1,3-Thiazoline-5-thiolates and 1,3-thiazole-5(2H)-thiones by [3+2]-cycloaddition of carbon bisulfide to metalated 4-alkylidene-4H-pyridin-1- ides

Article abstract of DOI:10.1002/ejoc.200500373

The 4-alkylidene-4H-pyridin-1-ides 1(-), which are ambident anions derived from azomethines 1a-e, react easily with CS₂ to yield the lithium 2,3-dihydro-1,3-thiazole-5-thiolates 3a-e. Two mechanisms are basically possible for this cyclization: a concerted process similar to a 1,3-dipolar cycloaddition or a two-step reaction which starts with a Cα CS₂ coupling and continues with a ring closure reaction to yield lithium thiazolidine-5-thiones 2. A proton migration from the Cα position to the previous imino N-atom then follows to form the 2,3-dihydro-1,3-thiazole-5- thiolates 3a-e. Protonation of 3 and a final oxidation of the intermediates 6 results in the formation of 1,3-thiazole-5(2H)-thiones 7. This last step is always accompanied by a hydrolysis which results in 1,3-thiazole-5(2H)-ones 8 as side products. In addition, a surprising byproduct 9 was found in the reaction of 1e with NaH and CS₂ in pyridine. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejoc.200500373

FULL PAPER
1
,3-Thiazoline-5-thiolates and 1,3-Thiazole-5(2H)-thiones by [3+2]-Cyclo-
[
‡]
addition of Carbon Disulfide to Metalated 4-Alkylidene-4H-pyridin-1-ides
[a]
[b]
[a]
Diana Hampe, Helmar Görls, and Ernst Anders*
Dedicated to Professor Dr. Roland Boese on the occasion of his 60th birthday
Keywords: Metalated azomethines / Carbon disulfide fixation / 1,3-Thiazole-5-thiolates / 1,3-Thiazole-5(2H)-thione / NMR
spectroscopy
The 4-alkylidene-4H-pyridin-1-ides 1(–), which are ambid-
ent anions derived from azomethines 1a–e, react easily with
CS to yield the lithium 2,3-dihydro-1,3-thiazole-5-thiolates
2
the 2,3-dihydro-1,3-thiazole-5-thiolates 3a–e. Protonation of
3 and a final oxidation of the intermediates 6 results in the
formation of 1,3-thiazole-5(2H)-thiones 7. This last step is al-
3
a–e. Two mechanisms are basically possible for this cycliza- ways accompanied by a hydrolysis which results in 1,3-thi-
tion: a concerted process similar to a 1,3-dipolar cycload- azole-5(2H)-ones 8 as side products. In addition, a surprising
dition or a two-step reaction which starts with a Cα CS coup- byproduct 9 was found in the reaction of 1e with NaH and
CS in pyridine.
2
ling and continues with a ring closure reaction to yield lith-
ium thiazolidine-5-thiones 2. A proton migration from the Cα
position to the previous imino N-atom then follows to form
2
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Introduction
Previous investigations on the azomethines 1 (which can
be prepared from 4-picolylamine and various ketones) have
opened a convenient synthetic approach to ambident carb-
anions which exhibit an interesting behavior towards elec-
trophiles, especially heterocumulenes (CO2, RNCO,
[
1]
RNCS). The benzylic methylene group in 1 is significantly
1
more acidic than the methyl group (R in 1a–c,e) and thus
can be deprotonated by various metallo-organyl com-
pounds or strong bases (Scheme 1). The formal allyl anion
which results is stabilized by charge delocalization into both
the pyridine ring and the C–N double bond. Quite a few
resonance structures can thus be formulated for these
anions 1(–) with three (Scheme 1) contributing significantly
to the resonance hybrid. As clearly supported by extensive
NMR investigations and DFT calculations,[ the most im-
1]
portant one of these can be expected to be the 4-alkylidene- Scheme 1. The ambident anions 1(–) are obtained by deprotonation
1
,4-dihydropyridine A which is followed by the 4-alkylid- of the azomethines 1 [derived from different ketones and 4-(ami-
1
nomethyl)pyridine].
ene-3,4-dihydropyridine B and the 2-azaallyl anion C. If R
2
and R are aryl substituents the conjugated system can be
extended even further.
According to a definition by Pearson and Kauffmann,[2]
‡] Metal 4-Iminomethyl-4H-pyridin-1-ides, 2. Part 1: Ref.[
1]
anions such as 1(–) can be interpreted as belonging to the
[
[
a] Institut für Organische Chemie und Makromolekulare Chemie class of semistabilized 2-azaallyl anions due to the elec-
der Friedrich-Schiller-Universität,
tronic influence of the heteroaromatic pyridine residue. Sta-
Humboldtstrasse 10, 07743 Jena, Germany
[
b] Institut für Anorganische und Analytische Chemie der Fried- bilized 2-azaallyl anions which bear strong electron-with-
rich-Schiller-Universität,
drawing substituents such as CN (nitriles), COOR (esters)
August-Bebel-Strasse 2, 07743 Jena, Germany
or O POR (phosphonates) can easily be obtained by depro-
Fax: +49-3641-948212
2
E-mail: Ernst.Anders@uni-jena.de
tonation of the corresponding azomethines. Nonstabilized
Eur. J. Org. Chem. 2005, 4589–4600
DOI: 10.1002/ejoc.200500373
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4589

D. Hampe, H. Görls, E. Anders
FULL PAPER
2-azaallyl anions possessing only alkyl residues and/or hy- thiazole-5-thiolate 3a–e (Scheme 2). In case of 1b, the mag-
drogen atoms are usually not obtained by deprotonating nesium bis(4-pyridin-4-yl-2,3-dihydro-1,3-thiazole-5-thiol-
azomethines but by tin/lithium exchange in (2-azaallyl)stan- ate) complex 4b was synthesized since the corresponding
[
2]
nanes. Synthetic applications of (2-azaallyll)ithium com- lithium compound 3b could only be prepared in an unre-
pounds include their addition to C=C, C=N, N=N, C=S, producible manner in a very poor yield.
and C=O double bonds as well as CϵC and CϵN triple
bonds. Cycloadducts are normally obtained except for
additions on C=O bonds.[ Intensive structural studies of
2]
these 2-azaallyl anions have been performed mainly on se-
–
–
mistabilized systems, e.g. [PhCHNCHPh] , [Ph CNCHPh] ,
2
–
[2b,3,12–14]
– [2b,4]
[
Ph CNCH ]
or [PhCHNCAlk ] .
However, a
2
2
2
–
few non-stabilized systems, such as [CH NCHAlk] , have
2
also been investigated.[
5]
At a first glance, the potential reaction partner, carbon
disulfide (CS ), seems to be a poor electrophile. DFT calcu-
2
lations on this cumulene indicate that the carbon atom car-
ries a small negative charge as compared to its oxygen ana- Scheme 2. The numbering of 3 does not follow the IUPAC rules,
logue CO in which the carbon atom is significantly posi- but should facilitate the NMR descriptions; in the case of 4b MgEt
2
2
[
6]
was used for deprotonation of 1b.
tively charged. The sulfur atoms are, however, easily po-
larizable which enables a significant charge redistribution in
Two possible mechanisms must be considered for this
cyclization (Scheme 3). A concerted cycloaddition with an
asynchronous transition state in which a lithium coordina-
tion mode is present that vaguely resembles a metal-assisted
a polar environment. CS can thus react as a C-electrophile
2
with suitable nucleophiles, e.g. amines, amides, alkoxides,
etc. It is quite often employed as a building block in the
synthesis of dithiocarboxylates, dithiocarbamates, (iso)thio-
ureas, amidines, guanidines, etc.[7] The dithiocarbamate
moiety generated from secondary N-methyl-amines can act
as a protecting (and directing) group for the amino function
in metalation and subsequent alkylations of the methyl
[
12]
azomethine ylide
which will be decisive in pathway a.
The other possibility (pathway b) is a two-step mechanism
in which CS first forms a single bond to the Cα atom to
2
give a dithiocarboxylate intermediate 5. Under the reaction
conditions employed (–65 °C to room temperature, THF),
we did not observe the intermediate formation of 5. After
the C–C bond formation, the now negatively charged sulfur
atom in the dithiocarboxylate 5 can be expected to attack
the positively polarized imino carbon atom in an intramol-
ecular manner. This ring closure releases the products, the
lithium 4-pyridin-4-yl-5-thioxo-1,3-thiazolidin-3-ides 2a–e.
[
8]
group. Moreover, carbon disulfide has been found to
function as a valuable dipolarophile in various 1,3-dipolar
[
9]
cycloadditions like other C=S-containing substrates.
Among other cycloadditions (hetero-Diels–Alder reactions,
2+2]-cycloadditions, chelotropic reactions) [3+2]-cycload-
[
ditions open various synthetic pathways for obtaining a
multitude of five-ring heterocycles.[ Due to the massive
potential applications of thiolate intermediates, quite a few
structural investigations of alkali metal and alkaline earth
metal thiolate complexes both in the solid state and in solu-
tion have been started in the 1980s and 1990s by several
10]
[
11]
research groups.
Continuing our systematic investigation on the reaction
behavior of 4H-pyridin-1-ide anions 1(–) towards various
[
1]
electrophiles, we now report on an unusual activation/fix-
ation reaction observed when CS reacts with lithium 4-
2
Scheme 3. Only 2e was isolated: Yield 46%. The numbering of 2
does not follow the IUPAC rules, but should facilitate the NMR
descriptions.
iminomethylene-4H-pyridin-1-ides Li1(–) which results in
cyclic lithium thiolates. We have investigated the solid-state
structure (X-ray analysis) of these products in order to gain
more insight into the coordination pattern of these ambid-
ent anions towards the metal cation.
While reaction a (Scheme 3) is clearly a 1,3-dipolar cyclo-
addition, the two-step process can regarded as 1,3-dipolar
cyclization, too. Huisgen and Sustmann et al. recently have
demonstrated the possibility to switch from concerted to
two-step processes via zwitterionic or biradical intermedi-
Results and Discussion
[
13a,13b]
ates. Further, both mechanisms can coexist.
step mechanisms are also discussed for several hetero-
Two-
Lithium 2,3-Dihydro-1,3-thiazole-5-thiolates 3
Addition of CS to the Cα atom of a lithium 4-alkylid- Diels–Alder reactions, which belong to the [ 4 + 2 ] type
2
π
s
π s
[
13c–13e]
ene-4H-pyridin-1-ide Li1(–) (Scheme 1) is accompanied by of reactions.
cyclization and a subsequent proton shift which result in
If one assumes the lithium 4H-pyridin-1-ides Li1(–) to
the formation of a lithium 4-pyridin-4-yl-2,3-dihydro-1,3- be examples of 2-azaallyl anions, the reaction can also be
4590
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 4589–4600

1,3-Thiazoline-5-thiolates and 1,3-Thiazole-5(2H)-thiones
FULL PAPER
Table 1. Conditions for the reaction of metalated azomethines 1a–e with CS
2
.
Starting
compound
R1
R2
Product
Base
T [°C]
T [°C] of
Time[a]
Yield
(%)
CS
2
addition
1
1
1
1
1
1
1
1
a
a
a
b
b
c
CH
CH
CH
CH
CH
CH
Ph
3
3
3
3
3
3
C
C
C
6
6
6
H
4
4
4
-p-Ph
3a
3a
nBuLi
–65
3 d
3 d
90
–
78
nBuLi
78
nBuLi
78
nBuLi
78
MgEt
20
nBuLi
78
nBuLi
78
nBuLi
78
H
H
-p-Ph
-p-Ph
–20
35
–
3a
room temp.
–20
3 d
51
–
α-naphthyl
α-naphthyl
tBu
3b
never[b]
12 h
1 h
10–30
34
–
4b
2
–20
–
3c
–20
71
–
d
e
Ph
3d
–20
3 d
84
–
CH
3
C
6
H
4
-p-OCH
3
2e, 3e
–20
2e: 1 h
3e: 2 d
46
–
[a] Time for precipitation formation of 3 and 4b, respectively. [b] Longer than 1–2 weeks.
1
2
interpreted as a 1,3-anionic cycloaddition which is defined the ring. Compounds 2d and 3d (R = R = Ph) are excep-
as a one- or multistep reaction of 1,3-anionophiles with tions in that only one asymmetric center is formed during
double or triple bonds. This reaction differs from 1,3-di- the reaction (Cα and N9, respectively). For the compounds
polar cycloadditions in that the positive charge has been 2e and 3b,c,e there are no indications in the NMR spectra
removed from the 1,3-dipole to obtain a negatively charged for the existence of diastereomers. Either only one dia-
4π-electron system (usually stabilized by the presence of a stereomer of 2e is formed (as a racemate) or both dia-
metal cation) which can react in a similar manner as a 1,3- stereomers have incidentally identical chemical shifts.
[
2b]
dipole to yield negatively charged five-membered rings.
Furthermore, the ring nitrogen atom N9 in the compounds
Some 1,3-anionic cycloadditions have been demonstrated to 3b,c,e can be expected to undergo a fast inversion in solu-
proceed by two-step mechanisms.[ Kauffmann et al. re- tion which leads to indistinguishable diastereomers. How-
14]
ported that 2 equiv. of (1,3-diphenyl-2-azaallyl)lithium ever, in the case of 3a, signal doubling for both the methyl
1
Li[PhCHNCHPh] react with CS in a double cycloaddition carbon atom (R ) and the quaternary carbon atoms of the
2
to yield a spiro compound (each C=S had cyclized with one five-membered ring are observed (see NMR Investigations
anion). Isolation of the monocylized product (corresponds as well as Experimetal Section).
to compound 2) was not successful.[ Support for the step-
15]
If the configuration of the lithium 4H-pyridin-1-ides
[
1]
wise addition mechanism is provided by the successful iso- Li1(–) can be predefined as being (E) the stereochemical
lation of the open-chain adduct when the oxygen analogue outcome of the cyclization could shed additional light on
[
1]
CO adds to either Li1(–) or (1,3-diphenyl-2-azaallyl)lith- the mechanism of addition. If the 1,3-anionic cycloaddition
ium.
2
[
16]
However, the subsequent cyclization and proton pathway (a; Scheme 3) is exclusively followed, only the cis
shift must be faster than the C–C bond formation when isomer of compounds 2 will be generated. On the other
CS is employed, since we could not detect the correspond- hand, pathway b generates the dithiocarboxylate 5 as an
2
ing open-chain adduct (the dithiocarboxylate 5) in this case. open-chain intermediate in which the subsequent attack of
1
2
We succeeded in isolating 2e (R = CH , R = C H -p- the negative sulfur atom can occur from both sides of the
3
6
4
OCH ) due to its poor solubility in THF as compared to C=N double bond resulting in the formation of all four
3
the other 5-thioxo-1,3-thiazolidin-3-ides 2a–d. Compound stereoisomers.
2
e precipitates spontaneously upon warming a solution to
room temperature. In addition, the lithium 4-pyridin-4-yl- either as an intramolecular 1,2-proton transfer or as an
,3-dihydro-thiazole-5-thiolates 3a–e can be crystallized if intermolecular acid-base reaction. Deprotonation of the re-
The mechanism of the proton migration can be discussed
2
the solution is allowed to stand for a longer period of time maining acidic Cα proton (which is expected to be more
at room temperature (Table 1). These are the products of a acidic than the corresponding protons in the starting mate-
proton transfer from Cα to the thiazolidine nitrogen atom rials 1) can be affected by the amide nitrogen atom (base)
N9 and can be considered to be amino-thioenolates of another anion of 2. Conjugation of the Cα–C7 double
(Scheme 2).
bond with the aromatic pyridine ring and the delocalization
In the course of this reaction, various new asymmetric of the negative charge over this extended conjugated π-sys-
centers are formed (Cα/C8 in 2a–c,e and C8/N9 in 3a–c,e: tem is assumed to be the driving force for this process. We
R ϶ R ). A total of four stereoisomers are conceivable – monitored this proton migration by 1H NMR measure-
1
2
namely two pairs of diastereomeric enantiomers. The dia- ments (Table 2) for the conversion of 2e into 3e. Shortly
stereomers are cis/trans isomers regarding the spatial ar- after dissolving 2e in [D ]DMSO, only the signals of 2e are
6
rangement of the substituents on the asymmetric atoms of detectable. After 2 d at room temperature, the proton trans-
Eur. J. Org. Chem. 2005, 4589–4600
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4591

D. Hampe, H. Görls, E. Anders
FULL PAPER
fer has proceeded to ca. 60% and in 3–4 d the transfer is molecules (THF). Interestingly enough, one of the anions
complete.
coordinates to the lithium ion via the negatively charged
sulfur end [Li1–S1 2.451(5) Å], the other via the pyridine
nitrogen atom [Li1–N1A 2.069(5) Å]. This arrangement al-
lows the formation of molecular chains since each thiazole-
5-thiolate anion complexes with two different lithium cat-
ions. This results in a distorted N,O,O,S tetrahedron about
the lithium ion with the following bond angles: N1A–Li1–
S1 122.1(2)°, O1–Li1–S1 118.4(2)° (these are widened pre-
sumably due to the spatial demand of the bulky thiazole-5-
thiolate ring), S1–Li1–O2 105.1(2)°, N1A–Li1–O2
Table 2. 1H and 13C NMR spectroscopic data of the lithium 4-
pyridin-4-yl-2,3-dihydro-thiazole-5-thiolates 3a–e and the lithium
4
-pyridin-4-yl-5-thioxo-1,3-thiazolidin-3-ide 2e ([D
6
]DMSO, room
[
a]
temp., 250/62.5 MHz).
3
c
2
e
b[c]
a
d
e
δ
H
H2/6
H3/5
NH9
8.19
8.53
4.68
8.23
8.65
4.80
8.15
8.41
3.79
8.19
8.60
4.66
8.15
8.53
4.55
8.41
7.80
Hα:
105.4(2)°, O1–Li1–N2 102.6(2)°, and O1–Li1–O2 100.6(2)°.
6.04
The latter four angles are somewhat compressed. Structural
analyses of Li–S bonds in numerous thiolates have yielded
a value of 2.6 Å as being an upper limit for a strong Li–S
CH
3
1.85
2.13
1.50
–
1.77
2.23
δ
C
[
17]
interaction.
(PhCH S)Li(NC H )]
C2/6
C3/5
C4
148.0
117.4
143.0
123.1
156.4
74.0
148.0
117.3
143.1
121.7
157.0
73.6
147.7
117.2
142.2
123.7
151.5
79.0
148.0
117.3
143.0
122.8
155.8
80.9
–
148.0
117.3
143.1
123.2
156.5
74.0
148.2
122.9
153.1
85.9
[
and [PhSLi(NC H ) ]
5 2 ϱ
also
2
5
5
ϱ
5
build infinite polymers in the solid state. In these related
compounds, the monomeric units of the infinite chains are
linked together by symmetrical or asymmetrical coordina-
tion of three or two lithium ions with one ligating sulfur
Cα
[
[
b]
b]
C7
C8
163.4
[d]
(33.6)
16.5
CH
3
29.8
30.4
25.8
30.4
[
18,19]
atom.
In contrast to this, the bridging in [3a(THF)2]ϱ
[
[
a] The numbering of 3a–e and 2e follows that in Schemes 2 and 3.
b] The carbon atom C7 of compounds 3 is the newly introduced
is accomplished by two different ligating atoms (S and N)
CS
carbon atom (C7) in the starting materials 1. [c] 4b: H2/6: 8.21; linker. The Li–S and Li–N(pyridine) distances in the ben-
H3/5: 8.60; NH9: 4.77; CH : 2.09; C2/6: 148.0; C3/5: 117.2; C4:
43.1; Cα: 121.7; C7: 157.0; C8: 73.6; CH : 30.4. [d] An unambigu-
2
carbon atom, C8 of compounds 3 corresponds to the imino in one 4-pyridin-4-yl-2,3-dihydro-1,3-thiazole-5-thiolate
3
zylthiolate mentioned above are in the range of 2.470–
.508 Å and 2.045–2.068 Å, respectively. In [3a(THF) ] the
1
3
2
2
ϱ
ous assignment of this signal was not possible, even not by 2D
NMR spectroscopy (see text).
Li1–S1 distance is with 2.451 Å somewhat shorter, but the
Li1–N1A distance is similar (2.069 Å).
In case of 3a, crystals suitable for X-ray analysis were
When 2-benzylpyridine was lithiated and then treated
obtained. Figure 1 depicts the molecular structure of 3a as with CS in the presence of TMEDA, a monomeric lithium
2
being a polymer [3a(THF) ] . The lithium cation is coordi- dithiocarboxylate could be isolated and structurally charac-
2
ϱ
[
20]
nated to two thiazole-5-thiolate anions and two solvent terized by single-crystal X-ray analysis.
The lithium ion
2 ϱ
Figure 1. Molecular structure of [3a(THF) ] with selected bond lengths [Å] (hydrogen atoms of the solvent molecules are omitted for
clarity).
4592
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 4589–4600

1,3-Thiazoline-5-thiolates and 1,3-Thiazole-5(2H)-thiones
FULL PAPER
is coordinated by one sulfur atom (2.438 Å), the pyridine porphyrin ring.[21] Furthermore, systematical investigations
nitrogen atom (2.057 Å) and the two nitrogen atoms in of complexes containing Mg–S and Mg–N interactions are
[
20]
TMEDA.
[
This structure compares quite well with beginning to shed light onto the characteristics of those
[
22]
3a(THF)] . The same reaction (lithiation, CS , TMEDA) bonds.
2
2
on one methyl group of 2,3-dimethylpyrazine leads to a mo-
Unfortunately, we have not yet succeeded in isolating the
nomeric lithium dithiocarboxylate complex in which both bright orange magnesium thiolate 4b in crystalline form
sulfur atoms are coordinated to the metal ion (2.554/ (prepared by deprotonation of 1b with MgEt and the sub-
2
2
.688 Å). These monomers are connected to a polymer sequent reaction with CS ). In the solid state 4b is an
2
chain by coordination of one pyrazine nitrogen atom to the orange powder that is extremely moisture-sensitive (sudden
lithium ion of another monomer moiety (Li···N 2.129 Å). color change to purple). Even under argon it slowly decom-
The C–S bonds in both lithium dithiocarboxylates are al- poses to unidentified products accompanied by a strong
most of the same length (1.687/1.673 Å and 1.687/ smell of H S and/or other sulfides. Presumably, the magne-
2
[
20]
1.675 Å).
sium ion binds to the 4-pyridin-4-yl-1,3-thiazole-5-thiolate
In [3a(THF)2]ϱ the S1–C7 and S2–C7 bonds (1.726 Å, in a similar manner as the lithium ion; e.g. tetrahedral coor-
.776 Å) are very similar but longer as compared to the dination by the thiolate sulfur atom of one anion, the pyri-
1
dithiocarboxylates and thus resemble a ketene dithioacetal dine nitrogen atom of a second anion and two solvent mole-
[
20]
structure. The S2–C8 bond in [3a(THF) ] with 1.872 Å cules (THF) or octahedral coordination by four thiolate
2
ϱ
can be defined as a typical C–S single bond. The S1–C7 anions (two via the sulfur atom and two via the pyridine N
and S2–C7 bond lengths in [3a(THF)2]ϱ range between a atom) and two THF molecules, respectively. The signals of
1
C–S double (1.67 Å) and a C–S single bond. The S1–S2– these solvent molecules are clearly discernible in the H
C7–Cα–N9 moiety is almost coplanar with the pyridine NMR spectrum, even after carefully drying the sample in
ring inclosing an angle of 1.8°. The aromatic ring thus vacuo. We conclude that THF molecules must be strongly
clearly contributes to the stabilization of the negative charge bound to the magnesium ion.
on the sulfur atom by forming an extended conjugated π-
3
system (as mentioned above). The sp carbon atom C8 is
turned out of the S1–S2–C7–Cα–N9 plane by 27.3°. The
biphenyl substituent stands almost perpendicular (89.2°) to
NMR Investigations
the thiazole ring. Both phenyl rings are distorted against
each other by 36.2°.
Compounds 3c and 3d (Table 1) have been subjected to
extensive NMR investigations ( H, C, DEPT135, HMBC,
1
13
Crystals of 3b were unfortunately not stable enough to HMQC) and the resulting spectra compared to those ob-
extract more than their structural motif from X-ray analysis tained for 3a and 3b (known solid-state structures). All re-
(Figure 2). However, this, together with 2D NMR experi- sults are self-consistent (Table 2) and one can assume that
ments clearly demonstrates its membership to the same all four of these compounds have similar solution struc-
class of compounds as 3a.
tures.
A comparison of the lithium thiolates 3a–e shows that
only small substituent effects on the chemical shifts of the
pyridine and thiazole ring are present (Table 2). The NMR
+
signals of the thiolate anions in 3b (M = Li ] and 4b (M
2+
=
Mg ) are not significantly influenced by the coordinat-
ing metal ion (see footnote [c] of Table 2).
1
2
Due to the two aliphatic groups at C8 (R = CH , R =
3
tBu), the signal of proton H9 in 3c is noticeably shifted
upfield. The small downfield shift of the signals of the
1
2
methyl group and the proton H9 in 3b (R = CH , R = α-
3
naphthyl) as compared to 3a,c,e is presumably the result of
the electronic influence of the aromatic residue (α-naphthyl,
ring current effect).
1
A comparison of the tautomers 2e and 3e (R = CH ,
3
2
R = C H -p-OCH ) reveals significant differences in their
6
4
3
1
13
chemical shifts in both H and C NMR spectra. The sig-
2 ϱ
Figure 2. Structure motif of [3b(THF) ] (hydrogen atoms are omit-
ted).
nals of protons H2/6 in 2e are shifted downfield by
0.26 ppm whereas those of protons H3/5 are shifted upfield
Complexes containing Mg–S interactions could possibly by 0.73 ppm. The difference of 1.39 ppm between the shifts
be of significant future interest due to the recent elucidation of the signals of Hα in 2e and H9 in 3e indicates a higher
of the solid-state structure of Photosystem I (2.5 Å resolu- acidity for Hα than for NH. In addition, the methyl protons
tion). In this natural system, the magnesium ion is surpris- are affected by the charge redistribution. In 2e, the methyl
ingly coordinated to the sulfur atom of a methionine group group is deshielded (signal shifted by +0.46 ppm as com-
in addition to the four nitrogen atoms of the chlorophyll pared to 3e. The signals of the carbon atoms also exhibit
Eur. J. Org. Chem. 2005, 4589–4600
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4593

D. Hampe, H. Görls, E. Anders
FULL PAPER
significant differences in their chemical shifts with the ex- carbon atom C8 and the nitrogen atom N9. Thus, the for-
ception of C2/6 (see Table 2). The signal location of Cα in mation of cis/trans isomers (diastereomers) is conceivable.
both 2e (δ = 85.9 ppm) and 3e (δ = 123.2 ppm) reflects its Usually, a pyramidal nitrogen atom inverts easily in solu-
3
2
respective hybridization (sp vs. sp ).
tion. However, the configuration on N9 is frozen in the so-
The signal location of the quaternary atom C8 in 2e can- lid-state structure of 3a (Figure 1) and the proton H9 is
not unambiguously be assigned, even when 2D NMR tech- located trans to the biphenyl residue. The 13C NMR spec-
1
13
niques are employed. An HMBC ( H, C-coupling) experi- trum of 3a shows two signals for the methyl carbon atom
ment shows a crosspeak between the Hα signal and a (not C10 and all quaternary carbon atoms (C4, Cα, C7, and C8)
1
3
visible) C signal at δ = 33.6 ppm. However, crosspeaks with very small (0.04–0.15 ppm) shift differences. This split-
1
3
between this invisible C signal and the signals of either ting can be explained either by the existence of cis/trans
the CH3 protons or the ortho-protons of the 4-meth- diastereomers (relative to the dihydrothiazole ring) or by a
oxyphenyl group are not discernible. Due to the neighbor- kind of axial chirality regarding the slightly restricted rota-
hood of the negatively charged nitrogen atom N9, C8 in 2e tion of the biphenyl ring along the C8–C11 bond. This sig-
is probably strongly shielded and its signal therefore shifted nal doubling was not observed for the other three com-
upfield to δ = 33.6 ppm. Another probable consequence of pounds 3b,c,e.
the negative charge at N9 is the upfield shift by 10–15 ppm
observed for the signal of the methyl carbon atom in 2e
1
Protonation and Subsequent Oxidation of the Lithium 4-
Pyridin-4-yl-2,3-dihydro-1,3-thiazole-5-thiolates 3a–e
(
R = CH ) as compared to that of the methyl groups in
3
compounds 3.
A comparison of the NMR spectroscopic data for the
Treating of the lithium salts 3 with water leads to inter-
esting 4-pyridin-4-yl-1,3-thiazole-5(2H)-thiones 7 (Scheme 4
and Figure 3). The course of this protonation/oxidation re-
action presumably includes the initial generation of 4-pyri-
din-4-yl-1,3-thiazolidine-5-thiones 6 which are then rapidly
oxidized (by air oxygen) at the CαH–NH bond (Scheme 4).
The yellow salts 3 dissolve in water to form bright orange
to deep red solutions. These change color and become gray-
green (3a–c) or blue (3d) upon extraction with ethyl acetate
starting compounds 1a–e (Table 3) and the lithium salts 3a–
1
e shows clear distinctions mainly in the H NMR spectra.
The NMR spectra of the azomethines 1a–e were recorded
in CDCl , but comparable results were obtained in [D ]-
3
6
DMSO. Since some measurements for 1b had to be carried
out at 0 °C, the use of [D ]DMSO was excluded. The pro-
6
tons H3/5 in 3 are strongly deshielded and their signals thus
shifted downfield by 1.06–1.52 ppm. The signals of protons
H2/6 in 3 are shifted in the opposite direction (upfield) but
not to the same extent as those of H3/5 – the chemical shift
differences range between 0.24 and 0.41 ppm. Their relative
position to each other is thus reversed in comparison to the
imines 1.
(intensive stirring in a beaker). The formation of an ex-
tended π-system in 7 over the atoms N9, Cα, C7, and the
exocyclic sulfur atom which, in addition, is cross-conju-
gated with the aromatic pyridine ring is assumed to be de-
cisive for this oxidation.
Table 3. 1H and 13C NMR spectroscopic data of the 4-imi-
nomethyl-pyridines 1a–e (CDCl
3
; 1a–e: 250/62.5 MHz, room temp.;
[
a]
1b: 0 °C, 400 MHz).
1
c
a
(Z)-b[b] (E)-b[b]
d
e
δ
H
H2/6
H3/5
Hα
8.57
8.47
7.13
4.19
2.49
8.57
7.41
4.79
2.43
8.53
7.33
4.43
1.86
8.52
7.28
4.56
–
8.59
7.43
4.69
2.32
[
c]
4.70
2.35
CH
3
δ
C
Scheme 4. The numbering of 2 does not follow the IUPAC rules,
but should facilitate the NMR descriptions in the Experimental
Section.
C2/6
C3/5
C4
Cα
C7
CH
149.8
122.8
149.7
54.4
166.6
16.0
149.7
122.9
149.1
55.2
171.6
29.8
149.9
123.0
149.2
54.9
170.8
21.1
149.6
122.5
150.3
53.2
177.6
13.8
149.7
122.7
149.7
56.1
170.2
–
149.9
122.8
150.0
54.2
166.2
15.7
An X-ray analysis of 7d confirms the formation of these
thiones (Figure 3). Both sulfur atoms S1/S2, the carbon
atoms C7, Cα, and the nitrogen atom N9 span a plane
which intersects at an angle of 41.1° with the pyridine ring.
[
d]
3
[
a] The numbering of compounds 1 follows that in Scheme 1. [b]
Two signal sets emerge for the (E)/(Z) mixture. [c] The signal of Cross-conjugational effects between these two π-systems are
H3/5 overlaps with the signals of the meta- and para-protons of the
thus reduced. Spatial hindrance could be one reason for this
4
-phenyl substituent to a multiplet at δ = 7.34–7.47 ppm. [d] The
imino carbon atom C7 in compounds 1 corresponds to the carbon
atom C8 in the lithium salts 2 and 3.
somewhat larger dihedral angle than that observed in the
solid-state structure of the anion 3a. The Cα–N9 (1.284 Å)
and the C7–S1 (1.596 Å) double bonds are significantly
As mentioned above, the 2,3-dihydrothiazole rings in 3 shorter than in 3a (Cα–N9 1.451 Å, C7–S1 1.726 Å). The
possess two chiral centers (with the exception of 3d): the system is thus more crowded and the protons H3/5 experi-
4594
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1,3-Thiazoline-5-thiolates and 1,3-Thiazole-5(2H)-thiones
FULL PAPER
Whereas 1,3-thiazole-5(4H)-ones are well-known hetero-
[
25]
cycles,
(2H)-ones. Barrett et al. have synthesized an example of
there are only very few examples of 1,3-thiazole-
5
such a 1,3-thiazole-5(2H)-one by a Michael addition of ac-
rylonitrile to the active methine group of 2,4-diphenyl-1,3-
[
26a]
thiazole-5(4H)-one.
In addition, Roesky et al. have
studied the 1,3-dipolar cycloaddition of COS to amino-sub-
stituted nitrile ylides generated from N-(chloromethyl)form-
[
26b]
amidines.
The interesting question of an 1,3-thiazole-5-thione/thiol
equilibrium suggests the use of aldimines in the reaction
sequence of deprotonation, cyclization with CS , proton-
2
1
2
ation and oxidation (cf. Scheme 4, R or R = H). However,
aldimines derived from aldehydes and 4-(aminomethyl)pyri-
dine (Scheme 1) unfortunately cannot be isolated (hydroly-
[
1,27]
sis or polymerization occurs).
An in situ generation un-
Figure 3. Molecular structure of 7d with selected bond lengths [Å]
and angles [°]: Cα–N9 1.284, Cα–C7 1.502, C7–S1 1.596, C7–S2
der mild conditions and instantaneous reaction could poss-
1
ibly result in the corresponding substance class of 7 (R or
1
.723, C8–S2 1.872, C8–N9 1.464, Cα–C4 1.488; S1–C2–S2 124.6,
N9–Cα–C7 117.6, N9–C8–S2 106.6, C7–S2–C8 92.5.
2
R = H). Studies in this direction are in progress.
ence stronger steric interactions with the sulfur atom. As-
tonishingly, the quaternary sp carbon atom C8 is only neg-
3
Sodium 2-(4-Methoxyphenyl)-2-methyl-4-(pyridin-4-yl)-2,5-
dihydrothiazole-5-trithiocarbonate 9
ligibly turned out of the dihydrothiazole plane (by 0.8°).
The phenyl rings are perpendicular both to each other and
to the thiazole ring so that the least possible steric interac-
tion exists among the aryl residues and the five-membered
ring.
Surprisingly, sodium 4-(pyridin-4-yl)-2,5-dihydrothi-
azole-5-trithiocarbonate 9 was found to be a byproduct in
the reaction of 1e with NaH and CS2 in pyridine
(Scheme 6). We assume that compound 9 is generated as a
The protonation/oxidation procedure that generates the
result of a hydrogen migration in Na2e or Na3e followed
5
(2H)-thiones 7 is always accompanied by a side reaction:
a desulfurization with formation of the 5(2H)-ones 8
Scheme 5). Compounds 8 result from hydrolysis of 7 dur-
by the attachment of a second molecule of CS (Scheme 6).
2
The reaction mixture contains at least four products; we
succeeded in isolating a small amount of 9 (approximately
(
ing the workup and, in addition, from slow degradation by
air moisture. Samples of 7 that had been stored a while
10% total yield) as a crystalline material suitable for X-
ray analysis (Figure 4). We assume the other products to
be diastereomeric forms of Na3e as well as structure III in
Scheme 7 since the 13C NMR spectrum of this product mix-
develop the strong typical smell of H S.
2
ture shows characteristic signals in the range of δ = 70–
3
9
0 ppm, which are typical for sp carbon atoms bound to
two geminal heteroatoms.
Scheme 5. Hydrolyses of 7b,d,e to the thiazole-5(2H)-ones 8b,d,e.
To the best of our knowledge, only one example for a
1
,3-thiazole-5(2H)-thione has been described in the litera-
[23]
ture by Huisgen et al. They reported the formation of 2-
4-nitrophenyl)-4-phenyl-1,3-thiazole-5(2H)-thione gener-
(
ated by the reaction of N-(4-nitrobenzyl)benzimidoyl chlo-
ride with triethylamine and carbon disulfide via a nitrile
[
23]
ylide.
A similar substance class – the 1,3-thiazole-5(4H)-
[
24]
thiones – has been synthesized by Heimgartner et al., in
which the C–N and C–S double bonds are opposite to each
other in the thiazole ring as compared to our 5(2H)-thiones
7
in which the two double bonds are conjugated. These
Scheme 6. Two possible reaction pathways a and b for the forma-
tion of compound 9.
5(4H)-thiones are obtained by an intramolecular cyclization
of a dithio-dipeptide with loss of the terminal amide residue
as an amine. The thiocarbonyl moiety is a suitable di-
Unfortunately, the structure of 9 was determined only as
polarophile and undergoes a cycloaddition reaction with a structure motif (Figure 4). The trithiocarbonate 9 is an
+
–
azomethine ylides to form spiro-attached dithiazolines.
ionic complex: {[Na(py) ] [Na (tritihiocarbonate) ] } (py
6 3 4
ϱ
Eur. J. Org. Chem. 2005, 4589–4600
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4595

D. Hampe, H. Görls, E. Anders
FULL PAPER
–
3 4 ϱ
Figure 4. Structure motif of the complex anion {[Na (trithiocarbonate) ] } of 9.
monomeric and a dimeric complex anion are present which
show, in contrast to 9, only a fivefold coordination in a
distorted square pyramid. The pyridine-2-thiolate anion
acts as bidentate chelate ligand similar to the trithiocarbon-
ate moiety in the complex anion of 9. In the case of the
dimeric complex anion, the sulfur atom bridges to a second
sodium ion. The positive counterion is built by a sodium
[
17]
ion coordinated with two crown ether molecules.
In Scheme 7, we propose a mechanism for the proton
shift that generates 9. This reaction is quite likely an inter-
molecular process. The proton H9 could be abstracted from
sodium 2,3-dihydro-1,3-thiazole-5-thiolate Na3e either by
the S1 atom of a second anion or under participation of a
Scheme 7. Possible reaction intermediates in the formation of 9 ac-
cording to pathway a.
=
NC H ). Two sulfur atoms in two trithiocarbonate moie- molecule of pyridine (solvent) which would also transfer the
5 5
ties act as bidentate ligands and chelate one sodium cation proton to the thiolate sulfur atom S1. Proton abstraction
Na1) in a square-planar manner to generate a complex and reprotonation could possibly take place simultaneously
(
anion. The coordination sphere of Na1 is saturated by two in analogy to proton relays in enzyme-catalyzed reactions.
axial coordinated pyridine nitrogen atoms (octahedral coor- The doubly negatively charged intermediate IV would
dination for Na1) originating from two additional trithi- therefore not necessarily be formed (or its lifetime is too
ocarbonate anions. A complex anionic polymer network is short for direct observation). The resulting 5-thiolo-2,3-di-
thus formed. The N-pyridine end of each ligand 9 is axially hydrothiazole anion can be considered as an azaenolate or
coordinated to one sodium ion in the network and the tri- as a metallo-enamine (resonance structure I, Scheme 7).
thiocarbonate at the other end is bound by S1/S2 ligation The second resonance form II can be interpreted as a
to the next sodium ion in the network. Although the resolu- thioacetal anion, which profits from the stabilization by the
tion was not particularly good, we were able to discern that two sulfur atoms. The mercapto group is much more acidic
3
the carbon atom C7 is clearly sp -hybridized (S3 is turned than the methine group in structure III (Scheme 7) and one
out of the plane of the thiazoline ring). The holes in the can assume a solvent-mediated facile proton transfer from
network are filled by the positive counterions (not shown S1 to C7. The outcome is an intramolecular redox reac-
in Figure 4) which are sodium ions that are coordinated by tion – the oxidation of Cα and the reduction of C7. Finally,
six pyridine molecules in an octahedral geometry.
Ruhlandt-Senge et al. have described the solid-state S3 to give 9.
structure of a sodium thiolate derived from metalation of Reaction path b in Scheme 6 starts with the sodium 5-
-mercaptopyridine in the presence of 12-crown-4 and thioxo-1,3-thiazolidin-3-ide Na2e and represents a simple
THF, which shows a few coordinational similarities to 9. A intramolecular one-step 1,2-hydride shift in which Hα
a further molecule carbon disulfide adds to the sulfur atom
2
4596
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1,3-Thiazoline-5-thiolates and 1,3-Thiazole-5(2H)-thiones
FULL PAPER
moves from Cα to C7 (structure III, Scheme 7). This re- FTS-25. MS: Finnigan MAT SSQ 710 and Finnigan MAT 900 XL
TRAP. Elemental analyses (C, H, N, S): Leco CHNS-932 and Vario
arrangement could be assisted by the negative charge of N9,
EL III. NMR spectra were recorded at 250 or 400 MHz and 62.5
the positive partial charge of C7, and the easy polarizability
1
13
1
13
or 100 MHz, for H and C, respectively. For H and C, [D
8
]
of the sulfur atoms. In a second step, an additional mole-
cule of carbon disulfide reacts with the thiolate sulfur atom.
In the course of the formation of the 2,5-dihydrothiazole-
THF (H: δ = 1.73, 3.58 ppm; C: δ = 25.2, 67.4 ppm) and CDCl
3
(H: δ = 7.24 ppm; C: δ = 77.0 ppm) were used as solvents with
TMS as internal standard. If not otherwise mentioned, all pro-
cedures were carried out under argon to exclude moisture from air.
NMR signals were assigned with help of two-dimensional methods
5-trithiocarbonate 9, two new stereocenters are created: the
carbon atoms C7 and C8; cis/trans diastereomers could
therefore be formed. The NMR spectra support this as- (HMQC and HMBC). [D ]THF and [D ]DMSO were purified and
8
6
2
sumption (doubling of C signals is observed). Further sup- dried according to standard procedures. CS was purchased from
port for this is the fact that compound 9 crystallized as the Sigma–Aldrich in a sealed bottle and used without further treat-
ment. The 4-(iminomethyl)pyridines 1a–e were prepared according
trans isomer as clearly seen in its structure motif (Figure 4).
to literature procedures.[ The diethylmagnesium solution was also
1]
prepared using literature procedures.[
28]
Conclusions
General Procedure for Syntheses of 3a–e: A colorless solution of
We conclude from our investigations that the anions 1(–) 4.8 mmol of 4-(iminomethyl)pyridine 1 in 20 mL of THF was co-
oled to –78 °C and 3.0 mL (4.8 mmol) of n-butyllithium (1.6 
solution, hexane fraction) was added through a syringe over the
course of 30–45 min. The color changed immediately to dark blue
obtained from the deprotonation of 4-(iminomethyl)pyri-
dines 1 show typical properties of 2-azaallyl anions. They
react with CS by a 1,3-anionic cycloaddition reaction in
2
(
1a,b), deep red (1c), or magenta (1d,e). The cooling was removed
and the solution was allowed to react overnight at room temp.
.8 mmol of CS was then added at –20 °C; the solution was stirred
which first the 4-pyridin-4-yl-5-thioxo-1,3-thiazolidine-3-
ides 2 and subsequent the 2,3-dihydrothiazole-5-thiolates 3
are formed. The reaction presumably occurs over a two-step
addition of CS2 and continues with a proton migration
4
2
for 15 min at this temperature before the cooling bath was removed.
After 10–20 min, the color turned bright orange. Crystallization
from the Cα atom of 2 to the amide atom N9. This yields began at room temperature. In case of 3a,b, a sample of the crystals
2,3-dihydro-thiazole-5-thiolates 3a–e, which have been veri- was given to X-ray analysis; the rest of the precipitate was filtered
fied by X-ray crystal structure analysis (compounds 3a/3b) off and the product dried in vacuo.
as well as by 2D NMR measurements on 3(a),b–e. Both the
Lithium 2-(Biphenyl-4-yl)-2-methyl-4-(pyridin-4-yl)-2,3-dihydro-1,3-
thiazole-5-thiolate (3a): Precipitate formation: 3 d, dirty yellow/
–
–
sulfur moiety (CS in 3a; CS in 9) and the pyridine nitro-
2
gen atom act as ligands for the metal cations. This has ra-
rely been observed.
2
orange. Yield: 90% (CS addition at –65 °C; containing 2.2 equiv.
of THF); 34.6% (CS addition at –20 °C; containing 3.0 equiv. of
2
Compound 2e could be isolated as the only representa- THF); 51% (CS2 addition at room temperature; containing
1
tive of substance class 2 and its transformation to 3e by a 1.79 equiv. of THF). H NMR ([D
6
]DMSO, 250 MHz, room
1
temp.): δ = 1.85 (s, 3 H, CH
J = 7.25 Hz, Ph), 7.42 (t, 2 H, J = 7.10 Hz, Ph), 7.51 (d, 2 H, J
8.38 Hz, Ph), 7.58–7.63 (m, 4 H, Ph), 8.19 (d, 2 H, J = 6.03 Hz,
H2/6), 8.53 (d, 2 H, J = 6.30 Hz, H3/5) ppm. C NMR ([D
DMSO, 62.5 MHz, room temp.): δ = 29.8 (CH ), 73.9/74.0 (C8),
17.4 (C3/5), 123.0/123.1 (Cα), 125.7 (2 C, Ph), 126.0 (2 C, Ph),
26.6 (2 C, Ph), 127.0 (Ph), 128.8 (2 C, Ph), 138.1 (Ph), 140.3 (Ph),
143.0/143.1 (C4), 148.0 (C2/6), 149.2 (Ph), 156.3/156.5 (C7) ppm.
3
), 4.68 (s, 1 H, NH, H9), 7.31 (t, 1 H,
proton migration was investigated with H NMR experi-
3
3
3
ments. When 3 is protonated with mild protic solvents, the
3
=
1,3-thiazole-5(2H)-thiones 7 and their hydrolysis products –
,3-thiazole-5(2H)-ones 8 – are formed. An interesting by-
3
13
6
]
1
3
product – sodium 4-pyridin-4-yl-2,5-dihydrothiazole-5-tri-
thiocarbonate 9 – was obtained in the reaction of 1e with
1
1
NaH and CS in pyridine. The mechanism of formation is
2
not known exactly, but can be interpreted either as an inter- IR (ATR): ν = 3242 (NH), 3029 (=C–H, aryl), 2972, 2871 (alkyl),
˜
molecular proton shift from N9 over S1 to C7 (acid-base 1596, 1523, 1496 (aryl, ring), 1451, 1416 (alkyl), 1251, 1045 (C–S)
–
1
reaction) or as an intramolecular 1,2-hydride shift from Cα cm . MS (FAB in DMBA, negative): m/z (%) = 361 (97)
–
21 17 2 2
[C H N S ] .
to C7.
Theoretical investigations on the mechanism of carbon
disulfide attack on 4H-pyridin-1-ide with DFT methods are
Lithium 2-Methyl-2-(1-naphthyl)-4-(pyridin-4-yl)-2,3-dihydro-1,3-
thiazole-5-thiolate (3b): The yield (10–30%) cannot be given exactly
presently underway. They include comparative studies on because of the poor reproducibility of the lithium thiolate. Precipi-
the influence of the coordination of CS to the metal ion tate formation: 3 d, 1–2 weeks or by no means, dirty yellow/orange.
2
1
(
lithium) and the attack to the Cα atom or the pyridine
H NMR ([D
6
]DMSO, 250 MHz, room temp.): δ = 2.11 (s, 3 H,
3
CH
3
,), 4.77 (s, 1 H, NH, H9), 7.35 (t, 1 H, J = 8.05 Hz, α-naph),
nitrogen atom. These results are beyond the scope of this
paper and will be presented as a complete study in the near
future. Moreover, we intend to investigate the reactivity of
CS2 towards the metalated aldimines – from 4-(ami-
nomethyl)pyridine – as well.
3
7.42–7.56 (m, 2 H, α-naph), 7.74 (d, 1 H, J = 8.20 Hz, α-naph),
3
4
3
7
=
.85 (dd, 1 H, J = 7.28, J = 1.25 Hz, α-naph), 7.91 (dd, 1 H, J
7.73, J = 1.75 Hz, α-naph), 8.22 (d, 2 H, J = 6.33 Hz, H2/6),
4
3
3
13
8
6
1
1
.62 (d, 2 H, J = 6.30 Hz, H3/5) ppm. C NMR ([D
2.5 MHz): δ = 30.4 (CH ), 73.6 (C8), 117.3 (C3/5), 121.8 (Cα),
23.3 (α-naph), 124.8 (3C, α-naph), 127.5 (α-naph), 129.0 (α-naph),
29.6 (α-naph), 134.5 (α-naph), 143.1 (C4), 143.4 (α-naph), 148.1
6
]DMSO,
3
Experimental Section
(
C2/6), 157.0 (C7) ppm. Because of poor reproducibility in ob-
General Remarks: Spectra were measured with following technical
taining the lithium compound 3b, the corresponding magnesium
devices: NMR: Bruker AC 250 and AC 400. IR-ATR: BIORAD compound (see below) was synthesized which allowed an exact
www.eurjoc.org 4597
Eur. J. Org. Chem. 2005, 4589–4600
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D. Hampe, H. Görls, E. Anders
FULL PAPER
characterization of the α-naphthyl-substituted thiazole-5-thiolate
anion.
DMSO, 250 MHz, room temp.): δ = 2.23 (s, 3 H, CH
3
), 3.78 (s, 3
3
H, OCH ), 6.04 (s, 1 H, NH, H9), 6.94 (d, 2 H, J = 8.83 Hz, Ph),
3
3
4
3
7
.80 (d, J = 4.40 Hz, 2 H, J = 1.58 Hz, H3/5), 7.87 (d, 2 H, J =
Magnesium Bis[2-methyl-2-(1-naphthyl)-4-(pyridin-4-yl)-2,3-dihy-
dro-1,3-thiazol-5-thiolate] (4b): To a solution of 0.276 g (1.06 mmol)
of 1b in 20 mL of THF (cooled to –20 °C) 1.0 mL (0.53 mmol) of
3
4
8
.83 Hz, Ph), 8.41 (d, J = 4.58 Hz, 2 H, J = 1.58 Hz, H2/6) ppm.
1
3
C NMR ([D
3.6 (C8 ?), 55.2 (OCH
28.4 (2 C, Ph), 133.8 (Ph), 148.2 (C2/6), 153.1 (C4), 160.3 (Ph),
63.4 (C7) ppm. IR (ATR): ν˜ = 2979, 2868 (CH , CH), 1603, 1567,
509 (aryl, ring), 1417, 1365 (CH, CH ), 1247, 1018 (C–S) cm .
6
]DMSO, 62.5 MHz, room temp.): δ = 16.5 (CH
3
),
3
1
1
1
3
), 85.9 (Cα), 113.2 (2 C, Ph), 122.9 (C3/5),
[
28]
an MgEt
2
solution (c = 0.53 mol/ L, THF) was added over a
period of 30 min. During this addition the solution turned red-
violet. After the addition was completed, the mixture was allowed
to come to room temperature and to stand overnight. Crystalli-
3
–
1
3
–
MS (DCI, negative): m/z (%) = 314 (100) [C16
Lithium 2-(4-Methoxyphenyl)-2-methyl-4-(pyridin-4-yl)-2,3-dihydro-
,3-thiazole-5-thiolate (3e): Yield: 46.1% (containing 0.9 equiv. of
14 2 2
H N OS ] .
2
zation of the magnesium bis(4H-pyridin-1-ide) Mg[1b(–)] took
[
1]
place. To this suspension, 0.13 mL (0.165 g, 2.162 mmol) of car-
bon disulfide was added at room temperature. The suspension then
turned a dirty dark green. After removal of the cooling bath, the
suspension gradually changed its color from dark green over bright
green, yellow-green and yellow to finally bright orange over a
period of 1–1.5 h. After 12 h of standing at room temperature, the
precipitate was filtered off under inert conditions and dried in
vacuo for 1 d. Traces of moisture turn the color of the precipitate
and the filtrate to purple. Yield: 0.599 g, 52.6% (containing
1
1
THF, corresponds to 2e after complete rearrangement). H NMR
(
[D
6
]DMSO, 250 MHz, room temp.): δ = 1.77 (s, 3 H, CH
3
), 3.68
3
(s, 3 H, OCH
3
), 4.55 (s, 1 H, NH, H9), 6.78 (d, 2 H, J = 8.85 Hz,
3
3
Ph), 7.41 (d, 2 H, J = 8.85 Hz, Ph), 8.15 (d, 2 H, J = 6.15 Hz,
3
13
H2/6), 8.53 (d, 2 H, J = 6.51 Hz, H3/5) ppm. C NMR ([D
DMSO, 62.5 MHz, room temp.): δ = 30.4 (CH ), 55.0 (OCH ), 74.0
C8), 112.7 (2 C, Ph), 117.3 (C3/5), 123.2 (Cα), 126.5 (2 C, Ph),
6
]
3
3
(
.28 equiv. of THF per Mg2 ). H NMR ([D
room temp.): δ = 2.09 (s, 3H, CH ), 4.77 (s, 1 H, NH, H9), 7.34 (t,
H, J = 7.72 Hz, α-naph), 7.40–7.98 (m, 2 H, α-naph), 7.73 (d, 1
+
1
141.8 (Ph), 143.1 (C4), 148.0 (C2/6), 156.5 (C7), 157.7 (Ph) ppm.
2
6
]DMSO, 250 MHz,
General Procedure for the Synthesis of 7 (and 8): Precipitates of the
lithium thiolates 3 were stirred into 30 mL of water. The resulting
yellow to red solution was stirred in a beaker for 30 min and ex-
tracted with 3 × 30 mL of ethyl acetate (the solution can take on
3
3
1
3
H, J = 8.06 Hz, α-naph), 7.79–7.96 (m, 2 H, α-naph), 8.21 (d, 2
3
H, J = 5.91 Hz, H2/6), 8.23 (d, 1 H, α-naph, overlapped with H2/
6
6
1
), 8.60 (d, 2H, 6.4 Hz, H3/5) ppm. 13C NMR ([D
6
]DMSO, a blue note during this step). The organic layer was dried with
), 73.6 (C8), 117.2 (C3/5),
Na SO and concentrated to almost dryness. The following purifi-
21.7 (Cα), 123.2 (α-naph), 124.7 (α-naph), 124.8 (α-naph), 125. 7
2.5 MHz, room temp.): δ = 30.4 (CH
3
2
4
cation is described individually for each thiazole-5(2H)-thione 7.
The thiones 7 are always accompanied by varying amounts of hy-
drolysis side products, the thiazole-5(2H)-ones 8, which are formed
during the workup. Moreover, the thiazole-5(2H)-thiones 7 are
slowly hydrolyzed upon prolonged exposure to air (storage) to 8.
(α-naph), 127.4 (α-naph), 128.9 (α-naph), 129.6 (α-naph), 134.4 (α-
naph), 143.1 (C4), 143.3 (α-naph), 148.0 (C2/6), 157.0 (C7) ppm.
IR (ATR): ν˜ = 3172 (NH), 3053 (=C–H, aryl), 2976, 2878 (alkyl),
1
1
687, 1607, 1552, 1507 [(het)aryl, ring], 1417, 1371, 1332, 1294,
–1
221, 1184, 1013, 802, 775 cm . MS (Micro-ESI, THF/methanol):
2
Stored samples of 8 develop the typical strong smell of H S over
time.
+
m/z (%) = 335 (52) [C19
H
15
N
2
S
2
] .
2
-(Biphenyl-4-yl)-2-methyl-4-(pyridin-4-yl)-1,3-thiazole-5(2H)-thi-
Lithium 2-tert-Butyl-2-methyl-4-(pyridin-4-yl)-2,3-dihydro-1,3-thi-
azole-5-thiolate (3c): Precipitate formation: 1 h, yellow. Yield:
1
one (7a): From 0.679 g of 3a (containing 1.79 equiv. of THF). After
complete removal of the solvent (ethyl acetate), a blue-brown vis-
cous residue was obtained, which consisted of ca. 90% of 7a ac-
cording to its H NMR spectrum. With column chromatography
(silica gel 60, ethyl acetate/chloroform, 1:1), three fractions were
isolated: F1 (beige): 4-phenylacetophenone (0.060 g); F2 (blue): 7a/
8
hydrolysis of the C=S bond takes place on the silica gel. Upon
longer storing in air, the typical smell of hydrogen sulfide becomes
noticeable. Yield (relating to 3a): 45.2% of 7a; 27.4% of 8a (not
pure, but as mixture of both compounds). H NMR ([D
200 MHz, room temp.): 7a: δ = 2.32 (s, 3 H, CH
4
1
δ = 2.25 (s, 3 H, CH
Ph), 8.08 (dd, 2 H, J = 4.4, J = 1.6 Hz, H3/5), 8.81 (dd, 2 H, J
.587 g, 71.0% (containing 1.95 equiv. of THF). 1H NMR ([D
6
]
DMSO, 250 MHz, room temp.): δ = 0.97 (s, 9 H, tBu), 1.48 (s, 3
1
3
3
H, CH ), 3.77 (s, 1 H, NH, H9), 8.09 (d, 2 H, J = 6.30 Hz, H2/6),
3
13
8
6
.38 Hz (d, 2 H, J = 6.48 Hz, H3/5) ppm. C NMR ([D
2.5 MHz, room temp.): δ = 25.75 (tBu), 25.78 (CH
), 79.1 (C8), 117.2 (C3/5), 123.7 (Cα), 142.4 (C4), 147.7
C2/6), 151.5 (C7) ppm. IR (ATR): ν˜ = 3185 (N–H), 3067, 3043
=C–H, aryl), 2967, 2871 (CH , CH /THF), 1683, 1565, 1550,
524, 1496 (aryl, ring), 1457, 1411, 1368 (CH , CH /THF), 1290,
156, 1055, 1002 (C–S), 979, 831 cm . MS (FAB in DMBA): m/z
6
]DMSO,
3
), 39.2
a (0.234 g, 55:45); F3 (yellow): 7a/8a (0.117 g, 80:20); i.e. slow
(
(
(
3 3
C(CH )
3
2
1
1
(
3
2
1
–1
6
]DMSO,
–
3
), 7.39–7.51 (m,
17 2 2
%) = 265 (76) for [C13H N S ] .
3
4
H, Ph), 7.57–7.73 (m, 5 H, Ph), 7.85 (dd, 2 H, J = 4.4, J =
Lithium 2,2-Diphenyl-4-(pyridin-4-yl)-2,3-dihydro-1,3-thiazole-5-thi-
olate (3d): Precipitate formation: 3 d, bright yellow. Yield: 1.416 g,
3
4
.6 Hz, H3/5), 8.76 (dd, 2 H, J = 4.4, J = 1.8 Hz, H2/6) ppm; 8a:
), 7.39–7.51 (m, 4 H, Ph), 7.57–7.73 (m, 5 H,
3
3
1
8
2
=
6
4.1% (containing 2.37 equiv. of THF). H NMR ([D
6
]DMSO,
4
3
3
50 MHz, room temp.): δ = 4.66 (s, 1 H, NH, H9), 7.15 (t, 2 H, J
7.10 Hz, Ph), 7.24 (t, 4 H, J = 6.95 Hz, Ph), 7.49 (d, 4 H, J =
.95 Hz, Ph), 8.19 (d, 2 H, J = 6.15 Hz, H2/6), 8.60 (d, 2 H, J =
4
13
=
4.6, J = 1.6 Hz, H2/6) ppm. C NMR ([D
room temp.): 7a: δ = 28.5 (CH ), 94.9 (C8), 124.5 (C3/5), 126.4,
26.7, 127.2, 127.7, 128.9 (9 C, Ph), 138.5, 139.28, 140.2, 140.4 (C4;
C, Ph), 149.1 (C2/6), 165.1 (Cα), 219.7 (C7) ppm; 8a: δ = 30.1
), 86.8 (C8), 123.3 (C3/5), 126.4, 126.7, 127.0, 127.69, 128.9
9 C, Ph), 137.0, 138.9, 139.33, 140.3 (C4; 3 C, Ph), 149.9 (C2/6),
60.8 (Cα), 192.5 (C7) ppm. MS (Micro-ESI, Methanol): 7a: m/z
6
]DMSO, 50 MHz,
3
3
3
3
3
1
3
6
.30 Hz, H3/5) ppm. 13C NMR ([D
6
]DMSO, 62.5 MHz, room
temp.): δ = 80.9 (C8), 117.3 (C3/5), 122.8 (Cα), 126.6 (2 C, Ph),
26.8 (4 C, Ph), 127.6 (4 C, Ph), 143.0 (C4), 147.2 (2 C, Ph), 148.0
C2/6), 155.8 (C7) ppm. IR (ATR): ν˜ = 3240 (NH), 3058 (=C–H,
aryl), 2977, 2874 (CH , THF), 1595, 1523, 1494 (aryl, ring), 1446
, THF), 1414, 1213, 1044, 1001 (C–S), 982, 892, 834, 749,
(CH
3
1
(
(
1
+
2
(
17 2 2
%) = 361 (100) C21H N S
[M + H] ; exact molecular mass for
(
6
CH
2
C
C
21
H
H
17
N
N
2
S : calcd. 361.083; found 361.083; 8a: m/z (%) = 345 (100)
OS [M + H] ; exact molecular mass for C21H N OS:
17 2
2
–1
+
97 cm . MS (FAB in DMBA): m/z (%) = 348 (24) [C20
H
16
N
2
S
2
] .
+
21
17
2
calcd. 345.106; found 345.106.
Lithium 2-(4-Methoxyphenyl)-4-(pyridin-4-yl)-5-thioxo-1,3-thiazoli-
dine-3-ide (2e): Precipitate formation: 30 min to 1 h, yellow. Yield:
2,2-Diphenyl-4-(pyridin-4-yl)-1,3-thiazole-5(2H)-thione (7d): From
.569 g, 46.1% (containing 0.9 equiv. of THF). 1H NMR ([D
]- 1.416 g of 3d (containing 2.37 equiv. of THF). After complete re-
6
0
4
598
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4589–4600

1,3-Thiazoline-5-thiolates and 1,3-Thiazole-5(2H)-thiones
FULL PAPER
moval of the solvent, a blue foam was obtained which could be
recrystallized from methanol with a little chloroform added. Deep
blue needles resulted. According to the H NMR spectrum, these
needles consisted of the 1,3-thiazole-5(2H)-thione 7d and its hy-
drolysis product [1,3-thiazole-5(2H)-one] 8d in a 87:13 ratio. Chro-
matographic separation (silica gel; chloroform/ethyl acetate, 6:1)
of pure compound 9 was too small for NMR investigations. 1
NMR ([D ]DMSO, 250 MHz, room temp.): δ = 1.78 (s, CH ), 1.97
(s, CH ), 2.03 (s, CH ), 3.69, (s, OCH ), 3.74 (s, OCH ), 3.76 (s,
OCH ), 3.80 (s, OCH ), 4.54 (s, NH or CαH), 4.67 (s, NH or CαH),
6.77–6.94 (m), 7.33–7.41 (m), 7.75–7.86 (m), 8.56–8.65 (m) ppm.
H
6
3
1
3
3
3
3
3
3
1
3
C NMR ([D
6
]DMSO, 62.5 MHz, room temp.): δ = 30.8 (CH
3
),
was not possible because the thione 7d hydrolyses to 8d on SiO
Yield (related to 3d): 28.8% (7d + 8d, 87:13). 1H NMR ([D
DMSO, 250 MHz, room temp.): 7d: δ = 7.39–7.57 (m, 10 H, Ph),
2
.
]-
33.1 (CH ), 55.4 (OCH
89.84, 113.1, 113.9, 117.7, 123.0, 123.5, 126.9, 139.5, 142.1, 143.4,
148.3, 150.6, 156.8, 158.0, 158.6, 165, 195 ppm. IR (ATR): ν˜ =
3
3
), 55.5 (OCH ), 72.2, 72.5, 74.3, 89.77,
3
6
3
4
3
3
7.87 (dd, 2 H, J = 4.51, J = 1.53 Hz, H3/5), 8.77 (d, 2 H, J = 3079 (=C–H), 2837 (OCH ), 1594, 1550, 1507, 1406, 1249, 1133,
–
1
5
.66 Hz, H2/6) ppm; 8d: δ = 7.39–7.57 (m, 10 H, Ph), 8.22 (d, 2 H,
1001, 878, 702, 678 cm .
3
3
13
J = 6.12 Hz, H3/5), 8.84 (d, 2 H, J = 5.96 Hz, H2/6) ppm.
]DMSO, 62.5 MHz, room temp.): 7d: δ = 100.0 (C8),
24.6 (C3/5), 127.3, 128.8, 129.0 (10 C, Ph), 137.8 (C4), 140.3 (2
C, Ph), 149.4 (C2/6), 164.5 (Cα), 218.4 (C7) ppm; 8d: δ = 97.8 (C8),
23.4 (C3/5), 128.6, 128.7, 128.8 (10 C, Ph), 137.0 (C4), 141.7 (2
C, Ph), 150.2 (C2/6), 160.1 (Cα), 191.9 (C7) ppm. MS (Micro-ESI,
C
Crystal Structure Determinations: The intensity data for the com-
pounds were collected with a Nonius KappaCCD diffractometer,
using graphite-monochromated Mo-K
NMR ([D
6
1
α
radiation. Data were cor-
rected for Lorentz and polarization effects, but not for absorption
1
effects.[
(
29,30]
The structures were solved by direct methods
SHELXS[ ) and refined by full-matrix least-squares techniques
31]
+
CHCl
exact molecular mass for C20
47.068; 8d: m/z (%) = 331 (10) C20
CHCl , room temp., 7d + 8d; c = 5.414 mg/25 mL): λmax = 379,
75 nm. IR (ATR): ν˜ = 3065, 3022, 3003 (=C–H, aryl), 1673 (C=S,
3
/CH
3
OH): 7d: m/z (%) = 347 (100) C20
15 2 2
H N S [M + H] ;
2
[32]
against F
o
(SHELXL-97 ). All hydrogen atoms were included at
15 2 2
H N S
: calcd. 347.068; found
H N OS [M + H] . UV/Vis
15 2
calculated positions with fixed thermal parameters. All non-hydro-
+
3
(
5
gen atoms were refined anisotropically.[ The quality of the data
32]
3
2 ϱ
of compounds [3b(THF) ] and 9 are not good; we therefore pub-
lish only the conformation of the molecules and the crystallo-
graphic data; these data are not being deposited with the Cam-
bridge Crystallographic Data Centre. XP (SIEMENS Analytical X-
ray Instruments, Inc.) was used for structure representations.
C=O), 1587, 1548, 1465 (aryl, ring), 1444, 1406, 1284, 1148, 1053
–1
(
C–S), 751, 693 cm . C20
14 2 2 14 2
H N S (7d, 346.48) and C20H N OS
(8d, 330.41) (87:13): calcd. C 69.76, H 4.11, N 8.14, S 17.37; found
C 69.28, H 4.02, N 8.08, S 17.37.
-(4-Methoxyphenyl)-2-methyl-4-(pyridin-4-yl)-2,3-dihydro-1,3-thia-
zol-5(2H)-thione (7e) and 2-(4-Methoxyphenyl)-2-methyl-4-(pyridin-
-yl)-2,3-dihydro-1,3-thiazol-5(2H)-one (8e): From 0.569 g of 3e
containing 0.9 equiv. of THF). After complete removal of the sol-
Crystal Data for 3a(THF)
2
:[33]
48.69 gmol , colorless prism, size 0.10×0.08×0.06 mm, triclinic,
29 2 2 2 4 8
C H35LiN O S ×0.5C H O, Mr =
2
–
1
5
¯
space group P1, a = 9.6538(3), b = 10.0533(2), c = 16.0045(5) Å, α
76.581(1), ß = 81.498(1), γ = 73.629(1)°, V = 1443.95(7) Å, T =
4
(
=
–
3
–1
–
90 °C, Z = 2, ρcalcd. = 1.262 gcm , µ(Mo-K
= 584, 10555 reflections in h(–12/12), k(–12/13), l(–20/20), mea-
sured in the range 2.29° Յ Θ Յ 27.44°, completeness Θmax
9.3%, 6540 independent reflections, Rint = 0.028, 4610 reflections
with F Ͼ 4σ(F ), 341 parameters, 0 restraints, R1obs = 0.060,
wR2obs = 0.154, R1all = 0.0923, wR2all = 0.171, GOOF = 1.043,
α
) = 2.17 cm , F(000)
vent, a bluish-brown, viscous foam was obtained which consisted
1
of 60% of 7e and 15% of 8e according to the H NMR spectrum.
=
Chromatographic purification (silica gel; ethyl acetate/chloroform,
9
1:1) gave one fraction of 4-methoxyacetophenone and five minor
fractions with varying composition of 7e and 8e. After that, the
main fraction was eluted with methanol, which showed almost the
same composition as before the purification. An exact yield cannot
be given because of the rapid hydrolysis of the C=S bond and the
o
o
–
3
largest difference peak/hole: 0.808/–0.721 eÅ .
Crystal Data for [3b(THF) 30LiN
2
]
ϱ
:
C
27
H
2
O
2
S
2
,
Mr
=
partial decomposition of the heterocyclic system which is discerni-
–1
4
85.59 gmol , colorless prism, size 0.03×0.03×0.03 mm, triclinic,
1
ble by the typical smell of released 4-methoxyacetophenone.
NMR (CDCl
.80 (s, 3 H, OCH
H
),
¯
space group P1, a = 12.5396(5), b = 12.9335(6), c = 16.1319(6) Å,
3
, 400 MHz, room temp.): 7e: δ = 2.23 (s, 3 H, CH
3
α = 89.076(3), ß = 89.858(2), γ = 86.364(2)°, V = 2610.68(19) Å ,
3
3
3
), 6.87–6.91 (m, 2 H, Ph), 7.35–7.39 (m, 2 H,
Ph), 7.77 (dd, 2 H, J = 4.43, J = 1.65 Hz, H3/5), 8.72 (d, J =
–3
–1
T = –90 °C, Z = 4, ρcalcd. = 1.235 gcm , µ(Mo-K
F(000) = 1028, 17009 reflections in h(–16/16), k(–16/15), l(–19/20),
measured in the range 4.32° Յ Θ Յ 27.50°, completeness Θmax
4.3%, 11311 independent reflections.
α
) = 2.3 cm ,
3
4
3
4
4
.43 Hz, 2 H, J = 1.64 Hz, H2/6) ppm; 8e: δ = 2.19 (s, 3 H, CH
3
),
=
3
.80 (s, 3 H, OCH ), 6.87–6.91 (m, 2 H, Ph), 7.35–7.39 (m, 2 H,
3
3
9
3
Ph), 8.11 (d, 2 H, J = 6.14 Hz, H3/5), 8.77 (d, 2 H, J = 6.14 Hz,
Crystal Data for 7d:[33] C H N S , Mr = 346.45 gmol , green
prism, size 0.03×0.03×0.02 mm, triclinic, space group P1, a =
–1
H2/6) ppm. 1 C NMR (CDCl
3
, 100 MHz, room temp.): 7e: δ =
), 94.1 (C8), 114.1 (2 C, Ph), 124.4 (C3/5),
27.0 (2 C, Ph), 132.1 (Ph), 138.4 (C4), 149.5 (C2/6), 159.6 (Ph),
64.4 (Cα), 219.1 (C7) ppm; 8e: δ = 31.7 (CH ), 55.3 (OCH ), 87.0
20 14 2 2
3
¯
2
1
1
3 3
9.9 (CH ), 55.3 (OCH
9
1
ρ
.7358(6), b = 10.4742(6), c = 10.5330(8) Å, α = 118.840(3), ß =
3
09.725(3), γ = 97.280(3)°, V = 829.28(9) Å , T = –90 °C, Z = 2,
3
3
–
3
–1
α
calcd. = 1.387 gcm , µ(Mo-K ) = 3.24 cm , F(000) = 360, 5636
(C8), 114.3 (2 C, Ph), 123.1 (C3/5), 127.0 (2 C, Ph), 133.4 (Ph),
reflections in h(–11/12), k(–13/12), l(–13/13), measured in the range
.37° Յ Θ Յ 27.50°, completeness Θmax = 97.1%, 3705 indepen-
dent reflections, Rint = 0.043, 2850 reflections with F Ͼ 4σ(F ),
17 parameters, 0 restraints, R1obs = 0.059, wR2obs = 0.144, R1all
.082, wR2all = 0.160, GOOF = 1.050, largest difference peak and
1
36.8 (C4), 150.4 (C2/6), 159.6 (Ph), 160.3 (Cα), 192.8 (C7) ppm.
2
Sodium {[2-(4-Methoxyphenyl)-2-methyl-4-(pyridin-4-yl)-2,5-dihy-
dro-1,3-thiazol-5-yl]sulfan-yl}(thioxo)methanethiolate (9): The azo-
methine 1e (0.574 g, 2.39 mmol) was added to a suspension of so-
dium hydride (0.064 g, 2.67 mmol) in dry pyridine (20 mL) at room
temp. After stirring of the mixture at room temperature for 48 h,
o
o
2
0
=
–
3
hole: 0.367/–0.586 eÅ .
–
1
CS
2
(0.182 g, 0.144 mL, 2.39 mmol) was added at room tempera-
Crystal Data for 9: C65H N10Na O S , Mr = 1315.69 gmol , yel-
60 2 2 8
¯
ture to the deeply magenta-colored solution, whereupon the color
immediately turned dirty orange. Overlayering of the pyridine solu-
tion with diethyl ether resulted in an orange oil, from which a few
crystals of 9 slowly grew. The following NMR spectroscopic data
are taken from the spectra of the reaction mixture since the yield
low prism, size 0.12×0.12×0.10 mm, triclinic, space group P1, a =
9.6997(7), b = 13.9990(10), c = 15.850(2) Å, α = 81.551(5), ß =
76.952(5), γ = 81.579(6)°, V = 2059.5(3) Å , T = –90 °C, Z = 1,
3
–
3
–1
ρ
calcd. = 1.061 gcm , µ(Mo-K
α
) = 2.69 cm , F(000) = 686, 13235
reflections in h(–12/12), k(–17/18), l(–18/20), measured in the range
Eur. J. Org. Chem. 2005, 4589–4600
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4599

D. Hampe, H. Görls, E. Anders
FULL PAPER
1
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Published Online: September 7, 2005
4600
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Eur. J. Org. Chem. 2005, 4589–4600