Synthesis and physicochemical properties of methyl 3-mercapto arylpropene dithioates

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Phosphorus, Sulfur, and Silicon
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Synthesis and Physicochemical
Properties of Methyl 3-
Mercapto Arylpropene
Dithioates
Marie-Laurence Abasq a , Jean-Louis Burgot a
,
Marylène Chollet-Krugler a , Patricia Courtel a
Béatrice Legouin a
&
a Laboratoire de Chimie Analytique—UFR des
Sciences Pharmaceutiques et Biologiques, Université
de Rennes I , Rennes, France
Published online: 16 Aug 2006.
To cite this article: Marie-Laurence Abasq , Jean-Louis Burgot , Marylène
Chollet-Krugler , Patricia Courtel & Béatrice Legouin (2005) Synthesis and
Physicochemical Properties of Methyl 3-Mercapto Arylpropene Dithioates,
Phosphorus, Sulfur, and Silicon and the Related Elements, 180:5-6, 1505-1506, DOI:
10.1080/10426500590913410
To link to this article: http://dx.doi.org/10.1080/10426500590913410
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Phosphorus, Sulfur, and Silicon, 180:1505–1506, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500590913410
Synthesis and Physicochemical Properties of Methyl
3-Mercapto Arylpropene Dithioates
Marie-Laurence Abasq
Jean-Louis Burgot
`
Marylene Chollet-Krugler
Patricia Courtel
´
Beatrice Legouin
Laboratoire de Chimie Analytique—UFR des Sciences Pharmaceutiques
et Biologiques, Universite´ de Rennes I, Rennes, France
Keywords Dimerization; dithiolethione; dithiolium; redex potential; sulfur-sulfur
cleavage
INTRODUCTION
1,2-dithiole-3-thiones and derivatives are endowed with several promis-
ing pharmacological properties.1 We have shown that the reduction of
3-(methylsulfanyl)-5-(phenyl)-1,2-dithiolium ion 1a1 by NaBH4 is an
efficient way to prepare the corresponding reduction product: methyl-
3-mercapto-3-phenylpropene dithioate 2a1.2 We present here the gen-
eralization of this reaction to other 3-(methylsulfanyl)-1,2-dithiolium
ions 1 to give methyl-3-mercapto-3-phenylpropene dithioates 2. Com-
pounds 2a1 and 2a2 have been previously described according to other
synthetic routes.3,4
SCHEME 1
Received July 9, 2004; accepted October 5, 2004.
Address correspondence to Marie-Laurence Abasq, Laboratoire de Chimie
Analytique—UFR des Sciences Pharmaceutiques et Biologiques, Universite´ de Rennes I,
35043 Rennes Cedex, France. E-mail: marie-laurence.abasq@univ-rennes1.fr
1505

1506
M.-L. Abasq et al.
RESULTS AND DISCUSSION
The 5-aryl derivatives (1a: R5 = Ar) gave 2a in very good yields (83–
96%) conditionally operating at 5◦C. The Z configuration of 2a2 and its
deprotonated form was deduced from two-dimensional NOESY spec-
tra in CDCl3 solvent. Compounds 2a are oxidized by oxygen in basic
and acidic solutions to give a mixture of unidentified products and the
corresponding dithiolium cations, respectively.
Unlike 5-aryl derivatives, the reaction proceeded in a complicated
way for 4-aryl derivatives (1b: R4 = Ar). It gave a mixture of the ex-
pected dithioates and dimers 3. The dimer 3b1 was already isolated
by electrolysis of 4-phenyl-1,2-dithiole-3-thione at platinum electrode
after methylation.5 Purification attemps of the crude product on silica
gel chromatography lead to dimers 3 whereas dithioates 2b could not
be isolated because of their high unstability.
The cyclic voltammetry experiments in DMF/Bu4 NPF6 showed that
2a2 is oxidized at a potential of Epa = +0.61V/ECS to 1a2 following a
−
two-electron process: 2a2 1a + 2e + H+. The redox couple 1a2/2a2
ꢀ
ꢁ
2
is electrochemically irreversible and chemically reversible. The pKa
value of 2a2/2a− was evaluated to 6.5 by calculation in H2O6 and
to 9.4 in DMF.72,8 The anodic peak Epa of 2a2 shifts on addition of
Bu4N(CH3COO)2 (pKa (CH3CO−/CH3CO2H) = 14.2 in DMF) as ex-
pected for proton-coupled electro2n transfer system.
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