Photochemical transformations of chalcone-podands into cyclobutane- containing benzocrown ethers

Article abstract of DOI:10.1007/s11172-009-0154-8

A method for the synthesis of cyclobutane-containing benzocrown ethers by the template photocycloaddition of the corresponding chalcone-podands in solutions was developed. It was shown by X-ray diffraction analysis, 1H and 13C NMR, and UV spectroscopy tha

Full text of DOI:10.1007/s11172-009-0154-8

Russian Chemical Bulletin, International Edition, Vol. 58, No. 6, pp. 1180—1191, June, 2009
1180
Photochemical transformations of chalconeꢀpodands
into cyclobutaneꢀcontaining benzocrown ethers*
I. G. Ovchinnikova, O. V. Fedorova, E. G. Matochkina, M. I. Kodess, P. A. Slepukhin, and G. L. Rusinov
I. Ya. Postovsky Institute of Organic Chemistry, Ural Branch of the Russian Academy of Sciences,
22/20 ul. S. Kovalevskoi, 620041 Ekaterinburg, Russian Federation.
Fax: +7 (343) 374 1189. Eꢀmail: iov@ios.uran.ru
A method for the synthesis of cyclobutaneꢀcontaining benzocrown ethers by the template
photocycloaddition of the corresponding chalconeꢀpodands in solutions was developed. It was
shown by Xꢀray diffraction analysis, 1H and 13C NMR, and UV spectroscopy that the intraꢀ
molecular [2π+2π] photocycloaddition (PCA) is stereoselective with the predominant formaꢀ
tion of structures of the βꢀ and γꢀtruxinic type. The PCA rate was shown to depend on the size
of the oxyethylene spacer and stereoorientation of the chalcone fragments in the podands.
The selectivity of the PCA process can be controlled by a change in the concentration of the
template (alkaline metal ions) and variation of the wavelength range of irradiation.
Key words: chalcones, podands, crown ethers, [2+2] cycloaddition, cyclobutanes, photoꢀ
chemistry.
The cinnamyl derivatives (chalcones) prone to photoꢀ
minal vinyl groups in the paraꢀposition to the polyether
chain was provided by the stacking interaction of the
aromatic substituents.12—14 However, attempts to enhance
the selectivity of the PCA process, including the use of
metal cations as templates, by irradiation of solutions
of the podands containing cinnamic acid residues in the
1,ωꢀpositions were unsuccessful.15,16
induced [2π+2π] photocycloaddition (PCA) evoke inꢀ
creased interest due to a possibility of using them as ligands
with the photocontrolled properties.1—3 However, the
choice of this type of compounds as molecular switchers
requires high regioꢀ and stereoselectivity of PCA proꢀ
cesses.4 The regioselectivity of pericyclic reactions
depends on the preꢀorganization of the reacting ethylene
groups. Two types of cycloaddition are possible: “headꢀ
toꢀhead” or “headꢀtoꢀtail.” 4,5 It is Еꢀisomers that are
usually involved in the PCA reaction. At the same time,
conformational transitions of chalcones can affect, to a
considerable extent, the reactivity of the CH=CH bonds
and stereoisomerism of the PCA products.6 As a rule, the
photoinduced dimerization reactions of cinnamic acid
derivatives in solutions occur with low stereoꢀ and
regioselectivity and afford a mixture of cyclobutaneꢀ
containing stereoisomers including those with the αꢀ,
εꢀtruxillic and βꢀ, γꢀtruxinic structures.4,5 However, on
going to macromolecules (crown ethers, podands)
capable of preꢀorganization, the regioꢀ and stereoselecꢀ
tivity of the PCA processes were considerably enhanced
in some cases.1,2 For example, the principle of valence
preꢀorganization of ethylene groups in chalconeꢀcontainꢀ
ing cyclophanes was used to obtain cyclophanes with
cyclobutane fragments.7—11 A noticeable selectivity of the
intramolecular photocycloaddition process in noncyclic
analogs of dibenzocrown ethers (podands) with the terꢀ
We have earlier studied17 the influence of the preꢀ
organization of the chalconeꢀpodand molecules with the
propenone group in the orthoꢀposition of the bridging aryl
Scheme 1
* Dedicated to Academician O. N. Chupakhin on the occasion
of his 75th birthday.
n = 0 (a), 1 (b), 2 (c).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1150—1160, June, 2009.
1066ꢀ5285/09/5806ꢀ1180 © 2009 Springer Science+Business Media, Inc.

Photochemistry of chalconeꢀpodands
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1181
substituent to the oxyethylene fragment in crystals on
their ability to undergo topochemical intermolecular PCA
reactions. Based on the Xꢀray diffraction data, we preꢀ
dicted the highest probability of the photochemical [2+2]
cycloaddition in the solid phase for the podands with the
phenyl substituents and oxyethylene fragment containing
two or three oxygen atoms (1a,b) (Scheme 1). In the
present work, in order to develop methods for the syntheꢀ
sis of cyclobutaneꢀcontaining crown ethers, we studied
the tendency of chalconeꢀpodands 1a—c to undergo PCA
transformations in solutions and the influence of such
factors as the template effect and preꢀorganization of
ligands on the regioselectivity of intramolecular [2π+2π]
photocycloaddition.
Fig. 1. Stereoorientation of the enone in compounds 1a—c
(arrows show the main correlations observed in the 2D NOESY
experiment).
transꢀsꢀcis conformation and is stabilized in crystals as
structure A (Fig. 1). The sꢀcis conformation is confirmed
Results and Discussion
1
by the results of 2D H—1H NOESY experiments for soꢀ
Stereoorientation of the chalcone groups in podand
molecules 1a—c has a decisive significance in photocycloꢀ
addition processes. Judging from the vicinal spinꢀspin
coupling constants (SSCC) of the olefinic protons in the
1H NMR spectra, the products of the Claisen—Schmidt
aldol condensation (see Scheme 1) are predominantly
formed as Еꢀisomers (Table 1). The chemical shifts of
these protons are very close, and their identification from
usual 1H NMR spectra is difficult. The unambiguous
lutions of compound 1 in DMSOꢀd6. However, the analyꢀ
sis of the intensity of the cross peaks suggests that the
elongation of the oxyethylene fragment facilitates
the conformational transition due to the rotation about the
C(1)—Cβ bond from structure A characteristic of comꢀ
pound 1a to structure B, which is more preferential for
compounds 1b,c. The decrease in the energy barrier to
rotation is due, probably, to the elongation of this bond
to 1.460(2) Å for compounds 1b,c compared to 1.438(2) Å
for compound 1a (Xꢀray diffraction data).17 In our
opinion, this transition explains the above changes in
chemical shifts of the protons of the CH=CH fragment
in compounds 1a—c.
1
assignment of H and 13C signals was performed using
2D 1H—13C HSQC and HMBC experiments. In the
13C NMR spectra, the signals for the olefinic carbon
atoms differ significantly in the chemical shifts: δCα ≈ 122
and δC ≈ 139, which makes it possible to identify the
correspβonding protons by the 2D HSQC data (see Table 1).
This assignment is also confirmed by the results of 2D HMBC
experiments in which the crossꢀpeaks between the nuclei
pairs H(6)—C(β) and H(β)—C(2) are observed. It is noteꢀ
worthy that the positions of the signals for the olefinic
1
protons in the H NMR spectra change with the elongaꢀ
tion of the oxyethylene fragment in compound 1: at n = 0
(1a) the signal of the Hα proton appears in a lower field
and the difference in the chemical shifts Δαβ is 0.16,
whereas at n = 1, 2 (1b,c), it is the Hβ protons that unꢀ
dergo a downfield shift and the Δαβ difference decreases
substantially.
According to the Xꢀray diffraction data,17 the propenone
fragment of chalconeꢀpodand molecules 1a,b exists in the
Table 1. 1H and 13C NMR spectral parameters of the CH=CH
fragment in compounds 1a—c
Comꢀ
pound
δ
3JH ,H /Hz
α β
Нα
Нβ
Δαβ
Сα
Сβ
1a
1b
1c
8.02
7.96
7.97
7.86
8.02
7.99
0.16 122.65 139.81
–0.06 122.33 139.15
–0.02 122.27 139.24
15.9
15.8
15.8

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
Ovchinnikova et al.
As a rule, the mechanism of photoinduced [2π+2π]
cycloaddition for olefins (chalcones) is associated with
two routes of photochemical activation of the reactant:
through the singlet state or through triplet excited state
due to intersystem crossing.18 In the former case, the
concerted (through the formation of an excimer) PCA
process occurs allowed by orbital symmetry. Taking into
account that the transꢀsꢀcis conformation of the chalcone
fragment of compounds 1a—c is most stable, the followꢀ
ing variants of intramolecular [π+π] complex formation
are possible: antiꢀ, synꢀ”headꢀtoꢀhead” or antiꢀ, synꢀ
”headꢀtoꢀtail” (A, B, C, and D, respectively). In the
second case, the reaction predominantly proceeds
according to the radical mechanism to form the intermeꢀ
diate 1,4ꢀbiradical.19
signals for the protons of the starting podands and
Zꢀisomers, the spectra contained characteristic signals
of the AA´BB´ spin system, which are attributed to the
stereoisomeric cyclobutane products. In the case of
compound 1a, the major cyclobutane derivative was comꢀ
pound rtctꢀ2a, whereas isomeric cyclobutanes rcttꢀ3b,c
and rttcꢀ4b,c were formed in the case of compound 1b,c
(Scheme 2).
Along with compound 2a, the 1H NMR spectra of the
reaction mixture exhibit trace amounts of two other isoꢀ
meric cyclobutaneꢀcontaining crown ethers with the
signals for the protons of the fourꢀmembered cycles at
δ 5.68 and 3.82, as well as at δ 5.06 and 4.53. These signals
may belong to rtccꢀ3a and rcttꢀ4a, respectively (Scheme 2,
Table 2).
The irradiation of solutions of chalconeꢀpodands
1a—c in DMF or MeCN with both the nonꢀfiltered light
from the incandescent lamp (150 W) and the filtered
light from the mercury lamp (500 W) in the shortꢀwaveꢀ
length ranges with λmax = 366 and 405 nm resulted in the
formation of mixtures of the starting compounds and phoꢀ
tolysis products that were difficult to separate. According
to the 1H NMR spectral data, the E—Zꢀisomerization
processes occurred predominantly (35—40%) in all the
three cases. The presence of Zꢀisomers was confirmed by
the appearance of the signals for the protons of the
CH=CH fragment of the enone at δ 7.27 and 6.66 as
doublets with an SSCC of 12.7 Hz. In addition to the
The content of the cyclobutane isomers in the mixture
varied from 7 to 18%. On going from the visible lightꢀ
irradiation of chalconeꢀpodands 1b,c to the ultraviolet
region, the fraction of cyclobutanes rtccꢀ3b,c increased
noticeably (from 2 to 12%). The decrease in the amount
of chalcones 1b,c due to the photochemical reactions is
observed in the electronic absorption spectra as well. The
decrease in the intensity of two longꢀwavelength absorpꢀ
tion maxima at 344 and 298 nm that characterize the
conjugation system of the chalcone fragment after the
irradiation of the solutions for 2—3 weeks was accomꢀ
panied by the simultaneous hypsochromic shift of the
maximum at 298 nm by 16 nm (Fig. 2). The decrease in
Scheme 2
n = 0 (a), 1 (b), 2 (c).

Photochemistry of chalconeꢀpodands
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1183
Table 2. Ratio of the PCA products after the irradiaꢀ
tion with the filtered light from the mercury lamp
(500 W) of acetonitrile solutions of chalconeꢀpodands
1a—c
terminal groups of the ligands (4.2—8 Å, Xꢀray diffracꢀ
tion data)17 and the kinetic template effect22 from the К+
(Li+, Cs+) ions can enhance the regioꢀ and stereoselecꢀ
tivity of the intramolecular PCA process due to the shortꢀ
ening of this distance.
Ratio of
Ta/nm
Ratio of
In fact, the electronic absorption spectra of irradiated
solutions of compounds 1a—c in the presence of an
equimolar amount of KSCN (KClO4) exhibit rather fast
exponential decrease in the absorbance. The complete
disappearance of the longꢀwavelength absorption maxima
at 298 and 343 nm indicated the occurrence of the PCA
reactions (see Fig. 2). The dimerization processes of the
chalconeꢀpodands differ considerably in time. For comꢀ
pound 1b, the reaction rate is fourfold higher than that for
compounds 1a,c (Fig. 2). First, it was natural to assume
the influence of the correspondence of the size of the
coordinating oxyethylene ligand cavity and the metal
cation radius on the intramolecular dimerization rate.
However, the use of the Li+ cations (0.78 Å) for comꢀ
pound 1a and Cs+ cations (1.65 Å) for compound 1c as
templates only insignificantly shortened the reaction time
(by 3—4 h). It is known that the podands are conformaꢀ
tionally mobile compared to the crown ethers23 and,
hence, manifest a low complexation ability. Therefore, in
our case, they form, most likely, complexes of the “roost”
type, where the guest is arranged at the top of the binding
(oxyethylene fragment) surface of the host.24 That is why,
other factors capable of influencing the rate and selecꢀ
tivity of the PCA process can be the polyether chain length
and stereoorientation of the chalcone terminal groups
of the podands. The problem on the degree of influence of
reactants
stereoisomers (%)
1a : KSCN
1 : 1
2a 3a 4a 5a
258—400
364—456
94
90
5
4
—
5
—
—
1b : KSCN
1 : 1
2b 3b 4b 5b
258—400
364—456
258—400
364—456
258—400
364—456
15 73
53 34
36 50
70 16
—
6
—
9
12
7
7
1 : 3
1 : 6
5
40 14 40
44 44
6
3
9
1c : KSCN
1 : 1
2c 3c 4c 5c
258—400
364—456
258—400
364—456
—
—
—
—
71 13 16
21 70
50 43
10 82
9
7
8
1 : 3
a T is transmission.
the degree of conjugation of the chromophores is related,
correspondingly, to both the formation of the PCA
products and transformation of the Eꢀisomer into the
Zꢀisomer.20,21
On the basis of specific features of the structures17 of
the starting compounds 1a—c, it can be assumed that
the simultaneous influence of the gauche effect22 from the
oxyethylene fragment providing the approach of the
C/mol L–1
c
A
a
A
b
1.0
1.0
0.5
5
3
2
0.5
1c
1a
1
1b
0
250
300
350
λ/nm
250
300
350 λ/nm
10
20
30 t/h
Fig. 2. Electronic absorption spectra of compounds 1a—c (c = 5•10–5 mol L–1) in DMF solutions during the irradiation with the light
from the incandescent lamp (150 W) in the absence (a) and in the presence of the potassium cation (b); c, changes in the concentraꢀ
tions of compounds 1a—c (c0 = 5•10–5 mol L–1) at 25 °C with time, t/h: 59 (1a), 15 (1b), and 67 (1c); kapp = (1.3 0.2)•10–7 (1a),
(1.6 0.25)•10–6 (1b), and (1.0 0.2)•10–7 (1c).

1184
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
Ovchinnikova et al.
C(27)
C(21)
C(2)
C(1)
C(19)
O(2)
C(15)
C(13)
C(10)
C(12)
C(31)
C(2)
C(1)
C(10)
O(1)
C(6)
O(3)
C(5)
C(9)
C(6)
C(7)
C(14)
C(15)
C(26)
C(18)
C(13)
C(3)
C(11)
C(4)
C(9)
C(8)
C(20)
C(12)
O(4)
C(19)
C(18)
C(16)
C(17)
C(21)
C(34)
C(7)
C(8)
C(14)
C(23)
C(33)
C(22)
O(3)
C(27)
C(22)
C(28)
C(3)
O(5)
C(24)
C(11)
C(20)
O(1)
C(32)
C(31)
C(24)
C(25)
C(16)
O(4)
C(30)
C(28)
C(25)
C(32)
C(26)
O(2)
C(29)
C(30)
C(17)
C(4)
C(29)
C(23)
2b
2а
Fig. 3. Geometry of molecules of crown ethers 2a and 2b.
C(32)
C(31)
C(2)
C(4)
C(30)
C(5)
C(6)
C(13)
C(1)
C(6)
O(1)
C(7)
C(33)
О(4)
C(14)
C(12)
C(11)
C(3)
C(2)
C(3)
C(16)
C(15)
C(10)
C(29)
C(27)
C(34)
C(28)
O(5)
C(4)
C(5)
C(7)
C(8)
C(11)
C(17)
C(8)
O(3)
C(1)
C(9)
C(28)
C(27)
O(4)
C(18)
C(19)
C(12)
C(29)
O(2)
C(13)
C(14)
O(3)
C(16)
C(9)
C(26)
C(30)
C(10)
C(15)
C(26)
C(24)
C(25)
C(31)
C(22)
O(6)
C(25)
C(32)
C(33)
O(5)
C(20)
C(23)
C(22)
C(24)
C(20)
O(2)
O(1)
C(36)
C(17)
C(23)
C(34)
C(21)
C(35)
C(28)
C(21)
C(19)
3b
Fig. 4. Geometry of molecules of crown ethers 3b and 3c.
3c
Table 3. Parameters of the 1H and 13C NMR spectra of the
cyclobutane fragment in compounds 2—4
the listed geometric parameters of the molecules was
solved using Xꢀray diffraction analysis and NMR specꢀ
troscopy.
Comꢀ
pound
δ
δ
C
H
The equilibrium shift from the E—Zꢀisomerization
processes toward the PCA reactions in the presence of
equimolar amounts of KSCN in the studied solutions
of podands 1a—c was confirmed by the analysis of the
1H NMR spectra of the reaction mixtures. However, some
distinctions were revealed in the studied processes of
photocycloaddition for compounds 1a and 1b,c. The irraꢀ
diation of chalconeꢀpodand 1a with the filtered light in
Hα Hα´ Hβ Hβ´
Cα
Cα´
Cβ
Cβ´
2a
2b
3b
3c
4b
4c
4.75
4.65
4.01
4.72
45.44
46.59
41.85
41.83
4.85 5.52 5.35 4.75 48.22 41.64 38.64 37.88
4.86 5.49 5.29 4.78 49.04 41.83 38.26 37.47
5.00
4.93
4.63
4.60
47.24
48.83
37.74
34.75

Photochemistry of chalconeꢀpodands
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1185
C(14)
C(16)
C(17)
C(23)
C(31)
C(32)
C(30)
C(22)
C(21)
O(1)
C(5)
C(13)
C(12)
O(3)
O(4)
C(10)
C(33)
C(34)
C(28)
O(5)
C(24)
C(6)
C(4)
C(7)
C(8)
C(9)
C(15)
C(11)
C(18)
C(20)
C(29)
C(27)
C(25)
C(26)
C(19)
O(3)
C(3)
C(2)
O(2)
C(1)
C(19)
C(1)
C(11)
C(8)
C(9)
C(28)
C(20)
C(18)
O(2)
C(29)
C(2)
O(5)
C(12)
C(13)
O(6)
C(30)
C(27)
C(26)
C(21)
C(23)
C(10)
C(15)
C(7)
C(17)
C(3)
C(6)
C(5)
C(22)
C(31)
O(4)
O(1)
C(36)
C(25)
C(24)
C(4)
C(16)
C(35)
C(34)
C(32)
C(33)
4b
4c
Fig. 5. Geometry of molecules of crown ethers 4b and 4c.
the wavelength range with λmax = 366 and 405 nm in the
solution resulted in the regiospecific intramolecular PCA
with the predominant formation of crown ether 2a conꢀ
taining the cyclobutane fragment of the γꢀtruxinic type
with the characteristic spin system of signals for the
Thus, two routes of intramolecular cyclization, viz.,
through both the singlet and triplet excited states, occur
in the solution photolysis of chalconeꢀpodands 1a—c.
The concerted PCA process allowed by the orbital symꢀ
metry is favored by the formation of photoadducts 2, 4,
and 5 upon the irradiation of solutions of the chalconeꢀ
podands with the longerꢀwavelength light (λmax = 405 nm).
In this case, the kinetic template effect of potassium
cations can provide an additional intramolecular approach
of the activated CH=CH bonds of the chalcone fragꢀ
ments up to the formation of excimers. At the same time,
the predominant formation of rtccꢀisomers 3 due to the
shortꢀwavelength ultraviolet irradiation (λmax = 366 nm)
proceeds mainly through the 1,4ꢀbiradical mechanism.
The presence of the benzoyl substituent at the CH=CH
fragment of the chalcone favors, as is known, an increase
1
АА´BB´ protons at δ 4.01—4.74 in the H NMR spectra
(see Scheme 2, Fig. 3, Tables 2, 3).
The pattern of intramolecular PCA processes became
somewhat more complicated with the elongation of the
oxyethylene fragment in the chalconeꢀpodands on going
from 1a to 1b,c. The formation of cyclobutanes rtccꢀ3b,c
was predominantly observed upon the irradiation with the
light with λmax = 366 nm (Fig. 4), whereas upon the irraꢀ
diation with the light with λmax = 405 nm cyclobutanes
rtctꢀ2b (see Fig. 3) and rcttꢀ4c, respectively, were preꢀ
dominantly formed (Fig. 5, see Scheme 2, Tables 2, 3).
The use of a considerable excess of the potassium salt
in the studied solutions of compound 1b led to the equiꢀ
probable formation of crown ethers rtctꢀ2b and rcttꢀ4b
(Fig. 5, see Tables 2, 3), whereas for compound 1c the
further increase in the regioꢀ and stereoselectivity of
formation of photoadduct 4c was observed.
C(18)
О(3)
C(19)
C(17)
C(16)
C(14)
C(33)
C(34)
C(35)
О(2)
C(13)
C(32)
О(4)
It should be mentioned than the elongation of the
oxyethylene fragment in the case of chalconeꢀpodands
1b,c allows another type of packing of the activated double
bonds “headꢀtoꢀtail” C, D to occur, which is allowed by
the orbital symmetry. Indeed, insignificant amounts of
1,3ꢀdiphenacylcyclobutanes rcttꢀ5b,c were found in the
reaction mixtures (Table 2). The Xꢀray diffraction analyꢀ
sis of compound 5c (Fig. 6) and the identical character
of the ABCD spin system of the cyclobutane protons of
C(20)
C(30)
C(15)
C(10)
C(31)
C(12)
C(11)
О(6)
C(29)
C(36)
C(21)
C(9)
C(8)
О(1)
О(5)
C(7)
C(28)
C(27)
C(22)
C(23)
C(24)
C(5)
C(4)
C(6)
C(1)
C(26)
C(2)
1
C(25)
compounds 5b,c in the H NMR spectra in the region
C(3)
δ 5.6—4.7 is evidently in favor of more energetically
favorable variant of intramolecular packing D.
Fig. 6. Geometry of a molecule of crown ether 5c.

1186
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Ovchinnikova et al.
in the constant of singletꢀtriplet conversion (sensitizing
ability).18 Two variants of formation of crown ethers 3 are
possible. The first variant, which is more probable, in our
opinion, is related to the primary formation of the σꢀbond
between the Cα carbon atoms of the adjacent chalcone
groups. The triplet 1,4ꢀbiradical formed as a result of the
intersystem crossing can undergo the conformational shift
from the bulky bridging aryl substituents in the final stage
of cyclization due to a longer lifetime than that of the
singlet state. The second variant is associated with the
E—Zꢀisomerization of one of the terminal groups of
the chalconeꢀpodand and, further, with the subsequent
intramolecular photocycloaddition to form crown ether 3
(see Ref. 25). In the case of this route, the cyclization of
compound 1a would proceed only with the formation of
stereoisomer 3a, because the E—Zꢀisomerization is prefꢀ
erential for this chalconeꢀpodand in the absence of the
template. However, this is not observed.
Another factor affecting the rate and selectivity of the
PCA reactions is the stereoorientation of the chalcone
groups of the initial ligands. It follows from the Xꢀray
diffraction analysis of photoadducts 2—5 (see Figs 3—6)
that the chalconeꢀpodands are involved in the intramoꢀ
lecular dimerization only in the transꢀsꢀcis conformation.
The reaction rate depends on the presence of more reacꢀ
tive structure B of the starting podand (see Fig. 1). In fact,
as it was shown above, although compounds 1a and 1b
have the same sꢀcis arrangement (see Fig. 1) and the
distance between the terminal groups for the former is
considerably shorter than that for the latter (Xꢀray difꢀ
fraction analysis), the PCA reaction rate of the latter with
structure B is 3.5 times higher (see Fig. 2). Thus, the rateꢀ
determining step of photocycloaddition of compound 1a
should be the conformational transition from structure A
to more reactive structure B. An indirect confirmation
can be the mutual orientation of the βꢀprotons of the
fourꢀmembered cycle and the bridging oxygen atoms in
the molecule of crown ether 2а (oriented in the same
direction) and the sꢀcis form of the chalcone groups at the
moment of cyclization corresponding to structure B,
which can be observed in the geometry of this molecule
(see Fig. 3).
diastereomer 5c (see Fig. 6). The “folding angle” ϕ beꢀ
tween two rootꢀmeanꢀsquare planes passing through the
C(8)C(9)C(29) and C(8)C(28)C(29) atoms is 2.3°, and
the fourꢀmembered cycle is almost planar. For antiꢀ”headꢀ
toꢀhead” stereoisomers 2a and 2b, the angle ϕ is 15.8°
(C(7)C(5)C(3)/C(3)C(8)C(7)) and 16.4° (C(8)C(9)C(34)/
C(8)C(17)C(34)), respectively (see Fig. 3). The further
increase in the folding angle is observed on going to
the molecular structures of synꢀ”headꢀtoꢀhead” isomers
4b,c with the angle ϕ equal to 25.3° (C(9)C(26)C(27)/
C(9)C(8)C(27)) and 18.4° (C(28)C(9)C(8)/C(28)C(29)ꢀ
C(8)), respectively (Fig. 5). The maximum deviations
from the planar geometry of the cyclobutane fragment
Table 4. Bond lengths (d) and bond angles (ω) of the cyclobutane
fragments in the crown ethers
Bond
d/Å
Bond angle
rtctꢀ2a
ω/deg
С(5)—С(7)
С(7)—С(8)
С(8)—С(3)
С(3)—С(5)
1.549(2) С(3)—С(5)—С(7)
1.546(2) С(5)—С(7)—С(8)
1.563(2) С(7)—С(8)—С(3)
1.574(2) С(8)—С(3)—С(5)
89.4(9)
90.0(8)
89.9(9)
88.5(8)
rtctꢀ2b
С(9)—С(8)
1.528(3) С(9)—С(8)—С(17) 90.2(16)
С(8)—С(17) 1.565(3) С(8)—С(17)—С(34) 88.9(14)
С(34)—С(17) 1.565(3) С(17)—С(34)—С(9) 88.6(15)
С(9)—С(34) 1.573(3) С(34)—С(9)—С(8) 90.0(14)
rtccꢀ3b
С(8)—С(9)
1.586(2) С(8)—С(9)—С(26) 86.7(13)
С(9)—С(26) 1.564(2) С(9)—С(26)—С(27) 90.6(13)
С(26)—С(27) 1.538(2) С(26)—С(27)—С(8) 88.8(12)
С(8)—С(27) 1.553(2) С(27)—С(8)—С(9) 89.2(12)
rtccꢀ3c
С(8)—С(9)
1.542(2) С(8)—С(9)—С(28) 90.6(11)
С(9)—С(28) 1.561(2) С(9)—С(28)—С(29) 85.3(11)
С(28)—С(29) 1.582(2) С(28)—С(29)—С(8) 89.6(11)
С(8)—С(29) 1.546(1) С(29)—С(8)—С(9) 87.2(11)
rcttꢀ4b
С(8)—С(9)
1.539(2) С(8)—С(9)—С(26) 88.3(14)
С(9)—С(26) 1.579(2) С(9)—С(26)—С(27) 87.9(13)
С(26)—С(27) 1.568(2) С(26)—С(27)—С(8) 88.3(13)
С(27)—С(8) 1.551(2) С(27)—С(8)—С(9) 89.9(13)
In turn, the low PCA rate in the case of chalconeꢀ
podand 1C compared to 1b (see Fig. 2) is related, most
likely, to considerable conformational changes in the
polyether chain during excimer formation.
The analysis of isolated photoadducts 2—5 (see
Figs 3—6) by Xꢀray diffraction and 1H and 13C NMR
spectroscopy revealed some regularities in the change
in the geometric parameters of molecules of the homoꢀ
logs listed.
rcttꢀ4c
С(8)—С(9)
1.546(3) С(8)—С(9)—С(28) 88.8(17)
С(9)—С(28) 1.575(3) С(9)—С(28)—С(29) 88.7(17)
С(28)—С(29) 1.560(3) С(28)—С(29)—С(8) 89.3(17)
С(8)—С(29) 1.547(3) С(29)—С(8)—С(9) 90.3(18)
5c synꢀ”headꢀtoꢀtail”
С(8)—С(9)
1.575(2) С(8)—С(9)—С(28) 89.3(10)
First, there is a certain dependence of the stereoisoꢀ
merism type on the degree of folding of the cyclobutane
ring of the photoadducts. The least angular strain26 of the
fourꢀmembered cycle is observed for synꢀ”headꢀtoꢀtail”
С(9)—С(29) 1.545(2) С(9)—С(29)—С(28) 90.7(10)
С(28)—С(29) 1.582(2) С(8)—С(28)—С(29) 89.0(10)
С(8)—С(28) 1.544(2) С(9)—С(8)—С(28) 91.0(9)

Photochemistry of chalconeꢀpodands
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1187
are characteristic of rtccꢀisomers 3b and 3c; the angle
ϕ is 23.3° (C(9)C(8)C(27)/C(9)C(26)C(27)) and 29.1°
(C(28)C(29)C(8)/C(28)C(9)C(8)), respectively (see
Fig. 4). The change in the degree of folding of the cycloꢀ
butane fragment in the series of homologs 5—2—4—3
agrees with an increase in the dispersion of the bond angle
values of the fourꢀmembered cycle from the optimum
value. The maximum scatter of the values from 90.6°
(C(8)C(9)C(28)) to 85.3° (C(9)C(28)C(29)) was observed
for stereoisomer 3c (Table 4). It can be assumed that the
folding angle value of the fourꢀmembered cycle depends
primarily on the rotation of the phenyl substituents, whose
orientation is controlled, in turn, by the polyether chain
length. In the general case, the elongation of the oxyꢀ
ethylene fragment in the studied crown ethers, except for
compounds 4b,c, increases the angle ϕ and also decreases
the torsional strain of the cycle but, probably, increases its
stabilization.26
(point symmetry C1) all protons and carbon atoms are
chemically nonequivalent (see Fig. 7, Table 3).
In symmetric isomers 2 and 4, the H(β,β´) protons
are identified by the crossꢀpeaks with the C(2) and C(6)
carbon atoms in the HMBC spectrum, and the H(α,α´)
protons are identified by the crossꢀpeaks with the ipsoꢀC
atom of the phenyl substituent (the enumeration of atoms
is given in Experimental).
The α,βꢀprotons in nonsymmetric isomers 3b,c
were assigned similarly, and the differentiation between
the αꢀ and α´ꢀprotons is based on the comparison of the
results of 2D NOESY experiments and Xꢀray diffraction
data for compound 3c. The NOESY spectrum exhibits
crossꢀpeaks between the Hα and Hβ protons, and the
latter, in turn, gives the crossꢀpeak with the Hβ proton.
´
However, these three protons have no crossꢀpeaks with
the most lowꢀfield proton of the cyclic Hα protons
´
(δH 5.5), indicating its opposite orientation in the cycle.
Differences in symmetry of photocycloaddition prodꢀ
ucts 2—5 are also manifested in the NMR spectra. In
stereoisomers rtccꢀ2 and rcttꢀ4 assigned to the point symꢀ
metry groups C2 and CS, respectively, the cyclic protons
form the AA´BB´ spin system. In the 13C NMR spectra,
the signals for the carbon atoms are equivalent in pairs
(Fig. 7, see Table 3), whereas in isomers rtccꢀ3 and rcttꢀ5
At the same time, rather intense crossꢀpeaks between the
Hα proton and the H(6), H(6´) protons are observed,
´
which is consistent with the presence of the shortened
contact between the corresponding protons in crystal,
namely, r(Hα —H(6)) = 2.22 Å, r(Hα —H(6´)) = 2.30 Å.
´
´
In addition, the NOESY spectrum exhibits the crossꢀpeaks
between the α,α´ꢀprotons and orthoꢀprotons of the benꢀ
zoyl substituents, i.e., between the pairs (Hα—H(9)),
(Hα —H(9´)), which made it possible to identify the sigꢀ
nals of the aromatic protons and then the carbon atoms
by the 2D HSQC and HMBC spectra.
´
Hα
Hβ
4
Thus, it was experimentally found that the presence
of alkali metal cations, which can provide an additional
intramolecular approach of the activated CH=CH bonds
of the chalcone fragments due to complex formation, in
solutions of chalconeꢀpodands 1a—c shifts the equilibꢀ
rium to the concerted PCA reaction with the predomiꢀ
nant formation of diastereomers 2a,b and 4c, respectively.
At the same time, the stereoselectivity of the PCA
reaction depends, to a considerable extent, on the length
of the oxyethylene fragment of the initial chalconeꢀ
podands. The shortest polyether chain in chalconeꢀpodand
1a (n = 0) favors the formation of rtctꢀisomer 2a. In the
case of compound 1b (n = 1), rtctꢀ2b and rcttꢀ4b are
formed equiprobably, whereas the chalconeꢀpodand with
the longest oxyethylene fragment (1c, n = 2) is dimerized
predominantly to form rcttꢀ4c. In turn, along with the
polyether chain length, the stereoorientation of the terꢀ
minal groups in compounds 1a—c (the presence of the
more reactive transꢀsꢀcis conformation of the propenone
fragment corresponding to structure B) can substantially
affect the PCA rate.
Hα´ Hβ
Hα Hβ´
3
2
Hβ
Hα
Hα
Hβ
1
5.6 5.4 5.2 5.0
4.8 4.6 4.4 4.2 4.0
δ
Experimental
Fig. 7. Fragments of the 1H NMR spectra (400 MHz, DMSOꢀd6)
for the cyclobutane protons in compounds 2a (1), 2b (2), 3b (3),
and 4b (4).
IR spectra were recorded on a Spectrum One FTIR spectroꢀ
meter (Perkin—Elmer) using a diffuse reflectance sampling

1188
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
Ovchinnikova et al.
accessory (DRA). Electronic absorption spectra of the studied
solutions were obtained on a UVꢀ2401 PC spectrometer (Shimadzu)
in quartz cells 1 cm thick. 1H and 13C NMR spectra were
measured on a Bruker DRXꢀ400 instrument with working
frequencies of 400 and 100 MHz in a DMSOꢀd6 solution using
SiMe4 and DMSOꢀd6 (δ 39.5) as internal standards, respecꢀ
tively. The complete assigCnment of the 1H and 13C signals in the
NMR spectra was performed by 2D COSY, NOESY, HSQC,
and HMBC experiments. Mass spectra (EI) were recorded on a
Varian MAT 311ꢀA instrument. The energy of ionizing electrons
was 70 eV, and the accelerating voltage was 3 eV. The melting
points were determined on a Boetius microheating stage. Thin
layer chromatography was carried out on Silufolꢀ254 plates using
an ethyl acetate—benzene (1 : 1) mixture as eluent and iodine
vapor for detection.
J = 8.4, 7.3, 1.6 Hz); 7.55 (m, 4 H, H(3´)); 7.63 (t, 2 H, H(4´),
J = 7.3 Hz); 7.89 (dd, 2 H, H(6), J = 7.6, 1.6 Hz); 7.97 (d, 2 H,
Hα, J = 15.8 Hz); 8.00 (d, 2 H, Hβ, J = 15.8 Hz); 8.09 (m, 4 H,
H(2´)). 13C NMR, δ: 67.68 (Ar—O—CH2—CH2); 68.89
(Ar—O—CH2—CH2); 69.94 (O—CH2); 112.72 (C(3)); 120.81
(C(5)); 122.27 (Cα); 123.07 (C(1)); 128.30 (C(2´)); 128.72
(C(3´)); 129.74 (C(6)); 132.09 (C(4)); 132.93 (C(4´)); 137.75
(C(1´)); 139.24 (Cβ); 157.74 (C(2)); 189.40 (C=O). IR, ν/cm–1
665; 694, 734, 752 (arom.); 871, 935, 989, 1017; 1052, 1082 (ν ,
:
s
C
arom—O—CAlk); 1117, 1125, 1163, 1180 (ν , ν , CAlk—O—CAlk);
as
1213, 1247 (ν , Carom—O—CAlk); 1275, 1333,s1448, 1489; 1571,
as
1598 (δ, C=C); 1659 (δ, C=O); 2874, 2945 (δ, CAlk—H); 3063
(δ, Carom—H).
Synthesis of cyclobutaneꢀcontaining crown ethers. A (spectroꢀ
photometric studies). Solutions of initial chalconeꢀpodands
1a—c (c = 5•10–5 mol L–1) in DMF in the absence and in the
presence of an equimolar amount of KSCN (KClO4, LiClO4,
CsClO4) (c = 5•10—5 mol L–1) in thinꢀwalled glass vessels were
irradiated with the nonfiltered light from the incandescent lamp
(150 W) at a distance of 30 cm. The reaction course was
monitored at certain time intervals by spectrophotometry
(see Fig. 2).
B. Solutions of compounds 1a—c (~0.01 g, 0.02 mmol) in
the absence and in the presence of 0.02 mmole of KSCN (KClO4)
in DMF or MeCN (10 mL) in thinꢀwalled glass vessels were
irradiated with the nonfiltered light from the incandescent lamp
(power 150 W) at a distance of 30 cm for 2—3 weeks. The
duration of the PCA process was monitored by IR spectroscopy.
After the completion of the reaction, the solvent was evapoꢀ
rated, and the ratio of photoadducts in the reaction mixtures was
estimated by the comparison of integral intensities28 of the
signals for the α,βꢀprotons of the E,Zꢀisomers and cyclobutane
protons in the 1H NMR spectra.
Chalconeꢀpodands 1a—c were synthesized according to an
earlier described procedure.27
1,2ꢀBis[2ꢀ(3ꢀphenylꢀ3ꢀoxopropꢀ1ꢀenꢀ1ꢀyl)phenoxy)]ethane
(1a). The yield was 87%, m.p. 142—144 °C. Calculated (%):
C, 81.01; H, 5.48. C32H26O4. Found (%): C, 81.09; H, 5.51.
UV (DMF), λ/nm: 297 (logε 4.58), 344 (logε 3.11). 1H NMR, δ:
4.63 (s, 4 H, O—CH2); 7.12 (ddd, 2 H, H(5), J = 7.7, 7.5 Hz,
1.0); 7.16 (dd, 4 H, H(3´), J = 8.3, 7.4 Hz); 7.30 (dd, 2 H, H(3),
J = 8.4, 1.0 Hz); 7.47 (tt, 2 H, H(4´), J = 7.4, 1.3 Hz); 7.53
(ddd, 2 H, H(4), J = 8.4, 7.5, 1.7 Hz); 7.81 (dd, 4 H, H(2´),
J = 8.3, 1.3 Hz); 7.83 (d, 2 H, H(6), J = 7.7 Hz); 7.86 (d, 2 H,
Hβ, J = 15.9 Hz); 8.02 (d, 2 H, Hα, J = 15.9 Hz). 13C NMR, δ:
67.00 (O—CH ); 112.57 (C(3)); 121.12 (C(5)); 122.65 (Cα);
123.07 (C(1));2127.91 (C(2´)); 128.36 (C(3´)); 131.50 (C(6));
132.14 (C(4)); 132.66 (C(4´)); 137.51 (C(1´)); 139.81 (Cβ); 157.99
(C(2)); 189.09 (C=O). IR, ν/cm–1: 693, 732, 749, 786 (arom.);
846, 870, 895, 944, 1001, 1018; 1059 (ν , Carom—O—CAlk); 1126,
s
1164, 1180 (ν , ν , CAlk—O); 1203, 1239 (ν , Carom—O—CAlk);
as
s
as
1274, 1338, 1447, 1491; 1567, 1604 (δ, C=C); 1656 (δ, C=O);
2877, 2923, 2946 (δ, CAlk—H); 3060, 3071 (δ, Carom—H).
1,5ꢀBis[2ꢀ(3ꢀphenylꢀ3ꢀoxopropꢀ1ꢀenꢀ1ꢀyl)phenoxy]ꢀ3ꢀoxaꢀ
pentane (1b). The yield was 80%, m.p. 109—110 °C. Calcuꢀ
lated (%): C, 78.76; H, 5.79. C34H30O5. Found (%): C, 78.67;
H, 5.7. UV (DMF), λ/nm: 297 (logε 4.47), 344 (logε 2.97).
1H NMR, δ: 3.98 (m, 4 H, O—CH2); 4.26 (m, 4 H, Ar—O—
CH2); 7.03 (dd, 2 H, H(5), J = 7.6, 7.3 Hz); 7.10 (d, 2 H, H(3),
J = 8.4 Hz); 7.40 (ddd, 2 H, H(4), J = 8.4, 7.3, 1.6 Hz); 7.54
(m, 4 H, H(3´)); 7.63 (t, 2 H, H(4´), J = 7.3 Hz); 7.90 (dd, 2 H,
H(6), J = 7.6, 1.6 Hz); 7.96 (d, 2 H, Hα, J = 15.8 Hz); 8.02 (d,
2 H, Hβ, J = 15.8 Hz); 8.09 (m, 4 H, H(2´)). 13C NMR, δ: 67.77
(Ar—O—CH2); 69.04 (O—CH2); 112.88 (C(3)); 120.89 (C(5));
122.33 (Cα); 123.17 (C(1)); 128.27 (C(2´)); 128.67 (C(3´));
129.58 (C(6)); 132.08 (C(4)); 132.86 (C(4´)); 137.77 (C(1´));
139.15 (Cβ); 157.67 (C(2)); 189.44 (C=O). IR, ν/cm–1: 690,
730, 748, 784 (arom.); 817, 868, 967, 986, 1018; 1035, 1054
(ν , Carom—O—CAlk); 1117 (νas, ν , CAlk—O—CAlk); 1213,
C. Solutions of compounds 1a—c (~0.1 g, 0.2 mmol) in the
absence and in the presence of 0.2, 0.6, and 1.2 mmole of KSCN
(KClO4) in 25 mL of DMF or MeCN in quartz vessels on
cooling (16—18 °C) were irradiated for 24—32 h with the light
from the mercury lamp (power 500 W) using light filters from
the standard set of colored optical glasses in shortꢀwavelength
regions of 258—400 nm (transmission λ
was 366 nm) and
max
364—456 nm (transmission λ
was 405 nm) at a distance of
30 cm. The duration of the PmCaAx process was monitored by IR
spectroscopy. After the completion of the process, the solvent
was evaporated, and the ratio of photoadducts in the reaction
mixtures was estimated by the comparison of integral intensities
of the signals for the α,βꢀprotons of the E,Zꢀisomers and
1
cyclobutane protons in the H NMR spectra (see Table 2). The
PCA products were separated by column chromatography (SiO2)
using benzene—ethyl acetate (1 : 1 or 5 : 1) and ethyl acetate—
acetonitrile (25 : 1) mixtures as eluents.
(12c,13t,14r,15t)ꢀ13,14ꢀDibenzoylꢀ2,5ꢀdioxatetracycloꢀ
[14.4.0.06,11.012,15]eucosaꢀ1(16),6,8,10,17,19ꢀhexaene
(rtctꢀ2a), m.p. 157—158 °C. Calculated (%): C, 81.01; H, 5.48.
C32H26O4. Found (%): C, 80.98; H, 5.49. 1H NMR, δ: 4.01 (m,
2 H, Hβ, Hβ ); 4.08, 4.35 (both m, 2 H each, ArOCH ); 4.75
s
s
1246 (ν , Carom—O—CAlk); 1275, 1328, 1447, 1491; 1567, 1598
s
(δ, C=C); 1650 (δ, C=O); 2827, 2881, 2945 (δ, CAlk—H);
3001, 3058 (δ, Carom—H).
1,8ꢀBis[2ꢀ(3ꢀphenylꢀ3ꢀoxopropꢀ1ꢀenꢀ1ꢀyl)phenoxy)]ꢀ
3,6ꢀdioxaoctane (1c). The yield was 72%, oil. Calculated (%):
C, 76.87; H, 6.05. C36H34O6. Found (%): C, 76.54; H, 6.25.
UV (DMF), λ/nm: 297 (logε 4.32), 344 (logε 2.22). 1H NMR, δ:
3.68 (m, 4 H, O—CH2); 3.84 (m, 4 H, Ar—O—CH2—CH2);
4.19 (m, 4 H, Ar—O—CH2—CH2); 7.02 (dd, 2 H, H(5), J = 7.6,
7.3 Hz); 7.07 (d, 2 H, H(3), J = 8.4 Hz); 7.39 (ddd, 2 H, H(4),
(m, 2 H, Hα´, Hα ); 7.08—7.12 (m, 4 H, H(3), H(3´)2, H(5),
´
H(5´)); 7.25 (td, 2 H, H(4), H(4´), J = 7.6, 1.6 Hz); 7.39 (dd,
4 H, H(10), H(10´), J = 8.2, 7.5 Hz); 7.43 (dd, 2 H, H(6),
H(6´), J = 7.6, 1.6 Hz); 7.56 (tt, 2 H, H(11), H(11´), J = 7.5,
1.2 Hz); 7.83 (dd, 4 H, H(9), H(9´), J = 8.2, 1.2 Hz). 13C NMR,
δ: 41.85 (Cβ, Cβ ); 45.44 (Cα, Cα ); 70.57 (OCH2); 118.68 (C(3),
´
´

Photochemistry of chalconeꢀpodands
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1189
7.27—7.33 (m, 3 H, H(10), H(6´)); 7.45 (tt, 1 H, H(11), J = 7.4,
1.3 Hz); 7.52—7.57 (m, 2 H, H(10´)); 7.64 (tt, 1 H, H(11´),
J = 7.4, 1.4 Hz); 7.70—7.73 (m, 2 H, H(9)); 8.23—8.26 (m, 2 H,
H(9´)). 13C NMR, δ: 37.88 (Cβ ); 38.64 (Cβ); 41.64 (Hα ); 48.22
´
(Hα); 63.93 (CH OAr´); 65.7´6 (O—CH ); 67.20 (O—CH );
67.81 (CH2OAr); 2110.37 (C(3)); 114.23 (C(3´)); 119.31 (C(52));
119.66 (C(5´)); 126.71 and 126.76 (C(4) and C(1´)); 127.29
and 127.32 (C(4´) and C(6´)); 127.42 (C(1)); 128.06 and
128.09 (C(9) and C(10)); 128.69 and 128.71 (C(9´) and C(10´));
129.18 (C(6)); 132.96 (C(11)); 133.47 (C(11´)); 135.19 (C(8));
135.88 (C(8´)); 155.66 (C(2)); 155.70 (C(2´)); 197.54 (C(7));
199.97 (C(7´)). IR, ν/cm–1: 558, 606, 623; 689, 701, 710, 745,
754, 788 (arom.); 827, 843, 900, 913, 920, 935, 984, 1010, 1023;
1039, 1064 (ν , Carom—O—CAlk); 1102, 1127, 1142, 1180 (ν ,
ν , CAlk—O—CAlk); 1212, 1224, 1249 (ν , Carom—O—CAlk);
1a3s24, 1450, 1489; 1581, 1596 (δ, C=C); 1a6s69 (δ, C=O); 2854,
2896, 2948, 2984 (δ, CAlk—H); 3032, 3050 (δ, Carom—H).
(18c,19t,20r,21c)ꢀ19,20ꢀDibenzoylꢀ2,5,8,11ꢀtetraoxatetraꢀ
cyclo[20.4.0.012,17.018,21]hexacosaꢀ1(22),12,14,16,23,25ꢀhexaꢀ
ene (rtccꢀ3c), m.p. 213—215 °C. Calculated (%): C, 76.87;
H, 6.05. C36H34O6. Found (%): C, 76.88; H, 6.07. 1H NMR,
δ: 3.15 (m, 1 H, OCH2); 3.53—3.62 (m, 2 H, ArOCH2);
2
s
s
C(3´)); 122.99 (C(5), C(5´)); 127.12 (C(6), C(6´)); 127.82 (C(4),
C(4´)); 128.33 (C(9), C(9´)); 128.67 (C(10), C(10´)); 133.62
(C(11), C(11´)); 134.12 (C(1), C(1´)); 134.91 (C(8), C(8´));
157.20 (C(2), C(2´)); 198.81 (C(7), C(7´)). MS, m/z
(I/Imax (%)): 474 [M]+ (6), 456 (2), 369 (30), 223 (9), 222 (17),
207 (56), 178 (4), 165 (4), 145 (3), 131 (10), 105 (100), 77 (54),
55 (2). IR, ν/cm–1: 617, 657, 669; 704, 761 (arom.); 854, 904,
956, 937, 988, 1001; 1058, 1089 (ν , Carom—O—CAlk); 1157,
1187 (ν , ν , CAlk—O—CAlk); 1216, 1s245 (ν , Carom—O—CAlk);
3.70—3.97 (m, 9 H, OCH2 and ArOCH2); 4.78 (dd, 1 H, Hβ ,
s
as
1290, 133a0s, 1385, 1446, 1491; 1579, 1593 (δ, C=C); 1671
(δ, C=O); 2865, 2914, 2946 (δ, CAlk—H); 3061 (δ, Carom—H).
(15c,16t,17r,18t)ꢀ16,17ꢀDibenzoylꢀ2,5,8ꢀtrioxatetracycloꢀ
[17.4.0.09,14.015,18]tricosaꢀ1(19),9,11,13,20,22ꢀhexaene
(rtctꢀ2b), m.p. 221—223 °C. Calculated (%): C, 78.76; H, 5.79.
C34H30O5. Found (%): C, 78.79; H, 5.74. 1H NMR, δ:
3.55—3.60, 3.74—3.81 (both m, 2 H each, O—CH2); 3.93—4.05
´
J = 10.5, 10.2 Hz); 4.86 (dd, 1 H, Hα, J = 10.1, 9.1 Hz); 5.29
(dd, 1 H, Hβ, J = 10.2, 10.1 Hz); 5.49 (dd, 1 H, Hα , J = 10.5,
9.1 Hz); 6.33 (dd, 1 H, H(3), J = 8.1, 1.1 Hz); 6.4´0 (td, 1 H,
H(5), J = 7.6, 1.1 Hz); 6.64 (dd, 1 H, H(3´), J = 8.0, 1.0 Hz);
6.75 (ddd, 1 H, H(4), J = 8.1, 7.6, 1.7 Hz); 6.80 (dd, 1 H, H(6),
J = 7.6, 1.7 Hz); 6.84 (ddd, 1 H, H(5´), J = 7.6, 7.5, 1.0 Hz);
7.05 (ddd, 1 H, H(4´), J = 8.0, 7.6, 1.7 Hz); 7.24—7.31 (m, 3 H,
H(10), H(6´)); 7.44 (tt, 1 H, H(11), J = 7.4, 1.2 Hz); 7.55—7.60
(m, 2 H, H(10´)); 7.64—7.69 (m, 3 H, H(11´) and H(9));
(m, 4 H, ArOCH2); 4.65 (m, 2 H, Hα, Hα ); 4.72 (m, 2 H, Hβ,
´
Hβ ); 6.87—6.95 (m, 4 H, H(3), H(3´), H(5), H(5´)); 7.18 (td,
´
8.30—8.33 (m, 2 H, H(9´)). 13C NMR, δ: 37.47 (Cβ ); 38.26
2 H, H(4), H(4´), J = 7.7, 1.5 Hz); 7.33—7.37 (m, 6 H, H(10),
H(10´), H(6), H(6´)); 7.51 (tt, 2 H, H(11), H(11´), J = 7.3,
1.0 Hz); 7.68 (dd, 4 H, H(9), H(9´), J = 8.3, 1.0 Hz). 13C NMR,
δ: 41.83 (Cβ, Cβ ); 46.59 (Cα, Cα ); 69.03 (O—CH ); 70.23
´
(Cβ); 41.83 (Cα ); 49.04 (Cα); 66.03, 66.59, 68.26, 68.91, 69.30,
´
72.20 (5 OCH2); 109.42 (C(3)); 110.35 (C(3´)); 118.42 (C(5));
119.85 (C(5´)); 125.16 (C(1)); 126.84 (C(6´) and C(1´));
126.96 (C(4)); 127.42 (C(4´)); 127.76 (C(10)); 127.98 (C(9));
128.74 and 128.79 (C(10´), C(9´), C(6)); 132.74 (C(11)); 133.53
(C(11´)); 135.03 (C(8)); 135.93 (C(8´)); 155.78 (C(2)); 156.19
(C(2´)); 197.32 (C(7)); 200.01 (C(7´)). IR, ν/cm–1: 478, 504, 637,
659; 691, 712, 752, 791 (arom.); 835, 847, 924, 953; 1064, 1074
(ν , Carom—O—CAlk); 1106, 1117, 1142 (ν , ν , CAlk—O—CAlk);
(ArOCH2); 115.54 (C(3), C(3´)); 121.40 (C(5), C(5´)2); 128.05
(C(9), C(9´)); 128.28 (C(4), C(4´)); 128.39 (C(10), C(10´));
129.34 (C(6), C(6´)); 129.88 (C(1), C(1´)); 133.10 (C(11),
C(11´)); 136.14 (C(8), C(8´)); 158.40 (C(2), C(2´)); 198.86
(C(7), C(7´)). MS, m/z (I/Imax (%)): 518 [M]+ (3), 500 (3), 413
(28), 398 (2), 282 (5), 236 (4), 228 (8), 207 (39), 178 (3), 165
´
´
s
s
as
(5), 145 (2), 131 (12), 105 (100), 77 (37), 55 (2). IR, ν/cm–1
:
1229, 1253 (ν , Carom—O—CAlk); 1304, 1316, 1338, 1407, 1447,
as
660; 696, 761, 779 (arom.); 801, 903, 924, 982, 1019; 1048 (ν ,
1492; 1581, 1597 (δ, C=C); 1662, 1679 (δ, C=O); 2863, 2925
(δ, CAlk—H); 3029, 3058 (δ, Carom—H).
s
Carom—O—CAlk); 1127, 1145, 1182 (ν , ν , CAlk—O—CAlk);
as
1209, 1223, 1244 (ν , Carom—O—CAlk); s1271, 1295, 1318, 1451,
(15t,16c,17r,18t)ꢀ16,17ꢀDibenzoylꢀ2,5,8ꢀtrioxatetracycloꢀ
[17.4.0.09,14.015,18]tricosaꢀ1(19),9,11,13,20,22ꢀhexaene
(rcttꢀ4b), m.p. 180—182 °C. Calculated (%): C, 78.76; H, 5.79.
as
1489; 1580, 1597 (δ, C=C); 1669, 1680 (δ, C=O); 2889, 2919,
2945 (δ, CAlk—H); 3013, 3058 (δ, Carom—H).
34H30O5. Found (%): C, 78.77; H, 5.76. 1H NMR, δ: 3.58 (m,
(15c,16t,17r,18c)ꢀ16,17ꢀDibenzoylꢀ2,5,8ꢀtrioxatetracycloꢀ
[17.4.0.09,14.015,18]tricosaꢀ1(19),9,11,13,20,22ꢀhexane
(rtccꢀ3b), m.p. 219—221 °C. Calculated (%): C, 78.76; H, 5.79.
C
4 H, OCH ); 3.93 (m, 4 H, ArOCH2); 4.63 (m, 2 H, Hβ, Hβ );
´
5.00 (m, 2 2H, Hα, Hα ); 6.74—6.78 (m, 4 H, H(3), H(3´), H(5),
´
C
34H30O5. Found (%): C, 78.74; H, 5.78. 1H NMR, δ:
H(5´)); 7.02 (td, 2 H, H(4), H(4´), J = 8.0, 1.6 Hz); 7.38—7.43
(m, 6 H, H(10), H(10´), H(6), H(6´)); 7.52 (tt, 2 H, H(11),
H(11´), J = 7.4, 1.3 Hz); 7.81 (dd, 4 H, H(9), H(9´), J = 8.3,
1.3 Hz). 13C NMR, δ: 37.74 (Cβ, Cβ ); 47.24 (Cα, Cα ); 65.31
3.40—3.52 (m, 2 H, OCH2); 3.60 (dt, 1 H, OCH2, J = 11.3,
2.4 Hz); 3.75 (m, 1 H, ArOCH2); 3.84—3.92 (m, 2 H, ArOCH2
and OCH2); 4.04—4.13 (m, 2 H, ArOCH2); 4.74—4.86 (m, 2 H,
´
´
Hβ , Hα); 5.35 (dd, 1 H, Hβ, J = 10.3, 9.6 Hz); 5.52 (dd, Hα
,
(ArOCH2); 66.21 (OCH2); 111.60 (C(3), C(3´)); 119.71 (C(5),
C(5´)); 127.16 (C(4), C(4´)); 127.80 (C(9), C(9´)); 128.08
(C(6), C(6´)); 128.12 (C(1), C(1´)); 128.59 (C(10), C(10´));
132.92 (C(11), C(11´)); 135.53 (C(8), C(8´)); 155.40 (C(2),
C(2´)); 198.53 (C(7), C(7´)). IR, ν/cm–1: 479, 562, 603; 691,
´
´
J = 10.3, 10.2 Hz); 6.42 (ddd, 1 H, H(5), J = 7.7, 7.3, 1.1 Hz);
6.60 (dd, 1 H, H(3), J = 8.3, 1.1 Hz); 6.66 (dd, 1 H, H(3´),
J = 7.9, 0.9 Hz); 6.75 (ddd, 1 H, H(4), J = 8.3, 7.3, 1.6 Hz); 6.80
(ddd, 1 H, H(5´), J = 7.6, 7.4, 0.9 Hz); 6.85 (dd, 1 H, H(6),
J = 7.7, 1.6 Hz); 7.02 (ddd, 1 H, H(4´), J = 7.9, 7.6, 1.6 Hz);
714, 752, 775, 789 (arom.); 853, 914, 942, 1001; 1055, 1087 (ν ,
s

1190
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
Ovchinnikova et al.
Carom—O—CAlk); 1116, 1144, 1164, 1185 (ν , ν , CAlk—O—CAlk);
grams.28 Some hydrogen atoms were revealed in the difference
synthesis and included into the refinement in the isotropic
approximation, and some hydrogen atoms were placed in geoꢀ
metrically calculated positions and refined using the riding model.
Compound rtctꢀ2a (solvate): C32H26O4•C3H7ON, M = 547.62,
the crystals are triclinic, space group Р1, а = 9.5686(4) Å,
b = 11.2901(4) Å, c = 14.2661(5) Å, α = 82.179(3)°, β = 84.403(4)°,
s
as
1224, 1243 (ν , Carom—O—CAlk); 1300, 1322, 1338, 1353, 1447,
as
1489; 1580, 1598 (δ, C=C); 1672, 1683 (δ, C=O); 2859, 2932,
2962 (δ, CAlk—H); 3037, 3063 (δ, Carom—H).
(18t,19c,20r,21t)ꢀ19,20ꢀDibenzoylꢀ2,5,8,11ꢀtetraoxatetraꢀ
cyclo[20.4.0.012,17.018,21]hexacosaꢀ1(22),12,14,16,23,25ꢀhexaene
(rcttꢀ4c), m.p. 218—220 °C. Calculated (%): C, 76.87; H, 6.05.
C36H34O6. Found (%): C, 76.9; H, 6.12. 1H NMR, δ:
3.19—3.27 (m, 2 H, O—CH2); 3.46 (m, 4 H, O—CH2);
3.66—3.75 (m, 4 H, O—CH2); 3.77—3.83 (m, 2 H, O—CH2);
γ = 73.307(4)°, V = 1459.72(9) Å3; Z = 2, μ = 0.083 cm–1
;
13 505 measured reflections (2.70 < θ < 31.61°), of them 7966
were independent reflections (Rint = 0.0140), number of reflecꢀ
tions with I > 2σ(I) 4768, ρ = 1.246 g cm–3, R factors: R1 = 0.0782,
wR2 = 0.1370 (for all reflections), R1 = 0.0461, wR2 = 0.1267
(I > 2σ(I)).
4.60 (m, 2 H, Hβ, Hβ ); 4.93 (m, 2 H, Hα, Hα ); 6.71—6.79 (m,
´
4 H, H(3), H(3´), H(5), H(5´)); 7.06 (td, 2´ H, H(4), H(4´),
J = 7.7, 1.7 Hz); 7.33 (dd, 2 H, H(6), H(6´), J = 7.6, 1.7 Hz);
7.42 (dd, 4 H, H(10), H(10´), J = 8.0, 7.5 Hz); 7.54 (tt, 2 H,
H(11), H(11´), J = 7.5, 1.2 Hz); 7.81 (dd, 4 H, H(9), H(9´),
J = 8.0, 1.2 Hz). 13C NMR, δ: 34.75 (Cβ, Cβ ); 48.83 (Cα, Cα );
Compound rtccꢀ3b: C34H30O5, M = 518.58, the crystals
are monoclinic, space group Р2(1)/C, а = 19.361(4) Å,
b = 13.2285(18) Å, c = 10.433(2) Å, β = 91.980(17)°, V =
= 2670.5(9) Å3; Z = 4, μ = 0.086 cm–1; 17 028 measured
reflections (2.61 < θ < 26.38°), of them 5332 were independent
reflections (Rint = 0.0542), number of reflections with I > 2σ(I)
2052, ρ = 1.290 g cm–3, R factors: R1 = 0.1535, wR2 = 0.0538
(for all reflections), R1 = 0.0413, wR2 = 0.0481 (I > 2σ(I)).
Compound rtccꢀ3c: C36H34O6, M = 562.63, the crystals
are monoclinic, space group Р2(1)/C, а = 11.5545(6) Å,
b = 22.9959(12) Å, c = 11.1039(7) Å, β = 90.019(5)°, V =
= 2950.4(3) Å3; Z = 4, μ = 0.085 cm–1; 25 755 measured
reflections (2.70 < θ < 26.39°), of them 5984 were independent
reflections (Rint = 0.0645), number of reflections with I > 2σ(I)
2341, ρ = 1.267 g cm–3, R factors: R1 = 0.1392, wR2 = 0.0457
(for all reflections), R1 = 0.0429, wR2 = 0.0422 (I > 2σ(I)).
Compound rcttꢀ4b: C34H30O5, M = 518.58, the crystals
are orthorhombic, space group Рbca, а = 11.9378(11) Å, b =
= 19.208(2) Å, c = 23.338(2) Å, β = 90°, V = 5351.4(9) Å3; Z = 8,
μ = 0.086 cm–1; 24 767 measured reflections (2.66 < θ < 26.39°),
of them 5399 were independent reflections (Rint = 0.0840),
´
´
66.79 (ArOCH2); 68.41 (OCH2); 70.64 (O—CH2); 110.38 (C(3),
C(3´)); 119.64 (C(5), C(5´)); 127.24 (C(4), C(4´)); 127.78 (C(6),
C(6´)); 128.0 (C(9), C(9´)); 128.28 (C(1), C(1´)); 128.46 (C(10),
C(10´)); 132.84 (C(11), C(11´)); 135.53 (C(8), C(8´)); 155.93
(C(2), C(2´)); 198.41 (C(7), C(7´)). MS, m/z (I/Imax (%)):
562 [M]+ (2), 457 (19), 223 (4), 207 (31), 178 (2), 165 (5), 145 (2),
131 (7), 105 (100), 77 (32), 55 (2). IR, ν/cm–1: 559, 609, 639;
693, 711, 748, 773, 788 (arom.); 853, 918, 951, 1003; 1060 (ν ,
s
C
arom—O—CAlk); 1115, 1136, 1160 (ν , ν , CAlk—O—CAlk);
as
1225, 1252 (ν , Carom—O—CAlk); 1290, s1319, 1365, 1448, 1492;
1581, 1598 (aδs, C=C); 1669, 1681 (δ, C=O); 2865, 2913 (δ,
C
Alk—H); 3035, 3065 (δ, Carom—H).
(1t,24c,25r,26t)ꢀ25,26ꢀDibenzoylꢀ8,11,14,17ꢀtetraoxatetraꢀ
cyclo[22.1.1.02,7.018,23]hexacosaꢀ2,4,6,18,20,22ꢀhexaene
(rtccꢀ5c), m.p. 219—221 °C. Calculated (%): C, 76.87; H, 6.05.
C36H34O6. Found (%): C, 76.84; H, 6.09. 1H NMR, δ: 3.54
(m, 1 H, OCH2); 3.75—3.89 (m, 8 H, OCH2); 4.03, 4.11, 4.34
(all m, 1 H each, OCH2); 4.70 (ddd, 1 H, CH, J = 12.0, 8.2, 0.8
Hz); 4.85 (ddd, 1 H, CH, J = 12.0, 6.8, 0.8 Hz); 5.09 (ddd, 1 H,
CH, J = 11.8, 6.8, 0.8 Hz); 5.66 (ddd, 1 H, CH, J = 11.8, 8.2,
0.8 Hz); 6.52—6.58 (m, 2 H, Ar); 6.63 (dd, 1 H, Ar, J = 8.1,
1.0 Hz); 6.79 (td, 1 H, Ar, J = 7.5, 1.1 Hz); 6.88—6.98 (m, 2 H,
Ar); 7.04 (dd, 1 H, Ar, J = 7.5, 1.7 Hz); 7.19—7.24 (m, 2 H, Ar);
7.26—7.36 (m, 4 H, Ar); 7.42 (tt, 1 H, Ar, J = 7.3, 1.4 Hz);
7.64—7.70 (m, 4 H, Ar). IR, ν/cm–1: 478, 498, 597, 612; 687,
697, 730, 756, 772 (arom.); 806, 850, 911, 926, 938; 1060
(ν , Carom—O—CAlk); 1116, 1138 (ν , ν , CAlk—O—CAlk); 1235,
number of reflections with I > 2σ(I) 2051, ρ = 1.287 g cm–3
,
R factors: R1 = 0.1545, wR2 = 0.0649 (for all reflections),
R1 = 0.0441, wR2 = 0.0591 (I > 2σ(I)).
Compound rcttꢀ4c: C36H34O6, M = 562.63, the crystals
are orthorhombic, space group Рccn, а = 14.4068(9) Å, b =
= 34.171(4) Å, c = 11.8808(14) Å, β = 90°, V = 5848.9(11) Å3;
Z = 8, μ = 0.086 cm–1; 21 394 measured reflections (2.83 < θ <
<
26.38°), of them 5847 were independent reflections
(Rint = 0.0973), number of reflections with I > 2σ(I) 2112,
ρ = 1.278 g cm–3, R factors: R1 = 0.1781, wR2 = 0.0916 (for
all reflections), R1 = 0.0570, wR2 = 0.0812 (I > 2σ(I)).
s
s
as
1251 (ν , Carom—O—CAlk); 1278, 1296, 1320, 1367, 1448, 1493;
as
1584, 1598 (δ, C=C); 1668 (δ, C=O); 2874, 2923, 2964 (δ,
C
Alk—H); 3038, 3061 (δ, Carom—H).
Compound rcttꢀ5c (solvate): C36H34O6•C6H6•H2O,
Xꢀray diffraction study. Crystals of cyclobutaneꢀcontaining
M = 658.76, the crystals are triclinic, space group Р1,
а = 9.0980(14) Å, b = 13.682(3) Å, c = 14.6328(13) Å, α =
= 84.709(14)°, β = 89.163(9)°, γ = 71.474(14)°, V = 1719.5(4) Å3;
Z = 2, μ = 0.086 cm–1; 17 477 measured reflections (2.71 < θ <
crown ethers 2a,b were prepared by the slow concentration of
solutions in DMF, compounds 3b,c were obtained in acetonitrile,
compounds 4b,c were obtained from nꢀbutanol, and crystals
of compound 5c were prepared from benzene. Single crystals of
compounds 2a, 3b,c, 4b,c, and 5c are racemates, whereas single
crystals of earlier27 described compound 2b represent a congloꢀ
merate and are formed by molecules of the R,R,S,Sꢀ or S,S,R,Rꢀ
enantiomer. Xꢀray diffraction analysis of the compounds was
carried out on an Xcalibur 3 automated diffractometer with the
CCD detector (MOKα radiation, λ = 0.71073 Å, graphite
monochromator, T = 295 K). The structures were solved by a
direct method and refined by least squares first in the isotropic
and then in the anisotropic approximation by F2 for all nonꢀ
hydrogen atoms using the SHELXSꢀ97 and SHELXLꢀ97 proꢀ
< 28.28°), of them 8111 were independent reflections (Rint
=
,
= 0.0258), number of reflections I > 2σ(I) 3811, ρ = 1.272 g cm–3
R factors: R1 = 0.1060, wR2 = 0.0857 (for all reflections),
R1 = 0.0410, wR2 = 0.0784 (I > 2σ(I)).
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 07ꢀ03ꢀ96111
and 07ꢀ03ꢀ96113) and the Presidium of the Russian
Academy of Sciences (Project “Design of New Supramoꢀ
lecular Structures Containing Heterocyclic Fragments”).

Photochemistry of chalconeꢀpodands
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
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Received March 25, 2009