The 3-substitution of naphthalene-1,2-diones with boronic acids: A C-H functionalization approach to novel spirooxazine photochromics

Article abstract of DOI:10.1016/j.tetlet.2012.02.082

The addition of alkyl and aryl boronic acids to naphthalene-1,2-diones in the presence of an excess of ammonium persulfate and catalytic silver nitrate to yield 3-functionalized naphthalene-1,2-diones is reported. The products of these reactions were then

Full text of DOI:10.1016/j.tetlet.2012.02.082

Tetrahedron Letters 53 (2012) 2226–2230
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Tetrahedron Letters
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The 3-substitution of naphthalene-1,2-diones with boronic acids: a C–H
functionalization approach to novel spirooxazine photochromics
Mark York
CSIRO Materials Science and Engineering, Bag 10, Clayton, Victoria 3169, Australia
Cooperative Research Centre for Polymers, 8 Redwood Drive, Notting Hill, Victoria 3168, Australia
Advanced Polymerik Pty Ltd, 8 Redwood Drive, Notting Hill, Victoria 3168, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
The addition of alkyl and aryl boronic acids to naphthalene-1,2-diones in the presence of an excess of
ammonium persulfate and catalytic silver nitrate to yield 3-functionalized naphthalene-1,2-diones is
reported. The products of these reactions were then further processed to yield the corresponding novel
spirooxazine photochromic dyes.
Received 10 November 2011
Revised 7 February 2012
Accepted 17 February 2012
Available online 24 February 2012
Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
Keywords:
Boronic acid
C–H functionalization
Photochromic
Spirooxazine
Spirooxazines are a commercially important class of photochro-
mic dyes, which upon irradiation with ultraviolet light undergo a
reversible colour change (Scheme 1) from the colourless spirocyclic
form 1 to the coloured merocyanine form 2.1
reaction between naphthalene-1,2-dione and phenylboronic acid
in the presence of ammonium persulfate and silver nitrate gave
40% yield of 3-phenylnaphthalene-1,2-dione,6 with 10% of the
4-phenyl compound (identified from a characteristic singlet at
approximately 6.5 ppm in the 1H NMR spectrum) formed as a minor
product (Scheme 2, R = Ph). As this provided a rapid method for the
formation of the desired 3-substituted naphthalene-1,2-dione pre-
cursors 3, a number of such compounds were prepared (Table 1).
The substitution reaction gave similar yields of the desired
product when performed with either boronic acids (Table 1, entry
1) or boronate esters (Table 1, entry 2), and was successful with
During our research into the synthesis and applications of pho-
tochromic compounds,2 we had reason to prepare a number of
novel spirooxazine dyes based upon a 3-substituted naphtha-
lene-1,2-dione core. A survey of the literature, however, found only
limited methods for the preparation of such naphthoquinones.
Thomson and co-workers reported a method for the formation of
3-phenylnaphthalene-1,2-dione from naphthalene-1,2-dione and
benzene in the presence of stoichiometric palladium(II) acetate.3
This process appeared quite limited in terms of scope and was also
not economically viable. Alternatively, the synthesis of 3-arylnaph-
thalene-1,2-diones via the oxidation of the corresponding phenol
has been reported by Estevez and co-workers.4 Whilst this process
would furnish the desired compounds in a regioselective manner,
it was not judged suitable for the synthesis of a large number of
analogous 3-substituted naphthalene-1,2-dione compounds due
to the need for a separate, multi-step synthesis of each precursor
phenol.
Scheme 1. Mechanics of photochromism of a spirooxazine.
Baran and co-workers reported a C–H functionalization of 1,4-
quinones with boronic acids.5 Within this study an example of
the functionalization of naphthalene-1,2-dione with an arylboronic
acid was provided with the corresponding 4-arylnaphthalene-1,2-
dione being reported as the product. However, in our hands the
E-mail address: Mark.York@csiro.au
Scheme 2. Synthesis of 3-substituted naphthalene-1,2-diones.
0040-4039/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2012.02.082

M. York / Tetrahedron Letters 53 (2012) 2226–2230
2227
Table 1
Synthesis of 3-substituted-naphthalene-1,2-diones
Entry
Naphthalene-1,2-dione
Boronic acid
Product
Yield (%)
1
40
10
2
3
4
44
39
25
5
52
6
7
8
21
0
50
10
9
0

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M. York / Tetrahedron Letters 53 (2012) 2226–2230
Scheme 3. Synthesis of novel spirooxazine photochromics.
Table 2
Synthesis of novel spirooxazine photochromics
Entry
Naphthalene-1,2-dione
Product
Yield (%)
1
48
2
61
3
29
4
67
5
6
48
72
7
62

M. York / Tetrahedron Letters 53 (2012) 2226–2230
2229
naphthalene-1,2-dione side product could also be transformed into
the corresponding spirooxazine (Table 2, entry 7).
In order to perform a preliminary evaluation of the photochro-
mic performance of the novel compounds 6a to 6f and 7, test
lenses were prepared using a matrix composed of polyethylenegly-
col 400 dimethacrylate and bisphenol A ethoxylate dimethacrylate
in a 1:4 weight ratio with 0.4% AIBN by mass as initiator.
1.2 ꢀ 10ꢁ6 mol of spirooxazine per gram of matrix was thoroughly
mixed into the lens matrix and the lenses thermally cured before
irradiation at 365 nm with a handheld UV source. The lenses after
irradiation can be seen in Figure 2.
The compounds display predominantly blue colouration of
varying shades with photochromic 6d displaying green colouration
in common with other known spirooxazines derived from 4-aryla-
mino substituted naphthalene-1,2-diones.2d,9 Interestingly, dibutyl
spirooxazine 6e displayed purple colouration similar to that ob-
served for spirooxazines derived from 4-amino substituted naph-
thalene-1,2-diones.2a,10
In summary, the convenient one-step synthesis of a number of
3-substituted naphthalene-1,2-diones is reported from the corre-
sponding naphthalene-1,2-diones and boronic acids. These com-
pounds were used to synthesize a range of novel spirooxazine
photochromic dyes with colours ranging from purple to green.
Figure 1. X-ray structure of novel spirooxazine 6f.
Acknowledgments
The author thanks the Co-operative Research Centre for Poly-
mers, Advanced Polymerik Pty Ltd and CSIRO Materials Science
and Engineering for their support.
arylboronic acids bearing either electron-donating or electron-
withdrawing groups (Table 1, entries 3 and 4). A 4-substituted
naphthalene-1,2-dione was also a suitable substrate for the pro-
cess, giving the corresponding 3,4-disubstituted naphthalene-1,2-
dione in moderate yield (Table 1, entry 5). Alkylboronic acids
underwent the reaction, but in this case the 3,4-dialkylated
naphthalene-1,2-dione was the major product (Table 1, entry 6).
Despite this observation, attempts to functionalize 3-arylnaphtha-
lene-1,2-dione in the 4-position with an alkylboronic acid gave
only unreacted starting material (Table 1, entry 7). Aryl bromide
substituents were tolerated (Table 1, entry 8) providing another
possible point of diversity via cross-coupling reactions. Reaction
with thiophene-3-boronic acid failed to give any of the expected
product, possibly as a result of the consumption of oxidants by
the in situ oxidation of the thiophene ring system (Table 1, entry
9). In some cases isolation of the corresponding 4-substituted
naphthalene-1,2-dione minor product was possible (Table 1,
entries 1 and 8, compounds 4a and 4b).
Supplementary data
Supplementary data (experimental procedures and data for all
new compounds) associated with this article can be found, in the
online version, at doi:10.1016/j.tetlet.2012.02.082.
References and notes
1. (a) Lokshin, V.; Samat, A.; Metelitsa, A. V. Russ. Chem. Rev. 2002, 71, 893–916;
(b) Bouas-Laurent, H.; Durr, H. Pure Appl. Chem. 2002, 73, 639–665.
2. (a) Evans, R. A.; York, M. Tetrahedron Lett. 2010, 51, 2195–2197; (b) Ali, A.;
Campbell, J. A.; Evans, R. A.; Malic, N.; York, M. Macromolecules 2010, 43, 8488–
8501; (c) Evans, R. A.; Hanley, T. L.; Skidmore, M. A.; Davis, T. P.; Such, G. K.;
Yee, L. H.; Ball, G. E.; Lewis, D. A. Nat. Mater. 2005, 4, 249–253; (d) Evans, R. A.;
York, M. Synth. Commun. 2010, 40, 3618–3628.
3. Mackenzie, N. E.; Surendrakumar, S.; Thomson, R. H.; Cowe, H. J.; Cox, P. J. J.
Chem. Soc., Perkin Trans. 1 1986, 2233–2238.
The substituted naphthalene-1,2-diones 3 were then treated
with hydroxylamine hydrochloride to yield the corresponding ni-
troso naphthol 5, which on heating with 1,3,3-trimethyl-2-methy-
lene indoline gave the desired spirooxazine photochromics 6
(Scheme 3 and Table 2).7
The 3-substituted naphthalene-1,2-diones (3a–e, g) gave the
corresponding spirooxazine compounds in moderate yields
(Table 2, entries 1–6). The regiochemistry of both boronic acid
addition and subsequent oxime formation was confirmed by
X-ray crystallography of crystalline spirooxazine 6f (Fig. 1).8 When
isolated from the initial addition reaction, the 4-substituted
4. Martínez, A.; Fernández, M.; Estévez, J. C.; Estévez, R. J.; Castedo, L. Tetrahedron
2005, 61, 485–492.
5. Fujiwara, Y.; Domingo, V.; Seiple, I. B.; Giantassio, R.; Del Bel, M.; Baran, P. S. J.
Am. Chem. Soc. 2011, 133, 3292–3295.
6. Experimental procedure:
A
mixture of naphthalene-1,2-dione (2.00 g,
12.65 mmol), phenylboronic acid (2.31 g, 18.97 mmol), (NH4)2S2O8 (8.66 g,
37.90 mmol) and AgNO3 (0.43 g, 2.53 mmol) in 1,2-dichloroethane (40 mL) and
H2O (30 mL) was stirred in an open flask for 2.5 h. A further portion of AgNO3
(0.43 g, 2.53 mmol) was then added and the mixture stirred for a further 2.5 h
before dilution with CH2Cl2 (100 mL) and H2O (100 mL). The organic phase was
separated, washed with 10% w/v Na2CO3 solution (100 mL), filtered through
Celite, dried (MgSO4) and evaporated in vacuo. The residue was purified by
column chromatography eluting with 0–10% v/v EtOAc/petroleum ether to give
3-phenylnaphthalene-1,2-dione (3a) as a red solid (1.18 g, 40%). Also present
Figure 2. Novel spirooxazine compounds 6a–f and 7 after UV irradiation.

2230
M. York / Tetrahedron Letters 53 (2012) 2226–2230
was 4-phenylnaphthalene-1,2-dione (4a) (0.30 g, 10%). The spectral data of
127.0, 124.5, 121.5, 121.2, 119.7, 106.8, 98.1, 50.9, 29.7, 25.3, 21.2; HRMS (EI)
calcd for C28H24N2O [M+]: 404.1888, found: 404.1888.
both compounds were in accordance with those reported previously.3
7. Experimental procedure: A mixture of 3-phenylnaphthalene-1,2-dione (0.40 g,
1.71 mmol) (3a) and hydroxylamine hydrochloride (0.24 g, 3.42 mmol) in EtOH
(15 mL) was stirred at room temperature for 18 h. The mixture was then
evaporated in vacuo, suspended between CH2Cl2 (30 mL) and H2O (30 mL), the
organic phase separated, dried (MgSO4) and evaporated in vacuo. The
residue was suspended in EtOH (10 mL), treated with 1,3,3-trimethyl-2-
8. Crystallographic data (excluding structure factors) for 50-(4-bromophenyl)-
1,3,3-trimethylspiro[indoline-2,30-naphtho[2,1-b][1,4]oxazine] (5f) have been
deposited with the Cambridge Crystallographic Data Centre as supplementary
publication no CCDC 850790. Copies of the data can be obtained, free of charge,
on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44
(0)1223 336033 or email: deposit@ccdc.cam.ac.uk).
methyleneindoline (0.385 g, 2.22 mmol) and heated in
a
sealed tube at
9. Clarke, D.; Heron, B. M.; Gabbut, C. D.; Hepworth, J. D.; Partington, S. M.; Corns,
S. N. U.S. 6303,673; 2001, Chem. Abstr. 2003, 139, 296689.
100 °C for 3 h. The mixture was evaporated in vacuo and the residue purified
by column chromatography eluting with 0–10% v/v EtOAc/petroleum ether to
give 1,3,3-trimethyl-50-phenylspiro[indolin-2,30-naphtho[2,1-b][1,4]oxazine]
10. (a) Rickwood, M.; Marsden, S. D.; Ormsby, M. E.; Staunton, A. L.; Wood, D. W.;
Hepworth, J. D.; Gabburr, C. D. Mol. Cryst. Liq. Cryst. 1994, 246, 17–24; (b)
Koshkin, A. V.; Lokshin, V.; Samat, A.; Gromov, S. P.; Fedorova, O. A. Synthesis
2005, 1876–1880; (c) Koshkin, A. V.; Fedorova, O. A.; Lokshin, V.; Guglielmetti,
R.; Hamelin, J.; Texier-Boullet, F.; Gromov, S. P. Synth. Commun. 2004, 34, 315–
322; (d) Pang, M. L.; Zhang, H. J.; Liu, P. P.; Zou, Z. H.; Han, J.; Meng, J. B.
Synthesis 2010, 20, 3418–3422.
(6a) as
a d 8.60 (d,
green gum (0.33 g, 48%). 1H NMR (CDCl3, 400 MHz)
J = 9.5 Hz, 1H), 7.84–7.79 (m, 3H), 7.61 (t, J = 8.3 Hz, 1H), 7.49–7.43 (m, 3H),
7.26–7.13 (m, 4H), 7.01 (d, J = 7.3 Hz, 1H), 6.86 (t, J = 7.4 Hz, 1H), 6.54 (d,
J = 7.8 Hz, 1H), 2.75 (s, 3H), 1.28 (s, 3H), 1.26 (s, 3H); 13C NMR (CDCl3, 50 MHz)
d 149.9, 147.2, 141.5, 136.5, 135.9, 130.2, 129.7, 129.2, 129.0, 127.8, 127.2,