Photo- and thermochromic spirans 37.*New symmetrical bisspiropyrans of the indoline series

Article abstract of DOI:10.1007/s10593-012-1145-5

New symmetrical bisspiropyrans of the indoline series, which have photochromic properties and are characterized by substantially higher absorption capacity of cyclic isomers in comparison to the monospiropyrans, were obtained on the basis of 4,6-dihydroxy

Full text of DOI:10.1007/s10593-012-1145-5

Chemistry of Heterocyclic Compounds, Vol. 48, No. 9, December, 2012 (Russian Original Vol. 48, No. 9, September, 2012)
PHOTO- AND THERMOCHROMIC SPIRANS
37.* NEW SYMMETRICAL BISSPIROPYRANS
OF THE INDOLINE SERIES
1
2
1
N. A. Voloshin , E. V. Solov'eva , S. O. Bezugliy ,
2
1,2
A. V. Metelitsa **, and V. I. Minkin
New symmetrical bisspiropyrans of the indoline series, which have photochromic properties and are
characterized by substantially higher absorption capacity of cyclic isomers in comparison to the
monospiropyrans, were obtained on the basis of 4,6-dihydroxy-5-methylisophthalaldehyde.
Keywords: 4,6-dihydroxy-5-methylisophthalaldehyde, merocyanine, spiropyran, absorption spectra, molar
extinction coefficient, photochromism.
The design and investigation of new effective photochromic systems with the aim of producing
multifunctional materials for molecular electronics are problems of current interest [2-6]. Spiropyrans and
spirooxazines are widely known types of organic photochromes [2-4]. The possibility of targeted alteration their
spectral-kinetic characteristics over a wide range by varying their structure has aroused the interest of
researchers in these compounds [2-6].
A highly important and frequently discussed characteristic of photochromes is the quantum yield of
photocoloration. However, a parameter of no lesser importance is the molar extinction coefficient (ε, MEC) of
the isomeric forms of a photochromic system that are mutually transformed during exposure to actinic light. It
characterizes the absorptive capacity of the substance or, essentially, the probability that a quantum of light is
absorbed by the molecule. It is clear that the higher the value of this coefficient at a fixed level of intensity of
the incident light, the larger the number of molecules that can transit to the excited state and isomerize to the
photoreaction products with a characteristic quantum yield for the given system.
It is known that the products from the phototransformation of spiropyrans and spirooxazines (the
merocyanine isomers) have the highest values of the MEC among photochromic compounds, reaching
-
1
-1
4
0000-120000 l·mol ·cm . This makes it possible to observe a distinct optical response even when the
conversion degree of the cyclic isomers into the merocyanine isomers is small. At the same time, the initial
cyclic forms usually have low MEC values, and this is one of the reasons for the low degree of transformation
_
*
*
______
For Communication 36, see [1].
*To whom correspondence should be addressed, e-mail: photo@ipoc.rsu.ru.
1
Southern Scientific Center, Russian Academy of Sciences, 41 Chekhov Ave., Rostov-on-the-Don 344006,
Russia; e-mail: ssc-ras@ssc-ras.ru.
2
Research Institute of Physical and Organic Chemistry, Southern Federal University, 194/2 Stachki Ave.,
Rostov-on-the-Don 344090, Russia.
_
________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1460-1470, September, 2012.
Original article submitted July 5, 2011; revision submitted January 29, 2012.
009-3122/12/4809-1361©2012 Springer Science+Business Media New York
0
1361

to the colored products. Thus, for example, in toluene the 6-methyl-substituted spirobenzopyranindoline [7] has
-1
-1
a molar extinction coefficient of 6270 l·mol ·cm at the maximum of the long-wave absorption band at 297 nm.
Structural modifications directed at increasing the MEC of the cyclic isomeric forms of spirocyclic compounds
are therefore of interest from both theoretical and practical points of view.
One possible way of increasing the MEC involves raising spatial size of the molecular system.
However, such modification must not lead to a decrease in the quantum yields of photocoloration on account of
the increased effectiveness of nonradiative or secondary photochemical processes. A possible solution of the
problem is to produce structures that link two molecules of the spiro compound in such a way as to exclude or
restrict the possibility of simultaneous opening of the two rings. Such a condition is met in the structure of
symmetrical bisspiropyrans with the general formula 1.
Me
N
Me
Me
Me
1
R
1
O
O
R
N
Me
R
R
1
A
h h,
Me
Me
1
R
Me Me
1
R
N
O
R
N
R
O
Me
1
B
The present work concerns the synthesis of new symmetrical indoline bisspiropyrans of type 1 and
description of their spectral and photochromic properties.
The symmetrical bisspiropyrans 1a-f were obtained in a single stage by the reaction of two equivalents
of the 3H-indolium salts 2a-f with 4,6-dihydroxy-5-methylisophthalaldehyde (3) in the presence of
triethylamine as a base.
Me
Me
Me
1
R
HO
OH
Me
–
Et N
3
+
+
N

I
OHC
CHO
Me
R
2
a–f
3
4
'
5'
6'
Me
Me
Me
4
2'
4''
3
10'
2
''
1
1
O
O
R
R
N
1'
9' N1''
1
Me
R
R
7
''
7
1
a–f
1
1
a–d R = H, a R = Me, b R = All, c R = i-Bu, d R = Pr; e, f R = OMe, e R = Pr, f R = Me
A method for the synthesis of the isophthalaldehyde 3 with an overall yield of 51%, involving
bromination of 2,6-dimethoxytoluene, treatment of the obtained dibromo derivative with an excess of
butyllithium and dimethyl formamide, and subsequent demethylation with aluminum chloride in nitrobenzene,
was described earlier [8]. We propose a simple single-stage method for the preparation of this aldehyde with a
5
8% yield by Duff formylation of 2-methylresorcinol (4).
1
362

Me
Me
HO
OH
HO
OH
+
N (CH ) + CF COOH
4 2 6 3
OHC
CHO
4
3
The compositions of each of the obtained products 1a-f were supported by the results of elemental
1
analysis, and the structure was supported by the H NMR spectra (see Experimental).
1
In the upfield region, the H NMR spectra of the bisspiropyrans 1a-f contain signals for the protons of
the magnetically non-equivalent geminal methyl groups, the N-alkyl substituents (Me, All, Pr, i-Bu), and the
respective Me and OMe substituents of the pyran and also the indoline fragments. In the downfield region there
are signals for the ring protons of the above-mentioned fragments.
1
The distinctive features of the H NMR spectra of compounds 1a-f arise from the presence of the two
asymmetric spiro carbon atoms in their molecules. The spiropyrans, in which the two heterocyclic fragments are
linked by a stereogenic tetrahedral carbon atom, exist in the form of two (R) and (S) enantiomers that can
usually be separated by high-resolution liquid chromatography with chiral sorbents [9-12]. In the molecules of
the bisspiropyrans 1a-f the presence of the second asymmetric spiro carbon atom increases the number of
stereoisomers to four: the (R,R), (S,S), (R,S), and (S,R) enantiomers. Since the above-mentioned bisspiropyrans
contain two identical indoline fragments, the (R,S) and (S,R) stereoisomers have a plane of symmetry and
represent a meso form.
The different stereochemical structures of the pair of (R,R) and (S,S) enantiomers and of the meso form
of the compounds under investigation show up in different values for the chemical shifts of the signals for the
protons of the substituents and of certain ring protons, and this is particularly noticeable in the case of bulky
1
N-alkyl substituents. Thus, in the H NMR spectra of compounds 1a,b,d,e, the signals for the protons of the
gem-dimethyl groups represent a six-proton singlet and two three-proton singlets, in the spectrum of compound
1
c there are four three-proton singlets, while in the spectrum of compound 1f there are two six-proton singlets.
The prochirality of the methylene protons in the N- and N"-allyl substituents (compound 1b) and the methyl
protons in the N- and N"-isobutyl substituents (compound 1c) leads to diastereotopic splitting in the signals of
these groups.
As known, in the spectra of N-allyl-substituted spiropyrans, the signals of the diastereotopic protons of
the methylene group take the form of two triplets of doublets of doublets, while those of the terminal CH group
2
are two quartets of doublets [13, 14] (Fig. 1a). In the case of the N,N"-diallyl-substituted bisspiropyran 1b, the
signals of the diastereotopic protons of the CH groups take the form of two two-proton multiplets in the regions
2
of 3.56-3.66 and 3.84-3.95 ppm, each of which represents the superimposition of the triplet of doublets of
doublets of the (R,R) and (S,S) enantiomers and the meso form. The signals for the cis protons of the terminal
CH groups in the stereoisomers are represented by two quartets of doublets at 5.02 and 5.04 ppm, while those
2
of the trans protons are a quartet of doublets in the regions of 5.14 and 5.17 ppm. The two-proton multiplet of
the CH group in the allyl substituents lies in the region of 5.77-5.90 ppm (Fig. 1b).
The signals for the diastereotopic protons of the methyl and methylene groups in the N-isobutyl
substituent of the spiropyrans appear in the form of two doublets and two double doublets, respectively [13, 14].
The signals for the analogous protons of the N- and N"-isobutyl substituents of the bisspiropyran 1c have the
form of four three-proton doublets in the region of 0.88-0.91 ppm (the methyl groups) and a four-proton
multiplet in the region of 2.85-2.88 ppm, which represent the superposition of the two double doublets of the
pair of (R,R) and (S,S) enantiomers and the meso form (the methylene groups). The signals for the protons of the
CH groups have the form of a two-proton multiplet in the region of 1.92-2.04 ppm.
The protons of the indoline fragments in the (R,R) and (S,S) enantiomers and of the meso form in
compounds 1a-f (H-4,4", H-5,5", H-6,6", and H-7,7") appear in the form of two-proton signals with the
appropriate multiplicity, while the signals for the protons of the pyran fragments (H-3',7' and H-4',6') appear in
the form of either a two-proton doublet or of two one-proton doublets.
1
363

1
Fig. 1. The signals of the allyl group protons in the H NMR spectra of the N-allyl-substituted spiropyran (a)
[14] and the bisspiropyran 1b (b) in CDCl3.
The absence of signals for the protons of the N-alkyl and gem-dimethyl groups and also of other protons
of the indoline and pyran fragments in the regions of the spectrum characteristic of the open planar merocyanine
form [15-17] and the different chemical shift values of the signals for the protons of the gem-dimethyl groups,
the N- and N"-alkyl substituents, and certain bisspiropyran ring protons indicate that the obtained compounds in
CDCl solution are present in the spirocyclic form as a mixture of the (R,R) and (S,S) enantiomers, and the meso
3
form.
In the electronic absorption spectra (EAS) of the cyclic forms of compounds 1a-f it is possible to single out
three regions where the absorption maxima are located: at 256-257 (ε 51470-57220), 290-315 (ε 13040-17560),
-
1
-1
and 340-344 nm (ε 6010-7510 l·mol ·cm ).
Comparison of the EAS of the bisspiropyran 1a and its model mono analog, the 6-methyl-substituted
spirobenzopyranindoline 5 (Table 1, Fig. 2) shows that the structure of the long-wave part for these compounds
is identical, and the only difference lies in the different degrees of manifestation of the bands (in the form of a
maximum or of a shoulder). Thus, the maximum of the absorption band in the spectrum of the model spiropyran
5
in toluene at 297 nm corresponds to a shoulder at 294 nm in the spectrum of the bisspiropyran 1a; conversely,
the two vibrational maxima at 326 and 343 nm in the spectrum of the latter correspond to two shoulders at 318
and 332 nm in the spectrum of the spiropyran 5. The important expected difference is due to the different
absorption band intensities in the spectra of compounds 5 and 1a-f; the MEC of the bisspiropyrans is 2-3 times
greater than in the model spiropyran 5.
The solvent effect on the EAS of bisspiropyrans shows up as a small hypsochromic shift in the
absorption band maxima with increase in the solvent polarity; for example, in the transition from toluene to
acetonitrile these maxima are shifted by 2 nm towards the short-wave region (Table 1).
1
364

TABLE 1. The Spectral and Kinetic Characteristics of Compounds 1a-f, 5
Toluene, 263 K
Acetonitrile, 293 K
Form А Form В
Com-
pound
Form А
Form В
ε,
τ
263 (B),
s
λ
nm
max
,
ε,
λ
nm
max
,
τ293 (B),
λ
max, nm
-1
-1
λmax, nm
-1
-1
l·mol ·cm
l·mol ·cm
s
1
1
1
1
a
b
c
294 sh
18150
6610
6010
450
553
591
21.6
257
51470
45710
17070
6520
6100
—
442
5.8
3
3
26
43
266 sh
290 sh
324
545 sh
586
6
40 sh
630 sh
3
40
327
43
6990
6420
450
554
24.3
41.4
29.4
258
443
15.9
5.1
3
267 sh
293 sh
325
546 sh
587
5
6
92
45 sh
633 sh
3
41
293
17770
7480
6670
451
555
594
257
—
—
442
3
3
27 sh
43
266 sh
294 sh
325 sh
545 sh
587
6
45 sh
635 sh
3
41
d
294
18870
7670
6720
450
554
594
256
445
6.0
3
3
27 sh
43
267 sh
293 sh
325 sh
549 sh
589
6
45 sh
635 sh
3
41
1
1
5
e
f
315
13040
5440
455
558
35.6
36.3
9.4
256
57220
48020
15910
7510
446
6.9
8.0
2.1
3
44 sh
266 sh
315
547 sh
592
5
6
98
45 sh
341 sh
256
633 sh
444
312
17560
6970
456
555
55290
46090
15500
6930
3
42 sh
266 sh
311
546 sh
590
5
6
96
45 sh
340 sh
249 sh
295
633 sh
396
297
6130
3560
2630
407
556
590
16610
6030
3
3
18 sh
32 sh
586
329 sh
2730
Fig. 2. The electronic absorption spectra of solutions of the bisspiropyran 1a (1, 2) and the spiropyran 5 (3, 4) in
toluene (1, 3) and in acetonitrile (2, 4).
1
365

When the solutions of the bisspiropyrans 1a-f are exposed to light corresponding to the absorption
bands of the cyclic isomeric forms, then coloration accompanied by the appearance of long-wave absorption
bands with maxima at 586-598 and 442-456 nm is observed in EAS (Table 1, Fig. 3).
-
5
Fig. 3. The electronic absorption spectra of the bisspiropyran 1f (c 1.6×10 M, acetonitrile, T 293 K) during
irradiation with the polychromatic light of a mercury lamp with λ < 400 nm (dt = 3 sec).
irr
Similarly, in the case of the monospirocyclic derivative 5, the photoinduced spectral changes are
characterized by the appearance of two absorption bands with maxima at 586-590 and 396-407 nm, depending
on the polarity of the solvent. Such absorption bands are characteristic of the S →S and S →S transitions
0
1
0
2
respectively in the molecules of the merocyanine isomers of the monospiropyrans B [2, 3]. Both in the case of
the bisspiropyrans 1a-f and in the case of the spiropyran 5, increase in the solvent polarity gives rise to a
hypsochromic shift in the long-wave absorption band maxima of the photoproducts. The observed negative
solvatochromism indicates a bipolar structure for the merocyanine isomers of spiropyrans 1a-f and 5 [18].
-5
Fig. 4. The kinetic curve (λobs 590 nm) for the thermal decoloration of the bisspiropyran 1f (c 1.6×10 M, T 293 K)
in acetonitrile and its corresponding logarithmic anamorphosis (inset).
1
366

As for the monospiran 5, thermal recyclization, leading to disappearance of the photoinduced color in
the solutions of the bisspiropyrans 1a-f, assures the reverse path for their photochromic process. The kinetics of
the reverse thermal reactions of compounds 1a-f, 5 obeys a monoexponential law and is characterized by time
constants of 2-8 sec in acetonitrile at 293 K (Fig. 4, Table 1). As in the case of the monospiropyrans of the
indoline series [19, 20], the increase in the lifetime of the colored forms of the bisspiropyrans 1e,f is due to the
presence of the electron-donating methoxy groups in their indoline fragments.
A consequence of the bipolarity in the merocyanine isomers of compounds 1a-f, 5 is their
destabilization in nonpolar solvents. Thus, in toluene at 293 K the lifetime of the colored forms B is less than
1
sec, and only with decrease of temperature it is possible under stationary conditions to record the absorption
of the merocyanine isomers, the lifetime of which amounts to 9.4-41.4 sec at 263 K (Table 1). Both in the polar
solvent acetonitrile and in the weakly polar toluene the decoloration rate of bisspiropyran 1a-f solutions is less
than that of the spiropyran 5. This is probably due to steric overloading of the merocyanine bisspiropyrans
compared with the open form of spiropyran 5, which increases the activation barriers for cis–trans isomerization
reactions in the thermal recyclization process.
Fig. 5. The kinetic curve recorded at the absorption band maximum of the colored form of bisspiropyran 1f (c
-5
2
.4×10 M, T 253 K) at 596 nm in toluene during (1) thermal decoloration reaction and during (2)
photochemical decoloration reaction upon irradiation with light at 578 nm.
In addition to the thermal recyclization reaction, a reverse photoreaction was also observed for the
bisspiropyrans 1a-f. With decrease of temperature, when the thermal reaction is substantially retarded,
irradiation with visible light at the absorption band of the merocyanine isomers leads to decoloration of
solutions previously colored by UV radiation, and this is accompanied by restoration of the initial (before UV
irradiation) absorption spectra of the cyclic forms of the bisspiropyrans. Thus, in particular, for the solution of
compound 1f previously colored by UV irradiation, the Figure 5 shows the time dependence of the optical
density at the absorption band maximum of the colored form at 253 K, which demonstrates the practical absence
of thermal recyclization at reduced temperature and, at the same time, complete decoloration during irradiation
with light at 578 nm.
1
367

Thus, while retaining the basic spectral kinetic characteristics of photochromic transformations, the
obtained symmetrical bisspiropyrans give molar extinction coefficients 2-3 times higher for the cyclic isomeric
forms than for the monospirocyclic derivatives.
EXPERIMENTAL
1
The H NMR spectra were recorded in CHCl on a Varian Unity-300 spectrometer (300 MHz) with the
3
residual protons of the solvent as internal standard. The electronic absorption spectra and the kinetic curves for
thermal recyclization of the investigated compounds at 293 K were recorded on an Agilent 8453
spectrophotometer with a sample thermostat attachment, and at 263 K on an Ocean Optics HR4000 fiber optic
spectrophotometer with a Quantum Northwest qPod thermostat. Photolysis of the solutions was performed with
a Newport system based on a 200-W mercury lamp with a set of interference light filters. Acetonitrile of
spectral purity (Aldrich) was used to prepare the solutions. Elemental analysis was performed on a KOVO CHN
analyzer. The melting points were determined on a Boetius hot stage apparatus.
The 3H-indolium salts 2a-f [21, 22] and the spiropyran 5 [23] were obtained by the indicated methods.
Dispiro[indoline-2,2'-pyrano[3,2-g]chromene-8',2"-indolines] 1a-f (General Method). A mixture of
Et N (0.28 ml, 2 mmol) and 2-PrOH (3 ml) was added dropwise over 30 min to a refluxing mixture of the salt
3
2
a-f (2 mmol), aldehyde 3 (0.18 g, 1 mmol), and 2-PrOH (12 ml). The reaction mixture was refluxed for 6 h, the
solvent was evaporated, and the residue was purified by column chromatography on Al O (benzene as eluent)
2
3
and recrystallized.
,1",3,3,3",3",10'-Heptamethyldispiro[indoline-2,2'(2H,8H)-pyrano[3,2-g]chromene-8',2"-indoline] (1a).
1
1
Yield 0.21 g (43%). Pale-pink crystals, mp 172.5-174°C (heptane). H NMR spectrum, δ, ppm (J, Hz): 1.15
(
6Н, s), 1.24 (3Н, s), and 1.25 (3Н, s, 3,3"-(СН ) ); 1.57 (3Н, s, 10'-СН ); 2.66 (3Н, s) and 2.67 (3Н, s,
3 2 3
1
,1"-СН ); 5.51 (2Н, d, J = 10.2, H-3',7'); 6.47 (2Н, d, J = 7.7, H-7,7"); 6.62 (1Н, s, H-5'); 6.75 (2Н, d, J = 10.2,
3
H-4',6'); 6.81 (2H, dt, J = 7.4, J = 1.0, H-5,5"); 7.03 (2H, dd, J = 7.3, J = 1.3, H-4,4"); 7.13 (2H, dt, J = 7.6,
J = 1.3, H-6,6"). Found, %: C 80.64; H 7.07; N 5.82. C H N O . Calculated, %: C 80.78; H 6.98; N 5.71.
3
3
34
2
2
1
,1"-Diallyl-3,3,3",3",10'-Pentamethyldispiro[indoline-2,2'(2H,8H)-pyrano[3,2-g]chromene-8',2"-indo-
1
line] (1b). Yield 0.25 g (46%). Pale-brown crystals, mp 182-183°C (heptane–toluene, 2:1). H NMR spectrum,
δ, ppm (J, Hz): 1.17 (6Н, s), 1.30 (3Н, s) and 1.32 (3Н, s, 3,3"-(СН ) ); 1.64 (3H, s, 10'-СН ); 3.56-3.66 (2H,
3
2
3
m) and 3.84-3.95 (2H, m, 1,1"-CH CH=CH ); 5.02 (1Н, qd, J = 10.3, J = 1.8) and 5.04 (1Н, qd, J = 10.3,
2
2
J = 1.8, 1,1"-CH CH=CH ); 5.14 (1H, qd, J = 17.2, J = 1.9) and 5.17 (1H, qd, J = 17.2, J = 1.9,
2
2
1
1
,1"-CH CH=CH ); 5.50 (1H, d, J = 10.2) and 5.51 (1H, d, J = 10.2, H-3',7'); 5.77-5.90 (2Н, m,
2 2
,1"-CH CH=CH ); 6.49 (2H, d, J = 7.7, H-7,7"); 6.59 (1H, s, H-5'); 6.72 (2H, d, J = 10.2, H-4',6'); 6.79 (2H,
2
2
dt, J = 7.4, J = 1.0, H-5,5"); 7.03 (2H, dd, J = 7.3, J = 1.3, H-4,4"); 7.09 (2H, dt, J = 7.6, J = 1.3, H-6,6").
Found, %: C 82.05; H 6.99; N 5.06. C H N O . Calculated, %: C 81.89; H 7.06; N 5.16.
37
38
2
2
1
,1"-Di-iso-butyl-3,3,3",3",10'-pentamethyldispiro[indoline-2,2'(2H,8H)-pyrano[3,2-g]chromene-
1
8
',2"-indoline] (1c). Yield 0.18 g (32%). Pale-yellow crystals, mp 171-173°C (heptane). H NMR spectrum, δ,
ppm (J, Hz): 0.88 (3H, d, J = 6.6); 0.89 (3H, d, J = 6.6); 0.90 (3H, d, J = 6.6) and 0.91 (3H, d, J = 6.6,
1
1
5
,1"-CH CH(CH ) ); 1.16 (3Н, s); 1.17 (3Н, s); 1.22 (3Н, s) and 1.24 (3Н, s, 3,3"-(СН ) ); 1.56 (3H, s,
2 3 2 3 2
0'-СН ); 1.92-2.04 (2H, m, 1,1"-CH CHМе ); 2.85-2.88 (4Н, m, 1,1"-CH CHМе ); 5.50 (1H, d, J = 10.2) and
3
2
2
2
2
.51 (1H, d, J = 10.2, H-3',7'); 6.47 (2H, d, J = 7.7, H-7,7"); 6.57 (1H, s, H-5'); 6.68 (1H, d, J = 10.2) and 6.69
(
1H, d, J = 10.2, H-4',6'); 6.76 (2H, dt, J = 7.4, J = 1.0, H-5,5"); 6.99-7.03 (2Н, m, H-4,4"); 7.10 (2H, dt,
J = 7.6, J = 1.3, H-6,6"). Found, %: C 81.60; H 8.15; N 4.66. C H N O . Calculated, %: C 81.49; H 8.07;
3
9
46
2
2
N 4.87.
3
,3,3",3",10'-Pentamethyl-1,1"-dipropyldispiro[indoline-2,2'(2H,8H)-pyrano[3,2-g]chrome-ne-
1
8
',2"-indoline] (1d). Yield 0.22 g (40%). Pale-pink crystals, mp 199-200°C (heptane). H NMR spectrum, δ,
ppm (J, Hz): 0.85 (3Н, t, J = 7.4) and 0.86 (3Н, t, J = 7.4, 1,1"-CH CH CH ); 1.14 (6Н, s), 1.23 (3Н, s), and
2
2
3
1
368

1
5
6
3 2 2 2 3 3 2 2 3
.24 (3Н, s, 3,3"-(СН ) ); 1.44-1.69 (7Н, m, 1,1"-CH CH CH , 10'-СН ); 2.97-3.20 (4Н, m, 1,1"-CH CH CH );
.50 (2Н, d, J = 10.2, H-3',7'); 6.48 (2Н, d, J = 7.7, H-7,7"); 6.59 (1Н, s, H-5'); 6.71 (2Н, d, J = 10.2, H-4',6');
.76 (2Н, dt, J = 7.4, J = 1.0, H-5,5"); 7.02 (2Н, dd, J = 7.3, J = 1.2, H-4,4"); 7.11 (2Н, dt, J = 7.6, J = 1.3,
H-6,6"). Found, %: C 81.43; H 7.62; N 5.03. C H N O . Calculated, %: C 81.28; H 7.74; N 5.12.
3
7
42
2
2
3
,3,3",3",10'-Pentamethyl-5,5"-dimethoxy-1,1"-dipropyldispiro[indoline-2,2'(2H,8H)pyrano[3,2-g]-
1
chromene-8',2"-indoline] (1e). Yield 0.24 g (39%). Pale-brown crystals, mp 188-189°C (heptane). H NMR
spectrum, δ, ppm (J, Hz): 0.84 (3Н, t, J = 7.4) and 0.85 (3Н, t, J = 7.4, 1,1"-CH CH CH ); 1.14 (6Н, s), 1.20
2
2
3
(
3Н, s), and 1.21 (3Н, s, 3,3"-(СН ) ); 1.47-1.71 (7Н, m, 1,1"-CH CH CH , 10'-СН ); 2.90-3.13 (4Н, m,
3 2 2 2 3 3
1
,1"-CH CH CH ); 3.77 (6Н, s, 5,5"-OСН ); 5.48 (2Н, d, J = 10.2, H-3',7'); 6.37 (2Н, d, J = 8.2, H-7,7"); 6.57
2 2 3 3
(
1Н, s, H-5'); 6.61-6.66 (4H, m, H-4,6,4",6"); 6.68 (2Н, d, J = 10.2, H-4',6'). Found, %: C 77.32; H 7.47;
N 4.70. C H N O . Calculated, %: C 77.20; H 7.64; N 4.62.
3
9
46
2
4
1
,1",3,3,3",3",10'-Heptamethyl-5,5"-dimethoxydispiro[indoline-2,2'(2H,8H)-pyrano[3,2-g]chromene-
1
8
',2"-indoline] (1f). Yield 0.24 g (44%). Pale-yellow crystals, mp 203-204°C (heptane). H NMR spectrum, δ,
ppm (J, Hz): 1.15 (6Н, s); 1.22 (3Н, s); 1.23 (3Н, s, 3,3"-(СН ) ); 1.57 (3Н, s, 10'-СН ); 2.60 (3Н, s) and 2.61
3
2
3
(
3Н, s, 1,1"-СН ); 3.78 (6Н, s, 5,5"-OСН ); 5.50 (2Н, d, J = 10.2, H-3',7'); 6.36-6.39 (2Н, m, H-7,7"); 6.60 (1Н,
3 3
s, H-5'); 6.64-6.68 (4H, m, H-4,6,4",6"); 6.74 (2Н, d, J = 10.2, H-4',6'). Found, %: C 76.50; H 6.78; N 5.01.
C H N O . Calculated, %: C 76.34; H 6.96; N 5.09.
3
5
38
2
4
4
,6-Dihydroxy-5-methylisophthalaldehyde (3). A mixture of 2-methylresorcinol (4) (2.23 g,
1
8 mmol), hexamethylenetetramine (5.61 g, 40 mmol), and trifluoroacetic acid (25 ml) was refluxed for 6 h in
an inert atmosphere. It was then cooled, and a mixture of conc. HCl (25 ml) and H O (30 ml) was added. The
2
reaction mixture was poured into water (250 ml) and maintained at room temperature for 12 h. The precipitate
was filtered off, washed with water, dried, and recrystallized from a 1:2 PhMe–2-PrOH mixture. Yield 1.88 g
1
(
(
58%). Pale-brown crystals, mp 185-186 °С (mp 181.5-183°С [8]). H NMR spectrum, δ, ppm (J, Hz): 2.11
3H, s, 5-СН ); 7.68 (1H, s, 2-H); 9.76 (2H, s, 1,3-CHO); 12.01 (2H, s, 4,6-OH). Found, %: C 60.09; H 4.41.
3
C H O . Calculated, %: C 60.00; H 4.48.
9
8
4
The work was carried out with financial support from the Ministry of Education and Science of the
Russian Federation (Federal Targeted Program "Scientific and Scientific-pedagogical personnel of the
Innovative Russia", 2009-2013, state contract P2435), the Grants Council of the President of the Russian
Federation (grant NSh-3233.2010.3), and the Russian Foundation for Basic Research (grant 09-03-00813).
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