Preparation of new O-Alkyl naphthalenecarbothioates and alkyl naphthalenecarbodithioates, and EPR-spectroscopic study of their radical anions1,2

Article abstract of DOI:10.1080/10426507.2010.490151

O-Alkyl naphthalenecarbothioates and bis-carbothioates are prepared by the reaction of the corresponding esters by use of Lawesson's reagent. The related naphthalenecarbodithioates are obtained (a) from methylnaphthalenes via bromination with NBS, subsequent methoxide-promoted reaction with sulfur, and finally alkylation of the carbodithioate salts with alkyl halides or (b) lithiation of bromonaphthalenes, reaction with carbon disulfide, and alkylation. The thiono- and dithioesters were transformed into persistent radical anions by in situ electroreduction. Spin density distributions were determined by EPR spectroscopy and MO calculations. Copyright Taylor & Francis Group.

Full text of DOI:10.1080/10426507.2010.490151

Phosphorus, Sulfur, and Silicon, 185:1273–1300, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.490151
PREPARATION OF NEW O-ALKYL
NAPHTHALENECARBOTHIOATES AND ALKYL
NAPHTHALENECARBODITHIOATES, AND
EPR-SPECTROSCOPIC STUDY OF THEIR RADICAL
ANIONS1,2
Ju¨rgen Voss, Karsten Strey, Thomas Maibom,
Manfred Krasmann, and Gunadi Adiwidjaja
Department of Chemistry, University of Hamburg, Hamburg, Germany
O-Alkyl naphthalenecarbothioates and bis-carbothioates are prepared by the reaction of the
corresponding esters by use of Lawesson’s reagent. The related naphthalenecarbodithioates
are obtained (a) from methylnaphthalenes via bromination with NBS, subsequent methoxide-
promoted reaction with sulfur, and finally alkylation of the carbodithioate salts with alkyl
halides or (b) lithiation of bromonaphthalenes, reaction with carbon disulfide, and alkylation.
The thiono- and dithioesters were transformed into persistent radical anions by in situ
electroreduction. Spin density distributions were determined by EPR spectroscopy and MO
calculations.
Keywords O-Alkyl naphthalenecarbothioates; in situ electroreduction; MO calculations; naph-
thalenecarbodithioates; radical anions; spin densities
INTRODUCTION
We published EPR spectroscopic studies on the radical anions of naphthalene-3 and
anthracenecarboxylic esters4 several years ago. Furthermore, we have investigated the spin
density distributions in the radical anions of various types of thiocarbonyl compounds
(“thioketyls”) for decades.5–9 The aim of our experiments and of the corresponding theo-
retical calculations was to explore the characteristic changes of the spin densities which are
brought about through the replacement of oxygen by the significantly larger and thus easier
to polarize sulfur atoms in a compound. As a result of these investigations, we have found
that the thiono derivatives of carboxylic esters and amides were transformed into the radical
anions at much lower one-electron reduction potentials as compared with the oxo analogs.7
Thiocarbonyl and, even more pronounced, dithiocarboxylate substituents turned also out to
Received 12 January 2009; accepted 18 April 2009.
Dedicated to Professor Naomichi Furukawa on the occasion of his 70th birthday.
The Universita¨t Hamburg and the Fonds der Chemischen Industrie are gratefully acknowledged for financial
support. We thank Prof. Dr. U. Behrens (X-ray), Dr. Volker Sinnwell (NMR spectroscopy), and Manfred Didschun
(preparations) at the Universita¨t Hamburg for their competent assistance.
Address correspondence to Prof. Dr. Ju¨rgen Voss, Department of Chemistry, University of Hamburg, Martin-
Luther-King-Platz 6, D-20146 Hamburg, Germany. E-mail: voss@chemie.uni-hamburg.de
1273

1274
J. VOSS ET AL.
exhibit significantly stronger electron-withdrawing effects. Due to this effect, the spin den-
sity in the benzene moiety of benzoate derived radical anions considerably decreases in the
order ester > thionester > dithioester7 and also amide > thioamide.9 The spin-attracting
power of the dithiocarboxylate group is even surpassed by the α-oxo-dithiocarboxylate
substituent in 2-phenyl-2-oxo-ethanedithioate esters10–13 and the corresponding amides
and thioamides.12 Alternatively, we have found that ester substituents withdraw signifi-
cantly less spin density from the extended delocalized π-electron systems of naphthalene-3
and anthracenecarboxylate radical anions4 as compared with the corresponding benzoates.
Since we were interested in the balance between these two competing effects, we
have investigated the radical anions of thiono- and dithionaphthoate esters, which exhibit
both an extended π-electron system and an effective spin-withdrawing substituent in one
molecule. For comparison, we have also included derivatives with two of these functional
groups.
RESULTS AND DISCUSSION
Preparations
O-Ethyl naphthalene-1-carbothioate (1b)14–16 and O-ethyl naphthalene-2-
carbothioate (2b)15,17 are described in the literature. We needed, however, further
thionesters for our study and have also prepared 1a, 1c, 1e, 2a, 2c, and 3–8 (Scheme 1)
by thionation of the corresponding esters with 2,4-bis(4-methoxyphenyl)-1,3,2,4-
dithiadiphosphetane 1,3-disulfide (Lawesson’s reagent, LR).15,18
The yields were low in several cases, but most of the desired thionesters could be
1
obtained in sufficient amounts. The H and 13C NMR data (Table VI and VII) are in
agreement with the structures. For the sake of completeness and comparison, the data
of 1b and 2b are also included. The assignment of the signals was achieved by DEPT-
1
1
135 or H-1H- and H-13C-COSY experiments. It was corroborated by comparison of
the observed chemical shifts with theoretical values, which were calculated by use of
increments for naphthalene and the respective substituents.19 The 13C shift increments for
the CS substituent (ꢀδipso = 16.6, ꢀδortho = −1.7, ꢀδmeta = −0.1, ꢀδpara = 3.9 ppm) were
derived from the spectra of related reference compounds.20–22 When we prepared 1b and
1c, we found small amounts of their isomers 2b and 2c as byproducts. This was due to a
contamination of the commercial α-naphthoic acid, which we had used as starting material.
We found a content of 10% β-naphthoic acid by a careful 1H NMR spectroscopic analysis of
the methyl esters. Fortunately, the pairs of isomers could be separated by chromatography to
yield in one batch both the thionesters as pure compounds. The thionester 1e was prepared
from 2,6-di-tert-butyl naphthalene via bromination, lithiation, carboxylation, esterification,
and finally thionation of the ester 1d with LR according to Scheme 2.3,23
Thionation of diisopropyl naphthalene-1,5-dicarboxylate led to a separable mixture
of the mono- (4a) and the bisthionester (4b), although we applied a 50% stoichiometric
excess of LR, which is known to transfer, in general, two sulfur atoms per molecule to the
carbonyl compound. The product ratio was 30:1 in favor of the mono-thionester 4a, and
the total yield was only 23%. Possibly this is due to steric hindrance, which impedes the
attack of the bulky LR molecule at the isopropyl α-naphthoate moiety. Also the mono- and
bis-thionesters 7a and 7b as well as 8a and 8b were obtained as separable mixtures when
the corresponding esters were treated with LR.18 In these cases, the total yields were high
and more bis-thionester was formed, even though only a 10–20% excess of LR was used.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1275
S
OR1
S
R2
OR
R2
1a: R1 = Me, R2 = H
1b: R1 = Et, R2 = H
1c: R1 = iPr, R2 = H
1e: R1 = Ph, R2 = tBu
2a: R = Me
2b: R = Et
2c: R = iPr
S
S
X
S
OiPr
S
OR
MeO
OMe
5
iPrO
S
OR
3a: R = Me
3b: R = Ph
4a: X = O
4b: X = S
S
X
OEt
OEt
OR
RO
S
S
S
7a: X = O, R = Me
7b: X = S, R = Me
7c: X = S, R = iPr
6
X
iPrO
OiPr
8a: X = O
8b: X = S
Scheme 1 O-Alkyl naphthalenecarbothioate esters 1–8.
The dithionaphthoates 9a,24–26 9c,24,26,27 10a,28–30 10b,26,31 and 13a32 are known
compounds. Besides these five dithioesters, we have synthesized the naphthalenecarbo-
dithioates 9b, 9d, 9e, 12a, and 12b as well as the naphthalene-bis-carbodithioates 11a, 11b,
11c, 12c, and 13b (Scheme 3).
Most of these dithioesters were prepared by reaction of the corresponding (bro-
momethyl)naphthalenes with sulfur and sodium methoxide, and subsequent alkylation.33,34

1276
J. VOSS ET AL.
Br
tBu
tBu
(1)
(2), (3), (4)
tBu
tBu
O
OPh
S
OPh
tBu
tBu
(5)
tBu
tBu
1d
1e
Scheme 2 (1): Br2/(MeO)3PO; (2): nBuLi/Et2O; (3) CO2; (4): PCl5; (5): PhOH/pyridine/DMAP;
(6): LR/C6H5Cl.
SR1
S
S
SR
R2
9a: R1 = Me, R2 = H
9b: R1 = CD3, R2 = H
10a: R = Me
10b: R = Et
9c: R1 = Et, R2 = H
9d: R1 = Me, R2 = tBu
9e: R1 = Et, R2 = Me
S
SR
SR
S
S
SR
RS
XR
S
S
X
11a: R = Me, X = S
11b: R = CD3, X = S
12a: R = Me, X = Br
12b: R = Et, X = Br
13a: R = Me
13b: R = Et
11c: R = CH2Ph, X = O
12c: R = Me, X = CS−SMe
Scheme 3 Naphthalenecarbodithioate esters 9–13.
In the case of the 1,3-dibenzyl derivative, only one bromomethyl group reacted as expected,
whereas the second one was transformed into a thionoester group according to the analytical
and spectroscopic data of the product (see the Experimental section and Tables IX–XI). We
tentatively assigned the structure 11c to the trithioester. The 4-bromo derivatives 12a and
12b were obtained by unintentional mono-lithiation of 1,4-dibromonaphthalene, subsequent
reaction with carbon disulfide, and alkylation of the dithiocarboxylate with iodomethane

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1277
or iodoethane. The Grignard reaction did not work in this case. Neither were we able to
achieve a di-metallation of 1,4-dibromonaphthalene. The desired 12c could, however, be
prepared from 1,4-bis(bromomethyl)naphthalene by the above-mentioned alternate method.
The dithioester 9d was synthesized from 2-tert-butyl-naphthalene via the ketone 14, the
pyridinium salt 15, and the reaction of the carboxylic acid 16 with 2,4-bis(methylsulfanyl)-
1,3,2,4-dithiadiphosphetane 2,4-disulfide (“Davy’s reagent,” DR35) according to Scheme 4.
-
I
N
O
Me
O
+
(2)
tBu
(1)
tBu
tBu
14
15
O
OH
SCH3
S
(4)
tBu
(3)
15
tBu
16
9d
Scheme 4 (1): AcCl/AlCl3; (2): I2/pyridine; (3): a) NaOH, b) HCl; (4): DR.
The 1H and 13C NMR data of the naphthodithioates (Tables IX and X) are in agreement
with the structures. The signals were assigned as described for the thionesters.19–21 The
structure of 9d and accordingly of its precursors was, furthermore, corroborated by an
X-ray structure analysis (Figure 1).
Electroanalytical Results
Radical anions of thionesters and dithioesters in the benzene and other series exhibit
considerable stabilities.7 Their persistency is significantly enhanced compared with the
radical anions of the corresponding esters or thiolesters.36 We have now determined the half-
wave reduction potentials E1/2 of the single-electron transfer (SET) steps for selected thion-
and dithioesters in the naphthalene series by differential pulse polarography (DPP). They
represent a measure of the thermodynamic stability of the corresponding radical anions,
whereas the ratios of the aniodic and cathodic cyclovoltammetric (CV) peak currents, iap/icp,
which were determined by the approximate method of Nicholson,37 correspond with their
kinetic stabilization (“persistency”). The results are compiled in Table I.
Inspection of Table I shows that, in general, O-alkyl naphthothioates exhibit a re-
versible SET step at a low potential, which only slightly depends on the nature of the
O-alkyl group (cf. 1a vs. 1b and 2a vs. 2b). The reduction potentials E1/2 of the thion-
esters are shifted significantly to less negative values as compared with the corresponding
esters (1a: E1/2 = −0.95 V; methyl α-naphthoate: E1/2 = −1.40 V3). This effect is due to
the pronounced polarizability of the thiocarbonyl group, although one could think of the

1278
J. VOSS ET AL.
Figure 1 ORTEP view of the X-ray diffraction structure of 9d (one of the two independent molecules in the cell
is shown) with atom numbering. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms are
not shown. Relevant bond lengths of both the molecules (pm): C-1−C11: 147.8/148.6, C-11−S-11: 162.9/161.9,
C-11−S-12: 171.9/172.6, C-12−S-12: 178.2/179.2; bond angles (◦): S-11−C-11−S-12: 125.9/125.9, C-11−S-
12−C-12: 104.7/105.6, and torsion angle (◦): C-2−C-1−C-11−S-11: 109.0/110.8.
reverse effect on account of the higher electronegativity of oxygen compared with sulfur.
The naphthalene derivative 1a is also reduced at a less negative potential than O-methyl
benzothioate (E1/2 = −1.09 V7), which should be due to the more extended naphthalene
π-electron system of 1a. The 2,6-bis-thionester 7b is even easier to reduce. Its potential is
shifted in the anodic direction by 0.35 V as compared with 2a. Furthermore, 7b exhibits
a second reversible SET step at −0.88 V, which is due to the formation of a persistent
diamagnetic dianion (Scheme 5). The same is true for the mono-thionester 7a. Second re-
duction steps at E1/2 ≤ −1.30 V are also observed for the mono-thionesters 1a, 1b, 2a, 2b,
and 2c and the 2,7-bis-thionester 8a. These are, however, irreversible due to rapid follow-up
reactions of the dianions.
−
−
S
S
−
−
−
−
e
e
OMe
OMe
7b
MeO
MeO
−e
−e
−
.
S
S
Radical Anion
Dianion
Scheme 5 Dianion of O,O-dimethyl naphthalene-2,6-bis(carbothioate) 7b.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1279
Table I Polarographic half-wave potentials E1/2 [V]a and cyclovoltammetric peak ratios iap/icp of selected
naphthothioates and naphthodithioates
Compound
E1/2(1)
iap/icp(1)
0.60
E1/2(2, 3, 4)
iap/icp(2)
1a
1b
2a
2b
2c
7a
7b
8a
−0.95
−0.82
−0.91
−0.87
−0.95
−0.68
−0.56
−0.80
−0.78
−0.52
−0.49
−0.60
−0.65
−0.63
−0.64
−0.35
−0.32
−1.38
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
0.95
0.95
−1.32
−1.30
0.69
−1.52
−1.50
0.95
0.85
−1.13
−0.88
0.44
−1.38
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
9e
0.76
0.95
0.90
Irreversible
Irreversible
Irreversible
0.86
0.87
0.83
−1.34
11a
11b
11c
12a
12b
12c
13a
13b
−0.70, −0.89
−0.70, −0.89
−1.35
−0.75, −1.30
−0.75, −1.31
−1.32
−0.52, −1.06, −1.43
−0.59, −1.13, −1.34
aMeasured by use of an internal Ag/Ag+/AgBr/Br− reference electrode in DMF, the potential of which is
shifted by −0.55 V vs. the aqu. SCE.
The peak current ratios ipa/ipc are ≥ 0.6.37 As a rule of thumb, radical anions are
stable enough for successful EPR measurements if ipa/ipc is ≥ 0.4. Thus, we expected good
EPR results after in situ electroreduction of the naphthothioates at room temperature.
The first SET steps of the dithionaphthoates occur at even less negative potentials
than those of the corresponding thionesters (cf. 1b/9e and 7b/13a in Table I), whereas
only a marginal difference between 9e (E1/2 = −0.78 V) and methyl dithiobenzoate
(E1/2 = −0.80 V7) exists. The peak current ratios of ipa/ipc ≥ 0.76 are indicative of a
considerable persistency of the radical anions. We have observed the lowest reduction
potential for the SET of diethyl 2,6-bis-dithionaphthoate 13b (E1/2 = −0.32 V). The 1,3-
dibenzyl derivative 11c and the 4-bromonaphthodithioates 12a and 12b do not exhibit
reversible reduction steps. Even the first SET steps at E1/2 = −0.60 V (11c) and E1/2
=
−0.63/−0.60 V (12a/12b) are irreversible. This is not unexpected, since radical anions of
benzyl esters exhibit a tendency to eliminate resonance-stabilized benzyl radicals38 unless
they are stabilized by particular effects, e.g., conjugation with carbonyl groups as in benzyl
2-oxo-2-phenylethanedithioate.11 Bromoarene radical anions are also known to be a rather
elusive species. O-Phenyl 2-bromobenzothioate and 4-bromobenzothioate thus show only
quasireversible SET steps. Due to the high spin and negative charge densities in the ortho-
and the para-positions and the resulting weak carbon–bromine bonds, bromide anions are
easily eliminated. The radical anions of O-phenyl 3-bromobenzothioate can, however, be
detected, as no destabilization of the C-Br bond occurs in the meta-position.39,40 These
aspects are further discussed in the EPR section (see below). In addition, all dithionaph-
thoates studied exhibit further irreversible reduction steps at more negative potentials (see
Table I).

1280
J. VOSS ET AL.
EPR Spectroscopy and MO Calculations
Thionester radical anions. In contrast to the naphthoate esters,3 the correspond-
ing thionesters gave less persistent radical anions. We were, for instance, not able to record
EPR spectra of the naphthalene-1,4-bis(carbothioate) radical anions 3a−• and 3b−•, or of
the 2,3-isomer 6−•. In other cases, the lability of the radical anions led to decomposition
products and, as a consequence, to asymmetric spectra, which could not easily be analyzed
and interpreted. Furthermore, the heavy-atom effect of the sulfur caused line-broadening.
Thus several spectra were not well resolved. Figure 2 shows the EPR spectrum of 1e−• as
an example.
The spectrum of 4a−•, on the other hand, exhibits sharp lines. Obviously the additional
doublet splittings observed in the low-field wings of the three pronounced multiplets result
from an unknown impurity (see Figure 3).
The g-factors of the O-alkyl naphthothioate radical anions 1c−• (2.0060), 4a−•
(2.0051), 7c−• (2.0054) and, in particular, of the bis-naphthothioate 8a−• (2.0068) are
enhanced compared with the g-factors (≈ 2.0032–2.0037) in the naphthoate series.3 This
increase is caused by the spin-orbit coupling (heavy-atom effect) of the thiocarbonyl sulfur
atom (ζS = −382 cm−1). The calculation of π-spin densities ρµπ from g-factors is not
straightforward, although a quantitative relationship between ρπµ, g, the spin-orbit cou-
pling constant ζ, and the electronic excitation energy ꢀE(n → π∗) exists.41,42 However,
Figure 2 Experimental (top) and simulated (bottom) EPR spectrum of the O-phenyl 3,7-di-tert-butylnaphthalene-
1-carbothioate radical anion 1e−•
.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1281
Figure 3 Experimental (top) and simulated (bottom) EPR spectrum of the O,S-diisopropyl naphthalene-1,5-bis-
carbo-monothioate radical anion 4a−•
.
ꢀE(n → π∗) of radical anions is not easy to determine, and, furthermore, the correct
symmetry of the g-tensor must be known and taken into account. But in a semiquantitative
sense, the increase of the g-factor is indicative of a considerable π-spin density in the
thiocarbonyl group. The same increase of g-factors has been observed and discussed for
benzoate esters and benzamides, and the corresponding sulfur and selenium analogs.7,9,36,43
The proton hfs coupling constants aHµ of the thionester radical anions are compiled
in Table II. The assignment of the observed coupling constants aHµ to distinct positions µ
Table II EPR spectroscopic proton HFS coupling constants aHµ (mT) in the thionester radical anions [C10H7-
CS-OR1]•− and [R1O-CS-C10H6-CX-OR2]•−, and the radical 17
Compound a(1-H) a(2-H) a(3-H) a(4-H) a(5-H) a(6-H) a(7-H) a(8-H)
a(R1)
a(R2)
a
1a
1b
1e
2a
2c
4a
7a
7b
7c
8a
17
—
—
—
0.592
0.595
0.595
—
—
0.032
—
—
—
—
0.336
0.663
0.663
0.610
0.090
0.090
0.046
0.09
0.183
0.183
0.136
0.090
0.090
—
0.21
0.22
0.236
0.196
0.581
0.042
0.046
0.069
0.310
0.327
0.515
—
0.250
0.246
—
0.045
0.045
0.063
0.063
0.069
0.383
0.365
0.661
0.09
0.167
0.129
0.069b
0.122
0.045
0.015a
0.09
—
—
—
—
0.017
—
0.045
0.045
0.736
0.736
—
0.21
0.22
0.236
0.478
—
—
a
0.079
0.187
a
a
a
0.030
0.039
0.11
—
0.03
0.039
—
0.11
0.11
0.11
0.118
0.196
0.304
—
0.118
0.478
—
0.039
0.039
a
a
a
a
0.099
0.147
0.573
—
—
aNo resolved splitting observed.
ba(4ꢁ-H).

1282
J. VOSS ET AL.
was not at all straightforward on account of the low symmetry of at least the mono-esters.
Specific substitution of protons by tert-butyl groups44 as in 1e, and variation of the O-alkyl
substituents, in particular the exchange of CH3 by CD3, was helpful. The absence of the
large 0.25 mT and the very small 0.017 mT splitting in the 3,7-di-tert-butyl derivative 1e−•
as compared with 1a−• and 1b−• allows, for instance, an assignment of these two coupling
constants to the 3- or the 7-position. Interestingly, the EPR spectrum of 1e−• can only be
simulated under the presumption of three nearly equal coupling constants of ca. 0.07 mT.
Two of these belong to the naphthalene protons 6-H and 8-H. We assign the third one to the
4ꢁ-position of the O-phenyl substituent. In addition, the McConnell relationship between
aHµ and the π-spin density ρ was used. This finally led to a(3-H) = 0.017 mT and a(7-H) =
0.25 mT for the radical anions 1−•
.
The number and the relative intensities of the lines in the EPR spectrum observed
for 5 are not in agreement with the highly symmetric structure of this compound. Instead
of the three triplets expected for the radical anion 5−•, 42 clearly resolved sharp lines
corresponding to six non-equivalent protons are observed in addition to a number of low
intensity lines that cannot be assigned to the main radical species (see Figure 4).
We tentatively assign this spectrum to the asymmetric tricyclic benzyl-type radical 17,
which might be formed from the primary radical anion 5−• by intramolecular nucleophilic
displacement of a methoxide ion (Scheme 6). We have described the EPR spectroscopic
detection of similar α,α-di-hetero-substituted benzyl radicals such as 18, which are formed
from the radical anions of the corresponding sterically hindered alkyl dithiobenzoates.
These exhibit comparable proton hfs coupling constants (Scheme 6).22
_
S
S
.
.
1.151
SH
.
Me
Me O
S
S
MeS
H
O
OMe
0.573
H
0.336
H
0.395
CMe3
MeO
0.120
H
H
0.147
H
0.099
Me3C
_
.
H
H
H
0.481
5
0.304
0.581
17
18
Scheme 6 Formation of 17 and proton hfs coupling constants a (mT) of 17 and 18.
Dithioester radical anions. As expected, according to the heavy-atom effect of
the sulfur atoms, the naphthodithioate radical anions exhibit even higher g-factors as com-
pared with the thionesters (9a−•: 2.00697; 9b−•: 2.00712; 9c−•: 2.00694; 9d−•: 2.00664;
10a−•: 2.00675).
Their EPR spectra are not well resolved. Figure 5 shows the spectrum of 11a−• as an
example. Several of the coupling constants compiled in Table III are therefore given with
only two decimal digits. Furthermore, very small splittings, which should, e.g., result from
deuterium in the SCD3 groups, are not observable. The corresponding coupling constants
were however included in the simulations to improve the agreement with the experimental
spectra.
The assignment of the observed coupling constants aHµ to distinct positions µ was
achieved in the same way as in the thionester series, i.e., by comparison of suitably substi-
tuted derivatives and by applying the McConnell relationship.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1283
Figure 4 Experimental (top) and simulated (bottom) EPR spectrum of 17.
We have also studied the radical anions of alkyl azulenecarboxylates and -
carbothioates, which are the fascinating isomers and counterparts of the corresponding
naphthalene derivatives. They exhibit a non-alternating aromatic π-electron system and
consequently a particular spin density distribution.45 These results will be published
elsewhere.

1284
J. VOSS ET AL.
Table III EPR spectroscopic proton HFS coupling constants aHµ [mT] in the dithioester radical anions 9•−–13•−
Compound a(1-H) a(2-H) a(3-H) a(4-H) a(5-H) a(6-H) a(7-H) a(8-H)
a(R1)
a(R2)
9a
9b
9c
9d
—
—
—
—
—
0.602
—
—
—
0.20
0.20
0.490
0.49
0.494
0.488
0.49
—
0.09
0.09
0.08
—
0.092
0.13
0.100
—
0.530
0.53
0.527
0.537
0.53
0.205
0.66
0.63
—
0.147
0.13
0.147
0.098
0.10
0.059
0.05
0.049
0.049
0.05
0.130
0.13
0.130
0.098
0.10
0.059
0.05
0.049
0.049
0.06
0.093
0.01a
0.029
0.098
0.03
0.088
0.09
0.01a
0.12
—
—
—
—
—
9e
0.12b
0.006
—
10a
11a
11b
12c
13a
13b
0.175
0.27
0.205
0.08
0.006
0.18
0.253
0.09
—
0.09
0.01a
0.12
0.09
0.06
—
0.29
0.09
0.20
0.09
c
c
c
c
0.08
0.01
0.01
0.04
0.04
0.20
0.20
—
—
0.01
0.01
0.04
0.04
0.09
0.06
—
aaD
.
.
CD3
baH
CH3
cNo resolved splittings observed.
The radical anion of O-methyl anthracene-9-carbothioate was not persistent. Instead,
only the EPR spectrum of the anthraquinone radical anions could be detected after in situ
electroreduction of this thionester.4
Spin density distributions. We have determined the spin density distribution
in the radical anions by use of HMO and semi-empirical (AM1 type) quantum chemical
Figure 5 Experimental (top) and simulated (bottom) EPR spectrum of the dimethyl naphthalene-1,3-
bis(carbodithioate) radical anion 11a−•
.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1285
Table IV Spin densities ρπµ in the O-alkyl naphthothioate radical anions 1−•–4−•, 7−•, 8−•, and the benzyl type
radical 17
Position µ
Compound
ρπµa
1
2
3
4
5
6
7
8
1b
Exp.
0.220
0.144
0.144
0.006
0.017
0.021
0.017
0.012
0.027
0.029
0.054
0.058
0.000
0.007
0.014
0.006
0.060
0.000
0.013
0.037
0.003
0.246
0.185
0.180
0.033
0.040
0.020
0.017
0.023
0.067
0.074
0.054
0.045
0.048
0.084
0.073
0.046
0.113
0.109
0.068
0.073
0.050
0.033
0.029
0.016
0.017
0.012
0.010
0.121
0.073
0.072
0.191
0.119
0.094
0.091
0.048
0.045
0.017
0.005
0.001
0.067
0.082
0.039
0.020
0.007
0.014
0.006
0.060
0.023
0.040
0.027
0.135
0.084
0.049
0.245
0.167
0.152
0.035
0.053
0.045
0.048
0.084
0.177
0.235
HMO
AM1
Exp.
HMO
AM1
Exp.
HMO
AM1
Exp.
HMO
Exp.
HMO
AM1
Exp.
HMO
Exp.
2
0.273
0.212
0.165
4a
0.012
0.010
0.025
7a
7c
0.074
0.113
0.090
0.109
0.089
0.177
0.210
0.109
0.116
0.090
0.109
0.089
0.073
0.048
0.215
0.176
0.109
8a
17
0.000
0.003
0.054
0.003
0.124
0.104
0.212
0.169
HMO
aExp. values as calculated from proton hfs coupling constants aµH by use of the McConnell equation: ρµπ
aHµ/−2.7.
=
calculations. They are compared with experimental values calculated as mentioned above
from McConnell’s relationship aµH = Q·ρπ (Q = −2.7 mT) in Tables IV and V. The
µ
agreement between the experimental and the calculated spin densities is only moderate
in certain cases, in particular for the bifunctional thioesters. In general, it is even better
for the simple HMO type calculations as compared with the results of the more sophisti-
cated semi-empirical methods. We attribute these deviations to the low symmetry of the
mono-substituted naphthalene derivates and to the high number of sulfur centers in the
bis-thioesters, since the parameters especially for thiocarbonyl sulfur atoms are not al-
ways appropriate. Nevertheless, interesting and valid conclusions can be drawn from the
results.
Expectedly, the unpaired electron is mainly located in the thioester part of the
naphthalene-1-carbothioate (1) and -carbodithioate (9) systems. The distribution is sim-
ilar to the thiono- and dithiobenzoate series,7 i.e., the quasi-para (4-) and the quasi-ortho
(2-) positions exhibit the highest spin densities with ρπ4 > ρ2π . We have observed the same
effect in the naphthoate ester series.3 It is more pronounced in 1−• compared with 9−•
.
For instance, ρπ4 (naphthoate ester3) = 0.281 > ρ4π (1−•) = 0.246 > ρ4π (9−•) = 0.196.
The spin density in the unsubstituted part of the radical anions, on the other hand, is not
negligible: ρπ7 = 0.091 and ρ5π = 0.068 in the thionester radical anion 1b−•. The highest
spin densities in the naphthalene-2-carbothioate (2−•) and -carbodithioate (10−•) radical
anions are observed in the 1- (quasi-ortho) positions: ρπ1 (2) = 0.273; ρ1π (10−•) = 0.223.
Somewhat surprisingly, but similar to the naphthoate ester series,3 the 8- and the 6-positions
exhibit however rather high spin densities as well: ρπ8 (2−•) = 0.135; ρ8π (10−•) = 0.094;

1286
J. VOSS ET AL.
Table V Spin densities ρπµ in alkyl naphthodithioate radical anions
Position
Compound
1
2
3
4
5
6
7
8
9a
Exp.a
HMO
AM1
Exp.a
HMO
AM1
Exp.a
HMO
AM1
Exp.a
HMO
AM1
Exp.a
HMO
MNDO
0.181
0.140
0.142
0.034
0.021
0.015
0.002
0.012
0.020
0.196
0.186
0.173
0.076
0.040
0.020
0.244
0.247
0.218
0.054
0.077
0.044
0.065
0.029
0.026
0.100
0.115
0.059
0.000
0.062
0.028
0.074
0.146
0.076
0.022
0.016
0.007
0.076
0.073
0.017
0.030
0.020
0.002
0.000
0.040
0.019
0.048
0.052
0.046
0.002
0.005
0.068
0.066
0.077
0.069
0.000
0.040
0.019
0.004
0.000
0.013
0.022
0.046
0.020
0.094
0.084
0.051
0.033
0.069
0.015
0.000
0.062
0.028
0.015
0.095
0.033
10a
11a
12c
13a
0.223
0.212
0.161
0.033
0.052
0.030
0.030
0.078
0.068
0.030
0.078
0.068
0.004
0.000
0.013
0.074
0.146
0.076
0.015
0.095
0.033
aCalculated from the McConnell equation: ρµπ = aHµ/−2.7.
ρπ6 (2−•) = 0.121; ρπ6 (10−•) = 0.076, whereas very low spin densities are observed in the
second quasi-ortho (3-) positions of 2−• and 10−•
.
The situation is more complicated in the disubstituted radical anions. Obviously,
the spin density distribution in the 1,3-derivatives 11 is predominantly determined by the
dithioester substituent in the 1-position, whereas that in the 3-position plays only a minor
role. Similar to 1, high spin densities are found in the 4- (quasi-para) (ρπ4 = 0.244), 5- (ρ5π =
0.100) and 7-position (ρπ7 = 0.066) of 11−•. The spin density in the 2-position is however
quite low (ρπ2 (11−•) = 0.033) just as in the corresponding ester radical anion (ρπ2 = 0.0123),
although it represents the quasi-ortho position with respect to two thionester groups. The
spin density distribution in the symmetric 2,6-disubstituted thion- and diester radical anions
7−• and 13−• can best be compared with 2−• and 10−•. But the total spin density in the
naphthalene moiety is also low, as one easily recognizes from the low total widths of the
corresponding EPR spectra. This can be explained by the assumption that a large part of
the spin density is localized in the functional groups, i.e., the resonance formulae of type
7b−• shown in Scheme 5 should exhibit particularly high statistic weights. This effect is
even more pronounced in 12c−• with two dithioester groups in the quasi-para positions
of one ring. In this case, no spin densities (resolved proton hfs couplings) whatsoever
are found experimentally in the unsubstituted ring. The corresponding calculated values,
on the other hand, are low but not zero. The MO theory obviously underestimates the
distinct resonance effect of two conjugated thionester groups. In so far, 12c−• strikingly
resembles the monocyclic dimethyl benzene-1,4-bis(carbodithioate) radical anion with
aH2,3,5,6 = aMH e = 0.108 mT.43 The asymmetric radical anion 4a−• exhibits spin density
mainly in the thionester-substituted part of the naphthalene system, as one would expect.
In the asymmetric 2,6- and 2,7-disubstituted counterparts 7a−• and 8a−•, the spin density
is more evenly delocalized over both rings.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1287
Conclusions
A series of novel O-alkyl naphthalene-mono- and -bis-thionesters and alkyl
naphthalene-mono- and -bis-dithioesters has been prepared. The corresponding radical
anions could be generated by in situ electroreduction and studied by EPR spectroscopy. The
spin density distributions in these radical anions as determined from the experimentally
measured proton hfs couplings and from quantum chemical calculations are discussed.
The distributions decidedly depend on the position of the thioester substituents and their
relative orientation in case of the bis-thioester radical anions.
EXPERIMENTAL
Corrected melting points (m p) were determined on an Electrothermal apparatus.
Boiling points (bp) were determined during distillation. Thin layer chromatography (TLC)
was performed on Al foils coated with SiO2 F254 (Merck, Darmstadt). The spots were
detected by the extinction of the fluorescence or by spraying with the iodine/sodium
azide reagent.46 Column chromatography (CC) was performed on Kieselgel 60 (Merck,
Darmstadt), 0.063–0.200 mm (70–230 mesh). Eluents [CCl4, EtOAc, petroleum ether
(PE)] were distilled prior to use. Solvents were purified and dried by standard laboratory
procedures.47
IR spectra were measured as KBr pellets on a Perkin-Elmer FT-IR 1720 X spectrom-
eter. NMR spectra were measured in CDCl3 on Bruker WM 250, WM 400, or AMX 400
spectrometers. Chemical shifts δ are related to SiMe4 (δ = 0.00 ppm) as internal standard.
Coupling constants J are given in Hz. Mass spectra were measured on Varian MAT CH 7
or CH 311 spectrometers at 70 eV. Electroanalytical measurements [differential pulse po-
larograpy (DPP) and cyclovoltammetry (CV)] were performed on a Metrohm polarograpy
setup EA 354 with a Hewlett-Packard plotter HP 7040 A. Half-wave potentials E1/2 (DPP)
and peak potentials (CV) were measured in dry DMF47 containing tetrapropylammonium
bromide (2–5 mg/10 mL) by use of an internal Ag/AgBr reference electrode, the potential
of which is shifted by −0.55 V vs. the aqu. SCE. In situ electrogeneration of the radical an-
ions was achieved with a Bank Electronic (Wenking type) potentiostat MP 31. EPR spectra
were measured in quartz flat cells on Bruker ER 420 S and ESP 300 E spectrometers at
25◦C in dry and purified47 DMF. The EPR spectra were simulated by use of the Symfonia
program (Bruker).
Quantum chemical calculations of the spin densities were performed by use of the
Hu¨ckel 88 or the SHMO48 program (HMO and McLachlan calculations) and the QCPE
software MOPAC 6.0 and MOPAC 93 (MNDO and AM1 calculations).
X-Ray Structure Analysis
The crystal data of 9d and a summary of experimental details are given in Table VI.
Data collection was performed with a CAD 4 SDP (Enraf Nonius) diffractometer with
graphite-monochromated Cu-Kα1 radiation (λ = 1.54184 Å) in the θ/2θ scan mode at
298 K. The structure was solved by the direct method MULTAN49 and differential Fourier
synthesis. Refinement was performed by least squares methods. Due to a disorder of the
tert-butyl group, the H-atoms could not be localized. Crystallographic data of 9d have
been deposited with the Cambridge Crystallographic Data Centre as a supplementary
publication no. CCDC-710517. Copies of the data can be obtained free of charge on

1288
J. VOSS ET AL.
Table VI Crystal data and structure refinement for 9d
Empirical formula
Formula weight
Crystal system
Space group
a [pm]
C16H18S2
274.46
Triclinic
P¯i
976.8 (1)
b [pm]
1030.0 (1)
c [pm]
1546.1 (1)
95.78 (1)
98.25 (1)
α [◦]
β [◦]
γ [◦]
90.32 (1)
V [pm3]
Z
1531 • 106
4
ρcalcd. [g cm−3
]
1.19
29.29
584
2/65
µ [cm−1
F(000)
]
θ limits [◦]
h/k/l limits
0, +11/−12, +12/−18, +18
Reflections collected (I > 3σI)
Number of parameters
4069
398
R index
Rw index (w = σI
0.071
0.080
−2
)
application to CCDC, 12 Union Road, Cambridge CB2 IEZ, UK [Fax: (international) +
44-1223/336-033; E-mail: deposit@ccdc.cam.uk].
Thionesters
The respective ester (1.00 mol. equiv.) and 2,4-bis(4-methoxyphenyl)-1,3,2,4-
dithiadiphosphetane 1,3-disulfide (LR)15,18 (≈ 0.60 mol. equiv.) were heated to reflux for
6 h in about the 20-fold amount of chlorobenzene or (if stated) toluene. The progress of the
reaction was monitored by TLC. After completion of the reaction, the solvent was removed
by vacuum distillation in a rotary evaporator. The residue was purified by chromatography
with a suitable eluent and/or recrystallization. NMR spectroscopic, MS, and analytical
data of the thionesters are compiled in Tables VII–IX.
O-Ethyl naphthalene-1-carbothioate (1b)14–16 and O-ethyl naphthalene-2-
carbothioate (2b)15,17 are described in the literature.
O-Methyl Naphthalene-1-carbothioate (1a)
Methyl α-naphthoate3 (2.00 g, 10.50 mmol) was thionated with LR (2.50 g,
6.30 mmol). CC (CCl4) gave 1a (0.38 g, 18%) as an orange oil. IR: ν(C S) 1235 cm−1
.
O-Isopropyl Naphthalene-1-carbothioate (1c) and O-Isopropyl
Naphthalene-2-carbothioate (2c)
Isopropyl α-naphthoate3 (1.25 g, 5.80 mmol, containing isopropyl β-naphthoate as
a contamination) was thionated with LR (1.21 g, 2.99 mmol). CC (CCl4) gave 1c (F1,

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1289
Table VII Chemical shifts δ [ppm] and coupling constants J [Hz] in the 1H NMR spectraa of the thionesters
Compound
Proton chemical shifts δ and proton–proton coupling constants J
1a
1b
1c
1e
4.43 (s, 3 H, CH3), 7.45–7.60 (m, 3 H, 3/6/7-H), 7.85–7.95 (m, 3 H, 2/4/5-H), 8.25 (d, 3JH7,H8
8.6, 1 H, 8-H)
=
1.51 (t, 3J = 7.8, 3 H, CH3), 4.78 (q, 3J = 7.8, 2 H, CH2), 7.35–7.55 (m, 3 H, 3/6/7-H),
7.78–7.87 (m, 3 H, 2/4/5-H), 8.19 (d, 3JH7,H8 = 7.5, 1 H, 8-H)
1.55 (d, 3J = 6.1, 6 H, CH3), 6.00 (sep, 3J = 6.1, 1 H, CHMe2), 7.40–7.55 (m, 3 H, 3/6/7-H),
7.80–7.90 (m, 2 H, 4/5-H), 7.90 (d, 3JH2,H3 = 7.0, 1 H, 2-H), 8.19 (d, 3JH7,H8 = 8.1, 1 H, 8-H)
1.39 (s, 9 H, CH3), 1.43 (s, 9 H, CH3), 7.29 (d, 3JH2 ,H3 = 7.6, 2 H, 2ꢁ/6ꢁ-H), 7.36 (t, 3JH3 ,H4
=
ꢁ
ꢁ
ꢁ
ꢁ
3
7.2, 1 H, 4ꢁ-H), 7.53 (t, 3JH2 ,H3 ≈ JH3 ,H4 = 7.4, 2 H, 3ꢁ/5ꢁ-H), 7.60 (dd, 3JH5,H6 = 8.4,
ꢁ
ꢁ
ꢁ
ꢁ
4JH6,H8 = 1.8, 1 H, 6-H), 7.81 (d, 3JH5,H6 = 8.4, 1 H, 5-H), 7.90 (d, 4JH2,H4 = 1.6, 1 H, 4-H),
8.20 (d, 4JH6,H8 = 1.8, 1 H, 8-H), 8.54 (d, 4JH2,H4 = 1.6, 1 H, 2-H)
2a
2b
2c
4.35 (s, 3 H, CH3), 7.50–7.65 (m, 2 H, 6/7-H), 7.82 (d, 3JH5,H6 = 8.0, 1H, 5-H), 7.87
(d, 3JH7,H8 = 8.5, 1 H, 8-H), 7.96 (d, 3JH3,H4 = 8.3, 1 H, 4-H), 8.28 (dd, 3JH3,H4 = 8.3,
4JH1,H3 = 1.0, 1 H, 3-H), 8.71 (bs, 1 H, 1-H)
1.58 (t, 3J = 7.0, 3 H, CH3), 4.79 (q, 3J = 7.0, 2 H, CH2), 7.45–7.62 (m, 2 H, 6/7-H), 7.80 (d,
3JH5,H6 = 8.0, 1H, 5-H), 7.87 (d, 3JH7,H8 = 8.5, 1 H, 8-H), 7.95 (d, 3JH3,H4 = 7.2, 1 H, 4-H),
8.28 (d, 3JH3,H4 = 7.2, 1 H, 3-H), 8.70 (s, 1 H, 1-H)
1.45 (d, 3J = 6.1, 6 H, CH3), 5.85 (sep, 3J = 6.1, 1 H, CHMe2), 7.40–7.50 (m, 2 H, 6/7-H), 7.70
(d, 3JH5,H6 = 8.0, 1 H, 5-H), 7.85 (d, 3JH7,H8 = 8.5, 1 H, 8-H), 7.88 (d, 3JH3,H4 = 7.5, 1 H,
4-H), 8.18 (d, 3JH3,H4 = 7.5, 1 H, 3-H), 8.59 (bs, 1 H, 1-H)
3a
3b
4.32 (s, 3 H, CH3), 7.48 (m, 2 H, 6/7-H), 7.70 (s, 2 H, 2/3-H), 8.08 (m, 2 H, 5/8-H)
7.26–7.32 (m, 4 H, 3ꢁ/5ꢁ-H), 7.36–7.41 (m, 4 H, 2ꢁ/6ꢁ), 7.52–7.58 (m, 2 H, 4ꢁ-H), 7.63–7.68 (m, 2
H, 6/7-H), 8.05 (s, 2 H, 2/3-H), 8.54–8.59 (m, 2 H, 5/8-H)
4a
1.44 [d, 3J = 6.2, 6 H, 1-CH(CH3)2], 1.54 [d, 3J = 6.6, 6 H, 5-CH(CH3)2], 5.36 (sep, 3J = 6.1, 1
H, 1-CHMe2), 5.94 (sep, 3J = 6.3, 1 H, 5-CHMe2), 7.53 (dd, 3JH2,H3 = 7.2, 3JH3,H4 = 8.6, 1
H, 3-H), 7.56 (dd, 3JH6,H7 = 7.2, 3JH7,H8 = 8.6, 1 H, 7-H), 7.80 (dd, 3JH2,H3 = 7.2, 4JH5,H7
=
1.0, 1 H, 2-H), 8.12 (dd, 3JH2,H3 = 7.2, 4JH6,H8 = 1.0, 1 H, 6-H), 8.38 (d, 3JH7,H8 = 8.6, 1 H,
8-H), 8.98 (d, 3JH3,H4 = 8.6, 1 H, 4-H)
4bb
1.55 (d, 3J = 6.1, 12 H, CH3), 5.94 (sep, 3J = 6.1, 2 H, CHMe2), 7.48 (dd, 3JH2,H3 = 7.2,
3JH3,H4 = 8.6, 2 H, 3/7-H), 7.77 (dd, 3JH2,H3 = 7.2, 4JH2,H4 = 1.0, 2 H, 2/6-H), 8.25 (d,
3JH3,H4 = 8.6, 2 H, 4/8-H)
5b
6
4.10 (s, 6 H, CH3), 7.50 (vt, 3JH2,H3 ≈ JH3,H4 ≈ 8.6, 2 H, 3/6-H), 7.96 (d, 3JH3,H4 = 8.6, 2 H,
3
4/5-H), 8.19 (d, 3JH2,H3 = 7.6, 2 H, 2/7-H)
1.40 (t, 3J = 7.0, 6 H, CH3), 4.41 (q, 3J = 7.0, 4 H, CH2), 7.61 (m, 2 H, 6/7-H), 7.92 (m, 2 H,
5/8-H), 8.23 (s, 2 H, 1/4-H)
7a
3.98 (s, 3 H, COOCH3), 4.39 (s, 3 H, CSOCH3), 7.93 (d, 3JH7,H8 = 8.6, 1 H, 8-H), 7.99 (d,
3JH3,H4 = 8.4, 1 H, 4-H), 8.09 (dd, 3JH3,H4 = 8.8, 4JH1,H3 = 1.5, 1 H, 3-H), 8.31 (dd,
3JH7,H8 = 8.6, 4JH5,H7 = 1.6, 1 H, 7-H), 8.59 (bs, 1 H, 1-H), 8.72 (bs, 1 H, 5-H)
4.39 (s, 6 H, CH3), 7.95 (d, 3JH3,H4 = 8.6, 2 H, 4/8-H), 8.35 (dd, 3JH3,H4 = 8.6, 4JH1,H3 = 1.7, 2
H, 3/7-H), 8.75 (d, 4JH1,H3 = 1.7, 2 H, 1/5-H)
7b
7c
8a
1.54 (d, 3J = 12.0, 6 H, CH3), 5.93 (sep, 3J = 6.0, 2 H, CHMe2), 7.93 (d, 3JH3,H4 = 8.4, 2 H,
4/8-H), 8.28 (dd, 3JH3,H4 = 8.4, 4JH1,H3 = 1.7, 2 H, 3/7-H), 8.65 (d, 4JH1,H3 = 1.7, 2 H, 1/5-H)
1.43 [d, 3J = 6.0, 6 H, 6-CH(CH3)2], 1.55 [d, 3J = 6.0, 6 H, 2-CH(CH3)2], 5.32 (sep, 3J = 6.0, 1
H, 6-CHMe2), 5.93 (sep, 3J = 6.0, 1 H, 2-CHMe2), 7.82–7.88 (m, 2 H, 4/5-H), 8.14 (dd,
3JH3,H4 = 8.6, 4JH1,H3 = 1.6, 1 H, 3-H), 8.36 (dd, 3JH6,H7 = 8.6, 4JH6,H8 = 1.6, 1 H, 6-H),
8.70 (s, 1 H, 1-H), 8.76 (s, 1 H, 8-H)
8b
1.54 (d, 3J = 6.0, 12 H, CH3), 5.94 (sep, 3J = 6.0, 2 H, CHMe2), 7.81 (d, 3JH3,H4 = 9.2, 2 H,
4/5-H), 8.34 (dd, 3JH3,H4 = 9.2, 4JH1,H3 = 1.6, 2 H, 3/6-H), 8.78 (d, 4JH1,H3 = 1.6, 2 H, 1/8-H)
aCompounds 1b, 2, 3a, 6, 7a, 7b were measured at 250 MHz, all other thionoesters at 400 MHz.
bAssignments were corroborated by COSY measurements.

1290
J. VOSS ET AL.
Table VIII Chemical shifts δ [ppm] in the 13C NMR spectraa of the thionesters
b
C-1 C-2 C-3 C-4 C-4a C-5 C-6 C-7 C-8 C-8a α-CS β-CS OCHn OCCH3
1a 139.6 124.8 125.4 131.4 133.7 127.2 126.2 124.8 128.6 129.2 216.5
1c 139.9 124.3 124.7 130.5 133.2 127.5 126.5 125.6 127.9 128.6 214.8
1e 132.1 120.2 138.6 129.0 126.5 128.2 122.5 146.9 125.1 127.5 207.0
2a 128.2 135.0 125.0 129.0 135.0 129.1 127.2 126.2 129.4 132.0
2b 129.0 136.8 125.6 129.o 134.2 129.6 128.6 125.7 130.1 134.0
2c 127.5 136.0 125.3 128.0 135.2 129.3 126.4 127.4 129.6 132.2
3a 141.7 125.5 125.5 141.7 129.3 127.0 126.4 126.4 127.0 129.3 215.6
3b 141.2 125.3 125.3 141.2 129.4 127.1 126.8 126.8 127.1 129.4 213.5
4a 130.9 127.1 124.9 127.9 129.0 140.5 129.3 125.9 129.7 128.1 214.5
166.6e
59.5
76.0
20.8
c
211.6
211.0
210.3
58.9
59.1
61.1
13.9
21.2
59.5
d
76.1
68.3
76.5
58.9
61.7
52.1
21.6
20.8
21.2
4b 140.9 127.6 125.6 127.7 129.1 140.9 127.6 125.6 127.7 129.1 214.9
5
6
139.0 132.8 125.2 132.1 125.2 132.1 125.2 132.8 139.0 134.2 216.3
128.6 133.4 133.4 128.6 128.8 130.0 128.5 128.5 130.0 128.8
208.8
211.4
166.9e
211.4
209.0
209.8
14.2
7a 128.9 129.5 129.1 130.6 134.5 126.2 137.2 126.1 130.0 134.4
7b 128.8 137.1 126.2 129.1 134.3 128.8 137.1 126.2 129.1 134.3
7c 128.8 137.7 126.2 129.4 134.3 128.8 137.7 126.2 129.4 134.3
8a 131.6 129.0 127.8 130.3 136.7 127.9 127.4 137.2 127.6 132.6
59.5
76.0
75.9
21.3
22.0
21.3
21.4
165.8e 68.7
8b 130.0 137.1 127.3 130.9 136.8 130.9 127.3 137.1 130.0 131.4
209.1
75.9
aCompounds 1, 3a, 6, and 8 were measured at 63 MHz, all other dithioesters at 100 MHz.
bn = 3 for 1a, 2a, 3a, 5, 7a, 7b; n = 2 for 1b, 2b, 6; n = 1 for 1c, 2c, 4a, 4b, 7c, 8a, 8b.
c31.26 [C(CH3)3], 31.29 [C(CH3)3], 34.8 [C(CH3)3], 35.3 [C(CH3)3], 122.1 (C-2ꢁ/6ꢁ), 127.1 (C-4ꢁ), 129.8
(C-3ꢁ/5ꢁ), 149.4 (C-1ꢁ).
d121.5 (C-2ꢁ/6ꢁ), 126.4 (C-4ꢁ), 129.5 (C-3ꢁ/5ꢁ), 154.0 (C-1ꢁ).
eC O.
0.470 g, 35%); IR: ν(C S) 1231 cm−1, and 2c (F2, 0.140 g, 11%); IR: ν(C S) 1241 cm−1
,
as orange oils.
Phenyl 3,7-Di-tert-butylnaphthalene-1-carboxylate (1d)3,23
Commercially available 2,6-di-tert-butylnaphthalene, containing substantial amounts
of the isomer 3,7-di-tert-butylnaphthalene according to its 1H NMR spectrum, was purified
via its thiourea adduct.50 The colorless crystals (3.00 g, 12.50 mmol), mp 148–149◦C
(lit.50 146–147◦C), were dissolved in trimethyl phosphate (30 mL). Bromine (0.77 mL,
15.0 mmol) in trimethyl phosphate (10 mL) was added dropwise. After stirring at 70◦C for
6 h and cooling to 20◦C, the solution was extracted five times with PE. The extract was
washed with NaHSO4 solution and H2O, and dried over MgSO4. Removal of the PE and
CC (PE) gave 1-bromo-3,7-di-tert-butylnaphthalene (3.87 g, 97%) as white crystals, mp
1
50◦C (lit.51: 53–54◦C). H NMR (400 MHz): δ 1.38 (s, 9 H, CH3), 1.42 (s, 9 H, CH3),
7.58 (dd, 1 H, 6-H), 7.67 (d, 1 H, 2-H), 7.71 (d, 1 H, 5-H), 7.81 (d, 1 H, 4-H), 8.02 (d, 1
H, 8-H); 4JH2,H4 = 1.5, 3JH5,H6 = 8.6, 4JH6,H8 = 2.0. 13C NMR (100 MHz): δ 30.8 (CH3),
30.9 (CH3), 34.7 (CMe3), 35.0 (CMe3), 121.4 (C-6), 122.2 (C-4), 122.5 (C-1), 125.1 (C-8),
127.6 (C-2), 128.4 (C-5), 128.7 (C-4a), 133.0 (C-8a), 148.6 (C-7), 149.5 (C-3). MS (70
eV): m/z (%) = 320/318 (13/15) [M+], 305/303 (59/57) [M+ − CH3], 209 (9), 194 (7),
167 (9), 152 (6), 57 (100) [CMe3+]. The bromide (2.51 g, 7.80 mmol) was dissolved in

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1291
Table IX Chemical shifts δ [ppm] and coupling constants J [Hz] in the 1H NMR spectraa of the dithioesters
Compound
Proton chemical shifts δ and proton–proton coupling constants J
9d
1.43 (s, 9 H, CH3), 2.85 (s, 3 H, SCH3), 7.45 (m, 2 H, 6/7-H), 7.58 (d, 4JH2,H4 = 2.0, 1 H,
2-H), 7.80 (m, 2 H, 4/5-H), 8.11 (d, 3JH7,H8 = 8.0, 1 H, 8-H)
9db
7.46 (ddd, 3JH5,H6 = 8.0, 3JH6,H7 = 6.8, 4JH6,H8 = 1.8, 1 H, 6-H), 7.52 (ddd, 3JH7,H8 = 8.0,
3JH6,H7 = 6.8, 4JH5,H7 = 1.4, 1 H, 7-H), 7.63 (d, 4JH2,H4 = 2.0, 1 H, 2-H), 7.93 (ddd,
3JH5,H6 = 8.0, 4JH5,H7 = 1.4, 4JH4,H5 = 0.8, 1 H, 5-H), 7.96 (dd, 4JH2,H4 = 2.0, 5JH4,H8
0.7, 1 H, 4-H) 8.06 (dddd, 3JH7,H8 = 8.0, 4JH6,H8 = 1.8, 4JH4,H5 = 0.8, 5JH4,H8 = 0.8, 1 H,
8-H)
=
9e
1.45 (t, 3J = 7.5, 3 H, CH2CH3), 2.50 (s, 3 H, CH3), 3.42 (q, 3J = 7.5, 2 H, CH2CH3), 7.32
(s, 1 H, 2-H), 7.38–7.48 (m, 2 H, 6/7-H), 7.62 (s, 1 H, 4-H), 7.75 (d, 3JH5,H6 = 8.0, 1 H,
5-H), 8.09 (d, 3JH7,H8 = 8.0, 1 H, 8-H)
10b
11a
11b
11c
1.48 (t, 3J = 7.5, 3 H, CH3), 3.43 (q, 3J = 7.5, 2 H, CH2), 7.40–7.50 (m, 4 H, 4/5/6/7-H),
7.80–7.90 (m, 2 H, 3/8-H), 8.10–8.20 (m, 1 H, 1-H)
2.82 (s, 3 H, 3-CS2CH3), 2.85 (s, 3 H, 1-CS2CH3), 7.50–7.63 (m, 2 H, 6/7-H), 8.00 (d, 3JH5,H6
= 8.0, 1 H, 5-H), 8.12 (d, 3JH7,H8 = 8.0, 1 H, 8-H), 8.16 (s, 1 H, 4-H), 8.52 (s, 1 H, 2-H)
7.50–7.63 (m, 2 H, 6/7-H), 7.99 (d, 3JH5,H6 = 8.0, 1 H, 5-H), 8.12 (d, 3JH7,H8 = 8.0 1 H, 8-H),
8.16 (s, 1 H, 4-H), 8.53 (s, 1 H, 2-H)
4.38 (s, 2 H, SCH2Ph), 4.67 (s, 2 H, OCH2Ph), 7.31–7.46 (m, 10 H, HAr), 7.53–7.63 (m, 2 H,
6/7-H), 7.99 (d, 3JH5,H6 = 8.0, 1 H, 5-H), 8.12 (d, 3JH7,H8 = 8.0, 1 H, 8-H), 8.16 (s, 1 H,
4-H), 8.52 (s, 1 H, 2-H)
12a
12b
2.78 (s, 3 H, CH3), 7.31 (d, 3JH2,H3 = 9.0, 1 H, 3-H), 7.49–7.64 (m, 2 H, 6/7-H), 7.79 (d,
3JH5,H6 = 9.0, 1 H, 5-H), 8.12 (d, 3JH2,H3 = 9.0, 1 H, 2-H), 8.29 (d, 3JH7,H8 = 9.0, 1 H, 8-H)
1.47 (t, 3J = 7.5, 3 H, SCH2CH3,), 3.44 (q, 3J = 7.5, 2 H, SCH2CH3), 7.28 (d, 3JH2,H3 = 9.0,
1 H, 3-H), 7.50–7.63 (m, 2 H, 6/7-H), 7.77 (d, 3JH5,H6 = 9.0, 1 H, 5-H), 8.12 (d, 3JH2,H3
9.0, 1 H, 2-H), 8.29 (d, 3JH7,H8 = 9.0, 1 H, 8-H)
=
12c
13a
2.82 (s, 6 H, CH3), 7.43 (s, 2 H, 2/3-H), 7.48–7.53 (m, 2 H, 6/7-H), 8.08–8.14 (m, 2 H, 5/8-H)
2.82 (s, 6 H, CH3), 7.95 (d, 3JH3,H4 = 8.6, 2 H, 4/8-H), 8.35 (dd, 3JH3,H4 = 8.6, 4JH1,H3 = 1.7,
2 H, 3/7-H), 8.75 (d, 4JH1,H3 = 1.7, 2 H, 1/5-H)
13b
1.48 (t, 3J = 7.3, 6 H, CH3), 3.45 (q, 3J = 7.3, 4 H, CH2), 7.93 (d, 3JH3,H4 = 8.6, 2 H, 4/8-H),
8.13 (dd, 3JH3,H4 = 8.6, 4JH1,H3 = 1.3, 2H, 3/7-H), 8.50 (d, 4JH1,H3 = 1.3, 2 H, 1/5-H)
aMeasured at 250 MHz.
bAromatic protons, measured in acetone-d6 at 400 MHz.
dry diethyl ether (50 mL) under N2. A solution of nBuLi in hexane (5.2 mL, 15%) was
injected with a syringe through a septum, and the solution was stirred at 20◦C for 2 h.
Dry CO2 was bubbled through the solution for 30 min. The clear yellow reaction mixture
was cautiously hydrolyzed by stirring with ice/water (5 mL) and 4% aqu. HCl (8 mL)
for 10 h. The solution was extracted four times with diethyl ether. The extract was dried
over MgSO4. Removal of the solvent gave 3,7-di-tert-butylnaphthalene-1-carboxylic acid
(2.04 g, 90%) as white crystals, mp 186◦C. IR: ν(OH) 3442, ν(C O) 1688 cm−1. 1H NMR
(DMSO-d6, 400 MHz): δ 1.48 (s, 9 H, CH3), 1.51 (s, 9 H, CH3), 7.79 (dd, 1 H, 6-H), 8.05
4
(d, 1 H, 5-H), 8.14 (d, 1 H, 4-H), 8.31 (d, 1 H, 2-H), 8.90 (d, 1 H, 8-H); JH2,H4 = 2.0,
3JH5,H6 = 8.6, 4JH6,H8 = 2.0. 13C NMR (DMSO-d6, 100 MHz): δ 30.9 (CH3), 31.0 (CH3),
34.4 (CMe3), 34.8 (CMe3), 119.9 (C-6), 124.8 (C-2), 127.4 (C-8), 127.5 (C-1), 128.2 (C-5),
128.3 (C-4), 128.8 (C-8a), 131.8 (C-4a), 144.0 (C-3), 146.2 (C-7), 168.0 (C O). The acid
(0.55 g, 1.90 mmol) was mixed with PCl5 (0.52 g, 2.48 mmol) and heated to 140◦C for 3 h.
POCl3 was removed to yield 3,7-di-tert-butyl-1-naphthoyl chloride (1.00 g, 98%) as a deep
green oil. IR: ν(C O) 1757 cm−1. 1H NMR (400 MHz): δ 1.42 (s, 9 H, CH3), 1.45 (s, 9 H,
CH3), 7.65 (dd, 1 H, 6-H), 7.83 (d, 1 H, 5-H), 8.02 (d, 1 H, 4-H), 8.64 (s, 1 H, 2-H), 8.68 (d,

1292
J. VOSS ET AL.
1 H, 8-H); 4JH2,H4 = 2.0, 3JH5,H6 = 8.6, 4JH6,H8 = 2.0. The raw chloride was dissolved in
dry pyridine (4 mL), and phenol (0.23 g, 2.40 mmol) and DMAP (100 mg) were added.
The mixture was stirred at 0◦C for 5 h, then hydrolyzed with ice/water (5 mL) and conc.
aqu. HCl (5.3 mL), and extracted four times with diethyl ether. After drying over MgSO4
and removal of the solvent, the residue was recrystallized from PE to give 1d (0.30 g, 49%),
light yellow crystals, mp 160–161◦C. IR: ν (C O) 1730 cm−1 3,23
.
O-Phenyl 3,7-Di-tert-butylnaphthalene-1-carbothioate (1e)
The ester 1d (200 mg, 0.54 mmol) was thionated with LR (138 mg, 0.34 mmol)
to give 240 mg of a raw product. An aliquot of 100 mg was purified by preparative TLC
(PE/EtOAc 20:1) to yield 1e (7.3 mg, 8%) as a yellow solid besides the recovered 1d
(54 mg, 57%).
O-Methyl Naphthalene-2-carbothioate (2a)
Methyl β-naphthoate52 (1.53 g, 8.04 mmol) was thionated with LR (1.80 g,
4.46 mmol) in toluene (3 mL). Yield: 0.69 g (43%) after CC (CCl4), orange crystals,
mp 41–42◦C. IR: ν(C S) 1234 cm−1
.
O,O-Dimethyl Naphthalene-1,4-dicarbothioate (3a)
Dimethyl naphthalene-1,4-dicarboxylate3 (0.300 g, 1.23 mmol) was thionated with
LR (0.550 g, 1.36 mmol). Yield: 18 mg (6%) after CC (CCl4), orange needles. IR: ν(C S)
1229 cm−1
.
O,O-Diphenyl Naphthalene-1,4-dicarbothioate (3b)
Diphenyl naphthalene-1,4-dicarboxylate3 (0.720 g, 2.17 mmol) was thionated with
LR (1.36 g, 3.36 mmol). Yield: 0.104 g (14%) after CC (PE:EtOAc 30:1) and recrystal-
lization from toluene, yellow needles, mp 191–192◦C. IR: ν(C S) 1254 cm−1
.
Isopropyl 5-Isopropoxythiocarbonylnaphthalene-1-carboxylate (4a) and
O,O-Diisopropyl Naphthalene-1,5-dicarbothioate (4b)
Diisopropyl naphthalene-1,5-dicarboxylate3 (0.720 g, 2.40 mmol) was thionated with
LR (1.36 g, 3.36 mmol) in toluene (3 mL). CC (PE/EtOAc 30:1) gave two fractions. F1: 5
mg (0.6%) 4b, yellow powder, mp 178–180◦C; IR: ν(C S) 1263 cm−1; F2: 240 mg (32%)
4a, yellow powder, mp 68–69◦C. IR: ν(C O) 1712, ν(C S) 1252 cm−1
.
O,O-Diisopropyl Naphthalene-1,8-dicarbothioate (5)
Diisopropyl naphthalene-1,8-dicarboxylate3 (395 mg, 1.60mmol) was thionated with
LR (398 mg, 0.984 mmol) in toluene (2 mL) under N2. Yield: 67 mg (16%) after preparative
TLC (PE:EtOAc 20:1), yellow crystals, mp 195◦C; IR: ν(C S) 1239 cm−1
.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1293
O,O-Diethyl Naphthalene-2,3-dicarbothioate (6)
Diethyl naphthalene-2,3-dicarboxylate53 (150 mg, 0.551 mmol) was thionated with
LR (212 mg, 0.523 mmol) in toluene (0.6 mL) under N2. Yield: 78 mg (46%) after
preparative TLC (PE:EtOAc 10:1), orange-brown solid. IR: ν(C S) 1260 cm−1
.
Methyl 6-Methoxythiocarbonylnaphthalene-2-carboxylate (7a)
and O,O-Dimethyl Naphthalene-2,6-dicarbothioate (7b)
Dimethyl naphthalene-2,6-dicarboxylate3 (2.44 g, 10.0 mmol) was thionated with LR
(4.49 g, 11.1 mmol). CC (CCl4) gave two fractions. F1: 1.80 g (65%) 7b, orange crystals,
mp 193–194◦C (EtOAc); IR: ν(C S) 1238 cm−1; F2: 0.18 g (7%) 7a, citrine crystals, mp
122–123◦C. IR: ν(C O) 1724, ν(C S) 1265 cm−1
.
O,O-Diisopropyl Naphthalene-2,6-dicarbothioate (7c)
Diisopropyl naphthalene-2,6-dicarboxylate3 (0.500 g, 1.66 mmol) was thionated with
LR (807 mg, 2.00 mmol). Yield: 0.155 g (28%) after CC (CCl4/CHCl3 3:1), orange crystals,
mp 90–91◦C. IR: ν(C S) 1238 cm−1
.
Isopropyl 7-Isopropoxythiocarbonylnaphthalene-2-carboxylate (8a)
and O,O-Diisopropyl Naphthalene-2,7-dicarbothioate (8b)
Diisopropyl naphthalene-2,7-dicarboxylate3 (0.500 g, 1.66 mmol) was thionated with
LR (807 mg, 2.00 mmol). CC (CCl4/CHCl3 3:1) gave two fractions. F1: 0.210 g (40%) 8b,
orange oil; IR: ν(C S) 1235 cm−1. F2: 0.238 g (43%) 8a, orange crystals, mp 74–75◦C.
IR: ν(C O) 1713, ν(C S) 1219 cm−1
.
Dithioesters
Methyl naphthalene-1-carbodithioate (9a),24–26 ethyl naphthalene-1-carbodithioate
(9c),24,26,27 methyl naphthalene-2-carbodithioate (10a),28–30 ethyl naphthalene-2-
carbodithioate (10b),26,31 and dimethyl naphthalene-2,6-bis-carbodithioate (13a)32 are
described in the literature. NMR spectroscopic, MS, and analytical data of the dithioesters
are compiled in Tables IX–XI.
Trideuteromethyl Naphthalene-1-carbodithioate (9b)
The dithioester 9b was obtained via the Grignard route described in the literature25
for the preparation of 9a by use of CD3I instead of Me2SO4 as the alkylating agent. The
physical and spectroscopic data of 9b and 9a were identical.
Methyl 3-tert-Butylnaphthalene-1-carbodithioate (9d)
Acetyl chloride (14.1 g, 0.183 mol) was dropped into a stirred solution of AlCl3
(28.2 g, 0.210 mol) in 1,2-dichloroethane (74 mL) at 0◦C under exclusion of moisture. 2-
tert-Butylnaphthalene54 (32.1 g, 0.174 mol) was slowly added at <20◦C. After 12 h at 20◦C
and subsequent heating to 50◦C for 1 h, the reaction mixture was poured on ice, acidified to

1294
J. VOSS ET AL.
Table X Chemical shifts δ [ppm] in the 13C NMR spectra (100 MHz) of the dithioesters ArCS-SR
R
C-1
C-2
C-3
C-4
C-4a
C-5
C-6
C-7
C-8
C-8a α-CS β-CS
9c
9e
Eta
Etb
11a Mec
11b CD3
145.4 123.9 124.7 130.0 133.8 126.9 125.0 126.4 128.2 129.4 231.7
144.6 124.2 133.7 128.3 133.4 125.8 125.4 125.4 126.9 127.1 231.2
145.2 122.5 140.8 130.0 131.3 129.0 125.1 127.4 128.0 133.0 230.0 227.2
145.2 122.5 140.8 130.0 131.3 128.9 125.1 127.6 128.0 133.0 230.6 227.2
d
11c CH2Phe 145.2 121.2 137.3 129.9 131.8 129.0 125.2 127.4 127.9 133.0 229.3 225.0
12a Mef
12b Etg
12c Meh
13a Mei
145.1 127.4 128.9 124.8 132.2 127.8 125.6 124.5 127.6 130.6 230.8
145.1 127.4 128.9 124.7 132.1 127.7 125.6 123.9 127.6 130.5 230.2
146.6 122.8 122.8 146.6 129.8 127.2 125.3 125.3 127.2 129.8 231.4
126.1 143.6 125.6 127.2 130.4 126.1 143.6 125.6 127.2 130.4
229.4
a12.2 (SCH2CH3), 31.9 (SCH2CH3).
b11.6 (SCH2CH3), 20.9 (3-CH3), 31.2 (SCH2CH3).
c20.7 (3-SCH3), 21.0 (1-SCH3).
d20.7 (sep, 1JCD = 22.5, 3-SCD3), 21.0 (sep, 1JCD = 22.5, 1-SCD3).
e33.6 (CS-SCH2Ph), 42.6 (CO-SCH2Ph), CPh: 127.5, 128.7 (2 C), 128.9, 129.3, 129.6, 130.2, 133.0.
f21.1 (CH3).
g12.1 (SCH2CH3), 31.9 (SCH2CH3).
h21.0 (SCH3).
i20.8 (SCH3).
pH 1 with conc. HCl, and extracted with 1,2-dichloroethane. The organic phase was washed
subsequently with H2O, aqu. NaOH (2×) and H2O (→ pH 7), and dried over K2CO3.
Removal of the solvent and fractionating distillation gave 1-acetyl-3-tert-butylnaphthalene
(14), 19.9 g, 51%) as a colorless liquid, bp 126–133◦C. IR: ν(C O) 1747 cm−1. 1H NMR
(CDCl3, 400 MHz): δ 1.44 [s, 9 H, C(CH3)3], 2.75 (s, 3 H, SCH3), 7.47 (ddd, 1 H, 6-H),
7.53 (ddd, 1 H, 7-H), 7.82 (dd, 1 H, 5-H), 7.90 (d, 1 H, 4-H), 7.99 (d, 1 H, 2-H), 8.61 (dd, 1
H, 8-H). 4JH2,H4 = 1.7, 3JH5,H6 = 7.8, 4JH5,H7 = 1.7, 3JH6,H7 = 7.8, 3JH7,H8 = 8.6, 4JH6,H8
=
1.7. C8H18O (226.32), calcd. C 84.91, H 8.02; found C 85.02, H 7.80. This ketone (9.06 g,
40.0 mmol) and I2 (5.10 g, 20.1 mmol) were heated to 100◦C for 30 min in dry pyridine
(20 mL) and then left at 20◦C for 12 h. The mixture was filtered with suction, and the
solid was washed with cooled (−28◦C) MeOH and recrystallized from EtOH to yield N-[2-
(3-tert-butyl-1-naphthyl)-2-oxoethyl]pyridinium iodide (15, 6.93 g, 40%), mp 249–250◦C.
IR: ν(C O) 1747 cm−1. 1H NMR (DMSO-d6, 60 Mz): δ 1.57 [s, 9 H, C(CH3)3], 2.27 (d,
1 H, CH2), 2.52 (d, 1 H, CH2), 6.90 (s, 1 H, 4-H), 7.65–7.85 (m, 2 H, 6/7-H), 8.1–8.9
(m, 7 H, 2/5-H, PyH), 9.38 (d, 1 H, 8-H). 2JCH2 = 13, 3JH7,H8 = 6. C21H22ION (431.31),
calcd. C 58.48, H 5.14, I 29.42, N 3.25; found C 58.35, H 5.19, I 29.91, N 2.93. 15 (5.00
g, 11.6 mmol) was heated to reflux for 1 h in a solution of NaOH (3.00 g, 50 mL EtOH,
50 mL H2O). The solution was acidified to pH 1 with dil. HCl. Filtration gave 3-tert-butyl-
1-naphthoic acid (16, 2.40 g, 26%), mp 161–162◦C (EtOH). IR: ν(C O) 1747 cm−1. 1H
NMR (CDCl3, 400 MHz): δ 1.47 [s, 9 H C(CH3)3], 7.50–7.85 (m, 3 H, 5/6/7-H), 8.04 (d, 1
H, 4-H), 8.64 (d, 1 H, 2-H), 9.15 (d, 1 H, 8-H), 13.0 (bs, 1 H, OH). 4JH2,H4 = 2.0, 3JH7,H8
=
8.6. C15H16O2 (228.29), calcd. C 78.92, H 7.06; found C 79.10, H 7.04. 16 (1.60 g,
7.01 mmol) was heated to 80◦C in chlorobenzene (7 mL). 2,4-Bis(methylsulfanyl)-1,3,2,4-
dithiadiphosphetane 2,4-disulfide (“Davy’s reagent” (DR),35 1.10 g, 3.90 mmol) was added.
The solution was refluxed for 10 min and then heated to 80◦C for 90 min. The solvent was
removed. CC of the residue (1. PE, 2. hexane) and recrystallization from EtOH gave 9d
(0.88 g, 49%) as red crystals, mp 58–59◦C. IR: ν(C S) 1247 cm−1
.

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1295
Table XI Elemental analyses and mass spectra of thionesters and dithioesters
Elemental
formulae
Calcd.: C, H, S
Found: C, H, S
Mass spectra
m/z (% relative intensity) [assignment]
Compound
1a
C12H10OS (202.3)
71.25, 4.98, 15.85
70.89, 5.05, 16.09
202 (95) [M+], 187 (54) [M+ − CH3], 171 (68) [M+ − OCH3], 159
(100) [C10H7S+], 155 (25) [C10H7CO+], 127 (62) [C10H7+], 115
+
(48) [C9H7
]
1b
1c
C
13H12OS (216.3)
216 (55) [M+], 187 (54) [M+ − C2H5], 172 (19) [M+ − OC2H4],
72.19, 5.59, 14.82
72.60, 5.52, 13.74
171 (100) [M+ − OC2H5], 159 (43) [C10H7S+], 155 (46)
+
[C10H7CO+], 127 (83), [C10H7+], 115 (28) [C9H7
]
C
14H14OS (230.3)
230 (51) [M+], 188 (53) [M+ − C3H6], 187 (73) [M+ − C3H7], 171
73.01, 6.13, 13.92
72.76, 6.24, 13.95
(56) [M+ − OC3H7], 159 (10) [C10H7S+], 155 (100)
[C10H7CO+], 127 (88) [C10H7+], 115 (22) [C9H7+], 101 (7)
+
[C8H5+], 77 (15) [C6H5
]
2a
2b
2c
C
12H10OS (202.3)
202 (67) [M+], 171 (100) [M+ − OCH3], 155 (10) [C10H7CO+],
+
141 (23), 127 (62) [C10H7+], 115 (13) [C9H7
]
71.25, 4.98, 15.85
70.99, 4.88, 16.06
C13H12OS (216.3)
72.19, 5.59, 14.82
71.62, 5.52, 15.04
216 (52) [M+], 200 (10), 188 (6) [M+ − C2H4], 172 (39) [M+
−
OC2H4], 171 (100) [M+ − OC2H5], 155 (89) [C10H7CO+], 127
+
(84) [C10H7+], 115 (11) [C9H7
]
C
14H14OS (230.3)
230 (33) [M+], 197 (10), 188 (16) [M+ − C3H6], 187 (12) [M+
−
73.01, 6.13, 13.92
72.64, 6.53, 13.80
C3H7], 172 (32) [M+ − OC3H6], 171 (36) [M+ − OC3H7], 155
(100) [C10H7CO+], 127 (8+8) [C10H7+], 115 (10) [C9H7+], 101
(5) [C8H5+], 77 (8) [C6H5
]
3b
4a
C
24H26O2S2 (400.5)
307 (39) [M+ − OC6H5], 291 (30) [M+ − SC6H5], 214 (100)
71.97, 4.03, 16.01
71.35, 4.01, 16.66
C18H20O3S (316.4)
68.33, 6.37, 10.13
68.55, 6.51, 10.16
[M+ − 2 OC6H5], 198 (8), 170 (86) [C10H6CS+], 169 (20), 126
+ a
(20) [C10H6
]
316 (11) [M+], 257 (10) [M+ − OC3H7], 241 (22) [M+ –C3H6S],
231 (20), 215 (26) [C12H7O2S+], 199 (38) [C12H7OS+], 187
(100) [C11H7OS+], 171 (21) [C11H7S+], 154 (18) [C11H6O+],
126 (23) [C10H6+], 115 (31) [C9H7
]
+
5
C
14H12O2S2 (276.4)
276 (1) [M+], 245 (1) [M+ − OCH3], 212 (4) [M+ − S2], 201 (100)
[M+ − CSOCH3], 186 (46) [C11H10OS+], 158 (14) [C10H6S+],
154 (10) [C11H6O+], 126 (14) [M+ − 2 CSOCH3]
60.84, 4.38, 23.20
59.00b, 4.41, 22.66
C
64.60, 4.65, 12.32
64.66, 4.47, 12.34
C14H12O2S (276.4)
60.84, 4.38, 23.20
60.47, 4.32, 23.14
7a
7b
14H12O3S (260.3)
260 (88) [M+], 228 (100) [M+ − CH3OH], 199 (29) [C12H7OS+],
168 (29), 138 (14), 126 (22) [M+ − CO2CH3 − CSOCH3]
276 (100) [M+], 245 (60) [M+ − OCH3], 215 (30) [C12H7S2+], 171
(14) [C11H7S+], 170 (56) [C11H6S+], 169 (12), 158 (8)
[C10H6S+], 154 (6) [C11H6O+], 126 (17) [M+ − 2 CSOCH3],
107 (18)
7c
8a
8b
C
18H20O2S2 (332.5)
MS not recorded
65.02, 6.06, 19.29
64.80, 6.16, 18.76
C
68.33, 6.37, 10.13
68.10, 6.85, 10.01
C
18H20O3S (316.4)
MS not recorded
MS not recorded
18H20O2S2 (332.5)
65.02, 6.06, 19.29
65.22, 6.46, 18.45
9c
C
13H12S2 (232.4)
no analysis
16H18S2 (274.5)
232 (30) [M+], 203 (15) [M+ − C2H5], 171 (100) [M+ − SC2H5],
127 (27) [M+ − CS2C2H5]
9d
C
MS not recorded
70.02, 6.61, 23.37
70.24, 6.59, 23.24

1296
J. VOSS ET AL.
Table XI Elemental analyses and mass spectra of thionesters and dithioesters (Continued)
Elemental
Formulae
Calcd.: C, H, S
Found: C, H, S
Mass spectra
m/z (% relative intensity) [assignment]
Compound
9e
C14H14S2 (246.4)
68.24, 5.73, 26.03
68.35, 5.84, 25.81
246 (28) [M+], 217 (17) [M+ − C2H5], 185 (100) [M+ − SC2H5],
139 (12)
11a
11b
11c
12a
C
14H12S4 (308.5)
308 (55) [M+], 261 (100) [M+ − SMe], 214 (21) [M+ − 2 SMe],
170 (34) [M+ − SMe − CS2Me], 126 (21), [M+ − 2 CS2Me]
54.50, 3.92, 41.57
54.67, 4.01, 40.53
C14H6D6S4 (314.6)
53.46, 1.92c, 40.65
53.37, 1.81, 40.82
314 (56) [M+], 264 (100) [M+ − SCD3], 245 (14) [M+ − CD3 −
SCD3], 214 (21) [M+ − 2 SCD3], 170 (34) [M+ − SCD3 −
CS2CD3], 126 (21), [M+ − 2 CS2CD3]
C
26H20OS3 (444.64)
321 (45) [M+ − SCH2C6H5], 305 (5), 170 (23) [C10H6CS], 154
+
70.23, 4.53, 21.64
69.12, 4.53, 21.86
C12H9BrS2 (297.2)
48.49, 3.05,
21.58d48.65, 2.90,
21.57
(C10H6CO), 126 (18) [C10H6], 91 (100), [C7H7
]
298/296 (39/37) [M+], 251/249 (100) [M+ − SCH3], 170 (53)
[M+ − SCH3 − Br], 126 (71) [M+ − CS2CH3 − Br]
12b
12c
13a
13b
C
13H11BrS2 (311.3)
312/310 (35/33) [M+], 283/281 (12/11) [M+ − C2H5], 251/249
(100/95) [M+ − SC2H5], 170 (51), [M+ − SC2H5 − Br], 126
(56) [M+ − CS2C2H5 − Br]
50.16, 3.56, 20.60e
50.15, 3.47, 20.67
C
14H12S4 (308.5)
308 (38) [M+], 261 (32) [M+ − SMe], 245 (26), 214 (100) [M+ − 2
SMe], 170 (77) [M+ − SMe − CS2Me], 126 (34) [M+ − 2
CS2Me]
54.50, 3.92, 41.57
54.04, 3.85, 41.78
C
54.50, 3.92, 41.57
54.40, 4.02, 41.50
C
14H12S4 (308.5)
MS not recorded
16H16S4 (336.5)
MS not recorded
57.10; 4.79; 38.11
56.92; 5.13; 34.43b
aCI-MS: 401 (100) [M+ + 1], 307 (10) [M+ − OC6H5], 291 (9) [M+ − SC6H5], 214 (8) [M+ − 2 OC6H5].
bThe deviating analyses are due to impurities that could not be completely removed.
cD: Calcd. 3.83, found 3.61.
dBr: Calcd. 26.88, found 26.67.
eBr: Calcd. 25.67, found 25.62.
Ethyl 3-Methylnaphthalene-1-carbodithioate (9e)
Compound 9e was obtainedas describedfor 11a (seebelow) fromthe1-bromomethyl-
3-methylnaphthalene (0.091 g, 0.39 mmol), which was present as impurity (1H NMR spec-
trum) in 1,3-bis(bromomethyl)naphthalene (4.00 g, 12.7 mmol) and EtI (12.0 g, 76.0 mmol).
Yield: 0.065 g (68%), orange crystals, mp 56–57◦C. IR: ν(C S) 1237 cm−1
.
Dimethyl Naphthalene-1,3-bis-carbodithioate (11a)
1,3-Bis(bromomethyl)naphthalene55 (2.00 g, 6.37 mmol) and S8 (1.28 g, 40.0 mmol)
were added to a NaOMe solution (1.00 g Na in 20 mL dry MeOH). The reaction mixture
was heated to reflux for 4 h. The red-brown solution was cooled and mixed with ice (30 g).
MeI (4.30 g, 30.3 mmol) was added slowly with a pipette. After stirring at 20◦C for 1 h,

PREPARATION OF NEW NAPHTHALENECARBOTHIOATES
1297
H2O was added, and the solution was extracted with diethyl ether. The extract was dried
over Na2SO4, the solvent was removed, and the residue was purified by CC (PE:EtOAc 9:1)
and recrystallization (PE) to yield 11a (0.175 g, 9%) as a light red powder, mp 81–82◦C.
IR: ν(C S) 1232 cm−1
.
Bis-trideuteromethyl Naphthalene-1,3-bis-carbodithioate (11b)
Compound 11b was prepared and purified as described for 11a except by using CD3I
instead of MeI. Yield: 0.20 g (10%), mp 79–80◦C. IR: ν(C S) 1232 cm−1
.
O-Benzyl 1-Benzylthio-thiocarbonyl-naphthalene-3-carbothioate (11c)
Compound 11c was prepared and purified as described for 11a by use of PhCH2Br
instead of MeI. Yield: 0.10 g (3%), orange needles, mp 110–111◦C. IR: ν(C S) 1237,
ν(C O) 1657 cm−1
.
Methyl 4-Bromonaphthalene-1-carbodithioate (12a)
An etheral solution of nBuLi (18.3 mL, 29.0 mmol) was dropped into a solution
of 1,4-dibromonaphthalene56 (3.50 g, 12.2 mmol) in diethyl ether at −10◦C. A yellow
precipitate formed, and the suspension was stirred at 20◦C for 1 h. After cooling to −15◦C,
CS2 (4.0 g, 53 mmol) was dropped in. The brown colored reaction mixture was warmed
up to 20◦C within 3 h. Ice (35 g) and then MeI (5.0 g, 35 mmol) were added, and the
solution was rapidly stirred for 1 h. It was then diluted with H2O and extracted with diethyl
ether. The extract was dried over Na2SO4, and the solvent was removed. Purification by
CC (PE:EtOAc 9:1) and recrystallization from PE gave 12a (0.83 g, 22%), orange crystals,
mp 72◦C. IR: ν(C S) 1202 cm−1
.
Ethyl 4-Bromonaphthalene-1-carbodithioate (12b)
Compound 12b was prepared as described for 12a from 1,4-dibromonaphthalene56
(2.0 g, 7.0 mmol) by use of EtI (5.0 g, 28 mmol) instead of MeI. CC (PE:EtOAc 40:1) and
recrystallization from PE gave 12b (0.125 g, 6%), orange crystals, mp 42◦C. IR: ν(C S)
1200 cm−1
.
Dimethyl Naphthalene-1,4-bis-carbodithioate (12c)
Compound 12c was prepared and purified as described for 11a from 1,4-
bis(bromomethyl)naphthalene57 (1.10 g, 3.50 mmol), S8 (0.47 g, 15.0 mmol), NaOMe
(0.40 g, 17.0 mmol Na in 10 mL MeOH), and MeI (2.00 g, 14.1 mmol). Yield: 0.075 g
(7%), light red powder, mp 95◦C. IR: ν(C S) 1245 cm−1
.
Dimethyl Naphthalene-2,6-bis-carbodithioate (13a)
Compound 13a was prepared and purified as described for 11a from 2,6-
bis(bromomethyl)naphthalene58 (1.10 g, 3.50 mmol), S8 (0.47 g, 15.0 mmol), NaOMe
(0.40 g, 17.0 mmol Na in 10 mL MeOH), and MeI (2.00 g, 14.1 mmol). Yield: 0.375 g
(35%), red crystals, mp 188◦C (toluene). IR: ν(C S) 1238 cm−1
.

1298
J. VOSS ET AL.
Diethyl Naphthalene-2,6-bis-carbodithioate (13b)
Compound 13b was prepared and purified as described for 11a from 2,6-
bis(bromomethyl)naphthalene58 (3.14 g, 10.0 mmol), S8 (1.28 g, 40.0 mmol), NaOEt
(1.80 g, 78.0 mmol Na in 35 mL EtOH), and EtI (20.1 g, 128 mmol) instead of MeI. Yield:
0.80 g (24%), red crystals, mp 120–121◦C (toluene). IR: ν(C S) 1238 cm−1
.
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