The cycloaddition of cyclopropenes to enones

Article abstract of DOI:10.1016/S0040-4039(00)00566-9

A number of 1- and 1,2-disubstituted cyclopropenes undergo [4+2]- cycloaddition to methyl vinyl ketone or acrolein at ambient temperature to produce 2-oxabicyclo[4.1.0]hept-3-enes. When 1-phenyl-2- trimethylsilylcyclopropene is treated with 0.4 mol. equiv. of m- chloroperbenzoic acid, the derived ring-opened enone undergoes [4+2]- cycloaddition to the remaining starting material at ambient temperature. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)00566-9

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 4205–4208
The cycloaddition of cyclopropenes to enones
a
a,∗
b
b
Juma’a R. Al Dulayymi, Mark S. Baird, Helmi H. Hussain, Baker J. Alhourani,
b
c
c
Al-Meqdad Y. Alhabashna, Simon J. Coles and Michael B. Hursthouse
a
Department of Chemistry, University of Wales, Bangor, Gwynedd, LL57 2UW, UK
Chemistry Department, College of Science, Muttah University, Alkarak, P.O.Box 7, Jordan
EPSRC National Crystallography Service, Department of Chemistry, University of Southampton, Southampton,
SO17 1BJ, UK
b
c
Received 2 March 2000; accepted 4 April 2000
Abstract
A number of 1- and 1,2-disubstituted cyclopropenes undergo [4+2]-cycloaddition to methyl vinyl ketone
or acrolein at ambient temperature to produce 2-oxabicyclo[4.1.0]hept-3-enes. When 1-phenyl-2-trimethylsilyl-
cyclopropene is treated with 0.4 mol. equiv. of m-chloroperbenzoic acid, the derived ring-opened enone undergoes
[4+2]-cycloaddition to the remaining starting material at ambient temperature. © 2000 Elsevier Science Ltd. All
rights reserved.
It was reported recently that 1-phenyl-2-trimethylsilylcyclopropene 1 is converted into the crystalline
tetramer 2 in remarkably high yield (85%) when allowed to stand at ambient temperature under vacuum
1
for three weeks. Some of us observed that when 1 was kept at 5°C for an extended period without
2
taking precautions to exclude air, a different crystalline material was obtained. The formation of this
compound appeared to occur most rapidly when 1 was purified by chromatography over silica and then
allowed to stand alone at 20°C, when crystals had begun to be deposited after 18 h; after 7 days NMR
of the crude products showed the almost complete reaction of the cyclopropene and the formation of a
single product. The same product was formed more slowly when 1 was kept in D-chloroform at 20°C,
†
about 10% reaction occurring in 7 days. The product gave a microanalysis consistent with a structure
formed from two molecules of cyclopropene and one oxygen atom; its NMR spectrum included two
trimethylsilyl signals at δ −0.2 and −0.3, two cyclopropane hydrogens as an AB pattern (J 5.2 Hz) at
1
.31 and 1.40 and a second AB system (J 17.0 Hz) at 2.31 and 2.74, together with ten phenyl hydrogens.
3
Its structure was confirmed as being 3 by means of a single crystal X-ray study, the result of which is
shown in Fig. 1.
∗
†
Corresponding author.
No tetramer 2 was detected by NMR under either of these conditions.
0
040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)00566-9
tetl 16845

4
206
Fig. 1. Single crystal X-ray structure determination of 3
This formation of compound 3 appeared to be explained by the [4+2]-cycloaddition of the cyclopro-
pene 1 and the enone 4, to produce a six-membered heterocycle in the boat conformation with atoms
C7 and C9 in RS and SR configurations, respectively. The ring-opening of cyclopropenes to give related
enones on reaction with oxygen is known; thus the indenone 5 is converted into compound 6 with the
4
more electron withdrawing group on the 1-position of the enone. Presumably the cyclopropene 1 must
absorb enough oxygen during work-up or chromatography, or in storage, to be oxidised; nonetheless,
none of the dimer was observed when oxygen was bubbled through a solution of 1 in D-chloroform for 18
h. However, in support of the above mechanism, the oxidation of 1 by 1 mol. equiv. of m-chloroperbenzoic
5
6
acid for 10 min at −40°C led to a mixture of 4 together with a minor isomer 7 (70%; ratio 1.7:1); when
the oxidation of 1 was carried out with 0.4 mol. equiv. of the peracid, the NMR spectrum of the product
initially showed the presence of 4 and 7 together with unreacted 1; after standing for 18 h at 20°C, the
spectrum showed the signals for compound 3, and 7 remained unreacted; the major isomer 4 was no
longer present, apparently having reacted with the excess of cyclopropene.

4
207
There are many examples of cycloaddition of cyclopropenes to dienes, in many cases even at ambient
7
temperature or below. There are also many examples of the addition of alkenes to enones and enals;
with simple alkenes these usually occur at relatively high temperature, although in some cases, and
particularly in the presence of a Lewis acid catalyst they occur at ambient temperature and below.8
However, the formation of 3 as described above would represent the first example of the [4+2]-addition
7
of a cyclopropene to an enone. Although there are a number of examples of 2-oxabicyclo[4.1.0]hept-3-
9
10
enes, most of these are further functionalised with a ketone at C-5; others are derived from 4H-pyrans
1
1
or 4H-pyran-4-ones by cyclopropanation. The cyclopropene 1 was therefore treated with an excess
of methyl vinyl ketone in chloroform for 4 h at 20°C; the adduct 8a was isolated in 91% crude yield
87% after rapid column chromatography);1 a similar product 8b was isolated when 1 was treated with
2
(
acrolein (86%). In contrast, when 1 was allowed to stand with trans-but-2-en-1-al or 4-methylpent-3-
en-2-one, no products of [4+2]-cycloaddition were observed and instead the cyclopropene was slowly
oxidised to give 3.
In order to establish whether this reaction could be applied more widely, a number of other
1
3
cyclopropenes were treated with methyl vinyl ketone or acrolein at 20°C; the results are presented
1
4
in Table 1.
Table 1
Reactions of cyclopropenes with enones to give 2-oxabicyclo[4.1.0]hept-3-enes at 20°C
Under these conditions, no reaction was observed with either mesityl oxide or trans-crotonaldehyde.

4
208
2-Bromo-1-octylcyclopropene did not react with any of the enones, nor did 3-methyl-3-
phenylcyclopropene. In this latter case the steric hindrance caused by the 3-substituents to cycloaddition
to the cyclopropene π-bond has been noted on a number of occasions.7
The use of an appropriate catalyst and of high pressure to promote the [4+2]-cycloaddition with less
reactive enones and cyclopropenes is being examined.
References
1
2
3
. Lee, G.-A.; Chang, C.-Y. Tetrahedron Lett. 1998, 39, 3013.
. Hussain, H. H.; Alhourani, B. J.; Al Alhabashna, M. Y. Unpublished results.
. Crystal data for 3: Formula C12
16
H O0.5Si, MW=196.34, triclinic, space group P1 (no.1), a=6.038 (2), b=9.898(2),
3
3
c=10.640(2) Å, α=108.49(3), β=103.01(3), γ=103.23(3)°, U=555.7(2) Å , Z=2,
D =1.173 Mg/m , µ(Mo-
c
−1
kα)=0.171mm , F(000)=212, crystal size=0.35×0.125×0.125 mm, T=150(2) K. Intensity data were collected on a
2
Nonius KappaCCD area detector diffractometer. The structure was solved by direct methods and refined on F by full-
matrix least-squares (non-H anisotropic, H-atoms isotropic) to final R
1 2
=0.0397 and wR =0.1253 for 3999 unique data and
2
51 parameters. Full details have been deposited with the Cambridge Crystallographic Data Centre (CCDC141103).
4
5
6
. Padwa, A.; Austin, D. J.; Xu, S. L. Tetrahedron Lett. 1991, 32, 4103.
. Baird, M. S.; Hussain, H. H. Tetrahedron Lett. 1986, 27, 5143.
. Further oxidation of the mixture of 4 and 7 with MCPBA for 18 h at 20°C led to the epoxidation of the alkene bond of 4,
but left 7 unchanged.
7
8
. For a review, see: Baird, M. S. Cyclopropanes from Cyclopropenes, in Three and Four Membered Carbocyclic Compounds;
de Meijere, A., Ed.; Houben Weyl E17a, 1996; p. 114.
. See for example: Yamauchi, M.; Katayama, S.; Baba, O.; Watanabe, T. J. Chem. Soc., Perkin Trans. 1 1990, 3041; Takaki,
K.; Okada, M.; Negoro, K. J. Org. Chem. 1982, 47, 1200; Weichert, A.; Hoffmann, H. M. R. J. Org. Chem. 1991, 56, 4098;
Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675; Conrads, M.; Mattay, J. Chem. Ber. 1991, 124, 1425; Bakker,
C. G.; Scheeren, J. W.; Nivard, R. J. F. Rec. Trav. Chim. Pays Bas 1981, 100, 13; Bridges, A. J.; Fisher, J. W. J. Org. Chem.
1
984, 49, 2954; Snider, B.; Phillips, G. B. J. Org. Chem. 1983, 48, 3685; Jao, E.; Slifer, P. B.; Lalancette, R.; Hall, S. S.
J. Org. Chem. 1996, 61, 2865; Seebach, D.; Stucky, G.; Pfammatter, E. Chem. Ber. 1989, 122, 2377; Takaki, K.; Yamada,
M.; Negoro, K. J. Org. Chem. 1982, 47, 5246; Weinstein, B.; Lin, L.-C. C.; Fowler, F. W.; J. Org. Chem. 1980, 45, 1657;
Alder, K.; Ruden, E. Chem. Ber. 1941, 74, 920; Alder, K.; Offermans, H.; Ruder, E. Chem. Ber. 1941, 74, 905; Smith, G.
W.; Norden, D. G.; Ballard, S. A. J. Am. Chem. Soc. 1951, 73, 5267, 5270.
9. Dolejs, L.; Mironov, A.; Sorm, F. Coll. Czech. Chem. Commun. 1961, 1015.
1
1
1
0. See for example: Dimroth, W. Chem. Ber. 1966, 99, 2351, 2357, 2358; Bischofberger, N.; Frei, B.; Wirz, J. Helv. Chim.
Acta 1983, 66, 2489; Frei, B.; Wolf, H. R.; Jeger, O. Helv. Chim. Acta 1979, 62, 1645.
1. Yamaoka, H.; Mishima, I.; Miyamoto, M.; Hanafusa, T. Bull. Chem. Soc. Jpn. 1980, 53, 469; Yamaoka, H.; Mishima, I.;
Hanafusa, T.; Chem. Lett. 1980, 411.
2. A minor product observed in the NMR spectrum of the crude product was provisionally identified as the regioisomeric
adduct. Compound 8a showed δH 7.3–7.7 (5H, m), 4.43 (1H, m), 2.43 (1H, d (J 14.7 Hz) of narrow m), 2.19 (1H, d (J 14.7
Hz) of narrow m), 1.72 (3H, narrow m), 1.34 (1H, d, J 5.3 Hz), 1.30 (1H, br.d, J 5.3 Hz), −0.31 (9H, s); irradiation of the
signal at 1.72 reduced the signal at 4.43 to a dd (J 2.8, 4.6 Hz) and those at 2.43 and 2.19 each to a dd (J 16.8, 2.8 and 16.8,
4
.6 respectively); δC 147.0, 140.3, 129.8, 128.1, 92.2, 68.2, 23.2, 20.4, 15.3, 13.3, −3.0.
1
1
3. Baird, M. S.; Hussain, H. H.; Nethercott, W. J. Chem. Soc., Perkin Trans. 1 1986, 1845; Baird, M. S.; Dale, C. M.; Al
Dulayymi, J. R. J. Chem. Soc., Perkin Trans. 1 1993, 1373.
4. The regiochemistry of 10a and 10b was confirmed by the presence an additional couplings in the H NMR signal for one
1
of the hydrogens on C-5 to the cyclopropane hydrogen on C-6. The regiochemistry of 10e and 10f was assigned by analogy
to 8.