The synthesis and fluorescence of novel N-substituted-1,8-naphthylimides

Article abstract of DOI:10.1002/jhet.5570450216

(Chemical Equation Presented) The synthesis and characterisation of a series of novel 4-acylamino and 4-alkylamino-N-1,8-naphthalimides is described. The UV-visible absorption and emission properties of the compounds are reported. Significant solvent effects are noted for 4-n-butyl-9-n-butyl-1,8- naphthylimide. The incorporation of acetyl and chloroacetyl groups into the 4-substituent markedly increases the fluorescence quantum yield compared with 4-alkylamino substituemnts.

Full text of DOI:10.1002/jhet.5570450216

Mar-Apr 2008
397
The Synthesis and Fluorescence of Novel N-Substituted-1,8-
naphthylimides
Dongwu Yuan1 , Robert G Brown1, John D Hepworth1, Michael S Alexiou2
and John H. P. Tyman2*
1School of Chemistry, University of Central Lancashire, Preston, Lancs. and 2Department of Chemistry, Brunel
University, Uxbridge, Middlesex, UB8 3PH; jhptyman@hotmail.com
Received May 4, 2007
R
O
N
O
NHCOR1
The synthesis and characterisation of a series of novel 4-acylamino and 4-alkylamino-N-1,8-
naphthalimides is described. The UV-visible absorption and emission properties of the compounds are
reported. Significant solvent effects are noted for 4-n-butyl-9-n-butyl-1,8-naphthylimide. The
incorporation of acetyl and chloroacetyl groups into the 4-substituent markedly increases the fluorescence
quantum yield compared with 4-alkylamino substituemnts.
J. Heterocyclic Chem., 45, 397 (2008).
INTRODUCTION
RESULTS AND DISCUSSION
The photochemistry and photophysics of the
alkylaminonaphthalic-1,8-N-alkylimides continues to be
of wide interest in technical, medical and electronic fields.
In addition to their application in non-destructive testing
(NDT) in metals and ceramics [1,2], laser applications
[3,4], for sensors and switches [5-7], probes in cancer
studies [8,9] and for their anti-viral activity [10-13], more
recent research has highlighted their potential as
electroluminescent materials [14-17] and as fluorescent
sensors for metal ions [18-26].
The synthesis and fluorescence properties of a variety
of N-alkylsubstituted-1,8-naphthalimides have been
described [27,28] and one former aspect by others [7].
Methods of synthesis involving nucleophilic displacement
of the nitro group [29] and developments with chloro and
bromo analogues have been reported [30]. The role of
structure has been fully examined in the case of
monosubstituted [1] and extended to studies on
disubstituted compounds [31,32].
Substitution and Nucleophilic reactions. The reaction
routes and compounds synthesised are depicted in
Schemes 1 and 2. Scheme 1 gives the synthesis of
compounds (3) and (4) from 4-nitronaphthalic anhydride
1 by way of reduction to 4-aminonapthalic anhydride (2).
Compound (5) results from replacement both of the 4-
nitro group and at the anhydride. Compound (6) is
obtained from 4-aminonaphthalic anhydride by reaction
first at the anhydride and then by acylation of the amino
group. Compound (8) is also derived from 4-amino-
naphthalic anhydride (2) by reaction first at the anhydride
and (9) by acylation of the OH and the amino groups of
(8). Compound (13) is formed from reaction of the
anhydride group of (1), and (14) by reduction of (13).
Dependent on the value of number of methylene groups,
n, in the reactant, compound (14) can be obtained either
directly from 4-aminonaphthalic anhydride (2) or from
(1). Scheme 2 depicts the synthesis of compounds (10),
(11), and (12) by reaction first at the anhydride group of 1
and then at the nitro group by nucleophilic displacement.
Compounds (15) and (16) result from a similar procedure
except that an amino acid intermediate is used instead of
an amino alcohol. Hydrolysis of (16 affords the acid (17).
Reaction of 4-nitronaphthalic anhydride (1) and its 4-
aminonaphthalic derivative (2) with amines occurred
preferentially at the anhydride group to give 9-substituted
1,8-naphthalimides through a ring-opening and closing
sequence. Displacement of a 4-nitro group by amines only
occurs in aprotic solvents. DMF was employed in the
present work although in later studies the use of N-
methylpyrrolidinone [30] (NMP) is preferred since side-
In the present investigation, directed partly to devising
water-soluble compounds, a number of novel 4-alkyl-
amino-N-alkylnaphthalimides (with similar 4- and 9-alkyl
groups a series of 4-nitro-N-alkylaminonaphthalimides
and a range of 4-amino-N-alkylnaphthalic-1,8-imides
have been synthesized. Previously, substitution at the 4-
and 9- positions by alkylamino groups has been
investigated, but in the present work carboxyalkyl-,
sulphoalkyl-, halogenoalkylcarboxy- and ethoxycarbonyl-
alkylamino substituents have been introduced to study the
role played by electron attracting groups. Fluorescence
measurements have revealed novel properties.

398
D. Yuan , R. G Brown, J. D. Hepworth, M. S. Alexiou and J. H. P. Tyman
Vol 45
Scheme 1
(CH2)nOR
R
N
R
N
O
N
O
O
O
O
O
i
NH(CH2)nOR1
NH2
NHCOR1
(5a, R = H, n = 2,3,4)
(5b, R = SO3H, n = 2,4)
(6, R = Et. Bu)
(7, (a) R1 = CH2Cl; R = Bu
(b) R1 = CH= CHCO2H(Z), R = Et)
x
x
(CH2)nCO2H
O
O
O
O
O
O
O
O
O
O
N
O
iii
iv
v
iv
14
(n = 1,2)
NO2
NH2
NHAc
NHAc
(1)
(2)
(3)
(4)
iii,
vi
viii
vi
vi
(CH2)nCO2H
(CH2)nCO2H
(CH2)2OH
(CH2)2OCOCH2Cl
O
N
O
O
N
O
O
N
O
O
N
O
ix
NO2
NH2
NH2
NHCOCH2Cl
(13, n = 2,3,4)
(14, from 13, n = 1,2,3;
(8)
(9)
from 2, n = 1,2)
Reagents: (i)(a) ClCH2COCl, DMF. (b) (COCH=CHCO)O. (ii) RNH2,DMF. (iii) SnCl2,MeOH, HCl. (iv) Ac2O, Py. (v) NH2CH2CO2Na, DMF;
HCl. (vi) NH2(CH2)nCO2H, EtOH, (vii) n = 1, 2 NH2(CH2)nCO2H, DMF. (viii) NH2(CH2)2OH, DMF. (ix) ClCH2COCl, NEt3. (x) (a) R = H,
NH2(CH2)nOH, DMF, heat; (b) n = 2; H2SO4; n = 4, H2SO4; KOH.
Scheme 2
(CH2)2OH
(CH2)2OH
(CH2)2OCOCH2Cl
O
O
O
O
N
O
O
N
O
O
N
O
xi
xi
x
NO2
NO2
NHBu
NHBu
(1)
(10)
(11)
(12)
xii
CH2CO2Et
CH2CO2Et
CH2CO2H
O
N
O
O
N
O
O
N
O
xi
xiii
NO2
NHBu
NHBu
(15)
(16)
(17)
Reagents: (ix), ClCH2COCl, NEt3, (x) NH2(CH2)OH, EtOH. (xi), BuNH2,DMF, heat. (xii) NH2CH2CO2Et, EtOH. (xiii) KOH; HCl.
reactions such as the formation of a 4-dimethylamino
derivative are greatly reduced. Displacement of the halide
ion from 4-halogenonaphthalic anhydrides can offer
advantages over the 4-nitro compound in the work-up
procedure [30] and enable products to be purified by
crystallisation rather than chromatography. In the present
work the formation of 4-dimethylamino impurities was
minimal possibly because the reactions were carried out at
75-80°C rather than 100-120°C. These considerations do
not apply to compounds having a 9-imidic function.
Attempts to use 4-nitronaphthalic anhydride in aprotic
solvents (DMF, DMSO) with the weak nucleophile

Mar-Apr 2008
The Synthesis and Fluorescence of Novel N-Substituted-1,8-naphthylimides
399
bromobenzoyl derivatives of
compound [41], the presence of such halogen substituents
in the conjugation depressed fluorescence intensity.
a
4,4'-diaminostilbene
sodium glycinate, en route to similar groups at the 4- and
9-positions led to complex mixtures. Glycine esters were
little better and reminiscent of the behaviour of taurine
[28]. Accordingly, for the introduction of electron-
attracting groups at 4- and 9-positions, 4-amino-1,8-
naphthalimide (2) was used as the substrate. Acetylation
afforded the acetyl derivative (3) and reaction with
sodium glycinate gave the carboxymethyl compound (4,
n=1) in excellent yield, which possesses outstanding
fluorescent properties. Compound (4, n=1) is also
accessible from 4-aminonaphthalic-1,8-anhydride by
direct reaction with glycine to give (14, n=1) followed by
acetylation and from 4-nitronaphthalic-1,8-anhydride and
glycine in ethanol to afford (13, n =1) followed by
reduction with tin (II) chloride to (14, n =1) and
acetylation.
Enhancement of the influence of electron-attracting
properties of the substituents, involved the chloroacetyl-
ation of 4-amino-(9-n-butyl)-1,8-naphthalimide (6) and
of 4-amino-(2-hydroxyethyl)-1,8-naphthalimide (8) to
give compounds (7a) and (9) respectively. The major
enhancement of fluorescence properties appears to
come from the 4- rather than the 9-substituent, since
compound (16) possessed only moderate properties.
Increased aqueous solubility was conferred on the
compounds by the introduction of a sulphonic group as
in (5b, R = SO3H, n = 2,4) although these were only
obtained in low yield.
The fluorescence of FBYR is highly solvent dependent
(Table1). Both the longest wavelength absorption band
and the fluorescence emission maximum are shifted to
longer wavelength with increasing solvent polarity, as
anticipated for a charge-transfer transition. The absorp-
tion maxima of the second and third absorption
transitions are relatively unaffected by the solvent. The
highest fluorescence intensity is observed in ethyl acetate
solution and the lowest in methanol although it dropped
almost to zero in aqueous conditions. All of the
fluorescence decays were clean single exponentials.
Calculation of radiative (kr) and non-radiative (knr) rate
constants (Table 1) reveals that the decreased fluores-
cence intensity in polar solvents derives from both a
decrease in the radiative rate constant and an increase in
the non-radiative one. However, the large increase in knr
for methanol compared to the other alcohols may also be
a result of quenching of the excited state by solvent
clusters as proposed previously for aqueous solutions of
other amino-1,8-naphthalimides [43] and the role of
hydrogen bonding. This last mechanism would also
explain the virtually nil emission intensity for FBYR in
water. By way of an alternative explanation [44], the
formation of exciplexes between FBYR and protic
solvents may account for both the decrease in kr and the
increase in knr in the three alcohols used here. It is
interesting to note that Krystkowiak [44] also observed a
decrease in kr by a factor of 2.5 for 4-aminophthalimide
in hexafluoroisopropanol, water and deuterated water.
Fluorescence Properties of the 1,8-Naphthylimides.
The incorporation of polar groups at the 4- and 9-
positions of 1,8-naphthylimides not only resulted in
increased water solubility but also produced compounds
Table 1
Effect of solvent on the fluorescence of 4-n-butylamino-9-n-butyl-1,8-naphthalimide.
Solvent
Absorption
(nm)
maxima λex
(nm)
λem
φf
τf
kr
Knr
(nm)
470
479
500
512
522
523
523
(ns)
9.40
8.85
9.50
10.57
9.63
8.95
8.24
x10-8 s-1
1.09
1.00
0.98
0.82
0.69
0.67
0.46
X10-8 s-1
0.22
0.19
0.07
0.16
0.35
0.38
0.75
Methylcyclohexane
Toluene
Ethyl acetate
Acetonitrile
2-Propanol
Ethanol
264, 272, 410
263, 286, 420
260, 280, 428
260, 280, 432
260, 284, 440
260, 284, 442
260, 284, 442
410
420
428
432
442
442
442
0.83
0.84
0.93
0.84
0.66
0.66
0.38
Methanol
λex and λem are the excitation wavelength and the maximum of the fluorescence emission respectively.
with high fluorescence intensities. This effect appears to
be a consequence of the electron-withdrawing nature of
the substituents. This behaviour contrasts with that of
previously studied naphthalimides, notably 4-n-
butylamino-9-(n-butyl)-1,8-naphthalimide (FBYR), in
which the substituents possess electron-releasing
character. Similar properties have been observed [8] in the
compound (7, R = (CH2)3Br, R1 =Me) in which however
the halogen atom is remote from active electronic
involvement. From our work with 4-chlorobenzoyl and 4-
The fluorescence properties of the synthesised and
novel 1,8-naphthalimides in ethanol solution are shown in
Table 2 along with data for FBYR. The absorption and
fluorescence properties of the compounds reported in
Table 2 divide naturally into two groups. Compounds (5),
(14) and (16) are similar to FBYR in their properties
while compounds (4), (7) and (9), despite the presence of
the amino function at the 4-position, resemble the
properties of naphthalimides lacking
substituent [27].
a
4-amino

400
D. Yuan , R. G Brown, J. D. Hepworth, M. S. Alexiou and J. H. P. Tyman
Vol 45
Table 2
Fluorescence properties of 4,9-disubstituted-1,8-naphthalimides (in ethanol).
Compound
Absorption
maxima(nm)
Extinction
(log10ε)
λex
(nm)
λem
(nm)
φf
τf
(ns)
kr
knr
x10-8 s-1
x10-8 s-1
Coefft.
FBYR
5a, n=3
5a, n=4
5b, n=2
14, n=1
14, n=2
14, n=3
16
260(4.29) 284(4.25) 442
442(4.20)
262(4.61) 284(4.31) 444
444(4.46)
262(4.31) 284(4.31) 444
444(4.22)
523
526
525
525
540
537
537
543
0.66
0.55
0.62
0.69
0.46
0.50
0.54
0.64
8.95
8.76
9.00
7.13
8.88
8.88
8.78
8.94
0.67
0.63
0.69
0.97
0.52
0.58
0.62
0.72
0.38
0.51
0.42
0.43
0.61
0.58
0.52
0.40
258(3.86)
436
282(3.83) 436(3.94)
260(4.21)
434(4.09)
258(4.28)
434(4.09)
258(4.30)
434(4.25)
274(sh) 434
274(sh) 434
274(sh) 434
256(3.97) 284(4.07) 442
442(4.11)
4
238(4.45) 364(4.19)
238(4.41) 360(4.14)
242(4.46) 382(4.21) 382
238(4.38) 360(4.08) 360
364
360
454
454
518
454
0.94
0.91
0.01
0.88
7.03
6.59
1.49 / 8.12
6.67
1.34
1.38
-
0.09
0.14
-
7a
7b
9
1.32
0.18
λex and λem are the excitation wavelength and the maximum of the fluorescence emission respectively; sh, shoulder.
effect of the CH=CHCO2H group which may exert a
negative effect as found with 4-phenylamino and 4-nitro
substituents; and linear conjugation with the
naphthalimide ring then results in a major loss of
fluorescence. It would be of interest to examine the
succinoyl analogue having a CH2CH2CO2H group lacking
conjugation, but this opportunity was not available.
Distal hydroxy groups as in compounds (5a, n = 3 and
4), have little effect on fluorescence intensity relative to
that of FBYR. This is in contrast to the quenching effect
of distal nitrogen atoms at the 4- position [18] and the 9-
position [45] (although the quenching effect is much
smaller in the latter). The ethoxycarbonyl group in
compound (16) also has similar properties to FBYR as
does (5b, n=2), although the terminal sulphonic group
greatly increases solubility in water with little effect on
the absorption and fluorescence properties. By contrast,
acetyl and chloroacetyl groups as in compounds (4), (7a)
and (9) enhance the fluorescence intensity and also alter
the colour of the emission relative to FBYR. A primary
amino group as in (14), although assisting fluorescence is
much less effective than an alkylamino group as in
compound 16.
It is noticeable that although the lowest energy
absorption maximum of (7b) in ethanol is similar to that
of naphthalimides which do not have
a 4-amino
substituent [27], the emission maximum is close to that of
FBYR. This observation suggests that in the emissive
excited state the 4-amino substituent is conjugated with
the ring. The double exponential fluorescence kinetics
therefore reflect the twisting process necessary to convert
the initially excited state into the emissive state.
Thus, the major influence on increase of the
fluorescence intensity arises from incorporation of acetyl
and chloroacetyl groups into the 4-amino substituent,
These two electron-withdrawing groups alter the
behaviour of the 4-amino function as observed in FBYR.
Although we have no supporting evidence, it is possible
that the carbonyl group of the acetyl function forms a
hydrogen-bond to the 3-H atom creating a new stabilising
six-membered ring which may partially increase the
conjugation of the whole system. The hydrogen atoms of
the NH and at the peri-position do not sterically interact
and obstruct coplanarity.
EXPERIMENTAL
UV/visible absorption spectra were measured on a Perkin-
Elmer Lambda 3 spectrophotometer and a Hewlett Packard
8452A diode array instrument in 1 cm quartz cells at ambient
temperature with concentrations 10-4-10-5 mol dm-3. Fluorescence
spectra were recorded on a Perkin-Elmer LS-5 Luminescence
spectrometer and a SPEX Fluoromax spectrofluorimeter in
corrected mode. Quantum yield measurements were made on
optically dilute samples which were deoxygenated by bubbling
with oxygen-free nitrogen for 30 min. Fluorescein in 0.1 mol
dm-3 sodium hydroxide (φf = 0.90) [33] or quinine sulphate in
0.1 mol dm-3 perchloric acid (φf = 0.55) [34] were used as
quantum yield standards. Fluorescence lifetimes were measured
by the technique of time-correlated single-photon counting [35]
at the Synchroton Radiation source in the SERC Daresbury
The negligible fluorescence of (7b) could be ascribed to
loss of coplanarity as for a 4-dimethylamino substituent
[27], which is twisted out of plane, or due to an electronic

Mar-Apr 2008
The Synthesis and Fluorescence of Novel N-Substituted-1,8-naphthylimides
401
laboratory [36]. Infrared spectra were recorded on a Galaxy
series FTIR 3000, Mattson Polaris FTIR and Perkin-Elmer 1310
spectrometers. Proton nuclear magnetic resonance spectra were
obtained on a Bruker WM250 cryospectrometer and on a Hitachi
R-1100 instrument. Mass spectra were determined on a modified
AEI MS902 instrument. Accurate masses were determined by
the EPSRC centre at the Chemistry Department, University of
Wales at Swansea. Thin layer chromatography (TLC) was
carried out on silica gel GF254. High performance liquid
chromatography (HPLC) was affected with the aid of a Perkin
Elmer UV variable wavelength spectrometer (LC55) equipped
with a flow through cell. Microanalyses were carried out in the
Microanalytical Department, University of Manchester.
Commercial compounds used for absorption and fluorescence
measurements were obtained from Molecular Probes Inc., and
chemicals for organic synthesis from the Aldrich Chemical Co.
5-Nitroacenaphthene mp 101-102 °C and 3-nitroacenaph-
thene, mp 147-148 °C were prepared in 72% and 20% yields
respectively as previously described [37,38]. 4-Nitronaphthalic
anhydride (1), mp 227-228 °C in 33% yield was obtained by
oxidation of 5-nitroacenaphthene [39]. 4-Aminonaphthalic-1,8-
anhydride (2), mp > 360 °C was prepared from the nitro
compound by reduction with stannous chloride [27].
4-Acetylaminonaphthalic-1,8-anhydride (3), mp 283-285 °C was
obtained by acetylation of the amino compound [40]. The
compounds synthesis are depicted in Schemes 1 and 2.
203-204°C; ir: (nujol), 3340 (NH), 1675, 1625 (C=O), 1580
(C=C), 775, 755 (ArCH bend) cm-1; 1H nmr (DMSO-d6): δ,
1.45-1.74 (8H, m, 2x (CH2)2CH2OH), 3.36-3.46 (6H, m,
NHCH2(CH2)2CH2 and NCH2(CH2)2CH2), 3.98-4.04 (2H, t, J
6.9Hz, NCH2), 4.39-4.51 (2H, dt, 2xOH,.exch.), 6.75-6.78 (1H,
d, J 8.7Hz, 3-H), 7.63-7.69 (1H, t, J 7.9Hz, 6-H), 7.79 (1H, br.,
NH, exch.), 8.23-8.26 (1H, d, J 8.5Hz, 2-H), 8.38-8.70 (2H, m,
5-H and 7-H). Anal. Calcd.for C20H24N2O4: C, 67.3; H, 6.8; N,
7.8%. Found: C, 66.9; H, 6.8; N. 7.8.
4-(2-Sulphatoxyethylamino-9-(2-sulphatoxyethyl)-1,8-naph-
thalimide (5b, n = 2;R = SO3H). 4-(2-Hydroxyethylamino)-9-
(2-hydroxyethyl)-1,8-naphthalimide, (prepared as described
[28]) (0.50 g, 1.7 mmol), was stirred with 98% conc. sulphuric
acid (20 mL) at 2-4°C for 18 h. The solution was diluted with
water at 0° and kept at that temperature for 3 h when a
precipitate formed which was filtered and the solid washed with
isopropanol and methanol. The solid was dissolved in hot water
and ethanol, cooled to 4°C, and isopropanol added to give a
precipitate which was collected by filtration to give orange
crystals of the product (0.43g, 55%), mp > 300°C (decomp); ir:
(nujol), 3389 (NH), 1680,1640 (C=O), 1575 (C=C), 1211, 1017
1
(S=O), 780, 782 (ArCH bend).cm-1; H nmr (D2O): δ, 3.36-3.85
(6H, tt, NCH2CH2 and NHCH2CH2), 4.23-4.28 (2H, t, J 4.6Hz,
NCH2CH2), 5.94-5.98 (1H, d, J 8Hz, 3-H), 6.83-6.86 (1H, t, J
7.8Hz, 6-H), 7.17-7.20 (1H, d, J 8Hz, 2-H), 7.25-7.29 (2H, dd,
5-H and 7-H).
4-Acetamido-1,8-naphthalic anhydride (3), (spectral
properties not previously decribed).
Dipotassium 4-(Sulphatoxybutylamino-9-(4-sulphatoxy-
R = SO3K). 4-(4-
A
mixture of 4-
butyl)-1,8-naphthalimide (5b, n=4,
aminonaphthalic anhydride (0.50 g, 2.3 mmol), glacial acetic
acid (1 mL, 17.0 mmol), and pyridine (4 mL, 50.0 mmol) was
refluxed for 1 h. After the addition of acetic anhydride (8 mL,
84.0 mmol) the yellow mixture became brown and refluxing was
continued for 3 h. The cooled mixture was diluted with water
(100 mL) and the grey precipitate filtered and the product
crystallised (acetic acid) to give the acetate, (yield, 43%), mp
283-285 °C (lit., [30] 282-283 °C); ir, (nujol), 3574,3380 (NH),
1773, 1711 (C=O), 1586 (C=C), 777, 751 (ArCH bend) cm-1; 1H
nmr, (DMSO-d6),δ, 2.27 (3H, s, Me), 7.89-7.95 (1H, t, J 8.0Hz,
6-H), 8.27-8.30 (1H, d, J 8.1Hz, 3-H), 8.48-8.79 (3H, m, 2-H, 5-
H and 7-H).
Synthesis of 4,9-Disubstituted 1,8-Naphthalimides. 4-(3-
Hydroxypropylamino)-9-(3-hydroxypropyl)-1,8-naphthal-
imide (5a, n = 3; R = H). A solution of 4-nitronaphthalic
anhydride, 1 (2.43 g, 10.0 mmol) and 3-hydroxypropylamine
(3.375 g, 45.0 mmol) in dimethylformamide (40 mL) was stirred
and heated under nitrogen until TLC indicated complete
reaction. The reaction mixture was cooled and diluted with
water. The precipitate was collected by filtration and crystallised
from ethanol and obtained as yellow needles, (yield, 70%), mp
210-211 °C.; ir: (nujol), 3340 (NH), 1675, 1630, 1580 (C=C),
775, 760 cm-1; 1H nmr: (DMSO-d6), δ, 1.70-1.92 (4H, m,
NHCH2CH2 and NCH2CH2), 3.14-3.61 (6H, m, NHCH2CH2CH2
and NCH2CH2CH2), 4.03-4.09, (2H, t, J 7.2Hz, NCH2), 4.46-
4.66 (2H, m, 2OH, exch.), 6.75-6.79 (1H, d, J 9Hz, 3-H), 7.63-
7.69, (1H, t, J 7.6Hz, 6-H), 7.73-7.78 (1H, br., NH, exch.), 8.23-
8.27, (1H, d, J 9Hz, 2-H), 8.40-8.68 (2H, m, 5-H and 7-H). Anal.
Calcd. for C18H20N2O4 : C, 65.8; H, 6.2; N, 8.5..Found: C, 65.4;
H, 6.4; N, 8.3.
Hydroxybutylamino)-9-(4-hydroxybutyl)-1,8-naphthalimide (0.5
g, 1.4 mmol) in 98% concentrated sulphuric acid (10 mL) was
stirred at 2-4°C for 24 h, then diluted with water (250 cm3),
neutralised with potassium hydroxide, and kept at 2-4°C for 12
h, when the salt was precipitated. The precipitate was collected
by filtration, extracted with ethanol and the extract dried to give
orange crystals of the product (0.04 g, 6%), mp 178-184°C
which contained traces of inorganic salts; ir (nujol): 3441, 3319
(NH), 1678, 1631 (C=O), 1581 (C=C), 1361, 1190 (S=O), 774,
1
757 (ArCH bend). cm-1; H nmr (DMSO-d6/CDCl3): δ 1.48-1.85
(8H, m, CH2CH2CH2CH2), 3.26-3.57 (6H, m, NCH2
CH2CH2CH2 and NHCH2CH2CH2CH2), 4.00-4.05 (2H, t, J
7.1Hz, NCH2), 6.53-6.56 (1H, d, J 8.4Hz, 3-H), 7.41-7.47 (1H, t,
J 7.6Hz, 6-H), 8.23-8.41 (3H, m, 2-H, 5-H and 7-H).
4-Acetamido-9-carboxymethyl-1,8-naphthalimide (4;
n
=1). 4-Acetamido-1,8-naphthalic anhydride (0.2 g, 0.8 mmol)
and sodium glycinate (0.4 g, 0.8 mmol) in dimethylformamide
(10 mL) were heated at 80°C for 3 h under a nitrogen
atmosphere at which point TLC indicated that no reaction had
taken place. The heating was continued at 120°C for 2 h and
finally, to complete reaction, at 140°C for 13 h. The cooled
mixture was diluted with water and acidified to afford a
precipitate which was collected by filtration and crystallised
(ethanol), to give yellow crystals (0.16 g, 64%), mp > 315°C
(decomp.); ir (nujol): 3389, 3260 (NH), 1725, 1669 (C=O), 1598
1
(C=C),788,761 (ArCH bend) cm-1; H nmr (DMSO-d6): δ, 2.26
(3H, s, Me), 4.69 (2H, s, CH2), 7.83-7.89 (1H, t, J 7.9Hz, 6-H),
8.19-8.23 (1H, d, J 8.1Hz, 3-H), 8.42-8.64 (3H, m, 2-H, 5-H and
7-H). Anal. Calcd. for C16H12N2O5: C, 61.5; H, 3.9; N, 9.0.
Found: C, 61.7; H, 4.0; N, 9.0.
4-(4-Hydroxybutylamino)-9-(4-hydroxybutyl)-1,8-naph-
thalimide (5a, n = 4; R = H). This compound was prepared in a
similar way from 4-nitronaphthalic anhydride and 4-
hydroxybutylamine to give, yellow needles, (yield, 54%), mp
4-Chloroacetamido-9-(n-butyl)-1,8-naphthalimide (7a, R =
Bu, R1 = CH2Cl). Chloroacetyl chloride (0.13 g, 1.12 mmol) in
dimethylformamide (2 mL) was added dropwise to 4-amino-9-
(n-butyl)-1,8-naphthalimide (0.15 g, 0.56 mmol) in dimethyl-

402
D. Yuan , R. G Brown, J. D. Hepworth, M. S. Alexiou and J. H. P. Tyman
Vol 45
formamide (10 mL) containing triethylamine (0.11 g, 1.12
mmol) cooled in an ice/water bath. The reaction mixture was
stirred at ambient temperature for 10 h when TLC indicated
partial reaction. Further chloroacetyl chloride (0.26 g, 2.24
mmol), and triethylamine (0.22 g, 2.24 mmol) in DMF (5 mL)
were then added at 2-4°C. The mixture was left at ambient
temperature for 20 h (TLC monitoring), and finally heated at
60°C for 5 h, to complete reaction. The mixture was diluted with
water (100 mL), the precipitate was collected by filtration and
crystallised (acetic acid), to give the product (0.14 g, 73%), as
cream crystals, mp 244-246°C; ir(nujol): 3257 (NH), 1696, 1650
(C=O), 1593 (C=C), 783, 750 (ArCH bend) cm-1; 1H nmr
(DMSO-d6/CDCl3): δ, 0.85-0.91 (3H, t, J 7.5Hz, Me), 1.30-1.39
(2H, m, CH2CH3), 1.55-1.64 (2H, m, CH2CH2CH3), 4.04-4.10
(2H, t, J 7.5Hz, NCH2), 4.29 (2H, s, CH2Cl), 7.66-7.73 (1H, t, J
8.8Hz, 6-H), 8.25-8.28 (1H, d, J 7.5Hz, 3-H), 8.33-8.54 (3H, m,
2-H, 5-H and 7-H), 9.95 (1H, s, NH). Anal. Calcd.for
C18H17ClN2O3: C, 62.7; H, 5.0: Cl, 10,3; N, 8.1. Found: C, 62.7;
H, 5.2; Cl, 10.3; N, 8.3.
4-(Maleiamido-9-ethyl-1,8-naphthalimide (7b, R = Et, R1 =
carboxyethenyl). A mixture of 4-amino-9-ethyl-1,8-naphthal-
imide (6), (0.50 g, 2.1 mmol) and maleic anhydride (0.60 g, 6.3
mmol) in chloroform (50 mL) was refluxed for 20 h and the
solvent then removed in vacuo. The residue was stirred with
water, then filtered and the solid crystallised (ethanol/DMF) to
give yellow crystals, (0.38 g, 53%), mp 222-224°C; ir (nujol):
3275 (NH), 3132 (OH), 1717 (C=O, COOH), 1697, 1653 (C=O),
1591 (C=C), 783, 757 (ArCH bend) cm-1; 1H nmr (DMSO-
d/CDCl3): δ, 0.83-0.88 (3H, t, J 6.3Hz, Me), 3.70-3.79 (2H, q, J
7.5Hz, CH2Me, 5.92-5.97 (1H, d, J 12.5Hz, CHCOOH), 6.26-
6.31(1H, d, J 12.5Hz, NHCOCH), 7.31-7.37 (1H, t, J 7.0Hz, 6-H),
7.94-7.97 (1H, d, J 7.0Hz, 3-H), 8.08-8.22 (3H, td, 2-H, 5-H and
7-H), 11.0 (1H, s, NH). Anal Calcd. for C18H14N2O5: C, 63.9; H,
4.2; N, 8.3. Found: C, 63.6; H, 4.3; N, 8.3.
5-H and 7-H). Anal. Calcd. for C14H12N2O3 :C, 65.6; H, 4.7; N,
10.9. Found: C, 66.0; H, 5.0; N, 11.1.
4-Chloroacetamido-9-(2-chloroacetoxyethyl)-1,8-naphthal-
imide (9). An ice-cold solution of 4-amino-9-(2-hydroxyethyl)-
1,8-naphthalimide (8) (0.34 g, 1.3 mmol) in DMF (5 mL)
containing triethylamine (0.20 g, 2.0 mmol), was stirred and
treated dropwise with chloroacetyl chloride (0.22 g, 2.0 mmol) in
DMF (2 mL). Since reaction (TLC monitoring) was slow (after 4
h) more chloroacetyl chloride (0.22 g, 2.0 mmol) and
triethylamine (0.20 g, 2.0 mmol) were added dropwise to the
mixture, which was reacted at ambient temperature for 1 h. TLC
then indicated complete reaction and the mixture was diluted with
water (150 cm3) and the precipitate filtered and crystallised
(ethanol) to afford brown-yellow crystals (0.32 g, 60%), mp 211-
214°C; ir (nujol): 3274 (NH), 1753 (C=O, COOR), 1697, 1659,
1
1593 (C=C), 784, 755 (ArCH bend) cm-1; H nmr (DMSO-d6): δ
4.28 (2H, s, OCOCH2Cl), 4.29-4.45 (4H, m, CH2CH2), 4.55 (2H,
s, NHCOCH2Cl), 7.86-7.92 (1H, t, J 7.9Hz, 6-H), 8.21-8.25 (1H,
d, J 8.2Hz, 3-H), 8.46-8.65 (3H, m, 2-H, 5-H and 7-H), 10.27 (1H,
s, NH). Anal. Calcd. for C18H14Cl2N2O5 : C, 52.8; H, 3.5; Cl, 17.3.
N, 6.8. Found: C, 52.6; H, 3.6; Cl,17.2; N, 6.8.
4-n-Butylamino-9-(2-hydroxyethyl)-1,8-naphthalimide (11).
4-Nitro-9-(2-hydroxyethyl)-1,8-naphthalimide (10) was
prepared as described previously [28]. To 4-nitro-9-(2-hydroxy-
ethyl)-1,8-naphthalimide (0.50 g, 1.5 mmol) in dry DMF (25
mL), n-butylamine (0.50 g, 6.0 mmol) was added and the
mixture heated at 105-110°C for 1.5 h under nitrogen (TLC
monitoring). After work-up by dilution with water and filtration,
yellow-green crystals (0.20 g, 43%) were obtained and
crystallised (ethanol), mp 190-192°C; ir(nujol): 3471 (OH),
3392 (NH), 1672, 1641 (C=O), 1588 (C=C), 767, 757 (ArCH
1
bend) cm-1; H nmr (DMSO-d6/CDCl3): δ, 0.56-0.62 (3H, t, J
7.5Hz, Me), 1.01-1.16 (2H, m, CH2 CH3), 1.30-1.45 (2H, q, J
7.5Hz, CH2CH2CH3), 2.97-3.00 (2H, q, J 7.1Hz, NHCH2), 3.37-
3.40 (2H, q, J 7.8Hz, CH2OH), 3.81-3.87 (1H, t, J 6.8Hz, OH),
3.88-3.93 (2H, t, J 6.3Hz, NCH2), 6.24-6.27 (1H, d, J 7.9Hz, 3-
H), 6.60-6.69 (1H, br., NH, exch.), 7.13-7.20 (1H, t, J 8.8Hz, 6-
H), 7.93-7.96 (1H, d, J 7.5Hz, 2-H) 8.07-8.16 (2H, dd, 5-H and
7-H). Anal. Calcd.for C18H20N2O3: C, 69.2; H, 6.5; N, 9.0.
Found: C, 69.1; H, 6.4; N, 9.1.
4-(Maleimido-9-ethyl-1,8-naphthylimide. A mixture of the
preceding maleiamido compound (0.30 g, 0.9 mmol) and sodium
acetate trihydrate (0.50 g, 3.6 mmol) was refluxed in acetic
anhydride for 1 h, and then cooled to give the imide by
dehydration. The reaction mixture was diluted with water,
stirred for 7 h at 2-4°C and then filtered. The washed solid was
crystallised from acetic acid to give brown crystals of the
naphthalimide, (0.10 g, 35%), mp 219-221°C; ir (nujol): 1720
(C=O), 1699, 1659 (C=O), 1589 (C=C), 784, 757 (ArCH bend)
4-n-Butylamino-9-(2-chloroacetoxyethyl)-1,8-naphthal-
imide (12). To 4-n-butylamino-9-(2-hydroxyethyl)-1,8-
naphthalimide (0.6 g, 1.9 mmol), in DMF (10 mL), containing
triethylamine (0.3 g, 2.9 mmol), chloroacetyl chloride (0.32 g,
2.9 mmol) in DMF (5 mL) was added dropwise to the ice-cold
solution. TLC indicated after 4 h that reaction was still
incomplete, and chloroacetyl chloride (0.54 g, 4.75 mmol) in
DMF (5 mL) containing triethylamine (0.48 g, 4.75 mmol) was
added to the reaction mixture, which was stirred for a further 6 h
at ambient temperature. TLC indicated complete reaction and
the mixture was concentrated, and diluted with water to afford a
yellow emulsion, which solidified after stirring for 2 h at 2-4°C.
The solid was collected by filtration and crystallised
(ethanol/acetone) to give dark yellow crystals (0.20g, 27%), mp
113-116°C; ir (nujol): 3442, 3432 (NH), 1750 (COOR), 1685,
1
cm-1; H nmr (CDCl3): δ, 1.32-1.38 (3H, t, J 7.5Hz, Me), 4.23-
4.32 (2H, q, J 7.5Hz, CH2CH3), 7.06 (2H, s, COCH=CHCO),
7.62-7.66 (1H, d, J 10.0Hz, 3-H), 7.76-7.82 (1H, t, J 7.5Hz, 6-
H), 7.90-7.94 (1H, d, J 10.0Hz, 2-H), 8.66-8.71(2H, m, 5-H and
7-H). Anal. Calcd. for C18H12N2O4: C, 67.8; H, 3.8; N, 8.8.
Found: C, 68.0; H, 3.7; N, 8.7.
4-Amino-9-(2-hydroxyethyl)-1,8-naphthalimide (8). 4-Amino-
naphthalic-1,8-anhydride (2.0 mmol) and 2-hydroxyethylamine
(6.0 mmol) in DMF (25 mL) were stirred at 90°C and heated
under nitrogen until TLC indicated complete reaction (2 h). The
reaction mixture was cooled, diluted with water and the
precipitated solid was filtered and crystallised (ethanol) to afford
dark yellow prisms (50% yield), of 8, mp 261-263°C; ir (nujol):
3525 (OH), 3363, 3224 (NH), 1658, 1631 (C=O), 1576 (C=C),
778, 759 (ArCH bend).cm-1; 1H nmr (DMSO-d6/CDCl3 ): δ,
3.47-3.56 (2H, q, J 5.9Hz, CH2OH ), 3.74-3.80 (1H, t, J 5.9Hz,
OH), 4.00-4.05 (2H, t, J 5.9Hz, NCH2), 6.19 (2H,br., NH2,
exch.), 6.52-6.56 (1H, d, J 8.5Hz, 3-H), 7.24-7.30 (1H, t, J
7.8Hz, 6-H), 7.97-8.00 (1H, d, J 8.5Hz, 2-H), 8.11-8.23 (2H, dd,
1
1642 (C=O) ,1546 (C=C), 773, 755 (ArCH bend) cm-1; H nmr
(CDCl3): δ, 1.01-1.07 (3H, t, J 7.5Hz, Me), 1.48-1.63 (2H, m,
CH2CH3), 1.76-1.88 (2H, q, J 7.2Hz, CH2CH2CH3), 3.39-3.46
(2H, q, J 5.8Hz, NHCH2), 4.07 (2H, s, CH2Cl), 4.49-4.69 (4H,
m, NCH2CH2), 5.32 (1H, br., NH, exch.), 6.71-6.74 (1H, d, J
7.5Hz, 3-H), 7.58-7.66 (1H, t, J 8.8Hz, 6-H), 8.08-8.11 (1H, d, J
7.9Hz, 2-H), 8.44-8.59 (2H, dd, 5-H and 7-H).. Anal. Calcd. for

Mar-Apr 2008
The Synthesis and Fluorescence of Novel N-Substituted-1,8-naphthylimides
403
C20H21ClN2O4: C, 61.8; H, 5.5; Cl, 9.1:, N, 7.2. Found: C, 62.1;
H, 5.8; Cl, 9.0; N, 6.8.
reaction of 4-aminonaphthalic-1,8-anhydride with β-alanine in
DMF.
4-Amino-9-(carboxymethyl)-1,8-naphthalimide (14; n=1).
(a) 4-Nitronaphthalic anhydride (1.94 g, 8.0 mmol) and
glycine (0.75 g, 10.0 mmol) in ethanol (40 mL) were stirred and
refluxed until TLC indicated complete reaction. The cooled
mixture was diluted with water and the precipitated solid filtered
and crystallised (ethanol), to give pale yellow needles of the
nitro compound (13, n = 1) (yield 35%), mp 266-267°C; ir
(nujol)::3080 (CH), 1715 (C=O, COOH), 1675, 1630 (C=O),
1587 (C=C), 1535, 1360 (NO2), 788, 759 (ArCH bend) cm-1; 1H
nmr (DMSO-d6/CDCl3): δ, 4.69 (2H, s, CH2), 7.77-7.84 (1H, t, J
8.0Hz, 6-H), 8.20-8.24 (1H, d, J 8.0Hz, 3-H), 8.23-8.65 (3H, m,
2-H, 5-H and 7-H). Anal. Calcd.for C14H8N2O6: C, 56.0; H, 2.7:
N, 9.3. Found: C, 56.4; H, 3.0; N, 9.6. The nitro compound (1.2
g, 4.0 mmol) and stannous chloride (3.80 g, 20.0 mmol) in
methanol (20 mL) containing conc. hydrochloric acid (5 mL)
were refluxed for 1.5 h, concentrated in vacuo, then cooled and
diluted with water. The precipitated solid was filtered and
crystallised (ethanol) to give yellow microcrystals (yield 44%),
mp 263-266°C; ir (nujol): 3483, 3430, 3354, 3260 (NH), 1745
(C=O, COOH), 1670, 1646, (C=O), 1581 (C=C), 785, 763,
(ArCH bend) cm ; H nmr (DMSO-d6): δ, 4.64 (2H, s, CH2),
6.81-6.85 (1H, d, J 8.4Hz, 3-H), 7.59-7.66 (1H, t, J 8.0Hz, 6-H),
8.12-8.15 (1H, d, J 8.4Hz, 2-H), 8.37-8.58 (2H, dd, 5-H and 7-
H). Anal. Calcd. for C14H10N2O4:C, 61,7; H, 3.7; N, 10.4..
Found: C, 61.7; H, 4.0; N, 10.1.
(b) 4-Aminonaphthalic-1,8-anhydride (2) (2.0 mmol) and
glycine (6.0 mmol) in DMF (25 mL) were heated at 120°C for 8
h under nitrogen when TLC indicated complete reaction. The
cooled mixture was diluted with water and the precipitated solid
filtered and crystallised (ethanol) to give yellow microcrystals,
(yield 47%), mp 263-266°C.
4-Amino-9-(3-carboxypropyl)-1,8-naphthalimide (14; n =
3). 4-Nitronaphthalic anhydride (8.0 mmol) and 4-
aminobutanoic acid (10.0 mmol) were refluxed in ethanol (40
mL) for 4 h. Work up as for the previous compound afforded
creamy white needles of the nitro compound (13, n = 3), from
ethanol (yield 67%), mp 182-184°C; ir (nujol): 3084(CH), 1705
(C=O, COOH), 1658, 1628 (C=O), 1587 (C=C), 1540, 1346
1
(NO2), 785, 770 (ArCH bend) cm-1; H (DMSO-d6): δ 1.59-1.71
(2H, q, J 7.2Hz, NCH2CH2CH2), 1.96-2.03 (2H, t, J 7.4Hz,
NCH2), 3.81-3.87 (2H, t, J 7.0Hz, NCH2CH2CH2), 7.59-7.66
(1H, t, J 8.0Hz, 6-H), 8.03-8.06 (1H, d, J 8.0Hz, 3-H), 8.27-
8.42, (3H, m, 3-H, 5-H and 7-H). Anal. Calcd. for C16H12N2O6:
C, 58.5; H, 3.7; N, 8.5. Found: C, 58.5; H, 3.7: N, 8.5. The nitro
compound was reduced by the general method with stannous
chloride and gave the same compound as that formed in 11%
yield from the reaction of 4-aminonaphthalic-1,8-anhydride with
4-aminobutanoic acid, namely, 4-amino-9-(3-carboxypropyl)-
1,8-naphthalimide, orange needles mp 163-165°C; ir (nujol):
3457, 3356, 3258 (NH), 1721 (C=O, COOH), 1678, 1652
(C=O), 1574 (C=C), 772, 755 (ArCH bend) cm-1; 1H nmr
(DMSO-d6): δ 1.90-2.02 (2H, q, J 7.5Hz, NCH2CH2CH2), 2.30-
2,36 (2H, t, J 7.5Hz, NCH2), 4.07-4.13 (2H, t, J 7.5Hz,
CH2COOH), 5.82 (2H, br., NH2, exch.), 6.74-6.78 (1H, d, J
8.1Hz, 3-H), 7.47-7.53 (1H, t, J 8.5Hz, 6-H), 8.20-8.46 (3H, m,
2-H, 5-H and 7-H). Anal. Calcd for C16H14N2O4: C, 64.4; H, 4.7;
N, 9.4. Found: C, 64.3; H, 4.5; N, 9.8..
-1
1
4-Butylamino-(9-ethoxycarbonylmethyl)-1,8-naphthal-
imide (16). 4-Nitro-1,8-naphthalic anhydride (8 mmol) and ethyl
glycinate (11 mmol) in ethanol were refluxed for 10 h when
TLC indicated complete reaction. The cooled mixture was
diluted with water and the precipitated solid collected by
filtration and crystallised (ethanol) to give orange-yellow
needles (yield 55%), mp 154-155°C, consisting of 4-nitro-(9-
ethoxycarbonylmethyl)-1,8-naphthalimide (15); ir (nujol): 3085
(ArCH), 1743, (C=O, COOEt), 1707, 1670 (C=O), 1590 (C=C),
1570, 1377 (NO2), 781, 752 (ArCH bend) cm-1; 1H nmr
(CDCl3): δ 1.26-1.32 (3H, t, J 7.0Hz, Me), 4.19-4.28 (2H, q, J
7.1Hz, CH2CH3), 4.91 (2H, s, NCH2), 7.79-7.87 (2H, m, 3-H
and 6-H), 8.47-8.66 (3H, m, 2-H, 5-H and 7-H). Anal. Calcd. for
C16H12N2O6: C, 58.5; H, 3.7; N, 8.5.. Found: C, 58.4; H, 3.9; N,
8.8. 4-Nitro-(9-ethoxycarbonylmethyl)-1,8-naphthalimide (15)
(0.33 g, 1.0 mmol) and n-butylamine (0.22 g, 3.0 mmol) were
heated at 80°C in DMF (15 mL) under nitrogen for 2 h and then
at 100°C when TLC indicated complete reaction. The cooled
mixture was diluted with water and the precipitated solid
collected by filtration and crystallised (ethanol) to afford dark
yellow crystals (0.12 g, 35% yield), mp 170-171°C; ir (nujol):
3407 (NH), 1733 (C=O, COOR), 1686, 1646 (C=O), 1593
The products from methods (a) and (b) were identical.
Acetylation of the amino compound gave the acetyl derivative
which was identical with compound (4).
4-Amino-9-(2-carboxyethyl)-1,8-naphthalimide (14; n =
2). 4-Nitro-1,8-naphthalic anhydride (8.0 mmol) and 3-amino-
propionic acid (10.0 mmol) were refluxed in ethanol (40 mL) for
3 h when TLC showed reaction was completed. The cooled
mixture was diluted with water and the precipitated solid was
collected by filtration and crystallised (ethanol) to afford white
microcrystals (yield 65%), mp 198-200°C of the nitro
compound, (13, n = 2); ir (nujol): 3080 (CH), 1705 (COOH),
1675, 1628 (C=O), 1587 (C=C), 1535, 1352 (NO2), 788, 732
1
(ArCH bend) cm-1; H nmr (DMSO-d6): δ, 2.37-2.44 (2H, t, J
7.6Hz, NCH2), 4.10-4.16 (2H, t, J 7.6Hz, NCH2CH2), 7.67-7.74
(1H, t, J 8.0Hz, 6-H), 8.10-8.14 (1H, d, J 8.0Hz, 3-H), 8.35-8.56
(3H, m, 2-H, 5-H and 7-H). Anal. Calcd. for C15H10N2O6: C,
57.3; H, 3.2; N, 8.9. Found: C, 57.4; H, 3.1; N, 9.0. The nitro
compound (1.26 g, 4.0 mmol) was reduced by the general
method with stannous chloride and the precipitated solid was
collected by filtration and crystallised (ethanol) to give pale
yellow needles, mp 226-228°C; ir (nujol): 3471, 3362, 3258
(NH), 1724 (C=O, COOH), 1675, 1642 (C=O), 1581 (C=C),
1
(C=C), 781, 760 (ArCH bend) cm-1; H nmr (CDCl3): δ 0.98-
1.05 (3H, t, J 7.3Hz, CH2CH2 Me), 1.29-1.35 (3H, t, J 7.1Hz,
OCH2CH3), 1.42-1.59 (4H, m, CH2CH2CH3), 3.33-3.39 (2H, s,
NHCH2), 4.22-4.31 (2H, q, J 7.1Hz, OCH2CH3), 4.91(2H, s,
NCH2), 6.59-6.63 (1H, d, J 8.4Hz, 3-H), 7.43-7.50 (1H, t, J
7.9Hz, 6-H), 8.04-8.08 (1H, d, J 8.2Hz, 2-H), 8.33-8.47 (2H, dd,
5-H and 7-H). Anal. Calcd.for C20H22N2O4: C, 67.8; H, 6.3; N,
7.9. Found: C, 68.0; H, 6.6; N, 7.9.
Hydrolysis and acidification gave the acidic product believed
to be (17), 4-n-butylamino-9-carboxymethyl-1,8-naphthalimide
the nmr spectrum of which showed the presence of a carboxyl
and lacked an ethyl group.
1
778, 757 (ArCH bend) cm-1; H nmr (DMSO-d6): δ 2.34-2.40
(2H, t, J 7.5Hz, NCH2), 4.04-4.10 (2H, t, J 7.5Hz, NCH2CH2),
6.28 (2H, br., NH2, exch.), 6.50-6.53 (1H, d. J 7.1Hz, 3-H),
7.20-7.27 (1H, t, J 8.8Hz, 6-H), 7.92-7.95 (1H, d, J 7.5Hz, 2-H),
8.10-8.17 (2H, m, 5-H and 7-H). Anal. Calcd. for C15H12N2O4:
C, 63.4; H, 4.3: N, 9.9. Found: C, 63.7; H, 4.7: N, 9.4.
The product was identical to that obtained in 51% yield from

404
D. Yuan , R. G Brown, J. D. Hepworth, M. S. Alexiou and J. H. P. Tyman
Vol 45
Guo Liu; Pan-Feng Gao; Guo-He Huang; You-An Mao, Sensors
Actuators B 2006,114, 308.
Acknowledgements. We thank the University of Central
Lancashire for a research studentship (DY), the EPSRC for
granting us access to the Daresbury Laboratory and Swansea MS
facility, and Brent Chemicals for some financial assistance.
[21] Jiangli Fan; Xiaojun Peng; Yunkou Wu; Erhu Lu; Jun Hou;
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