Electronic absorption spectra of arylmethylene, ethylidene, and allylidene 3H-furan-2-one derivatives

Article abstract of DOI:10.1134/S1070363207080130

The electronic absorption spectra of 3H-furan-2-ones containing substituents with varied length of the conjugation chain in position C ³ of the heteroring are examined. The conclusions are made about the direction of the band shift depending on

Full text of DOI:10.1134/S1070363207080130

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 8, pp. 1366 1369.
Pleiades Publishing, Ltd., 2007.
Original Russian Text A.Yu. Egorova, I.E. Kamneva, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 8, pp. 1287 1290.
Electronic Absorption Spectra of Arylmethylene, Ethylidene,
and Allylidene 3H-Furan-2-one Derivatives
A. Yu. Egorova and I. E. Kamneva
Chernyshevskii Saratov State University,
ul. Astrakhanskaya 83, Saratov, 410012 Russia
e-mail: kwirina1982@mail.ru
Received November 15, 2006
Abstract The electronic absorption spectra of 3H-furan-2-ones containing substituents with varied length
of the conjugation chain in position C3 of the heteroring are examined. The conclusions are made about the
direction of the band shift depending on the structure and size of the conjugation system of the substituents.
DOI: 10.1134/S1070363207080130
In this study we examined arylmethylene, ethyl-
idene, and allylidene derivatives of 3H-furan-2-ones,
which are widely used as intermediates in the synthesis
of various ali- and heterocyclic compounds exhibiting
the biological activity.
absorption and to correlate the nature of substituents
with the absorption band shifts.
Published data concerning this problem are scarce.
There are only a few articles dealing with the effect of
substituent in position 5 of the heteroring [1] on the
color of the compounds [2] and on the shift of the
absorption bands in the UV spectra of 5-aryl-3-benzyl-
idene-3H-furan-2-ones.
Electronic spectroscopy is the best experimental
tool for studying conjugated systems and fine struc-
tures of organic compounds.
The presence of the conjugated C=C, C=O bonds
and the aromatic ring with substituents of different
nature in the 3H-furan-2-one derivatives that we study
allows the molecule to be considered as an integrated
resonator. The aim of our study was to establish the
characteristic conjugated system responsible for the
Arylmethylene (I V) and ethylidene (VI VIII)
derivatives of 3H-furan-2-one were prepared by con-
densation of 4-oxo-4-arylbutanoic acids with aromatic
aldehydes [3] and alkylaromatic ketones [4] according
to the published procedures.
O
Ar
Ar
H
Ph
O
AcONa
O
Ac2O
I IV
Ph
R
COOH
CH3
CH3
O
O
Ph
O
(COONH4)2
R
O
VI VIII
, V: Ar =
,
I: Ar = Ph, II: Ar = 4-NO2 C6H4, III: Ar = 3-NO2 C6H4, IV: Ar =
VI: R = H, VII: R = Cl, VIII: R = NO2.
NO2
O
O
The structure of compounds VI VIII suggests that
the methyl group protons are labile, because of the
effect of the carbonyl group in the furan ring, the
exocyclic C=C bond, and also the activating effect of
the electron-withdrawing substituent in the aromatic
ring. These factors allow 3-ethylidene-3H-furan-2-
ones VI VIII to be used as methylene components in
the condensation with aromatic aldehydes [5].
1366

ELECTRONIC ABSORPTION SPECTRA OF ARYLMETHYLENE, ETHYLIDENE
1367
We have used the aldehydes of the aromatic and
log
heterocyclic series.
4.6
4.4
4.2
4.0
3.8
3.6
NO2
3
O
H
R
+
CH3
O
Ph
2
1
3.4
3.2
3.0
O
NO2
VIII
230
280
330
380
430
, nm
C2H5OH
Fig. 1. Absorption band shift depending on the substituent
in the C position of 3H-furan-2-one. (1) I, (2) II, and
R
3
HN
O
Ph
(3) IV.
O
system with electron transfer, which causes the batho-
chromic shift of the absorption band (Fig. 1, com-
pounds I and II).
IX: R = Ph, X: R = m-NO2 C6H4,
XI: R =
.
, XII: R =
NO2
O
O
R
R
+
N
H
O C=C C
1
According to the IR and H NMR data, the com-
pounds prepared were identified as 5-phenyl-3-[3-(R-
phenyl)-1-(4-nitrophenyl)allylidene]-3H-furan-2-ones
IX and X, and 5-phenyl-3-[3-(5-R1-furyl)-1-(4-nitro-
phenyl)allylidene]-3H-furan-2-ones XI and XII.
Introduction of the furyl residue instead of the
phenyl group also causes a bathochromic shift (com-
pounds I and IV in Fig. 1), which is caused by excess
-electron density in the furan ring and involvement
of the lone electron pair of oxygen in the common
conjugation chain.
The UV spectra of I XII mainly contain two ab-
sorption bands (see table). The absorption band with
260 nm is common for all the 3H-furan-2-one
max
derivatives and belongs to the C=C Ph fragment. The
chromophore responsible for the second absorption
<
> O
O
band with
361 455 nm includes the conjugated
+
carbonyl framgamx ent O=C C=C Ar. Hence, the 3H-
furan-2-one arylidene derivatives contain active , -
unsaturated carbonyl fragment, which accounts for
their participation in the Michael condensation and
the previously reported results of the reaction with
Grignard reagents [6].
UV spectral parameters of I XII
Comp.
no.
max1, nm
log
max2, nm log
2
1
To account for the effect of substituents on the
absorption band location, it is necessary to consider
the structure of the , -unsaturated carbonyl fragment
with the formal charge resulting from the -electron
transfer.
I
II
262
260
260
260
260
260
260
260
260
260
260
266
4.14
4.14
4.42
4.05
4.13
4.14
4.12
4.14
4.45
4.37
4.39
4.32
389
410
391
409
445
361
373
375
395
400
415
455
4.36
4.47
III
IV
V
VI
VII
VIII
IX
X
4.39
4.26
4.25
4.45
4.42
4.45
4.46
4.38
4.39
4.52
H
O C=C C
H
O=C C=C
|
+
<
>
It can be seen from the resonance structure that the
effect of polar substituents in p-position ( NR2, OR,
NO2) will be the most significant. These substituents
make longer the effective chain of the conjugated
XI
XII
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 8 2007

1368
log
EGOROVA, KAMNEVA
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
1
2
230
280
330
380
430
, nm
0
30
60
90
Angle , deg
Fig. 2. Absorption band shift of 5-phenyl-3-phenylethyl-
idene-3H-furan-2-one VI as compared to 5-phenyl-3-
phenylmethylene-3H-furan-2-one I. (1) I and (2) VI.
Fig. 3. Resonance energy as a function of angle
between the planes of the conjugated chromophores.
The absorption band of 3H-furan-2-one ethylidene
derivatives VI VIII is shifted hypsochromically as
compared to arylmethylene derivatives I V, which is
probably due to the effect of the methyl group. This
group sterically hinders the existence of the planar
resonance structure (Fig. 2).
It is known that the interaction in conjugated un-
saturated systems is the strongest when the un-
saturated groups are coplanar. If their planes form
angle , the resonance energy will be proportional to
cos2 (Fig. 3).
Figure 3 shows that small angles (up to 20 C) do
not noticeably distort the conjugation as compared to
the planar system, whereas at large rotation angles the
interaction between the unsaturated groups becomes
negligible, and the chromophores become essentially
separated.
I
Proceeding from this standpoint, we carried out
quantum-chemical calculations of the geometry of
arylmethylene (I V) and ethylidene (VI VIII) 3H-
furan-2-one derivatives by the PM3 method using the
MOPAC program (Fig. 4). These calculations showed
that for 3-arylmethylene-3H-furan-2-one the phenyl
ring deviates from the heteroring plane by 18.3 ,
whereas in 3-ethylidene-3H-furan-2-one the dihedral
angle is as large as 52.1 . This fact accounts for the
difference in the electronic absorption spectra.
For allylidene derivatives of 3H-furan-2-ones IX
XII, the absorption band is shifted bathochromocally
as compared to the corresponding arylmethylene
derivatives I V, which is due to the presence of an
additional dimethine group and to an increase in the
effective length of the conjugated system (Fig. 5).
VI
Fig. 4. Steric structures of 5-phenyl-3-phenylmethylene-
3H-furan-2-one I and 5-phenyl-3-phenylethylidene-3H-
furan-2-one VI.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 8 2007

ELECTRONIC ABSORPTION SPECTRA OF ARYLMETHYLENE, ETHYLIDENE
1369
Arylmethylene (I V), ethylidene (VI VIII), and
allylidene (IX XII) 3H-furan-2-one derivatives were
prepared by the previously described procedures [3 5].
log
4.6
4.4
4.2
ACKNOWLEDGMENTS
2
4.0
3.8
3.6
3.4
3.2
3.0
The study was financially supported by the Russian
Foundation for Basic Research (project no. 05-03-
32196).
1
REFERENCES
1. Hanna, C. and Schueler, F.W., J. Am. Chem. Soc.,
1953, vol. 75, no. 5, p. 741.
230
280
330
380
430
480
, nm
2. Schueler, F.W. and Hanna, C., J. Am. Chem. Soc.,
1951, vol. 73, no. 13, p. 3528.
3. Egorova, A.Yu. and Chadina, V.V., Arilidenovye proiz-
vodnye 3H-furan-2-onov. Sintez i reaktsii (Arylidene
Derivatives of 3H-Furan-2-ones. Synthesis and Reac-
tions), Saratov: Saratov. Gos. Univ., 2004.
Fig. 5. Absorption band shift for 5-phenyl-3-[3-phenyl-1-
(4-nitrophenyl)allylidene]-3H-furan-2-one IX as com-
pared to 5-phenyl-3-phenylmethylene-3H-furan-2-one I.
(1) I and (2) IX.
4. Kamneva, I.E. and Burukhina, O.V., Abstract of Papers,
Materialy mezhdunarodnoi konferentsii studentov i
aspirantov po fundamental’nym naukam Lomonosov-
2005 (Proc. Int. Conf. of Students and Post-Graduates
in the Field of Basic Sciences Lomonosov-2005 ),
Moscow, 2005, Chemistry section, vol. 1, p. 151.
Thus, in the series of arylmethylene, ethylidene,
and allylidene 3H-furan-2-one derivatives the absorp-
tion band at 361 415 nm belongs to the O=C C=C Ar
enone group, and its location depends on the nature
of substituents in the aromatic ring, on the steric
factors, and on the size of the conjugated system.
5. Kamneva, I.E., Burukhina, O.V., and Egorova, A.Yu.,
Izv. Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol.,
2005, no. 11, p. 20.
EXPERIMENTAL
The UV spectra were taken on an SF-201 spectro-
5
6. Chadina, V.V., Cand. Sci. (Chem.) Dissertation,
photometer from 10 M solutions of compounds in
chloroform.
Saratov, 2004.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 8 2007