Photocyclization of 2-azido-1-(4-tert-butylphenoxy)-9,10-anthraquinone in the presence of substituted phenols

Article abstract of DOI:10.1007/s11172-007-0171-4

New types of phototransformations in the quinone series, viz., photocyclizations of 1-aryloxy-2-azido-9,10-anthraquinone in the presence of phenols, were studied. The photolysis affords mainly 5H-naphtho[2,3-c] phenoxazine-8,13-diones, in which the nitrogen atom is covalently bound to the phenyl ring of the attached phenol. As a result, complex polycyclic derivatives of phenoxazines were prepared in high yields in one step.

Full text of DOI:10.1007/s11172-007-0171-4

Russian Chemical Bulletin, International Edition, Vol. 56, No. 6, pp. 1130—1134, June, 2007
1130
Photocyclization of 2ꢀazidoꢀ1ꢀ(4ꢀtertꢀbutylphenoxy)ꢀ9,10ꢀanthraquinone
in the presence of substituted phenols*
L. S. Klimenko, I. A. Os´kina, V. M. Vlasov,ꢀ I. Yu. Bagryanskaya, and Yu. V. Gatilov
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences,
9 prosp. Akad. Lavrent´eva, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383) 330 9752. Eꢀmail: vmvlasov@nioch.nsc.ru
New types of phototransformations in the quinone series, viz., photocyclizations of
1ꢀaryloxyꢀ2ꢀazidoꢀ9,10ꢀanthraquinone in the presence of phenols, were studied. The photolyꢀ
sis affords mainly 5Hꢀnaphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdiones, in which the nitrogen atom is
covalently bound to the phenyl ring of the attached phenol. As a result, complex polycyclic
derivatives of phenoxazines were prepared in high yields in one step.
Key words: photolysis, photocyclization, 9,10ꢀanthraquinones, azides, 5Hꢀnaphꢀ
tho[2,3ꢀc]phenoxazineꢀ8,13ꢀdiones, phenols, Xꢀray diffraction analysis.
It is known1,2 that visible light irradiation of 1ꢀaryloxyꢀ
9,10ꢀanthraquinone derivatives causes migration of the
aryl group to the periꢀoxygen atom to form highly reactive
9ꢀaryloxyꢀ1,10ꢀanthraquinones. Earlier, we have modiꢀ
fied 1ꢀaryloxyꢀ9,10ꢀanthraquinones by introducing the
second photoactive (acyloxy,3 nitroso,4 diazo, azo,5 or
azido6,7) group into the quinone molecule and studied the
factors determining the reactivity and the preference of a
particular reaction pathway. The photolysis and thermolyꢀ
sis of 2ꢀdiazo and azido derivatives proved to be a conveꢀ
nient general approach to the synthesis of new heteroꢀ
cyclic 9,10ꢀanthraquinone derivatives annelated at posiꢀ
tions 1 and 2 with furan, thiophene, phenoxazine, or
phenothiazine heterocycles. A new photoreaction, viz.,
the cyclization of 2ꢀazidoꢀ1ꢀ(4ꢀtertꢀbutylphenoxy)ꢀ9,10ꢀ
anthraquinone in the presence of excess 4ꢀtertꢀbutylphenol
yielding 5Hꢀnaphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdione subꢀ
stituted at the nitrogen atom, was discovered in the study.7
To our knowledge, data on analogous photoinitiated cyꢀ
clizations of azido derivatives are lacking in the literature.
Undoubtedly, a detailed investigation of this cyclizaꢀ
tion is of theoretical interest because the mechanism of
this reaction and the dependence of its efficiency on the
chemical nature of the reagents remain unclear. These
data can be useful also in the applied aspect because the
observed photocyclization is a new oneꢀstep synthesis of
various polycyclic phenoxazines and phenothiazines.
The aim of the present study was to investigate photoꢀ
chemical transformations of 2ꢀazidoꢀ1ꢀ(4ꢀtertꢀbutylꢀ
phenoxy)ꢀ9,10ꢀanthraquinone in the presence of phenol
and its alkyl derivatives, compare the efficiency of the
phototransformations, and determine the structures of
photocyclization products.
Results and Discussion
2ꢀAzidoꢀ1ꢀ(4ꢀtertꢀbutylphenoxy)ꢀ9,10ꢀanthraquinone
(1) was synthesized from 2ꢀaminoꢀ1ꢀchloroꢀ9,10ꢀanthraꢀ
quinone by introducing the 4ꢀtertꢀbutylphenoxy group
according to a known procedure8 followed by the diazotiꢀ
zation of the amino group and the reaction of the resultꢀ
ing solution of the diazonium salt with NaN3 by analogy
with the study.9
A solution of azidoanthraquinone 1 and phenol ArOH
in a ratio of 1 : 3 in dry benzene was irradiated at 20 °C
with full light from a mercury lamp or with sunlight until
azide 1 was completely consumed (Scheme 1). The
photocyclization in the presence of unsubstituted phenol
or orthoꢀ and paraꢀalkylꢀsubstituted phenols afforded
the corresponding 5Hꢀnaphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀ
diones 2a—d in high yields. In all cases, small amounts
(<5%) of 1ꢀhydroxyꢀ2ꢀ(4ꢀtertꢀbutylphenylamino)ꢀ9,10ꢀ
anthraquinone were detected in photolysates by analogy
with the study.7
The structures of phenoxazines 2a—d were determined
by elemental analysis, mass spectrometry, and IR, UV,
and 1H NMR spectroscopy. When assigning the signals in
1
the H NMR spectra of compounds 2a—d (see the Exꢀ
perimental section), we found signals for six protons of
the anthraquinone moiety, viz., the characteristic pairs of
signals for the protons H(10), H(11) and H(9), H(12) of
the unsubstituted anthraquinone ring and two signals for
* Dedicated to the memory of Academician N. N. Vorozhtsov
on the 100th anniversary of his birth.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1089—1093, June, 2007.
1066ꢀ5285/07/5606ꢀ1130 © 2007 Springer Science+Business Media, Inc.

5HꢀNaphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdiones
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 6, June, 2007
1131
Scheme 1
similar pentacyclic moiety in the Cambridge Structural
Database.12 The most similar compounds containing the
phenoxazine moiety, such as 2ꢀmethylꢀ2ꢀ(10ꢀphenoxaziꢀ
nyl)propionitrile,13 10ꢀpiperidylacetylphenoxazine,14
10ꢀacetylꢀ1ꢀcyanophenoxazine,15 and 10ꢀacetylꢀ3ꢀcyanoꢀ
phenoxazine,16 are nonplanar, and the oxazine ring in
these compounds adopts a boat conformation. The bond
lengths and bond angles in the phenoxazine fragment of
molecule 2c are similar to the corresponding parameters
in the aboveꢀmentioned compounds. The N(5)—C(4a)
and N(5)—C(5a) bond lengths are the only exceptions. In
molecule 2c, these bonds are shortened to 1.392(6) and
1.396(6) Å compared to the analogous bonds in the referꢀ
ence compounds (from 1.426 to 1.455 Å). Presumably,
this difference is associated with a flattening of the oxꢀ
azine ring in molecule 2c. The plane passing through the
atoms of the phenyl ring C(1´)—C(6´) (the rms deviation
from the plane is 0.006 Å) is virtually perpendicular to the
plane of the pentacyclic moiety (the dihedral angle beꢀ
tween these two fragments is 82.4(1)°).
In the crystal structure of compound 2c, the molꢀ
ecules are linked to each other by the O(3)—H...O(2)
hydrogen bonds (O(3)...O(2), 2.864(6) Å; H...O,
1.93(6) Å; O(3)—H...O, 154(4)°) to form infinite headꢀ
toꢀtail chains along the b axis. The chains are linked in
pairs by πꢀstacking arene—arene interactions (Fig. 2). The
distance between the planes of the adjacent molecules
involved in the πꢀstacking interactions is 3.56 Å; the
intercenter distance between the 1,4ꢀbenzoquinone and
oxazine rings is 3.568(3) Å. The pairs of chains are packed
in stacks along the a axis with the distance of 3.45 Å
between the planes of the adjacent molecules. The
intercenter distances vary from 3.934(3) to 4.133(4) Å,
which is indicative of a large shift of the πꢀstacking interꢀ
action.
The Xꢀray diffraction data provide unambiguous eviꢀ
dence that the cyclization under study is accompanied by
a change in the position of the tertꢀbutyl substituent in
the phenoxazine ring. The substituent, which is in the
para position with respect to the oxygen atom in the
aryloxy group of starting azide 1, is attached at the
para position with respect to the nitrogen atom in the
reaction products. In earlier studies17—19 on the photolyꢀ
sis and thermolysis of isomeric 2ꢀaryloxyꢀ1ꢀazidoꢀ9,10ꢀ
anthraquinones, the same change in the position of the
substituent was demonstrated by the independent synꢀ
thesis.
Ar in ArOH
2
OH
R
t/h
Yield (%)
Ph
a
b
c
d
4´
2´
4´
2´
H
4.5
3.5
3.0
4.0
87
82
86
79
4ꢀMeС6H4
2,6ꢀMe2С6H3
4ꢀButС6H4
5´ꢀMe
3´,5´ꢀMe2
5´ꢀBut
the protons H(6) and H(7) of the substituted ring. The
1H NMR spectra of products 2b,d obtained by the
photocyclization with paraꢀsubstituted phenols show two
set of signals, each set corresponding to three aromatic
protons (H(1), H(3), H(4) and H(3´), H(4´), H(6´)) with
the splitting pattern being typical of 1,2,4ꢀtrisubstituted
benzenes.10 This is evidence for the attachment of the
nitrogen atom at the ortho position with respect to the
hydroxy group. In the 1H NMR spectra of compounds
2a,c, the signals for the protons H(2´), H(3´), H(5´),
H(6´) and H(2´), H(6´) appear as a broad singlet and a
singlet, respectively, which is indicative of the replaceꢀ
ment of the hydrogen atom in the para position of
the aromatic ring of phenol. To prove the position of
the tertꢀbutyl substituent in the aromatic ring of the
phenoxazine fragment, we studied compound 2c by Xꢀray
diffraction.
The threeꢀdimensional structure of compound 2c is
shown in Fig. 1. The pentacyclic moiety of the molecule
is virtually planar (the rms deviation from the plane is
0.109 Å). However, although the phenyl rings are planar
within 0.006—0.044 Å, the O(14) and N(5) atoms in the
oxazine ring deviate in the same direction from the plane
passing through the other four C atoms of the oxazine ring
by 0.072 and 0.064 Å, respectively. The geometric paramꢀ
eters of molecule 2c are within 3σ of the mean values.11 It
should be noted that we found no structures containing a
Our experimental data are not contradictory to the
commonly accepted mechanism of photocyclization of
aryl azides containing an arylthio or aryloxy group in the
ortho positions with respect to the azido group7,17—20
(Scheme 2). According to the published data, the carbon
atom of the substituent bound to the heteroatom is atꢀ
tacked by singlet nitrene 3 that is generated upon photoꢀ
decomposition of the azido group21 to form intermediate

1132
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 6, June, 2007
Klimenko et al.
C(17)
C(16)
C(18)
C(15)
C(2)
C(3)
C(4)
C(1)
C(14A)
O(2)
O(14)
C(12)
C(13)
C(4A)
N(5)
C(1´)
C(13B)
C(12A)
C(13A)
C(11)
C(10)
C(2´)
C(3´)
C(5A)
C(6)
C(19)
C(9)
C(8A)
C(7A)
C(8)
O(1)
C(6´)
C(5´)
C(7)
C(4´)
O(3)
C(20)
Fig. 1. Threeꢀdimensional structure of 2ꢀtertꢀbutylꢀ5ꢀ(4´ꢀhydroxyꢀ3´,5´ꢀdimethylphenyl)naphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdione (2c)
based on Xꢀray diffraction data.
Scheme 2
Fig. 2. πꢀStacking interactions between molecules 2c in the adꢀ
jacent chains based on Xꢀray diffraction data (the projection
along the crystallographic direction [101]).
biradical spiro complex 4. The formation of phenoxazines
2a—d upon irradiation of azide 1 in the presence of subꢀ

5HꢀNaphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdiones
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 6, June, 2007
1133
2ꢀtertꢀButylꢀ5ꢀ(2´ꢀhydroxyꢀ5´ꢀmethylphenyl)ꢀ5Hꢀ
naphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdione (2b). M.p. 238—241 °C.
Found (%): C, 78.00; H, 5.36; N, 3.09. C31H25NO4. Calcuꢀ
lated (%): C, 78.32; H, 5.26; N, 2.95. 1H NMR (CDCl3), δ: 1.23
(s, 9 H, But); 2.30 (s, 3 H, Me); 5.97 (d, 1 H, H(3´), J = 8.5 Hz);
4.57 (br.s, 1 H, OH); 6.09 (d, 1 H, H(6), J = 8.5 Hz); 6.72 (dd,
1 H, H(4´), J1 = 8.5 Hz, J2 = 3.0 Hz); 6.82 (d, 1 H, H(6´), J =
3.0 Hz); 6.98 (d, 1 H, H(1), J = 3.0 Hz); 7.02 (d, 1 H, H(4), J =
8.5 Hz); 7.12 (d, 1 H, H(7), J = 8.5 Hz); 7.45 (dd, 1 H, H(3),
J1 = 8.5 Hz, J2 = 3.0 Hz); 7.66 (m, 2 H, H(10), H(11)); 8.10 (m,
2 H, H(9), H(12)). IR, ν/cm–1: 3430 (OH); 3035, 2963 (C—H);
1664 (C=O); 1590, 1522 (C=C). UVꢀVis, λmax/nm (logε): 268
(4.70), 313 (3.64), 403 (3.48), 560 (3.98). MS, m/z: 475 [M+].
2ꢀtertꢀButylꢀ5ꢀ(4´ꢀhydroxyꢀ3´,5´ꢀdimethylphenyl)ꢀ5Hꢀ
naphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdione (2c). M.p. 325—327 °C.
1H NMR (CDCl3), δ: 1.23 (s, 9 H, But); 2.29 (s, 6 H, 2 Me);
5.10 (br.s, 1 H, OH); 5.92 (d, 1 H, H(4), J = 8.5 Hz); 6.17 (d,
1 H, H(6), J = 8.5 Hz); 6.66 (dd, 1 H, H(3), J1 = 8.5 Hz, J2 =
3.0 Hz); 6.90 (s, 2 H, H(2´), H(6´)); 7.00 (d, 1 H, H(1), J =
3.0 Hz); 7.63 (d, 1 H, H(7), J = 8.5 Hz); 7.72 (m, 2 H, H(10),
H(11)); 8.25 (m, 2 H, H(9), H(12)). IR, ν/cm–1: 3485 (OH);
3078, 2960, 2873 (C—H); 1664 (C=O); 1597, 1516 (C=C).
UVꢀVis, λmax/nm (logε): 264 (4.78), 313 (3.60), 405 (3.61), 560
stituted phenols can be attributed to the radical substituꢀ
tion of the hydrogen atom in phenol derivatives by this
intermediate biradical spiro complex. The experimentally
observed direction of the attack (ortho and para positions)
is consistent with the known features of the freeꢀradical
aromatic substitution.22,23
To summarize, we studied a new type of photoꢀ
transformations in the quinone series, viz., the photoꢀ
cyclization of 1ꢀaryloxyꢀ2ꢀazidoꢀ9,10ꢀanthraquinones in
the presence of phenols. 5HꢀNaphtho[2,3ꢀc]phenoxazineꢀ
8,13ꢀdiones, in which the nitrogen atom is covalently
bound to the phenyl ring of the introduced reagent, were
prepared in high yield. The present study demonstrated
that the aboveꢀdescribed photocyclization provides a conꢀ
venient oneꢀstep procedure for the synthesis of various
Nꢀsubstituted polycyclic derivatives of phenoxazine.
Experimental
The IR spectra were recorded on a Vectorꢀ22 (Bruker) specꢀ
trophotometer in KBr pellets. The UVꢀVis spectra were meaꢀ
sured on a Hewlett Packard Agilent 8453 spectrophotometer in
(3.90)
. Highꢀresolution mass spectrum, found: 489.1951 [M+].
1
ethanol (1•10–4 mol L–1). The H NMR spectra were recorded
C
32H27NO4. Calculated: M = 489.1940.
on a Bruker WРꢀ200SY instrument (the chemical shifts are given
on the δ scale) with SiMe4 as the internal standard. The EI mass
spectra were obtained on a Finnigan MATꢀ8200 instrument.
The TLC analysis was carried out on Silufol UVꢀ254 plates
using a 9 : 1 toluene—ethanol system as the eluent. The column
chromatography was carried out on silica gel (140—350 µm).
The solvents were dried before use. Photolysis was carried out
using light from a SVDꢀ120A lamp through an UFSꢀ1 light filter
(280—400 nm) and also with the use of the full spectrum of the
mercury lamp. The synthesis and physicochemical characterisꢀ
tics of the starting azidoanthraquinone 1 have been described
earlier.7
Preparative photolysis of azide 1 in the presence of phenols
(general procedure). A solution of compound 1 (0.4 g, 1 mmol)
and substituted phenol (3 mmol) in dry benzene (0.5 L) was
irradiated at 20 °C for 3—4.5 h until the starting compound
disappeared (TLC monitoring). The reaction solution was conꢀ
centrated, and the residue was chromatographed on silica gel.
1ꢀHydroxyꢀ2ꢀ(4ꢀtertꢀbutylphenyl)aminoꢀ9,10ꢀanthraquinone
(0.01—0.02 g) was isolated from the first violet band by elution
with benzene. This product was identified by comparing with an
authentic sample.8 Then the major violet band was eluted with
chloroform. Products 2a—d were recrystallized from an ethaꢀ
nol—benzene mixture.
2ꢀtertꢀButylꢀ5ꢀ(4´ꢀhydroxyphenyl)ꢀ5Hꢀnaphtho[2,3ꢀc]phenꢀ
oxazineꢀ8,13ꢀdione (2a). M.p. 236—239 °C. 1H NMR (CDCl3),
δ: 1.23 (s, 9 H, But); 5.92 (d, 1 H, H(4), J = 8.5 Hz); 6.13 (d,
1 H, H(6), J = 8.5 Hz); 6.66 (dd, 1 H, H(3), J1 = 8.5 Hz, J2 =
3.0 Hz); 6.86 (br.s, 1 H, OH); 7.03 (d, 1 H, H(1), J = 3.0 Hz);
7.14 (br.s, 4 H, H(2´), H(3´), H(5´), H(6´)); 7.60 (d, 1 H, H(7),
J = 8.5 Hz); 7.73 (m, 2 H, H(10), H(11)); 8.25 (m, 2 H, H(9),
H(12)). IR, ν/cm–1: 3467 (OH); 3010, 2949, 2864 (C—H); 1666
(C=O); 1590, 1514 (C=C). UVꢀVis, λmax/nm (logε): 266 (4.72),
314 (3.63), 405 (3.46), 562 (4.00). Highꢀresolution mass specꢀ
trum, found: m/z 461.1635 [M+]. C30H23NO4. Calculated:
M = 461.1627.
2ꢀtertꢀButylꢀ5ꢀ(5´ꢀtertꢀbutylꢀ2´ꢀhydroxyphenyl)ꢀ5Hꢀ
naphtho[2,3ꢀc]phenoxazineꢀ8,13ꢀdione (2d). M.p. 192—195 °C.
1H NMR (500 MHz, CDCl3), δ: 1.22 and 1.29 (both s, 9 H each,
2 But); 5.94 (d, 1 H, H(3´), J = 8.5); 5.99 (d, 1 H, H(6), J =
8.5 Hz); 6.68 (dd, 1 H, H(4´), J1 = 8.5 Hz, J2 = 3.0 Hz); 6.70 (d,
1 H, H(6´), J = 3.0 Hz); 7.14 (d, 1 H, H(1), J = 3.0 Hz); 7.18 (d,
1 H, H(4), J = 8.5 Hz); 7.31 (d, 1 H, H(7), J = 8.5 Hz); 7.44
(dd, 1 H, H(3), J1 = 8.5 Hz, J2 = 3.0 Hz); 7.59 (td, 1 H, H(10),
J1 = 8.0 Hz, J2 = 2.0 Hz); 7.66 (td, 1 H, H(11), J1 = 8.0 Hz, J2 =
2.0 Hz); 7.75 (br.s, 1 H, OH); 8.00 (dd, 1 H, H(9), J1 = 8.0 Hz,
J2 = 2.0 Hz); 8.05 (dd, 1 H, H(12), J1 = 8.0 Hz, J2 = 2.0 Hz).
IR, ν/cm–1: 3400 (OH); 2960 (C—H); 1660 (C=O), 1590, 1522
(C=C). UVꢀVis, λmax/nm (logε): 266 (4.78), 313 (3.63), 410
(3.46), 560 (4.02). Highꢀresolution mass spectrum, found:
517.2241 [M+]. C34H32NO4. Calculated: M = 517.2253.
Xꢀray diffraction study of compound 2c. Xꢀray diffraction
data were collected on a Bruker P4 diffractometer (MoꢀKα raꢀ
diation, graphite monochromator, 2θ/θꢀscanning technique in
the range 2θ < 50°). A crystal of compound 2c of dimensions
0.60×0.36×0.03 mm was selected. The crystals are monoꢀ
clinic: a = 10.095(2) Å, b = 20.326(5) Å, c = 12.952(4) Å,
β = 110.32(2)°, V = 2492(1) Å3, space group P21/c, Z = 4,
C32H27NO4, dcalc = 1.305 g cm–3, µ = 0.086 mm–1. The intensiꢀ
ties of 4370 independent reflections were measured. The empiriꢀ
cal absorption correction was applied based on azimuthal scans
(the transmission was 0.79—0.98). The structure was solved by
direct methods using the SHELXSꢀ97 program package16 and
refined by the fullꢀmatrix leastꢀsquares method with anisotropic
displacement parameters for nonhydrogen atoms and isotropic
displacement parameters for H atoms using the SHELXLꢀ97
program package.16 The parameters of other H atoms (except
for OH) were calculated in each refinement cycle from the
coordinates of the corresponding carbon atoms. The hydrogen
atom of the hydroxy group at the O(3) atom was located in a
difference electron density map. The final refinement was carꢀ
ried out based on all F 2 to wR2 = 0.1926, S = 0.905, 339 variables

1134
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 6, June, 2007
Klimenko et al.
(R = 0.0734 for 1490 reflections with F > 4σ). The structure
of 2c was deposited at the Cambridge Crystallographic Data
Centre (CCDC, refcode 626170). The Xꢀray diffraction data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/
data_request/cif deposit.
11. F. H. Allen, O. Kenard, D. G. Watson, L. Bramer, A. G.
Orpen, and R. Taylor, J. Chem. Soc., Perkin Trans. 2,
1987, 12, 21.
12. F. H. Allen, Acta Crystallogr., Sect. B, 2002, 58, 380 (Verꢀ
sion 5.27).
13. D. Gigmes, D. Siri, J.ꢀP. Reboul, N. Redouane, P. Tordo,
and G. Pepe, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun., 1998, 54, 822.
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Received January 19, 2007