Photochemical preparation of cyclopropanes from cyclobutanones

Article abstract of DOI:10.1139/v00-175

A general method for the preparation of cyclopropanes is reported. Triplet-photosensitized reactions of a series of cyclobutanones give cyclopropanes as the major product. Part 1 describes the synthesis of substituted cyclobutanones used in this study. In Part 2, the photo-reactions of cyclobutanones are reported. Triplet-sensitized reactions of cyclobutanones using acetone as a sensitizer give cyclopropanes as the major non-polar products. The extent of photodecarbonylation seems to be dependent on α-substitution. Electron-donating groups promote decarbonylation while electron-withdrawing groups favour cycloelimination.

Full text of DOI:10.1139/v00-175

114
Photochemical preparation of cyclopropanes from
cyclobutanones
Jailall Ramnauth and Edward Lee-Ruff
Abstract: A general method for the preparation of cyclopropanes is reported. Triplet-photosensitized reactions of a se-
ries of cyclobutanones give cyclopropanes as the major product. Part 1 describes the synthesis of substituted
cyclobutanones used in this study. In Part 2, the photo-reactions of cyclobutanones are reported. Triplet-sensitized reac-
tions of cyclobutanones using acetone as a sensitizer give cyclopropanes as the major non-polar products. The extent of
photodecarbonylation seems to be dependent on α-substitution. Electron-donating groups promote decarbonylation while
electron-withdrawing groups favour cycloelimination.
Key words: photodecarbonylation, cyclobutanones, cyclopropanes, triplet-sensitization.
Résumé : On décrit une méthode générale de préparation des cyclopropanes. Les réactions photosensibilisées de trip-
lets d’une série de cyclobutanones conduisent à des cyclopropanes comme produits majeurs. Dans la première partie,
on décrit la synthèse des cyclobutanones substituées utilisées dans cette étude. Dans la deuxième partie, on décrit les
photoréactions des cyclobutanones. Les réactions sensibilisées de triplets de cyclobutanones utilisant de l’acétone
comme sensibilisateur conduisent à la formation de cyclopropanes comme produits non polaires principaux. Le degré
de photodécarbonylation semble dépendre de la substitution en α. Les groupes électrodonneurs favorisent la
décarbonylation alors que les groupes électroattracteurs favorisent la cycloélimination.
Mots clés : photodécarbonylation, cyclobutanones, cyclopropanes, sensibilisation triplet.
[Traduit par la Rédaction] Ramnauth and Lee-Ruff 120
Introduction
excited cyclobutanone (6). The triplet-sensitized photochem-
istry of cyclobutanones appears to take a completely differ-
ent course of events compared to its singlet state chemistry
and is an area that has been relatively unexplored. The impe-
tus for this work is the increasing availability of cyclobu-
tanones in both chiral and achiral forms (7). With three
centres amenable to functionalization, cyclobutanones could
be valuable precursors to substituted cyclopropanes.
In this paper, we report the synthesis and triplet-
photosensitized reactions of a series of substituted cyclo-
butanones to assess substitution patterns towards photode-
carbonylation.
Small ring compounds have become more than just a curi-
osity to chemists. In particular, cyclopropane-containing
compounds have played an important role in organic synthe-
sis (1). In contrast to simple alkanes and cycloalkanes, such
as cyclopentane and cyclohexane, cyclopropanes participate
in a variety of reactions under mild conditions. This in-
creased reactivity of cyclopropanes has been attributed to the
deformation of bond angles from normal values as well as
torsional effects. Cyclopropane derivatives are also known to
constitute the basic framework of biologically active com-
pounds present in animals, plants, and microorganisms, or to
be generated as intermediates in primary and secondary met-
abolic processes (2).
Results and discussion
A variety of methods are available for the synthesis of
cyclopropanes, but only a few of these have been reported
from ring-contraction reactions of cyclobutane derivatives
(3). In conjunction with our work on the synthesis and
photochemistry of cyclobutanones (4, 5), we are interested
in the photodecarbonylation of cyclobutanones as a potential
route to cyclopropanes. Preliminary studies have indicated
that cyclopropane formation is dominant from a triplet-
Synthesis of cyclobutanones
The optically active cyclobutanone ((–)-4) was prepared
from the cyclobutane diester (1), which was obtained from
cis-pinonic acid of 92% optical purity (8). The latter com-
pound is an oxidation product of the naturally occurring (+)-
α-pinene. The synthesis of (–)-4 was carried out according to
Scheme 1. The diester (1) was reduced with LiAlH4 to the
diol (2) in quantitative yield. This crude diol was then mono-
protected with 1.0 equiv of benzoyl chloride at 0°C to
hydroxy benzoate (3) in 75% yield. This alcohol was then
oxidized under Swern conditions to give cyclobutanone
((–)-4) in 90% yield after flash column chromatography. The
structure of (–)- 4 was ascertained from its spectral and ana-
lytical data.
Received August 14, 2000. Published on the NRC Research
Press Web site on February 16, 2001.
J. Ramnauth and E. Lee-Ruff.1 Department of Chemistry,
York University, Toronto, ON M3J 1P3, Canada.
1Corresponding author (telephone: (416) 736–5443; fax: (416)
736–5936. e-mail: leeruff@yorku.ca).
The racemic 2,2,4-trisubstituted cyclobutanone (5) was syn-
thesized according to a literature procedure; the key step
Can. J. Chem. 79: 114–120 (2001)
© 2001 NRC Canada
DOI: 10.1139/cjc-79-2-114

Ramnauth and Lee-Ruff
115
Scheme 1.
Scheme 2.
Scheme 3.
involved a [2 + 2] cycloaddition of t-butyl acrylate to N,N-
dimethylisobutenylamine (9). This compound was then con-
verted to cyclobutanone 8 according to Scheme 2. The syn-
thesis of 8 involved the reduction of 5 to diol 6 in
quantitative yield followed by protection of its primary
hydroxyl group with 1 equiv of benzoyl chloride at –20°C in
a yield of 85%. This alcohol was then oxidized under Swern
conditions to give the targeted compound 8 in a yield of
87%. The structure of this ketone was confirmed by spectral
and analytical data.
Cyclobutanone derivatives (11a–e) were prepared accord-
ing to Scheme 3. The olefins (9a–e) were prepared by esteri-
fication of the corresponding alcohol with benzoyl chloride
in pyridine in yields ranging from 90–95%. These olefins
were then treated with dichloroketene (generated in situ
from activated zinc with trichloroacetyl chloride) in the pres-
ence of DME (10) to give the cycloadducts (10a–e) in yields
of 80–85%. In all cases, only one regio- and (or) stereo-
1
isomer was obtained as determined by H and 13C NMR.
The regioisomer of the dichloroketene adduct 10c was also
ascertained by X-ray crystallography (11).
These dichlorocyclobutanones were dechlorinated with zinc
powder in acetic acid to give cyclobutanones (11a–e) in high
yields ranging from 85–95%. The structures of all cyclo-
butanones were confirmed by spectral and analytical data.
Cyclobutanone 11a showed 9 peaks in the 13C NMR spec-
trum and a symmetrical pattern for the cyclobutyl protons in
1
the H NMR spectrum. A similar analysis was made for 11b
to confirm its regioisomeric structure. The structures of the
1
regioisomers 11c and 11d were confirmed by 2-D H COSY
1
experiments. The splitting patterns in the H NMR spectra
were consistent with the assigned structures. The
© 2001 NRC Canada

116
Can. J. Chem. Vol. 79, 2001
Scheme 4.
stereochemistry of 11d and 11e was assigned based on the
olefins and cyclopropanes were obtained, relative yields
were determined by H NMR or HPLC analysis.
1
1
starting olefins. Also, 13C and H NMR data showed that
there is no interconversion of the two isomers under the
acidic conditions used in the dechlorination reaction.
The products derived from the photolysis of the different
substituted cyclobutanones are illustrated in Scheme 4. The
yields for the photolyses in acetone are tabulated (Table 1).
For photoreactions in THF, the major products were the
olefins for all of the cyclobutanones except for cyclobu-
tanone 8. For this cyclobutanone, an intractable polymeric
mixture was obtained. This suggests that the initial photo-
products were not stable under these conditions leading to
oligomerization.
Photolyses of cyclobutanones
Photolyses were performed using a medium-pressure mer-
cury arc lamp with a Pyrex filter. Photolyses were conducted
in acetone for the triplet sensitized reactions while compara-
tive non-sensitized irradiations were carried out in THF. The
samples were thoroughly degassed with argon prior to irradi-
ation. The samples were photolyzed for 4 h and the crude
photolysis products were purified by chromatography. Con-
versions were on average >90%. In cases where mixtures of
The structures of all photoproducts were assigned based
on spectral and analytical data. It is evident from the results
that under triplet-sensitized conditions cyclopropanes are the
© 2001 NRC Canada

Ramnauth and Lee-Ruff
Table 1. Yields of photoproducts for photoreactions of cyclobutanones in acetone.
117
Cyclobutanone
Products
Ratio of
Cyclopropane
Olefin
cyclopropane:olefin
(–)-4
8
10a
10b
11a
11b
11c
11d, 11e
(–)-12 (72 %)
14 (85%)
13 (trace)
not detected
19 (65%)a
20 (58%)a
9a (6%)
9b (6%)
9c (10%)
11d (2%), 11e (2%)
1:0
1:0
0:1
0:1
17 (81%)
18 (78%)
14 (64%)
15 (41%), 16 (27%)
13.5:1
13:1
6.4:1
17:1
aRef. 12.
Scheme 5.
major products while olefins are the major products under
non-sensitized conditions. The photodecarbonylation reac-
tion seems to be quite general.
ones 11d and 11e showed that about 10% of the other
epimer was formed. It is likely that the decarbonylation
products undergo equilibration at the 1,4-diradical stage. This
stereochemical scrambling of starting materials does not oc-
cur under non-sensitized conditions. This indicates the pres-
ence of a stereochemically labile triplet 1,4-acyl-alkyl
diradical intermediate under the triplet-sensitized conditions.
The triplet 1,3-diradical formed after decarbonylation would
be expected to undergo rapid epimerization relative to ring
closure which would also allow for equilibration of the final
products.
The cyclopropane photoproducts are photochemically in-
ert under the acetone sensitized conditions, e.g., irradiation
of 16 for 4 h showed no epimerization with complete recov-
ery eliminating the possibility for stereochemical equilibra-
tion at the cyclopropane stage.
It is apparent that the extent of photodecarbonylation is
dependent on the α-substituent. We compared the ratio of
cyclopropane to olefin to look at the efficiency of the
decarbonylation pathway with varying substituents (Table 1).
The results indicate that electron-donating groups promote
decarbonylation. (–)-Cyclobutanone 4 with two electron-
donating methyl groups at the α-position gave cyclopropane
12 as the only product. The lowest ratio of cyclopropane to
olefin was obtained for cyclobutanone 11c which has a weak
electron-withdrawing benzoyloxymethyl group at the α-posi-
tion. In the extreme case, with α,α-dichlorocyclobutanones
10a and 10b, cycloelimination to give 1,1-dichloroalkene is
the only reaction (12).
The stereoisomeric cyclobutanones 11d and 11e provide
examples of cyclobutanones with methyl substituents at the
α-position. But more importantly, they provide a stereo-
chemical probe for epimerization in the photodecarbonyl-
ation reaction. Under triplet-sensitized conditions these two
cyclobutanones gave similar product distributions as deter-
mined by 1H NMR analyses. It was surprising to see that the
products showed no memory effect of the starting cyclo-
butanone stereochemistry unlike the photochemical ring-
expansion under non-sensitized conditions (5).
In general, the extent of epimerization at the α-carbon in
the decarbonylation of cyclobutanones will depend on the
lifetimes of the intermediate acyl-alkyl diradical 19 and the
1,3-diradical 20 (Scheme 5). A thermodynamic equilibration
of these intermediates would give an epimeric mixture of
cyclopropanes. After 1 h of irradiation under triplet-
sensitized conditions, analysis of the unreacted cyclobutan-
Conclusion
It has been shown that triplet-sensitized reactions of
cyclobutanones, using acetone as a sensitizer, gave cyclo-
propanes as the major non-polar products. Under non-
sensitized conditions, the photochemistry of cyclobutanones
gave mostly cycloelimination products. The extent of photo-
decarbonylation seems to be dependent on the nature of the
α-substituents. Electron-donating groups promote decar-
bonylation while electron-withdrawing groups favour
cycloelimination. The triplet-sensitized photoreactions of
E-3-benzoyloxymethyl-2,3-dimethylcyclobutanone (11d) and
Z-3-benzoyloxymethyl-2,3-dimethylcyclobutanone (11e), a pair
of epimeric cyclobutanones, gave a similar product distribu-
tion. The distribution of products does not show any mem-
ory effect of the starting ketone stereochemistry. In both
© 2001 NRC Canada

118
Can. J. Chem. Vol. 79, 2001
cases, the major product was E-1-benzoyloxymethyl-1,2-
dimethylcyclopropane, along with its stereoisomer and mi-
nor elimination products. It is evident from these results that
the photodecarbonylation reaction is not stereoselective and
bond rotation in the diradical intermediates occurs faster
than ring closure. Since the cyclobutanones are prepared
from [2 + 2] cycloadditions of alkenes and ketene or ketene
equivalents, this two step process represents an alternate
route for cyclopropanations under neutral conditions which
could find many applications. The reaction can also be a po-
tential route to sterically congested cyclopropanes.
dry pyridine (20 mL) over a period of 30 min. The reaction
was kept at this temperature for 4 h and then allowed to
warm to room temperature. After this time, the reaction mix-
ture was concentrated and diluted with CH2Cl2 (300 mL).
The organic phase was washed with H2O (3 × 50 mL), 1%
HCl (3 × 50 mL), sat. aq NaHCO3 (3 × 50 mL), H2O (2 ×
50 mL) and dried over Na2SO4. Evaporation of the solvent,
followed by flash silica gel chromatography (6:1, hex-
ane:ethyl acetate), gave 5.8 g (75%) of 3. MS m/z: 249 (M + 1).
1
FT-IR (neat) cm–1: 3410, 1719. H NMR (CDCl3) δ: 8.04–
7.42 (m, 5H), 4.29–4.22 (m, 2H), 3.75–3.70 (m, 1H), 2.39–
2.14 (m, 1H), 1.88–1.50 (m, 5H), 1.09 (s, 3H), 0.99 (s, 3H).
13C NMR (CDCl3) δ: 166.7, 133.0, 130.3, 129.6, 128.4,
74.1, 64.1, 43.9, 34.5, 34.4, 29.1, 28.1, 15.2. The crude
product was used for the next step.
Experimental
Melting points (mp) were determined on a Reichert melt-
ing point apparatus and were uncorrected. NMR spectra
were recorded on a Bruker ARX 400 (400 MHz) spectrome-
ter in CDCl3 containing 1% TMS unless otherwise noted.
Chemical shifts are quoted in delta (δ) values in parts per
million (ppm) downfield from TMS (δ = 0). Mass spectra
(MS) were recorded at 70 eV electron impact mode on a
Kratos profile mass spectrometer. Optical rotations were
measured using a Perkin–Elmer 241 polarimeter at 22°C.
Fourier transform infrared spectra (FT-IR) were recorded on
a Pye Unicam SP3–200 spectrometer as thin films or KBr
pellets. HPLC analysis was performed on a Waters M6000A
instrument with a Lamda-Max model 481 LC detector using
UV detection (254 nm), a Hewlett–Packard integrator, and a
Spherisorb Silica analytical column from Sigma–Aldrich.
Elemental analyses were performed by Guelph Chemical
Laboratories Ltd.
Photolyses were carried out using a Hanovia 450 W me-
dium-pressure mercury arc lamp in a water-cooled quartz
immersion well. Pyrex tubes containing the samples were
strapped around this well and the assembly immersed in an
ice water bath. The samples were purged with argon for
30 min prior to irradiation. All solvents used in these reac-
tions were dried and distilled.
A solution of oxalyl chloride (1.25 mL, 15 mmol) in dry
CH2Cl2 (60 mL) was cooled to –60°C with constant stirring
under argon. To this mixture, DMSO (2.0 g, 25 mmol) in
dry CH2Cl2 (12 mL) was added over a 5 min period. After
an additional 10 min of stirring, 3 (2.5 g, 10.1 mmol) in
CH2Cl2 (25 mL) was added over a 5 min period. After
15 min, TEA (7.0 mL) was added over a 5 min period, and
the resulting mixture was allowed to warm to room tempera-
ture. The reaction mixture was treated with H2O (30 mL)
and stirred for 10 min to separate the two layers. The or-
ganic layer was separated and the aqueous layer was ex-
tracted with CH2Cl2 (2 × 50 mL). The combined organic
extract was washed with 2% HCl (2 × 50 mL), H2O
(50 mL), sat. aq NaHCO3 (50 mL), sat. aq NaCl (50 mL),
and dried over MgSO4. Purification by flash silica gel chro-
matography (6.25:1, hexane:ethyl acetate) gave 2.2 g (90%)
of the title compound as a colourless oil. [α]2D2 = –
23.0° (CHCl3, c 1.5). MS m/z: 246. FT-IR (neat) cm–1:
1
1777.1, 1718.3. H NMR (CDCl3) δ: 8.05–7.27 (m, 5H),
4.40–4.36 (m, 2H), 3.21 (dd, J = 8.9, 8.7 Hz, 1H), 2.84 (dd,
J = 7.7, 9.9 Hz, 1H), 2.23–2.10 (m, 2H), 1.93–1.85 (m, 1H),
1.22 (s, 3H), 1.15 (s, 3H). 13C NMR (CDCl3) δ: 214.3,
166.6, 133.1, 130.1, 129.6, 128.5, 63.9, 61.1, 48.6, 33.6,
29.9, 23.4, 17.3. Anal. calcd. for C15H18O3: C 73.14, H 7.37;
found: C 72.94, H 7.76.
Analytical thin layer chromatography (TLC) was per-
formed on commercially prepared silica gel 60F 254 plastic
sheets (E. Merck & Co.). Preparative TLC was performed on
Aldrich silica gel 60F 254 precoated glass plates. For col-
umn chromatography, Silicycle silica gel (flash chromatog-
raphy grade, 20–45 µm) was used.
Synthesis of (±)-2-benzoyloxymethyl-4,4-dimethylcyclo-
butanone (8)
The keto-ester 5 (9) was reduced according to the proce-
dure described for the reduction of diester 1 to give com-
1
Synthesis of (–)-3-[2-(benzoyloxy)ethyl]-2,2-dimethyl-
cyclobutanone (4)
pound 6 (mixture of isomers) in a yield of 98%. H NMR of
major isomer δ: 4.06 (d, J = 7.3 Hz, 1H), 3.86 (t, J =
10.9 Hz, 1H), 3.74 (dd, J = 4.2, 6.8 Hz, 1H), 3.20 (br s, 1H),
3.05 (br s, 1H), 1.62–1.54 (m, 2H), 1.11 (s, 3H), 1.06 (s,
3H). 13C NMR (CDCl3) of major isomer δ: 76.4, 63.2, 37.9,
35.4, 32.3, 28.8, 22.3. This crude diol was used in the next
step without further purification. The hydroxy ester 7 was
prepared in 85% yield by a slightly modified procedure as
described for the preparation of 3. This reaction was con-
To a stirred suspension of LiAlH4 (2.5 g, 65.2 mmol) in
dry Et2O (100 mL) at 0°C under argon was added 1 (8)
(7.0 g, 32.6 mmol) in 60 mL dry Et2O dropwise over a pe-
riod of 30 min. The reaction mixture was then heated to re-
flux for 4 h. After cooling in an ice-water bath the following
were added dropwise in sequence: (i) 2.4 mL H2O in 7.6 mL
THF; (ii) 2.4 mL 15% aq. NaOH; and, (iii) 7.2 mL H2O.
The resulting mixture was stirred at ambient temperature for
an additional 30 min after which it was filtered and washed
with Et2O (3 × 100 mL). The ether extracts were combined
and dried over anhyd Na2SO4 and concentrated to give 4.7 g
(99.7%) of 2. This crude diol was dissolved in dry pyridine
(50 mL) and cooled to 0°C. To this solution was added
dropwise benzoyl chloride (4.4 g, 31.3 mmol, 0.95 equiv) in
1
ducted at –20°C instead of 0°C. H NMR (CDCl3) of major
isomer δ: 8.04–7.26 (m, 5H), 4.73 (dd, J = 1.7, 9.8, Hz, 1H),
4.18 (dd, J = 4.8, 6.6 Hz, 1H), 3.97–3.95 (m, 1H), 2.84 (d,
J = 3.5 Hz, 1H), 2.77–2.73 (m, 1H), 1.76–1.73 (m, 1H),
1.68–1.61 (m, 1H), 1.14 (s, 3H), 1.08 (s, 3H). This com-
pound was oxidized under Swern conditions as before to
give 8 as a colourless oil in a yield of 87% after flash silica
© 2001 NRC Canada

Ramnauth and Lee-Ruff
119
gel chromatography (4:1, hexane:ethyl acetate). MS m/z: 233
(M + 1). FT-IR (neat) cm–1: 1772.6, 1718.5. 1H NMR
(CDCl3) δ: 7.99–7.38 (m, 5H), 4.49 (d, J = 4.9 Hz, 2H),
3.78–3.73 (m, 1H), 2.08 (t, J = 11.0 Hz, 1H), 1.86 (dd, J =
3.2, 8.3 Hz, 1H), 1.24 (s, 3H), 1.18 (s, 3H). 13C NMR
(CDCl3) δ: 214.2, 166.4, 133.1, 129.9, 129.6, 128.4, 62.0,
58.3, 54.2, 30.3, 23.5, 21.7. Anal. calcd. for C14H16O3: C
72.39, H 6.95; found: C 72.25, H 7.07.
47.4, 16.9, 8.6. Anal. calcd. for C14H14Cl2O3: C 55.85, H
4.69; found: C 55.81, H 4.66.
General procedure for the dechlorination of
cyclobutanones 11a–e
A one-neck round-bottom flask was charged with zinc
powder (5 equiv) and glacial acetic acid (1.5 mL/equiv). To
this vigorously stirred suspension was slowly added the
dichlorocyclobutanone (1 equiv) in glacial acetic acid
(1 mL/equiv). After addition, the mixture was heated to
60°C for 30 min. The reaction mixture was cooled, diluted
with anhyd ether (100 mL) and then filtered. The filtrate was
then treated with sat. aq NaHCO3 (5 × 100 mL), sat. aq
NaCl (1 × 100 mL), and dried over Na2SO4. In general, the
crude products contained very little impurity and were puri-
fied using a short plug of silica gel with 4:1 (hexane:ethyl
acetate). Compounds 11c–e were purified by flash silica gel
chromatography, using methylene chloride as the eluent.
General procedure for the preparation of
dichlorocyclobutanones 10a–e
A two-neck round-bottom flask, equipped with a magnetic
stirrer, dropping funnel, and argon inlet was charged with
activated zinc (4 equiv) and the olefin (1 equiv) in anhyd
ether (2 mL mmol–1 of olefin). To this vigorously stirred sus-
pension was added dropwise a mixture of trichloroacetyl
chloride (2 equiv), 1,2-dimethoxyethane (DME) (2 equiv),
and anhyd ether (1 mL mmol–1) over a period of about
30 min. This mixture was stirred overnight at room tempera-
ture. After this time, hexane was added (~50 mL) and the
suspension stirred for 5 min to precipitate the zinc salts. The
solution was then decanted and treated sequentially with
H2O (100 mL), sat. aq NaHCO3 (3 × 100 mL), sat. aq NaCl
(100 mL), and dried over Na2SO4. The syntheses of com-
pounds 10a and 10b have been reported previously (12).
3-Benzoyloxymethylcyclobutanone (11a)
Prepared in 95% yield from compound 10a. FT-IR (neat)
1
cm–1: 1787, 1719. H NMR (CDCl3) δ: 8.04–7.26 (m, 5H),
4.50 (d, J = 6.1 Hz, 2H), 3.29–3.21 (m, 2H), 3.04–2.89 (m,
3H). 13C NMR (CDCl3) δ: 205.9, 166.4, 133.2, 129.8, 129.6,
128.5, 67.2, 50.1, 23.0. Anal. calcd. for C12H12O3: C 70.58,
H 5.92; found: C 70.65, H 5.76.
4-Benzoyloxymethyl-2,2-dichloro-3,3-dimethylcyclobutanone
(10c)
3-[2-(Benzoyloxy)ethyl]cyclobutanone (11b)
Prepared in 93% yield from 10b. FT-IR (neat) cm–1: 1786,
Prepared from olefin 9 c in 82% yield. The crude product
was recrystallized from hexane to give creamish coloured
1
1718. H NMR (CDCl3) δ: 8.04–7.43 (m, 5H), 4.40 (t, J =
6.1 Hz, 2H), 3.28–3.20 (m, 2H), 2.86–2.79 (m, 2H), 2.60–
2.56 (m, 1H), 2.12–2.07 (m, 2H). 13C NMR (CDCl3) δ:
207.2, 166.5, 133.1, 130.1, 129.5, 128.4, 63.7, 52.7, 35.0,
21.4. Anal. calcd. for C13H14O3: C 71.55, H 6.47; found: C
71.73, H 6.37.
1
crystals, mp 61–62°C. FT-IR (KBr) cm–1: 1801, 1716. H
NMR (CDCl3) δ: 8.02–7.44 (m, 5H), 4.62 (dd, J = 5.0,
6.8 Hz, 1H), 4.46 (dd, J = 3.1, 8.7 Hz, 1H), 3.94 (dd, J =
3.2, 5.6 Hz, 1H), 1.58 (s, 3H), 1.36 (s, 3H). 13C NMR
(CDCl3) δ: 192.3, 166.0, 133.4, 129.6, 129.4, 128.6, 91.9,
62.6, 59.0, 45.1, 24.5, 21.1. Anal. calcd. for C14H14Cl2O3:
C 55.85, H 4.69; found: C 56.00, H 4.81.
2-Benzoyloxymethyl-3,3-dimethylcyclobutanone (11c)
Prepared in 95% yield from compound 10c. FT-IR (neat)
1
cm–1: 1779, 1720. H NMR (CDCl3) δ: 8.02–7.42 (m, 5H),
E-3-Benzoyloxymethyl-2,2-dichloro-3,4-dimethylcyclobu-
tanone (10d)
4.54 (dd, J = 4.9, 6.8 Hz, 1H), 4.45 (dd, J = 3.0, 8.8 Hz,
1H), 2.97–2.91 (m, 1H), 2.70 (dd, J = 2.5, 14.5 Hz, 1H),
2.66 (dd, J = 1.3, 16.1 Hz, 1H), 1.49 (s, 3H), 1.29 (s, 3H).
13C NMR (CDCl3) δ: 205.5, 166.2, 133.1, 129.9, 129.6,
128.5, 66.2, 59.9, 58.5, 30.0, 29.6, 22.8. Anal. calcd. for
C14H16O3: C 72.39, H 6.95; found: C 72.34, H 6.84.
Prepared in 81% yield from olefin 9d. The crude product
was passed through a short plug of silica gel to give a white
solid, mp 99–100°C. FT-IR (neat) cm–1: 1800, 1726. 1H
NMR (CDCl3) δ: 8.26–7.65 (m, 5H), 4.87 (d, J = 11.6 Hz,
1H) 4.81 (d, J = 11.6 Hz, 1H), 3.93 (q, J = 7.1 Hz, 1H), 1.55
(s, 3H), 1.39 (d, J = 7.0 Hz, 3H). 13C NMR (CDCl3) δ:
194.9, 166.0, 133.4, 129.7, 129.5, 128.6, 90.2, 68.5, 56.0,
47.4, 16.9, 8.6. Anal. calcd. for C14H14Cl2O3: C 55.85, H
4.69; found: C 55.80, H 4.83.
E-3-Benzoyloxymethyl-2,3-dimethylcyclobutanone (11d)
Prepared in 85% yield from 10d. FT-IR (neat) cm–1: 1780,
1
1720. H NMR (CDCl3) δ: 8.04–7.44 (m, 5H), 4.42 (s, 2H),
3.32 (m, 1H), 3.16 (d, J = 19.6 Hz, 1H), 2.59 (d, J =
16.8 Hz, 1H), 1.24 (s, 3H), 1.09 (d, J = 7.5 Hz, 3H). 13C
NMR (CDCl3) δ: 208.6, 166.4, 133.3, 129.8, 129.6, 128.6,
58.9, 54.0, 32.5, 18.2, 8.5. Anal. calcd. for C14H16O3: C
72.39, H 6.95; found: C 72.34, H 7.24.
Z-3-Benzoyloxymethyl-2,2-dichloro-3,4-dimethylcyclo-
butanone (10e)
Prepared in 81% yield from olefin 9e. The crude product
was passed through a short plug of silica gel to give a vis-
cous yellow oil which solidified on standing at –10°C over-
night, mp 75–76°C. FT-IR (neat) cm–1: 1800, 1726. 1H
NMR (CDCl3) δ: 8.03–7.52 (m, 5H), 4.63 (d, J = 11.9 Hz,
1H) 4.51(d, J = 11.9 Hz, 1H), 3.71 (q, J = 7.5 Hz, 1H), 1.65
(s, 3H), 1.37 (d, J = 7.0 Hz, 3H). 13C NMR (CDCl3) δ:
194.9, 166.0, 133.4, 129.7, 129.5, 128.6, 90.2, 68.5, 56.0,
Z-3-Benzoyloxymethyl-2,3-dimethylcyclobutanone (11e)
Prepared in 87% yield from 10e. FT-IR (neat): 1780,
1
1720 cm–1. H NMR (CDCl3) δ: 8.06–7.50 (m, 5H), 4.43
(dd, J = 11.7, 15.8 Hz, 2H), 3.23–3.21 (m, 1H), 3.00 (s, 2H),
1.57 (s, 3H), 1.23 (d, J = 7.0 Hz, 3H). 13C NMR (CDCl3) δ:
208.5, 166.2, 133.2, 129.7, 129.6, 128.6, 68.2, 62.1, 53.9,
© 2001 NRC Canada

120
Can. J. Chem. Vol. 79, 2001
32.9, 24.5, 8.3. Anal. calcd. for C14H16O3: C 72.39, H 6.95;
found: C 72.36, H 6.79.
Acknowledgments
We would like to thank the Natural Sciences and Engi-
neering Research Council of Canada (NSERC) for financial
support.
(–)-Cyclopropane (12)
Prepared in 72% yield from (–)-cyclobutanone 4. [α]D22
=
–12.1° (CHCl3, c 0.7). MS m/z: 218 (M+). H NMR (CDCl3)
δ: 8.07–7.42 (m, 5H), 4.39–4.36 (t, J = 6.9 Hz, 2H), 1.88–
1.83 (m, 1H), 1.73–1.67 (m, 1H), 1.08 (s, 3H), 1.05 (s, 3H),
0.60–0.59 (m, 1H), 0.47–0.44 (m, 1H), 0.00 (t, J = 4.7 Hz,
1H). 13C NMR (CDCl3) δ: 166.7, 132.8, 130.6, 129.6, 128.3,
65.5, 29.1, 27.4, 21.2, 20.0, 19.5, 15.3. Anal. calcd. for
C14H18O2: C 77.03, H 8.31; found: C 76.84, H 8.55.
1
References
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Chem. 52, 3693 (1987).
Olefin (13)
1H NMR (CDCl3) δ: 8.05–7.42 (m, 5H), 5.20–5.18 (m,
1H), 4.29 (t, J = 7.0 Hz, 2H), 2.46–2.49 (m, 2H), 1.72 (s,
3H), 1.66 (s, 3H).
1-Benzoyloxymethyl-2,2-dimethylcyclopropane (14)
1
Prepared in 85% yield from cyclobutanone 8. H NMR
(CDCl3) δ: 8.09–7.45 (m, 5H), 4.52 (dd, J = 4.9, 6.9 Hz, 1H),
4.17 (dd, J = 2.8, 8.7 Hz, 1H), 1.18 (s, 3H), 1.13 (s, 3H),
1.10–1.09 (m, 1H), 0.62 (dd, J = 4.1, 4.5 Hz, 1H), 0.31 (t,
J = 4.9 Hz, 1H). 13C NMR (CDCl3) δ: 166.8, 132.8, 130.6,
129.6, 128.3, 66.7, 27.1, 22.6, 20.1, 18.8, 16.4. Anal. calcd.
for C13H16O2: C 76.43, H 7.89; found: C 76.16, H 8.17.
11. E. Lee-Ruff and J. Ramnauth. Acta Cryst. Section C, 54,
IUC9800029 (1998).
12. J. Ramnauth and E. Lee-Ruff. Can. J. Chem. 77, 1245 (1999).
© 2001 NRC Canada