1,4-Naphthoquinone disulfides and methyl sulfides: Self-assembled monolayers on gold substrates

Full text of DOI:10.1021/jo981185j

J . Org. Chem. 1999, 64, 2919-2923
2919
Sch em e 1. Na p h th oqu in on e Meth yl Su lfid es a n d
Disu lfid es P r ep a r ed in Th is Wor k
1,4-Na p h th oqu in on e Disu lfid es a n d Meth yl
Su lfid es: Self-Assem bled Mon ola yer s on
Gold Su bstr a tes
Charles A. Panetta,* Peter Wei-J en Fan, Rasem Fattah,
J oe C. Greever, Zhuoli He, Charles L. Hussey,
Dezhi Sha, and Lyle D. Wescott, J r.
The Department of Chemistry, The University of Mississippi,
University, Mississippi, 38677
Received J une 18, 1998
The preparation and electrochemistry of self-assembled
monolayers (SAMs) of organic disulfides on gold were
first described in the publications of Nuzzo1 and Tanigu-
chi2 about 15 years ago. Since then, many reports have
appeared concerning the modification of gold surfaces
with dialkyl disulfides3 and other organosulfur com-
pounds, including dialkyl sulfides.4,5
Sch em e 2. P r ep a r a tion of Na p h th oqu in on e
Meth yl Su lfid es 1a a n d 2a
Our laboratory has been active in the synthesis of a
variety of redox-active disulfides for a number of years.
These have incorporated electron-acceptor moieties, such
as 1,4-naphthoquinones and TCNQs, (tetracyanoquino-
dimethanes) electron-donating moieties, such as pyrenes
and ferrocenes, or both donors and acceptors in the same
molecule. More recently, methyl sulfides of 1,4-naphtho-
quinones were also prepared here, and we then became
aware that although many examples of disulfide and
dialkyl sulfide SAMs have been reported in the literature,
the direct comparison of the two sulfur classes with
identical terminal groups was not studied until recently.6
It is generally recognized that the structure and
interfacial properties of disulfide-modified surfaces were
effectively indistinguishable from those of surfaces modi-
fied with thiols with the same terminal alkyl groups.
However, the nature of the dialkyl sulfide-to-gold adsorp-
tion process is not at all conclusive. Some studies
conclude that the S-C bonds of dialkyl sulfides cleave
before formation of a gold thiolate,7,8 whereas others
report evidence that there is no S-C bond cleavage
during the adsorption process.6,9 The results of the
present work indicate that disulfides and methyl sulfides
with identical redox moieties (1,4-naphthoquinones) pro-
duce SAMs on gold that have quite different electro-
chemical properties. However, one cause of these differ-
ences may be due to the differences in the way the
monolayers pack.
sulfur derivatives for SAMs on gold if they showed any
clear advantages in their stability or electrochemistry.
Four pairs of 2-alkylamino- and 2-alkoxyarylamino-1,4-
naphthoquinone disulfides and methyl sulfides (1-4,
Scheme 1) were prepared by various synthetic routes. All
eight were new compounds and were completely purified
and characterized. These were the methyl sulfides and
disulfides of 2-decylamino-1,4-naphthoquinone (1), 3-chlo-
ro-2-decylamino-1,4-naphthoquinone (2), 2-(4-decoxyphe-
nyl)amino-1,4-naphthoquinone (3), and 3-chloro-2-(4-
decoxyphenyl)amino-1,4-naphthoquinone (4).
Two routes were used to prepare the methyl sulfides.
10-(Methylthio)decanamine10,11 (5) was the required in-
termediate in the syntheses of products 1a and 2a .
Treatment of the hydrochloride of 5 with 1,4-naphtho-
quinone (6) afforded a 37% yield of 1a , while product 2a
resulted from a monosubstitution reaction of 5 with 2,3-
dichloro-1,4-naphthoquinone (7, 33%, Scheme 2).
The decoxyphenylaminonaphthoquinone methyl sul-
fides, 3a and 4a , were both prepared by a route that
started with p-nitrophenol (Scheme 3). Products 2a and
4a were completely characterized except that the reso-
nances of the amine hydrogens were not observed in the
NMR spectra.
In general, the methyl sulfides of electron acceptors
were easier to synthesize compared with the preparations
of disulfides. The former would be the preferred organo-
(1) Nuzzo, R. G.; Allara, D. L. J . Am. Chem. Soc. 1983, 105, 4481.
(2) Taniguchi, I.; Toyosawa, K.; Yamaguchi, H.; Yasukouchi, K. J .
Electroanal. Chem. 1982, 140, 187.
(3) Nuzzo, R. G.; Fusco, F. A.; Allara, D. A. J . Am. Chem. Soc. 1987,
109, 2358.
(4) Troughton, E. B.; Bain, C. D.; Whitesides, G. M.; Nuzzo, R. G.;
Allara, D. L.; Porter, M. D. Langmuir 1988, 4, 365.
(5) Zhang, M.; Anderson, M. R. Langmuir 1994, 10, 2807.
(6) J ung, C.; Dannenberger, O.; Xu, Y.; Buck, M.; Grunze, M.
Langmuir 1998, 14, 1103-1107.
(7) Zhong, C.-J .; Porter, M. D. J . Am. Chem. Soc. 1994, 116, 11616.
(8) Sandroff, C. J .; Herschbach, D. R. J . Phys. Chem. 1982, 86, 3277.
(9) Beulen, M. W. J .; Huisman, B.-H.; van der Heijden, P. A.; van
Veggel, F. C. J . M.; Simons, M. G.; Biemond, E. M. E. F.; deLange, P.
J .; Reinhoudt, D. N. Langmuir 1996, 12, 6170-6172.
The disulfides of the 2-decylamino-1,4-naphthoquino-
nes, 1b and 2b, were both prepared from di(10-amino-
decyl) disulfide dihydrochloride (13) (Scheme 4).12
The disulfides of the 2-(4-decoxyphenyl)amino-1,4-
naphthoquinones, 3b and 4b, were synthesized using 10-
(10) Kjaer, A.; Gmelin, R.; J ensen, R. B. Acta Chem. Scand. 1956,
10, 1614.
(11) Walker, J . J . Chem. Soc. 1950, 193.
(12) Dirscherl, v. W.; Weingarten, F. W. Liebigs Ann. Chem. 1951,
574, 131.
10.1021/jo981185j CCC: $18.00 © 1999 American Chemical Society
Published on Web 03/26/1999

2920 J . Org. Chem., Vol. 64, No. 8, 1999
Notes
Sch em e 5. P r ep a r a tion of Na p h th oqu in on e
Sch em e 3. P r ep a r a tion of Na p h th oqu in on e
Meth yl Su lfid es 3a a n d 4a
Disu lfid es 3b a n d 4b
Sch em e 4. P r ep a r a tion of Na p h th oqu in on e
Disu lfid es 1b a n d 2b
mV easier to oxidize than the corresponding methyl
sulfides, 1a and 2a . Both disulfides and methyl sulfides
with aliphatic spacers and chlorine substitution (2a and
2b) had lower electron-transfer rates and substantial
repulsive interactions between adjacent redox centers
compared with the deschloro products, 1a and 1b. Note
that the voltammograms of SAMs modified with naph-
thoquinones 3 and 4 each showed both oxidation and
reduction reactions. The former was thought to be the
result of the donor properties of the phenylamino moi-
ety.14 Indeed, a similar wave was observed in the CV of
4-[(10-methylthio)decoxy]aniline. These results are sum-
marized in Table 1. All data in this table were collected
after repetitive scanning. When cycling, coverage dropped
fast at the very beginning and gradually slowed and
tended to be stable. SAMs of the methyl sulfides stabi-
lized after 15-20 cycles, and the decreasing rate of
surface coverage was less than 10%. SAMs of the disul-
fides stabilized after 5-10 cycles, and the decreasing rate
of surface coverage was less than 5%. The cyclic volta-
mmograms of gold substrates modified with products 1a
and 1b (Figure 1) and 2a and 2b (Figure 2) have been
included in this paper.
(4-nitrophenoxy)decyl bromide13 (8) as the starting ma-
terial and the previously unknown 15 as an intermediate
(Scheme 5).
The electrochemistry of gold electrodes modified with
each of the eight methyl sulfides and disulfides was
compared according to four parameters: the surface
coverage (Γ, in mol/cm2); the formal potential (E°′, in
volts) estimated from the average of the reduction and
oxidation peak potentials; the peak separation (∆Ep, in
Exp er im en ta l Section
Electr och em istr y. Acetonitrile (Fisher Optima grade) was
distilled from CaH2 under nitrogen, passed through activated
alumina, and stored in a tightly capped bottle over 4 Å molecular
sieves until needed. Absolute ethanol was used as received from
McCormick Distilling Co., Inc. Tetra-n-butylammonium hexaflu-
orophosphate (TBAHFP) was synthesized and purified according
to standard procedures. Standard glass microscope slides (Fisher
Cat. No.12-549) served as gold substrates; they were cleaned
by ultra sonication in successive baths of piranha solution (1:3
by volume 30% H2O2/concentrated H2SO4), distilled water, and
2-propanol (Fisher Optima grade). The oven-dried microscope
slides were coated with 50 Å of chromium followed by 1500 Å of
gold by thermal evaporation at a base pressure of 7 × 10-7 Torr
by using an Edwards Auto 306 vacuum coater equipped with a
Sycon model STM-100/MF thin film monitor. After coating was
complete, the vacuum chamber was back-filled with high-purity
nitrogen gas. The gold films prepared by this method were found
by X-ray diffraction analysis to exhibit strong Au {111} crystal-
millivolts); and the peak-width at half-maximum (∆Efwhm
,
in millivolts). The peak separation is inversely related
to the electron-transfer rate, and the peak-width at half-
maximum is a measure of the lateral interactions be-
tween molecules in SAMs (at 298 K, ∆Efwhm should be
90.3/n mV, where n is the number of electrons involved
in the redox reaction). The best coverages were observed
mainly for the disulfide derivatives, especially those with
the aliphatic side chains (1b and 2b) (Table 1). The same
disulfides had lower oxidation potentials and were 23-9
(13) Mutai, K.; Tukada, H.; Nakagaki, R. J . Org. Chem. 1991, 56,
4896.
(14) Zalis, S.; Fiedler, J .; Pospisil, L.; Fanelli, N.; Lanza, C.;
Lampugnani, L. Microchem. J . 1996, 54, 478-486.

Notes
J . Org. Chem., Vol. 64, No. 8, 1999 2921
Ta ble 1. Electr och em ica l Resu lts for Gold Electr od es Mod ified w ith Ea ch of th e Eigh t Meth yl Su lfid es a n d Disu lfid esa
SAM modified with
naphthoquinone
Γ × 1010 (mol/cm2)b
E°′ (V)c
∆Ep (mV)
∆Efwhm (mV)
1a
1b
2a
2b
0.88 ( 0.07
2.9 ( 0.3
1.3 ( 0.1
2.2 ( 0.2
0.195 ( 0.00
0.27 ( 0.03
0.10 ( 0.01
0.47 ( 0.3
1.9 ( 0.1
1.0 ( 0.1
0.17 ( 0.03
0.23
0.089 ( 0.004
0.066 ( 0.001
0.094 ( 0.007
0.085 ( 0.006
0.687 ( 0.001
-0.055 ( 0.003
0.647 ( 0.005
-0.004 ( 0.003
-0.022 ( 0.007
0.479 ( 0.006
0.071 ( 0.008
0.490
27 ( 3
67 ( 4
290 ( 30
275 ( 7
50 ( 4
26 ( 2
168 ( 9
103 ( 5
65 ( 4
200 ( 14
43 ( 8
248
98 ( 4
164 ( 5
210 ( 16
196 ( 10
75 ( 4
3a (donor portion)
3a (acceptor portion)
3b (donor portion)d
3b (acceptor portion)d
3b (acceptor portion)
4a (donor portion)
77 ( 2
128 ( 6
249 ( 12
138 ( 6
210 ( 13
71 ( 5
4a (acceptor portion)
4b (donor portion)
136
4b (acceptor portion)
4-H2NC6H4O(CH2)10SCH3
0.15
1.35 (0.03
0.058
0.463 (0.004
72
54 (5
82
130 (7
a
All measurements were collected at the same scan rate (100 mV/s) after 24 h unless otherwise noted. The +/- indicates the 95%
confidence limit. Both acceptor and donor reactions involve two electrons and two protons. c Versus SCE. Measured after 10 min.
b
d
mM solutions of the methyl sulfides and disulfides in methylene
chloride or tetrahydrofuran for 24 h. Cyclic voltammetric
measurements were made in a three-electrode cell with an
EG&G Princeton Applied Research Corp. (PARC) model 283
potentiostat/galvanostat employing PARC model 270 electro-
chemistry analysis software running on an IBM-compatible 386
computer. For studies with self-assembled monolayers, the gold-
coated substrates served as the working electrodes. They were
clamped to an O-ring joint attached to the side of the cell. The
O-ring provided a liquid-tight seal and defined the area of the
working electrode, which was ca. 1.54 cm2. The reference
electrode for all experiments was an EG&G saturated calomel
electrode (SCE) separated from the working electrode compart-
ment by means of a Luggin capillary. All potentials mentioned
in this paper were measured with respect to this reference
electrode. The counter electrode was a platinum wire spiral. The
electrolyte solutions used for aqueous experiments were 1.0 M
aqueous HClO4 and a pH ) 7.2 phosphate buffer solution
(Aldrich Chemical Co.). The solutions in the electrochemical cells
were deaerated with high-purity N2 before each experiment, and
F igu r e 1. Cyclic voltammograms of the SAMs of 2-N-(10-
methylthio)decylamino-1,4-naphthoquinone, 1a (s), and
Di[N-(1,4-naphthoquinon-2-yl)-10-aminodecyl] disulfide,1b
(- - -).
an atmosphere of N2 was maintained over the solution in the
cell during measurements. Electronic resistance compensation
was employed during all experiments. The equilibrium surface
coverage, Γ, reported for each monolayer was estimated from
the charge under the appropriate voltammetric oxidation or
reduction wave after subtraction of the residual current.
Syn th etic Ch em istr y. The following general techniques
were followed unless otherwise stated. All reactions sensitive
to air and moisture were carried out in flame-dried apparatus,
under a dry nitrogen atmosphere using either magnetic or
mechanical stirring. All melting points were determined on a
Thomas-Hoover Unimelt apparatus and are uncorrected. Infra-
red spectra were recorded on a FT-IR spectrometer using KBr
1
pellets or thin liquid films. H (300 MHz) and 13C NMR spectra
were determined on a spectrometer using CDCl3, DMSO-d6, or
D2O with tetramethylsilane (Me4Si) as the internal standard.
Column chromatography was carried out by gravity or low
pressure using 230-400 mesh E. Merck silica gel (9385). Thin-
layer chromatography was performed on Analtech Silica Gel
HLF Uniplates (10 × 20 cm, #47521) with a fluorescence
indicator. TLC spots were visualized either by exposure to iodine
vapors or by irradiation with UV light. Elemental analyses were
performed by Galbraith Laboratories, Inc., Knoxville, TN, or
Atlantic Microlab, Inc., Norcross, GA.
2-N-(10-Meth ylth io)decylam in o-1,4-n aph th oqu in on e (1a).
A mixture of 0.35 g (1.5 mmol) of 10-(methylthio)decylammo-
nium chloride (5‚HCl)10,11 and 96 mg (0.77 mmol) of Na2CO3‚
H2O in 95% ethanol was refluxed for 15 min and cooled to room
temperature. 1,4-Naphthoquinone (0.23 g, 1.46 mmol) was added
with stirring, and the mixture was refluxed for 5 h. After the
solvent was removed, the crude orange solid was placed on a
silica gel column and eluted with hexane/acetone (9:1). The
product was recrystallized from ethanol to give 0.19 g (37%) of
1a as an orange solid: mp 94.5-96.0 °C; 1H NMR (CDCl3) δ
8.10 (d, 1H), 8.04 (d, 1H), 7.72 (m, 1H), 7.61 (m, 1H), 5.89 (bs,
1H, exchangeable), 5.73 (s, 1H), 3.18 (q, 2H), 2.50 (t, 2H), 2.10
F igu r e 2. Cyclic voltammograms of the SAMs of 3-chloro-2-
N-(10-methylthio)decylamino-1,4-naphthoquinone, 2a (s), and
di[N-(3-chloro-1,4-naphthoquinon-2-yl)-10-aminodecyl] disul-
fide, 2b (- - -).
lographic texture.15 The gold electrodes were taken directly from
the vacuum coater and immersed in solutions containing 1-4.
Films were prepared by immersion of the substrates in 0.5-1.0
(15) He, Z.; Bhattacharyya, S.; Cleland, W. E. J .; Hussey, C. L. J .
Electroanal. Chem. 1995, 397, 305.

2922 J . Org. Chem., Vol. 64, No. 8, 1999
Notes
(s, 3H), 1.67 (m, 4H), 1.50-1.29 (m, 12H); IR (KBr) 3342, 2917,
2848, 1676, 1600, 1567, 1512, 1507, 1460, 1114, 720 cm-1. Anal.
Calcd for C21H29NO2S: C, 70.16; H, 8.13; N, 3.90; S, 8.92.
Found: C, 70.10; H, 8.10; N, 3.83; S, 8.84.
Di(10-p h th a lim id od ecyl) Disu lfid e (12). Benzyltriethy-
lammonium tetrathiomolybdate16 (7.3 g, 12 mmol) was slurried
in 40 mL of dry CHCI3. N-(10-Bromodecyl)phthalimide12 (11)
(4.0 g, 11 mmol) was added. The resulting mixture was stirred
vigorously at room temperature overnight. The volume was
reduced by approximately one-third, and the dark concentrate
was triturated several times with ether. The combined ether
layers were dried with anhydrous MgSO4. Evaporation of the
solvent yielded a colored oil which crystallized from hexane to
afford 2.5 g (72%) of 12 as a white solid: mp 58-60 °C (lit.12 mp
3-Ch lor o-2-N-(10-m et h ylt h io)d ecyla m in o-1,4-n a p h t h o-
qu in on e (2a ). 10-(Methylthio)decanamine (5)10,11 (0.25 g, 1.23
mmol), 0.28 g (1.23 mmol) of 2,3-dichloro-1,4-naphthoquinone,
and 0.34 g (2.46 mmol) of K2CO3 were mixed in 10 mL of 95%
ethanol, and the resultant mixture was refluxed for 10 h. After
the solvent was removed, the crude red solid was adsorbed on
0.5 g of Celite, and this was placed on a column containing 10 g
of silica gel and eluted with hexane/EtOAc (1:1). The product
was recrystallized from hexane to afford 0.16 g (33%) of a red
solid: mp 118-120 °C (dec); 1H NMR (CDCl3) δ 8.17 (d, 1H),
8.02 (d, 1H), 7.72 (dd, 1H), 7.61 (dd, 1H), 3.83 (q, 2H), 2.49 (t,
2H), 2.10 (s, 3H), 1.74-1.51 (m, 4H), 1.48-1.13 (br, 12H); IR
(KBr) 3284, 2921, 2850, 1675, 1599, 1569, 1509, 1331, 1295, 1129
cm-1. Anal. Calcd for C21H28ClNO2S: C, 64.02; H, 7.16; N, 3.56;
S, 8.14. Found: C, 63.93; H, 7.02; N, 3.54; S, 8.04.
1
49 °C); H NMR (CDCI3) δ 7.85 (m, 4H), 7.75 (m, 4H), 3.65 (t,
4H) 2.65 (t, 4H), 1.70 (m, 8H), 1.35-1.25 (m, 24H); IR (KBr)
2923, 2841, 1769, 1712, 1461, 1394, 1359, 1184, 1051, 717 cm-1
.
Di(10-a m in od ecyl) Disu lfid e Dih yd r och lor id e (13). Com-
pound 12 (2.7 g, 4.2 mmol) was added to 30 mL of ethanol in a
50 mL round-bottom flask. The mixture was warmed, and 64%
aqueous hydrazine hydrate (0.43 g, 8.4 mmol) was added
dropwise with stirring. Warming was continued until a homo-
geneous solution was obtained, which was stirred overnight. A
gelatinous suspension was formed. Approximately 1 mL of
concentrated HCI was added to adjust the pH to 1. A copious
white precipitate was formed, and the mixture was refluxed for
0.5 h. After cooling to room temperature, the phthalimide
hydrazide was removed by filtration. The filtrate was then
evaporated to give a white solid that was dissolved in a mixture
of 20 mL of ethanol and 20 mL of water. The mixture was made
basic with 10% NaOH and extracted with ether (30 mL × 4).
The ether layer was dried with anhydrous MgSO4, and the
volume was reduced in half. Dry HCI gas was bubbled through
the ether solution, and a white precipitate separated, which was
collected and washed with ether. After drying, 1.03 g (55%) of
13 was collected (Dirscherl and Weingarten prepared this
product in 49% yield, and it melted at 180 °C)12: 1H NMR (D2O)
δ 2.50 (t, 4H), 2.35 (t, 4H), 1.23 (m, 8H), 1.1-0.85 (m, 24H); IR
10-(4-Nitr op h en oxy)d ecyl Meth yl Su lfid e (9). 10-(4-Ni-
trophenoxy)decyl bromide13 (8) (11.1 g, 31 mmol), 2.6 g (34 mmol)
of thiourea, and 100 mL of DMSO were stirred and warmed until
a solution was obtained, and stirring was continued for 16 h. A
10% solution of NaOH (300 mL) was added, and the mixture
was stirred in an ice bath for 30 min. Methyl iodide (8.8 g, 62
mmol) was slowly added, and the resultant mixture was stirred
for 6 h. A sticky yellow solid was collected and washed with
water. It was crystallized from 2-propanol to afford 5.2 g (52%)
of 9: mp 58.0-59.5 °C; 1H NMR (CDCl3) δ 8.20 (d, 2H), 6.94 (d,
2H), 4.05 (t, 2H), 2.50 (t, 2H), 2.10 (s, 3H), 1.82 (m, 2H), 1.62
(m, 2H), 1.49-1.30 (m, 12H); IR (KBr) 2979, 2848, 1595, 1516,
1337, 1258, 1173, 1108, 843 cm-1
.
10-(4-Am in op h en oxy)d ecyl Meth yl Su lfid e (10). Com-
pound 9 (4.6 g, 0.014 mol) and 12.6 g (56 mmol) of SnCl2‚2H2O
were added to 50 mL of dry EtOAc, and the mixture was refluxed
for 16 h. EtOAc (50 mL) was added, and the result was washed
with several small portions of a 5% solution of EDTA‚disodium
salt dihydrate in order to remove ionic tin. The EtOAc solvent
was removed to give a yellow residue. It was recrystallized from
hexane to afford 1.5 g (36%) of 10: mp 68-70 °C; 1H NMR
(CDCl3) δ 6.75 (d, 2H), 6.65 (d, 2H), 3.87 (t, 2H), 2.50 (t, 2H),
2.10 (s, 3H), 1.73 (m, 2H), 1.57 (m, 2H), 1.50-1.25 (m, 12H); IR
(KBr) 2909-2857 (broad),1604, 1513, 1461,1130, 1001, 721 cm-1
.
Di[N-(1,4-n a p h th oqu in on -2-yl)-10-a m in od ecyl] Disu lfid e
(1b). A mixture of 200 mg (0.44 mmol) of 13, 124 mg (0.96 mmol)
of Na2CO3‚H2O, and 3.0 mL of 95% ethanol was heated to the
reflux temperature and then allowed to cool to room tempera-
ture. A solution of 142 mg (0.90 mmol) of 1,4-naphthoquinone
(6) in 3.0 mL of ethanol was added, and the stirred mixture was
refluxed for 1 h and then allowed to stir at ambient temperature
for 4 days. The brick-red mixture was diluted with about 10 mL
of CH2Cl2 and filtered to separate 198 mg of mostly inorganic
solids. The filtrate was concentrated under reduced pressure to
afford 236 mg of a dark, tarry residue, which was chromato-
graphed on silica gel using CH2Cl2/EtOAc (94:6). A middle
faction containing 1b (36 mg, 12%) was isolated. It was
(KBr) 3317, 2918, 2851, 1517, 1250, 1108, 843 cm-1
.
2-{N-4-[(10-Meth ylth io)d ecoxy]p h en yla m in o}-1,4-n a p h -
th oqu in on e (3a ). A mixture of 3.5 g (12 mmol) of 10, 1.9 g (12
mmol) of 1,4-naphthoquinone (6), and 50 mL of 95% ethanol was
refluxed for 22 h. After cooling, a purple precipitate formed and
was collected by filtration, and the residue was washed with
water and ethanol. The crude product was chromatographed on
silica gel and eluted with hexane/EtOAc (8.9:1.1). It was
recrystallized from CH2Cl2/EtOH (3:7) to give 2.0 g (36%) of 3a
as a purple solid: mp 111-112 °C; 1H NMR (CDCl3) δ 8.10 (m,
2H), 7.75-7.65 (m, 2H), 7.43 (s, 1H, exchangeable), 7.19 (d, 2H),
6.94 (d, 2H), 6.23 (s, 1H), 3.97 (t, 2H), 2.50 (t, 2H), 2.10 (s, 3H),
1.78 (m,2H), 1.57 (m, 2H), 1.50-1.33 (m, 12H); IR (KBr) 3279,
2915, 2847, 1671, 1595, 1565, 1512, 1345, 1238, 931 cm-1. Anal.
Calcd for C27H33NO3S: C, 71.81; H, 7.37; N, 3.10; S, 7.10.
Found: C, 71.70; H, 7.42; N, 3.07; S, 7.01.
2-Ch lor o-3-{N-4-[(10-m eth ylth io)d ecoxy]p h en yla m in o}-
1,4-n a p h th oqu in on e (4a ). A mixture of 2.8 g (9.6 mmol) of 10,
2.2 g (9.6 mmol) of 2,3-dichloro-1,4-naphthoquinone (7), 1.38 g
(10 mmol) of K2CO3, and 50 mL of 95% ethanol was refluxed for
16 h. The solution changed from yellow to dark red, and a dark
brown precipitate separated. The latter was collected and
washed with 5 mL portions of acetone and hot water until it
was neutral. The mother liquor was extracted two times with
50 mL portions of CHCI3. After removal of the organic solvent,
0.71 g (15%) of a purple solid was isolated. Recrystallization once
from hexane/ethyl acetate (8:2) and twice from hexane gave 0.17
g (3%) of a pure product: mp 118-120 °C (dec); 1H NMR (CDCl3)
δ 8.20 (d, lH), 8.17 (d, lH), 7.77 (m, lH), 7.75 (m, lH), 7.05 (d,
2H), 6.87 (d, 2H), 3.96 (t, 2H), 2.49 (t, 2H), 2.10 (s, 3H), 1.76 (m,
2H), 1.57 (m, 2H), 1.37-1.25 (br, 12H); IR (KBr) 3243, 2923,
2844, 1677, 1633, 1606, 1562, 1495, 1464, 1287, 1234, 1140, 826
cm-1. Anal. Calcd for C27H32ClNO3S: C, 66.72; H, 6.64; N, 2.88;
S, 6.60. Found: C, 66.54; H, 6.84; N, 2.74; S, 6.74.
1
recrystallized from EtOAc: mp 99-101 °C; H NMR (CDCl3) δ
8.10 (d, 2H), 8.08 (d, 2H), 7.75 (dd, 2H), 7.62 (dd, 2H), 5.91 (bs,
2H), 5.72 (s, 2H), 3.17 (m, 4H), 2.67 (t, 4H), 1.37-1.68 (m, 32H);
IR (KBr) 3344, 2993, 2850, 1675, 1600, 1570, 1520 cm-1. Anal.
Calcd for (C40H52N2O4S2)2‚H2O: C, 68.83; H, 7.65; N, 4.01.
Found: C, 69.09; H, 7.50; N, 3.95.
Di[N -(3-ch lor o-1,4-n a p h t h oq u in on -2-yl)-10-a m in od e -
cyl] Disu lfid e (2b). A mixture of 13 (0.48 g, 11 mmol), Na2-
CO3‚H2O (0.28 g, 23 mmol), and 95% ethanol (45 mL) was
refluxed for 15 min and cooled to room temperature. 2,3-
Dichloro-1,4-naphthoquinone (7, 0.49 g, 22 mmol) was added,
and the mixture was refluxed and stirred for 14 h. The
precipitate was collected by filtration and washed with water
and cold ethanol. Purification by column chromatography (hex-
ane/EtOAc, 80:20) on silica gel gave 4 as a red powder weighing
0.47 g (56%). Recrystallization from CHCl3/ethanol (6:4) gave
an analytical sample: mp 91.5-92.5 °C; 1H NMR (CDCI3) δ 8.14
(d, 2H),8.02 (d, 2H), 7.72 (m, 2H), 7.62 (m, 2H), 6.15 (bs, 2H,
exchangeable), 3.85 (q, 4H), 2.67 (t, 4H), 1.70-1.60 (m, 8H) 1.55-
1.20 (m, 24H); IR (KBr) 3273, 2922, 2844, 1676, 1598, 1572,
1507, 1442, 1332, 1293, 1130, 715 cm-1. Anal. Calcd for C40H50
-
Cl2N2O4S2: C, 63.39; H, 6.65; N, 3.70; S, 8.46. Found: C, 63.30;
H, 6.86; N, 3.66; S, 8.35.
10-(4-Am in op h en oxy)d ecyl Br om id e (14). 10-(4-Nitrophe-
noxy)decyl bromide13 (8) (8.8 g, 25 mmol) was added to a
(16) Ramesha, A. R.; Chandrasekaran, S. Synth. Commun. 1992,
22, 3277.

Notes
J . Org. Chem., Vol. 64, No. 8, 1999 2923
hydrogenation bottle containing 200 mL of 95% ethanol. The
bottle was warmed gently until the solid dissolved, and 0.3 g of
PtO2 was added. The mixture was placed in a Parr hydrogena-
tion apparatus and was treated with 50 psi of hydrogen at room
temperature until no more hydrogen was taken up (about 2 h).
The reaction mixture was filtered through Celite, and the filtrate
was concentrated under reduced pressure. The residue was
recrystallized from ethanol to yield 7.0 g (94.3%) of 14: mp 66-
68 °C (EtOH); 1H NMR (CDCl3) δ 6.74 (d, 2H), 6.66 (d, 2H), 3.88
(t, 2H), 3.40 (t, 2H), 2.92 (broad s, 2H, exchangeable) 1.77-1.89
(m, 4H), 1.23-1.41 (m, 12H); IR (KBr) 3331 (broad), 2917, 2850,
were repeated. The solvents were removed, and the residue was
chromatographed (CHCl3/EtOAc, 95:5) on a silica gel column.
Fractions which contained the red product were combined and
evaporated, and the residue was recrystallized from CHCl3/EtOH
to afford 29 mg of 3b (14%), a red solid that melted at 127-128
°C: 1H NMR (CDCl3) δ 8.10 (d, 4H), 7.80 (dd, 2H), 7.60 (dd, 2H),
7.45 (s, 2H), 7.20 (d, 4H), 6.95 (d, 4H), 6.25 (s, 2H), 3.95 (t, 4H),
2.70 (t, 4H), 1.75 (m, 8H), 1.40 (m, 24H); IR (KBr) 3252, 2900,
2840, 1677, 1590, 1563, 1510, 1237, 822, 722, cm-1. Anal. Calcd
for C52H60N2O6S2: C, 71.55; H, 6.88; N, 3.21. Found: C, 71.18;
H, 6.91; N, 3.22.
1517, 1465, 1246, 1039, 828, 649 cm-1
.
Di{10-[N-(3-ch lor o-1,4-n a p h th oqu in on -2-yl)-4-a m in op h e-
n oxy]d ecyl} Disu lfid e (4b). A mixture of 10-(4-aminophenoxy)-
decyl disulfide (15, 141 mg, 0.25 mmol) and 2,3-dichloro-1,4-
naphthoquinone (7, 114 mg, 0.50 mmol) was added to 20 mL of
95% ethanol in a round-bottom flask. Then, NaCO3‚H2O (62 mg,
0.50 mmol) was added, and the mixture was heated at 65 °C for
6 h. The reaction mixture was cooled to room temperature; the
red solid that was formed was filtered and washed with cold
water and then ethanol. This solid was air-dried and chromato-
graphed on silica gel with CH2Cl2 and then with CH2Cl2/EtOAc,
1:4. The first purple faction was collected, the solvent was
removed, and the residue was recrystallized from DMSO to
10-(4-Am in op h en oxy)d ecyl Disu lfid e (15). A solution of
1.0 g (2.8 mmol) of 10-(4-aminophenoxy)decyl bromide (14) in
10 mL of dry CHCl3 was prepared. This was added during a
period of 10 min to a stirred solution of 2.0 g (3.3 mmol) of
benzyltriethylammonium tetrathiomolybdate16 in 15 mL of dry
CHCl3. One hour later, the mixture turned black, and it was
stirred for an additional 20 h at room temperature. The solvent
was removed under reduced pressure, and the resultant sticky
residue was extracted first with ether (3 × 30 mL) and then
with THF (3 × 20 mL). Evaporation of the extracts left a pale
orange residue that was recrystallized from ether/CHCl3 to give
1.78 g (71%) of 15: mp 87-88 °C; 1H NMR (CDCl3) δ 6.72 (d,
4H), 6.65 (d, 4H), 3.87 (t, 4H), 3.44 (bs, 4H), 2.68 (t, 4H), 1.67
(m, 8H), 1.30 (m, 24H); IR (KBr) 3380, 3311, 2919, 2850, 1512,
1246, 830, 765, cm-1. Anal. Calcd for C32H52N2O2S2‚H2O: C,
66.39; H, 9.40; N, 4.84; S, 11.08. Found: C, 66.79; H, 9.44; N,
4.76; S, 11.54.
1
afford 160 mg (60%) of 4b: mp 123-124 °C; H NMR (DMSO-
d6) δ 9.24 (s, 2H, exchangeable), 8.02 (d, 4H), 7.83 (m, 4H), 7.06
(d, 4H), 6.85 (d, 4H), 3.94 (t, 4H), 2.68 (t, 4H), 1.70 (t, 4H), 1.61
(t, 4H), 1.27-1.20 (m, 24H); IR (KBr) 3330, 2919, 2851, 1684,
1671, 1576, 1512, 1397, 1240, 1138, 826, 716 cm-1. Anal. Calcd
for
C52H58Cl2N2O6S2: C, 66.30; H, 6.20; Cl, 7.53; N, 2.97.
Di{10-[N-(1,4-n a p h th oqu in on -2-yl)-4-a m in op h en oxy]d e-
cyl} Disu lfid e (3b). A mixture of 136 mg (0.24 mmol) of 15,
100 mg (0.63 mmol) of 1,4-naphthoquinone (6), and 15 mL of
95% ethanol was stirred and heated at the reflux temperature
for 6 h and then at room temperature for 16 h. Anhydrous THF
(5 mL) was added to increase the solubilities of the reactants,
and the 6 h of reflux and 16 h of stirring at room temperature
Found: C, 66.05; H, 6.25; Cl, 7.75; N, 2.93.
Ack n ow led gm en t. The work was supported by the
National Science Foundation-Mississippi EPSCoR Project
(Grants OSR 91-08767 and EPS 94-52857).
J O981185J