Synthesis and properties of photoacylotropic (2Z)-2-(N-acyl-N- arylaminomethylidene)benzo[b]thiophen-3(2H)-ones with a chiral migrating group

Article abstract of DOI:10.1007/s11172-006-0191-5

New photochromic (2Z)-2-(N-acyl-N-arylaminomethylidene)benzo[b]thiophen- 3(2H)-ones containing L-amino acid derivatives as migrating groups were synthesized. Light irradiation of their solutions at 436 nm leads to the photoinduced acylotropic rearrangemen

Full text of DOI:10.1007/s11172-006-0191-5

Russian Chemical Bulletin, International Edition, Vol. 54, No. 12, pp. 2783—2789, December, 2005
2783
Synthesis and properties of photoacylotropic
(2Z )ꢀ2ꢀ(NꢀacylꢀNꢀarylaminomethylidene)benzo[b]thiophenꢀ3(2H )ꢀones
with a chiral migrating group
a
a
b
b
c
V. P. Rybalkin,a Ya. Yu. Vorob´eva, G. S. Borodkin, A. D. Dubonosov, A. V. Tsukanov, V. V. Tkachev,
ꢀ
S. M. Aldoshin,c V. A. Bren´,a,b and V. I. Minkina,b
aInstitute of Physical and Organic Chemistry, Rostov State University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Еꢀmail: dubon@ipoc.rsu.ru
bSouthern Scientific Center, Russian Academy of Sciences,
41 ul. Chekhova, 344006 RostovꢀonꢀDon, Russian Federation.
Еꢀmail: sscꢀras@mmbi.krinc.ru
cInstitute of Problems of Chemical Physics, Russian Academy of Sciences,
1 prosp. Akad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation.
Еꢀmail: sma@icp.ac.ru
New photochromic (2Z )ꢀ2ꢀ(NꢀacylꢀNꢀarylaminomethylidene)benzo[b]thiophenꢀ3(2H )ꢀ
ones containing Lꢀamino acid derivatives as migrating groups were synthesized. Light irradiaꢀ
tion of their solutions at 436 nm leads to the photoinduced acylotropic rearrangement N → O
accompanied by migration of the chiral fragment. The bulky Nꢀacyl group causes steric strain
thus destabilizing the amide form of compounds and facilitating the photorearrangement.
Key words: benzo[b]thiophene, ketoenamine, photochromic compounds, chirality.
The photoinduced acylotropic rearrangement of
(2Z )ꢀ2ꢀ(NꢀacylꢀNꢀarylaminomethylidene)benzo[b]thioꢀ
phenꢀ3(2H )ꢀones (Scheme 1)1 makes it possible to perꢀ
form migration of large fragments within the molecules
under light, resulting in changes in their physical and
chemical properties. Such molecular systems can exhibit
properties of molecular switches, as we have demonstrated
earlier for photoacylotropic systems containing a fluoroꢀ
phoric migrating group2 and photoacylotropic chemoꢀ
sensors.3,4
Scheme 1
The aim of the present study was to synthesize photoꢀ
acylotropic systems containing a chiral migrating acyl
group and investigate their structures and photochroꢀ
mic properties for the purpose of designing chiroptical
switches.5,6
Results and Discussion
We chose natural amino acids, such as Lꢀalanine,
Lꢀleucine, Lꢀisoleucine, and Lꢀmethionine, as the starting
compounds containing a chiral center, viz., the asymmetꢀ
ric carbon atom, because the chiral center in these comꢀ
pounds is at the carbon atom nearest to the carboxy group.
In addition, optically pure enantiomers of these comꢀ
pounds are commercially available. The target compounds
with chiral acyl migrating groups were synthesized as folꢀ
lows. Amino acid chlorides with the phthalimide protecꢀ
tion of the amino group were prepared. The reactions of
the latter with ketoenamines 3 in acetonitrile in the presꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2690—2696, December, 2005.
1066ꢀ5285/05/5412ꢀ2783 © 2005 Springer Science+Business Media, Inc.

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Rybalkin et al.
ence of triethylamine gave Nꢀ and Oꢀacyl derivatives 1a—i
and 2c,j—m. Photoirradiation of solutions of 1a—i afꢀ
forded solutions of compounds 2a—i, which were not
isolated preparatively (Scheme 2).
pounds 2j—m in the Nꢀacyl form failed. In these cases,
acylation occurs only at the oxygen atom (see Scheme 2).
Fractional crystallization of the reaction product of
2ꢀ[Nꢀ(4ꢀiodophenyl)aminomethylidene]benzo[b]thioꢀ
phenꢀ3(2H )ꢀone with (2S)ꢀ(1ꢀphthal)iminopropionyl
chloride afforded both isomers, viz., Nꢀacylated (Zꢀ1c)
and Oꢀacylated (2c). The structures of the reaction prodꢀ
ucts were established by electronic and vibrational specꢀ
troscopy and 1H NMR spectroscopy.
Scheme 2
The electronic absorption spectra of the Nꢀacyl isoꢀ
mers are virtually identical to each other and are characꢀ
terized by a longꢀwavelength band at λ = 426—429 nm,
which is independent of the nature of the substituent in
the Nꢀphenyl ring (Table 1).
The IR spectra of the Nꢀacyl derivatives show, along
with symmetric and asymmetric carbonyl stretching
bands of the phthalimide protecting group at
νsC=O ~1780—1760 cm–1 and νasC=O ~1730—1710 cm–1
respectively, carbonyl stretching bands of the
benzothiophene fragment at νC=O ~1675—1655 cm–1
The stretching bands of the amide carbonyl group at
1720—1690 cm–1 overlap with the asymmetric stertching
bands of the phthalimide fragment. In the 1H NMR specꢀ
tra, the singlet of the methine proton at δ 8.60—9.08 is
evidence for the Z configuration of the Nꢀacyl derivatives,
which is confirmed by Xꢀray diffraction data for comꢀ
pound 1i.
,
R = Me, R´ = 2ꢀOMe (а); R = Me, R´ = 2ꢀBr (b);
R = Me, R´ = 4ꢀI (c); R = CH(Me)CH2Me, R´ = 2ꢀOMe (d);
R = CH(Me)CH2Me, R´ = Mes (e); R = CH2CH(Me)2,
R´ = 2ꢀOMe (f); R = (CH2)2SMe, R´ = 2ꢀOMe (g);
R = (CH2)2SMe, R´ = 4ꢀI (h); R = (CH2)2SMe, R´ = Mes (i);
R = Me, R´ = 2ꢀMe (j); R = Me, R´ = 2ꢀNO2 (k);
.
R = Me, R´ = 2,3ꢀ(CH)4 (l); R = (CH2)2SMe, R´ = 2,3ꢀ(CH)4 (m)
Only compounds 1a—i were prepared in the Nꢀacyl
Z form necessary for the photoinduced acylotropic rearꢀ
rangement N → O. Attempts to synthesize isomeric comꢀ
Table 1. Spectroscopic and photochromic characteristics of acylated ketoenamines
Comꢀ
pound
Solvent
Electronic absorption spectrum, λmax/nm (ε •10–4/L mol–1 cm–1
)
Quantum yield,
max
ϕ
→
1
2
N Isomer
O Isomer
1а
1b
1c
1d
1e
1f
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
Toluene
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
307 (2.20), 426 (1.24)
259 (2.14), 307 (2.20), 427 (1.16)
306 (2.45), 424 (1.16)
258 (2.08), 306 (2.55), 424 (1.11)
308 (2.18), 426 (1.19)
255 (2.42), 308 (2.25), 425 (1.19)
308 (2.29), 425 (1.29)
259 (2.14), 308 (2.30), 427 (1.25)
311 (2.70), 429 (1.40)
260 (2.50), 312 (2.71), 430 (1.31)
308 (2.44), 427 (1.32)
260 (2.49), 309 (2.47), 425 (1.22)
309 (2.41), 428 (1.30)
309 (2.31), 427 (1.15)
310 (2.32), 428 (1.30)
310 (2.35), 424 (1.13)
310 (2.77), 429 (1.36)
311 (2.59), 429 (1.17)
—
310 (1.96), 347 (1.44)
305 (2.07), 342 (1.41)
312 (2.09), 345 (1.77)
254 (1.37), 308 (2.20), 339 (1.81)
351 (2.70)
0.41
0.48
0.45
0.41
0.43
0.50
0.55
0.61
0.55
310 (2.16), 345 (2.70)
309 (2.06), 346 (1.56)
305 (2.11), 342 (1.42)
307 (2.60), 341 (0.96)
254 (1.76), 307 (2.81), 340 (0.80)
310 (2.14), 347 (1.64)
307 (2.29), 341 (1.50)
310 (2.08), 347 (1.56)
306 (2.12), 345 (1.40)
315 (2.10), 351 (2.62)
313 (2.19), 349 (2.75)
304 (2.62), 340 (0.96)
305 (2.26), 333 (0.86)
310 (2.16), 345 (2.70)
307 (2.08), 342 (1.68)
310 (2.08), 343 (1.96)
308 (2.16), 350 (1.49)
310 (2.18), 352 (1.51)
1g
1h
1i
2c
2j
2k
2l
—
—
—
—
—
—
—
—
—
2m

Chiral photoacylotropic benzo[b]thiophenones
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 12, December, 2005 2785
The electronic spectra of solutions of the Oꢀacyl isoꢀ
mers of 2a—m show a characteristic longꢀwavelength abꢀ
sorption band at λ = 340—351 nm, whose intensity, shape,
and position depends on the nature of the Nꢀphenyl subꢀ
stituent R´ (see Table 1). For examples, this band in the
spectra of compounds 2h, 2g, and 2i in toluene is obꢀ
served at λ (ε) of 351 (2.62), 347 (1.56), and 340 (0.96) nm,
respectively. In this series, the intensity of the band deꢀ
creases and is virtually independent of the structure of the
substituent in the acyl group. In addition to the aboveꢀ
described two C=O bands of the phthalimide protecting
group, the doubleꢀbond stretching vibration region in the
IR spectra of these isomers contains a stretching band of
the ester carbonyl group at ~1760—1750 cm–1, which
can overlap with the symmetric stretching band of the
phthalimide group.
The 1H NMR spectra of solutions of the N and
O isomers show, along with signals of the ketoenamine
fragment, a fourꢀproton multiplet of the phthalimide proꢀ
tecting group at low field and characteristic signals for the
protons of the amino acid residues at high field.
Light irradiation of solutions of all Nꢀacyl isomers
(Zꢀ1) in toluene and acetonitrile at λexc = 436 nm leads to
the photoinduced acylotropic rearrangement N → O (see
Scheme 1) giving rise to Oꢀacyl isomers 2 with high quanꢀ
tum yields (see Table 1). The structures of the photoꢀ
acylotropic rearrangement products were established based
on characteristic absorption in the UV spectra. The prodꢀ
uct obtained in a photoreactor (light irradiation at λexc =
436 nm) from compound 1c is identical to the Oꢀacyl
isomer (2c).
In the case of compounds 2a,b,d—g,i, the reverse
acylotropic rearrangement O → N occurs upon the addiꢀ
tion of trichloroacetic acid to solutions of the Oꢀacyl isoꢀ
mers prepared photochemically. For compounds 2c,h,
the acylotropic rearrangement O → N ceased once the
equilibrium is reached, whereas this rearrangement is not
observed for compounds 2j—m.
1
The H NMR spectra of mesityl derivatives 1e,i show
diastereotopism of the orthoꢀmethyl and aromatic proꢀ
tons of the mesityl ring (Fig. 1). In deuterionitrobenzene,
this anisochronism of the signals is retained upon heating
to 180 °C. This is evidence for hindered rotation of the
mesityl ring about the CAr—N bond, which, in turn, conꢀ
firms the atropoisomerism in (2Z )ꢀ2ꢀ(NꢀacylꢀNꢀarylꢀ
aminomethylidene)benzo[b]thiophenꢀ3(2H )ꢀones conꢀ
taining the orthoꢀsubstituted Nꢀphenyl ring, which we
have found earlier.6
As expected, acylation of ketoenamines containing
the orthoꢀsubstituted aryl ring with chiral acid chlorides
afforded a mixture of atropoisomeric diastereomers. This
is evidenced by the doubling of the signals for the methine
proton of the ketoenamine fragment, the proton at the
chiral center of the amino acid residue, and the protons of
the substituents in the ortho position of the Nꢀphenyl
ring (Fig. 2).
CH(4)3
CH(6)3
CH(2)3
H(3)
H(5)
9
8
7
6
5
4
3
2
1
δ
4.82
5.54
5.80
4.89
30.71
5.90 5.23
25.71
10.45
4.46
5.24
14.37 15.85 14.46
1
Fig. 1. H NMR spectrum of compound 1e at 20 °C in deuterobenzene.

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Rybalkin et al.
+
OCH3
OCH3´
CH
C*H+C*H´
CH´
9
8
7
6
5
4
3
2
1
δ
4.00
14.70
4.80
7.27
3.15
2.43
6.20
15.01
13.76
26.57
19.07
4.73
8.00
6.37
1
Fig. 2. H NMR spectrum of compound 1f at 20 °C in CDCl3.
To reveal the structural factors, which hinder the synꢀ
thesis of compounds Zꢀ1, and with the aim of changing
some photochromic properties, we studied compound 1i
by Xꢀray diffraction. The molecular structure of 1i is shown
in Fig. 3. The atoms of the benzothiophene fragment
C(1)C(2)C(3)C(4)C(5)C(6)C(7)C(8)S(1) are in a single
plane (I) (to within 0.01 Å). The N(1) atom is in a planar
configuration (the sum of the angles at this atom is 360°).
O(1)
S(2)
O(2)
C(21)
C(2)
C(4)
C(3)
C(23)
C(1)
C(19)
C(20)
C(9)
C(5)
C(6)
C(22)
O(4)
N(1)
C(8)
C(31)
C(30)
C(16)
C(11)
C(7)
N(2)
C(10)
S(1)
C(18)
C(24)
C(29)
C(28)
C(12)
C(13)
C(15)
C(14)
O(3)
C(25)
C(26)
C(27)
C(17)
Fig. 3. Molecular structure of (2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀdioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ4ꢀmethylthiobutyryl]ꢀNꢀmesitylaminoꢀ
methylidene}benzo[b]thiophenꢀ3(2H )ꢀone (1i).

Chiral photoacylotropic benzo[b]thiophenones
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 12, December, 2005 2787
Table 2. Selected bond lengths (d), bond angles (ω), and torsion angles (τ) in molecule 1i
Bond
d/Å
Angle
ω/deg
Bond angle
ω/deg
S(1)—C(1)
S(1)—C(8)
1.758(2)
1.760(2)
1.781(3)
1.800(2)
1.378(3)
1.453(2)
1.393(3)
1.211(2)
1.459(3)
1.334(3)
1.496(3)
1.201(3)
1.450(3)
1.408(3)
1.204(2)
1.208(3)
1.499(3)
1.529(3)
C(1)—S(1)—C(8)
C(9)—N(1)—C(19)
C(9)—N(1)—C(10)
C(19)—N(1)—C(10)
C(9)—C(1)—C(2)
C(9)—C(1)—S(1)
C(2)—C(1)—S(1)
O(1)—C(2)—C(3)
O(1)—C(2)—C(1)
C(3)—C(2)—C(1)
C(8)—C(3)—C(2)
C(3)—C(8)—S(1)
C(1)—C(9)—N(1)
C(15)—C(10)—N(1)
O(2)—C(19)—N(1)
O(2)—C(19)—C(20)
N(1)—C(19)—C(20)
N(2)—C(20)—C(21)
N(2)—C(20)—C(19)
91.2(1)
116.8(2)
120.1(2)
123.1(2)
119.2(2)
129.0(2)
111.8(2)
126.0(2)
124.7(2)
109.3(2)
113.6(2)
113.9(2)
129.0(2)
118.3(2)
120.5(2)
121.6(2)
117.8(2)
112.7(2)
111.7(2)
C(22)—C(21)—(20)
C(21)—C(22)—S(2)
O(3)—C(24)—N(2)
113.2(2)
108.6(2)
124.4(2)
S(2)—C(23)
S(2)—C(22)
N(1)—C(9)
N(1)—C(10)
N(1)—C(19)
O(1)—C(2)
C(2)—C(3)
C(1)—C(9)
C(1)—C(2)
O(2)—C(19)
N(2)—C(20)
N(2)—C(24)
O(3)—C(24)
O(4)—C(31)
C(11)—C(16)
C(19)—C(20)
Torsion angle
τ/deg
174.5(2)
5.5(3)
–176.3(2)
–101.1(2)
76.8(3)
С(8)—S(1)—C(1)—C(9)
C(9)—C(1)—C(2)—O(1)
S(1)—C(1)—C(2)—O(1)
C(9)—N(1)—C(10)—C(11)
C(19)—N(1)—C(10)—C(11)
N(1)—C(10)—C(11)—C(16)
C(9)—N(1)—C(19)—O(2)
C(10)—N(1)—C(19)—O(2)
C(9)—N(1)—C(19)—C(20)
C(24)—N(2)—C(20)—C(19)
C(19)—C(20)—C(21)—C(22)
C(20)—C(21)—C(22)—S(2)
C(23)—S(2)—C(22)—C(21)
C(31)—N(2)—C(24)—C(25)
1.3(3)
4.7(4)
–173.3(2)
–177.9(2)
–125.2(2)
167.3(2)
177.2(2)
–171.3(2)
–2.0(2)
The N(1)—C(9) and N(1)—C(19) distances are 1.378(3)
and 1.393(3) Å, respectively, and the N(1)—C(10) disꢀ
tance is 1.453(2) Å.
O(2)—C(19) bond, which is indicative of a uniform disꢀ
tribution of the amide conjugation over two oxygen atoms
in the plane III. By contrast, the N(1) atom is involved
not only in the amide conjugation with the O(2) atom but
also in conjugation with the C(1)=C(9) πꢀbond. In single
crystals, the molecules do not form intermolecular hydroꢀ
gen bonds.
To summarize, irradiation of solutions of
(2Z )ꢀ2ꢀ(NꢀacylꢀNꢀarylaminomethylidene)benzo[b]thioꢀ
phenꢀ3(2H )ꢀones, which are Lꢀamino acid derivatives,
causes migration of the acyl group containing the asymꢀ
metric carbon atom due to the photoinduced acylotropic
rearrangement N → O. An increase in the volume of the
substituent in the acyl fragment compared to acetyl deꢀ
rivatives studied earlier1 in going to amino acid derivaꢀ
tives containing the phthalimide protecting group leads to
an increase in steric strain in Nꢀacyl derivative Zꢀ1 and
destabilization of this isomer, which can be responsible
for irreversibility of the photorearrangement.
The carbon atoms of the mesityl fragment from C(10)
to C(18) are in a single plane (II) (to within 0.02 Å). This
fragment is twisted about the N(1)—C(10) bond relaꢀ
tive to the plane of the C(9)N(1)C(19) atoms. The
C(9)N(1)C(10)C(11) torsion angle is 78.9(2)°. This muꢀ
tual arrangement of the fragments is attributed to an inꢀ
crease in steric strain, as evidenced by the shortened inꢀ
tramolecular C(10)—S(1), C(11)—S(1), and C(15)—S(1)
distances (3.037(5), 3.275(5), and 3.394(5) Å, respecꢀ
tively), resulting in the nearly perpendicular arrangement
of the planes I and II.
The
torsion
angles
in
the
C(9)N(1)C(19)C(20)C(21)S(2)C(23) chain are given in
Table 2 and characterize the orientation of the chain fragꢀ
ment of the molecule relative to the planes I and II.
The plane of the phthalimide fragment involving the
atoms from C(20) to C(31)O(3)O(4) (III) is nearly paralꢀ
lel to the plane II. The formal angle between these planes
is 15°, the C(10)—N(1)—C(20)—N(2) pseudotorsion
angle is 60.1(1)°, and the shortest distance between the
atoms of the planes II and III in the molecule (C(15) and
C(24)) is 3.249(5) Å.
A comparison of the O(1)—C(2), O(2)—C(19),
O(3)—C(24), and O(4)—C(31) distances (1.211(2),
1.201(3), 1.204(2), and 1.208(3) Å, respectively) shows
that there is conjugation between the πꢀorbitals of the
O(1)—C(2) and C(1)—C(9) bonds and the amide conjuꢀ
gation in the N(1)C(19)O(2), N(2)C(24)O(3), and
N(2)C(31)O(4) fragments. In the latter two fragments,
the C=O bonds are equally elongated compared to the
Experimental
Electronic absorption spectra of compounds 1a—i and
2c,j—m were measured on a Specord Mꢀ40 spectrophotometer.
The solutions were irradiated using a DRShꢀ250 mercury lamp
equipped with a kit of glass light filters. The quantum yields in
toluene were determined using potassium ferrioxalate.7 The IR
spectra were recorded on a Specord IRꢀ75 instrument in Nujol
mulls. The 1H NMR spectra were measured on a Varian
Unityꢀ300 instrument (300 MHz) in CDCl3 with Me4Si as the
internal standard.
Phthaloylamino acids were synthesized according to a proꢀ
cedure described earlier8 from phthalic anhydride and the corꢀ

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Rybalkin et al.
responding amino acid in the presence of triethylamine and then
recrystallized from aqueous ethanol.
Phthaloylamino acid chlorides were synthesized according
to a known procedure9 from the corresponding acids and thionyl
chloride in anhydrous benzene.
Synthesis of aminovinyl ketones 3 (general procedure).
Equimolar amounts of 2ꢀhydroxybenzo[b]thiopheneꢀ2ꢀcarbꢀ
aldehyde and the corresponding substituted aniline were conꢀ
densed in acetonitrile followed by crystallization.10
Synthesis of compounds 1a—i and 2c,j—m (general proceꢀ
dure). Triethylamine (1.72 g, 0.017 mol) was added to a solution
of aminovinyl ketone 3 (0.015 mol) in a minimum amount of
anhydrous acetonitrile at 60 °C. NꢀPhthaloylamino acid chloꢀ
ride (0.017 mol) was added to this mixture. The reaction prodꢀ
uct was filtered off, washed with methanol, and recrystallized.
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)proꢀ
panoyloxy]ꢀNꢀ(2ꢀmethoxyphenyl)aminomethylidene}benꢀ
zo[b]thiophenꢀ3(2H )ꢀone (1a). The yield was 38%, m.p. 265 °C
(from acetonitrile). Found (%): C, 66.90; H, 4.15; N, 5.75.
C27H20N2O5S. Calculated (%): C, 66.93; H, 4.16; N, 5.78. IR,
ν/cm–1: 1775, 1725, 1670. 1H NMR, δ, diastereomer A: 8.93 (s,
1 H, CH); 7.84—6.53 (m, 12 H, Ar); 4.91 (q, 1 H, CH, J =
7.1 Hz); 3.93 (s, 3 H, OMe); 1.58 (d, 3 H, Me, J = 7.1 Hz);
diastereomer B: 8.87 (br.s, 1 H, CH); 7.84—6.53 (m, 12 H, Ar);
5.02 (br.q, 1 H, J = 6.9 Hz); 3.02 (br.s, 3 H, OMe); 1.59 (d, 3 H,
Me, J = 6.9 Hz). The isomer ratio A : B = 8 : 7.
toluene). Found (%): C, 71.55; H, 5.58; N, 5.13. C32H30N2O4S.
Calculated (%): C, 71.35; H, 5.61; N, 5.20. IR, ν/cm–1: 1750,
1720, 1675. 1H NMR, δ: 9.08 (s, 1 H, CH); 7.88—7.14 (m, 8 H,
Ar); 7.12 and 6.57 (both br.s, 1 H, CH, Mes); 4.25 (d, 1 H, CH,
J = 10.5 Hz); 2.80—2.60 (m, 1 H, CH); 2.36, 2.24, and 1.50
(all s, 3 H each, Me); 1.20—0.75 (m, 8 H, CH2, 2 Me).
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ4ꢀ
methylpentanoyl]ꢀNꢀ(2ꢀmethoxyphenyl)aminomethylidene}benꢀ
zo[b]thiophenꢀ3(2H )ꢀone (1f). The yield was 24%, m.p. 245 °C
(from toluene). Found (%): C, 68.36; H, 5.02; N, 5.30.
C30H26N2O5S. Calculated (%): C, 68.42; H, 4.98; N, 5.32. IR,
1
ν/cm–1: 1760, 1705, 1685, 1650. H NMR, δ, diastereomer A:
8.90 (s, 1 H, CH); 7.86—6.68 (m, 12 H, Ar); 5.05—4.90 (m,
1 H, CH); 3.90 (s, 3 H, OMe); 2.40—1.80 (m, 2 H, CH2);
1.50—1.25 (m, 1 H, CH); 0.90—0.80 and 0.75—0.65 (both m,
3 H each, Me); diastereomer B: 8.87 (br.s, 1 H, CH); 7.86—6.70
(m, 12 H, Ar); 5.05—4.90 (m, 1 H, CH); 3.24 (br.s, 3 H, OMe);
2.40—1.80 (m, 2 H, CH2); 1.50—1.25 (m, 1 H, CH); 0.90—0.80
and 0.75—0.65 (both m, 3 H each, Me). The isomer ratio
A : B = 7 : 8.
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ4ꢀ
methylthiobutyryl]ꢀNꢀ(2ꢀmethoxyphenyl)aminomethylidene}benꢀ
zo[b]thiophenꢀ3(2H )ꢀone (1g). The yield was 35%, m.p.
228—229 °C (from a butanol—DMF mixture). Found (%):
C, 63.87; H, 4.5; N, 5.16. C29H24N2O5S2. Calculated (%):
C, 63.95; H, 4.44; N, 5.14. IR, ν/cm–1: 1750, 1720, 1600.
1H NMR, δ, diastereomer A: 8.62 (s, 1 H, CH); 7.84—6.60 (m,
12 H, Ar); 5.00—4.90 (m, 1 H, CH); 3.95 and 1.98 (both s,
3 H each, Me); 2.50—2.00 (m, 4 H, 2 CH2); diastereomer B:
8.58 (br.s, 1 H, CH); 7.84—6.60 (m, 12 H, Ar); 5.07—5.00 (m,
1 H, CH); 2.91 (br.s, 3 H, OMe); 2.50—2.00 (m, 4 H, 2 CH2);
1.97 (s, 3 H, Me). The isomer ratio A : B = 1 : 2.
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)proꢀ
panoyloxy]ꢀNꢀ(2ꢀbromophenyl)aminomethylidene}benzo[b]thioꢀ
phenꢀ3(2H )ꢀone (1b). The yield was 20%, m.p. 202—203 °C
(from acetonitrile). Found (%): C, 58.56; H, 3.15; N, 5.29.
C
26H17BrN2O4S. Calculated (%): C, 58.55; H, 3.21; N, 5.25.
IR, ν/cm–1: 1775, 1750, 1730, 1680. 1H NMR, δ, diastereoꢀ
mer A: 8.96 (br.s, 1 H, CH); 7.86—6.96 (m, 12 H, Ar); 5.15—4.90
(br.s, 1 H, CH); 1.8—1.6 (br.s, 3 H, Me); diastereomer B: 8.90
(br.s, 1 H, CH); 7.86—6.96 (m, 12 H, Ar); 4.93 (br.q, 1 H, CH,
J = 6.9 Hz); 1.62 (d, 3 H, Me, J = 6.9 Hz). The isomer ratio
A : B = 1 : 3.
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ
4ꢀmethylthiobutyryl]ꢀNꢀ(4ꢀiodophenyl)aminomethylidene}benꢀ
zo[b]thiophenꢀ3(2H )ꢀone (1h). The yield was 21%, m.p.
216—217 °C (from an acetonitrile—toluene mixture).
Found (%): C, 52.49; H, 3.32; N, 4.35. C28H21IN2O4S2. Calcuꢀ
lated (%): C, 52.51; H, 3.30; N, 4.37. IR, ν/cm–1: 1775, 1710,
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)proꢀ
panoyloxy]ꢀNꢀ(4ꢀiodophenyl)aminomethylidene}benzo[b]thioꢀ
phenꢀ3(2H )ꢀone (1c). The yield was 7.6%, m.p. 293 °C (from an
acetonitrile—toluene mixture). Found (%): C, 53.93; H, 2.90;
N, 4.82. C26H17IN2O4S. Calculated (%): C, 53.81; H, 2.95;
N, 4.83. IR, ν/cm–1: 1710, 1675, 1590. 1H NMR, δ: 8.74
(br.s, 1 H, CH); 7.84—6.96 (m, 10 H, Ar); 7.05—6.88 (br.s,
2 H, Ar); 5.06 (br.q, 1 H, CH, J = 7.0 Hz); 1.63 (d, 3 H, Me,
J = 7.0 Hz).
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ3ꢀ
methylpentanoyl]ꢀNꢀ(2ꢀmethoxyphenyl)aminomethylidene}benꢀ
zo[b]thiophenꢀ3(2H )ꢀone (1d). The yield was 36%, m.p. 195 °C
(from acetonitrile). Found (%): C, 68.38; H, 5.02; N, 5.28.
C30H26N2O5S. Calculated (%): C, 68.42; H, 4.98; N, 5.32. IR,
ν/cm–1: 1760, 1720, 1675. 1H NMR, δ, diastereomer A: 8.95 (s,
1 H, CH); 7.85—6.38 (m, 12 H, Ar); 4.63—4.40 (m, 1 H, CH);
3.94 (s, 3 H, OMe); 2.76—2.45 (m, 1 H, CH); 1.8—0.60 (m,
2 H, 6 H, CH2, 2 Me); diastereomer B: 8.93 (br.s, 1 H, CH);
7.85—6.38 (m, 12 H, Ar); 4.63—4.40 (m, 1 H, CH); 2.85 (br.s,
3 H, OMe); 2.76—2.45 (m, 1 H, CH); 1.8—0.60 (m, 2 H, 6 H,
CH2, 2 Me). The isomer ratio A : B = 5 : 6.
1
1655. H NMR, δ: 8.70 (br.s, 1 H, CH); 7.84—6.80 (m, 12 H,
Ar); 5.25 (br.t, 1 H, CH); 2.60—2.34 (m, 4 H, 2 CH2); 1.98
(s, 3 H, Me).
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ4ꢀ
methylthiobutyryl]ꢀNꢀmesitylaminomethylidene}benzo[b]thioꢀ
phenꢀ3(2H )ꢀone (1i). The yield was 22%, m.p. 183—184 °C
(from acetonitrile). Found (%): C, 66.79; H, 4.97; N, 5.01.
C31H28N2O4S2. Calculated (%): C, 66.88; H, 5.07; N, 5.03. IR,
ν/cm–1: 1775, 1720, 1670. 1H NMR, δ: 8.98 (s, 1 H, CH);
7.85—7.13 (m, 8 H, Ar); 7.08 and 6.76 (both br.s, 1 H each,
Mes); 5.03—4.95 (m, 1 H, CH); 2.55—2.20 (m, 4 H, 2 CH2);
2.38, 1.88, and 1.87 (all s, 3 H each, Me); 2.22 (br.s, 3 H, Me).
3ꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀpropanoylꢀ
oxy]ꢀ2ꢀ(4ꢀiodophenyl)iminomethylbenzo[b]thiophene (2c). The
yield was 57%, m.p. 189—191 °C (from a acetonitrile—butanol
mixture). Found (%): C, 53.83; H, 2.90; N, 4.82. C26H17IN2O4S.
Calculated (%): C, 53.81; H, 2.95; N, 4.83. IR, ν/cm–1: 1780,
1770, 1710. 1H NMR, δ: 8.66 (s, 1 H, CH); 7.94—7.16 (m,
12 H, Ar); 5.40 (q, 1 H, CH, J = 7.2 Hz); 1.87 (d, 3 H, Me,
J = 7.2 Hz).
(2Z )ꢀ2ꢀ{Nꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ3ꢀ
methylpentanoyl]ꢀNꢀmesitylaminomethylidene}benzo[b]thiophenꢀ
3(2H )ꢀone (1e). The yield was 40%, m.p. 275—276 °C (from
3ꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀpropanoylꢀ
oxy]ꢀ2ꢀ(2ꢀmethylphenyl)iminomethylbenzo[b]thiophene (2j). The
yield was 37%, m.p. 165 °C (from toluene). Found (%): C, 69.20;

Chiral photoacylotropic benzo[b]thiophenones
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 12, December, 2005 2789
H, 4.28; N, 5.99. C27H20N2O4S. Calculated (%): C, 69.22;
H, 4.30; N, 5.98. IR, ν/cm–1: 1780, 1760, 1710. 1H NMR, δ:
8.55 (s, 1 H, CH); 7.94—7.14 (m, 12 H, Ar); 5.39 (q, 1 H, CH,
J = 7.25 Hz); 2.27 (s, 3 H, Me).
3ꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)propanoylꢀ
oxy]ꢀ2ꢀ(2ꢀnitrophenyl)iminomethylbenzo[b]thiophene (2k). The
yield was 69%, m.p. 203 °C (from toluene). Found (%): C, 62.50;
H, 3.40; N, 8.39. C26H17N3O6S. Calculated (%): C, 62.52;
H, 3.43; N, 8.41. IR, ν/cm–1: 1780, 1710, 1620. 1H NMR, δ:
8.62 (s, 1 H, CH); 8.00—7.18 (m, 12 H, Ar); 5.40 (q, 1 H, CH,
J = 7.25 Hz); 1.87 (d, 3 H, Me, J = 7.25 Hz).
3ꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)propanoylꢀ
oxy]ꢀ2ꢀ(naphthꢀ1ꢀyl)iminomethylbenzo[b]thiophene (2l). The
yield was 35%, m.p. 211 °C (from a butanol—DMF mixture).
Found (%): C, 71.39; H, 4.01; N, 5.54. C30H20N2O4S. Calcuꢀ
lated (%): C, 71.41; H, 4.00; N, 5.55. IR, ν/cm–1: 1778, 1705.
1H NMR, δ: 8.73 (s, 1 H, CH); 8.42—7.18 (m, 15 H, Ar); 5.38
(q, 1 H, CH); 1.85 (d, 3 H, Me, J = 7.25 Hz).
3ꢀ[(S)ꢀ2ꢀ(1,3ꢀDioxoꢀ1,3ꢀdihydroisoindolꢀ2ꢀyl)ꢀ4ꢀmethylꢀ
thiobutyryloxy]ꢀ2ꢀ(naphthꢀ1ꢀyl)iminomethylbenzo[b]thiophene
(2m). The yield was 20%, m.p. 199—200 °C (from a buꢀ
tanol—DMF). Found (%): C, 68.10; H, 4.26; N, 4.92.
C32H24N2O4S2. Calculated (%): C, 68.07; H, 4.28; N, 4.96. IR,
ν/cm–1: 1775, 1750, 1705. 1H NMR, δ: 8.72 (s, 1 H, CH);
8.42—7.19 (m, 15 H, Ar); 5.60—5.50 (m, 1 H, CH); 2.80—2.50
(m, 4 H, 2 CH2); 2.10 (s, 3 H, Me).
The results of Xꢀray diffraction study, including the atomic
coordinates and displacement parameters, were deposited with
the Cambridge Structural Database.
This study was financially supported by the US Civilꢀ
ian Research and Development Foundation (CRDF)—the
Ministry of Education and Science of the Russian Fedꢀ
eration (Grant ROꢀ004ꢀX1), the Council on Grants of
the President of the Russian Federation (Program for
State Support of Leading Scientific Schools of the Rusꢀ
sian Federation, Grant NShꢀ945.2003.3), the Program
for Basic Research of the Division of Chemistry and Maꢀ
terials Science of the Russian Academy of Sciences "Theoꢀ
retical and Experimental Studies of the Nature of Chemiꢀ
cal Bonds and Mechanisms of Important Chemical Reꢀ
actions and Processes," and the Program for Support of
Research of PostꢀGraduate Students of the Ministry of
Education and Science of the Russian Federation (Grant
40/21ꢀ629).
References
1. A. E. Lyubarskaya, G. D. Palui, V. A. Bren´, Yu. A. Zhdanov,
M. I. Knyazhanskii, V. I. Minkin, and L. P. Olekhnovich,
Zh. Org. Khim., 1976, 12, 918 [J. Org. Chem. USSR, 1976, 12
(Engl. Transl.)].
2. V. A. Bren´, A. D. Dubonosov, O. G. Karamov, N. I.
Makarova, V. I. Minkin, L. L. Popova, V. P. Rybalkin,
N. N. Tkalina, A. V. Tsukanov, and E. N. Shepelenko,
Zh. Org. Khim., 2002, 38, 1755 [Russ. J. Org. Chem., 2002,
38, 1698 (Engl. Transl.)].
3. V. P. Rybalkin, L. L. Popova, A. D. Dubonosov, E. N.
Shepelenko, Yu. V. Revinskii, V. A. Bren´, and V. I. Minkin,
Zh. Org. Khim., 2001, 37, 1384 [Russ. J. Org. Chem., 2001, 37
(Engl. Transl.)].
4. A. D. Dubonosov, V. I. Minkin, V. A. Bren, L. L. Popova,
V. P. Rybalkin, E. N. Shepelenko, N. N. Tkalina, and A. V.
Compounds 2a—i were prepared by light irradiation of soluꢀ
tions of compounds 1a—i at λexc = 436 nm in a 10ꢀmm spectroꢀ
photometric cell. The structures of compounds 2a,b,d,i were
proposed based on similarity of their electronic absorption specꢀ
tra with the spectra of compounds 2c,j—m.
Xꢀray diffraction study of compound 1i. The unit cell paramꢀ
eters and a threeꢀdimensional Xꢀray diffraction data set were
obtained on an automated fourꢀcircle KUMA diffractometer
(MoꢀKα radiation, graphite monochromator). Paleꢀyellow transꢀ
parent crystals 1i are monoclinic, space group P21/c. The moꢀ
lecular formula is C31H28N2O4S2, M 556.67, a = 11.469(4) Å,
b = 18.686(6) Å, c = 14.289(5) Å, β = 112.71(4)°, V =
2824.9(17) Å3, Z = 4, ρ
= 1.678 g cm–3, µ(MoꢀKα) =
calc
0.228 mm–1
.
Tsukanov, Ach. Org. Chem. (ARKIVOC), 2003, 13, 12.
5. B. L. Feringa, Chem. Rev., 2000, 5, 1789.
The intensities of 5397 reflections were measured in the
angle range 2θ < 50.1° using the ω/2θꢀscanning technique from
a single crystal of dimensions 0.32×0.27×0.31 mm. After excluꢀ
sion of systematic absences and merging of the intensities of
equivalent reflections, the data set of measured F 2(hkl) and
σ(F 2) contained 5218 independent reflections, of which 5003 reꢀ
flections with F 2 > 4σ(F 2) were used in subsequent calculations.
The structure was solved by direct methods and refined by
the fullꢀmatrix leastꢀsquares method against F 2 using the
SHELXLꢀ97 program package11 with anisotropic displacement
parameters for nonhydrogen atoms. Most H atoms were located
from difference Fourier maps (the positions of the H atoms at
the C(17) and C(23) atoms were calculated geometrically) and
were refined isotropically. In the final steps, the intensities of
reflections were corrected for absorption by a semiempirical
method and then refined by the leastꢀsquares method with the
fixed atomic coordinates and thermal parameters of the H atoms.
The final data obtained in the refinement of 352 parameters
were as follows: R1 = 0.041 for 5003 observed reflections with
I > 2σ(i); R1 = 0.074 based on all 5218 measured reflections,
Goof 1.08.11,12
6. V. P. Rybalkin, E. N. Shepelenko, Ya. Yu. Vorob´eva, G. S.
Borodkin, V. A. Bren´, V. I. Minkin, S. M. Aldoshin, V. V.
Tkachev, and A. N. Utenyshev, Izv. Akad. Nauk, Ser. Khim.,
2003, 1706 [Russ. Chem. Bull., Int. Ed., 2003, 52, 1800].
7. C. A. Parker, Photoꢀluminescence of Solutions, Elsevier Pubꢀ
lishing Company, Amsterdam—London—New York, 1968.
8. L. F. Fieser and M. Fieser, Reagents for Organic Synthesis,
John Wiley and Sons, New York—London—Sydney, 1968.
9. Organikum, Organischꢀchemisches Grundpraktikum, VEB
Deutscher Verlag der Wissenschaften, Berlin, 1976.
10. V. A. Bren´, V. I. Usacheva, and V. I. Minkin, Khim.
Geterotsikl. Soedin., 1972, 920 [Chem. Heterocycl. Compd.,
1972 (Engl. Transl.)].
11. G. M. Sheldrick, SHELXꢀ97, University of Göttingen,
Göttingen (Germany), 1997.
12. A. C. T. North, D. C. Phillips, and F. S. Mathews, Acta
Crystallogr., Sect. A, 1968, 24, 351.
Received April 18, 2005;
in revised form December 21, 2005