Double thioalkylation/arylation of nitroarenes with the reduction of nitro- to amino group

Article abstract of DOI:10.1016/S0040-4020(02)01454-0

Some active bicyclic nitroarenes readily react with an excess of alkyl/arylthiols in the presence of DBU and bis-trimethylsilylacetamide (BSA) in DMF solution, to give dithioalkyl/aryl substituted anilines in moderate to good yields via displacement of ortho- and para-hydrogen atoms with simultaneous reduction of the nitro- to amino-group.

Full text of DOI:10.1016/S0040-4020(02)01454-0

Tetrahedron 59 (2003) 101–110
Double thioalkylation/arylation of nitroarenes with the reduction
of nitro- to amino group
´
Zbigniew Wrobel
Institute of Organic Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, PL-01-224 Warsaw, Poland
Received 12 August 2002; revised 14 October 2002; accepted 7 November 2002
Abstract—Some active bicyclic nitroarenes readily react with an excess of alkyl/arylthiols in the presence of DBU and bis-
trimethylsilylacetamide (BSA) in DMF solution, to give dithioalkyl/aryl substituted anilines in moderate to good yields via displacement of
ortho- and para-hydrogen atoms with simultaneous reduction of the nitro- to amino-group. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
hydrogen atoms with a sulfur nucleophile was accompanied
by the reduction of a nitro-group to an amine.
Sulfur-based anions are known as good nucleophiles in the
aromatic nucleophilic substitution in nitroarenes containing
the leaving group in the ortho-, para-1–3 and even (in the
case of polynitroarenes) meta-position.4,5 However, there
are a very few reports about the direct nucleophilic
substitution of hydrogen by thioanions, and even in these
cases due to low yields, the reaction was often not of
synthetic value.1,6 Recently it was reported that nitroquino-
lines react with alkanethiolate anions to give products of
oxidative nucleophilic substitution of hydrogen by thiolates
in moderate but preparative yields.6 Nitroarenes as well as
oxygen in the air were found to be involved in the oxidation
process.
Thus, treatment of nitronaphthalene 1a (X¼Y¼Z¼CH;
1 mmol) with an excess of 1,1-dimethylethylthiol 2a (R¼
t-Bu; 5 mmol), DBU (7.5 mmol) and BSA (2.5 mmol) in
DMF (5 mL) solut0ion gave, after 10 days of stirring at room
temperature, 20,4 -di-(1,1-dimethylethylthio)-1-naphthyl-
amine 3aa in 87% yield (Scheme 1).
Investigation of the reaction in different conditions (Table
1) revealed that it proceeded without BSA, although the
yield was much less. Other Lewis acids did not improve the
yield of product 3aa. Protic solvents, which can sometimes
be complementary to base/Lewis acid/aprotic solvent
system,10 were less effective in this case.
The reaction was found to be general character for different
alkyl or aryl thiols, and active bicyclic nitroarenes provided
they possess two hydrogen atoms (to be replaced by two
thiolate substituents) accessible for nucleophilic displace-
ment (Table 2).
2. Results and discussion
Continuing our investigations into reactions of aromatic
nitro compounds with different nucleophilic agents in
the presence of Lewis acids,7–12 we observed a new kind
of transformation of nitroarenes under action of thiols
leading to dithioalkylated amines. Substitution of two
Reactions proceeded smoothly with hindered tertiary and
Scheme 1.
Keywords: bicyclic aromatic compounds; thiols; substitution; reduction; amines.
E-mail: wrobel@icho.edu.pl
0040–4020/03/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01454-0

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Z. Wrobel / Tetrahedron 59 (2003) 101–110
102
Table 1. Reaction of nitronaphthalene 1a with t-butylthiol 2a in various conditions
Entry
Base
Lewis acid (LA)
LA (equiv.)
Solvent
Temperature (8C)
Timea
Yieldb (%)
1
2
3
4
5
6
7
8
9
DBU
DBU
DBU
DBU
DBU
Et3N
Et3N
DBU
NaOH
BSA
–
–
t-BuMe2SiCl
MgCl2
Me3SiCl
Ti(O-i-Pr)4
MgCl2
–
2.5
–
–
2.5
0.625
5.0
2.5
0.625
–
DMF
DMF
DMF
DMF
DMF
DMF
MeCN
DMSO
MeOH
Room temperature
Room temperature
70
Room temperature
Room temperature
60
Room temperature
Room temperature
Room temperature
10
20
4
30
60
4
6
14
10
87
23
43
38
41
49
–
45
59
a
Days.
Isolated.
b
Table 2. Reactions of bicyclic nitroarenes 1 with thiols 2 in DBU/BSA/DMF system
Entry
Reactants
X
Y
W
R
Timea
Products
Yieldb (%)
3
4
Yieldb (%)
1
2
3
4
5
6
7
8
1aþ2a
1aþ2b
1aþ2c
1aþ2d
1aþ2e
1aþ2f
1aþ2g
1aþ2h
1bþ2a
1bþ2b
1bþ2c
1bþ2e
1bþ2f
1cþ2a
1dþ2a
1dþ2c
CH
CH
CH
CH
CH
CH
CH
CH
N
N
N
N
N
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
t-Bu
i-Bu
n-Bu
Et
Allyl
4-ClC6H4
4-MeC6H4
PhCH2
t-Bu
i-Bu
n-Bu
Allyl
10
10
6
14
14
20
14
30
4
4
6
3
12
2
3aa
3ab
3ac
3ad
3ae
3af
3ag
3ah
3ba
3bb
3bc
3be
3bf
3ca
3da
3dc
87
65
52
22
22
59
80
25
96
77
32
28
64
54
50
24
–
–
4ab
4ac
4ad
4ae
–
–
4ah
–
4bb
4bc
4be
–
–
–
4dc
Tr
19
37
60
–
–
27c
–
Tr
33
47
–
–
c
c
9
10
11
12
13
14
15
16
c
4-ClC6H4
t-Bu
t-Bu
CH
CH
CH
CH
CH
6
30
–
16
N
n-Bu
a
Days.
Isolated.
Corresponding disulphide 5 isolated as a byproduct.
b
c
secondary alkylthiols or arylthiols. Interestingly, with less
hindered primary alkylthiols it led to a mixture of di- (3) and
mono- (4) thioalkylated products. The latter ones were
comparatively unstable and darkened very quickly so in
some cases correct elemental analysis was impossible to
obtain. Reaction of 2a with 6-nitroquinoline which has only
one hydrogen atom (in position 5-) susceptible to aromatic
nucleophilic substitution led to a mixture of amine 4ea and
hydroxylamine 6 (Scheme 2).
unambiguously elucidated by independent synthesis of
4ac and its ortho-analog 4ac0 (Scheme 3).
For other aminothiols 4, the position of the thioalkyl
substituent was assumed to be para- as in the case of 4ac.
The mechanism of the reaction was not clear. Kawakami
and Suzuki showed that direct oxidative thioalkylation and
dithioalkylation of various nitroquinolines with alkyl thiols
in NaH/THF/2108C system were very fast processes.6
Thus, one could expect a similar pathway in our DBU/BSA/
DMF/room temperature system with the modification that,
The position of the thioalkyl substituent in 4ac was
Scheme 2.

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Z. Wrobel / Tetrahedron 59 (2003) 101–110
103
Scheme 3. (a) TsCI/DIPEA/DCM; (b) n-BuSH/K2CO3/DMF; (c) SnCI2/AcOEt-EtOH.
Scheme 4.
in the presence of an excess of the thiolate anion, reduction
of the nitro-group to the amine could occur, thus terminating
the reaction. This possibility was ruled by in experiment in
which 1-butylthio-4-nitronaphthalenes 9a and 9b were
allowed to react with thiol 2c in standard reaction conditions
(Scheme 4).
via crystallisation from the reaction mixture in about 50%
yield when the r0eaction was arrested after 30 min, and
turned out to be 2 ,40-di-(1,1-dimethyletylthio)-1-hydroxyl-
aminonaphthalene 11. This in turn could be converted to
3aa under standard reaction conditions (Scheme 5).
These results can be rationalized on the basis of the reaction
pathway shown in Scheme 6.
Neither 3ac nor 4ac were detected among the reaction
products for 9b as a substrate whereas for 9a only small
amount of 3ac was isolated. The main products in both cases
were bissulphides 10a and 10b resulting from the
substitution of the nitro group with the n-butylthiolate
anion. Such type of nitro-thiolate replacement although not
completely clear has already been found.6
The thiolate anion 12 and nitroarene 1 form the Meisen-
heimer complex 13 directly, or via an electron transfer-
recombination of a radical/anion two step sequence.6
Adduct 13 is converted to the nitroso compound 15
probably via sililated derivative 14.7–12 Nitroso compound
15 can be reduced to 4 in a multistage way, including
formation of N-hydroxysulfenamide and thiolytic cleavage
of the N–S bond13 (path a). In some cases, disulphides 5
were isolated from reaction mixtures. Alternatively nitroso
compound 15 can be converted to a strongly electrophilic
sulfenamide cation13 which may rearrange to 3, but more
probably under action of silylating agent 15 is converted to
quinoid-type oxime derivative 16. This in turn undergoes
Following of the progress of the reaction of 1a with 2a
carefully, revealed comparatively fast disappearance of the
substrate 1a, but rather slow formation of the terminal
product 3aa. Tlc analysis showed formation of an
intermediate slightly more polar than 1a in hexane–ethyl
acetate (8:1) solvent system. This intermediate underwent
destruction during column chromatography. It was isolated
Scheme 5.

´
Z. Wrobel / Tetrahedron 59 (2003) 101–110
104
Scheme 6.
Scheme 7.
the second addition of 12 to form adduct 17 which, after
silylation isomerises to hydroxylamine derivative 18
(isolated after quenching with water as deprotected 11).
40-(1,1-dimethylethylthio)naphthalene was formed in 85%
yield (Scheme 7).
It appears to be analogous to the known reaction of 19 with
sodium hydrogen sulphite, leading to sodium 1-amino-2-
hydroxy-4-sulphonate14–16 via substitution of hydrogen
and reduction steps and most probably via an ortho-benzo-
quinone oxime intermediate.17
Instead of addition to the aromatic ring to form 16 and
ultimately 3, the nitroso derivative 15 can be reduced to
amine 4. It seems that addition prevailed in the case of
tertiary thiolates, whereas less hindered primary ones cause
the reduction as well.
Reduction steps terminating the sequence and leading to
amine 3 are rather vague. They may consist of silylation and
electron transfer processes with thiolate anion 12 as an
electron donor.1
It should be mentioned that the initial addition of anion 12 to
the nitro compound 1 could occur both on ortho- and para-
position. For clarity, only para-pathway was shown, leading
to isomers para- of 13, 14, 15 and 16. It seems obvious that
4 could be formed only from para- substituted nitroso
compound 15. On the other hand bis-substituted 3 could be
formed by successive addition of two thiolates to ortho-
then to para-position or vice versa.
In order to improve the yield of 3aa and economize on the
reaction time, some other ‘external’ reducing agents were
tried to convert the crude reaction mixture after formation of
18 (or 11) to final product 3aa (Scheme 8).
Hypothesis of the presence of nitroso compound as an
intermediate was supported by the reaction of stable
commercial 1-nitroso-2-naphthol 19 with thiol0 2a under
standard reaction conditions, in which 10-amino-2 -hydroxy-
In both cases, reaction can be completed very quickly but
the yields were substantially lower when compared with the
standard procedure.
3. Experimental
1
Melting points were uncorrected. H and 13C NMR spectra
were recorded on Varian Gemini 400 MHz in CDCl3
solution unless otherwise stated in reference to TMS.
Chemical shifts were expressed in ppm, coupling constants
Scheme 8. Reduction conditions: (a) Na2S2O4 (10 eq.)/aq. NaHCO3/608C/
3h 56%; (b) Zn (10 eq.)/AcOH/reflux/300 54%.

´
Z. Wrobel / Tetrahedron 59 (2003) 101–110
105
in hertz. Mass spectra were obtained on ADM-604. IR
spectra were done on Spectrum 2000. Column chroma-
tography was performed on silica gel 240–400 mesh with
hexane-ethyl acetate mixtures as eluants. Nitronaphthalene,
5-, 8-nitroquinolines, 5-nitroisoquinoline and all thiols were
commercially available.
7.59 (d, J¼7.8 Hz, 1H), 7.82 (ddd, J¼8.2, 1.3, 0.7 Hz, 1H),
8.61 (ddd, J¼8.4, 1.3, 0.7 Hz, 1H); dC¼143.1, 136.0, 135.8,
127.2, 126.5, 125.0, 124.2, 121.1, 120.6, 109.3, 46.3, 29.6,
20.4, 11.4; nmax (KBr): 3468.1, 3379.7, 3233.7, 2963.5,
2923.5, 2873.0, 1621.9, 1584.2, 1511.5, 1456.4, 1386.4,
1358.2, 1338.2, 1279.8, 824.1, 758.3; m/z (%): 232 (9.3),
231 (59.9), 177 (4.5), 176 (13.1), 175 (100.0), 174 (50.1),
143 (22.1), 130 (21.2); HRMS calcd for C14H17NS:
[231.1082]; found: 231.1080.
3.1. Reactions of nitroarenes 1 with thiols 2 in the
presence of Lewis acid: standard procedure
Nitroarene 1 (2.5 mmol), thiol 2 (12.5 mmol), and Lewis
acid (for BSA: 1.6 mL; 6.25 mmol) were placed in 50 mL
flask and dissolved in dry DMF (20 mL). The flask was
immersed in a cold water bath and DBU (2.8 mL;
18.75 mmol) was added. After stoppering the flask the
mixture was stirred at room temperature for the time
indicated in Tables 1 and 2. The progress of the reaction was
followed by tlc. After completion of the reaction the mixture
was treated with satd aq. NaHCO3 solution (20 mL), and
argon was bubbled through the mixture (outlet connected to
the bubbler with aq. chloramine T solution) to remove most
odour and volatile substances. The residue was diluted with
satd NaHCO3 solution (100 mL) and extracted with ethyl
acetate (3£50 mL), extracts were dried (MgSO4), concen-
trated and the residue chromatographed using hexane–ethyl
acetate mixtures as eluants. Products isolated are referred in
Table 2 and Scheme 2.
3.1.3. Reaction of nitronaphthalene1a with n-butylthiol
2c (entry 3). Amino-20,40-di-(1-butylthio)-naphthalene;
3ac: 415 mg (52%). Dark yellow oil. dH¼0.87 (t, J¼
7.3 Hz, 3H), 0.88 (t, J¼7.3 Hz, 3H), 1.36–1.46 (m, 4H),
1.50–1.58 (m, 4H), 2.76–2.81 (m, 4H), 5.1 (broad s, 2H),
7.50 (ddd, J¼8.3, 6.8, 1.3 Hz, 1H), 7.57 (ddd, J¼8.3, 6.8,
1.3 Hz, 1H), 7.78 (s, 1H), 7.83 (ddd, J¼8.3, 1.3, 0.6 Hz,
1H), 8.51 (ddd, J¼8.3, 1.3, 0.6 Hz, 1H); dC¼145.3, 139.6,
134.9, 126.9, 126.7, 125.4, 123.7, 121.8, 120.7, 111.8, 36.0,
35.2, 31.9, 31.6, 21.8, 21.7, 13.7, 13.6; nmax (film): 3467.8,
3358.7, 2957.3, 2928.4, 2871.1, 1602.1, 1415.5, 1378.5,
1363.4; m/z (%): 320 (18.1), 319 (85.5), 264 (10.8), 263
(23.4), 262 (100.0), 206 (39.0), 174 (15.9). Anal. calcd for
C18H25NS2 [319.53]: C, 67.66; H, 7.89; N, 4.38%; found:
C, 67.52; H, 7.75; N, 4.39%. Amino-40-(1-butylthio)-
naphthalene; 4ac: 110 mg (19%). Dark yellow oil. dH¼
0.86 (t, J¼7.2 Hz, 3H), 1.36–1.45 (m, 2H), 1.49–1.57 (m,
2H), 2.79 (t, J¼7.2 Hz, 2H), 4.21 (broad s, 2H), 6.72 (d,
J¼7.9 Hz, 1H), 7.49 (ddd, J¼8.3, 6.8, 1.4 Hz, 1H), 7.55
(ddd, J¼8.3, 6.8, 1.4 Hz, 1H), 7.56 (d, J¼7.9 Hz, 1H), 7.81
(ddd, J¼8.4, 1.3, 0.6 Hz, 1H), 8.55 (ddd, J¼8.4, 1.3, 0.6 Hz,
1H); dC¼142.7, 135.0, 133.7, 126.7, 126.5, 125.0, 124.3,
121.6, 121.2, 109.4, 36.1, 31.6, 21.8, 13.7; nmax (film):
3466.4, 3378.7, 2957.0, 2928.5, 2870.6, 1621.8, 1584.3,
1511.6, 1456.4, 1435.0, 1338.5, 1278.9, 823.0, 758.0; m/z
(%): 232 (9.7), 231 (59.5), 175 (27.7), 174 (100.0), 143
(13.7), 130 (19.6); HRMS: calcd for C14H17NS: [231.1082];
found: 231.1076.
3.1.1. Reaction of nitronaphthalene 10a with 1,1-dimethyl-
ethylthiol 2a (entry 1). Amino-2 ,40-di-(1,1-dimethyl-
ethylthio)naphthalene; 3aa: 694 mg (87%). Yellow
crystals; mp 98–1008C (AcOEt–hexane); dH¼1.28 (s,
9H), 1.36 (s, 9H), 5.32 (broad s, 2H), 7.52 (ddd, J¼8.4,
6.8, 1.4 Hz, 1H), 7.56 (ddd, J¼8.4, 6.8, 1.4 Hz, 1H), 7.81
(ddd, J¼8.4, 1.4, 0.6 Hz, 1H), 7.85 (s, 1H), 8.70 (ddd, J¼
8.4, 1.4, 0.6 Hz, 1H); dC¼148.6, 147.3, 137.9, 128.2, 127.0,
125.2, 123.4, 121.8, 117.8, 109.5, 48.8, 47.3, 31.2, 31.1;
n
max (KBr): 3449.7, 3340.2, 2967.3, 1597.9, 1416.5, 1360.8,
1167.4, 756.8; m/z (%): 320 (5.2), 319 (24.1), 263 (14.7),
209 (9.5), 208 (13.9), 207 (100.0), 206 (15.9), 175 (6.2), 174
(33.4). Anal. calcd for C18H25NS2 [319.53]: C, 67.66; H,
7.89; N, 4.35%; found: C, 67.81; H, 8.13; N, 4.36%.
3.1.4. Reaction of nitronaphthalene 1a with ethylthiol 2d
(entry 4). Amino-20,40-diethylthionaphthalene; 3ad:
145 mg (22%); Dark yellow oil. dH¼1.21 (t, J¼7.3 Hz,
3H), 1.23 (t, J¼7.3 Hz, 3H), 2.78–2.84 (m, 4H), 5.20 (broad
s, 1H), 7.48–7.52 (m, 1H), 7.55–7.59 (m, 1H), 7.80 (s, 1H),
7.82 (ddd, J¼8.4, 1.3, 0.6 Hz, 1H), 8.51 (ddd, J¼8.2, 1.3,
0.6 Hz, 1H); 13C: d¼145.6, 140.0 135.0, 127.0, 126.7,
125.5, 123.7, 121.8, 120.2, 111.3, 30.2, 29.5, 15.1, 14.7;
3.1.2. Reaction of nitronaphthalene 1a with 1-methyl-
propylthiol 2a (entry 2). Amino-20,40-di-(1-methylpropyl-
thio)naphthalene; 3ab: 520 mg (65%). yellow oil. dH¼
0.99–1.04 (m, 6H), 1.17–1.20 (m, 3H), 1.22–1.24 (d, J¼
6.8 Hz, 3H), 1.44–1.56 (m, 2H), 1.58–1.70 (m, 2H),
2.95–3.01 (m, 1H), 3.02–3.09 (m, 1H), 5.10 (broad s,
2H), 7.47–7.52 (m, 1H), 7.55–7.59 (m, 1H), 7.76–7.83 (m,
2H), 7.81 (s, 1H), 8.54–8.59 (m, 1H); nmax (KBr): 3469.5,
3361.3, 2964.1, 2922.9, 2873.6, 1601.7, 1496.9, 1453.1,
1416.1, 1377.7, 1362.8, 1224.8, 1147.9, 757.5; m/z (%): 321
(10.8), 320 (21.3), 319 (100.0), 318 (6.7), 317 (27.4), 288
(15.4), 263 (27.8), 262 (36.9), 260 (6.2), 232 (12.2), 231
(6.8), 208 (6.5), 207 (20.6), 206 (25.4). Anal. calcd for
C18H25NS2 [319.53]: C, 67.66; H, 7.89; N, 4.38; S, 20.01%;
found: C, 67.65; H, 7.59; N, 4.64; S, 20.0%. Traces (11 mg;
,1%) of amino-40-(1-methylpropylthio)naphthalene; 4ab:
yellow oil. dH¼0.99 (t, J¼7.4 Hz, 3H), 1.19 (d, J¼6.8 Hz,
3H), 1.43–1.53 (m, 2H), 1.58–1.68 (m, 2H), 2.98 (m, 1H),
4.25 (broad s, 2H), 6.72 (d, J¼7.8 Hz, 1H), 7.48 (ddd,
J¼8.2, 6.8, 1.3 Hz, 1H), 7.56 (ddd, J¼8.4, 6.8, 1.3 Hz, 1H),
n
max (film): 3464.7, 3356.8, 2972.0, 2924.0, 2867.4, 1602.3,
1497.1, 1415.5, 1377.5, 1363.8, 1259.8, 756.1; m/z (%): 265
(6.8), 264 (11.8), 263 (71.6), 236 (9.4), 235 (14.8), 234
(100.0), 206 (11.5), 205 (8.0), 203 (10.3), 202 (17.9), 201
(3.9), 200 (5.6), 190 (9.4), 174 (14.0), 173 (4.3). Anal. calcd
for C14H17NS2: [263.43]: C, 63.83; H, 6.50; N, 5.32; S,
24.35%; 0found: C, 63.97; H, 6.66; N, 5.34; S, 24.27%.
Amino-4 -ethylthionaphthalene; 4ad: 188 mg (37%). Dark
yellow oil; dH¼1.19 (t, J¼7.4 Hz, 3H), 2.80 (q, J¼7.4 Hz,
2H), 4.20 (broad s, 2H), 6.70 (d, J¼7.8 Hz, 1H), 7.45–7.49
(m, 1H), 7.53–7.58 (m, 1H), 7.57 (d, J¼7.8 Hz, 1H), 7.81
(ddd, J¼8.4, 1.3, 0.6 Hz, 1H), 8.54 (ddd, J¼8.6, 1.3, 0.6 Hz,
1H); dC¼142.9, 135.1, 134.0, 126.7, 126.5, 125.0, 124.2,
121.2, 121.0, 109.3, 30.2, 14.8; nmax (film): 3461.6, 3374.8,
2971.8, 2924.2, 2866.5, 1622.0, 1584.5, 1511.6, 1435.2,
1359.0, 1338.6, 1280.7, 1259.4, 823.7, 757.4; m/z (%): 203

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Z. Wrobel / Tetrahedron 59 (2003) 101–110
106
(8.5), 174 (15.0), 144 (10.7), 143 (100.0), 142 (4.9), 116
(17.4), 115 (30.4); HRMS: calcd for C12H13NS: [203.0769];
found: 203.0769.
3016.6, 2914.7, 1603.0, 1491.1, 1418.8, 1364.9, 1981.9,
1013.9, 801.6, 757.0, 676.7; m/z (%): 389 (11.8), 388 (24.7),
387 (100.0), 266 (3.8), 265 (12.6), 264 (63.5), 263 (11.1),
262 (4.2), 221 (4.2), 220 (16.7). Anal. calcd for C24H21NS2:
[387.57]: C, 74.38; H, 5.46; N, 3.61; S, 16.55%; found: C,
74.22; H, 5.27; N, 3.61; S, 16.46%; first fraction from
column chromatography contained excess of 2g together
with its dimer 4-methylphenyldisulphide 5g: m/z (%): 248
(9.2), 247 (14.9), 246 (92.7), 182 (11.1), 125 (5.5), 124
(17.4), 123 (100.0), 122 (7.6), 121 (8.2).
3.1.5. Reaction of nitronaphthalene 1a with allylthiol 2e
(entry 5). Amino-20,40-diallylthionaphthalene; 3ae: 158 mg
(22%). Dark yellow oil. dH¼3.38–3.42 (m, 4H), 4.81–4.95
(m, 4H), 5.12 (broad s, 2H), 5.78–5.90 (m, 2H), 7.48–7.52
(m, 1H), 7.56–7.60 (m, 1H), 7.74 (s, 1H), 7.80–7.83 (m,
1H), 8.50–8.52 (m, 1H); nmax (film): 3467.6, 3359.6,
3078.0, 2977.6, 2914.9, 1602.5, 1497.3, 1416.4, 1379.0,
1364.2, 1225.1, 987.4, 917.8, 756.4; m/z (%): 289 (5.4), 288
(9.8), 287 (56.8), 248 (8.9), 247 (16.5), 256 (100.0), 214
(8.9), 213 (56.2), 212 (5.2), 207 (5.0), 206 (8.5), 205 (51.4),
204 (5.1), 200 (12.7), 199 (6.8), 180 (11.3), 161 (21.4).
Anal. calcd for C16H17NS2 [287.45]: C, 66.86; H, 5.96; N,
4.87; S, 22.31%; found: C, 66.81; N, 6.12; N, 5.01; S,
22.19%. Amino-40-allylthionaphthalene; 4ae: 320 mg (60%).
Dark yellow oil. dH¼3.40 (ddd, J¼7.3, 1.4, 0.9 Hz, 2H),
4.24 (broad s, 2H), 4.83 (ddt, J¼17.0, 2.8, 1.4 Hz, 1H), 4.91
(ddt, J¼9.9, 2.8, 0.9 Hz, 1H), 5.85 (ddt, J¼17.0, 9.9, 7.3 Hz,
1H), 6.70 (d, J¼7.7 Hz, 1H), 7.47–7.51 (m, 1H), 7.54–7.59
(m, 1H), 7.55 (d, J¼7.7 Hz, 1H), 7.81 (ddd, J¼8.4, 1.3,
0.6 Hz, 1H), 8.55 (dd, J¼8.4, 1.3, 0.6 Hz, 1H); dC¼143.1,
135.2, 134.8, 134.2, 126.7, 126.6, 125.0, 124.2, 121.2, 120.4,
117.0, 109.3, 39.6; nmax (film): 3465.9, 3379.0, 3233.5,
3079.2, 2912.4, 1621.7, 1583.9, 1511.3, 1456.4, 1434.7,
1387.2, 1359.4, 1280.8, 918.7, 822.4, 757.7; m/z (%): 216
(3.3), 251 (23.0), 176 (4.2), 175 (10.6), 174 (100.0); HRMS:
calcd for C13H13NS: [215.0769]; found: 215.0761.
3.1.8. Reaction of nitrona0phthalene 1a with benzylthiol
2h (entry 8). Amino-20,4 -di-(phenylmethylthio)naphtha-
lene; 3ah: 240 mg (25%). yellow oil; dH¼3.80 (s, 2H), 3.88
(s, 2H), 4.92 (broad s, 2H), 7.05–7.11 (m, 4H), 7.15–7.22
(m, 6H), 7.45–7.50 (m, 1H), 7.46 (s, 1H), 7.52–7.57 (m,
1H), 7.75 (ddd, J¼8.2, 1.3, 0.6 Hz, 1H), 8.46 (ddd, J¼8.4,
1.3, 0.6 Hz, 1H); dC¼146.4, 141.2, 138.2, 138.2, 135.2,
129.0, 128.8, 128.4, 128.3, 127.2, 127.1, 126.9, 126.6,
125.4, 123.5, 121.9, 119.8, 110.9, 41.2, 40.4; nmax (KBr):
3416.8, 3332.2 3025.0, 2927.2, 1601.2, 1492.6, 1450.8,
1410.5, 1373.8, 1225.4, 1026.9, 772.4, 757.6, 696.9; m/z
(%): 389 (4.1), 388 (9.7), 397 (34.9), 298 (6.9), 297 (13.3),
296 (62.0), 205 (3.9), 91 (100.0). Anal. calcd for
C24H21NS2: [387.57]: C, 74.38; H, 5.46; N, 3.61; S,
16.55%; 0 found: C, 73.83; H, 5.47; N, 3.61; S, 16.33%.
Amino-4 -phenylmethylthionaphthalene; 4ah: 179 mg (27%).
Dark yellow oil. dH¼3.94 (s, 2H), 4.23 (broad s, 2H), 6.63
(d, J¼7.8 Hz, 1H), 7.07–7.10 (m, 2H), 7.14–7.22 (m, 3H),
7.37 (d, J¼7.8 Hz, 1H), 7.48 (ddd, J¼8.2, 6.7, 1.4 Hz, 1H),
7.54 (ddd, J¼8.4, 6.7, 1.4 Hz, 1H), 7.82 (ddd, J¼8.2, 1.4,
0.6 Hz, 1H), 8.53 (ddd, J¼8.4, 1.4, 0.6 Hz, 1H); dC¼143.2,
138.4, 135.1, 134.9, 128.9, 128.3, 126.8, 126.7, 126.6,
125.0, 124.2, 121.2, 120.6, 109.3, 41.3; nmax (film):3468.0,
3381.7, 3233.1, 3059.2, 3027.5, 2920.5, 1621.5, 1583.2,
1511.3, 1454.7, 1434.9, 1387.2, 1359.8, 1339.2, 1281.2,
822.5, 757.7, 699.1; m/z (%): 266 (6.5), 265 (32.6), 176
(5.6), 175 (12.3), 174 (100.0), 165 (7.0), 164 (9.1), 131
(5.0), 130 (17.2), 121 (8.2); HRMS: calcd for C17H15NS:
[265.0925]; found: 265.0934; first fractions from column
chromatography (257 mg) consisted with mixture of benzyl
mercaptan 2h and its dimer benzyl disulphide 5h: m/z (%):
247 (1.3), 246 (7.7), 214 (3.7), 181 (5.46), 92 (9.6), 91
(100.0); HRMS: calcd for C14H14S2: [246.0537]; found:
246.0547.
3.1.6. Reaction of nitronaphthalene 1a with 4-chloro-
thiophenol 2f (entry 6). Amino-20,40-di-(4”-chloro-
phenylthio)naphthalene; 3af: 631 mg (59%). Yellow
crystals; mp 135–1388C (AcOEt). dH¼5.27 (broad s, 2H),
6.94 (AA0 part of the 1st AA0XX0 system, 2H)0, 7.02 (AA0
part of 0the 02nd AA0XX0 system, 2H), 7.11 (XX part o0f the
1st AA XX system, 2H), 7.18 (XX0 part of the 2nd AA XX0
system, 2H), 7.52–7.59 (m, 2H), 7.85–7.87 (m, 1H), 7.93
(s, 1H), 8.32–8.35 (m, 1H); dC¼147.9, 143.1, 137.6, 135.8,
134.9, 131.6, 130.9, 129.2, 128.9, 128.5, 127.7, 127.6,
126.9, 126.1, 123.7, 122.0, 116.9, 107.5; nmax (KBr):
3480.1, 3366.6, 1601.3, 1494.3, 1473.7, 1420.1, 1381.5,
1364.5, 1089.9, 1008.1, 812.2, 757.7; m/z (%): 430 (18.1),
430 (18.8), 429 (75.3), 428 (26.2), 427 (100.0), 286 (33.2),
285 (21.4), 284 (90.6), 283 (12.3), 249 (21.8), 240 (27.5).
Anal. calcd for C22H15NS2Cl2 [428.29]: C, 61.75; H,
3.53; N, 3.27%; found: C, 61.54; H, 3.49; N, 3.13%.
4-Chlorophenyl disulphide; 5f (300 mg) also isolated and
identified by means of ms spectrum: m/z (%): 290 (10.0),
289 (6.3), 288 (49.4), 287 (8.9), 286 (70.0), 224 (6.2), 222
(9.6), 145 (37.9), 144 (13.2), 143 (100.0); HRMS: calcd for
C12H385Cl2S2: [285.9445]; found: 285.9457.
3.1.9. Reaction of 5-nitroquinoline 1b with 1,1-dimethyl-
ethylthiol 2a (entry 9). 50-Amino-60,80-di-(1,1-dimethyl-
ethylthio)quinoline; 3ba: 768 mg (96%). yellow crystals;
mp 149–1568C (EtOH). dH¼1.31 (s, 9H), 1.38 (s, 9H), 5.40
(broad s, 2H), 7.39 (dd, J¼8.5, 4.2 Hz, 1H), 8.09 (s, 1H),
8.20 (dd, J¼8.5, 1.7 Hz, 1H), 9.06 (dd, J¼4.2, 1.7 Hz, 1H);
dC¼151.0, 150.2, 148.7, 130.5, 120.0, 119.8, 118.5, 110.2,
49.1, 47.2, 31.2, 31.1; m/z (%): 320 (17.7), 264 (18.4), 210
(10.0), 209 (15.0), 208 (100.0), 207 (13.4), 175 (20.2), 163
(10.7); nmax (KBr): 3328.7, 2957.5, 1618.1, 1558.1, 1362.3,
1341.4, 1162.7, 782.8. Anal. calcd for C17H24N2S2
[320.52]: C, 63.70, H, 7.55; N, 8.74; S, 20.01%; found: C,
63.53; H, 7.55; N, 8.65; S, 20.33%.
3.1.7. Reaction of nitronaphthalene 1a with 4-methyl-
thiophenol 2g (entry 7). Amino-20,40-di-(400-methyl-
phenylthio)naphthalene; 3ag: 770 mg (80%). light pink
solid; mp 107–1108C (AcOEt–hexane). dH¼2.24 (s, 3H),
2.29 (s, 3H), 6.98 (s, 4H), 7.04 (s, 4H), 7.47–7.55 (m, 2H),
7.81–7.85 (m, 1H), 7.94 (s 1H), 8.38–8.40 (m, 1H);
dC¼147.2, 142.7, 135.7, 135.6, 135.3, 134.9, 132.8, 129.8,
129.6, 127.9, 127.1, 127.0, 126.9, 125.8, 123.8, 121.8,
117.9, 108.9, 20.9, 20.8; nmax (KBr): 3468.4, 3352.7,
3.1.10. Reaction of 5-nitroquinoline0 1b with 2-methyl-
propylthiol 2a (entry 10). 50-Amino-6 ,80-di-(1-methylpro-
pylthio)quinoline; 3bb: 619 mg (77%). Light green solid;

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Z. Wrobel / Tetrahedron 59 (2003) 101–110
107
mp 79–818C (aq. EtOH); (main rotamer). dH¼1.02 (t,
J¼7.3 Hz, 3H), 1.04 (t, J¼7.3 Hz, 3H), 1.25 (d, J¼6.8 Hz,
3H), 1.30 (dd, J¼6.8, 1.6 Hz, 3H), 1.50–1.80 (m, 4H),
3.01–3.11 (m, 1H), 3.39–3.57 (m, 1H), 5.04 (broad s, 2H),
7.40 (dd, J¼8.4, 4.0 Hz, 1H), 7.75 (d, J¼0.9 Hz, 1H), 8.16
(dd, J¼8.4, 1.7 Hz, 1H), 8.97 (dd, J¼4.0, 1.7 Hz, 1H); nmax
(KBr): 3409.1, 3295.0, 3172.8, 2961.8, 2921.9, 1624.5,
1592.8, 1561.6, 1486.7, 1448.0, 1373.0, 1346.1, 857.9,
773.8; m/z (%): 322 (5.0), 321 (9.5), 320 (44.6), 319 (4.8),
318 (17.3), 289 (9.5), 288 (21.0), 287 (100.0), 286 (8.9), 285
(43.4), 264 (15.0), 263 (5.1), 234 (4.3), 233 (21.9), 232
(7.7), 231 (21.6), 230 (8.2), 229 (3.4), 209 (8.8), 208 (53.7),
207 (27.6), 201 (5.4), 177 (4.8), 176 (24.3), 175 (43.0), 174
(9.1), 173 (6.4), 163 (26.4). Anal. calcd for C17H24N2S2:
[320.52]: C, 63.70; H, 7.55; N, 8.74; S, 20.01%; found: C,
63.63; H, 7.33; N, 8.62; S, 19.73%. 50-Amino-80-(1-
methylpropylthio)quinoline; 4bb: 12 mg (,1%). Dark
yellow oil. dH¼1.02 (t, J¼7.4 Hz, 3H), 1.30 (d, J¼6.6 Hz,
3H), 1.52–1.62 (m, 1H), 1.70–1.78 (m, 1H), 3.40–3.48 (m,
1H), 6.79 (d, J¼7.9 Hz, 1H), 7.39 (dd, J¼8.5, 4.2 Hz, 1H),
7.55 (d, J¼7.9 Hz, 1H), 8.17 (dd, J¼8.5, 1.6 Hz, 1H), 8.98
(dd, J¼4.2, 1.6 Hz, 1H); dC¼149.7, 147.9, 141.2, 131.9,
129.9, 124.7, 119.8, 119.5, 119.2, 42.7, 29.4, 20.0, 11.4;
202 mg (28%). Yellow oil. dH¼3.41 (dt, J¼7.3, 0.9 Hz,
2H), 3.67 (dt, J¼6.9, 0.9 Hz, 2H), 4.88–5.10 (m, 4H), 4.99
(broad s, 1H), 5.79–5.97 (m, 2H), 7.43 (dd, J¼8.5, 4.2 Hz,
1H), 7.68 (s, 1H), 8.16 (dd, J¼8.5, 1.6 Hz, 1H), 8.98 (dd,
J¼4.2, 1.6 Hz, 1H); dC¼150.0, 147.5, 144.2, 137.7, 133.9,
133.6, 130.5, 123.5, 120.2, 118.8, 117.8, 117.4, 111.9, 38.6,
36.3; nmax (film): 3438.6, 3342.4, 3212.9, 3078.7, 2977.0,
2914.6, 1607.5, 1563.4, 1484.8, 1402.4, 1353.3, 1224.3,
988.0, 918.2, 779.0; m/z (%): 290 (3.3), 289 (5.6), 288
(31.4), 257 (3.8), 256 (11.0), 255 (68.5), 247 (17.5), 216
(6.2), 215 (18.8), 214 (100.0), 213 (32.9), 206 (15.1), 182
(31.9), 181 (28.5). Anal. calcd for C15H16N2S2 [288.44]: C,
62.44; H, 5.59; N, 9.71; S, 22.23%; f0ound: C, 62.35; H,
5.61; N, 9.80; S, 22.12%. 50-Amino-8 -allylthioquinoline;
4be: 254 mg (47%). Yellow solid; mp 80–828C (AcOEt–
hexane). dH¼3.66 (dt, J¼6.8, 1.2 Hz, 2H), 4.17 (broad s,
2H), 5.00 (ddt, J¼10.1, 1.7, 1.2 Hz, 1H), 5.06 (ddt, J¼17.1,
1.7, 1.2 Hz, 1H), 5.92 (ddt, J¼17.1, 10.1, 6.8 Hz, 1H), 6.77
(d, J¼7.9 Hz, 1H), 7.39 (dd, J¼8.4, 4.0 Hz, 1H), 7.51 (d,
J¼7.9 Hz, 1H), 8.17 (dd, J¼8.4, 1.7 Hz, 1H), 8.98 (dd, J¼
4.0, 1.7 Hz, 1H); dC¼149.7, 147.4, 141.2, 134.0, 131.1,
130.0, 124.4, 119.9, 119.5, 117.3, 110.1, 36.4; nmax (film
from CHCl3): 3438.2, 3344.2, 3232.3, 1632.9, 1600.0,
1587.4, 1563.2, 1459.6, 1419.1, 1381.2, 1357.9, 1322.7,
919.1, 811.8, 778.5; m/z (%): 216 (16.9), 184 (13.9), 183
(100.0), 182 (9.4), 181 (3.5), 176 (8.9), 175 (37.9), 169
(8.1), 157 (10.1); HRMS: calcd for C12H12N2S: [216.0721];
found: 216.0723.
n
max (KBr): 3341.0, 3232.6, 2963.7, 2926.0, 2872.6, 1630.5,
1598.5, 1586.9, 1562.3, 1505.7, 1458.5, 1419.4, 1378.5,
1323.0, 1017.5, 813.7, 779.6; m/z (%): 233 (5.8), 232 (34.0),
271 (3.4), 203 (5.6), 200 (10.1), 199 (69.4), 178 (4.9), 177
(13.2), 176 (100.0), 175 (23.7), 144 (31.9); HRMS: calcd for
C13H16N2S: [232.1034]; found: 232.1042.
3.1.13. Reaction of 5-nitroquinoline 1b with 4-chloro-
thiophenol 2f (entry 13). 50-Amino-60,80-di-(400-chloro-
phenylthio)quinoline; 3bf: 686 mg (64%). Yellow solid;
mp 156–1598C (AcOEt). dH¼5.06 (broad s, 2H), 7.00 (AA0
part of the 1st AA0XX0 system, 2H), 7.17–7.35 (m, 6H),
7.47 (dd, J¼8.4, 4.2 Hz, 1H), 7.54 (s, 1H), 8.20 (dd, J¼8.4,
1.4 Hz, 1H), 9.01 (dd, J¼4.2, 1.7 Hz, 1H); nmax (KBr):
3478.8, 3359.5, 3072.3, 1604.8, 1559.1, 1474.4, 1406.8,
1350.7, 1090.2, 101.2, 812.5, 772.4; m/z (%): 432 (17.6),
431 (20.0), 430 (75.6), 429 (29.4), 428 (100.0), 287 (30.3),
286 (20.7), 285 (82.4), 284 (16.5), 254 (10.7), 252 (32.4),
250 (37.3). Anal. calcd for C21H14N2S2Cl2 [429.27]: C,
58.76; H, 3.29; N, 6.53%; found: C, 58.68; H, 3.58; N,
6.51%.
3.1.11. Reaction of05-nitroquinoline 1b with n-butylthiol
2c (entry 11). 5 -Amino-60,80-di-(1-butylthio)quinoline;
3bc: 256 mg (32%). Yellow oil. dH¼0.88 (q as a super-
position of two t, J¼7.3 Hz, 6H), 1.37–1.45 (m, 4H), 1.50–
1.60 (m, 4H), 2.81–2.87 (m, 4H), 5.07 (broad s, 2H), 7.55
(dd, J¼6.0, 1.0 Hz, 1H), 7.80 (s, 1H), 8.57 (d, J¼6.0 Hz,
1H), 9.83 (d, J¼1.0 Hz, 1H); dH¼149.7, 146.9, 142.9,
134.5, 130.4, 125.5, 120.3, 118.9, 113.3, 35.3, 32.2, 31.9,
30.8, 22.1, 21.8, 13.7, 13.6; nmax (film): 3438.4, 3339.1,
2957.1, 2928.6, 2870.9, 1608.3, 1561.9, 1484.1, 1450.8,
1401.5, 1387.1, 1353.4, 1222.1, 779.0; m/z (%): 322 (4.4),
321 (9.0), 320 (40.5), 291 (8.2), 289 (5.9), 288 (20.4), 287
(100.0), 264 (9.2), 246 (4.6), 245 (23.9), 231 (5.3), 230
(17.2), 208 (3.7), 207 (10.2), 189 (8.0), 188 (5.3). Anal.
calcd for C17H24N2S2 [320.52]: C, 63.70, H, 7.55; N, 8.74;
S, 20.01%;0 found: C, 63.6; H, 7.52; N, 8.68; S, 20.05%.
50-Amino-8 -(1-butylthio)quinoline; 4bc: 191 mg (33%).
Dark yellow crystals; mp 98–1008C (AcOEt–hexane).
dH¼0.92 (t, J¼7.4 Hz, 3H), 1.45–1.54 (m, 2H), 1.65–1.74
(m, 2H), 3.00 (t, J¼7.4 Hz, 2H), 4.11 (broad s, 2H), 6.79 (d,
J¼7.9 Hz, 1H), 7.39 (dd, J¼8.5, 4.2 Hz, 1H), 7.42 (d,
J¼7.9 Hz, 1H), 8.17 (dd, J¼8.5, 1.7 Hz, 1H), 8.96 (dd,
J¼4.2, 1.7 Hz, 1H); dC¼149.5, 146.9, 140.3, 129.9, 128.4,
126.3, 120.0, 119.6, 110.4, 32.1, 30.8, 22.2, 13.7; nmax
(KBr): 3441.7, 3335.5, 3216.8, 2950.0, 2920.2, 2852.2,
1629.8, 1602.8, 1589.5, 1460.5, 1416.4, 1382.8, 1358.0,
1319.1, 1258.1, 1017.8, 806.4, 798.9, 776.9, 645.2; m/z (%):
233 (6.3), 232 (35.6), 203 (14.5), 200 (15.0), 199 (100.0),
189 (13.4), 188 (7.9), 17.7 (4.1), 176 (26.5), 175 (18.4);
HRMS: calcd for C13H16N2S [232.1034]: found: 232.1037.
3.1.14. Reaction of 8-nitroquinoline 1c with 1,1-dimethyl-
ethylthiol 2a (entry 14). 80-Amino-50,70-di-(1,1-dimethyl-
ethylthio)quinoline; 3ca: 433 mg (54%). Yellow solid.
dH¼1.26 (s, 9H), 1.38 (s, 9H), 6.11 (broad s, 2H), 7.46
(dd, J¼8.5, 4.2 Hz, 1H), 7.83 (s, 1H), 8.75 (dd, J¼4.2,
1.7 Hz, 1H), 8.90 (dd, J¼8.5, 1.7 Hz, 1H); dC¼150.4, 148.0,
147.3, 138.2, 135.8, 132.8, 122.2, 114.3, 109.5, 48.9, 47.3,
31.3, 31.1; nmax (KBr): 3459.0, 3339.1, 2962.1, 1600.4,
1580.8, 1481.7, 1451.0, 1166.4, 789.2; m/z (%): 320 (25.9),
264 (16.6), 209 (13.3), 208 (100.0), 207 (16.8), 175 (37.3).
Anal. calcd for C17H24N2S2 [320.52]: C, 63.70, H, 7.55; N,
8.74; S, 20.01%; found: C, 63.71; H, 7.45; N, 8.69; S,
20.11%.
3.1.15. Reaction of 5-nitroisoquinoline 1d with 1,1-di-
methylethylthiol 2a (entry 15). 50-Amino-20,40-di-(1,1-
dimethylethylthio)isoquinoline; 3da: 400 mg (50%).
Yellow solid; mp 167–1718C (AcOEt–hexane). dH¼1.30
(s, 9H), 1.38 (s, 9H), 5.40 (broad s, 2H), 7.56 (dd, J¼5.9,
3.1.12. Reaction of 5-nitroquinoline 1b with allylthiol 2e
(entry 12). 50-Amino-60,80-di-(allylthio)quinoline; 3be:

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Z. Wrobel / Tetrahedron 59 (2003) 101–110
108
0.9 Hz, 1H), 8.56 (d, J¼5.9 Hz, 1H), 10.01 (d, J¼0.9 Hz,
1H); dC¼153.1, 148.4, 147.5, 142.7, 131.8, 126.2, 117.8,
114.3, 113.5, 49.4, 47.4, 31.3, 31.1; nmax (KBr): 3426.4,
3311.5, 3205.4, 3168.3, 2957.5, 1627.8, 1551.8, 1474.4,
1429.9, 1362.7, 1162.8, 823.8; m/z (%): 320 (15.8), 264
(14.9), 210 (9.0), 209 (13.4), 208 (100.0), 175 (23.7). Anal.
calcd for C17H24N2S2 [320.52]: C, 63.70, H, 7.55; N, 8.74;
S, 20.01%; found: C, 63.70; H, 7.55; N, 8.74%.
3.2. Independent synthesis of 10-amino 20/40 butylthio-
naphthalenes 2ac and 2ac0 (Scheme 3)
3.2.1. Step a. 10-Nitro020 and 40 tosyloxynaphthalenes 8a and
8b. 20 or 40 hydroxy-1 -nitronaphthalene18 (7a or 7b; 1.89 g,
10 mmol) were dissolved in dry DMF (25 mL) with
diisopropylethylamine (2.2 mL, 12.5 mmol). The reaction
flask was immersed in a cooling bath (cold water) and solid
tosyl chloride (2.4 g, 12.5 mmol) was added. The reaction
mixture was stirred overnight at room temperature. After
pouring onto water (150 mL), the mixture was extracted
with AcOEt (3£50 mL), the combined extracts washed with
water, dried (MgSO4), the solvent evaporated and the
residue chromatographed to give products 8a (2.68 g; 78%)
or 8b (2.16 g; 63%).
3.1.16. Reaction of 5-nitro0isoquinoline 1d with
n-butylthiol 2c (entry 16). 5 -Amino-20,40-di-(1-butyl-
thio)isoquinoline; 3dc: 188 mg (24%). Dark yellow oil.
dH¼0.88 (q as a result of superposition of two t, J¼7.1 Hz,
6H), 1.39–1.46 (m, 4H), 1.51–1.59 (m, 4H), 2.81–2.87 (m,
4H), 7.55 (dd, J¼6.0, 0.9 Hz, 1H), 7.80 (s, 1H), 8.56 (d,
J¼6.0 Hz, 1H), 9.82 (d, J¼0.9 Hz, 1H); dC¼151.8, 143.9,
143.2, 140.0, 129.2, 126.8, 121.6, 116.6, 114.6, 36.7, 35.1,
32.1, 31.8, 22.1, 22.0, 13.9, 13.8; nmax (film): 3432.3,
3323.4, 3297.7, 2957.6, 2928.6, 2871.4, 1621.5, 1600.0,
1554.2, 1478.7, 1464.1, 1366.5, 1223.8, 1049.1, 821.4; m/z
(%): 322 (10.7), 321 (20.9), 320 (100.0), 265 (7.7), 264
(21.2), 263 (58.2), 208 (10.4), 207 (31.4), 176 (5.7), 175
(12.0). Anal. calcd for C17H24N2S2 [320.52]: C, 63.70, H,
7.55; N, 8.74; S, 20.01%; found: C, 63.66; H, 7.47; N, 8.49;
S, 19.91%. 50-Amino-80-(1-butylthioisoquinoline; 4dc:
73 mg (13%). Dark yellow oil. dH¼0.87 (t, J¼7.4 Hz,
3H), 1.36–1.45 (m, 2H), 1.50–1.58 (m, 2H), 2.83 (t, J¼
7.4 Hz, 2H), 4.31 (broad s, 2H), 6.89 (d, J¼7.8 Hz, 1H),
7.57 (dd, J¼5.9, 0.8 Hz, 1H), 7.60 (d, J¼7.8 Hz, 1H), 8.55
(d, J¼5.9 Hz, 1H), 9.87 (d, J¼0.8 Hz, 1H); dC¼151.6,
142.3, 141.7, 134.6, 129.4, 127.1, 122.2, 114.0, 112.7, 38.5,
31.5, 21.8, 13.6; nmax (film): 3345.5, 3209.3, 2957.4,
2928.6, 2871.0, 1640.8, 1605.4, 1583.2, 1494.4, 1448.5,
1381.5, 1360.8, 1330.6, 1282.6, 1055.5, 820.8; m/z (%): 234
(5.7), 233 (15.6), 232 (100.0), 189 (3.1), 178 (13.5), 177
(13.5), 176 (93.5), 175 (86.5), 174 (5.5); HRMS: calcd for
C13H16N2S: [232.1034]; found: 232.1033.
10-Nitro-20-Tosyloxynaphthalene 8a. Yellow crystals; mp
135–1378C (AcOEt–hexane). dH¼2.47 (s, 3H), 7.34–7.37
(AA0 part of AA0BB0 system, 2H), 7.61–7.67 (m, 2H), 7.66
(d, J¼9.0 Hz, 1H), 7.70–7.72 (m, 1H), 7.79–7.81 (part BB0
of AA0BB0 system, 2H), 7.91–7.93 (m, 1H), 8.04 (d,
J¼9.0 Hz, 1H); dC¼146.4, 138.5, 132.2, 131.8, 131.6,
130.1, 129.4, 128.6, 128.2, 127.7, 125.0, 121.8, 120.9, 21.8;
n
max (KBr): 1643.6, 1596.3, 1533.3, 1508.7, 1357.6, 1225.6,
1214.5, 1192.6, 1175.6, 1090.2, 1028.3, 965.8, 869.7, 813.3,
768.7, 678.9; m/z (%): 344 (4.1), 343 (20.7), 157 (4.0), 156
(6.9), 155 (80.2), 139 (3.5), 130 (5.0), 114 (5.6), 92 (7.4), 91
(100.0). Anal. calcd for C17H13NO5S [343.36]: C, 59.47; H,
3.82; N, 4.08; S, 9.34%; found: C, 59.52; H, 3.93; N, 4.16;
S, 9.24%.
10-Nitro-40-tosyloxynaphthalene 8b. Yellow crystals; mp
138–1418C (AcOEt–hexane). dH¼2.44 (s, 2H), 7.31–7.35
(part AA0 of AA0BB0 system 2H), 7.36 (d, J¼8.4 Hz, 1H),
7.58 (ddd, J¼8.6, 6.9, 1.1 Hz, 1H), 7.720 (ddd, J¼8.8, 6.9,
1.3 Hz, 1H), 7.80–7.81 (BB0 part of AA BB0 system, 2H),
8.04 (ddd, J¼8.6, 1.3, 0.8 Hz, 1H), 8.18 (d, J¼8.4 Hz, 1H),
8.54 (dt, J¼8.8, 0.8 Hz, 1H); dC¼149.6, 146.2, 144.7,
132.1, 130.2, 130.1, 128.5, 128.1, 127.9, 126.6, 124.1,
123.2, 122.5, 116.5, 21.7; nmax (KBr): 1632.2, 1595.8,
1569.6, 1522.8, 1507.4, 1425.3, 1367.4, 1348.8, 1260.7,
1226.1, 1188.9, 1175.2, 1090.8, 1042.6, 984.1, 848.1, 815.4,
803.5, 769.2, 733.5, 708.9, 681.8; m/z (%): 344 (4.5), 343
(22.1), 157 (5.7), 156 (8.8), 155 (100.0), 114 (5.1). Anal.
calcd for C17H13NO5S [343.36]: C, 59.47; H, 3.82; N, 4.08;
S, 9.34%; found: C, 59.46; H, 4.02; N, 4.14; S, 9.26%.
3.1.17. Reaction of 6-nitroisoquinoline 1e with 1,1-di-
methylethylthiol 2a (Scheme 2): chromatography per-
formed with CHCl3–MeOH (10:1) as eluant. 60-Amino-50-
(1,1-dimethylethylthio)isoquinoline; 4ea: 197 mg. Brown
solid; mp 49–518C. dH¼1.32 (s, 9H), 4.91 (broad s, 2H),
7.23 (d, J¼9.0 Hz, 1H), 7.35 (dd, J¼8.4, 4.2 Hz, 1H), 7.93
(dd, J¼9.0, 0.7 Hz, 1H), 8.62 (dd, J¼4.2, 1.6 Hz, 1H), 8.78
(ddd, J¼8.4, 1.6, 0.7 Hz, 1H): nmax (KBr): 3434.6, 3275.9,
3140.9, 2955.1, 1618.5, 1553.5, 1494.8, 1418.8, 1359.4,
1164.2, 1149.7, 827.5, 808.7; m/z (%): 232 (7.7), 177 (11.3),
176 (100.0), 175 (7.4), 149 (6.1), 148 (6.7), 144 (5.9), 132
(4.8), 132 (6.2). Anal. calcd for C13H16N2S [232.35]: C,
67.20; H, 6.94; N, 12.06; S, 13.80%; found: C, 66.97; H,
7.04; N, 11.78; S, 13.56%. Additionally 114 mg of brown
3.2.2. Step b. Tosylate 7a or 7b (972 mg, 3.84 mmol) was
dissolved in dry DMF (20 mL), n-BuSH (470 mL,
4.4 mmol) was added, followed by addition of solid
K2CO3 (830 mg, 6 mmol). The mixture was stirred over-
night at room temperature. After pouring onto satd aq.
NaHCO3 solution (100 mL), extraction with AcOEt
(3£50 mL) and column chromatography the product 9a
(480 mg, 65%) or 9b (604 mg, 82%) was isolated.
1
solid was isolated which gave unresolvable H NMR but
was judged to be 60-hydroxylamino-50-(1,1-dimethyl-
ethylthio)isoquinoline; 6 on the basis of its ms spectrum:
mp 177–1798C; m/z (%): 248 (10.6), 232 (2.6), 193 (3.8),
192 (31.7), 191 (3.2), 177 (8.4), 176 (41.4), 175 (100.0), 174
(5.6), 173 (7.8), 148 (9.1), 147 (4.0), 131 (8.6), 129 (5.9);
HRMS: calcd for C13H16N2SO: [248.0983]; found:
248.0991; nmax (film): 3272.2, 3117.4, 2815.5 (broad),
1602.5, 1585.3, 1500.9, 1461.8, 1412.1, 1352.9, 1164.5,
1145.9, 1125.6, 987.8, 836.5, 807.9. The sample of 6 was
converted to 4ae on heating to reflux in Zn/AcOH system.
20-(1-Butylthio)-10-nitronaphthalene 9a. Yellow solid; mp
49–518C (hexane). dH¼0.91 (t, J¼7.4 Hz, 3H), 1.40–1.49
(m, 2H), 1.59–1.66 (m, 2H), 3.02 (t, J¼7.4 Hz, 2H), 7.54–
7.58 (m, 1H), 7.57 (d, J¼8.7 Hz, 1H), 7.60–7.65 (m, 1H),
7.73–7.76 (m, 1H), 7.86–.88 (m, 1H), 7.90 (d, J¼8.7 Hz,
1H); dC¼148.8, 132.1, 130.7, 129.0, 128.1, 128.0, 127.2,
126.8, 125.1, 121.4, 34.3, 31.3, 21.7, 13.5; m/z (%): 262

´
Z. Wrobel / Tetrahedron 59 (2003) 101–110
109
(5.8), 261 (35.4), 232 (23.3), 214 (5.8), 205 (16.0), 198
(3.6), 197 (21.6), 196 (7.0), 190 (4.9), 189 (9.3), 188 (59.3),
182 (36.6), 172 (11.7); nmax (KBr): 2962.9, 2928.4, 2861.2,
1624.9, 1584.3, 1515.9, 1334.2, 1229.0, 1129.6, 1097.6,
861.1, 804.5, 793.3. Anal. calcd for C14H15NO2S [261.34]:
C, 64.34; H, 5.78; N, 5.36; S, 12.27%; found: C, 64.41; H,
5.67; N, 5.37; S, 12.23%.
obtained. Compound 10a: off white solid; mp 109–1118C.
dH¼0.87 (t, J¼7.3 Hz, 3H), 0.98 (t, J¼7.3 Hz, 3H), 1.40–
1.46 (m, 2H), 1.50–1.60 (m, 4H), 1.72–1.80 (m, 2H), 2.85
(t, J¼7.5 Hz, 2H), 3.02 (t, J¼7.5 Hz, 2H),.39 (d, J¼7.8 Hz,
1H), 7.43 (ddd, J¼8.0, 6.8, 1.2 Hz, 1H), 7.55 (ddd, J¼8.4,
6.8, 1.2 Hz, 1H), 7.77–7.80 (m, 2H), 8.61–8.63 (m, 1H);
dC¼143.7, 136.0, 131.4, 129.4, 128.3, 128.0, 127.3, 125.7,
125.0, 122.8, 35.8, 32.4, 32.1, 31.3, 31.1, 33.5, 22.4, 114.0,
13.9; nmax (KBr): 3051.8, 2956.2, 2924.3, 2870.3, 2856.5,
1614.9, 1578.7, 1496.5, 1463.4, 1434.6, 1420.9, 1375.9,
1223.3, 1118.9, 979.4, 857.8, 809.4, 797.3, 771.0, 747.6;
m/z (%): 306 (8.1), 305 (16.7), 304 (77.8), 250 (9.7), 249
(17.0), 248 (100.0), 215 (5.3), 214 (10.3), 194 (7.3), 193
(12.1), 192 (80.4), 191 (31.3), 190 (29.8), 172 (7.0), 171
(12.4). Anal. calcd for C18H24S2 [304.52]: C, 71.00; H, 7.94;
S, 21.06%; found: C, 70.82; H, 8.01; S, 21.04%.
40-(1-Butylthio)-10-nitronaphthalene 9b. Yellow solid; mp
56–588C (hexane). dH¼0.98 (t, J¼7.3 Hz, 3H), 1.50–1.59
(m, 2H), 1.76–1.84 (m, 2H), 3.13 (t, J¼6.7 Hz, 2H), 7.35 (d,
J¼8.3 Hz, 1H), 7.60–7.66 (m, 1H), 7.71–7.76 (m, 1H),
8.21 (d, J¼8.3 Hz, 1H), 8.37 (ddd, J¼8.4, 1.1, 0.6 Hz, 1H),
8.69 (ddd, J¼8.8, 1.1, 0.6 Hz, 1H); dC¼145.7, 143.4, 131.6,
129.7, 127.2, 125.3, 124.6, 124.1, 123.9, 119.9, 32.0, 30.3,
22.2, 13.6; nmax (KBr): 2964.6, 2926.1, 2864.3, 1559.3,
1503.8, 1418.2, 1322.3, 1304.1, 1260.1, 1197.8, 1164.1,
933.3, 776.5, 766.2; m/z (%): 263 (6.3), 262 (17.2), 261
(100.0), 207 (3.2), 206 (7.6), 205 (59.3), 204 (5.3), 201
(8.1), 188 (3.9), 175 (14.5), 171 (12.9), 159 (14.7), 158
(10.5). Anal. calcd for C14H15NO2S [261.34]: C, 64.34; H,
5.78; N, 5.36; S, 12.27%; found: C, 64.61; H, 5.58; N, 5.52;
S, 12.33%.
3.3.2. Reaction of 40-butylthio-10-nitronaphthalene 9b
with n-butylthiol 2c. Nitroarene 9b (130 mg, 0.5 mmol)
was dissolved in dry DMF (10 mL) and treated with
BTMSA (320 mL, 1.25 mmol), n-butylthiol 2c (280 mL,
2.5 mmol) and DBU (500 mL, 3.75 mmol). The mixture was
stirred at room temperature for 21 days. After standard work
up followed by column chromatography, 10,40-di-(1-
butylthio)naphthalene 10b (55 mg, 36%) was obtained as
the only isolable product. Compound 10b: dH¼0.92 (t, J¼
7.4 Hz, 6H), 1.44–1.52 (m, 4H), 1.61–1609 (m, 4H), 2.95 (t,
J¼7.4 Hz, 4H), 7.48 (0s, 2H), 7.570 (AA part of AA0XX0
system, 2H), 8.43 (XX part of AA XX0 system, 2H); dC¼
133.2, 133.0, 127.3, 126.5, 125.7, 34.0, 31.2, 22.0, 13.7;
3.2.3. Step c. (1) Sulphide 9a (65 mg, 0.25 mmol) was
dissolved in EtOH (15 mL). SnCl2·2H2O (680 mg, 3 mmol)
was added and the mixture stirred and refluxed for 20 h.
After pouring onto satd aq. NaHCO3 solution (20 mL), the
solid material was filtered off and washed with AcOEt, and
the filtrate was extracted with AcOEt. The combined
organic solutions were washed with water, dried with
MgSO4, concentrated and chromatographed to yield
10-amino-20-(1-butylthio)naphthalene 4ac0 (304 mg, 53%)
as a yellow oil. dH¼0.88 (t, J¼7.4 Hz, 3H), 1.35–1.45 (m,
2H), 1.50–1.60 (m, 2H), 2.79 (t, J¼6.6 Hz, 2H), 5.01 (broad
s, 2H), 7.21 (dd, J¼8.6, 0.4 Hz, 1H), 7.44–7.50 (m, 3H),
7.74–7.78 (m, 1H), 7.79–7.83 (m, 1H); nmax (film): 3464.7,
3357.7, 3053.0, 2957.2, 2928.4, 2971.0, 1602.5, 1503.7,
1403.7, 1376.4, 858.5, 796.6, 738.3; m/z (%): 233 (3.8), 232
(12.0), 231 (69.6), 176 (10.6), 175 (58.2), 174 (100.0), 147
(10.1), 144 (4.4), 143 (23.5); HRMS: calcd for C14H17NS:
[231.1082]; found: 231.1084.
n
max (film): 3469.4, 2957.5, 2929.3, 2871.3, 1567.1, 1463.9,
1367.5, 1192.2, 992.3, 820.3, 758.6; m/z (%): 306 (10.6),
305 (20.5), 304 (100.0), 249 (5.3), 248 (19.2), 247 (28.3),
193 (5.0), 192 (19.2), 191 (33.8), 190 (4.6). Anal. calcd for
C18H24S2 [304.52]: C, 71.00; H, 7.94; S, 21.06%; found: C,
71.05; H, 7.87; S, 21.26%.
3.4. Reaction of 1a with 2a arrested on the stage of 20,40-
di-(1,1-dimethyletylthio)-10-hydroxylaminonaphthalene
11 (Scheme 5)
Reaction was performed according to the general procedure.
After 30 min of stirring at room temperature the mixture
was quenched with 50 mL of satd aq. NH4Cl solution. A
stream of Ar was bubbled through the mixture for 1 h to
remove the excess of mercaptan and other volatile
substances. The mixture was then extracted with AcOEt
(3£50 mL) and dried over MgSO4. Evaporation of the
solvent followed by recrystallisation of the residue from
hexane gave product 11 (425 mg, 50%), as unstable light
yellow crystals containing small amounts of impurities; 1H
NMR spectra both in CDCl3 and benzene-d6 exhibited
broadened signals because of the presence of dynamic
system: dH (CDCl3)¼1.30 (s, 9H), 1.37 (s, 9H), 5.49 (s, 1H),
7.51–7.65 (m, 2H), 7.95 (s, 1H), 8.40–8.48 (m, 1H), 8.66
(s, 1H), 8.68–8.80 (m, 2H); dH (C6D6)¼1.17 (s, 9H), 1.19
(s, 9H), 5.85 (s, 1H), 7.35–7.43 (m, 2H), 8.19 (s, 1H), 8.59
(d, J¼7.6 Hz, 1H), 8.70 (s, 1H), 8.96 (d, J¼8.6 Hz, 1H);
(2) Sulphide 9b (22 mg, 0.08 mmol) was dissolved in
AcOEt (3 mL) and treated with SnCl2·2H2O (90 mg,
0.4 mmol). After stirring at room temperature overnight,
the reaction mixture was diluted with AcOEt (30 mL), and
washed with satd aq. NaHCO3 solution (10 mL). Column
chromatography afforded 8 mg (43%) of product with both
1
MS and H NMR spectra superimposable with those of
10-amino-40-(1-butylthio)naphthalene 4ac.
3.3. Reaction of 20 and 40 1-nitronaphthalenes with
n-butylthiol 2c (Scheme4)
3.3.1. Reaction of 20-butylthio-10-nitronaphthalene 9a
with n-butylthiol 2c. Nitroarene 9a (262 mg, 1 mmol) was
dissolved in dry DMF (20 mL) and treated with BSA
(640 mL, 2.5 mmol), n-butylthiol 2c (560 mL, 5 mmol) and
DBU (500 mL, 3.75 mmol). The mixture was stirred at room
temperature for 15 days. After0standard work up followed
by column chromatography 1 ,20-di-(1-butylthio)naphtha-
lene 10a (152 mg, 50%) and amine 3ac (28 mg, 9%) were
n
max (film): 3341.4, 3210.3, 3065.6, 2967.4, 2897.3, 2862.4,
1557.8, 1493.6, 1457.9, 1364.4, 1166.0, 1105.2, 1048.4,
875.3, 763.8, 670.6; m/z (%): 335 (,1), 320 (5.6), 319
(24.4), 263 (13.3), 221 (5.8), 220 (11.1), 209 (9.5), 208
(15.8), 207 (100.0), 206 (23.0), 205 (8.4), 175 (5.5), 174

´
Z. Wrobel / Tetrahedron 59 (2003) 101–110
110
(32.7); LSIMS: 335 (Mþ), 319, 307, 289, 278, 262; LSIMS
HR: calcd for C18H25ONS2: [335.1378]; found: 335.1371.
Acknowledgements
This study was funded by the State Committee of Scientific
Research Grant No. PBZ 6.01.
Product 11 treated with BSA (2.5 equiv.) and DBU
(5 equiv.) in DMF solution for 4 days at room temperature
according to the general procedure afforded 3aa in a 63%
yield.
References
3.5. Reactions of 1a with 2a terminated with external
reducing agents (Scheme 8)
1. Paradisi, C.; Scorrano, G. Acc. Chem. Res. 1999, 32, 958–968.
2. Chupakhin, O. N.; Charushin, V. N.; van der Plas, H. C.
Nucleophilic Aromatic Substitution of Hydrogen. Academic:
San Diego, 1994.
The first stage of reaction was performed as in Section 3.4
on a 1 mmol scale but the reaction was quenched after
30 min with aq. satd NaHCO3 (10 mL).
3. Terrier, F. Nucleophilic Aromatic Displacement. VCH: New
York, 1991.
Procedure a. At this point Na2S2O4 (870 mg, 5 mmol) and
the mixture stirred at 608C for 3 h. Usual work up followed
by chromatography yielded 3aa (168 mg, 53%).
4. Zlotin, S. G.; Kislitsin, P. G.; Samet, A. V.; Serebriakov, E. A.;
Konyushkin, L. D.; Semenov, V. V. J. Org. Chem. 2000, 65,
8430–8438.
5. Serushkina, O. V.; Dutov, M. D.; Shevelev, S. A. Russ. Chem.
Bull. 2001, 50, 261–264.
Procedure b. The mixture was extracted with AcOEt extract
evaporated, the residue dissolved in AcOH (10 mL). Zn dust
(650 mg, 10 mmol) was added and the mixture was refluxed
with stirring for 30 min. Work up followed by column
chromatography yielded 3aa (180 mg, 55%).
6. Kawakami, T.; Suzuki, H. J. Chem. Soc. Perkin Trans. 1 2000,
3640–3644.
´
7. Wrobel, Z. Tetrahedron Lett. 1997, 38, 4913–4916.
´
8. Wrobel, Z. Tetrahedron 1998, 54, 2607–2618.
´
9. Wrobel, Z.; Eur, J. Org. Chem. 2000, 521–525.
3.6. Reaction of 1-nitroso-2-naphthol 19 with
1,1-dimethylethylthiol 2a (Scheme 7)
10. It was found that 4-chloronotrobenzene reacts with phenyl-
acetonitrile in NaOH/aq. MeOH solution to form 3-phenyl-2,
1-benzisoxazole via replacement of ortho-hydrogen atom
followed by further steps, whereas in DBU/DMF system only
40-(1-cyano-1-phenylmethyl)nitrobenzene resulted from sub-
stitution of chlorine was detected. After adition of MgCl2 to
the later system only 3-phenyl-2,1-benzisoxazole was isolated
To a stirred solution of 1-nitroso-2-naphthol 19 (173 mg,
1 mmol), t-BuSH 2a (550 mL, 5 mmol) in DMF (15 mL),
BSA (640 mL, 2.5 mmol) and DBU (1 mL, 7.5 mmol) were
added. After stirring for 3 days at room temperature the
reaction mixture was worked up according to standard
procedure. Column chromatography gave product 20
(211 mg, 85%).
´
Wrobel, Z. Pol. J. Chem. 1998, 72, 2384–2388.
´
11. Wrobel, Z. Tetrahedron Lett. 2000, 41, 7365–7366.
´
12. Wrobel, Z. Tetrahedron 2001, 57, 7899–7907.
13. Eyer, P.; Gallemann, D. Reactions of Nitrosoarenes with SH
Groups. In The Chemistry of Amino, Nitroso, Nitro and
Related Groups. Patai, S., Ed.; Wiley: New York, 1996; pp
999–1039 Supplement F2.
10-Amino-40-(1,1-dimethylethylthio)-20-hydroxynaphtha-
lene 20. dH (DMSO-d6)¼1.20 (s, 9H), 5.31 (broad s, 2H),
7.27–7.34 (m, 2H), 7.39 (s, 1H), 8.00–8.03 (m, 1H), 8.43–
8.46 (m, 1H), 9.13 (broad s, 1H); dC¼137.8, 131.8, 131.6,
128.3, 126.9, 123.7, 123.6, 123.0, 121.8, 114.4, 46.7, 30.8;
14. Schmidt, M. J. Prakt. Chem. 1890, 42, 156–158.
15. Schmidt, M. J. Prakt. Chem. 1891, 44, 522–523.
16. Boeniger, M. Chem. Ber. 1894, 27, 23–25.
17. Andersen, K. K. Sulphonic Acid and Their Derivatives. In The
Synthesis and Reactions of Organic Compounds. Compre-
hensive Organic Chemistry, Sir Barton, D., Ed.; Pergamon:
Oxford, 1979; p 336.
n
max (KBr): 3354.3, 3287.8, 3064.3, 2984.4, 1619.6, 1605.3,
1562.9, 1507.7, 1434.5, 1362.6, 1348.3, 1270.2, 1246.4,
1168.4, 1029.2, 958.2, 940.6, 888.3, 861.1, 759.0; m/z: 248
(3.5), 247 (21.6), 193 (5.5), 192 (12.6), 191 (100.0), 190
(11.6), 162 (6.7), 159 (13.3), 158 (5.0), 146 (15.1). Anal.
calcd for C14H17NOS [247.36]: C, 67.98; H, 6.93; N, 5.66;
S, 12.96%; found: C, 68.12; H, 6.92; N, 5.91; S, 13.22%.
18. Ma˛kosza, M.; Sienkiewicz, K. J. Org. Chem. 1998, 63,
4199–4208.