Synthesis and radical polymerization of various 2-cyclopropylacrylates

Article abstract of DOI:10.1002/ejoc.200400132

Fourteen new alkyl 2-cyclopropylacrylates 1a-n with various substituents R¹-R⁵ were synthesized from readily available precursors by applying standard transformations such as cyanohydrin formation from an aldehyde, alcoholysis to an α-hydroxycarboxylic ester, oxidation and Wittig methylenation of an α-oxocarboxylic ester. Overall yields ranged from 33 to 54%. A new method for the hydrolysis of dimethyl cyclopropanedicarboxylates to the corresponding half-esters was developed. The α-oxocarboxylates 7g-n were prepared by dirhodium tetraacetate catalyzed cyclopropanation of alkenes 8g-n with methyl or ethyl diazopyruvate in 32-58% yield. The monomers 1a-n were characterized by ¹H, ¹³C NMR spectroscopy, mass spectrometry and elemental analysis. The radical homopolymerizations of 1a-n were carried out with 2,2′- azabisisobutyronitrile (AIBN) as initiator in chlorobenzene at 65 °C. The highest polymer yields were obtained in the polymerizations of If and 1h or 1k and 11, i.e. from monomers with an annelated five- or six-membered ring. In the case of 1h and 1k, both the polymer yields (99 and 98%, respectively) and the glass transition temperatures (T_g) of 57 and 93 °C were significantly higher than those observed for the polymer from 1,1-bis(ethoxycarbonyl)-2-vinylcyclopropane (DECVCP), which was used as a benchmark for the monomer reactivities in the radical polymerizations of all the vinylcyclopropane derivatives 1a-n. The bicyclic monomers 1h and 1k also demonstrated drastically improved reactivities in the radical copolymerization with methyl methacrylate when compared to DECVCP. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200400132

FULL PAPER
Synthesis and Radical Polymerization of Various 2-Cyclopropylacrylates[‡]
Armin de Meijere,*[a] Viktor Bagutski,[a] Frank Zeuner,[b] Urs Karl Fischer,[b]
Volker Rheinberger,[b] and Norbert Moszner*[b]
Keywords: Hydrolysis / Cycloaddition / Wittig reaction / Ring-opening polymerization / Copolymerization
Fourteen new alkyl 2-cyclopropylacrylates 1a−n with various
substituents R1−R5 were synthesized from readily available
zene at 65 °C. The highest polymer yields were obtained in
the polymerizations of 1f and 1h or 1k and 1l, i.e. from mono-
precursors by applying standard transformations such as cy- mers with an annelated five- or six-membered ring. In the
anohydrin formation from an aldehyde, alcoholysis to an α-
hydroxycarboxylic ester, oxidation and Wittig methylenation
of an α-oxocarboxylic ester. Overall yields ranged from 33 to
54%. A new method for the hydrolysis of dimethyl cyclopro-
case of 1h and 1k, both the polymer yields (99 and 98%, re-
spectively) and the glass transition temperatures (Tg) of 57
and 93 °C were significantly higher than those observed for
the polymer from 1,1-bis(ethoxycarbonyl)-2-vinylcyclopro-
panedicarboxylates to the corresponding half-esters was de- pane (DECVCP), which was used as a benchmark for the
veloped. The α-oxocarboxylates 7g−n were prepared by di-
rhodium tetraacetate catalyzed cyclopropanation of alkenes
8g−n with methyl or ethyl diazopyruvate in 32−58% yield.
The monomers 1a−n were characterized by 1H, 13C NMR
spectroscopy, mass spectrometry and elemental analysis. The
radical homopolymerizations of 1a−n were carried out with
monomer reactivities in the radical polymerizations of all the
vinylcyclopropane derivatives 1a−n. The bicyclic monomers
1h and 1k also demonstrated drastically improved reactivities
in the radical copolymerization with methyl methacrylate
when compared to DECVCP.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
2,2Ј-azabisisobutyronitrile (AIBN) as initiator in chloroben- Germany, 2004)
Introduction
among other properties, exhibit a high rate of polymeri-
zation and improved mechanical properties.[3] For the latter,
it is important that the corresponding homopolymers of the
2-Vinylcyclopropane-1,1-dicarboxylates are interesting cyclic monomers attain both a high molecular weight and
monomers because they demonstrate less polymerization a glass transition temperature (Tg) higher than ca. 60 °C.
shrinkage than other vinyl monomers, such as methacry- In contrast to other ring-opening low-shrinkage monomers,
lates.[1,2] They undergo radical ring-opening polymeri- such as spiro-orthocarbonates or cyclic ketene acetals, the
zation, resulting in polymers which mainly contain 1,5-di- 2-vinylcyclopropane-1,1-dicarboxylates are stable in the
substituted pent-2-enyl subunits. Low polymerization presence of humidity, acidic and basic impurities, and inor-
shrinkage makes such cyclic monomers attractive as com- ganic fillers. In addition, they show a greater tendency to
ponents of dental adhesives or filling composites. For an undergo radical copolymerization with other vinyl mono-
application in dental composites the monomers should, mers. However, in comparison with methacrylates, 2-vinyl-
cyclopropane-1,1-dicarboxylates are less reactive in the rad-
ical copolymerization,[4] and this restricts their practical ap-
plication. The reactivities of the vinylcylopropanes in the
[‡]
Polymerization of cyclic monomers, 11. Part 10: Ref.[1] For one
of us (A. d. M.), this is to be considered as Part 98 in the series
radical polymerization depend on their structure and there-
fore can be influenced by the number and type of substitu-
ents or the introduction of bicyclic structural units.[2]
Previously, we reported on the synthesis and polymeri-
zation of methyl 2-(bicyclo[3.1.0]hex-1-yl)acrylate, whose
reactivity in radical copolymerization was found to be
higher than that of methyl methacrylate.[1] Here we describe
the synthesis and radical polymerization of both methyl and
ethyl 2-cyclopropylacrylates bearing various substituents
(1aϪe,g) as well as bicyclic methyl or ethyl 2-cyclopro-
pylacrylates (1f,hϪn) with variation in the size of the second
ring (Scheme 1).
‘‘Cyclopropyl Building Blocks for Organic Synthesis’’. Part 97:
S. Wiedemann, K. Rauch, I. Marek, A. de Meijere, Eur. J. Org.
Chem. 2003, 631Ϫ635; Part 96: S. I. Kozhushkov, R. Langer,
D. S. Yufit, J. A. K. Howard, H. Schill, D. Demus, K.
Miyazawa, A. de Meijere, Eur. J. Org. Chem. 2004, 289Ϫ303.
Institut für Organische Chemie der Georg-August-Universität
Göttingen,
[a]
[b]
Tammannstrasse 2, 37077 Göttingen, Germany
Fax: (internat.) ϩ 49-551-399475
E-mail: Armin.deMeijere@chemie.uni-goettingen.de
Ivoclar Vivadent AG,
Bendererstrasse 2, 9494 Schaan, Liechtenstein
Fax: (internat.) ϩ 423-2331279
E-mail: norbert.moszner@ivoclarvivadent.com
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2004, 3669Ϫ3678
DOI: 10.1002/ejoc.200400132
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3669

A. de Meijere, V. Bagutski, F. Zeuner, U. K. Fischer, V. Rheinberger, N. Moszner
FULL PAPER
iodide in acetone, or the substituted formylcyclopropanes
5bϪf, are accessible on large scales. The aldehydes 5b,c were
prepared on a 0.2-mol scale by formylation of the lithiated
methylenecyclopropanes 2b,c with DMF,[6] according to an
improved protocol, in good yields (82 and 66%, respec-
tively). The aldehyde 5e was prepared in 83% yield accord-
ing to a previously reported procedure.[7] For the prep-
aration of aldehydes 5d,f a new saponification protocol for
dimethyl cyclopropanedicarboxylates 3d,f leading to half-
esters 4d,f in high yields and, in the case of 3f, with excellent
regioselectivity, was developed. Thus, the bicyclic gem-dies-
ter 3f was hydrolyzed with lithium hydroxide monohydrate,
suspended in a mixture of tetrahydrofuran and methanol
(4:1), to give only the exo-carboxylic acid 4f in 83% yield,
the configuration of which was also confirmed by an X-ray
crystal structure analysis.[8] The obtained half-esters 4d,f
were smoothly converted into the corresponding aldehydes
5d,f by catalytic hydrogenation of the corresponding acyl
chlorides in the presence of 10% Pd/C and equimolar
amounts of 2,6-lutidine according to an adopted protocol
for a Rosenmund reduction.[9] The aldehydes 5bϪf were
transformed via the respective cyanohydrins, prepared as
described previously,[10] to the corresponding alkyl 2-cyclo-
propyl-2-hydroxyacetates 6bϪf. The cyanohydrins, derived
from 5b,c which could undergo acid-catalyzed side reac-
tions, required milder methanolysis conditions (General
Procedure 2A)[1,11] to yield the respective 2-hydroxyacetates
6b,c in good yields, while the less sensitive cyanohydrins
prepared from 5dϪf were smoothly converted into the α-
hydroxy esters 6dϪf by treatment with anhydrous methanol
saturated with dry HCl at Ϫ20 °C (General Procedure 2B).
It should also be noted that hydrolysis of the intermediate
imino ester hydrochlorides usually required 1Ϫ2 h, while
overnight stirring at ambient temperature was necessary to
completely solvolyze the respective imino ester hydrochlo-
ride to the α-hydroxy ester 6f. This might be caused by for-
mation of an intermediate pyrroline derivative, which would
undergo hydrolysis more slowly than the corresponding
imino ester hydrochloride.
Scheme 1. Variously substituted cyclopropylacrylates 1aϪn synthe-
sized in this work
Results and Discussion
Synthesis of New Monomers
The unsubstituted and the cyclopropane ring-substituted
alkyl 2-cyclopropylacrylates 1aϪn were prepared by Wittig
methylenation of the corresponding alkyl 2-cyclopropyl-2-
oxoacetates, which were synthesized by two different meth-
ods (Scheme 2) depending on the substitution pattern of the
cyclopropane ring.
The first route relies on transformations of functional
groups, which are already attached to the cyclopropane
The synthesized alkyl 2-cyclopropyl-2-hydroxyacetates
ring. The key precursors to compounds 7aϪf, such as po- were oxidized with active manganese dioxide according to
tassium cyclopropyloxoacetate,[5] which is smoothly con- a previously reported protocol,[1,12] to give the respective α-
verted into the methyl ester 7a upon heating with methyl oxoacetates 7bϪf in good yields (71Ϫ88%).
Scheme 2. Synthesis of substituted cyclopropylacrylates 1aϪn; reagents and conditions: i. 1) nBuLi, THF, 0 °C, 1 h, 2) DMF, Ϫ78 Ǟ 0
°C, 30 min, 3) 2  H2SO4, 0 Ǟ 20 °C; ii. LiOH·H2O, MeOH, THF, 20 °C, 24 h; iii. 1) (COCl)2, C6H6, 2 h, 20 °C, 2) H2, 10 wt.% Pd/C,
2,6-lutidine, THF, 12 h, 20 °C; iv. 1) NaCN, NH4Cl, Et2O, H2O, 10 °C, 40 min, 2) HCl, R5OH, Et2O, 2 °C, 16 h (GP 2A) or HCl, R5OH,
Ϫ10 Ǟ 20 °C, 2 h (GP 2B); v. MnO2, Et2O, 20 °C, 6 h; vi. 0.2 mol % [Rh2(OAc)4], CH2Cl2, 16 h; vii. CH3PPh3Br, nBuLi, iPr2NH (GP
5A) or 10 mol % iPr2NH (GP 5B), THF, Ϫ78 Ǟ 20 °C, 12 h or CH3PPh3Br, tBuOK, THF, Ϫ30 Ǟ 20 °C, 16 h (GP 5C); for substituents
R1ϪR5 see Scheme 1
3670
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2004, 3669Ϫ3678

Synthesis and Radical Polymerization of Various 2-Cyclopropylacrylates
FULL PAPER
The α-oxoacetates 7gϪn were prepared by a different propylamide (LDA) in tetrahydrofuran according to the
route in moderate yields (32Ϫ58%) by rhodium() acetate protocol of Wenkert at al.,[13] which had previously been
catalyzed addition of alkyl diazopyruvates to the corre- successfully applied for the methylenation of 7g to 1g, con-
sponding alkenes 8gϪn, according to a protocol adopted verted smoothly compounds 7aϪc,m to the respective acry-
from Wenkert at al.[13]
lates 1aϪc,m in good yields (65Ϫ80%, Table 1).
The methylenation of α-oxoacetates was tested on 7a as
However, even this method has some drawbacks. Genera-
a model compound, by applying various Wittig olefination tion of the ylide with LDA required 2 h of stirring at low
protocols. Thus, the ylide generated from methyltri- temperature (Ϫ40 °C) and 2 h at ambient temperature.
phenylphosphonium bromide with bases such as sodium Moreover, methylenation of α-oxo esters with an additional
hydride in tetrahydrofuran, or with n-butyllithium in tetra- alkoxycarbonyl group turned out to be problematic. Thus,
hydrofuran or diethyl ether,[5] led only to partial conversion attempts to methylenate 7d according to this protocol gave
of 7a providing the α-methyleneacetate 1a in moderate the desired product 1d only in moderate yield (44%). There-
yields (Ͻ 55%). This may be attributed to partial enoliz- fore, an improved methylenation protocol was developed. It
ation, since about 40% of 7a could be recovered from the turned out that generation of the ylide from methyltri-
reaction mixture. Reaction of 7a with the ylide generated phenylphosphonium bromide with n-butyllithium in the
from methyltriphenylphosphonium bromide with sodium presence of 5Ϫ10 mol % of diisopropylamine proceeds at
hydride in dimethyl sulfoxide or with potassium tert-but- the same rate as without it, and provides a homogeneous
oxide in tetrahydrofuran gave only mixtures of products. It ylide solution just upon warming the reaction mixture from
was found that only the ylide generated with lithium diiso- Ϫ78 °C to ambient temperature over 1 h. On the other
Table 1. The various 2-cyclopropylacrylates 1aϪn prepared; for details see Schemes 1 and 2
[a]
[b]
[c]
Method A: CH3PPh3Br, nBuLi, iPr2NH (GP 5A). Method B: 10 mol % iPr2NH, THF, Ϫ78 Ǟ 20 °C, 12 h (GP 5B). Method C:
CH3PPh3Br, tBuOK, THF, Ϫ30 Ǟ 20 °C, 16 h (GP 5C).
Eur. J. Org. Chem. 2004, 3669Ϫ3678
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A. de Meijere, V. Bagutski, F. Zeuner, U. K. Fischer, V. Rheinberger, N. Moszner
FULL PAPER
hand, the ylide thus generated smoothly reacts with an oxo plained on this basis. The replacement of the methylene hy-
group at Ϫ50 °C, while ester groups are completely inert drogen atoms in 1b by an ethylene bridge leads to monomer
under these conditions. Apparently, a catalytic amount 1c in which the former radical-accessible methylene group
(5Ϫ10 mol %) of diisopropylamine is sufficient to repro- is changed to the corresponding tetrasubstituted double
tonate the enolate formed by deprotonation of the α-oxo bond. In contrast to a vinyl group, tetrasubstituted double
ester. It is remarkable that the added amine did not lead to bonds are not usually capable of adding initiating radicals
1
any side reactions such as a Michael addition to the and could be therefore detected in poly-1c by H and 13C
resulting acrylate, or aminolysis of the ester group, and the NMR spectroscopy.
yield of 1d was increased to 79%.
Of course, this improved protocol may be used for the
methylenation of compounds 7aϪc,g,m to furnish better
yields of 1aϪc,g,m, which had been synthesized before the
Table 2. Polymerization of monomers 1aϪe,g and DECVCP (2.0
mol/L) in chlorobenzene and in the presence of AIBN (2.0 mol %)
at a temperature of 65 °C with a polymerization time (tP) of 15 h
new procedure was developed. Thus, ethyl 2-methylene-
¯
¯
Monomer Polymer yield (%) Mn [g/mol] Mw [g/mol] Tg [°C]
cyclopropylacrylate 1b (R5 ϭ Et) was obtained in 75% yield
from oxo ester 7b (R5 ϭ Et) by this improved procedure
compared to the 65% yield obtained for the methyl ester 7b
(R5 ϭ Me), achieved with the previously applied protocol.
In this respect, the attempted methylenation of 7f gave
an unusual result in that recovery of the starting material
was predominant. Most probably, complexation of the oxo
carbonyl and the endo-methoxycarbonyl groups of 7f with
a lithium cation, forming a six-membered cyclic chelate,
leads to an orientation of the oxo carbonyl group which
sterically disfavors addition of the bulky ylide. Indeed,
methylenation of 7f was successful (78% yield) with so-
called ‘‘salt-free’’ ylide, generated from methyltri-
phenylphosphonium bromide with potassium tert-butoxide
in tetrahydrofuran.
1a
1b
1c
1d
1e
1g
71
15
118900[a]
5300
86300
Ϫ[c]
2900
Ϫ
419000
7800
156100
Ϫ
8500
Ϫ
98
54
118
53
Ϫ
62
40
43
67[b]
17
42[b]
DECVCP 95
67500
128700
[a] Polymer was not completely soluble in THF. [b] Polymer was not
soluble in THF. Not determined.
[c]
Radical Polymerizations of 2-Cyclopropylacrylates 1a؊n
The polymerization of monomers 1aϪe,g was carried out
in chlorobenzene solution using AIBN as the initiator. The
results show (Table 2) that polymers formed from 1a and 1c
Scheme 3. Ring-opening polymerization of methyl 2-cyclopro-
pylacrylate (1a)
¯
have number-average molecular weights (Mn) of 118900 and
86300 g/mol, and Tg of 98 and 118 °C, respectively, while
Polymerizations of the bicyclic monomers 1f,h,i and 1jϪn
the radical polymerizations of 1b and 1e lead to the forma- were also carried out in chlorobenzene solutions with
1
tion of oligomeric products only. The H and 13C NMR AIBN as the initiator. These promising results demonstrate
spectra of the obtained poly-1a confirmed the opening of (Table 3) a significant influence of the size of the second
the cyclopropane ring with formation of a 1,5-disubstituted ring on the radical polymerization of the bicyclic mono-
ring-opened unit (Scheme 3). This ring-opening polymeri- mers. The highest polymer yields were obtained from the
zation which occurs instead of a simple vinyl-group polymeri- polymerizations of 1f and 1h or 1k and 1l, i.e. of monomers
zation, is typical for vinylcyclopropanes.[2] Monomer 1g re- with an annelated five- or six-membered ring. In the case
sulted in an insoluble cross-linked polymer, which was ex- of 1h and 1k both the polymer yields (99 and 98%, respec-
pected on the basis of the bifunctionality of this monomer. tively) and the glass transition temperatures (Tg) of 57 and
In contrast to this, poly-1d was also insoluble in tetrahydro- 93 °C were significantly higher than those observed for
furan, but could be dissolved in other solvents, such as DECVCP. According to these results, the monomers 1h and
chloroform or chlorobenzene. Unfortunately, the polymer- 1k meet the requirements for dental applications mentioned
ization of 1aϪe,g resulted in significantly lower polymer above, and can be considered as leads for further structure
yields in comparison to the 1,1-bis(ethoxycarbonyl)-2-vinyl- optimization. In contrast to this, the bicyclo[2.1.0]pentyl
cyclopropane DECVCP, which was used as a benchmark and bicyclo[6.1.0]nonyl groups containing monomers 1j
for the reactivity in the radical polymerization of the vinyl- and 1n, respectively, gave low or even very low polymer
¯
cyclopropane derivatives. The low polymer yield and Mn yields. In comparison to 1f and 1h, compounds 1j and 1n
value of monomer 1b indicate that a methylene substituent showed a significant reduction of both the polymer yield
affects adversely the formation of high molecular weight and Mn value. It is well documented[2] that the introduction
¯
polymers. This was also confirmed by the fact[14] that 1,1- of a second substituent at the same position of the cyclo-
bis(ethoxycarbonyl)-2-methylenecyclopropane did not form propane ring, such as the vinyl group, may cause a signifi-
polymers in dichlorobenzene in the presence of AIBN after cant decrease of the monomer reactivity in the radical poly-
15 h. The polymerization behavior of 1c can be also ex- merization because of steric interactions. In comparison to
3672
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Eur. J. Org. Chem. 2004, 3669Ϫ3678

Synthesis and Radical Polymerization of Various 2-Cyclopropylacrylates
FULL PAPER
1l, the drastically lower polymer yield in the radical poly- proved reactivity in the radical polymerization when com-
merization of 1m, which contains an annelated cyclohexene pared to DECVCP.
ring, can probably be attributed to the presence of allylic
Table 4. Copolymerization of MMA (1.0 mol/L) with 1a,h,k (1.0
hydrogen atoms in the monomer structure. Generally, this
causes a degradative chain transfer in the radical polymeri-
mol/L) in chlorobenzene and in the presence of AIBN (2.0 mol %)
at a temperature of 65 °C with tP ϭ 2 h
zation with formation of less reactive and therefore more
slowly propagating radicals.[15] The 1H and 13C NMR spec-
[a]
¯
Comonomer Polymer yield (%) Mn [g/mol] FMMA
Tg [°C]
tra of the polymers obtained, for example, in the radical
polymerization of the bicyclic monomers 1h or 1k con-
firmed the opening of the cyclopropane rings with forma-
tion of 1,5-disubstituted ring-opened units containing the
unchanged second ring (Scheme 4).
1a
1h
1k
8.6
27.7
10.1
13300
34300
17900
0.20
0.71
0.91
Ϫ[b]
62
95
[a]
[b]
Molar composition of the copolymer: [Comonomer]/[MMA].
Not determined
Table 3. Polymerization of bicyclic monomers 1f,hϪn (2.0 mol/L)
in chlorobenzene and in the presence of AIBN (2.0 mol %) at a
temperature of 65 °C, with tP ϭ 15 h
Experimental Section
¯
¯
Monomer Polymer yield (%) Mn [g/mol] Mw [g/mol] Tg [°C]
General: 1H NMR spectra were recorded with Bruker AM 250
(250 MHz), Varian Unity 300 (300 MHz) or Bruker DPX-400
(400 MHz) spectrometers. 13C NMR spectra were recorded with
Mercury 200 (50.3 MHz), Bruker AM 250 (62.9 MHz) or Bruker
DPX-400 (100.6 MHz) spectrometers. Multiplicities were deter-
mined by DEPT (Distortionless Enhancement by Polarization
Transfer) or APT (Attached Proton Test) measurements. Tetra-
methylsilane, hexamethyldisilane (HMDS) or residual CHCl3 were
used as internal standards. IR spectra were recorded with a Bruker
IFS 66 (FT-IR) spectrophotometer, as KBr pellets or as neat oils
sandwiched between KBr plates. Mass spectra (EI, 70 eV) were
measured using a Finnigan MAT 95 spectrometer. Melting points
were obtained using a Büchi 510 capillary melting point apparatus
and are uncorrected. TLC: MachereyϪNagel pre-coated sheets,
0.25 mm Sil G/UV254. Column chromatography: Merck silica gel,
grade 60, 70Ϫ230 mesh. Flash chromatography: Merck silica gel,
grade 60 230Ϫ400 mesh; a dry column technique[16] was applied.
1f
1h
1i
1j
1k
1l
1m
1n
30
99
91
37
98
94
27
2
14600
113000
181300
21000
58500
Ϫ[a]
23100
380800
204600
30900
124100
Ϫ
55
57
40
46
93
53
Ϫ
19800
Ϫ
22400
Ϫ
Ϫ
[a]
Not determined
¯
The number-average molecular weights of polymers (Mn) were de-
termined by gel permeation chromatography (GPC) using THF as
eluent, a Spektra 100 UV-detector and columns calibrated with po-
ly(methyl)methacrylate standards. Differential scanning calorim-
etry (DSC) measurements were performed with a PerkinϪElmer
DSC-7 thermal analyzer employing a scan rate of 10 °C/min. The
elemental analyses were performed in Göttingen by the Mikroana-
lytisches Laboratorium with an elemental analyzer CHN-2000
(Leco). Solvents diethyl ether and tetrahydrofuran (THF) were dis-
tilled from sodium/benzophenone. Diisopropylamine, 2,6-lutidine
and dimethyl sulfoxide were distilled from calcium hydride under
nitrogen. Anhydrous methanol and ethanol were distilled from the
corresponding magnesium alkoxides under nitrogen. Anhydrous di-
chloromethane was distilled from phosphorus pentoxide under ni-
Scheme 4. Ring-opening polymerization of bicyclic monomers
1f,hϪn; for substituents R1, R2, R4 and R5 see Scheme 1
As mentioned above, 2-vinylcyclopropane-1,1-dicar-
boxylates are less reactive in the radical copolymerization
with methacrylates. In order to elucidate this feature, the
radical copolymerizations of MMA with 1a, 1h, or 1k were
carried out in chlorobenzene solutions in the presence of
AIBN (Table 4). The composition of the copolymers
trogen. Benzene, cyclopentene, cyclohexene, chlorobenzene and di-
formed could be determined by 1H NMR spectroscopy, methylformamide were dried with molecular sieves (4 A). Pentane,
˚
hexane, 1,3-cyclohexadiene, tert-butyl methyl ether, oxalyl chloride,
methyl and ethyl chlorooxalate, lithium hydroxide monohydrate, so-
dium cyanide, activated manganese() oxide, 10 wt.-% Pd/C, di-
rhodium tetraacetate, methyltriphenylphosphonium bromide, po-
tassium tert-butoxide, n-butyllithium solution in hexane, 2,6-di-
tert-butyl-4-methylphenol (BHT), dimethyl trans-cyclopropane-1,2-
dicarboxylate (3d) and aliphatic urethane dimethacrylate (UDMA,
Ivoclar Vivadent, from 2-hydroxyethyl methacrylate and 2,2,4-tri-
methylhexamethylenediisocyanate) were used as supplied without
further purification. 1,1-Bis(ethoxycarbonyl)-2-vinylcyclopro-
using the intensity ratio of the peaks at δ ϭ 3.69 ppm as-
signed to the OCH3 protons of 1a, 1h, or 1k and at δ ϭ
3.60 ppm assigned to the OCH3 protons of the MMA units.
The copolymers formed with 1h and 1k contained visibly
fewer units derived from MMA in comparison with the co-
polymer of 1a. Taking into consideration the fact that the
molar composition of a copolymer of DECVCP and MMA
obtained under similar conditions[4] was 0.09:1.00, it can
be concluded that the 2-cyclopropylacrylates, especially the
bicyclic monomers 1h and 1k, demonstrate a drastically im- pane[17] (DECVCP), methylenecyclopropane[18] (2b), bicyclopro-
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A. de Meijere, V. Bagutski, F. Zeuner, U. K. Fischer, V. Rheinberger, N. Moszner
FULL PAPER
pylidene[19] (2c), dimethyl bicyclo[3.1.0]hexane-6,6-dicarboxylate[20] ester 3f with LiOH, was recrystallized from a mixture of toluene
(3f), diethyl 2-formylcyclopropane-1,1-dicarboxylate[7] (5e), potas-
and cyclohexane (1:2; 250 mL) to yield 13.92 g of pure 4f as color-
sium cyclopropyloxoacetate,[21] methyl and ethyl diazopyruvate,[22] less prisms. A second crop (1.29 g) was obtained after concen-
3,3-dimethylcyclobutyl bromide,[23] ethyl trans-(2-ethenylcyclo-
propyl)oxoacetate (7g) and ethyl trans-2-(2-ethenylcyclopropyl)-
propenoate[13] (1g) were prepared as described previously. 2,2Ј-Azo-
bisisobutyronitrile (AIBN) was purified by recrystallization
from methanol. Methyl methacrylate (MMA) was washed with a
5.0 wt.-% NaOH solution, dried with anhydrous sodium sulfate,
and distilled from calcium hydride under argon.
tration of the mother liquor and recrystallization of the residue
from the same solvent (ca. 25 mL). The overall yield was 15.21 g
(83%), m.p. 137Ϫ137.5 °C. IR (KBr): ν˜ ϭ 3450, 3045, 3023, 2968,
2875, 1747, 1700, 1443, 1371, 1316, 1283, 1233, 1193, 1162, 1110,
1050, 1022, 938, 872, 806, 768 cmϪ1. 1H NMR (250 MHz, CDCl3):
δ ϭ 0.83 [m, 1 H, C(3)ϪH], 1.67 [m, 1 H, C(3)ϪH], 1.85Ϫ2.10 (m,
4 H, 2 CH2), 2.20 (m, 2 H, 2 CH), 3.73 (s, 3 H, OCH3), 11.22 (br.
s, 1 H, OH) ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 21.3
(CH2), 26.4 (2 CH2), 35.7 (2 CH), 35.8 (C), 52.7 (CH3), 167.6 (C),
176.8 (C) ppm. MS (70 eV, EI): m/z (%) ϭ 184 (22) [Mϩ], 166 (96)
[Mϩ Ϫ H2O], 155 (21) [Mϩ Ϫ H Ϫ C2H4], 153 (73) [Mϩ Ϫ CH3O],
152 (70) [Mϩ Ϫ CH3OH], 138 (36) [Mϩ Ϫ CO Ϫ H2O], 134 (100)
[Mϩ Ϫ CH3OH Ϫ H2O], 124 (78), 107 (21), 106 (36), 93 (15), 79
(90), 77 (34) [C6H5ϩ], 67 (27), 53 (12), 41 (19) [C3H5ϩ]. C9H12O4
(184.19): calcd. C 58.69, H 6.57; found C 58.89, H 6.83.
Syntheses
3,3-Dimethylcyclobut-1-ene (8j): 1-Bromo-3,3-dimethylcyclobutane
(49.3 g, 302 mmol) was added in one portion to a stirred solution
of tBuOK (52 g, 463 mmol) in anhydrous DMSO (460 mL), kept
at 20 °C (cold water bath) under nitrogen. The mixture was stirred
at ambient temperature for 20 min, the volatile material was bulb-
to-bulb-distilled (Tbath 50 °C/20 Torr) into a Ϫ78 °C (dry ice/ace-
tone bath) cold, pointed-bottom Schlenk flask. After the distil-
lation was complete, the crude product was transferred by cannula
from the cooled collecting flask into a separating funnel, washed
with water (2 ϫ 20 mL), brine (10 mL) and placed in a storage
bottle containing a small amount of BHT (ca. 10 mg) and molecu-
General Procedure for the Two-Step Synthesis of Aldehydes 5d,f
from Carboxylic Acids by Rosenmund Reduction of Acid Chlorides
(GP 1):[9] Anhydrous DMF (0.1 mL) and oxalyl chloride (15.2 g,
10.3 mL, 120 mmol) were added at ambient temperature to a
stirred solution of the respective carboxylic acid (100 mmol) in an-
hydrous CH2Cl2 (50 mL), and the mixture was stirred until the gas
evolution had ceased (1Ϫ2 h). Then the solvent was evaporated un-
der reduced pressure (15Ϫ20 Torr) without heating until the tem-
perature of the reaction flask had reached ca. 20 °C, anhydrous
benzene (50 mL) was added to the residue and solvent evaporation
was repeated under the same conditions. The resulting crude acyl
chloride was used for the next step without additional purification.
Freshly distilled 2,6-lutidine (10.7 g, 11.6 mL, 100 mmol) and the
crude acyl chloride were added at ambient temperature to a vigor-
ously stirred suspension of 10% Pd/C (1.5 g, 1.4 mmol) in anhy-
drous degassed THF (500 mL) under hydrogen (1 bar). The reac-
tion mixture was stirred until the hydrogen absorption had ceased
(2Ϫ12 h), then the solvent was evaporated under reduced pressure
at ambient temperature. The residue was triturated with anhydrous
ether (100 mL), the solution diluted with pentane (200 mL) whilst
stirring, and filtered through Celite which was subsequently
washed with a 2:1 mixture of ether/pentane (2 ϫ 50 mL). The fil-
trate was concentrated under reduced pressure at ambient tempera-
ture to give the crude aldehyde, which was purified by distillation
under reduced pressure.
˚
lar sieves (4 A) (ca. 1 g). The colorless liquid weighed 21.9 g (88%).
1
It was pure 3,3-dimethylcyclobut-1-ene according to its H NMR
1
spectrum. H NMR (250 MHz, CDCl3): δ ϭ 1.19 (s, 6 H, 2 CH3),
2.25 (d, J ϭ 1 Hz, 2 H, CH2), 5.99 [dt, J ϭ 2.8, 1 Hz, 1 H, C(1)ϪH],
6.09 [d, J ϭ 2.8 Hz, 1 H, C(2)ϪH] ppm. 13C NMR (62.9 MHz,
CDCl3, DEPT): δ ϭ 26.5 (2 CH3), 44.6 (CH2), 44.9 (C), 132.0
(CH), 146.5 (CH) ppm.
Partial Hydrolysis of Diesters 3d,f with Lithium Hydroxide: A solu-
tion of LiOH·H2O (4.2 g, 100 mmol) in anhydrous methanol
(100 mL) was added dropwise over a 30-min period to a vigorously
stirred solution of the respective diester (100 mmol) in anhydrous
THF (400 mL) at ambient temperature, and the mixture was stirred
for an additional 24 h. Then the solvents were completely evapo-
rated under reduced pressure (Tbath ϭ 40 °C), the residue was dis-
solved in a minimal amount of water (ca. 100 mL) and extracted
with diethyl ether (2 ϫ 50 mL). The aqueous phase was acidified
with 12  HCl, saturated with NaCl and extracted with diethyl
ether (5 ϫ 100 mL). The combined extracts were dried with
Na2SO4, and the solvents evaporated under reduced pressure to
give a crude product, which was purified by distillation under re-
duced pressure or recrystallized from an appropriate solvent.
Methyl trans-2-Formylcyclopropanecarboxylate (5d): According to
GP 1, the half-ester 4d (15.1 g, 105 mmol), after distillation of the
crude product, gave 11.4 g (85%) of pure 5d as a colorless oil, b.p.
trans-2-(Methoxycarbonyl)cyclopropanecarboxylic Acid (4d):
A
crude mixture (25 g) obtained after hydrolysis of the diester 3d
(31 g, 196 mmol) with LiOH, was bulb-to-bulb-distilled under re-
duced pressure (Tbath ϭ 100Ϫ110 °C/0.1 Torr) to give pure ester 4d
(20 g, 70%), the physical properties and 1H NMR spectra of which
are identical to those reported in the literature.[24] IR (film): ν˜ ϭ
3116, 3078, 3018, 2958, 2751, 2702, 2658, 2560, 1731, 1698, 1436,
1376, 1327, 1305, 1207, 1175, 1115, 1087, 1055, 1006, 918, 853, 820,
1
81Ϫ82 °C (12 Torr), H and 13C NMR spectra of which are ident-
ical to those reported in the literature.[26] IR (film): ν˜ ϭ 3105, 3062,
3013, 2958, 2849, 2740, 1736, 1715, 1436, 1387, 1322, 1284, 1207,
1175, 1082, 1060, 1022, 946, 913, 864, 850, 820, 749, 735, 667 cmϪ1
.
MS (70 eV, EI): m/z (%) ϭ 128 (4) [Mϩ], 113 (1) [Mϩ Ϫ CH3], 99
(4) [Mϩ Ϫ CHO], 97 (19) [Mϩ Ϫ OCH3], 96 (20) [Mϩ Ϫ CH3OH],
85 (2), 71 (6), 69 (53) [Mϩ Ϫ CO2CH3], 68 (33) [Mϩ Ϫ CH3OH Ϫ
CO], 59 (18), 55 (9), 45 (2), 43 (5), 42 (9), 41 (100) [C3H5ϩ], 40
(22) [C3H4ϩ].
744, 651, 629 cmϪ1 13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ
.
15.8 (CH2), 22.0 (CH), 22.7 (CH), 52.3 (CH3), 171.8 (C), 178.1 (C)
ppm. MS (70 eV, EI): m/z (%) ϭ 144 (1) [Mϩ], 143 (1) [Mϩ Ϫ H],
127 (4) [Mϩ Ϫ OH], 126 (4) [Mϩ Ϫ H2O], 113 (100) [Mϩ Ϫ OCH3],
112 (54) [Mϩ Ϫ CH3OH], 99 (23) [Mϩ Ϫ CO2 Ϫ H], 98 (58) [Mϩ
Methyl exo-6-Formylbicyclo[3.1.0]hexane-6-carboxylate (5f): Ac-
cording to GP 1, the half-ester 4f (14.7 g, 80 mmol), after distil-
lation of the crude product, gave pure 5f (11.8 g, 88%) as a colorless
oil, b.p. 66Ϫ67 °C (7 mbar). IR (film): ν˜ ϭ 2955, 2918, 2894, 2866,
2791, 2753, 2716, 1739, 1701, 1480, 1438, 1405, 1372, 1330, 1293,
1232, 1199, 1156, 1109, 1091, 1054, 1030, 987, 964, 945, 893, 870,
Ϫ CO Ϫ H2O], 95 (6), 85 (27) [Mϩ Ϫ CO2Me], 84 (51) [Mϩ
Ϫ
CO2Me Ϫ H], 71 (4), 69 (10), 68 (20), 67 (6), 59 (32), 57 (16), 55
(18), 45 (16), 43 (6), 42 (6), 41 (20). C6H8O4 (144.13): calcd. C
50.00, H 5.59; found C 49.74, H 5.36.
exo-6-(Methoxycarbonyl)bicyclo[3.1.0]hexane-6-carboxylic
Acid
1
(4f):[8] The colorless solid (15.53 g) obtained after hydrolysis of di-
832, 809, 757 cmϪ1. H NMR (250 MHz, CDCl3): δ ϭ 0.93Ϫ1.14
3674
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 3669Ϫ3678

Synthesis and Radical Polymerization of Various 2-Cyclopropylacrylates
FULL PAPER
[m, 1 H C(3)ϪH], 1.66Ϫ1.80 [m, 1 H C(3)-H], 1.91Ϫ2.12 (m, 4 H,
MgSO4. The crude product obtained after evaporation of the sol-
2 CH2), 2.20Ϫ2.26 [m, 2 H, 2 CH], 3.78 (s, 3 H, CH3), 9.15 (s, 1 vent was distilled under reduced pressure or used in the next step
H, CHO) ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 22.3 without further purification.
(CH2), 26.2 (2 CH2), 35.3 (2 CH), 45.2 (C), 52.5 (CH3), 168.6 (C),
Methyl exo-(6-Methoxycarbonylbicyclo[3.1.0]hex-6-yl)hydroxyacet-
ate (6f): According to GP 2B, the crude cyanohydrin (13.6 g,
69.6 mmol) obtained from the aldehyde 5f (11.8 g, 70.2 mmol) after
workup (the imino ester hydrochloride was hydrolyzed by stirring
the aqueous mixture at ambient temperature for 16 h) gave crude
6f (14.9 g, 94%) as a colorless oil, which was used for the next step
without additional purification. Flash chromatography of the crude
product (0.71 g), eluting with pentane/diethyl ether (10:1 to 5:1)
and subsequent kugelrohr distillation, gave an analytical sample 6f
(0.60 g, 84%) as colorless oil. IR (film): ν˜ ϭ 3487, 3029, 2953, 2865,
1736, 1436, 1393, 1349, 1295, 1267, 1202, 1153, 1137, 1098, 1060,
195.5 (CH) ppm. MS (70 eV, EI), m/z (%) ϭ 168 (9) [Mϩ], 167
(100) [Mϩ Ϫ H], 135 (13), [Mϩ Ϫ CH3OH Ϫ H], 108 (3) [Mϩ
Ϫ
CO2CH3], 107 (4) [Mϩ Ϫ CO2CH3 Ϫ H], 79 (5) [C6H7ϩ], 67 (6).
C9H12O3 (168.19): calcd. C 64.27, H 7.19; found C 64.07, H 7.03.
General Procedure for the Two-Step Synthesis of α-Hydroxycar-
boxylic Esters from Aldehydes (GP 2): A solution of NaCN (11.3 g,
230 mmol) in water (25 mL) was added with cooling (ice/water
bath) during a period of 20 min to a stirred suspension of NH4Cl
(13.9 g, 260 mmol) and the respective aldehyde (200 mmol) in
70 mL of a 1:1 mixture of water/diethyl ether so that the tempera-
ture of the mixture was kept at 10 °C. After the addition was com-
plete, the mixture was stirred at this temperature for an additional
20 min. The organic layer was separated, and the aqueous phase
was extracted with ethyl acetate (3 ϫ 50 mL). The combined ex-
tracts were washed with brine (2 ϫ 50 mL), acidified with a few
drops of ortho-phosphoric acid, dried with MgSO4, filtered and
concentrated under reduced pressure at ambient temperature to
give the crude product,[1,10] which was converted into the alkyl α-
hydroxyacetates 6bϪf by two different methods. Method A: Anhy-
drous MeOH (16 mL, 400 mmol) and diethyl ether (25 mL) were
added under nitrogen to the crude cyanohydrin. This mixture was
added in one portion with stirring to a pre-cooled (Ϫ10 °C, ice/
salt bath) solution prepared by saturating anhydrous diethyl ether
(100 mL) at 0 °C with dry HCl and subsequent dilution with the
same solvent (175 mL). The mixture was stirred at 0Ϫ2 °C for 18 h,
then the solid was filtered off, washed with anhydrous diethyl ether
(50 mL) and dried under reduced pressure at ambient temperature
to give a slightly gray powder, which was then added with stirring
to water (100 mL) and kept at 0 °C (ice bath). The mixture was
stirred at 0 °C for 30 min and at ambient temperature for 1 h. The
aqueous phase was saturated with NaCl and extracted with ethyl
acetate (4 ϫ 50 mL). The combined organic layers were washed
with brine (50 mL) and dried with MgSO4. The solvent was evapo-
rated, and the residue distilled under reduced pressure, or was used
in the next step without additional purification.[1,11] Method B: A
three-necked pointed-bottom 250-mL flask was equipped with a
septum, thermometer and gas inlet tube, which almost reached the
bottom of the flask. The outer neck of the inlet tube was fitted with
a bubbler charged with paraffin, and this in turn was connected to
a CaCl2 drying tube. The reaction flask was immersed in a dry ice/
acetone bath, and a slow stream of dry hydrogen chloride was
passed through the system. Then a solution of the crude cyanohy-
drin (200 mmol) in the respective anhydrous alcohol (100 mL) was
added by syringe at such a rate as to keep the temperature of the
reaction mixture below Ϫ10 °C (ca. 20 min, cooling with dry ice/
acetone bath). At the same time the stream of HCl was adjusted so
as to keep the pressure in the reaction flask slightly above ambient
(controlled by the bubbler). After the addition of the solution was
complete, the mixture was saturated with hydrogen chloride at Ϫ20
°C and the cooling bath was removed. After stirring at ambient
temperature for an additional 2 h, the solvents were evaporated un-
der reduced pressure at ambient temperature. Ice/water (100 mL)
was added to the stirred residue at 0 °C, and the mixture was stirred
at this temperature for an additional 30 min. The ice bath was re-
1
1027, 989, 946, 853, 842, 706 cmϪ1. H NMR (250 MHz, CDCl3):
δ ϭ 0.91Ϫ1.11 [m, 1 H, C(3)-H], 1.58Ϫ1.72 [m, 1 H, C(3)-H],
1.75Ϫ1.90 (m, 5 H, 2 CH2 ϩ CH), 1.92Ϫ2.05 (m, 1 H, CH), 3.02
(br. s, 1 H, OH), 3.60 (s, 1 H, CH), 3.65 (s, 3 H, CH3), 3.79 (s, 3
H, CH3) ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 23.2
(CH2), 25.9 (CH2), 26.3 (CH2), 30.0 (CH), 30.3 (CH), 36.9 (C),
52.0 (CH3), 52.7 (CH3), 75.3 (CH), 170.3 (C), 173.4 (C) ppm. MS
(70 eV, EI): m/z (%) ϭ 228 (2) [Mϩ], 227 (3) [Mϩ Ϫ H], 197 (2)
[Mϩ Ϫ CH3O], 178 (10), 169 (33) [Mϩ Ϫ CO2CH3], 159 (11), 137
(100), 118 (11), 109 (21), 91 (15), 81 (24) [C6H9ϩ], 79 (22) [C6H7ϩ],
77 (8) [C6H5ϩ], 72 (11), 67 (30), 53 (6), 41 (5). C11H16O5 (228.24):
calcd. C 57.88, H 7.07; found C 57.60, H 6.85.
General Procedure for the Oxidation of α-Hydroxy Esters 6bϪf to α-
Oxo Esters 7bϪf with Active Manganese Dioxide (GP 3):[1,12] Active
MnO2 (Fluka) (2 ϫ 40 g) was added, in two portions with an
interval of 2 h, to a well-stirred solution of the respective α-hydroxy
ester (80 mmol) in anhydrous diethyl ether (500 mL). The suspen-
sion was stirred at ambient temperature (2Ϫ4 h) until the starting
material had been completely consumed (TLC monitoring). The
mixture was filtered through Celite, which was subsequently
washed with diethyl ether (2 ϫ 150 mL). The solvent was evapo-
rated from the combined filtrates under reduced pressure to give
sufficiently pure (Ͼ 95% according to GC) α-oxo ester, which could
be used without additional purification.
Methyl
exo-(6-Methoxycarbonylbicyclo[3.1.0]hex-6-yl)oxoacetate
(7f): Oxidation of crude 6f (11.7 g, 51 mmol) according to GP 3
gave a colorless oil (9.8 g, 84%), which was pure according to its
1H NMR spectroscopic data. An analytical sample was obtained
by kugelrohr distillation of crude 7f. IR (film): ν˜ ϭ 3034, 2957,
2869, 1739, 1701, 1437, 1360, 1311, 1289, 1234, 1196, 1152, 1075,
1031, 1004, 982, 949, 905, 878, 856, 846, 817, 779, 751, 718 cmϪ1
.
1H NMR (250 MHz, CDCl3): δ ϭ 1.02Ϫ1.22 [m, 1 H, C(3)-H],
1.66Ϫ1.81 [m, 1 H, C(3)-H], 1.93Ϫ2.16 (m, 4 H, 2 CH2), 2.32Ϫ2.38
(m, 2 H, 2 CH), 3.75 (s, 3 H, CH3), 3.83 (s, 3 H, CH3) ppm. 13C
NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 22.4 (CH2), 26.7 (2 CH2),
41.5 (2 CH), 43.3 (C), 52.5 (CH3), 53.0 (CH3), 161.7 (C), 168.3 (C),
189.0 (C) ppm. MS (70 eV, DCI, NH3): m/z (%) ϭ 470 (1) [2M ϩ
NH4ϩ], 244 (100) [M ϩ NH4ϩ]. C11H14O5 (226.23): calcd. C 58.40,
H 6.24; found C 58.15, H 5.95.
General Procedure for the Synthesis of Alkyl Oxoacetates 7hϪn by
[Rh2(OAc)4]-Catalyzed Addition of Alkyl 3-Diazopyruvates to Cyclic
Alkenes (GP 4): A solution of the corresponding alkyl 3-diazopy-
moved, and the mixture was stirred at ambient temperature for ruvate[22] (200 mmol) in anhydrous degassed CH2Cl2 (400 mL) was
an additional time (1 h or 16 h for gem-alkoxycarbonyl-substituted
cyanohydrins). The organic layer was separated, and the aqueous
phase was extracted with ethyl acetate (4 ϫ 50 mL). The combined
added to a well-stirred solution of [Rh2(OAc)4] (0.14Ϫ0.39 mol %)
and the respective cycloalkene (200Ϫ500 mmol) in the same solvent
(400 mL) during 16 h. After the addition was complete, the
organic phases were washed with brine (50 mL) and dried with solvents were evaporated under reduced pressure at ambient
Eur. J. Org. Chem. 2004, 3669Ϫ3678
www.eurjoc.org  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 3675

A. de Meijere, V. Bagutski, F. Zeuner, U. K. Fischer, V. Rheinberger, N. Moszner
FULL PAPER
1
temperature. The residue was triturated with pentane (110 mL),
755, 720 cmϪ1. H NMR (250 MHz, CDCl3): δ ϭ 1.24Ϫ1.36 (m,
passed through a pad (diameter 65 ϫ 30 mm) of silica gel used for 4 H), 1.68Ϫ1.79 (m, 2 H), 1.85Ϫ1.95 (m, 4 H), 2.58 (t, J ϭ 3.4 Hz,
flash chromatography and washed with pentane/diethyl ether (10:1;
1 H, CH), 3.86 (s, 3 H, CH3) ppm. 13C NMR (62.9 MHz, CDCl3,
3 ϫ 150 mL). The slightly yellow oil obtained after evaporation of DEPT): δ ϭ 20.7 (2 CH2), 23.1 (2 CH2), 30.5 (2 CH), 32.1 (CH),
the solvent was purified by column chromatography on silica gel.
52.9 (CH3), 161.7 (C), 193.1 (C) ppm. MS (70 eV, EI): m/z (%) ϭ
182 (1) [Mϩ], 123 (100) [Mϩ Ϫ CO2CH3], 95 (45) [C7H11ϩ], 93 (4)
[C7H9ϩ], 91 (3) [C7H7ϩ], 81 (19) [C6H9ϩ], 79 (19) [C6H7ϩ], 77 (6)
[C6H5ϩ], 67 (39), 66 (5), 65 (5), 59 (4), 55 (61), 53 (20), 51 (4), 41
(42). HRMS (EI): calcd. for (C10H14O3) [Mϩ] 182.0943, found
182.0943.
Methyl exo-(Bicyclo[3.1.0]hex-6-yl)oxoacetate (7h): Addition of
methyl diazopyruvate[22] (19.8 g, 155 mmol) to cyclopentene
(27 mL, 308 mmol) in the presence of 0.26 mol % of Rh2(OAc)4
(176 mg, 0.4 mmol) according to GP 4 gave a slightly yellow oil
(25.7 g), which was subjected to chromatography on silica gel (2 L)
eluting with pentane/diethyl ether (10:1) to give pure 7h (12.7 g,
49% yield, Ͼ 98% purity according to GC) as a colorless oil. B.p.
80Ϫ82 °C (2 mbar). IR (film): ν˜ ϭ 3037, 2956, 2886, 2865, 1735,
1706, 1448, 1438, 1406, 1327, 1290, 1249, 1227, 1169, 1100, 1074,
Ethyl exo-(Bicyclo[4.1.0]hept-2-en-7-yl)oxoacetate (7m): Addition
of ethyl diazopyruvate[22] (10.0 g, 70 mmol) to 1,3-cyclohexadiene
(13 mL, 137 mmol) in the presence of 0.32 mol % of [Rh2(OAc)4]
(100 mg, 0.22 mmol) according to GP 4 gave a crude product
(10.7 g) as a yellow oil, which was subjected to chromatography on
silica gel (1 L), eluting with hexane/tBuOMe (20:1) to yield pure
7m (7.9 g, 58%). IR (film): ν˜ ϭ 3039, 2985, 2936, 2852, 1728, 1703,
1638, 1473, 1445, 1420, 1393, 1370, 1295, 1258, 1236, 1196, 1089,
1044, 1017, 992, 976, 935, 887, 843, 804, 754 cmϪ1
(250 MHz, CDCl3): δ ϭ 1.20 [dtt, J ϭ 13.3, 10.8, 9 Hz, 1 H, C(3)-
exo], 1.60Ϫ1.94 (m, 5 H), 2.10Ϫ2.13 (m, 2 H, 2 CH), 2.57 (t, J ϭ
.
1H NMR
H
2.8 Hz, 1 H, CH), 3.85 (s, 3 H, CH3) ppm. 13C NMR (62.9 MHz,
CDCl3, DEPT): δ ϭ 19.9 (CH2), 27.4 (CH), 27.5 (2 CH2), 35.9 (2
CH), 52.9 (CH3), 161.6 (C), 192.6 (C) ppm. MS (70 eV, EI): m/z
(%) ϭ 168 (2) [Mϩ], 109 (100) [Mϩ Ϫ CO2CH3], 85 (2), 81 (26)
[Mϩ Ϫ C2H3O2 Ϫ CO], 79 (8) [C6H7ϩ], 71 (3), 67 (2), 55 (3), 53 (7),
41 (6). C9H12O3 (168.19): calcd. C 64.27, H 7.19; found C 64.51, H
6.92.
1043, 1015, 961, 928, 858, 802, 757, 746, 684 cmϪ1 1H NMR
.
(250 MHz, CDCl3): δ ϭ 1.35 (t, J ϭ 7 Hz, 3 H, CH3), 1.63Ϫ2.23
(m, 6 H), 3.02 (dd, J ϭ 4.2, 3.5 Hz, 1 H, CH), 4.31 (q, J ϭ 7 Hz,
2 H, CH2), 5.58Ϫ5.66 (m, 1 H, CH), 5.92Ϫ5.60 (m, 1 H, CH) ppm.
13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 14.0 (CH3), 17.9 (CH2),
20.3 (CH2), 28.3 (CH), 30.1 (CH), 30.9 (CH), 62.4 (CH2), 124.9
(CH), 126.3 (CH), 161.0 (C), 191.8 (C) ppm. MS (70 eV, EI): m/z
(%) ϭ 194 (7) [Mϩ], 179 (2) [Mϩ Ϫ CH3], 165 (4) [Mϩ Ϫ C2H5],
148 (6), 147 (7), 121 (73), 120 (48), 116 (15), 103 (14), 93 (100), 91
(64), 79 (34) [C6H7ϩ], 77 (57) [C6H5ϩ], 65 (13), 55 (27), 41 (7).
HRMS (EI): calcd. for (C11H14O3) [Mϩ] 194.0943, found 194.0943.
Ethyl (2,2-Dimethylbicyclo[2.1.0]pent-5-yl)oxoacetate (7j): Addition
of ethyl diazopyruvate[22] (24.4 g, 172 mmol) to 3,3-dimethylcyclo-
butene (8j; 25 mL, 215 mmol) in the presence of 0.39 mol % of
[Rh2(OAc)4] (300 mg, 0.68 mmol) according to GP 4 gave a crude
product (29.1 g) as a yellow oil, which was separated by column
chromatography on silica gel (2 L), eluting with hexane/tBuOMe
(20:1) to yield an intermediate fraction (2.27 g) containing about
70% of 7j and pure 7j (11.7 g, 35%, purity Ͼ 98% according to GC)
as a 3.8:1 mixture of exo/endo isomers. A small amount (250 mg) of
pure exo-7j was isolated by column chromatography of an aliquot
of the mixture of exo/endo isomers (2 g) on 200 g of silica gel under
the same conditions as above, but only from the latest fractions. IR
(film): ν˜ ϭ 3039, 2959, 2930, 2867, 1733, 1712, 1465, 1443, 1385,
1368, 1303, 1271, 1240, 1146, 1082, 1030, 1015, 986, 938, 914, 880,
General Procedure for the Wittig Methylenation of Oxo Esters 7dϪn
to 2-Substituted Alkyl Acrylates 1dϪn (GP 5B): First diisopro-
pylamine (1.4 mL, 10 mmol), then a 2.5  nBuLi solution in hexane
(40 mL, 100 mmol) were added to a well-stirred suspension of
methyltriphenylphosphonium bromide (37.5 g, 105 mmol) in anhy-
drous THF (250 mL), kept at Ϫ78 °C (dry ice/acetone bath) under
nitrogen. After the slight warming of the reaction mixture had
ceased, the cooling bath was removed, and the mixture was warmed
up to ambient temperature (about 1 h), then cooled to Ϫ78 °C
again, and a solution of the respective carbonyl compound
(100 mmol) in anhydrous THF (20 mL) was added with vigorous
stirring so that the temperature did not exceed Ϫ50 °C. After stir-
ring for an additional 30 min at this temperature, the cooling bath
was removed, the reaction mixture was stirred overnight (12 h) and
then acidified with 5% aqueous H2SO4 (10 mL). Brine (50 mL) was
then added, the organic phase was separated and the aqueous
phase was extracted with diethyl ether (2 ϫ 100 mL). The com-
bined organic layers were washed with brine (2 ϫ 100 mL) and
dried with MgSO4. BHT (10 mg) was added, and a major pro-
portion of the solvents was removed at ambient temperature in a
rotary evaporator until the volume of the residue had been reduced
to 50Ϫ60 mL. Pentane (500 mL) was gradually added to the stirred
liquid residue (a spontaneously solidified residue may be homoge-
nized by adding a minimal amount of warm dichloromethane), and
1
834, 790, 739 cmϪ1. H NMR (250 MHz, CDCl3): δ ϭ 0.90 (s, 3
H, CH3), 1.29 (s, 3 H, CH3), 1.37 (t, J ϭ 7 Hz, 3 H, CH3), 1.42 [d,
J ϭ 11.5 Hz, 1 H, C(3)-H], 1.79 [dd, J ϭ 11.5, 4 Hz, 1 H, C(3)-H],
2.10 (d, J ϭ 4.8 Hz, 1 H, CH), 2.17 (dd, J ϭ 4.8, 4 Hz, 1 H, CH),
3.05 (s, 1 H, CH), 4.33 (q, J ϭ 7 Hz, 2 H, CH2) ppm. 13C NMR
(62.9 MHz, CDCl3, DEPT): δ ϭ 14.0 (CH3), 23.3 (CH3), 26.4
(CH), 29.5 (CH3), 34.1 (CH), 36.3 (C), 38.1 (CH2), 41.8 (CH), 62.4
(CH2), 161.0 (C), 192.3 (C) ppm. MS (70 eV, DCI, NH3): m/z
(%) ϭ 410 (4) [2M ϩ NH4ϩ], 231 (19) [M ϩ NH3 ϩ NH4ϩ], 214
(100) [M ϩ NH4ϩ], 185 (1) [M ϩ NH4ϩ Ϫ C2H5ϩ], 135 (2), 95 (1),
79 (9), 77 (5), 67 (23), 55 (17), 53 (6), 41 (10). C11H16O3 (196.24):
calcd. C 67.32, H 8.22; found C 67.19, H 7.96.
Methyl exo-(Bicyclo[4.1.0]hept-7-yl)oxoacetate (7k): Addition of
methyl diazopyruvate[22] (25.6 g, 200 mmol) to cyclohexene (50 mL,
500 mmol) in the presence of 0.31 mol % of [Rh2(OAc)4] (0.28 g,
0.63 mmol) according to GP 4 gave a crude product (31 g) as a the stirring continued at 0 °C until the OPPh3 crystallization was
yellow oil, which was separated into four fractions by column chro- complete. Then the solid was filtered off and washed with pentane/
matography on silica gel (2 L), eluting with hexane/tBuOMe (10:1) ether (10:1; 2 ϫ 50 mL). The combined filtrates were concentrated
as analyzed by GC. Fraction I: methyl 3-(cyclohexene-1-yl)pyruvate
(2.16 g, 92% purity); fraction II: 7k contaminated with some un-
identified products (1 g, 50% purity); fraction III: 7k (2.8 g, 73%
purity); fraction IV: pure 7k (19.9 g, 55%, Ͼ 99.5% purity). IR
(film): ν˜ ϭ 3011, 2935, 2860, 1734, 1703, 1449, 1413, 1306, 1259,
under reduced pressure at ambient temperature. In the cases of the
relatively low-boiling compounds 1a, 1b and 1g, the solvents were
distilled off at ambient pressure at a bath temperature Ͻ 60 °C,
and the remaining solvent was removed under reduced pressure (ca.
10 Torr) at ambient temperature (the evaporation was stopped as
1203, 1172, 1152, 1100, 1077, 1037, 1017, 973, 950, 890, 843, 779, soon as the contents of the distillation flask had reached room
3676  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2004, 3669Ϫ3678

Synthesis and Radical Polymerization of Various 2-Cyclopropylacrylates
FULL PAPER
temperature). The obtained crude product was purified by column
chromatography or distilled under reduced pressure.
raphy on silica gel (700 mL), eluting with pentane/ether (50:1) to
give pure exo-7j (5.2 g, exo/endo ratio 94:2 according to GC) con-
taminated with some by-product (4%) and pure endo-7j (210 mg).
Total yield 66%. exo-7j: Colorless oil. IR (film): ν˜ ϭ 3111, 3045,
3023, 2957, 2924, 2864, 2721, 1723, 1624, 1465, 1465, 1443, 1410,
1384, 1366, 1311, 1262, 1212, 1152, 1124, 1108, 1026, 997, 872, 812,
Methyl exo-2-(6-Methoxycarbonylbicyclo[3.1.0]hex-6-yl)propenoate
(1f): Methylenation of the oxo ester 7f (7.9 g, 35 mmol) according
to GP 5B yielded only 1.5 g (19%) of 1f, most of the starting mate-
rial being recovered. Therefore, an improved protocol (GP 5C) to
784, 675 cmϪ1 1H NMR (250 MHz, CDCl3): δ ϭ 0.88 (s, 3 H,
.
methylenate 7f was developed. GP 5C: A freshly prepared solution
of tBuOK (0.25 g, 2.2 mmol) in anhydrous THF (10 mL) was ad-
ded all at once with stirring into an oven-dried 25-mL flask charged
with methyltriphenylphosphonium bromide (0.82 g, 2.3 mmol) un-
der argon at ambient temperature. After additional stirring at room
temperature for 1 h, the ylide solution was cooled to Ϫ30 °C and
oxo ester 7f (0.45 g, 2 mmol) dissolved in the same solvent (2 mL)
was added dropwise, keeping the temperature of the reaction mix-
ture below Ϫ20 °C, and stirring continued at this temperature for
an additional 1 h. Then, the cooling bath was removed, and stirring
was continued at ambient temperature for 16 h. The reaction was
quenched by addition of a few drops of acetic acid. Most of the
solvent was removed under reduced pressure at ambient tempera-
ture. The residue was suspended in tBuOMe (10 mL) whilst stir-
ring, poured into pentane (20 mL), and the mixture was filtered.
The residue obtained after evaporation of the solvents from the
filtrate was subjected to chromatography on silica gel (50 mL), elut-
ing with hexane/tBuOMe (10:1) to give pure 1f (0.35 g, 78%). IR
(film): ν˜ ϭ 3111, 3023, 2952, 2869, 1734, 1635, 1437, 1371, 1295,
1233, 1196, 1152, 1102, 1048, 1026, 993, 954, 916, 867, 845, 812,
768, 685 cmϪ1. 1H NMR (250 MHz, CDCl3): δ ϭ 1.34Ϫ1.52 [m, 1
H, C(3)-H], 1.64Ϫ2.06 (m, 7 H), 3.58 (s, 3 H, CH3), 3.69 (s, 3 H,
CH3), 5.62 (d, J ϭ 0.8 Hz, 1 H), 6.19 (d, J ϭ 0.8 Hz, 1 H) ppm.
13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 25.5 (CH2), 26.4 (2
CH2), 34.9 (2 CH), 35.9 (C), 51.7 (CH3), 51.9 (CH3), 126.8 (CH2),
140.9 (C), 166.6 (C), 170.6 (C) ppm. MS (70 eV, EI): m/z (%) ϭ
CH3), 1.25 (s, 3 H, CH3), 1.31 (t, J ϭ 7 Hz, 3 H, CH3), 1.42 (d,
J ϭ 11 Hz, 1 H), 1.47 (d, J ϭ 4.5 Hz, 1 H, CH), 1.59 (dd, J ϭ 4.5,
4.5 Hz, 1 H, CH), 1.67 (dd, J ϭ 11, 4.5 Hz, 1 H), 2.17 (s, 1 H,
CH), 4.23 (q, J ϭ 7 Hz, 2 H, CH2), 5.04 (s, 1 H), 5.90 (s, 1 H)
ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 14.2 (CH3), 19.4
(CH), 23.3 (CH3), 26.7 (CH), 30.3 (CH3), 35.0 (C), 36.1 (CH), 37.7
(CH2), 60.7 (CH2), 119.2 (CH2), 140.6 (C), 167.1 (C) ppm. MS
(70 eV, EI): m/z (%) ϭ 194 (1) [Mϩ], 179 (17) [Mϩ Ϫ CH3], 165
(51) [Mϩ Ϫ C2H5], 151 (10), 149 (12) [Mϩ Ϫ C2H5O], 148 (10) [Mϩ
Ϫ C2H5OH], 147 (12), 133 (39), 123 (6), 121 (38) [Mϩ Ϫ CO2C2H5],
120 (22), 119 (29), 105 (100), 95 (8), 93 (28), 91 (32), 81 (6), 79 (43)
[C6H7ϩ], 77 (28) [C6H5ϩ], 67 (14), 65 (9), 55 (13), 53 (14), 51 (6),
43 (9), 41 (32). C12H18O2 (194.27): calcd. C 74.19, H 9.34; found
C 74.42, H 9.02. endo-7j: Colorless oil. IR (film): ν˜ ϭ 3105, 3037,
3016, 2985, 2953, 2936, 2902, 2865, 1722, 1628, 1464, 1446, 1383,
1364, 1300, 1275, 1249, 1188, 1163, 1110, 1030, 982, 946, 899, 855,
1
819, 777, 743 cmϪ1. H NMR (250 MHz, CDCl3): δ ϭ 0.65 (s, 3
H, CH3), 1.23 (s, 3 H, CH3), 1.30 (t, J ϭ 7 Hz, 3 H, CH3), 1.42 (d,
J ϭ 11.3 Hz, 1 H), 1.56 (dd, J ϭ 11.3, 4.5 Hz, 1 H), 1.63Ϫ1.83 (m,
3 H, 3 CH), 4.23 (q, J ϭ 7 Hz, 2 H, CH2), 5.73 (t, J ϭ 2 Hz, 1 H),
6.38 (t, J ϭ 2 Hz, 1 H) ppm. 13C NMR (62.9 MHz, CDCl3, DEPT):
δ ϭ 11.9 (CH), 14.3 (CH3), 23.4 (CH3), 27.7 (CH), 31.0 (CH), 32.0
(CH2), 32.4 (CH3), 33.5 (C), 60.4 (CH2), 127.8 (CH2), 137.1 (C),
167.8 (C) ppm. MS (70 eV, EI): m/z (%) ϭ 194 (1) [Mϩ], 179 (15)
[Mϩ Ϫ CH3], 165 (88) [Mϩ Ϫ C2H5], 151 (8), 149 (13) [Mϩ
Ϫ
C2H5O], 148 (19) [Mϩ Ϫ C2H5OH], 147 (21), 133 (41), 121 (47)
[Mϩ Ϫ CO2C2H5], 120 (28), 119 (38), 105 (100), 95 (19), 93 (29),
91 (30), 79 (41) [C6H7ϩ], 77 (21) [C6H5ϩ], 67 (14), 65 (7), 55 (14),
53 (9), 43 (8), 41 (24). C12H18O2 (194.27): calcd. C 74.19, H 9.34;
found C 73.96, H 9.23.
224 (2) [Mϩ], 192 (100) [Mϩ Ϫ CH3OH], 177 (1), 164 (21) [Mϩ
Ϫ
CH3OH Ϫ CO], 160 (30), 151 (8), 149 (6), 136 (12), 133 (23), 132
(23), 121 (4), 105 (42), 91 (9), 79 (15), 77 (15), 67 (16), 65 (6), 59
(9), 55 (2), 53 (3), 51 (4), 45 (2), 41 (4). C12H16O4 (224.25): calcd.
C 64.27, H 7.19; found C 64.21, H 7.00.
Methyl exo-2-(Bicyclo[4.1.0]hept-7-yl)propenoate (1k): Methylen-
ation of the oxo ester 7k (18.2 g, 100 mmol) according to GP 5B
gave a crude product (18.4 g), which was subjected to chromatogra-
phy on silica gel (1.5 L), eluting with hexane/tBuOMe (20:1) to
yield pure 1k (16.5 g, 92%). IR (film): ν˜ ϭ 3107, 2996, 2927, 2852,
1721, 1627, 1435, 1403, 1355, 1322, 1264, 1193, 1140, 1082, 1028,
1014, 1001, 916, 872, 842, 813, 773, 734 cmϪ1. 1H NMR (250 MHz,
CDCl3): δ ϭ 1.03 (ddd, J ϭ 5, 4, 1 Hz, 2 H, 2 CH), 1.20Ϫ1.28 (m,
4 H), 1.48 (t, J ϭ 5 Hz, 1 H, CH), 1.64Ϫ1.75 (m, 2 H), 1.80Ϫ1.93
(m, 2 H), 3.76 (s, 3 H, CH3), 5.16 (s, 1 H), 5.91 (d, J ϭ 1 Hz, 1 H)
ppm. 13C NMR (62.9 MHz, CDCl3, DEPT): δ ϭ 21.0 (2 CH), 21.2
(2 CH2), 23.3 (2 CH2), 24.0 (CH), 51.9 (CH3), 118.8 (CH2), 142.9
(C), 168.0 (C) ppm. MS (70 eV, EI): m/z (%) ϭ 180 (24) [Mϩ], 165
(6) [Mϩ Ϫ CH3], 149 (9) [Mϩ Ϫ CH3O], 148 (18) [Mϩ Ϫ CH3OH],
137 (6), 121 (27) [Mϩ Ϫ CO2Me], 120 (37) [Mϩ Ϫ CH3OH Ϫ CO],
120 (28), 111 (3), 105 (17), 93 (29), 92 (36), 91 (70), 81 (100)
[C6H9ϩ], 79 (86) [C6H7ϩ], 77 (51) [C6H5ϩ], 67 (34), 65 (15), 59 (15),
55 (10), 53 (17), 51 (6), 41 (79). HRMS (EI): calcd. for (C11H16O2)
[Mϩ] 180.1150, found 180.1150.
Methyl exo-2-(Bicyclo[3.1.0]hex-6-yl)propenoate (1h): Methylen-
ation of the oxo ester 7h (11.44 g, 68 mmol) according to GP 5B
gave a crude product (12.38 g) as a yellow oil, which was subjected
to chromatography on silica gel (1 L), eluting with pentane/diethyl
ether (20:1) to yield pure 1h (9.6 g, 85%) as a colorless liquid. IR
(film): ν˜ ϭ 3105, 3026, 2952, 2861, 1724, 1624, 1437, 1408, 1336,
1294, 1280, 1252, 1229, 1193, 1174, 1137, 1081, 1053, 998, 926,
1
887, 844, 812 cmϪ1. H NMR (300 MHz, CDCl3): δ ϭ 1.13Ϫ1.30
[m, 1 H, C(3)-H], 1.37 (dd, J ϭ 3.7, 3.5 Hz, 2 H, 2 CH), 1.56 (t,
J ϭ 3.7 Hz, 1 H, CH), 1.59Ϫ1.77 (m, 3 H), 1.85 (dd, J ϭ 12.4,
8 Hz, 2 H), 3.75 (s, 3 H, CH3), 5.18 (d, J ϭ 1 Hz, 1 H), 5.93 (d,
J ϭ 1 Hz, 1 H) ppm. 13C NMR (50.3 MHz, CDCl3, APT): δ ϭ
18.9 (CH), 20.9 (CH2), 27.7 (2 CH2), 28.5 (2 CH), 51.8 (CH3),
119.5 (CH2), 141.9 (C), 167.7 (C) ppm. MS (70 eV, EI): m/z (%) ϭ
166 (37) [Mϩ], 151 (15) [Mϩ Ϫ CH3], 138 (13) [Mϩ Ϫ C2H4], 135
(22) [Mϩ Ϫ CH3O], 134 (70) [Mϩ Ϫ CH3OH], 125 (8), 107 (46)
[Mϩ Ϫ CH3O Ϫ CO], 106 (74) [Mϩ Ϫ CH3OH Ϫ CO], 105 (36)
[Mϩ Ϫ CH3OH Ϫ CO Ϫ H], 100 (6), 93 (16), 91 (51) [C7H7ϩ], 79
(70) [C6H7ϩ], 77 (31) [C6H5ϩ], 67 (100), 65 (21), 59 (20), 53 (20),
51 (12), 43 (42), 41 (40). C10H14O2 (166.22): calcd. C 72.26, H 8.49;
found C 72.09, H 8.20.
Ethyl exo-2-(Bicyclo[4.1.0]hept-2-en-7-yl)propenoate (1m): Methyl-
enation of the oxo ester 7m (7.6 g, 39 mmol) according to GP 5A
Ethyl
2-(2,2-Dimethylbicyclo[2.1.0]pent-5-yl)propenoate
(1j): gave after flash chromatography of the crude product on flash silica
Methylenation of a 3.8:1 mixture of exo/endo isomers of 7j (8.3 g,
42 mmol) according to GP 5B gave a crude mixture of dia-
stereomers of 1j (6.7 g), which was purified by column chromatog-
gel (120 mL), eluting with pentane/ether (20:1), pure 1m (5.7 g,
76%) as a slightly yellow liquid. IR (film): ν˜ ϭ 3032, 2981, 2928,
2853, 1718, 1624, 1457, 1444, 1409, 1395, 1368, 1339, 1301, 1260,
Eur. J. Org. Chem. 2004, 3669Ϫ3678
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3677

A. de Meijere, V. Bagutski, F. Zeuner, U. K. Fischer, V. Rheinberger, N. Moszner
FULL PAPER
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Crystallogr., Sect. E 2003, 59, o1610Ϫo1612.
A. W. Burgstahler, L. O. Weigel, C. G. Schaefer, Synthesis
1976, 767Ϫ768.
V. Guay, P. Brassard, Synthesis 1987, 294Ϫ297.
E. G. J. C. Warmerdam, A. M. C. H. Nieuwendijk, C. G. van
der Kruse, J. Brussee, A. van der Gen, Recl. Trav. Chim. Pays-
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N. K. Capps, G. M. Davies, D. Loaks, R. W. McCabe, D. W.
Young, J. Chem. Soc., Perkin Trans. 1 1991, 12, 3077Ϫ3086.
E. Wenkert, R. S. Greenberg, H.-S. Kim, Helv. Chim. Acta
1987, 70, 2159Ϫ2165.
N. Moszner, unpublished results.
G. Odian, Principles of Polymerization, 3rd ed., John Wiley &
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L. M. Harwood, Aldrichchim. Acta 1985, 18, 25.
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1818Ϫ1824.
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3579Ϫ3587.
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78, 142Ϫ151.
T. Troxler, R. Scheffold, Helv. Chim. Acta 1994, 77,
1193Ϫ1202.
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J. Ratusky, F. Sorm, Collect. Czech. Chem. Commun. 1958,
23, 467Ϫ478.
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1999, 55, 6119Ϫ6128.
J. E. Baldwin, G. E. C. Chang, Tetrahedron 1982, 38, 825Ϫ835;
K. Hofmann, O. Jucker, W. R. Miller, A. C. Young, F. Tausig,
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metry 1995, 6, 683Ϫ684.
1174, 1140, 1099, 1061, 1044, 1027, 940, 923, 861, 845, 811, 789,
724, 696 cmϪ1. 1H NMR (250 MHz, CDCl3): δ ϭ 1.29 (t, J ϭ 7 Hz,
3 H, CH3), 1.29Ϫ1.36 (m, 1 H), 1.43Ϫ1.66 (m, 2 H), 1.77Ϫ2.08 (m,
4 H), 4.20 (q, J ϭ 7 Hz, 2 H, CH2), 5.26 (dd, J ϭ 1, 1 Hz, 1 H),
5.49 (ddd, J ϭ 9.5, 6.5, 2.5 Hz, 1 H, CH), 5.98 (d, J ϭ 1 Hz, 1 H),
6.01Ϫ6.08 (m, 1 H, CH) ppm. 13C NMR (62.9 MHz, CDCl3,
DEPT): δ ϭ 14.1 (CH3), 17.9 (CH2), 20.7 (CH), 20.8 (CH2), 23.8
(2 CH), 60.6 (CH2), 119.8 (CH2), 123.8 (CH), 127.0 (CH), 141.6
(C), 167.0 (C) ppm. MS (70 eV, EI): m/z (%) ϭ 192 (9) [Mϩ], 164
(2) [Mϩ Ϫ C2H4], 163 (12) [Mϩ Ϫ C2H5], 147 (15) [Mϩ Ϫ C2H5O],
[3]
[4]
[5]
[6]
[7]
[8]
[9]
146 (40) [Mϩ Ϫ C2H5OH], 145 (47), 131 (7), 119 (5) [Mϩ
Ϫ
CO2C2H5], 118 (44) [Mϩ Ϫ CO2C2H5 Ϫ H], 117 (98), 114 (100),
105 (7), 103 (6), 91 (66), 86 (42), 79 (87) [C6H7ϩ], 78 (51), 77 (61)
[C6H5ϩ], 65 (11), 53 (5), 51 (4), 41 (14). C12H16O2 (192.25): calcd.
C 74.97, H 8.39; found C 74.71, H 8.32.
[10]
[11]
Polymerizations: The polymerizations were carried out in sealed
glass tubes as described previously.[2] The polymers were reprecipi-
tated from THF/methanol and dried under vacuum to a constant
weight.
[12]
[13]
Poly-1f: 1H NMR (400 MHz, CDCl3): δ ϭ 1.1Ϫ2.6 (br., 8 H), 2.63
(s, 2 H, CH2ϪCϭ), 3.71 (m, 6 H, 2 CH3) ppm.
[14]
[15]
[16]
[17]
1
Poly-1h: H NMR (400 MHz, CDCl3): δ ϭ 1.25Ϫ1.80 (br., 7 H),
2.19 (s, 1 H, CHϪCHϭ), 2.36 (s, 2 H, CH2ϪCϭ), 3.70 (s, 3 H,
CH3), 6.62 (s, 1 H, ϪCHϭ) ppm. 13C NMR (100.6 MHz, CDCl3):
δ ϭ 23.9 (CH2), 31.0 (CH2), 31.8 (CH2), 32.0 (CH2) 46.2 (CH),
47.8 (CH), 51.2 (CH3), 131.0 (C), 147.1 (CH), 168.4 (C) ppm.
[18]
[19]
[20]
[21]
[22]
[23]
[24]
Poly-1i: 1H NMR (400 MHz, CDCl3): δ ϭ 1.25Ϫ1.55 (m, 4 H, CH,
CH3), 1.6Ϫ1.8 (br., 6 H), 2.17 (s, 1 H, CHϪCHϭ), 2.39 (s, 2 H,
CH2ϪCϭ), 4.14 (m, 2 H, CH2), 6.61 (s, 1 H, ϪCHϭ) ppm.
1
Poly-1k: H NMR (400 MHz, CDCl3): δ ϭ 0.84Ϫ2.68 (br., 12 H),
3.74 (s, 3 H, CH3), 6.7Ϫ7.1 (br., 1 H, ϪCHϭ) ppm. 13C NMR
(100.6 MHz, CDCl3): δ ϭ 23.7 (CH2), 25.9Ϫ26.4 (2 CH2), 31.1
(CH2), 32.4 (CH2), 39.2 (CH), 42.7 (CH), 51.6 (CH3), 130.6 (C),
148.0 (CH), 168.5 (C) ppm.
Poly-1l: 1H NMR (400 MHz, CDCl3): δ ϭ 0.95Ϫ1.7 (br., 12 H),
2.27Ϫ2.67 (br., 3 H), 4.19 (m, 2 H, CH2), 6.7Ϫ7.1 (br., 1 H,
ϪCHϭ) ppm. 13C NMR (100.6 MHz, CDCl3): δ ϭ 14.3 (CH3),
25.6Ϫ26.1 (3 CH2), 31.0 (CH2), 32.4 (CH2), 39.2 (CH), 42.5 (CH),
60.3 (CH2), 130.7 (C), 148.0 (CH), 168.1 (C) ppm.
[25]
[26]
[27]
D. S. Yufit, V. Bagutski, J. A. K. Howard, A. de Meijere, Acta
Crystallogr., Sect. E 2004, 60, o40Ϫo42. For stereochemical
assignments of related alkyl methylenecyclopropyl carbinols
see also: M. Lautens, P. H. M. Delanghe, J. Am. Chem. Soc.
1994, 116, 8526Ϫ8535.
Acknowledgments
[28]
[29]
The structural assignment for (R*,S*)-6c was deduced from a
This work was supported by the Fonds der Chemischen Industrie
for the group in Göttingen, and by the European Commission
(Contract G5RD-CT-2001Ϫ00554) for Ivoclar Vivadent AG.
1
comparison of its H NMR spectrum with that of (R*,S*)-6b,
which shows a similar signal order and coupling constants for
2-H, 3-H, and 2Ј-H.
S. Bien, Y. Segal, J. Org. Chem. 1977, 42, 1685Ϫ1688; E. Wen-
kert, M. E. Alonso, B. L. Buckwalter, E. L. Sanchez, J. Am.
Chem. Soc. 1983, 105, 2021Ϫ2029.
[1]
N. Moszner, F. Zeuner, U. K. Fischer, V. Rheinberger, A. de
Meijere, V. Bagutski, Macromol. Rapid Commun. 2003, 24,
269Ϫ273.
Received February 25, 2004
3678
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 3669Ϫ3678