3-Acyl-2-furylthiochromones: a new family of compounds with photoinduced fluorescence

Article abstract of DOI:10.1016/j.mencom.2016.11.021

New photosensitive 3-acyl-2-(2-furyl)thiochromones, potential components for multilayer media of archive-type optical discs, were prepared and tested for photorearrangement.

Full text of DOI:10.1016/j.mencom.2016.11.021

Mendeleev
Communications
Mendeleev Commun., 2016, 26, 521–523
3-Acyl-2-furylthiochromones: a new family
of compounds with photoinduced fluorescence
Konstantin A. Chudov,*a Konstantin S. Levchenko,b Valery A. Barachevskii,c
Tat’yana M. Valova,c Evgeny P. Grebennikov,b Pavel S. Shmelin,b Nikolai O. Poroshin,b
Grigory E. Adamov,b Vladimir N. Yarovenkoa and Mikhail M. Krayushkina
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian
Federation. Fax: +7 499 135 5328; e-mail: k4udov@gmail.com
b Central Scientific and Research Technological Institute ‘Technomash’, 121108 Moscow, Russian Federation
c Photochemistry Center, Russian Academy of Sciences, 119421 Moscow, Russian Federation
DOI: 10.1016/j.mencom.2016.11.021
O
O
O
S
New photosensitive 3-acyl-2-(2-furyl)thiochromones, potential
components for multilayer media of archive-type optical discs,
were prepared and tested for photorearrangement.
Me
SH
Ar
O
R
Compounds containing 3-(2-furyl)propenone system possess
photoactive properties and are capable of photoinduced isomeri-
zation under UV irradiation giving fluorescent products. The
derivatives of benzoquinones,1 chromones,2,3 and tetralones4,5 are
examples of such compounds. Recently, we obtained new repre-
sentatives possessing photoinduced fluorescence such as deriva-
tives of 2-aroyl-3-furylbenzofurans6 and 5-aroyl-4-furylthiazoles.7
Among the compounds synthesized previously, chromones are
the best studied.2,3,8–10 Photoisomerization of these compounds
is apparently of general character and can be exemplified by
isomerization of 3-acyl-2-furylchromones A.2,3
giving fluorescent products. Here, we performed the synthesis
and photochemical studies of 3-acyl-2-furylthiochromones, the
closest analogues of 3-acyl-2-furylchromones.
To synthesize compounds 1a–c, the methods similar to those
used previously in a syntheses of 3-acyl-2-furylchromones12
(Scheme 1) were employed. Thioacetophenone esters 2a,b were
obtained by acylation of 2-mercaptoacetophenone16 with benzoyl
or 2-thenoyl chlorides in the presence of triethylamine. However,
it appears that the classical conditions of the Baker–Venkataraman
rearrangement (ButOK in DMF) when applied to 2a,b led to an
OH
Ar
O
O
O
O
Ar
O
Ar
Me
Me
i
ii
O
O
O
hv
XH
X
XH
O
O
R
O
Ar
X = S, O
3a–c
2a–c
A
O
O
O
O
R
O
R
Ar
O
O
Ar
O
iii
XH
4a–d
R
O
O
X
OH
O
O
O
B
Ar
O
Ar
O
iv
R
X
We have obtained a large series of 3-acyl-2-furylchromones
with donor and acceptor substituents located at different positions
of the molecule. The influence of their structures on the physical
and chemical properties was revealed, and the possibility of their
application as components of registering media in multilayer
optical discs of extra high capacity with single-use, double-photon
bit-by-bit (bitwise) record and fluorescent reading of optical
information was proven.11–15
R
R
4'a–d
2, 3: a X = S, Ar = Ph
1a–d
1, 4, 4': a X = S, Ar = Ph, R = H
b X = S, Ar = Ph, R = Me
c X = S, Ar = 2-thienyl, R = H
d X = O, Ar = 2-thienyl, R = H
b X = S, Ar = 2-thienyl
c X = O, Ar = 2-thienyl
Scheme 1 Reagents and conditions: i, X = S, ArC(O)Cl, CH2Cl2, Et3N or
X = O, ArC(O)Cl, Py; ii, X = S, LDA (2 equiv.), THF, –15–0°C (Ar = Ph)
or –78 to –40°C (Ar = 2-thienyl) or X = O, ButOK, DMF, –10–0°C;
iii, 2-furaldehyde, piperidine (cat.), EtOH, 20–40°C; iv, SeO2, dioxane, reflux.
This work is a continuation of a search for new photoactive
compounds which can undergo irreversible photoisomerization
© 2016 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
– 521 –

Mendeleev Commun., 2016, 26, 521–523
inseparable mixture of products instead of diketones 3a,b. Also,
C(21)
C(20)
C(22)
S(23)
an attempted treatment of 2a with lithium diisopropylamide
(LDA) in THF17 followed by acidification afforded the cycliza-
tion product, 2-phenyl-4H-thiochromen-4-one. To avoid the
cyclization, the reaction mixture was treated under neutral con-
ditions providing the product 3a in 63% yield.
O(11)
C(4)
C(19)
O(18)
C(17)
C(3)
C(6)
C(5)
To obtain diketone 3b (27%), compound 2b was treated with
2 equiv. of LDA at –70 to –40°C in THF. Diketones 3a,b were
reacted with 2-furaldehyde and 5-methyl-2-furaldehyde giving the
products existing in two forms: 4a–c or 4'a–c. Thiochromanones
bearing benzoyl groups were isolated presumably as an enol
form 4', which was confirmed by 1H NMR spectra. The product
of condensation of diketone 3b with furaldehyde was isolated as
a mixture of two forms (4c, 4'c) and used for the next step
without isolation of individual components. Compounds 4a–c
(4'a–c) were oxidized with 1.5 equiv. of SeO2 in dioxane under
reflux affording 1a–c in 78–92% yields (see Scheme 1).†
Further oxidation of thiochromones 1a,b with m-CPBA allowed
us to obtain 1,1-dioxidothiochromones 5a,b (Scheme 2).
C(7)
C(8)
C(12)
C(13)
C(14)
C(2)
C(10)
C(9)
S(1)
O(16)
C(15)
Figure 1 X-ray structure of 1c. The atoms are represented as thermal
ellipsoids at 50% probability level.
C(23)
C(22)
C(21)
O(3)
O(20)
C(24)
C(19)
C(1)
C(2)
C(5)
C(25)
C(26)
O(18)
C(6)
C(4)
1
The structures of 1a–c and 5a,b were confirmed by H and
C(13)
C(14)
C(9)
13C NMR, high-resolution mass spectra (HRMS); for compounds
1c and 5a, X-ray analysis was performed (Figures 1 and 2).‡
It is evident from Table 1 that the replacement of the oxygen
atom (compound 1d) by sulfur in the chromone fragment (com-
C(17)
C(16)
C(7)
C(8)
S(10)
O(11)
O(12)
C(15)
O
Ph
O
Ph
Figure 2 X-ray structure of 5a. The atoms are represented as thermal
ellipsoids at 50% probability level.
O
O
O
O
i
pound 1c) results in appearance of two new long-wave absorption
bands at 330 and 357 nm (sh) (Figure 3) thus making possible
photoactivation of the latter compound with near UV light.
Absorption band maximum for the photoproduct of compound
1c has a batochromic shift of 10 nm, and the maximum of the
fluorescence band has a hypsochromic shift of 17 nm as compared
to the maxima of the corresponding bands for compound 1d.
Simultaneously, both compounds 1c and 1d have a comparable
photosensitivity of formation of the photoproduct, which is deter-
mined as a photoinduced optical density at the maximum of the
band of the photoproduct before the beginning of photodegrada-
tion normalized on the optical density in the absorption band
maximum of the starting compound in the range of photoactiva-
tion (DmBax/DAmax) (Table 1). Compound 1c has slightly smaller
S
R
S
R
O
O
1a,b
5a,b
a R = H
b R = Me
Scheme 2 Reagents and conditions: i, m-CPBA, CH2Cl2.
†
Thiochromones 1a–c (general procedure). A mixrure of two forms
4a–c/4'a–c (1 mmol) was dissolved in dioxane (2 ml), SeO2 (1.5 mmol)
was added, and the mixture was refluxed until the starting material disap-
peared (TLC control). Dioxane was removed under reduced pressure, the
residue was dissolved in chloroform (5 ml) and the solution was filtered
through a small column with silica gel with elution by a mixture of
methylene chloride–light petroleum (1:1). After evaporation of the eluent,
the resulting yellow crystals were washed with ethanol.
3-Benzoyl-2-(2-furyl)thiochromone 1a. Yield 0.3 g (90%), mp 235–
237°C. 1H NMR (300 MHz, CDCl3) d: 8.48 (d, 1H, J 8.0 Hz), 7.97 (d,
2H, J 7.4 Hz), 7.68 (d, 2H, J 3.7 Hz), 7.62–7.51 (m, 2H), 7.50–7.39
(m, 3H), 6.86 (d, 1H, J 3.6 Hz), 6.45 (dd, 1H, J 3.6, 1.7 Hz). 13C NMR
(75 MHz, CDCl3) d: 195.46, 179.16, 146.87, 145.74, 138.36, 136.54,
136.20, 133.59, 132.11, 130.78, 130.42, 129.05, 128.84, 128.75, 127.97,
126.20, 114.90, 112.77. HRMS, m/z: 333.0585 [M + H]+, 355.0401
[M + Na]+, 371.0139 [M + K]+ (calc. for C20H12O3S, m/z: 333.0580,
355.0399, 371.0139).
3-Benzoyl-2-(5-methylfuran-2-yl)thiochromone 1b. Yield 0.32 g (92%),
mp 192–194°C. 1H NMR (300 MHz, CDCl3) d: 8.46 (d, 1H, J 8.0 Hz),
7.97 (d, 2H, J 7.3 Hz), 7.64 (d, 2H, J 3.9 Hz), 7.59–7.49 (m, 2H), 7.43
(t, 2H, J 7.5 Hz), 6.75 (d, 1H, J 3.5 Hz), 6.04 (d, 1H, J 3.3 Hz), 2.17 (s,
3H). 13C NMR (75 MHz, CDCl3) d: 195.76, 179.17, 156.78, 145.10,
138.36, 136.70, 136.15, 133.44, 132.00, 130.41, 129.42, 129.03, 128.72,
128.68, 127.80, 126.15, 116.40, 109.46, 13.55. HRMS, m/z: 347.0737
[M + H]+, 369.0557 [M + Na]+, 385.0295 [M + K]+ (calc. for C21H14O3S,
m/z: 347.0736, 369.0556, 385.0295).
2-(2-Furyl)-3-(thiophen-2-ylcarbonyl)thiochromone 1c. Yield 78%,
mp 227–229°C. 1H NMR (300 MHz, CDCl3) d: 8.50 (d, 1H, J 8.0 Hz),
7.74–7.50 (m, 6H), 7.05 (t, 1H, J 4.3 Hz), 6.92 (d, 1H, J 3.6 Hz), 6.47
(dd, 1H, J 3.3, 1.5 Hz). 13C NMR (75 MHz, CDCl3) d: 187.31, 178.77,
146.69, 145.87, 143.87, 138.91, 136.07, 134.74, 134.02, 132.17, 130.47,
130.42, 128.89, 128.25, 128.04, 126.24, 115.16, 112.90. HRMS, m/z:
339.0144 [M + H]+, 360.9964 [M + Na]+, 376.9703 [M + K]+ (calc. for
C18H10O3S2, m/z: 339.0147, 360.9959, 376.9703).
‡
Crystallographic data.
Crystals of 1c (C18H10O3S2, M = 338.38) are monoclinic, space group
P21/n, at 120 K: a = 7.4352(6), b = 10.2324(7) and c = 19.3193(14) Å,
b = 95.189(2)°, V = 1463.79(19) Å3, Z = 4 (Z' = 1), dcalc = 1.535 g cm–3,
m(MoKa) = 3.76 cm–1, F(000) = 696.
Crystals of 5a (C20H12O5S, M = 364.36) are orthorhombic, space group
P212121, at 120 K: a = 8.0407(6), b = 11.5563(9) and c = 17.5501(13) Å,
V = 1630.8(2) Å3, Z = 4 (Z' = 1), dcalc = 1.484 g cm–3, m(MoKa) =
2.29 cm–1, F(000) = 752.
Intensities of 17241 and 19644 reflections for 1c and 5a, respectively,
were measured with a Bruker APEX2 CCD diffractometer [l(MoKa) =
= 0.71072 Å, w-scans, 2q < 58°], 3890 and 4330 independent reflections
[Rint = 0.0377 and 0.0487] were used in further refinement for 1c and 5a,
respectively. Structures were solved by direct method and refined by the
full-matrix least-squares technique against F2 in the anisotropic–isotropic
approximation. Positions of hydrogen atoms were calculated, and they
were refined in the isotropic approximation within the riding model. For
1c, the refinement converged to wR2 = 0.0975 and GOF = 1.047 for all
independent reflections [R1 = 0.0369 was calculated against F for 3134
observed reflections with I > 2s(I)]. For 5a, the refinement converged to
wR2 = 0.0937 and GOF = 1.003 for all independent reflections [R1 = 0.0405
was calculated against F for 3819 observed reflections with I > 2s(I)].
All calculations were performed using SHELXTL PLUS 5.0.18
CCDC 1443807 and 1443808 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk.
For more detail, see Online Supplementary Materials.
– 522 –

Mendeleev Commun., 2016, 26, 521–523
Table 1 Spectral kinetic characteristics of compounds 1 and 5.a
1.0
1
2
IBfl,max
(arbitrary t1/2/s
units)
0.8
0.6
0.4
Com- lAmax
pound nm
/
e/dm3
lmBax
/
DBmax
/
lfBl,max/ Dl/
nm
mol–1 cm–1 nm
DAmax nm
1a
293
330
15250
15750
424 0.14 486
62 248
1580
8
0.2
0.0
357(sh)
1b
1c
294
343
17500
30000
422 0.10 494
445 0.17 503
72 372
457
290
340
390
l/nm
440
490
294
330
18750
14750
58 345
1545
Figure 4 Absorption spectra of compound 5b in toluene (1) before and
(2–8) after successive UV irradiation through UFS-1 light filter.
357(sh) 11250
1d
5a
5b
305
379
400
25000
16750
21500
435 0.15 520
362 0.29 488
342 0.35 482
85 464
897
630
127
126
9
group, 6.65–6.75 ppm (dd, J 15.6, 7.9 Hz) for both photoproducts.
In the EI mass spectrum (70 eV), the peaks of a molecular ion
and a fragment of forms B [M–CHCHCHO]+ were detected.
In conclusion, we have synthesized new photosensitive 3-acyl-
2-(2-furyl)thiochromones which undergo irreversible photo-
induced transformations into fluorescent products. These com-
pounds and their analogues could be considered as specific
organic hybrid systems and serve as starting materials for the
further synthesis of condensed products and components of
optical memory.19
140 12
a lmAax, lBmax, and lfBl,max are the wavelengths at maxima of absorption bands of
forms A and B and a wavelength at maximum of fluorescence of form B,
respectively; DmAax and DmBax are the optical densities at maxima of absorption
bands of forms A and B before photodegradation of the compounds; Dl is
the Stokes shift; IBfl,max is the fluorescence intensity in the maximum of
fluorescence band in photoinduced form B before photodegradation; t1/2 is
the time during which the value of optical density in the maximum of the
absorption band of form B is reduced twice under non-filtered irradiation
with xenon lamp.
0.8
0.6
0.4
0.2
0.0
2000
1500
1000
500
0
This work was supported by the Russian Science Foundation
(grant no. 14-50-00126).
1
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2016.11.021.
2
3
4
290
390
490
590
690
References
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Figure 3 (1, 2) Absorption spectra, (3) fluorescence excitation measured
at 503 nm and (4) fluorescence by excitation at 424 nm of chromone 1c in
toluene (1) before and (2–4) after UV irradiation.
maximum of fluorescence intensity than that of chromone 1d,
however the stability of its photoproduct towards unfiltered irradia-
tion is higher almost twice, which is important for practical use.
In a transfer from compound 1c possessing thienol fragment
to 1a bearing benzoyl fragment, hypsochromic shifts of absorp-
tion bands (21 nm) and fluorescence (16 nm) of the photoproduct
were observed along with the decrease in fluorescence intensity.
Introduction of methyl substituent in furyl fragment (compound
1b) results in strong increase in efficiency of photodegradation
of the photoproduct and decrease in photosensitivity of the starting
compound.
It is important to note that 1,1-dioxidothiochromones 5a,b,
in which sulfonyl fragments possess strong electron-acceptor
effect, do not form photoproducts with long-wave absorption
band under UV irradiation.
Figure 4 demonstrates the disappearance of the absorption
band of compound 5b in toluene with the maximum at 400 nm and
simultaneous appearance of the photoproduct absorption band
(the maximum at 342 nm). Similar behavior is observed for com-
pound 5a. Both compounds 5a,b have weak fluorescence during
excitation at the maximum of absorption of the photoproducts,
but not at the absorption band maximum of the starting compound,
which sufficiently increases the Stokes shift. Both compounds
5a,b are less photochemically stable than their analogues 1a,b.
A comparative analysis of properties of photoproducts (form B)
of chromone 1d and thiochromone 1c was carried out. In 1H NMR
spectra of photoproducts, one can find two characteristic signals:
signals of aldehyde protons at 9.67 and 9.70 ppm (d, J 7.9 Hz),
respectively; signal of protons located at a-position to the aldehyde
Received: 28th April 2016; Com. 16/4923
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