Spiropyrans and spirooxazines 5. Synthesis of photochromic 8-(4,5-diphenyl-1,3-oxazol-2-y1)-substituted spiro[indoline-benzopyrans]

Article abstract of DOI:10.1007/s11172-009-0024-4

Photochromic spiro[indoline-benzopyrans] containing 4,5-diphenyloxazolyl group at position 8 of the benzopyran fragment have been obtained. New diphenyloxazolyl-substituted spiropyrans manifest considerably higher thermal stability of the merocyanine isom

Full text of DOI:10.1007/s11172-009-0024-4

Russian Chemical Bulletin, International Edition, Vol. 58, No. 1, pp. 156—161, January, 2009
156
Spiropyrans and spirooxazines
5.* Synthesis of photochromic 8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀsubstituted
spiro[indolineꢀbenzopyrans]**
N. A. Voloshin,a E. B. Gaeva,b A. V. Chernyshev,b A. V. Metelitsa,b and V. I. Minkinb
aSouthern Scientific Center, Russian Academy of Sciences,
41 ul. Chekhova, 344006 RostovꢀonꢀDon, Russian Federation
bScientific Research Institute of Physical and Organic Chemistry, Southern Federal University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Fax: +7 (863) 243 4667. Eꢀmail: photo@ipoc.rsu.ru
Photochromic spiro[indolineꢀbenzopyrans] containing 4,5ꢀdiphenyloxazolyl group at
position 8 of the benzopyran fragment have been obtained. New diphenyloxazolylꢀsubstituted
spiropyrans manifest considerably higher thermal stability of the merocyanine isomers than
their naphthopyran analogs.
Key words: triaryloxazole, spiropyrans, merocyanines, photochromism.
The synthesis and studies of new efficient photochroꢀ
of the CSp—O bond of the cyclic isomer A with subseꢀ
quent cis—transꢀisomerization to the metastable meroꢀ
cyanine form B.3—5
mic systems, prospective for development of polyfuncꢀ
tional materials for molecular electronics on their basis, is
an actual problem.2,3 Among the most wellꢀknown classes
of photochromic compounds, spiropyrans are of particuꢀ
lar interest since, depending on molecular structures, they
manifest spectroꢀkinetic characteristics varying in a wide
range, as well as due to the relative easiness of their
synthesis.3—5
On the basis of SPP by introduction of the correꢀ
sponding functional fragments, it is possible to obtain
polyfunctional molecular systems displaying, along with
photochromism, fluorescent,6 magnetic,7 and complexꢀ
forming properties switching by optical irradiation.8
Earlier,9 we reported on the synthesis of photochromic
5´ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀsubstituted spiro[indolineꢀ
naphthopyran], the merocyanine form of which reversibly
forms complexes with bivalent cations of heavy metals. In
continuation of this research, the present work deals with
the synthesis and description of photochromic properties
of a number of spirobenzopyrans containing diphenylꢀ
oxazolyl group at position 8 of the benzopyran fragment.
Mechanism of photochromic transformations of spiroꢀ
pyrans (SPP) (Scheme 1) includes the thermally and
photochemically reversible process of heterolytic cleavage
Scheme 1
Results and Discussion
There are two general methods for the synthesis of
SPP. The first of them (method I) includes a condensation
of corresponding heterocyclic cations with oꢀhydroxyꢀ
aromatic aldehydes in acidic medium, isolation of salts of
oꢀhydroxystyryl derivatives, and spirocyclization of
the latter under the action of a base. Method II, used the
most often for the preparation of indoline SPP, consists
in condensation of a methylene base (or the correspondꢀ
ing heterocyclic immonium salt in the presence of a base)
with oꢀhydroxyaromatic aldehydes. Both methods have
been used for the synthesis of indoline SPP containing
diphenyloxazolyl substituent (Scheme 2).
* For Part 4, see Ref. 1.
** Dedicated to Academician A. I. Konovalov on his 75th birthꢀ
day.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 156—161, January, 2009.
1066ꢀ5285/09/5801ꢀ0156 © 2009 Springer Science+Business Media, Inc.

Spiro[indolinebenzopyrans]
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
157
Scheme 2
Method I
Method II
PTC means phaseꢀtransfer catalysis
7: R1 = Me (a—d), Pr (e), All (f), Bui (g); R2 = H (a,e—g), Cl (b), Me (c), OMe (d); X = I (a,c—g), ClO4 (b);
8: R1 = Me (a—d), Pr (e); R2 = H (a,e), Cl (b), Me (c), OMe (d); X = I (a,c—e), ClO4 (b);
9: R1 = Me (a—d), Pr (e), All (f), Bui (g); R2 = H (a,e—g), Cl (b), Me (c), OMe (d)
Cyclization of aromatic acid benzoin esters (desyl
esters) by the Davidson method is a convenient method
for preparing 2,4,5ꢀtriarylꢀ1,3ꢀoxazoles.10 The synthesis
of the corresponding desyl esters, which can be obtained
by acylation of unsubstituted or symmetrically substituted
benzoin (in the case of unsymmetrically substituted benꢀ
zoin, formation of isomeric acylation products is posꢀ
sible), also is not difficult.11 However, in the case of
2ꢀ(hydroxyaryl)ꢀ4,5ꢀdiphenylꢀ1,3ꢀoxazoles, the syntheꢀ
sis of the corresponding desyl esters by this method is
complicated by the necessity to obtain acyl chlorides of
hydroxyꢀsubstituted arylcarboxylic acids and possible side
acylation reactions. In this case, preparation of the correꢀ
sponding desyl esters by the alkylation of carboxylic acid
salts with desyl chloride under phaseꢀtransfer catalysis
conditions is the most preferable.12
5ꢀChloroꢀ2ꢀhydroxybenzoic acid (1) was the starting
compound (see Scheme 2). The reaction of acid 1 with
sodium methoxide in methanol led to sodium salt 2, the
alkylation of which with 2ꢀchloroꢀ1,2ꢀdiphenylethanone
(3) under conditions of phaseꢀtransfer catalysis in the
system solid phase—liquid in the presence of 15ꢀcrownꢀ5

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Voloshin et al.
led to desyl ester 4. The reaction of desyl ester 4 with
ammonium acetate in acetic acid by the Davidson method10
afforded diphenyloxazolylꢀsubstituted phenol 5, the Duff
formylation of which in trifluoroacetic acid gave
oꢀhydroxybenzaldehyde 6.
and 5.16. The proton of the CH group is recorded as a
multiplet at δ 5.89.
The upfield portion of the SPP 9a—g spectra includes
several groups of mutually interacting signals for protons
related to the indoline and pyran fragments of the
molecule and the signals for two groups (each consisting
of five interacting nuclei) related to the phenyl groups of
the diphenyloxazolyl substituent. In contrast to diphenylꢀ
oxazolylꢀsubstituted phenol 5 and aldehyde 6, in the
1H NMR spectra of which the signals for the ten protons
of two phenyl rings of the diphenyloxazolyl group resonate
as fourꢀ and sixꢀproton multiplets, in the 1H NMR spectra
of the diphenyloxazolylꢀsubstituted spirobenzopyrans, the
signals for the protons of two phenyl rings of the benzꢀ
oxazole group form a complex picture of four multiplets
with the integral intensities being 2 : 3 : 3 : 2.
8ꢀDiphenyloxazolylꢀsubstituted spirobenzopyrans were
obtained by the twoꢀstep method (method I): viz., by the
reaction of 3Hꢀindolium salts 7a—e with diphenylꢀ
oxazolylꢀsubstituted hydroxybenzaldehyde 6 in acetic
acid, the isolation of salts of oꢀhydroxystyryl derivatives
8a—e, and treatment of the latter with ammonia, which
finally leads to SPP 9a—e. Spiropyrans 9f,g were syntheꢀ
sized by the oneꢀstep method (method II): viz., by the
condensation of 3Hꢀindolium salts 7f,g with oꢀhydroxyꢀ
benzaldehyde 6, which is formed by the formylation of
2ꢀ(2ꢀhydroxyphenyl)ꢀ4,5ꢀdiphenyloxazole 5, in the presence
of triethylamine as the base (see Scheme 2). Diphenylꢀ
oxazolylꢀsubstituted aldehyde 6 was obtained by formylaꢀ
tion of 2ꢀ(2ꢀhydroxyphenyl)ꢀ4,5ꢀdiphenyloxazole (5).
Colorless or lightly colored 8ꢀdiphenyloxazolylꢀsubꢀ
stituted spirobenzopyrans 9a—g was purified by chromaꢀ
tography and recrystallized. The structures of compounds
4—6 and 9a—g were established by 1H NMR spectroꢀ
scopy and confirmed by the elemental analysis data.
1H NMR spectroscopy is a convenient method for the
structural identification of SPP since it allows one to
quickly and accurately establish the structure of a comꢀ
pound obtained from characteristic shifts, spinꢀspin
coupling constants, and number of protons of various types.
The signals of such characteristic (indicative) groups as
gemꢀdimethyl group, Nꢀalkyl substituent, protons at the double
bond C(3)=C(4) usually can be easily identified and they
have different chemical shifts for open and cyclic forms.13—15
According to the 1H NMR spectroscopic data, the SPP
synthesized exist in solution (CDCl3) in the spirocyclic form.
The downfield region of SPP spectrum includes easily
identifiable two signals from the magnetically nonequivaꢀ
lent geminal methyl groups, the signal for the Nꢀalkyl
substituent (Me, Pr, All, Bui), and the signals for the
corresponding indicative groups of substituents (Me,
OMe) of SPP.
Prochirality of the methyl groups and the protons of
the methylene group of the Nꢀisobutyl substituent (SPP 9g)
and the methylene group of the Nꢀallyl substituent (SPP 9f)
leads to the diastereotopic splitting of signals for these groups.
Two doublets at δ 0.90 and 0.91 and two doublets of
doublets at δ 2.93 and 3.04 correspond to the diastereoꢀ
topic protons of the methyl and methylene groups of the
Nꢀisobutyl substituent of SPP 9g, respectively. A multiꢀ
plet of the signal for the proton of the CH group is
recorded around δ 2.04.
The diastereotopic protons of the methylene group
of the Nꢀallylꢀsubstituted SPP 9f resonate as a triplet
of doublets of doublets in the region δ 3.77 and 3.99. The
signals for the protons of the terminal CH2 group, each
resonating as quartet of doublets, are in the region δ 5.01
The 1H NMR spectroscopic data (the two signals from
the magnetically nonequivalent geminal methyl groups,
the signals for the protons of the phenyl rings of the
diphenyloxazolyl group, the diastereotopic splitting of
the signals for the protons of the Nꢀalkyl substituent, the
chemical shift values, and the spinꢀspin coupling conꢀ
stant values for the diastereotopic protons of the Nꢀisobuꢀ
tyl and Nꢀallyl substituents, the protons of the double
bond of the pyran fragment, and the protons of the
indoline and pyran fragments) unambiguously confirm
the structure of the SPP obtained. The absence of the
signals for the Nꢀmethyl and gemꢀdimethyl groups, transꢀ
vinylic protons, and other protons of the indoline and
pyran fragments in the regions of the spectrum characꢀ
teristic of the open plane merocyanine form without asymꢀ
metric center suggests that the compounds obtained exist
in solution (CDCl3) mainly in the spirocyclic form.
Electronic absorption spectra of cyclic forms A of SPP
9a—g in the region of spectral transparency of toluene are
characterized by the presence of two bands. The more
intensive one, a shortꢀwave band with molar extinction coefꢀ
ficient in the maximum being 19300—24200 L mol–1 cm–1
,
is susceptible to the changes in the SPP structure (subꢀ
stituents R1 and R2) and has the maximum in the region
300—312 nm (Table 1). In contrast to this, position of the
maximum of the less intensive (ε= 11800—13700 L mol–1 cm–1)
longꢀwave absorption band of SPP 9a—g does not depend
on the nature of substituents R1 and R2 in the indoline
part of SPP and is localized at 358 nm. This fact agrees
with the suggestion on the additivity of absorption spectra
of acoplanar fragments of SPP and on localization of the
electron transition, responsible for the more longꢀwave
absorption band, on the benzopyran part of the molecule.
Method of structural simulation showed that the elecꢀ
tronic absorption spectra of SPP can be represented as a
linear combination of absorption spectra of the composꢀ
ing fragments, that becomes possible due to the weak
interaction of the mutually orthogonal fragments. In this
case, the longꢀwave absorption band corresponds to the
photochemically active benzopyran fragment, whereas

Spiro[indolinebenzopyrans]
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
159
Table 1. Absorption spectra data and kinetic properties of comꢀ
pounds 9a—g in toluene, Т = 283 K
The absorption spectra of SPP 9a—g in toluene at
room temperature do not contain absorption band of the
merocyanine form, that suggests the absence of the ringꢀ
B
A
→
SPP
λ
A/nm (ε/L mol–1 cm–1
)
λ
B/nm
2
τ
max
max
chain equilibrium A
B in the ground state, which is
/s
observed for the structural analogs of compounds under
study, 5´ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀsubstituted spiroꢀ
naphthopyrans.9
1
2
1
9a
9b
9c
9d
9e
9f
301 (19300)
309 (22800)
306 (23700)
312 (24200)
302 (21600)
300 (20000)
302 (21800)
358 (11800)
358 (13700)
358 (13100)
358 (12300)
358 (12600)
358 (12500)
358 (12900)
450
470
440
440
440
445
445
648
650
650
655
650
650
650
25.5
9.8
On stopping the irradiation of solutions of SPP 9a—g,
their discoloration occurs, which is caused by the thermal
recyclization B → A. The kinetic curves of the relaxation
processes in the dark are satisfactoryly described by
the monoexponential function, which is confirmed by the
linear dependence of the logarithm of relative change of
optical density in the longꢀwave absorption band maxima
of the merocyanine isomers of SPP 9a—g from the thermal
discoloration time presented in Figure 2. The time conꢀ
stant values obtained from the kinetic curves of thermal
discoloration (lifetime) are presented in Table 1. In comꢀ
parison with 5´ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀsubstiꢀ
tuted spiro[indolineꢀnaphthopyran] having a high rate of
discoloration in the dark and characterizing by the lifeꢀ
time of the colored form of less than 1 s,9 compounds
9a—g, being its benzopyran analogs, manifest considerꢀ
ably higher thermal stability of the merocyanine isomers
with the lifetime of 10—60 s at Т = 283 K (see Table 1).
The lifetimes of the merocyanine forms B depend on
the nature of substituents at positions 1 and 5 of the
indoline fragment. The presence of electronꢀdonating
group at position 5 leads to the retardation of the thermal
process of discoloration. Thus, on going from 5ꢀchloro
derivative (SPP 9b) to the unsubstituted at position 5 SPP
9a and further to SPP 9c and 9d including electronꢀ
donating substituents, a considerable increase in the lifeꢀ
time of photoinduced isomers В is observed. An elongaꢀ
tion of the alkyl radical chain at the nitrogen atom (R1),
apparently, creating sterical hindrance in the process of
45.6
61.0
40.0
14.1
37.4
9g
the more shortꢀwave one, to the absorption of the heteroꢀ
cyclic part of the molecule.16
It was found that the cyclic forms of SPP do not posꢀ
sess fluorescent properties at 293 K.
On irradiation of toluene solutions of SPP 9a—g in
the region of the longꢀwave absorption of cyclic forms A,
their coloration is observed accompanied by the appearꢀ
ance in the electronic absorption spectra of bands (Fig. 1,
see Table 1) characteristic of acyclic merocyanine isoꢀ
mers B of SPP.3—5 It should be noted that SPP 9f underꢀ
goes irreversible photodegradation on the constant UV
irradiation.
Electronic absorption spectra of the merocyanine isoꢀ
mers B of SPP 9a—g in the visible region of the spectrum
include two bands: more intensive longꢀwave one with
the maximum at 648—655 nm and less intensive, with
maximum at 440—470 nm corresponding to the S0 → S1
and S0 → S2 transitions, respectively. Position of the maxiꢀ
mum of the longꢀwave absorption band of the meroꢀ
cyanine form B in the series of SPP 9a—g is considerably
shifted to the longꢀwave region of the spectrum on introꢀ
duction of the electronꢀdonating MeO group at position 5
of the indoline part of SPP (SPP 9d).
A
ln[(Ai – A∞)/(A0 – A∞)]
0.7
0.6
0.5
0.0
–0.5
9d
9c
9e
9g
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
0.4
hν
9a
0.3
0.2
0.1
9f
9b
10 15 20 25 30 35 40 45 50 55 t/s
5
350 400 450 500 550 600 650 700 750 λ/nm
Fig. 1. Electronic absorption spectra of SPP 9g in toluene on
Fig. 2. Linear anamorphoses of kinetic curves obtained in the
process of thermal discoloration of the merocyanine isomers of
compounds 9a—g in toluene, Т = 283 K.
irradiation with light with λ = 365 nm (C = 3.49•10–5 mol L–1
Т = 283 K).
,

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Voloshin et al.
5ꢀСhloroꢀ2ꢀhydroxyꢀ3ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)benzꢀ
aldehyde (6). A mixture of phenol 5 (3.48 g, 10 mmol), hexaꢀ
methylenetetramine (5.60 g, 40 mmol), and trifluoroacetic acid
(30 mL) was refluxed for 13 h under inert atmosphere and cooled
followed by the addition of a mixture of conc. hydrochloric acid
(14 mL) and water (28 mL). The reaction mixture was poured
into water (130 mL), a precipitate was filtered off, washed with
water, and dried. Benzaldehyde 6 obtained was recrystallized
from benzene. The yield was 2.67 g (71%), m.p. 184—185.5 °C.
Found (%): C, 70.46; H, 3.64; N, 3.67. C22H14ClNO3. Mol.
weight 375.81. Calculated (%): C, 70.31; H, 3.75; N, 3.73.
1H NMR, δ: 7.42—7.48 (m, 6 H, PhH); 7.67—7.72 (m, 4 H,
PhH); 7.89 (d, 1 H, H(4), J = 2.7 Hz); 8.11 (d, 1 H, H(6),
J = 2.7 Hz); 10.55 (s, 1 H, 1ꢀCHO); 12.12 (s, 1 H, 2ꢀOH).
8ꢀ(4,5ꢀDiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ3´,3´ꢀdimethylspiroꢀ
[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindolines] 9a—e (method I, general
procedure). A mixture of 3HꢀIndolium salt 7a—e (1 mmol),
aldehyde 6 (1 mmol), and glacial acetic acid (8 mL) was refluxed
for 5.5 h and kept for 12 h at ~20 °C. A precipitate formed was
filtered off, washed with ether, dried, and used further without
additional purification. A flow of dry ammonia was bubbled
through a suspension of salt 8a—e obtained in benzene (20 mL)
until dissolution of the precipitate, the solvent was evaporated,
the residue was purified by column chromatography on Al2O3
(eluent, benzene) and recrystallized.
the pyran ring formation, stabilizes the merocyanine form
В. This is confirmed by the lifetime values for SPP 9a
(R1 = Me), 9e (R1 = Pr), and 9g (R1 = Bui), which are 25,
40, and 37 s, respectively.
In conclusion, new 8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ
substituted spiro[indolineꢀbenzopyrans] are obtained
displaying photochromic properties in solutions. It was
found that, in contrast to naphthopyran analogs, the spiroꢀ
benzopyrans synthesized are characterized by significantly
higher thermal stability of the merocyanine isomers.
Experimental
1H NMR spectra were recorded on a Varian Unityꢀ300 spectroꢀ
meter (300 MHz) at 20 °C in CDCl3, δ values were determined
to within 0.01 ppm, spinꢀspin coupling constants, within 0.1 Hz.
Electronic absorption spectra and kinetic curves of thermal
recyclization reactions of compounds under study were recorded
on an Agilent 8453 spectrophotometer equipped with a thermoꢀ
stated cell. Photolysis of solutions was carried out by the mercury
DRShꢀ250 lamp supplied with a set of interferential light filters.
Toluene of spectrophotometric grade (Aldrich) was used for
preparation of solutions.
6ꢀChloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ1´,3´,3´ꢀtriꢀ
methylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9a). The yield
was 49%, m.p. 188—189 °C (from heptane—toluene, 2 : 1).
Found (%): C, 77.09; H, 5.01; N, 5.45. C34H27ClN2O2. Mol.
weight 531.05. Calculated (%): C, 76.90; H, 5.12; N, 5.28.
1H NMR, δ: 1.21, 1.39 (both s, 3 H each, 3´ꢀMe); 2.79 (s,
3 H, 1´ꢀMe); 5.85 (d, 1 H, H(3), J = 10.3 Hz); 6.58 (d, 1 H,
H(7´), J = 7.7 Hz); 6.86 (d, 1 H, H(4), J = 10.3 Hz); 6.93 (dt,
1 H, H(5´), J = 7.4 Hz, J = 0.9 Hz); 7.02—7.05 (m, 2 H, PhH);
7.12 (dd, 1 H, H(4´), J = 7.3 Hz, J = 1.2 Hz); 7.13 (d, 1 H, H(5),
J = 2.6 Hz); 7.20—7.27 (m, 4 H, H(6´), PhH); 7.30—7.38 (m,
3 H, PhH); 7.56—7.59 (m, 2 H, PhH); 8.04 (d, 1 H, H(7),
J = 2.6 Hz).
5´,6ꢀDichloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ1´,3´,3´ꢀ
trimethylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9b). The yield
was 52%, m.p. 215—216 °C (from heptane—toluene, 2 : 1).
Found (%): C, 72.04; H, 4.71; N, 4.87. C34H26Cl2N2O2. Mol.
weight 565.50. Calculated (%): C, 72.21; H, 4.63; N, 4.95.
1H NMR, δ: 1.21, 1.38 (both s, 3 H each, 3´ꢀMe); 2.75 (s, 3 H,
1´ꢀMe); 5.82 (d, 1 H, H(3), J = 10.3 Hz); 6.46 (d, 1 H, H(7´),
J = 8.2 Hz); 6.87 (d, 1 H, H(4), J = 10.3 Hz); 7.07 (d, 1 H,
H(4´), J = 2.2 Hz); 7.08—7.11 (m, 2 H, PhH); 7.13 (d, 1 H,
H(5), J = 2.6 Hz); 7.16 (dd, 1 H, H(6´), J = 8.2 Hz, J = 2.2 Hz);
7.27—7.39 (m, 6 H, PhH); 7.55—7.59 (m, 2 H, PhH); 8.05 (d,
1 H, H(7) J = 2.6 Hz).
1,2ꢀDiphenylꢀ2ꢀchloroethanone (3) was obtained according
to the known procedure.17
3HꢀIndolium iodides 7a,c—g were synthesized according to
the methods described earlier.18—21
Sodium 5ꢀchloroꢀ2ꢀhydroxybenzoate (2). A mixture of
5ꢀchloroꢀ2ꢀhydroxybenzoic acid 1 (8.63 g, 50 mmol) and sodium
methoxide (2.70 g, 50 mmol) in methanol (40 mL) was refluxed
for 2 h. Methanol was half evaporated in vacuo followed by the
addition of ether (30 mL). A precipitate was filtered off, dried
in vacuo, and used further without additional purification. The
yield was 8.47 g (87%).
2ꢀOxoꢀ1,2ꢀdiphenylethyl 2ꢀhydroxyꢀ5ꢀchlorobenzoate (4).
A mixture of sodium salt 2 (6.42 g, 33 mmol), 15ꢀcrownꢀ5
(1 mL), and acetonitrile (50 mL) was stirred for 0.5 h at 70 °C
followed by the addition of desyl chloride 3 (6.93 g, 30 mmol).
The mixture was stirred under reflux for 10 h and then poured
into icy water. A precipitate formed was filtered off, washed
with water, and dried. Ester 4 obtained was recrystallized from
propanꢀ2ꢀol—isooctane (3 : 1). The yield was 9.02 g (82%),
m.p. 123—124 °C. Found (%): C, 68.63; H, 4.21. C21H15ClO4.
Mol. weight 366.80. Calculated (%): C, 68.77; H, 4.12.
1H NMR, δ: 6.94 (d, 1 H, H(3), J = 8.9 Hz); 7.08 (s, 1 H,
1ꢀCOOCH(Ph)C(O)Ph); 7.40—7.47 (m, 6 H, H(4), PhH);
7.53—7.58 (m, 3 H, PhH); 7.93 (d, 1 H, H(6), J = 2.7 Hz);
7.96—7.99 (m, 2 H, PhH); 10.38 (s, 1 H, 2ꢀOH).
6ꢀChloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ1´,3´,3´,5´ꢀtetraꢀ
methylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9c). The yield
was 42%, m.p. 194—195.5 °C (from heptane—toluene, 2 : 1).
Found (%): C, 77.01; H, 5.23; N, 5.28. C35H29ClN2O2. Mol.
weight 545.08. Calculated (%): C, 77.12; H, 5.36; N, 5.14.
1H NMR, δ: 1.20, 1.36 (both s, 3 H each, 3´ꢀMe); 2.34 (s, 3 H,
5´ꢀMe); 2.76 (s, 3 H, 1´ꢀMe); 5.84 (d, 1 H, H(3), J = 10.3 Hz);
6.48 (d, 1 H, H(7´), J = 7.8 Hz); 6.84 (d, 1 H, H(4),
J = 10.3 Hz); 6.91 (s, 1 H, H(4´)); 7.02—7.08 (m, 3 H, H(6´),
PhH); 7.12 (d, 1 H, H(5) J = 2.6 Hz); 7.16—7.25, 7.31—7.38
(both m, 3 H each, PhH); 7.56—7.60 (m, 2 H, PhH); 8.04 (d,
1 H, H(7) J = 2.6 Hz).
4ꢀChloroꢀ2ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)phenol
(5).
A mixture of desyl benzoate 4 (7.34 g, 20 mmol), ammonium
acetate (9.24 g, 0.12 mol), and acetic acid (40 mL) was refluxed
for 4 h and poured into ice (500 g). A precipitate was filtered
off, washed with water, and dried. Phenol 5 obtained was
recrystallized from propanꢀ2ꢀol. The yield was 4.87 g (70%),
m.p. 136—137 °C. Found (%): C, 72.38; H, 3.95; N, 4.11.
C21H14ClNO2. Mol. weight 347.80. Calculated (%): C, 72.52;
1
H, 4.06; N, 4.03. H NMR, δ: 7.04 (d, 1 H, H(6), J = 8.9 Hz);
7.32 (dd, 1 H, H(5), J = 8.9 Hz, J = 2.6 Hz); 7.39—7.46 (m,
6 H, PhH); 7.68—7.71 (m, 4 H, PhH); 7.89 (d, 1 H, H(3),
J = 2.6 Hz); 11.23 (s, 1 H, OH).

Spiro[indolinebenzopyrans]
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
161
6ꢀChloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ5´ꢀmethoxyꢀ
1´,3´,3´ꢀtrimethylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9d).
The yield was 46%, m.p. 204.5—205.5 °C (from heptane—
toluene, 2 : 1). Found (%): C, 77.15; H, 5.11; N, 5.14.
C35H29ClN2O3. Mol. weight 561.08. Calculated (%): C, 74.92;
H, 5.21; N, 4.99. 1H NMR, δ: 1.22, 1.38 (both s, 3 H each,
3´ꢀMe); 2.72 (s, 3 H, 1´ꢀMe); 3.79 (s, 3 H, 5´ꢀOMe); 5.84 (d,
1 H, H(3), J = 10.3 Hz); 6.47 (d, 1 H, H(7´), J = 8.2 Hz); 6.74
(dd, 1 H, H(6´), J = 8.2 Hz, J = 2.6 Hz); 6.76 (d, 1 H, H(4´),
J = 2.6 Hz); 6.85 (d, 1 H, H(4), J = 10.3 Hz); 7.04—7.08
(m, 2 H, PhH); 7.12 (d, 1 H, H(5), J = 2.6 Hz); 7.22—7.26,
7.31—7.38 (both m, 3 H each, PhH); 7.56—7.60 (m, 2 H, PhH);
8.05 (d, 1 H, H(7) J = 2.6 Hz).
H(4), J = 10.3 Hz); 6.90 (dt, 1 H, H(5´), J = 7.4 Hz, J = 0.9 Hz);
7.03—7.07 (m, 2 H, PhH); 7.11 (dd, 1 H, H(4´), J = 7.3 Hz,
J = 1.1 Hz); 7.12 (d, 1 H, H(5), J = 2.6 Hz); 7.21 (dt, 1 H,
H(6´), J = 7.6 Hz, J = 1.3 Hz); 7.22—7.26, 7.31—7.38 (both m,
3 H each, PhH); 7.55—7.59 (m, 2 H, PhH); 8.02 (d, 1 H, H(7),
J = 2.6 Hz).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 06ꢀ03ꢀ32988ꢀa)
and the Ministry of Education and Science of Russian
Federation (Departmental Scientific Program ''Developꢀ
ment of the Scientific Potential of the Higher School'',
Project No. RNP2.1.1.1938).
6ꢀChloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ3´,3´ꢀdimethylꢀ
1´ꢀpropylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9e). The yield
was 44%, m.p. 186—187.5 °C (from heptane—toluene, 2 : 1).
Found (%): C, 77.20; H, 5.69; N, 4.90. C36H31ClN2O2. Mol.
weight 559.11. Calculated (%): C, 77.34; H, 5.59; N, 5.01.
1H NMR, δ: 0.87 (t, 3 H, 1´ꢀPr, J = 7.4 Hz); 1.20, 1.37 (both s,
3 H each, 3´ꢀMe); 1.63, 3.20 (both m, 2 H each, 1´ꢀPr); 5.85 (d,
1 H, H(3), J = 10.3 Hz); 6.59 (d, 1 H, H(7´), J = 7.7 Hz); 6.82
(d, 1 H, H(4), J = 10.3 Hz); 6.90 (dt, 1 H, H(5´), J = 7.4 Hz,
J = 0.9 Hz); 7.02—7.06 (m, 2 H, PhH); 7.10—7.12 (m, 2 H,
H(4´), H(5)); 7.18—7.24 (m, 4 H, H(6´), PhH); 7.30—7.38 (m,
3 H, PhH); 7.56—7.60 (m, 2 H, PhH); 8.04 (d, 1 H, H(7),
J = 2.6 Hz).
8ꢀ(4,5ꢀDiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ3´,3´ꢀdimethylspiro[2Hꢀ
1ꢀbenzopyranꢀ2,2´ꢀindolines] 9f,g (method II, general procedure).
A mixture of 3HꢀIndolium salt 7f,g (1 mmol), triethylamine
(0.14 mL, 1 mmol), and aldehyde 6 (1 mmol) in benzene (8 mL)
and propanꢀ2ꢀol (2 mL) was refluxed for 10 h, concentrated, and
the residue was purified by column chromatography on Al2O3
(eluent, benzene) and recrystallized.
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1´ꢀAllylꢀ6ꢀchloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ3´,3´ꢀ
dimethylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9f). The yield
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Calculated (%): C, 77.62; H, 5.25; N, 5.03. H NMR, δ: 1.23,
1.39 (both s, 3 H each, 3´ꢀMe); 3.77 (tdd, 1 H, 1´ꢀCH2CH=CH2,
J = 17.3 Hz, J = 5.3 Hz, J = 1.6 Hz, J = 1.6 Hz); 3.99 (tdd, 1 H,
1´ꢀCH2CH=CH2, J = 17.3 Hz, J = 4.2 Hz, J = 2.0 Hz,
J = 2.0 Hz); 5.01 (qd, 1 H, 1´ꢀCH2CH=CH2, J = 10.3 Hz,
J = 1.7 Hz, J = 1.7 Hz, J = 1.7 Hz); 5.16 (qd, 1 H, 1´ꢀCH2CH=CH2,
J = 17.2 Hz, J = 1.8 Hz, J = 1.8 Hz, J = 1.8 Hz); 5.85 (d, 1 H,
H(3), J = 10.3 Hz); 5.89 (m, 1 H, 1´ꢀCH2CH=CH2); 6.59 (d,
1 H, H(7´), J = 7.7 Hz); 6.82 (d, 1 H, H(4), J = 10.3 Hz); 6.92
(dt, 1 H, H(5´), J = 7.4 Hz, J = 0.9 Hz); 7.02—7.06 (m, 2 H,
PhH); 7.10—7.14 (m, 2 H, H(4´), H(5)); 7.18—7.24 (m, 4 H,
H(6´), PhH); 7.31—7.38 (m, 3 H, PhH); 7.56—7.60 (m, 2 H,
PhH); 8.04 (d, 1 H, H(7) J = 2.6 Hz).
6ꢀChloroꢀ8ꢀ(4,5ꢀdiphenylꢀ1,3ꢀoxazolꢀ2ꢀyl)ꢀ1´ꢀisobutylꢀ3´,3´ꢀ
dimethylspiro[2Hꢀ1ꢀbenzopyranꢀ2,2´ꢀindoline] (9g). The yield
was 45%, m.p. 182—183 °C (from heptane). Found (%):
C, 77.41; H, 5.65; N, 4.97. C37H33ClN2O2. Mol. weight 573.13.
Calculated (%): C, 77.54; H, 5.80; N, 4.89. 1H NMR, δ:
0.90 (d, 3 H, 1´ꢀCH2CH(CH3)2, J = 6.7 Hz); 0.91 (d, 3 H,
1´ꢀCH2CH(CH3)2, J = 6.6 Hz); 1.23, 1.38 (both s, 3 H each,
3´ꢀMe); 2.04 (m, 1 H, 1´ꢀCH2CH(CH3)2); 2.93 (dd, 1 H,
1´ꢀCH2CH(CH3)2, J = 14.5 Hz, J = 9.4 Hz); 3.04 (dd, 1 H,
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J = 10.3 Hz); 6.59 (d, 1 H, H(7´), J = 7.7 Hz); 6.81 (d, 1 H,
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Received November 9, 2007;
in revised form September 30, 2008