Synthesis and properties of photosensitive compounds based on bromine-containing 3-acyl-2-furylchromones

Article abstract of DOI:10.1007/s10593-011-0736-x

Methods have been developed for the synthesis of new photosensitive compounds based on the reaction of N,S,O-nucleophiles with 3-acyl-2-(5-bromofur- 2-yl)chromones and 3-acyl-2-(5-bromomethylfur-2-yl)chromones. The relationship between the spectral proper

Full text of DOI:10.1007/s10593-011-0736-x

Chemistry of Heterocyclic Compounds, Vol. 47, No. 2, May, 2011 (Russian Original Vol. 47, No. 2, February, 2011)
SYNTHESIS AND PROPERTIES OF PHOTOSENSITIVE
COMPOUNDS BASED ON BROMINE-CONTAINING
3-ACYL-2-FURYLCHROMONES*
K. S. Levchenko1, V. A. Barachevski2, V. N. Yarovenko3,
M. M. Krayushkin3**, I. S. Semenova3, O. I. Kobeleva2,
T. M. Valova2, and P. S. Shmelin1
Methods have been developed for the synthesis of new photosensitive compounds based on the reaction
of N,S,O-nucleophiles with 3-acyl-2-(5-bromofur-2-yl)chromones and 3-acyl-2-(5-bromomethylfur-
2-yl)chromones. The relationship between the spectral properties and the structure of compounds has
been shown.
Keywords: chromones, nucleophilic substitution, optical disks, absorption spectra, fluorescence spectra.
We showed previously that derivatives of 3-acetyl-2-furylchromones are promising components of
recording media for providing a single two-photon record on multilayer optical disks of ultra-high information
capacity [1, 2]. It is known that 3-acetyl-2-furylchromones in the initial form A do not possess fluorescence, but
on irradiation with UV light undergo irreversible photochemical conversion with the formation of the
fluorescing form B [1-4], which provides multiple fluorescent reading of optical information.
In the present work we have continued the study of the effect of structural factors on the photochemical
properties of 3-acyl-2-furylchromones. In the previous investigation it was shown that the spectral
characteristics of chromones depend to a significant extent on the substituents in the furan ring. The introduction
of halogen atoms or a nitro group leads to a strong bathochromic shift of the absorption band of the initial form
A, and also a shift of the absorption and fluorescence band of the photoproduct B [2]. It seemed expedient to
study the effect of donor groups on the photochemical and fluorescent properties of chromones.
_______
* Dedicated to our dear colleague L. I. Belen'kii on the occasion of his famous jubilee.
** To whom correspondence should be addressed, e-mail: mkray@mail.ioc.ac.ru.
1Central Science Research Institute of Technology "Tekhnomash", 4 Ivana Franko St., Moscow 121108, Russia;
e-mail: ntc_technology@socket.ru.
2Photochemistry Center, Russian Academy of Sciences, 7a, bdg 1, Novatorov St., Moscow 119421, Russia;
e-mail: barva@photonics.ru.
3N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Pr., Moscow
119991, Russia.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 198-210, February, 2011. Original
article submitted January 21, 2011.
0009-3122/11/4702-0155©2011 Springer Science+Business Media, Inc.
155

O
R
O
O
R
O
R
hv
O
O
O
O
..
R1
O
O
A
B
R1
O
R1
O
Proceeding from the fact that the benzopyranone fragment possesses electron-withdrawing properties it
might be proposed that under its influence atoms of halogen in the furan ring must possess enhanced reactivity
under conditions of a nucleophilic substitution reaction, which also permits the introduction of various donor
groups into the chromone system.
3-Acyl-2-furylchromones 1 containing a bromine atom at position 5 of the furan ring were synthesized
from 2-hydroxyacetophenone under the conditions proposed by us in the previous work [2], according to the
following scheme.
O
O
O
O
ArCOCl
t-BuOK
Ar
Me
Me
Py,
0–20°C
DMF,
0–15°C
O
O
OH
OH
Ar
O
O
O
O
O
O
O
O
O
R
Ar
O
SeO2
1,4-dioxane
Ar
O
Ar
O
Py,
EtOH, ~20°C
O
OH
R
R
R
1a–e
1 a Ar = Ph, R = Me; b Ar = Ph, R = Br; c Ar = thien-2-yl, R = Br; d Ar = Ph, R = H; e Ar = thien-2-yl, R = H
It turned out that on boiling in ethyl alcohol or on heating in DMF in the presence of K2CO3, or without
it in several cases, a nucleophilic substitution reaction takes place smoothly. Compounds 2-4 obtained in these
reactions are given in Table 1.
TABLE 1. Products of Nucleophilic Substitution of 3-Acyl-2-(5-bromofur-2-
yl)chromones
Com-
Yield,
%
Nucleophile
Solvent
Base
Conditions
R
pounds
PhSNa
EtOH
EtOH
EtOH
EtOH
EtOH
DMF
DMF
EtOH
EtOH
—
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Boiling
Boiling
Boiling
Boiling
Boiling
50°C
Ph
66
59
29
30
35
45
35
79
72
2a
2b
2с
2d
2e
3a
3b
4a
4b
t-BuSH
t-Bu
t-Bu
t-BuSH
HSCH2CO2Et
HS(CH2)2N(Et)2
PhOH
CH2CO2Et
(CH2)2NEt2
Ph
4-t-BuC6H4OH
Morpholine
Piperidine
50°C
4-t-BuС6H4
—
Morpholine Boiling
Piperidine Boiling
—
156

O
Ar
R1SR
O
O
R1 = Na or H
O
SR
2a–e
O
Ar
ROH
O
O
1b,c
O
OR
3a,b
O
Ar
HN
X
O
O
O
X
N
4a,b
2a,b,d,e, 3a,b, 4a,b Ar = Ph; 2c Ar = thien-2-yl; 4 a X = O, b X = CH2
Typical photoinduced changes of absorption and fluorescence spectra for compounds of the type of 2-4
are given in Figs. 1-3 respectively.
It is seen in Fig. 1 that on sequential irradiation of a solution of chromone 2e the intensity of the long-
wave absorption band of the initial form A at 354 nm is reduced with the simultaneous appearance and increase
of intensity of a long wave absorption band at 420 nm, explained by the formation of photoproduct B. The
appearance of the absorption band of the photoproduct is accompanied by the appearance of photoinduced
fluorescence with a maximum at 495 nm. On increasing the exposure to UV light its intensity grows.
Fig. 1. Absorption (1-5) and fluorescence (6-9) spectra of a solution of compound 2e in
toluene before (1) and after (2-9) irradiation with UV light through a UFS-1 filter.
Fluorescence spectra were measured on excitation with light of λ 425 nm (absorption
band maximum of the photoproduct).
157

Fig. 2. Absorption (1-5) and fluorescence (6-9) spectra of a solution of compound 3a in
toluene before (1) and after (2-9) irradiation with UV light through a UFS-1 filter. The
fluorescence spectra were measured on excitation with light of λ 415 nm (maximum of
the absorption band of the photoproduct).
Analogous photoinduced spectral changes were observed for compound 3a (Fig. 2).
Fig. 3. Absorption (1, 2) and fluorescence (3) spectra of a solution of compound 4b in
toluene before (1) and after irradiation (2, 3). The fluorescence spectra were measured
on excitation with light of λ 420 nm.
Photoinduced spectral changes, different from those described above, were displayed by chromones of
group 4 (Fig. 3). It is seen from the figure that the absorption bands of the initial form of chromone A and its
photoproduct overlap considerably.
As is shown by the data of Table 2 the photochemical and fluorescence properties of the obtained
chromones 2-4 differ strongly from the properties of the unsubstituted chromone 1d. The absorption bands of
the chromones in the initial state A were displaced bathochromically by 12-105 nm, the absorption and
fluorescence bands of the photoinduced form B had a low displacement (Table 2).
158

TABLE 2. Spectrokinetic Characteristics* of the Photoconversions of
Chromones
Com-
pound
λВ fl max, nm
IВ fl, rel. units

А max, nm (DА)

В max, nm (DВ)
Δλ = λВ fl max–В max, nm
1d
2a
2d
2e
3a
3b
4a
4b
315 (0.9)
327 (1.0)
338 (0.8)
354 (0.7)
340 (1.0)
345 (0.8)
406 (1.2)
420 (1.2)
415 (0.15)
420 (0.39)
420 (0.19)
420 (0.40)
415 (0.60)
415 (0.45)
418 (0.36)
423 (0.33)
495
490
488
495
490
490
491
491
80
70
68
75
75
75
73
68
260
1000
250
770
1700
1650
1840
2350
_______
* λA max and λB max are wavelengths of absorption band maxima of initial and
photoinduced forms of chromones respectively; λB fl max is the wavelength of the
band maximum of fluorescence of photoinduced form of chromone; DA is the
photoinduced optical density at the absorption band maximum of the
photoproduct; IB fl is the intensity of the fluorescence in the state of photo-
equilibrium.
O
Ph
RSR1
R
O
O
S
R1 = Na
or H
O
6a–e
O
Ph
O
Ph
PBO,
NBS
R
ROH
O
O
O
O
1a
O
O
O
Br
7
5
O
Ph
R1
R1R2NH
O
R
N
O
O
8a,b
a R1R2NH = morpholine, b R1R2NH = 2-methylaniline
From chromone derivatives containing a bromomethyl group, we synthesized analogs of chromones 2-4
differing only in the methylene fragment between the furan ring and the amino, thio, or oxy group (compounds
6-8). The given compounds were synthesized according to the scheme given above.
In the first stage 3-benzoyl-2-(5-bromomethylfur-2-yl)chromone 5 was formed from methyl derivative
1a by boiling with NBS and catalytic amounts of dibenzoyl peroxide (PBO) in CCl4. On interaction of
compound 5 with nucleophiles in DMF substitution of the bromine atom occurs with the formation of thio, oxo,
or amino derivatives of chromones 6, 7, 8 (Table 3).
159

TABLE 3. Products of Nucleophilic Substitution of 3-Acyl-2-(5-
bromomethylfur-2-yl)chromone 5*
Com-
pound
Nucleophile
Base
—
Conditions
R
R1
Yield, %
PhSNa
~20°C
50°C
Ph
—
—
—
—
—
—
75
80
47
64
80
20
60
70
6a
6b
6c
6d
6e
7
t-BuSH
K2CO3
t-Bu
Bu
BuSH
K2CO3
K2CO3
—
50°C
HSCH2CO2Et
KSCN
50°C
CH2CO2Et
CN
Boiling
50°C
PhOH
K2CO3
Morhholine
K2CO3
Ph
Morpholine
2-Methylaniline
~20°C
~20°C
(CH2)2O(CH2)2
2-MeC6H4
8a
8b
H
_______
*Solvents: DMF (compounds 6a-d, 7, 8a,b) and EtOH (compound 6e).
Data of photochemical investigations of the obtained compounds are given in Table 4.
The photoinduced spectral changes of compounds 6-8 were similar to those displayed for compounds 2
and 3. Comparison of the spectral characteristics of compounds 2-4 and 6-8 showed that introduction of a
nucleophile directly into the furan ring leads to a more substantial change in the position of the absorption band
of the initial form A of compounds while retaining the position of absorption and fluorescence bands of the
photoinduced form B. Amines showed the strongest influence. The introduction of morpholine and piperidine
rings leads to the strongest displacement in comparison with the unsubstituted chromone 1d from 315 to 406 and
420 nm, respectively (compounds 4a,b), while amines removed by one methylene link gave only a small (5-10
nm) bathochromic shift (compounds 8a,b). A similar parallel was also observed for the oxo and thio derivatives,
however, the bathochromic displacement of absorption band maxima was significantly less (15-30 nm). It must
be emphasized that, as shown by the comparative investigation of the fluorescent properties, the introduction of
a nucleophile directly into the furan nucleus leads to a substantial improvement of the fluorescent properties of
the photoproduct. In reality, for the series of compounds 6-8 the fluorescence intensity of the photoinduced form
does not exceed 100 rel. units on average, while for compounds 2-4 this parameter is from 200 to 2350 rel. units.
The conjugation of electron-donor groups with the furan ring therefore makes it more inclined to
photoinduced conversion, since all compounds of this type possess high photosensitivity, which is displayed in
high values of photoinduced optical density and of fluorescence intensity. Distancing the heteroatoms from the
furan nucleus by a methylene fragment leads to a reduction in the fluorescence intensity of the photoinduced
form.
TABLE 4. Spectrokinetic Characteristics of Photoconversions of Chromones
Com-
pound

А max, nm
(DА)

В max, nm
(DВ)
λ
В fl max, nm
Δλ = λВ fl max–В max, nm IВ fl, rel. units
330 (1.4)
330 (1.2)
331 (1.0)
329 (1.2)
319 (1.3)
318 (0.9)
320 (1.1)
327 (1.2)
420 (0.15)
420 (0.12)
417 (0.13)
417 (0.14)
420 (0.23)
420 (0.20)
415 (0.14)
400 sh (0.50)
490
495
490
490
493
495
490
490
70
75
73
73
73
75
75
90
57
60
63
61
63
40
118
57
6a
6b
6c
6d
6e
7
8a
8b
160

EXPERIMENTAL
The 1H NMR spectra were recorded on Bruker AC 200 (200 MHz) and AM 300 (300 MHz) instruments
in CDCl3. 13C NMR spectra were recorded on a Bruker AM300 (75 MHz) instrument in CDCl3, internal
standard was by the residual protons of the carbon atom of the solvent. Mass spectra were recorded on a Varian
MAT CH-6 instrument by direct insertion of the sample into the radiation source, ionization energy was 70 eV
and operating voltage 1.75 kV. Melting points were measured on a Boetius hot stage and are not corrected. The
analysis of all reaction mixtures and checks on the purity of isolated compounds was by TLC on Merck Silica
gel 60 F254 UV-254 plates.
Absorption–kinetic measurements (absorption spectra of initial compounds and photoproducts, kinetics
of photocoloration processes, kinetics of photoinduced optical density) were recorded on a Varian Cary 50
spectrophotometer. Toluene (Aldrich) was used as solvent. Solution concentration = 2·10-4 M. A quartz cuvette
of thickness 0.2 cm was used for measurements. Irradiation was effected by light from a LC-4 Hamamatsu lamp
through a UV light filter. The efficiency of photocoloring of compounds was assessed according to the
maximum value of the photoinduced optical density at the maximum of the absorption band of the photoproduct.
It was determined from the kinetic curve of the dependence of optical density on time of irradiation after
establishment of the photostationary state.
Fluorescence spectra were obtained on a Varian Cary Eclipse spectrophotometer. The working concentration
of compounds in toluene c = 4·10-5 M. A quartz cuvette of thickness 1 cm was used for measurements. Fluorescence
spectra were measured after reaching maximum change of the photoinduced optical density at the maximum of the
absorption band of the photoproduct on excitation by light of the same wavelength.
Compounds 1 were synthesized by the procedure developed previously in [2].
3-Benzoyl-2-(5-bromofur-2-yl)-4H-chromen-4-one (1b). Yield 1.09 g (70%); mp 209-210oC
(ethanol). 1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.23 (1H, d, J = 7.7, H-5); 7.99 (2H, d, J = 7.7, H'-2);
7.75 (1H, t, J = 7.8, H-7); 7.55-7.60 (2H, m, H Ar); 7.43-7.48 (3H, m, H Ar); 7.02 (1H, d, J = 3.7, H-3 furan);
6.42 (1H, d, J = 3.7, H-4 furan). Mass spectrum, m/z (Irel, %): 396 [M]+ (5), 394 (9), 316 (95), 315 [M-Br]+
(100). Found, %: C 60.69; H 2.73; Br 20.12. C20H11BrO4. Calculated, %: C 60.78; H 2.81; Br 20.22.
2-(5-Bromofur-2-yl)-3-(thiophen-2-carbonyl)-4H-chromen-4-one (1c). Yield 0.95 g (69%); mp 178oC
(ethanol). 1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.25 (1H, d, J = 7.9, H-5); 7.70-7.80 (2H, m, H Ar); 7.40-
7.65 (3H, m, H Ar); 7.05-7.10 (2H, m, H Ar); 6.48 (1H, d, J = 3.6, H-4 furan). Mass spectrum, m/z (Irel, %): 402
[M]+ (8), 400 (8), 322 (90), 321 [M-Br]+ (100). Found, %: C 53.80; H 2.21. C18H9BrO4S. Calculated, %: C 53.88; H
2.26.
3-Benzoyl-2-[5-(phenylthio)fur-2-yl]-4H-chromen-4-one (2a). A mixture of compound 1b (0.395 g,
1 mmol) and sodium phenothiolate (0.139 g, 1.05 mmol) was boiled in ethanol. After the end of the reaction
(check by TLC) the solvent was evaporated in vacuum, the residue dissolved in methylene chloride, and the
solution was filtered through a layer of silica gel. After evaporation in vacuum the residue was recrystallized
1
from ethanol. Yield 0.28 g (66%); mp 178-180oC. H NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.22 (1H, d,
J = 8.1, H-5); 7.92 (2H, d, J = 7.7, H'-2); 7.74 (1H, t, J = 7.9, H-7); 7.36-7.56 (5H, m, H Ar); 7.02-7.21 (6H, m,
H Ar); 6.65 (1H, d, J = 3.7, H-4 furan). 13C NMR spectrum (75 MHz), δ, ppm: 193.61; 176.18, 155.78, 141.71,
136.60, 136.11, 135.87, 134.45, 134.23, 133.93, 131.92, 129.74, 129.62, 129.52, 129.44, 129.17, 129.02,
127.68, 126.10, 125.74, 123.29, 117.97. Mass spectrum, m/z (Irel, %): 317 [M-SPh]+ (9), 316 (36), 315 (100),
314 (5), 287 (5), 277 (2), 267 (3), 259 (4), 231 (9), 202 (9), 182 (18), 110 (57). Found, %: C 73.50; H 3.69;
C26H16O4S. Calculated, %: C 73.57; H 3.80.
Reaction of Bromo Derivatives of Furylchromones with Alkanethiols (General Method). A mixture
of compound 1b or 1c (1 mmol) with t-BuSH or thioglycolic acid ethyl ester (1.05 mmol) was boiled in ethanol
in the presence of K2CO3. After completion of the reaction (check by TLC) the solvent was removed in
vacuum. The residue was dissolved in methylene chloride and the solution was processed by filtering
through silica gel. After evaporating in vacuum the residue was recrystallized from ethanol.
161

3-Benzoyl-2-[5-(tert-butylthio)fur-2-yl]-4H-chromen-4-one (2b). Yield 0.24 g; (59%); mp 105-106oC.
1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.21 (1H, J = 6.9, H-5); 8.02 (2H, d, J = 6.7, H'-2); 7.76 (1H, t,
J = 7.6, H-7); 7.34-7.65 (5H, m, H Ar); 7.17 (1H, d, J = 3.4, H-3 furan); 6.65 (1H, d, J = 3.5, H-4 furan); 1.13
(9H, s, C(CH3)3) 13C NMR spectrum (75 MHz), δ, ppm: 192.20; 176.27; 155.63; 151.89; 150.70; 148.05;
137.18; 134.41; 133.72; 129.57; 128.73; 126.11; 125.62; 123.60; 121.91; 119.55; 117.98; 116.82; 48.88, 30.93.
Mass spectrum (EI), m/z (Irel, %): 404 [M]+ (5), 374 (1), 350 (18), 349 (13), 348 (80), 330 (5), 319 (4), 317 (7),
316 (65), 315 [M-S(t-Bu)]+ (100), 306 (3), 294 (2), 288 (10), 287 (7), 275 (6), 271 (13), 270 (26). Found, %:
C 71.35; H 5.06. C24H20O4S. Calculated, %: C 71.27; H 4.98.
2-[5-(tert-Butylthio)fur-2-yl]-3-(thiophen-2-ylcarbonyl)-4H-chromen-4-one (2c). Yield 0.119 g
(29%); mp 133-135oC. 1H NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.23 (1H, d, J = 8.1, H-5); 7.78-7.62 (5H,
m, H Ar); 7.19 (1H, d, J = 3.3, H thiophene); 7.07 (1H, J = 4.4, H thiophene); 6.67 (1H, d, J = 3.7, H-4 furan);
1.22 (9H, s, C(CH3)3). Mass spectrum, m/z (Irel, %): 411 [M]+ (2), 410 (8), 355 (2), 354 (8), 353 (8), 341 (2),
323 (6), 322 (31), 321 (84) [M-S(t-Bu)]+ (84), 301 (2), 293 (2), 278 (2), 272 (13), 271 (17), 270 (100). Found,
%: C 64.43; H 4.47. C22H18O4S2. Calculated, %: C 64.37; H 4.42.
Ethyl Ester of 2-[5-(3-Benzoyl-4-oxo-4H-chromen-2-yl)fur-2-ylthio]acetic Acid (2d). Yield 0.130 g
1
(30%); mp 138-139oC. H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.22 (1H, d, J = 6.6, H-5); 8.04 (2H, d,
J = 7.1, H'-2); 7.76 (1H, t, J = 7.1, H-7); 7.63-7.42 (5H, m, H Ar); 7.14 (1H, d, J = 3.5, H-3 furan; 6.56 (1H, d,
J = 3.4, H-4 furan); 4.12 (2H, q, J = 7.1, CH2CH3); 3.17 (2H, s, CH2COOEt); 1.23 (3H, t, J = 7.2, CH3). Found,
%: C 66.29; H 4.14. C24H18O6S. Calculated, %: C 66.35; H 4.18.
3-Benzoyl-2-{5-[2-(diethylamino)ethylthio]fur-2-yl}-4H-chromen-4-one (2e). Yield 0.156 g (35%);
mp 111-113oC. 1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.22 (1H, dd, J = 7.9, J = 1.6, H-5); 8.03 (2H, d
d, J = 7.1, J = 1.6, H'-2); 7.75 (1H, dt, J = 7.3, J = 1.7, H-7); 7.37-7.62 (5H, m, H Ar); 7.14 (1H, d, J = 3.5, H-3
furan); 6.45 (1H, d, J = 3.6, H-4 furan); 2.62-2.69 (2H, m, SCH2); 2.41-2.53 (6H, m, CH2N(CH2Me)2); 0.93 (6H,
t, J = 7.1 N(CH2CH3)2). 13C NMR spectrum (75 MHz), δ, ppm: 192.59; 176.17; 155.60; 153.76; 150.84; 146.43;
137.17; 134.34; 133.74; 129.41; 128.81; 126.09; 125.57; 123.59; 117.91; 117.45; 115.21; 51.91; 46.90, 32.55;
11.88. Found, %: C 69.74; H 5.62. C26H25NO4S. Calculated, %: C 69.78; H 5.63.
Reaction of Bromo Derivatives of Furylchromones with Phenols (General Method). A mixture of
compound 1b (1 mmol), phenol or 4-tert-butylphenol (2.1 mmol) was heated (~70oC) in DMF solution in the
presence of K2CO3. After completion of the reaction (check by TLC) the mixture was poured into water,
extracted with methylene chloride, the extract was washed with a small amount of ice water, and filtered through
silica gel. After evaporation in vacuum the residue was recrystallized from ethanol.
1
3-Benzoyl-2-(5-phenoxyfur-2-yl)-4H-chromen-4-one (3a). Yield 0.184 g (45%); mp 146-147oC. H
NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.20 (1H, d, J = 7.8, H-5); 7.87 (2H, d, J = 7.8, H'-2); 7.73 (1H, t,
J = 7.8, H-7); 7.27-7.58 (7H, m, H Ar); 7.11-7.18 (2H, m, H Ar + H-3 furan); 6.92 (2H, d, J = 8.0, H" Ar); 5.60
(1H, d, J = 3.4, H-3 furan). 13C NMR spectrum (75 MHz), δ, ppm: 192.75, 176.00, 160.49, 155.60, 155.09,
151.04, 137.10, 136.79, 134.18, 133.54, 129.92, 129.35, 128.79, 128.66, 126.09, 125.46, 125.14, 123.57,
118.63, 118.11, 117.99, 117.84. Mass spectrum, m/z (Irel, %): 408 [M]+ (6), 363 (2), 317 (2), 316 (14), 315
[M-OPh]+ (100), 288 (3), 275 (2). Found, %: C 76.40; H 3.89. C26H16O5. Calculated, %: C 76.46; H 3.95.
3-Benzoyl-2-[5-(4-tert-butylphenoxy)fur-2-yl]-4H-chromen-4-one (3b). Yield 0.162 g (35%);
1
mp 168-169oC. H NMR spectrum (200 MHz), δ, ppm (J, Hz); 8.21 (1H, d, J = 7.9, H-5); 7.90 (2H, d, J = 7.6,
H'-2); 7.73 (1H, t, J = 7.5, H-7); 7.30-7.56 (7H, m, H Ar); 7.11 (1H, d, J = 3.4, H-3 furan); 6.86 (2H, d, J = 8.5,
H" Ar); 5.55 (1H, d, J = 3.4, H-4 furan); 1.33 (9H, s, C(CH3)3). Mass spectrum, m/z (Irel, %): 464 [M]+ (2), 407
(1), 388 (1), 360 (2), 338 (2), 317 (11), 316 (15), 315 [M-OPh(t-Bu)]+ (100), 302 (2), 275 (4), 259 (4). Found, %:
C 77.49; H 5.31. C30H24O5. Calculated, %: C 77.57; H 5.21.
Reaction of Bromo Derivatives of Furylchromones with Amines (General Method). A mixture of
compound 1b (1 mmol) and morpholine or piperidine (2.1 mmol) was boiled in ethanol. After completion of the
reaction (check by TLC) the solvent was evaporated in vacuum. The residue was dissolved in methylene
162

chloride, washed with water, dried, and filtered through silica gel. After evaporation in vacuum the residue was
recrystallized from ethanol.
3-Benzoyl-2-(5-morpholinofur-2-yl)-4H-chromen-4-one (4a). Yield 0.316 g (79%); mp 260-261oC.
1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.18 (1H, d, J = 7.7, H-5); 8.03 (2H, d, J = 7.3, H'-2); 7.68 (1H,
t, J = 7.7, H-7); 7.56 (1H, t, J = 7.2, H'-4); 7.36-7.48 (4H, m, H Ar); 7.24 (1H, d, J = 3.8, H-3 furan); 5.26 (1H,
d, J = 3.7, H-4 furan); 3.56-3.59 (4H, m, N(CH2CH2)2O); 2.88-2.92 (4H, m, N(CH2CH2)2O). Mass spectrum, m/z
(Irel, %): 329 [M-(CH2)2O]+ (2), 316 (2), 315 [M-morpholine]+ (40), 293 (2), 282 (2), 257 (3), 242 (3), 231 (5),
87 [morpholine] (100). Found, %: C 71.75; H 4.71. C24H19NO5. Calculated, %: C 71.81; H 4.77.
3-Benzoyl-2-[5-(piperidino)fur-2-yl]-4H-chromen-4-one (4b). Yield 0.287 g (72%); mp 212-213oC.
1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.17 (1H, d, J = 7.8, H-5); 8.06 (2H, d, J = 7.6, H'-2); 7.33-7.70
(6H, m, H Ar); 7.25 (1H, d, J = 3.4, H-3 furan); 5.20 (1H, d, J = 3.8, H-4 furan); 2.91-2.96 (4H, m,
N(CH2CH2)2CH2); 1.41-1.46 (6H, m, N(CH2CH2)2CH2). Mass spectrum, m/z (Irel, %): 400 (20), 399 [M]+ (64),
368 (3), 342 (4), 318 (5), 317 (10), 316 (25), 315 [M-piperidine]+ (100), 289 (8), 288 (36).
3-Benzoyl-2-[5-(bromomethyl)fur-2-yl]-4H-chromen-4-one (5). A mixture of compound 1a (0.330 g,
1 mmol), NBS (0.187 g, 1.05 mmol), and a catalytic amount of dibenzoyl peroxide in carbon tetrachloride was
boiled for 2 h (check by TLC). After completion of the reaction the solution was diluted with petroleum ether
(1:1) and filtered through a layer of silica gel. The solution obtained was evaporated in vacuum and the residue
was recrystallized from an acetone–petroleum ether mixture (1:1). Yield 0.31 g (85%); mp 185-186oC. 1H NMR
spectrum (200 MHz), δ, ppm (J, Hz): 8.23 (1H, dd, J = 7.9, J = 1.5, H-5); 8.02 (2H, d, J = 7.5, H'-2); 7.75 (1H,
dt, J = 5.0, J = 1.7, H-7); 7.55-7.60 (2H, m, H Ar); 7.43-7.48 (3H, m, H Ar); 7.07 (1H, d, J = 3.5, H-3 furan);
13
6.46 (1H, d, J = 3.5, H-4 furan); 4.22 (2H, s, CH2Br). C NMR spectrum (75 MHz), δ, ppm: 192.49; 176.18;
155.63; 154.71; 150.70; 145.55; 137.04; 134.48; 133.81; 129.55; 129.33; 128.85; 126.12; 125.69; 123.57;
119.66; 118.02; 116.62; 112.01; 21.54. Mass spectrum, m/z (Irel, %): 410 [M]+ (8), 409 (5), 408 (7), 373 (4), 343
(9), 330 (26), 329 [M-Br]+ (100), 315 [M-CH2Br]+ (31), 303 (18), 302 (13), 301 (59), 283 (6), 273 (6). Found,
%: C 61.61; H 3.18. C21H13BrO4. Calculated, %: C 61.63; H 3.20.
Interaction of Compound 5 with Thiol Salts (General Method). A mixture of compound 5 (0.409 g,
1 mmol) and sodium thiophenolate or KSCN (1.05 mmol) was heated in ethanol (60-70oC). After completion of
the reaction (check by TLC) the solvent was evaporated in vacuum. The residue was dissolved in methylene
chloride and filtered through a layer of silica gel. After evaporation in vacuum the residue was recrystallized
from ethanol.
3-Benzoyl-2-[5-(phenylthiomethyl)fur-2-yl]-4H-chromen-4-one (6a). Yield 0.332 g (75%); mp
1
114-115oC. H NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.23 (1H, d, J = 7.8, H-5); 8.02 (2H, d, J = 7.6,
H'-2); 7.73 (1H, t, J = 7.8, H-7); 7.42-7.59 (5H, m, H Ar); 7.14-7.30 (5H, m, H Ar); 7.00 (1H, d, J = 3.5, H-3
furan); 6.17 (1H, d, J = 3.5, H-4 furan); 3.84 (2H, s, CH2Ph). Mass spectrum, m/z (Irel, %): 438 [M]+ (4), 348 (2),
330 (33), 329 (38), 316 (3), 315 [M-CH2Ph]+ (100), 303 (5), 302 (10), 301 (38), 285 (7). Found, %: C 73.87;
H 4.10. C27H18O4S. Calculated, %: C 73.96; H 4.14.
3-Benzoyl-2-[5-(thiocyanatomethyl)fur-2-yl]-4H-chromen-2-one (6e). Yield 0.309 g (80%); mp
180-181oC. 1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.23 (1H, d, J = 7.8, H-5); 8.00 (2H, d, J = 7.3, H'-2);
7.77 (1H, t, J = 7.6, H-7); 7.43-7.63 (5H, m, H Ar); 7.13 (1H, d, J = 3.2, H-3 furan); 6.56 (1H, d, J = 3.2, H-4
furan); 3.94 (2H, s, CH2SCN). Mass spectrum, m/z (Irel, %): 387 [M]+ (4), 343 (2), 340 (5), 332 (10), 331 (26),
330 (68), 329 (100), 321 (6), 316 (32), 315 [M-CH2SCN]+ (82), 302 (26), 301 (28), 288 (5), 286 (8), 273 (6).
Found, %: C 73.77; H 4.00. C22H13NO4S. Calculated, %: C 68.21; H 3.38.
Reaction of Compound 5 with Thiols (General Method). A mixture of compound 5 (0.409 g,
1 mmol) with BuSH, t-BuSH, or thioglycolic acid ethyl ester (1.05 mmol) was stirred in DMF with gentle
heating (<50oC) in the presence of K2CO3. After completion of the reaction (check by TLC) the mixture was
poured into water. The precipitated solid was filtered off, washed with water, dissolved in methylene chloride,
the solution was dried, and filtered through silica gel. After evaporation in vacuum the residue was recrystallized
from ethanol.
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3-Benzoyl-2-[5-(tert-butylthiomethyl)fur-2-yl]-4H-chromen-4-one (6b). Yield 0.334 g (80%); mp
1
130-132oC. H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.22 (1H, d, J = 7.3, H-5); 8.02 (2H, d, J = 7.3,
H'-2); 7.74 (1H, t, J = 7.3, H-7); 7.41-7.60 (5H, m, H Ar); 7.09 (1H, d, J = 3.4, H-3 furan); 6.35 (1H, d, J = 3.4
H-4 furan); 3.51 (2H, s, CH2SCMe3); 1.16 [9H, s, SC(CH3)3]. Mass spectrum, m/z (Irel, %): 419 [M]+ (2), 418
(6), 343 (2), 330 (2), 329 (9), 317 (5), 316 (75), 315 [M-CH2SCHMe3]+ (100), 301 (11), 287 (4). Found, %:
C 71.71; H 5.23. C25H22O4S. Calculated, %: C 71.75; H 5.30.
3-Benzoyl-2-[5-(butylthiomethyl)fur-2-yl]-4H-chromen-4-one (6c). Yield 0.196 g (47%); mp
85-86oC. 1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.22 (1H, d, J = 7.7, H-5); 8.00 (2H, d, J = 7.5, H'-2);
7.74 (1H, t, J = 7.6, H-7); 7.42-7.58 (5H, m, H Ar); 7.10 (1H, d, J = 2.9, H-3 furan); 6.32 (1H, d, J = 2.8, H-4
furan); 3.45 (2H, s, CH2SC4H10); 2.30 (2H, t, J = 6.7, SCH2(CH2)2Me); 1.29-1.42 (4H, m, SCH2(CH2)2Me); 0.88
(3H, t, J = 6.8, SCH2(CH2)2CH3). Mass spectrum, m/z (Irel, %): 418 [M]+ (14), 361 (3), 347 (2),331 (15), 330
(68), 316 (23), 315 [M-CH2SBu]+ (100), 302 (8), 301 (27). Found, %: C 71.70; H 5.25. C25H22O4S. Calculated,
%: C 71.75; H 5.30.
Ethyl Ester of 2-{[5-(3-Benzoyl-4-oxo-4H-chromen-2-yl)fur-2-yl]methyl-thio}acetic Acid (6d).
Yield 0.287 g (64%); mp 123-125oC. 1H NMR spectrum (200 MHz), δ, ppm (J, Hz): 8.22 (1H, d, J = 8.1, H-5);
8.01 (2H, d, J = 7.3, H'-2); 7.75 (1H, t, J = 7.9, H-7); 7.41-7.58 (5H, m, H Ar); 7.09 (1H, d, J = 3.7, H-3 furan);
6.36 (1H, d, J = 3.7, H-4 furan); 4.17 (2H, q, J = 7.2, CH2Me); 3.64 (2H, s, CH2SCH2COOEt); 2.94 (2H, s,
CH2SCH2COOEt); 1.28 (3H, t, J = 7.2, OCH2CH3). Mass spectrum, m/z (Irel, %): 451 (5), 449 [M]+ (8), 435 (5),
416 (2), 403 (6), 385 (2), 373 (1), 362 (13), 361 (100), 343 (2), 333 (6), 331 (10), 330 (31), 329 (46), 316 (81),
315 [M-CH2SCH2COOEt]+ (99), 302 (10), 301 (39). Found, %: C 66.91; H 4.39. C25H20O6S. Calculated, %:
C 66.95; H 4.49.
3-Benzoyl-2-[5-(phenoxymethyl)fur-2-yl]-4H-chromen-4-one (7). Bromo derivative 5 (0.409 g,
1 mmol) was added to a mixture of K2CO3 (1 mmol) and phenol (1.05 mmol) in DMF and stirred at 50oC. After
completion of the reaction (check by TLC) the mixture was poured into water. The precipitated solid was
filtered off, washed with water, dissolved in methylene chloride, the solution dried, and filtered through silica
gel. After evaporation in vacuum the residue was recrystallized from ethanol. Yield of compound 7 was 84 mg
1
(20%); mp 136-138oC. H NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.24 (1H, d, J = 7.9, H-5); 7.99 (2H, d,
J = 7.8, H'-2); 7.75 (1H, t, J = 7.9, H-7); 7.40-7.58 (5H, m, H Ar); 7.22-7.25 (2H, m, H Ar); 7.10 (1H, d, J = 3.1,
H-3 furan); 6.97 (1H, t, J = 7.8, H Ar); 6.76 (2H, d, J = 8.1, H Ar); 6.49 (1H, d, J = 3.4, H-4 furan); 4.82 (2H, s,
CH2OPh). Mass spectrum, m/z (Irel, %): 422 [M]+ (2), 374 (1), 347 (1), 331 (7), 329 (100), 317 (2), 316 (8), 315
[M-CH2OPh]+ (14), 303 (1), 301 (27), 286 (4), 285 (8), 274 (4), 273 (11). Found, %: C 76.70; H 4.21. C27H18O5.
Calculated, %: C 76.77; H 4.29.
Reaction of Compound 5 with Amines (General Method). Bromo derivative 5 (1 mmol) was added to
a mixture of K2CO3 (1 mmol), and aminotoluene (1.05 mmol) or morpholine or o-toluidine (2.05 mmol) in
DMF and the mixture was stirred at room temperature. After completion of the reaction (check by TLC) the
mixture was poured into water. The precipitated solid was filtered off, washed with water, dissolved in
methylene chloride, the solution dried, and filtered through silica gel. After evaporation in vacuum the solid was
recrystallized from ethanol.
3-Benzoyl-2-[5-(morpholinomethyl)fur-2-yl]-4H-chromen-4-one (8a). Yield 0.249 g (60%); mp
1
176-178oC. H NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.21 (1H, d, J = 7.8, H-5); 8.02 (2H, d, J = 7.3,
H'-2); 7.74 (1H, t, J = 7.1, H-7); 7.54-7.59 (2H, m, H Ar); 7.42-7.47 (3H, m, H Ar); 7.13-7.15 (1H, d, J = 3.5,
H-3 furan); 6.36 (1H, d, J = 3.7, H-4 furan); 3.51-3.54 (4H, m, N(CH2CH2)2O); 3.36 (2H, s, CH2N); 2.15-2.17
(4H m, N(CH2CH2)2O). Mass spectrum, m/z (Irel, %): 397 [M-O]+ (2), 343 (1), 332 (4), 330 (19), 329 (100), 315
[M-CH2N(CH2CH2)2O]+ (2), 314 (18), 301 (5), 293 (4), 285 (3), 273 (6), 271 (5), 261 (4), 86 (7). Found, %:
C 72.19; H 5.00. C25H21NO5. Calculated, %: C 72.28; H 5.10.
3-Benzoyl-2-{5-[(o-tolylamino)methyl]fur-2-yl}-4H-chromen-4-one (8b). Yield 0.3 g (70%); mp
1
91-93oC. H NMR spectrum (300 MHz), δ, ppm (J, Hz): 8.23 (1H, dd, J = 8.0, J = 1.4, H-5); 8.00 (2H, d,
164

J = 7.2, H'-2); 7.74 (1H, dt, J = 7.8, J = 1.6, H-7); 7.39-7.59 (5H, m, H Ar); 7.00-7.09 (3H, m, H Ar); 6.68 (1H,
t, J = 7.4, H Ar); 6.33-6.41 (2H, m, H Ar); 4.18 (2H, s, CH2); 2.08 (3H, s, CH3). Mass spectrum, m/z (Irel, %):
436 [M]+ (9), 435 (53), 434 (3), 417 (2), 407 (2), 331 (5), 330 (39), 329 (61), 328 (53), 317 (16), 315
[M-CH2NPhMe]+ (100). Found, %: C 77.15; H 4.78. C28H21NO4S. Calculated, %: C 77.23; H 4.86.
The work was carried out with the support of the Russian Fund for Fundamental Investigations (Grant
10-03-00250-a).
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