Photocatalytic ring opening of α-epoxyketones: 1,3-Dioxolane formation

Article abstract of DOI:10.1007/s007060200073

Photocatalytic ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate in acetone resulted in the formation of 1,3-dioxolanes as major products through C-O bond cleavage and the formation of alcoholic by-products through C-C bond cleav

Full text of DOI:10.1007/s007060200073

Monatshefte fur Chemie 133, 1045±1053 ꢀ2002)
Photocatalytic Ring Opening
of a-Epoxyketones: 1,3-Dioxolane Formationa
Hamid R.Memarian and Farzad Nikpourb
Ã
University of Isfahan, Faculty of Sciences, Department of Chemistry, 81744 Isfahan, Iran
Summary. Photocatalytic ring opening of ꢀ-epoxyketones by 2,4,6-triphenylpyrylium tetra¯uoro-
borate in acetone resulted in the formation of 1,3-dioxolanes as major products through C±O bond
cleavage and the formation of alcoholic by-products through C±C bond cleavage. The type and nature
of the substituent affects the rate of ring opening.
Keywords. Dioxolanes; Electron transfer; ꢀ-Epoxyketones; Photochemistry; Ring opening.
Introduction
Single electron transfer ꢀSET) induced ring opening of epoxides and ꢀ-epoxyke-
tones has been of great interest for several years and is still under intensive inves-
tigation [1±9]. Such reactions have been recognized as important processes not
only in thermal but also in photochemical transformations. Two types of ring
openings ꢀC±C and C±O bond cleavages) have been observed from epoxide radical
cation intermediates. In the former case, intermediates have been trapped by molec-
ular oxygen or tetracyanoethylene to give trioxolane or oxacyclopentane deriva-
tives [4, 5]. In the case of C±O bond cleavage, proof has been obtained either by
rearrangement to carbonyl compounds [1, 2, 6] or by nucleophilic attack of appro-
priate reagents [3, 8, 9].
In recent studies we have investigated the effect of substituents on the photo-
catalytic ring opening of various ꢀ-epoxyketones by 2,4,6-triphenylpyrylium tetra-
¯uoroborate as a photocatalyst, followed by nucleophilic attack of methanol to
form methyl ether derivatives [10]. The results indicated that electron donating
groups increase the rate of ring opening; however, the stereoselectivity decreased
depending on type and stability of the reaction intermediates. The aim of this
work was to study the effect of substituents on the photocatalytic ring opening
of ꢀ-epoxyketones 1a±f in acetone and to explain the nature of the reaction
intermediate responsible for the formation of the isomericproducts.
a

Dedicated to Prof. Dietrich Dopp of Universitat Duisburg, Germany, for his invaluable help and
encouragement
b
Taken in part from the planned doctoral thesis of F. Nikpour, University of Isfahan
Corresponding author. E-mail: memarian@sci.ui.ac.ir
Ã

1046
H. R. Memarian and F. Nikpour
Results and Discussion
Irradiation of ꢀ-epoxyketones 1a±f and the photocatalyst 2,4,6-triphenylpyrylium
tetra¯uroborate ꢀ2) in a molar ratio of 10:1 in acetone at 400 nm resulted in an
opening of the epoxide ring and formation of 1,3-dioxolanes 3a±e and 4a±f as
major products besides alcoholic products 5a,b and 6.
1
IR and H NMR data gave useful information for the structural assignment of
the photoproducts. The IR spectra of 1,3-dioxolanes 3a±e and 4a±f showed an
increase of aliphatic CH-stretching due to addition of acetone. A shift of the
carbonyl group to higher frequency due to loss of epoxide ring strain after ring
opening is also observed ꢀTable 1).
1
The H NMR spectra showed two singlets for the methyl groups and an AB
system for the hydrogens on the dioxolane ring. The stereochemical assignment of
the isomericdioxolanes was achieved on the following basis:
i) The anisotropiceffects of both aromaticrings on one of the methyl groups in
the cis-products 4a±f causes a shielding of its protons which therefore appear
at higher ®elds in comparison to the other methyl group [11]. The consequence
of this phenomenon is that the difference between the chemical shifts of the
methyl groups in the cis-products 4a±f is greater than that in the trans-products
3a±e.
Table 1. Comparison of the IR data of 1a±f with those of 3a±e and 4a±f ꢀꢁꢀCˆO)=cmÀ 1
)
1
2
3
a
b
c
d
e
f
1670
1660
1665
1660
1665
1645
1690
1684
1678
1688
1680
±
1695
1685
1685
1688
1685
1656

Ring Opening of ꢀ-Epoxyketones
1047
ii) The chemical shifts for 4-H and 5-H of 4a±f ꢀcis-products) are closer to each
other in comparison to those of 3a±e ꢀtrans-products). Semiempirical PM3
calculations on both isomers showed that 5-H is located in the plane of the
phenyl ring, whereas 4-H lies parallel to the phenyl ring of the benzoyl moiety
ꢀFig. 1). This causes a deshielding of 5-H and shielding of 4-H, respectively.
iii) According to the Karplus-Conroy equation [12, 13] and using the Karplus
diagram [14], a larger coupling constant is expected for 4-H and 5-H in the
cis-products 4a±f. The results are summarized in Table 2.
Formations of the alcoholic products 5a,b and 6 has not been observed
upon photocatalytic ring opening of 1a±f in methanol [10] or by BF3 catalyzed
ring opening of 1a,b,d in acetone so far [15]. IR data, H NMR spectra, and a
1
Fig.1. Optimized structures of 3a ꢀa) and 4a ꢀb) from PM3 calculations
Table 2. Structurally relevant 1H NMR chemical shifts ꢀꢂ=ppm) and 1H±1H couplings J=Hz of 3a±e
and 4a±f
ꢂA
4-H
ꢂB
5-H
JAB
CH3
3a
4a
3b
4b
3c
4c
3d
4d
3e
4e
4f
4.93
5.48
4.91
5.45
4.90
5.48
5.20
5.47
5.18
5.49
4.89
5.51
5.75
5.39
5.80
5.42
5.74
5.51
5.73
5.47
5.72
5.35
7.3
8.2
7.3
7.6
7.3
7.6
7.2
7.6
7.1
7.4
7.6
1.42
1.57
1.40
1.49
1.42
1.52
1.43
1.52
1.42
1.53
1.44
1.61
1.81
1.59
1.79
1.60
1.80
1.60
1.79
1.59
1.82
1.60

1048
H. R. Memarian and F. Nikpour
Table 3. Photochemical reactions of 1a±f in acetone catalyzed by 2a
Compound
Irradiation time=hb
Product ꢀyield=%)c
Dioxolanes
Alcohol
trans
cis
ratio 4=3
1a
1b
1c
1d
1e
1f
10
4
3a ꢀ14)
3b ꢀ10)
3c ꢀ11)
3d ꢀ11)
3e ꢀ8)
±
4a ꢀ23)
4b ꢀ28)
4c ꢀ24)
4d ꢀ29)
4e ꢀ27)
4f ꢀ23)
1.64
2.80
2.18
2.64
3.37
±
6 ꢀ30)
6 ꢀ28)
9
5a ꢀ41)
6 ꢀ21)
4
10
4
5b ꢀ42)
5b ꢀ38)
a
Molar ratio of 1a±f:2 ˆ 10:1, [1a±f] ˆ 0.04 M, [2] ˆ 0.004 M; b the times refer to total disappear-
c
ance of starting 1a±f; isolated yield
comparison of their melting points with reported data supported the formation of
these products. It should be mentioned that the formation of 3f has not been
observed, but the conversion of small amount of 1f to its precursor ꢀcorresponding
chalcone) was noticed during the reaction.
We have proposed earlier a complete mechanism for the ring opening of 1a±f
in methanol [10]. Selective excitation of the photocatalyst 2 in the presence of 1a±f
ꢀꢃ ꢀ 400 nm) followed by electron transfer from the latter to photoexcited 2 leads
probably to the formation of three different radical cations 7±9 which should be
considered for the nucleophilic attack of acetone and the formation of dioxolanes.
It should be mentioned that irradiation of 1a±f in the absence of 2 at ꢃ ꢀ 400 nm in
acetone does not result in the formation of any products. The results presented in
Table 3 indicate that the irradiation time for total consumption of 1a±f is directly
related to the extent of electron donating ability of 1a±f towards photoexcited 2.
Furthermore, the electron donating character of 1a±f affects not only the rate of the
ring opening; the ratio of diastereomericdioxolanes is also dependent on the loca-
tion of the additional substituent on the parent molecule 1a. Whereas the methyl or
methoxy groups in the para position of the phenyl ring ꢀ1b or 1d) increase the
rate of the ring opening ꢀshortening of the irradiation time); the same substituent on
the benzoyl group ꢀ1c or 1d) has a smaller effect. The formation of the cis-1,3-
dioxolanes 4a±f is explained either by nucleophilic attack of acetone to the inter-
mediates 7 or 8 from the opposite side to the leaving group ꢀoxygen atom of the
epoxide ring; SN2 mechanism, paths II and IV) or to the intermediate 9 from the
bottom side ꢀpath VI). The observed high diastereoselectivity in this reaction
indicates the participation of the intermediate 8 rather than 9, since the intermedi-
ate 8 should be formed better in a aprotic solvent such as acetone. In contrast to
these results, we have proposed earlier the involvement of the intermediate 9 in
methanol solution because of the non-diastereoselectivity of the reaction [10]. The
formation of alcoholic products 5a,b and 6 is explained by C±C bond cleavage.
The important point is that when the phenyl group attached to the oxirane ring
carries the additional substituent, the formation of diol 6 has been observed; when
this substituent is located on the benzoyl group, the formation of the keto-alcohol
5a,b is observed.

Ring Opening of ꢀ-Epoxyketones
1049
Experimental
Melting points were determined with a Stuart Scienti®c SMP2-apparatus and are uncorrected. IR
spectra were recorded on a Shimadzu IR-435 spectrometer. 1H NMR spectra were measured in CDCl3
solutions containing TMS as an internal standard on a Bruker AW 80 spectrometer ꢀ80 MHz). Mass
spectra were obtained on a MAT 8200 spectrometer. Elemental analyses were performed with a CHN±
O-Rapid analyzer; the results agreed favourably with the calculated values. Preparative layer chroma-
tography ꢀPLC) was carried out on 20 Â 20cm2 plates coated with a 1 mm layer of Merck silica gel
PF254 prepared by applying the silica as a slurry and drying in air. All irradiations were carried out
using a 400 W high-pressure Hg vapour lamp from Narva with cooling of samples in Duran glass by
running cold water. The light was passed through a ®lter solution ꢀ75 g Á dmÀ 3 of NaNO2 and
4.4 g Á dmÀ 3 of CuSO4 in 2.7 M NH4OH) [16] to obtain ꢃ ꢀ 400 nm for the selective excitation of
2 and also to prevent the absorption of light by 1a±f.
A solution of 0.8 mmol of 1a±f in 20cm3 acetone ꢀc ˆ 0.04M) and 0.08mmol of 2 ꢀc ˆ 0.004 M)
was irradiated for the time given in Table 3.

1050
H. R. Memarian and F. Nikpour
Irradiation of 1,3-diphenyl-2,3-epoxy-1-propanone ꢀ1a; C15H12O2)
PLC, petroleum ether:ethyl acetateˆ 12:1, two times; zone 1: 31 mg ꢀ14%) of 3a, washed with n-
pentane, m.p.: 87±89ꢁC ꢀRef. [15]: 90±91ꢁC).
trans-4-Benzoyl-2,2-dimethyl-5-phenyl-1,3-dioxolane ꢀ3a; C18H18O3)
1
IR ꢀKBr): ꢁ ˆ 3025±3055, 2890±2990, 1690, 1590cmÀ 1; H NMR: ꢂ ˆ 1.42 ꢀs, 3H, CH3), 1.61 ꢀs,
3
3H, CH3), AB-system ꢀꢂA ˆ 4.93, ꢂB ˆ 5.51, j JABj ˆ 7.3 Hz, 2H, 4-H, 5-H), 7.10±8.00 ꢀm, 10H,
aromaticH) ppm; zone 2: 51 mg ꢀ23%) of 4a, recrystallized from n-hexane, m.p.: 116±118ꢁC
ꢀRef. [15]: 117±118ꢁC).
cis-4-Benzoyl-2,2-dimethyl-5-phenyl-1,3-dioxolane ꢀ4a; C18H18O3)
1
IR ꢀKBr): ꢁ ˆ 3030±3060, 2910±2995, 1695, 1595cmÀ 1; H NMR: ꢂ ˆ 1,57 ꢀs, 3H, CH3), 1.81 ꢀs,
3
3H, CH3), AB-system ꢀꢂA ˆ 5.48, ꢂB ˆ 5.75, j JABj ˆ 8.2Hz, 2H, 4-H, 5-H), 7.02 ꢀs, 5H, phenyl ring),
7.15±7.55 ꢀm, 5H, benzoyl group) ppm; zone 3: 64mg ꢀ30%) of 6, recrystallized from ethanol=ether,
m.p.: 71±73ꢁC ꢀRef. [17]: 73±74ꢁC).
1,2-Dibenzoyl-1,2-ethanediol ꢀ6; C16H14O4)
1
IR ꢀKBr): ꢁ ˆ 3360±3420, 3050, 2850±2930, 1690, 1680, 1595 cmÀ 1; H NMR: ꢂ ˆ 3.50 ꢀbr s, 2H,
OH), 4.80 ꢀs, 2H, CH), 6.90±8.10 ꢀm, 10H, aromaticH) ppm.
Irradiation of 3-p-methylphenyl-1-phenyl-2,3-epoxy-1,3-propanone ꢀ1b; C16H14O2)
PLC, petroleum ether:ethyl acetateˆ 12:1, two times; zone 1: 23mg ꢀ10%) of 3b, washed with ether,
m.p.: 45±48ꢁC ꢀRef. [15]: 47±48ꢁC).
trans-4-Benzoyl-2,2-dimethyl-5-p-methylphenyl-1,3-dioxolane ꢀ3b; C19H20O3)
1
IR ꢀKBr): ꢁ ˆ 3040, 2860±2995, 1684, 1595 cmÀ 1; H NMR: ꢂ ˆ 1.40 ꢀs, 3H, CH3), 1.59 ꢀs, 3H,
3
CH3), 2.25 ꢀs, 3H, CH3), AB-system ꢀꢂA ˆ 4.91, ꢂB ˆ 5.39, j JABj ˆ 7.3Hz, 2H, 4-H, 5-H), 7.00±7.98
ꢀm, 9H, aromaticH) ppm; zone 2: 66 mg ꢀ28%) of 4b, recrystallized from n-pentane, m.p.: 147±149ꢁC
ꢀRef. [15]: 148±149ꢁC).
cis-4-Benzoyl-2,2-dimethyl-5-p-methylphenyl-1,3-dioxolane ꢀ4b; C19H20O3)
1
IR ꢀKBr): ꢁ ˆ 3040, 2860±2990, 1685, 1590 cmÀ 1; H NMR: ꢂ ˆ 1.49 ꢀs, 3H, CH3), 1.79 ꢀs, 3H,
3
CH3), 2.10 ꢀs, 3H, CH3), AB-system ꢀꢂA ˆ 5.45, ꢂB ˆ 5.80, j JABj ˆ 7.6Hz, 2H, 4-H, 5-H), 6.65±7.55
ꢀm, 9H, aromaticH) ppm; zone 3: 60mg ꢀ28%) of 6, recrystallized from ethanol=ether, m.p.: 71±73ꢁC
ꢀRef. [17]: 73±74ꢁC).
Irradiation of 1-p-methylphenyl-3-phenyl-2,3-epoxy-1-propanone ꢀ1c; C16H14O2)
PLC, petroleum ether:ethyl acetateˆ 12:1, two times; zone 1: 26 mg ꢀ11%) of 3c, washed with n-
pentane=ether, m.p.: 82±83ꢁC.
trans-2,2-Dimethyl-4-p-methylbenzoyl-5-phenyl-1,3-dioxolane ꢀ3c; C19H20O3)
1
IR ꢀKBr): ꢁ ˆ 3040, 2850±2995, 1678, 1610 cmÀ 1; H NMR: ꢂ ˆ 1.42 ꢀs, 3H, CH3), 1.60 ꢀs, 3H,
3
CH3), 2.32 ꢀs, 3H, CH3), AB-system ꢀꢂA ˆ 4.90, ꢂB ˆ 5.42, j JABj ˆ 7.3 Hz, 2H, 4-H, 5-H), AB-system

Ring Opening of ꢀ-Epoxyketones
1051
3
ꢀꢂA ˆ 7.10, ꢂB ˆ 7.85, j JABj ˆ 7.7 Hz, 4H, aromaticH), 7.30 ꢀbs, 5H, aromaticH) ppm; EI-MS ꢀ70 eV,
‡
‡
‡
‡
50ꢁC): m=z ꢀ%) ˆ 238 [M ±CH3COCH3] ꢀ21), 190 [M ±C6H5CHO] ꢀ32), 177 [M ±CH3C6H4CO]
‡
‡
ꢀ49), 119 [CH3C6H4CO ] ꢀ100), 91 ‰C7H7 Š ꢂ86†, 77 ‰C6H5 Š ꢂ32†; zone 2: 56 mg ꢀ24%) of 4c,
washed with n-pentane=ether, m.p.: 132±133ꢁC.
cis-2,2-Dimethyl-4-p-methylbenzoyl-5-phenyl-1,3-dioxolane ꢀ4c; C19H20O3)
1
IR ꢀKBr): ꢁ ˆ 3045, 2900±2995, 1685, 1610 cmÀ 1; H NMR: ꢂ ˆ 1.52 ꢀs, 3H, CH3), 1.80 ꢀs, 3H,
3
CH3), 2.24 ꢀs, 3H, CH3), AB-system ꢀꢂA ˆ 5.48, ꢂB ˆ 5.74, j JABj ˆ 7.6 Hz, 2H, 4-H, 5-H), AB-system
3
ꢀꢂA ˆ 6.90, ꢂB ˆ 7.35, j JABj ˆ 7.7 Hz, 4H, aromaticH), 6.98 ꢀs, 5H, aromaticH) ppm; EI-MS ꢀ70 eV,
‡
‡
‡
50ꢁC): m=z ꢀ%) ˆ 281 [M ±CH3] ꢀ0.3), 238 [M ±CH3COCH3] ꢀ21), 190 [M ±C6H5CHO] ꢀ8), 177
‡
‡
‡
‡
[M ±CH3C6H4CO] ꢀ12), 119 [CH3C6H4CO ] ꢀ100), 91 ‰C7H7 Š ꢂ37†, 77 ‰C6H5 Š ꢂ3†; zone 3: 64 mg
ꢀ41%) of 5a, recrystallized from ethanol=ether, m.p.: 87±89ꢁC ꢀRef. [18]: 90ꢁC).
p-Methylbenzoylmethanol ꢀ5a; C9H10O2)
IR ꢀKBr): ꢁ ˆ 3350±3410, 3050, 2990, 1679, 1610 cmÀ 1; 1H NMR: ꢂ ˆ 2.39 ꢀs, 3H, CH3), 3.26 ꢀbr s,
3
1H, OH), 4.79 ꢀs, 2H, CH2), AB-system ꢀꢂA ˆ 7.22, ꢂB ˆ 7.77, j JABj ˆ 7.5 Hz) ppm.
Irradiation of 3-p-methoxyphenyl-1-phenyl-2,3-epoxy-1-propanone ꢀ1d; C16H14O3)
PLC, petroleum ether:ethyl acetateˆ 10:1, two times; zone 1: 28 mg ꢀ11%) of 3d, washed with n-
pentane=ether, m.p.: 43±47ꢁC ꢀRef. [15]: 47±48ꢁC).
trans-4-Benzoyl-5-p-methoxyphenyl-2,2-dimethyl-1,3-dioxolane ꢀ3d; C19H20O4)
1
IR ꢀKBr): ꢁ ˆ 3060, 2840±2990, 1688, 1616, 1595 cmÀ 1; H NMR: ꢂ ˆ 1.43 ꢀs, 3H, CH3), 1.60 ꢀs,
3
3H, CH3), 3.77 ꢀs, 3H, OCH3), AB-system ꢀꢂA ˆ 5.20, ꢂB ˆ 5.51, j JABj ˆ 7.2 Hz, 2H, 4-H, 5-H), AB-
3
system ꢀꢂA ˆ 6.94, ꢂB ˆ 7.29, j JABj ˆ 8.2Hz, 4H, aromaticH), 7.40±8.00 ꢀm, 5H, aromaticH) ppm;
zone 2: 74mg ꢀ29%) of 4d, recrystallized from n-hexane, m.p.: 127±129ꢁC.
cis-4-Benzoyl-5-p-methoxyphenyl-2,2-dimethyl-1,3-dioxolane ꢀ4d; C19H20O4)
1
IR ꢀKBr): ꢁ ˆ 3010, 2860±2950, 1688, 1620 cmÀ 1; H NMR: ꢂ ˆ 1.52 ꢀs, 3H, CH3), 1.79 ꢀs, 3H,
3
CH3), 3.62 ꢀs, 3H, OCH3), AB-system ꢀꢂA ˆ 5.47, ꢂB ˆ 5.73, j JABj ˆ 7.6 Hz, 2H, 4-H, 5-H), AB-
3
system ꢀꢂA ˆ 6.49, ꢂB ˆ 6.98, j JABj ˆ 8.2Hz, 4H, aromaticH), 7.15±7.55 ꢀm, 5H, aromaticH) ppm;
‡
‡
‡
EI-MS ꢀ70 eV, 60ꢁC): m=z ꢀ%) ˆ 312 [M ] ꢀ3), 254 [M ±CH3COCH3] ꢀ29), 176 [M ±C6H5CO±
‡
‡
OCH3] ꢀ54), 161 [M ±C6H5CO±OCH3±CH3] ꢀ47), 149 [M ±CH3COCH3±C6H5CO] ꢀ23), 105
‡
‡
[C6H5CO ] ꢀ100), 77 ‰C6H5 Š ꢂ35†; zone 3: 45mg ꢀ21%) of 6.
Irradiation of 1-p-methylphenyl-3-phenyl-2,3-epoxy-1-propanone ꢀ1e; C16H14O3)
PLC, petroleum ether:ethyl acetateˆ 10:1, two times; zone 1:20mg ꢀ8%) of 3e, visc ose oil.
trans-4-p-Methoxybenzoyl-2,2-dimethyl-5-phenyl-1,3-dioxolane ꢀ3e; C19H20O4)
IR ꢀ®lm): ꢁ ˆ 3045, 2840±2920, 1680, 1598 cmÀ 1; 1H NMR: ꢂ ˆ 1.42 ꢀs, 3H, CH3), 1.59 ꢀs, 3H, CH3),
3
3.79 ꢀs, 3H, OCH3), AB-system ꢀꢂA ˆ 5.18, ꢂB ˆ 5.47, j JABj ˆ 7.1 Hz, 2H, 4-H, 5-H), AB-system
3
ꢀꢂA ˆ 6.81, ꢂB ˆ 7.90, j JABj ˆ 8.1 Hz, 4H, aromaticH), 7.35 ꢀs, 5H, aromaticH) ppm; EI-MS ꢀ70 eV,
‡
‡
150ꢁC): m=z ꢀ%) ˆ 254 [M ±CH3COCH3] ꢀ92), 177 [M ±CH3OC6H4CO] ꢀ23), 135 [CH3OC6H4

1052
H. R. Memarian and F. Nikpour
‡
‡
‡
‡
CO ] ꢀ100), 119 [M ±CH3OC6H4CO±CH3COCH3] ꢀ14), 107 ‰CH3OC6H4 Š ꢂ9†, 105 ꢀC6H5CO ,
‡
24), 77 ꢀC6H5 , 84); zone 2: 68 mg ꢀ27%) of 4e, recrystallized from n-hexane, m.p.: 121±123ꢁC.
cis-4-p-Methoxybenzoyl-2,2-dimethyl-5-phenyl-1,3-dioxolane ꢀ4e; C19H20O4)
1
IR ꢀKBr): ꢁ ˆ 3050, 2820±2980, 1685, 1600 cmÀ 1; H NMR: ꢂ ˆ 1.53 ꢀs, 3H, CH3), 1.82 ꢀs, 3H,
3
CH3), 3.74 ꢀs, 3H, OCH3), AB-system ꢀꢂA ˆ 5.49, ꢂB ˆ 5.72, j JABj ˆ 7.4 Hz, 2H, 4-H, 5-H), AB-
3
system ꢀꢂA ˆ 6.05, ꢂB ˆ 7.54, j JABj ˆ 8.0 Hz, 4H, aromaticH), 7.00 ꢀs, 5H, aromaticH) ppm; EI-MS
‡
‡
‡
‡
ꢀ70 eV, 50ꢁC): m=z ꢀ%) ˆ 312 [M ] ꢀ1), 254 [M ±CH3COCH3] ꢀ27), 206 [M ±C6H5CHO] ꢀ7), 177
‡
‡
[M ±CH3OC6H4CO] ꢀ12), 135 [CH3OC6H4CO ] ꢀ100), 119 [M ±CH3OC6H4CO±CH3COCH3]
‡
‡
ꢀ50), 107 ‰CH3OC6H4 Š ꢂ8†, 77 ‰C6H5 Š ꢂ14†; zone 3: 69mg ꢀ42%) of 5b, recrystallized from
ether=ethanol, m.p.: 98±100ꢁC ꢀRef. [19]: 100ꢁC).
p-Methoxybenzoylmethanol ꢀ5b; C9H10O3)
IR ꢀKBr): ꢁ ˆ 3380, 1675, 1600 cmÀ 1; 1H NMR: ꢂ ˆ 3.57 ꢀbr s, 1H, OH), 3.80 ꢀs, 3H, OCH3), 4.74 ꢀs,
3
2H, CH2), AB-system ꢀꢂA ˆ 6.91, ꢂB ˆ 7.87, j JABj ˆ 8.2 Hz, 4H, aromaticH) ppm.
Irradiation of 1,3-di-)p-methoxyphenyl)-2,3-epoxy-1-propanone ꢀ1f; C17H16O4)
PLC, petroleum ether:ethyl acetateˆ 10:1, two times; zone 1: 57mg ꢀ23%) of 4f, yellowish viscose
oil.
cis-4-)p-Methoxybenzoyl)-5-methoxyphenyl-2,2-dimethyl-1,3-dioxolane ꢀ4f; C20H22O5)
1
IR ꢀ®lm): ꢁ ˆ 3050, 2830±2920, 1656, 1594cmÀ 1; H NMR: ꢂ ˆ 1.44 ꢀs, 3H, CH3), 1.60 ꢀs, 3H,
3
CH3), 3.74 ꢀs, 3H, OCH3), 3.78 ꢀs, 3H, OCH3), AB-system ꢀꢂA ˆ 4.89, ꢂB ˆ 5.35, j JABj ˆ 7.6 Hz, 2H,
‡
4-H, 5-H), 6.68±7.98 ꢀm, 8H, aromaticH) ppm; EI-MS ꢀ70 eV, 50 ꢁC): m=z ꢀ%) ˆ 284 [M
±
‡
‡
CH3COCH3] ꢀ94), 269 [M ±CH3COCH3±CH3] ꢀ5), 177 [M ±CH3COCH3±CH3OC6H4] ꢀ23), 149
‡
‡
‡
[M ±CH3COCH3±CH3OC6H4CO] ꢀ81), 135 [CH3OC6H4CO ] ꢀ100), 121 ‰CH3OC6H4CH2 Š ꢂ71†,
‡
‡
107 ‰CH3OC6H4 Š ꢂ47†, 92 [C6H5O ] ꢀ51); zone 2: 63mg ꢀ38%) of 5b.
Acknowledgments
We are grateful to the Isfahan University Research Council for partial support of this work and to Prof.

G. Hagele, Universitat Dusseldorf, Germany, for recording the mass spectra.

References
[1] House HO, Ryeson GD ꢀ1961) J Am Chem Soc 83: 979 and references cited therein
[2] Johnson CK, Dominy B, Reusch W ꢀ1963) J Am Chem Soc 85: 3894
[3] Kagan J, Juang PY, Firth BE, Przybytek JT, Sing SP ꢀ1977) Tetrahedron Lett 4289
[4] Futamura S, Kusunose S, Ohta H, Kamiya Y ꢀ1984) J Chem SocPerkin Trans I, 15 and references
cited therein
[5] Miyashi T, Kamata M, Mukai T ꢀ1987) J Am Chem Soc 109: 2780 and references cited therein
[6] Hasegawa E, Ishiyama K, Kato T, Horaguchi T, Shimizu T, Tanaka S, Yamashita Y ꢀ1992) J Org
Chem 57: 5352 and references cited therein
[7] Masaki Y, Miura T, Ochiai M ꢀ1996) Bull Chem Soc Jpn 69: 195
[8] Iranpoor N, Zeynizadeh B ꢀ1998) J Chem Res ꢀS) 466 and references cited therein
[9] Adams RD, Barnard TS, Brosius K ꢀ1999) J Organomet Chem 582

Ring Opening of ꢀ-Epoxyketones
[10] Memarian HR, Hesami A, Nikpour F, Dopp D ꢀ2001) Indian J Chem 40B: 662
1053

[11] Hess M, Meier H, Zeeh B ꢀ1984) Spektrokopische Methoden in der Organischen Chemie.
Thieme, Stuttgart, p 140
[12] Breitmaier E ꢀ1992) Vom NMR-Spektrum zur Strukturformel organischer Verbindungen.
Teubner, Stuttgart, p 40
[13] Harris RK ꢀ1991) Nuclear Magnetic Resonance Spectroscopy. Longman, Essex, p 226
[14] Karplus M ꢀ1939) J Chem Phys 30: 11
[15] Bubel ON, Tishchenco IG, Stasevich GZ, Romanco IL, Abramove AF, Skakovski ED ꢀ1975)
Chem Heterocycl Compd 15: 723
[16] Murov SL ꢀ1973) Handbook of Photochemistry. Dekker, New York, p 79
[17] Cadogan JIG, Ley SV, Pattenden G, Raphael RA, Ress CW ꢀ1996) Dictionary of Organic
Compounds, 6th edn., vol 3. Chapman & Hall, p 3026
[18] Beilstein ꢀ1931) Handbuch der organischen Chemie, Band VII=VIII. Springer, p 550
[19] Beilstein ꢀ1931) Handbuch der organischen Chemie, Band VII=VIII. Springer, p 618
Received June 19, 2001. Accepted )revised) November 28, 2001
È
Verleger: Springer-Verlag KG, Sachsenplatz 4±6, A-1201 Wien. ± Herausgeber: Osterreichische Akademie der Wissenschaften,
È
Dr.-Ignaz-Seipel-Platz 2, A-1010 Wien, und Gesellschaft Osterreichischer Chemiker, Eschenbachgasse 9, A-1010 Wien. ±
È
Redaktion: Wahringer Straꢀe 38, A-1090 Wien. ± Satz und Umbruch: Thomson Press Ltd., Chennai, India. ± Offsetdruck:
Manz Crossmedia, A-1051 Wien. ± Verlagsort: Wien. ± Herstellungsort: Wien. ± Printed in Austria.