Synthesis of 1,2,3,4,5,6,7-Heptasubstituted Cycloheptatrienes through Cycloaddition Reactions of Substituted Cyclopentadienones

Article abstract of DOI:10.1002/ejoc.201600516

Two schemes for synthesizing heptasubstituted cycloheptatrienes with various substituents in the ring are suggested. The first method is based on cycloaddition of 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone with substituted cyclopropenes and allows cycloheptatrienes containing two or three electron-withdrawing substituents in the molecule to be obtained. The second method employs a cascade reaction between a substituted cyclopentadienone and appropriate vinyldiazoacetates. It allows the number of electron-withdrawing substituents to be increased to five. In all cases, heptasubstituted cycloheptatrienes are formed as just one of the possible isomers.

Full text of DOI:10.1002/ejoc.201600516

DOI: 10.1002/ejoc.201600516
Full Paper
Synthesis of Carbocycles
Synthesis of 1,2,3,4,5,6,7-Heptasubstituted Cycloheptatrienes
through Cycloaddition Reactions of Substituted
Cyclopentadienones
Dmitry N. Platonov,[a] Aleksandr Yu. Belyy,[a] Ivan V. Ananyev,[b] and Yury V. Tomilov*[a]
Abstract: Two schemes for synthesizing heptasubstituted cy- to be obtained. The second method employs a cascade reaction
cloheptatrienes with various substituents in the ring are sug- between a substituted cyclopentadienone and appropriate vin-
gested. The first method is based on cycloaddition of 2,5-di- yldiazoacetates. It allows the number of electron-withdrawing
methoxycarbonyl-3,4-diphenylcyclopentadienone with substi- substituents to be increased to five. In all cases, heptasubsti-
tuted cyclopropenes and allows cycloheptatrienes containing tuted cycloheptatrienes are formed as just one of the possible
two or three electron-withdrawing substituents in the molecule isomers.
Introduction
tives (bromomaleonitrile, methyl 4,4,4-trifluorobut-2-ynoate)
failed. Therefore, to synthesize heptasubstituted cycloheptatri-
enes, we tried to use an approach employed previously to syn-
thesize heptaphenylcycloheptatriene[3a] by cycloaddition of
1,2,3-triphenylcyclopropene to tetraphenylcyclopentadienone.
In this case, we intended to use substrates already containing
electron-withdrawing groups in the molecules.
To date, in addition to this method, there are two schemes
of synthesis of polysubstituted cycloheptatrienes that, only with
some justifications, can be called synthetic methods. The first is
the cycle extension of substituted benzenes in the reactions
with diazo compounds, which allows predominantly cyclohep-
tatrienes with donor substituents in the ring to be synthesized
as a mixture of isomers.[3b] Another method is the reaction of
cyclopropenes with thiophene 1,1-dioxide, which is also used
mainly for the synthesis of cycloheptatrienes with donor sub-
stituents.[3c]
Previously,[1] we used a cascade reaction between methyl diazo-
acetate and dimethyl bromomaleate in the presence of pyridine
in a synthesis of 1,2,3,4,5,6,7-hepta(methoxycarbonyl)cyclohep-
tatriene (HMCC). This unique molecule has three types of reac-
tion centers, thus a series of stereo- and regioselective synthe-
ses of fused and cage carbo- and heterocyclic compounds can
be synthesized on its basis. The most interesting of them are
shown in Scheme 1.[2]
Studies on the structures of HMCC and the stable anion
formed from it[1] have shown that the reactivity of this molecule
is determined, to a considerable extent, by the presence of
seven electron-withdrawing groups that on the one hand, stabi-
lize the anion, and, on the other hand, impart the usual electro-
philic nature to one of the ring double bonds that is not in-
volved in conjugation. In this case, the majority of reactions,
both with electrophiles and with nucleophiles, involve the
HMCC anion.[2]
In view of the unusual type of HMCC reactivity, it seemed
interesting to perform syntheses of other representatives of
heptasubstituted cycloheptatrienes containing a few electron-
withdrawing groups in the molecule, including groups other
than CO2Me. Unfortunately, numerous attempts to perform cas-
cade reactions of HMCC analogues by following a similar proto-
col from other diazo compounds (diazoacetone, diazoacetoni-
trile, 2-diazo-1,1,1-trifluoroethane) and bromomaleate deriva-
Results and Discussion
Reaction of Electron-Withdrawing Cyclopentadienones
with Cyclopropenes
To obtain heptasubstituted cycloheptatrienes as similar as pos-
sible to HMCC, i.e., containing the maximum possible number
of electron-withdrawing groups, we originally chose the clear-
est scheme, which included a sequence of Diels–Alder reactions
between substituted cyclopentadienones and cyclopropenes
followed by decarbonylation of the intermediate bicyclic ad-
duct.
[a] N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation
E-mail: tom@ioc.ac.ru
http://zioc.ru
Dimethyl and diethyl 2-oxo-4,5-diphenylcyclopenta-3,5-di-
ene-1,3-dicarboxylates (1a,b) are the most readily available sta-
ble cyclopentadienones. They can be easily obtained from the
corresponding acetone-1,3-dicarboxylate and benzil.[4] The fol-
lowing cyclopropenes were synthesized by using reported tech-
[b] A. N. Nesmeyanov Institute of Organoelement Compounds, Russian
Academy of Sciences,
28 Vavilov st., 119991 Moscow, Russian Federation
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under http://dx.doi.org/10.1002/ejoc.201600516.
Eur. J. Org. Chem. 0000, 0–0
1
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Scheme 1. Main chemical reactions based on HMCC.
niques: 1,2,3-triphenylcyclopropene (2a),[5] methyl 2,3-di- propenes 2a–c in refluxing p-xylene made it possible to synthe-
methyl- (2b),[6] and methyl 2,3-diphenylcycloprop-2-ene-1- size substituted cycloheptatrienes 3–6 containing up to three
carboxylates (2c).[6] The reaction of dienes 1a,b with cyclo- ester groups in a molecule in up to 78 % yield (Scheme 2).
Scheme 2. Formation of substituted cycloheptatrienes based on cyclopentadienones 1 and cyclopropenes 2.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
2
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Figure 1. ORTEP-drawings for cycloheptatrienes 3a (left), 5 (center), and 6 (right).
When we were selecting this method for the synthesis of tadienone 1a with the known dimethyl 2-(trifluoromethyl)cyclo-
polysubstituted cycloheptatrienes, we did not expect that if var- propene-1,3-dicarboxylate (8),[7] containing three electron-with-
ious substituents are present in the ring, the target products drawing substituents. Unfortunately, because of the electron-
would be formed regioselectively as a single isomer. Neverthe- deficient nature of both the diene and dienophile, no reaction
less, both X-ray single-crystal analysis of compounds 3a, 5, and between them was observed. In view of this, it became neces-
6 (Figure 1) and 1H and 13C NMR spectra obtained for solutions sary to search for alternative methods for synthesizing cyclo-
of compounds 3–6 in CDCl3 unambiguously indicated that hep- heptatrienes with a large number (more than three) of electron-
tasubstituted cycloheptatrienes with fixed positions of double withdrawing substituents in the ring.
bonds in the ring were formed. In all cases, the only ring proton
was localized at the carbon atom containing an ester group.
Reaction of Vinyldiazoctetates with Cyclopentadienones
However, the fact that this proton strictly appears at a specific
position in the presence of several ester groups at various posi-
tions, was unexpected.
For example, the reaction of cyclopentadienone 1a with cy-
clopropene 2b gave only cycloheptatriene 3a, although, ac-
cording to the probable scheme of the reactions, symmetric
isomer 3b would be expected to be formed. In fact, the reaction
of the same cyclopentadienone 1a with cyclopropene 2c con-
taining phenyl groups instead of methyl groups gave the ex-
pected symmetric cycloheptatriene 4.
The search for new approaches to the synthesis of polysubsti-
tuted cycloheptatrienes was based on a study by Wang et al.[7]
dealing with a synthesis of 3-trifluoromethylated 8-oxabicy-
clo[3.2.1]octa-2,6-dienes. It has been shown that the reaction of
vinyldiazoacetate 9a with 2,5-dimethylfuran in benzene cata-
lyzed by dirhodium tetraacetate gives, apart from cyclopropene
8, mainly bicyclic compound 10 because of a bimolecular reac-
tion of the rhodium intermediate (Scheme 3). The formation of
vinylcyclopropane 11 is the key step in this process. It then
readily undergoes a [3,3]-sigmatropic rearrangement to give 8-
oxabicyclo[3.2.1]octa-2,6-diene structure 10.
The two-stage scheme with the Diels–Alder reaction as the
first stage can be confirmed by the reaction of cyclopentanedi-
enone 1b with cyclopropene 2b at room temperature. Based
1
on H and 13C NMR spectroscopic data, formation of adduct 7
was detected. Furthermore, the latter was converted into substi-
tuted cycloheptatriene-1,3,5-tricarboxylate 6 with the same ar-
rangement of double bonds in the ring found in the similar
compound 3a (Scheme 2). We failed to isolate pure adduct 7
because of its high lability. In this case, monitoring of the reac-
tion mixture by NMR spectroscopy has shown that the maxi-
mum level of formation of 7 occurs in the reaction of 1b with
2b at 25 °C for 30 min.
It is noted that, in almost all syntheses performed, we ob-
served the formation of one among several possible isomers.
However, according to preliminary data obtained in the study
of CH-acidity of substituted cycloheptatrienes it can be as-
sumed that not all the obtained isomers are thermodynamically
favorable. The study of this problem requires more attention; in
particular, the involvement of quantum-chemical calculations,
which are planned to be implemented in the near future.
Scheme 3. Reaction of diazo compound 9a with 2,5-dimethylfuran in the
presence of Rh2(OAc)4.
We assumed that if we use cyclopentadienone 1a in this
procedure instead of a furan, decarbonylation of the bicyclic
ketone would give a cycloheptatriene containing five electron-
withdrawing groups in the ring. Although it was hard to expect
To increase the number of electron-withdrawing substituents that the rhodium carbenoid would react with the electron-defi-
in the target molecule, we performed the reaction of cyclopen- cient cyclopentadienone 1, the possibility of 1,3-dipolar cyclo-
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
3
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
addition of 9a to 1 followed by dediazotization of the resulting ciently high yield of the corresponding cycloheptatriene, which
pyrazoline to give the expected vinylcyclopropane remained. required an optimization of the reaction conditions. As it turned
This scheme was also attractive because of the fact that reac- out, much better results were obtained when the reaction was
tions of 1,3-dipolar cycloaddition of diazo compounds to cyclo- carried out in dioxane under reflux conditions. In this case, not
pentadienone are known. These reactions gave pyrazolines, only the temperature decreased considerably, but also the reac-
which actually eliminated nitrogen to give cyclopropanes on tion time decreased (from 8–10 h in xylene to 4 h in dioxane).
heating to reflux in benzene.[4]
In fact, the reaction of 1a with diazo compounds 9b,c in diox-
ane heated to reflux gave cycloheptatrienes 13a,b in 78 and
81 % yields, respectively (Scheme 5). It should be noted that
the use of Rh2(OAc)4 in this process significantly reduced the
yield of cycloheptatriene 13a (up to 35 %), which indicates the
noncarbene path of its formation.
To check this hypothesis, we studied the reaction of cyclo-
pentadienone 1a with vinyldiazoacetate 9b by heating the mix-
ture to reflux in xylene. In fact, this reaction resulted in a hepta-
substituted cycloheptatriene, but the positions of substituents
in it were found to differ from those we expected based on the
reactions of cyclopentadienone 1 with cyclopropenecarboxy-
lates 2b,c (Scheme 2) or by analogy with the conversion of
vinylcyclopropane 11 (Scheme 3); that is, instead of the ex-
pected cycloheptatriene 12 with symmetric arrangement of
substituents (neglecting the positions of double bonds in the
ring), cycloheptatriene 13a was formed (Scheme 4), as followed
unambiguously from the data of X-ray single-crystal analysis
(Figure 2).
Scheme 5. Reaction of diazo compounds 9b,c with cyclopentadienone 1a in
dioxane at reflux.
An interesting result was obtained in the reaction of cyclo-
pentadienone 1a with cyano-substituted vinyldiazoacetate 9d.
In this case, along with cycloheptatriene 13c, approximately the
same amount of heptasubstituted tricyclo[3.2.1.02,4]oct-6-en-8-
one, exo-14, was isolated (Scheme 6). The structures of these
compounds were confirmed by X-ray single-crystal analysis
(Figure 3).
Scheme 4. Reaction of diazo compound 9b with cyclopentadienone 1a.
Scheme 6. Reaction of diazo compound 9d with cyclopentadienone 1a.
Furthermore, we have shown that photolysis of exo-14 in
dioxane at 25 °C is accompanied by its decarbonylation to give
the same cycloheptatriene 13c. Based on these data, it can be
assumed that the formation of the other cycloheptatrienes
13a–c also occur through intermediate generation of tricyclic
adducts 14 (Figure 4). However, the latter are probably formed
as less thermally stable endo isomers (Scheme 6).
Figure 2. ORTEP-drawings for cycloheptatriene 13a.
The results obtained prompted us to undertake a more de-
Thus, the formation of substituted cycloheptatrienes 13 in
tailed study of reactions of substituted vinyldiazoacetates with the reactions of cyclopentadienone 1 with vinyldiazoacetates 9
cyclopentadienones, 1a in particular. To do so, acetyl- and cy- formally matches the [4+2]-cycloaddition of a diene to cyclo-
ano-substituted vinyldiazoacetates 9c,d were also obtained by propene 15. However, taking into consideration that cyclopen-
analogy with the synthesis of 9b.[8] It was found that the reac- tadienone 1 does not react with cyclopropene 8, it is unlikely
tion of 1a with 9c in xylene heated at reflux gave an insuffi- that similar reactions would occur with other cyclopropenes
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
4
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Figure 3. ORTEP-drawings for cycloheptatriene 13c (left) and tricyclic compound exo-14 (right).
Conclusions
We have suggested two regioselective methods for the synthe-
sis of heptasubstituted cycloheptatrienes with several electron-
withdrawing substituents in the ring. One of the methods in-
volves the reaction of dialkyl 2-oxo-4,5-diphenylcyclopenta-3,5-
diene-1,3-dicarboxylates 1 with cyclopropenes containing no
electron-withdrawing substituents at the double bond. The sec-
ond method, which is fundamentally new, involves the reaction
of cyclopentadienones 1 with vinyldiazoacetates that, unlike cy-
clopropenes, should contain electron-withdrawing substituents
at each carbon atom. In the latter case, the resulting cyclohep-
tatrienes contain five electron-withdrawing substituents in the
ring.
Figure 4. Possible transition state during the formation of the tricyclic struc-
ture.
containing three electron-withdrawing substituents in a mol-
ecule. Most likely, the reaction actually starts with formation of
a C–C bond between the most reactive α-carbon atom of the
diazo compound and the C(1) atom of the cyclodiene. Further-
more, a nitrogen-containing molecule is eliminated with simul-
taneous rearrangement of the carbon moiety, which results in
the formation of two new C–C bonds; that is, formation of a
three-membered ring and a norbornene structure. Apparently,
in this case, the state in which the terminal end of the vinyl
group in the diazo compound is remote from the carbonyl
group of the cyclopentadienone is preferable and eventually
results in a tricyclic structure with endo-orientation of the three-
membered ring.
The ease of decarbonylation in the case of endo-isomers is
in good agreement with the regularities of decarbonylation of
isomeric tricyclo[3.2.1.02,4]oct-6-en-8-ones (16).[9] In fact, the
endo-isomer is readily decarbonylated even at 35 °C, whereas
exo-16 loses a CO molecule at the same rate only at 150 °C
(Scheme 7).
Experimental Section
General: 1H and 13C NMR spectra were recorded with a 300 and
75.5 MHz NMR spectrometer for solutions in CDCl3 containing
0.05 % of Me4Si as an internal standard. 19F NMR spectra were re-
corded with a 188.3 MHz instrument and δF values are quoted rela-
tive to CCl3F. Assignment of signals and determination of the struc-
ture compounds formed were made using COSY, HMBC, HSQC cor-
relation spectra. High-resolution mass spectra were obtained with a
Bruker micrOTOF II instrument (ESI, positive or negative ion modes,
capillary voltage 4500 V). All chemical reagents and solvents were
purchased from commercial sources and used without additional
purification.
X-ray Diffraction Experiments were carried out with a SMART APEX
II CCD diffractometer, using graphite monochromated Mo-Kα radia-
tion (l = 0.71073 Å, ω-scans) at 120 K. The structures were solved
by direct methods and refined by full-matrix least-squares against
F2 in anisotropic approximation for non-hydrogen atoms. Hydrogen
atom positions were calculated. All hydrogen atoms were refined in
isotropic approximation in the riding model. All calculations were
performed by using SHELX-97 and SHELX-2014 software.[10]
CCDC 1475655 (for 3a), 1475656 (for 5), 1475657 (for 6), 1475658
(for 13a), 1475659 (for 13c), and 1475660 (for exo-14) contain the
Scheme 7. Conditions for the CO elimination from exo- and endo-tricy-
clo[3.2.1.02,4]oct-6-en-8-ones.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
5
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre.
(ESI+): m/z calcd. for C27H20F3NO6Na+ [M + Na]+ 534.1140; found
534.1135.
exo-Trimethyl 3-Cyano-8-oxo-6,7-diphenyl-4-(trifluoromethyl)-
tricyclo[3.2.1.02,4]oct-6-ene-1,2,5-tricarboxylate (exo-14): Color-
Trimethyl
2,4-Dimethyl-6,7-diphenylcyclohepta-1,3,6-triene-
less crystals; m.p. 185–187 °C. IR (KBr): ν = 3029, 2959, 2255, 1826,
˜
1,3,5-tricarboxylate (3a): A solution of cyclopentadienone 1a
(1.84 g, 5.3 mmol) and cyclopropene 2a (1.0 g, 8 mmol) was heated
to reflux in xylene (8 mL) for 16 h. The solvent was evaporated in
vacuo, the oily residue was dissolved in methanol (4 mL) and the
solution was left to stand overnight at 0 °C. The precipitate was
filtered and washed with a mixture of petroleum and diethyl ether
(1:1) to give 3a (1.77 g, 78 %) as a white solid; m.p. 151–153 °C. IR
1763, 1742, 1439, 1315, 1276, 1221, 1171, 996, 978, 702 cm–1
.
1H
NMR (300 MHz, CDCl3): δ = 7.40–7.00 (m, 10 H), 3.79 (s, 3 H), 3.78
(s, 3 H), 3.72 (s, 3 H), 2.80 (s, 1 H) ppm. 13C NMR (75.5 MHz, CDCl3):
δ = 175.8, 163.6, 163.1, 162.6, 144.6, 141.7, 132.4, 131.7, 130.1, 128.7,
1
128.1, 122.5 (q, JC,F = 277.9 Hz), 111.6, 71.8, 70.3, 53.5, 53.3, 53.2,
46.0 (q, 2JC,F = 36.1 Hz), 45.1, 19.4 ppm. 19F NMR (282.4 MHz, CDCl3):
δ = –59.23 ppm. HRMS (ESI+): m/z calcd. for C28H20F3NO7Na+ [M +
Na]+ 562.1090; found 562.1084.
(KBr): ν = 2982, 2952, 1736, 1712, 1444, 1249, 1231, 1220, 1189,
˜
1
1080, 1047, 1020, 702 cm–1. H NMR (300 MHz, CDCl3): δ = 7.13 (s,
5 H), 7.04–7.08 (m, 3 H), 6.96–7.01 (m, 2 H), 4.19 (s, 1 H), 3.84 (s, 3
H), 3.67 (s, 3 H), 3.29 (s, 3 H), 2.08 (s, 3 H), 1.99 (s, 3 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 170.5, 168.6, 168.2, 141.2, 140.8, 139.8,
138.5, 135.8, 135.1, 131.1, 129.9, 129.7, 128.1, 127.4, 127.3, 127.0,
57.8, 52.3, 52.0, 51.5, 23.2, 19.5 ppm. HRMS (ESI+): m/z calcd. for
C27H26O6Na+ [M + Na]+ 469.1627; found 469.1622.
Supporting Information (see footnote on the first page of this
article): All experimental details can be found in the supporting
information. This includes experimental procedures, characteriza-
1
tion data, and copies of H, 13C and 19F NMR spectra.
Acknowledgments
Tetramethyl 6,7-Diphenyl-4-(trifluoromethyl)cyclohepta-1,4,6-
triene-1,2,3,5-tetracarboxylate (13a): A solution of cyclopentadi-
enone 1a (1.15 g, 3.3 mmol) and diazo compound 9a (1.0 g,
3.9 mmol) in dioxane (20 mL) was heated to reflux for 9.5 h. A new
portion of 9a (0.17 g, 0.7 mmol) was then added and the reaction
mixture was additionally heated to reflux until the disappearance
of the orange color, which is typical for cyclopentadienone 1a
(about 2 h). The solvent was evaporated by using a rotary evapora-
tor, the residue was dissolved in methanol (4 mL) and the formed
solution was left to stand overnight at 0 °C. The precipitate was
filtered and washed with a mixture of petroleum and diethyl ether
(1:1) to give 13a (1.40 g, 78 %) as colorless crystals; m.p. 154–156 °C.
High-resolution mass spectra were recorded in the Department
of Structural Studies of the Zelinsky Institute of Organic Chemis-
try, Moscow.
Keywords: Small ring systems · Medium-ring compounds ·
Diazo compounds · Domino reactions · Cycloaddition
[1] Yu. V. Tomilov, D. N. Platonov, R. F. Salikov, G. P. Okonnishnikova, Tetrahe-
dron 2008, 64, 10201–10206.
[2] a) Yu. V. Tomilov, D. N. Platonov, G. P. Okonnishnikova, Tetrahedron Lett.
2009, 50, 5605–5608; b) D. N. Platonov, G. P. Okonnishnikova, Yu. V. Tomi-
lov, Mendeleev Commun. 2010, 20, 83–85; c) Yu. V. Tomilov, D. N. Pla-
tonov, E. V. Shulishov, G. P. Okonnishnikova, A. A. Levina, Tetrahedron
2015, 71, 1403–1408; d) D. N. Platonov, G. P. Okonnishnikova, R. A. Novi-
kov, K. Yu. Suponitsky, Yu. V. Tomilov, Tetrahedron Lett. 2014, 55, 2381–
2384; e) Yu. V. Tomilov, D. N. Platonov, G. P. Okonnishnikova, O. M. Nefe-
dov, Russ. Chem. Bull. 2010, 59, 1387–1392; f) Yu. V. Tomilov, D. N. Pla-
tonov, E. V. Shulishov, G. P. Okonnishnikova, Tetrahedron 2013, 69, 6855–
6860.
IR (KBr): ν = 2958, 1736, 1724, 1434, 1277, 1253, 1181, 1169, 1125,
˜
1
1097, 702 cm–1. H NMR (300 MHz, CDCl3): δ = 7.10–6.91 (m, 10 H),
5.16 (s, 1 H), 3.85 (s, 6 H), 3.46 (s, 3 H), 3.44 (s, 3 H) ppm. 13C NMR
(75.5 MHz, CDCl3): δ = 168.9, 166.4, 165.1, 163.8, 143.3, 142.7, 141.9,
136.0, 130.0, 127.8, 125.1, 121.5 (q, 1JC,F = 274.5 Hz), 123.9 (q, 2JC,F
=
37.5 Hz), 53.4, 53.3, 52.6, 52.4, 41.4 ppm. 19F NMR (282.4 MHz,
CDCl3): δ = –63.60 ppm. HRMS (ESI+): m/z calcd. for C28H23F3O8Na+
[M + Na]+ 567.1243; found 567.1228.
[3] a) R. Breslow, H. W. Chang, J. Am. Chem. Soc. 1965, 87, 2200–2203; b)
A. J. Anciaux, A. Demonceau, A. F. Noels, A. J. Hubert, R. Warin, P. H.
Teyssie, J. Org. Chem. 1981, 46, 873–876; c) D. N. Reinhoudt, M. P. Smael,
W. J. M. Van Tilborg, J. P. Visser, Tetrahedron Lett. 1973, 14, 3755–3758.
[4] B. Eistert, A. J. Thommen, Chem. Ber. 1971, 104, 3048–3061.
[5] R. Breslow, P. Dowd, J. Am. Chem. Soc. 1963, 85, 2729–2735.
[6] C. Li, H. Zhang, J. Feng, Y. Zhang, J. Wang, Org. Lett. 2010, 12, 3082–
3085.
[7] Y. Wang, S. Zhu, G. Zhu, Q. Huang, Tetrahedron 2001, 57, 7337–7342.
[8] a) M. Guillaume, Z. Janousek, H. G. Viehe, Synthesis 1995, 920–922; b) M.
Supurgibekov, G. K. S. Prakash, V. A. Nikolaev, Synthesis 2013, 45, 1215–
1226.
Reaction of Cyclopentadienone 1a with Diazobutenoate 9c: A
solution of cyclopentadienone 1a (1.19 g, 3.4 mmol) and diazo com-
pound 9c (0.90 g, 4.1 mmol) in dioxane (18 mL) was heated to
reflux for 6 h. The solvent was evaporated by using a rotary evapo-
rator, and the residue was separated by chromatography on silica
gel (CHCl3/EtOAc, 20:1) to give cycloheptatriene 13c (0.75 g, 43 %)
and tricyclo[3.2.1.02,4]octen exo-14 (0.75 g, 41 %).
Trimethyl 7-Cyano-3,4-diphenyl-6-(trifluoromethyl)cyclohepta-
1,3,5-triene-1,2,5-tricarboxylate (13c): Colorless crystals; m.p.
165 °C (decomp.). IR (KBr): ν = 2956, 1737, 1725, 1632, 1619, 1491,
˜
[9] B. Halton, M. A. Battiste, R. Rehberg, C. L. Deyrup, M. E. Brennan, J. Am.
Chem. Soc. 1967, 89, 5964–5965.
[10] a) G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112; b) G. M. Shel-
drick, Acta Crystallogr., Sect. C 2015, 71, 3.
1437, 1281, 1242, 1230, 1188, 1127, 1085, 765, 702 cm–1
.
1H NMR
(300 MHz, CDCl3): δ = 7.05–7.17 (m, 10 H), 5.44 (s, 1 H), 3.87 (s, 3
H), 3.49 (s, 3 H), 3.43 (s, 3 H) ppm. 13C NMR (75.5 MHz, CDCl3): δ =
165.4, 164.1, 162.2, 144.3, 143.7, 143.2, 138.7, 135.4, 135.5, 129.7,
128.2, 127.8, 120.8 (q, 1JCF = 277.5 Hz), 120.4, 115.3, 53.8, 52.9, 52.7,
26.8 ppm. 19F NMR (282.4 MHz, CDCl3): δ = –63.31 ppm. HRMS
Received: April 26, 2016
Published Online: ■
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Synthesis of Carbocycles
D. N. Platonov, A. Yu. Belyy,
I. V. Ananyev, Yu. V. Tomilov* ......... 1–7
Synthesis of 1,2,3,4,5,6,7-Heptasub-
stituted Cycloheptatrienes through
Cycloaddition Reactions of Substi-
tuted Cyclopentadienones
Regioselective convergent three- to diphenylcyclopenta-3,5-diene-1,3-di-
four-step synthesis of heptasubsti- carboxylate and 2,3-dimethyl(2,3-di-
tuted cycloheptatrienes with a wide phenyl)cycloprop-2-ene-1-carboxyl-
range of substituents on the cycle was ates or 2-diazo-3-(trifluoromethyl)-
carried out, starting from 2-oxo-4,5- butenoates.
DOI: 10.1002/ejoc.201600516
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim