49.17 (2C), 122.90
1
(2CH=, JCH 168 Hz), 159.03 (2C=). Mass spectrum,
m/z (Irel, %): 270 (12) [M]+, 242 (8), 230 (12), 229 (100),
228 (27), 188 (11), 187 (17), 175 (12), 174 (57), 162
(10), 161 (57), 148 (22), 147 (21), 133 (18), 119 (25),
107 (36), 106 (26), 105 (30), 93 (92), 91 (68), 81 (57),
79 (74), 77 (38), 67 (65), 55 (36), 53 (11), 41 (34).
1-Bromo-2-(1-bromocyclopropyl)cyclobutene
(XXXIV) [1]. Yield 77%, Rf 0.3 (petroleum ether).
1H NMR spectrum, δ, ppm: 1.25–1.31 m (2H, CH2, cyclo-
Pr), 1.37–1.41 m (2H, CH2, cyclo-Pr), 2.59–2.62 m (2H,
CH2, cyclo-Bu), 2.63–2.69 m (2H, CH2, cyclo-Bu).
13C NMR spectrum, δ, ppm: 16.16 (2CH2, cyclo-Pr),
25.46 (CBr, cyclo-Pr), 30.59 (CH2), 33.45 (CH2), 108.23
(CBr=), 146.15 (C=).
The study was carried out under a financial support
of the Russian Academy of Sciences (program no. 1
“Theoretical and experimental study of the nature of the
chemical bond and the mechanisms of the most important
chemical reactions and processes,” Division of Chemistry
and Material Science) and of a grant of the President of
the Russian Federation (NSh 5538.2008.3).
7,7'-Methanediylidenebisbicyclo[4.1.0]heptane
1
(XXXV). Yield 90%. H NMR spectrum, δ, ppm: 1.23–
1.47 m (8H), 1.77–1.93 m (8H), 1.98–2.05 m (4H).
13C NMR spectrum, δ, ppm: 18.86 (2CH), 18.99 (2CH),
21.10 (2CH2), 21.22 (2CH2), 23.33 (2CH2), 23.65
(2CH2), 89.39 (2C=), 173.65 (=C=). Mass spectrum
MALDI-TOF: m/z 200 [M]+.
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