Functionalised organosulfur donor molecules: Synthesis of racemic hydroxymethyl-, alkoxymethyl- and dialkoxymethyl-bis(ethylenedithio)tetrathiafulvalenes

Article abstract of DOI:10.1016/S0040-4020(01)00432-X

Short synthetic routes to racemic derivatives of bis(ethylenedithio)tetrathiafulvalene carrying one hydroxymethyl (HMET), alkoxymethyl or dialkoxymethyl side chain are reported along with cyclic voltammetry measurements and conversion of HMET to (2:1) radical cation salts.

Full text of DOI:10.1016/S0040-4020(01)00432-X

TETRAHEDRON
Pergamon
Tetrahedron 57 32001) 5015±5026
Functionalised organosulfur donor molecules:
synthesis of racemic hydroxymethyl-, alkoxymethyl- and
dialkoxymethyl-bisꢀethylenedithio)tetrathiafulvalenes
Nezire Saygili,a R. James Brown,a Peter Day,b Robert Hoelzl,a Poopathy Kathirgamanathan,c
Eileen R. Mageean,a Turan Ozturk,a Melanie Pilkington,a Mohammed M. B. Qayyum,c
Scott S. Turner,b Lars Vorwerga and John D. Wallisa,p
aDepartment of Chemistry and Physics, The Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK
bThe Royal Institution of Great Britain, 21 Albemarle St., London W1S 4BS, UK
cUnit of Speciality Electronic Polymers, School of Electrical, Electronic and Information Engineering, South Bank University,
103 Borough Road, London SE1 0AA, UK
Received 27 November 2000; revised 23 March 2001; accepted 12 April 2001
AbstractÐShort synthetic routes to racemic derivatives of bis3ethylenedithio)tetrathiafulvalene carrying one hydroxymethyl 3HMET),
alkoxymethyl or dialkoxymethyl side chain are reported along with cyclic voltammetry measurements and conversion of HMETto 32:1)
radical cation salts. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
highly delocalised positive charge and the much smaller
anions, are not ideal partners. We have started a programme
to introduce hydrogen bonding functionality into the radical
cation salts. This could involve hydrogen bond formation
between a hydroxymethyl group for instance and an
inorganic anion, but conversely, a suitable hydrogen bond
accepting substituent could be used in combination with an
anion with hydrogen bonding potential such as hydrogen
phosphate. Introduction of a single substituent on one ethyl-
ene bridge of ETcreates a stereogenic centre, and we have
already reported the syntheses of 2, HMET, the enantiopure
derivative carrying a hydroxymethyl side chain,6 and 3 the
derivative carrying a 2-¯uoro-1-hydroxyethyl side chain 3.7
Both of these materials are prepared by reaction of the
dithiolate 4 with cyclic sulfate esters, a class of reagent
we introduced for the synthesis of the chiral tetramethyl
derivative 5.8 We now report a short synthesis of the
racemic modi®cation of HMET 2, and direct routes to its
O-alkylated derivatives 6 and 7. The procedures reported
here make these materials readily available to the synthetic
metals research community for further studies. The ET
derivative with a methoxymethyl group attached to all
four carbons of the ethylene bridges, 8, has also been
prepared as one enantiomer using cyclic sulfate ester
methodology, but only in very low yield. Furthermore,
the syntheses of ETderivatives 9 and 10 which are substi-
tuted with acetal containing functionalities, either a
dimethoxymethyl or a 2-dioxolanyl group, are described
3Scheme 1).
The discovery of superconductivity in the perrhenate radical
cation salt of the organosulfur donor bis3ethylenedithio)-
tetrathiafulvalene, ET, 11 has led to the preparation of an
enormous range of further radical cation salts2 as illustrated
by over 300 crystal structures now in Cambridge Structural
Database. The salts with the complex anions
[Cu{N3CN)2}Br]2 and [Cu3SCN)2]2 have shown the high-
est temperatures for the onset of the superconducting
state.3,4 The latter two salts adopt a layered crystal struc-
ture3,4 in which the molecules of ETare packed into sheets
with their longest molecular axes perpendicular to the sheet,
and sandwiched between layers composed of the polymeric
complex anions. Indeed, in this and the various other pack-
ing arrangements found for radical cation salts of ET, the
ethylene bridges of the ETmolecules lie adjacent to the
anions. Although a good case has been made for there
being weak hydrogen bonding between the two species,5
the lack of a strong directed attraction leads to orientational
disorder for symmetrical anions, and may also be respon-
sible for the high degree of polymorphism shown in the
radical cation salts with anions such as triiodide and hexa-
¯uorophosphate. Indeed, the large organic cation with its
Keywords: organic conductors; bis3ethylenedithio)tetrathiafulvalenes;
radical cation salts; synthesis.
Corresponding author. Tel.: 144-115-848-3149; fax: 144-115-948-
6636; e-mail: john.wallis@ntu.ac.uk
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020301)00432-X

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N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
Scheme 1.
Introduction of hydrogen bonding functionality into
TTF derivatives has been achieved in several other
laboratories using various functional groups, e.g. a
hydrogen phosphate group in 11,9 a thioamide in 1210
and hydroxy functionalities in 13 and 14,11,12 though
none of these molecules have chiral structures. In
our own work we have made TTF derivatives with
fused 1,4-dithiepine rings bearing hydroxymethyl side
chains such as 15 and 1613 and with fused 1,4-di-
thiocene rings bearing hydroxyl functionalities such as
17 and 18, the latter three having chiral structures
3Scheme 2).14
Scheme 2.

N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
5017
Scheme 3.
2. Results and discussion
salts 3BF42, Cl2, PF62) produced black microcrystalline
radical cation salts. Raman spectra of these compounds
showed an absorption, deriving from CvC bond stretch-
ings, in the range 1464±1467 cm21, typical17 of ET
molecules in radical cation salts of stoichiometry 2:1, and
this was supported by chemical analysis data. The Raman
spectrum from a 1:1 radical cation salt would show an
absorption in the region 1410±1420 cm21, though the
absorption from a 3:2 radical cation salt would be in the
same region as that from a 2:1 salt. Further investigations
of the electrical and structural properties of the 2:1 radical
cation salts of HMETare planned.
2.1. Synthesis of the racemic hydroxymethyl derivative
of ET 2
The synthesis of racemic 2 started from inexpensive allyl
alcohol by protection of its hydroxyl group with a t-butyl-
diphenylsilyl group to give 19. Subsequent treatment with
one equivalent of bromine provided the dibromo compound
20. Both reactions take place in yields of over 90%. Treat-
ment of 20 with the disodium salt of dithiolate 415,16 in THF
at room temperature for 12 h, furnished the bicyclic thione
21 in 54% yield after chromatography. Reaction of the
thione 21 with mercuric acetate in chloroform and acetic
acid led to replacement of the exocyclic sulfur atom with
oxygen to give oxo compound 22 in almost quantitative
yield. Cross coupling of oxo compound 22 with the related
unsubstituted oxo compound 23 in triethyl phosphite led to
the production of a 39% yield of the racemic monosubsti-
tuted-ETderivative 24, after chromatographic separation
from unsubstituted ET 1 and disubstituted material 25
3which may be present in up to four diastereoisomeric
forms: two racemic and two meso forms), both arising
from self coupling reactions of starting materials. Removal
of the t-butyldiphenylsilyl protecting group by treatment
with either tetrabutylammonium ¯uoride or 20% hydro-
chloric acid in THF gave racemic 2. The material is a
light orange powder which is sensitive to air oxidation
and should be stored under nitrogen 3Scheme 3).
Zhang et al. have published very recently their own
synthetic route to racemic HMET,18 which involves
cycloaddition of allyl alcohol with the trithione 26, gener-
ated thermally in situ from an oligomer, followed by the
same hydroxyl protection strategy as our own. They also
Table 1. Oxidation potentials 3V, relative to the AgCl/Ag electrode)
measured by cyclic voltammetry
1/2
E1
1/2
E2
1a
0.44
0.49
0.48
0.55
0.56
0.50
0.49
0.41
0.42
0.73
0.78
0.74
0.82
0.80
0.75
0.74
0.65
0.65
31)-2b
31/-)-2a
3b
5b
6a
7a
9c
10c
The results of cyclic voltammetric measurements on
racemic 2 are given in Table 1 along with data for 1, 3
and 5 for comparison, and other monosubstituted ET
derivatives reported here. The ®rst two oxidation potentials
of HMET30.48 and 0.74 V relative to Ag/AgCl) are similar
to those of ET. Electrocrystallisation of 2 in dichloro-
methane in the presence of various tetrabutylammonium
a
Measured in acetonitrile containing 0.1 M tetrabutylammonium hexa-
¯uorophosphate with a scan rate of 20 mV s21
.
b
c
Measured in acetonitrile containing 0.02 M tetrabutylammonium hexa-
¯uorophosphate with a scan rate of 20 mV s21
Measured in acetonitrile containing 0.1 M sodium perchlorate with a scan
rate of 100 mV s21
.
.

5018
N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
Scheme 4.
report the preparation by electrocrystallisation of a 2:1
radical cation perchlorate salt from HMET. The two
synthetic routes are comparable. Their synthesis consists
of six steps from the zinc complex of dithiolate 4 and
allyl alcohol, has an overall yield of ca 8%, and involves
three chromatographic puri®cations, while our own
synthesis from the same starting materials requires an
extra step 3conversion of the zinc complex to the disodium
salt of the dithiolate), has slightly better overall yield, ca
11%, and involves the same number of chromatographic
puri®cations. Either route should be feasible for inter-
disciplinary researcher workers in the ®eld of organic metals
to accomplish 3Scheme 4).
hydroxymethyl substituted thione 27, the unprotected form
of 22, from reaction of the zinc complex of dithiolate 4 with
2,3-dibromopropanol.19 However, when the disodium salt of
4 was used in basic media rather than the zinc complex, the
isomeric thione 28 containing a hydroxy-substituted
dihydro-1,4-dithiepine ring was produced. They report the
self coupling reaction of thione 27 in triethyl phosphite
gives 29, as a mixture of up to four stereoisomers, though
the total yield is only 5%. The need for superconducting
materials to have a well-ordered structure suggests that
the use of a single diastereoisomer of the organosulfur
donor for formation of radical cation salts is preferable,
though of course it cannot be ruled out that one stereoisomer
from a mixture may preferably form crystalline material.
We have made the hydroxymethyl substituted thione 27 in
Kumar et al. have reported the synthesis of the racemic
Scheme 5.

N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
5019
Scheme 6.
the same way, but found separation from unreacted
dibromopropanol 3which is reported to be carcinogenic)
not to be straightforward. For this reason, we preferred to
install the protecting group at the start of the synthesis, and
remove it after the coupling step.
tuted oxo material 23 to give the ethoxymethyl-ET 7 in 34%
yield along with self coupled materials 1 and 39. The oxida-
tion potentials for donors 6 and 7 have similar values to
those of HMET 2 3Scheme 5).
Tetrasubstituted derivatives of ET are attractive targets
since they offer the potential for interaction with anions at
either `end' of the molecule, however, their syntheses are
more problematic, requiring two substitution reactions at
secondary carbon atoms. Interestingly, the racemic forms
of these materials, e.g. the tetramethyl derivative 5, can
only be prepared by preparation of both enantiomers sepa-
rately and then making a 1:1 mixture. It is a rare case of the
enantiomer being easier to synthesize than the racemate!
Synthesis of enantiomerically pure tetramethyl-ET 5
involves reaction of the cyclic sulfate ester 40 with the
disodium salt of dithiolate 4 to give a reasonable yield
330%) of the bicyclic thione, and is completed by self
coupling in triethyl phosphite.20 However, when the size
of substituents on the cyclic sulfate ester is increased
smaller yields are obtained in the cyclisation step. The
cyclic sulfate ester 42 which has two chirally disposed
methoxymethyl substituents was prepared from the corre-
sponding enantiopure diol21 by conversion to the cyclic
sul®te ester 41 with thionyl chloride and pyridine and subse-
quent oxidation with sodium periodate and a catalytic
amount of ruthenium3IV) oxide.6 However, reaction of
this cyclic sulfate ester with the disodium salt of dithiolate
4 gave only ca 5% of thione 43. Nevertheless, this could be
converted to the tetramethoxymethyl-ETderivative 8 by
exchange of thione sulfur for oxygen to give 44 and then
self coupling in triethyl phosphite. With larger substituents
on the cyclic sulfate ester e.g. with two benzyloxymethyl
2.2. Synthesis of alkoxymethyl derivatives of ET 6±8
Although O-alkylated derivatives could in principle be
prepared by ether formation from HMET 2, only ®ve
synthetic steps are required if the alkyl group is introduced
to allyl alcohol in the ®rst step instead of the t-butyl-
diphenylsilyl protecting group. Thus, 3-methoxypropene
30, prepared from allyl alcohol, was brominated to give
32, and then reacted with the zinc complex of dithiolate 4
in acetonitrile to give the thione 34 in 49% yield. Exchange
of the thione sulfur atom of 34 for oxygen using mercuric
acetate in acetic acid and chloroform gave oxo compound
36 in 92% yield. In the ®nal step oxo compound 36 was
coupled with the unsubstituted oxo material 23 to yield the
racemic cross-coupled methoxymethyl-ETderivative 6 in
45% yield after chromatography. A later band gave a
mixture of stereoisomers of 38 from self coupling of the
substituted oxo compound 36. The racemic ethoxyethyl-
ETderivative 7 was prepared from commercially available
allyl ethyl ether in just four steps. In this case, 2,3-dibromo-
1-ethoxypropane 33 was prepared and reacted with the
disodium salt of dithiolate 4 to give the thione 35 in 60%
yield. This procedure is preferable to reaction with the zinc
complex of dithiolate 4, which had been used to prepare 34,
since the reaction is cleaner and gives a better yield.
Exchange of the thione sulfur atom in 35 for oxygen gave
oxo compound 37, which was coupled with the unsubsti-

5020
N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
Scheme 7.
groups, the reaction with dithiolate 4 failed completely.
Other workers have reported the synthesis of the cis
di-3hydroxymethyl) thione 45, and its conversion to an
unseparated mixture of two stereoisomers of the tetrakis-
genic centres. Thus in the 13C NMR spectrum there are
small differences between the two methoxy carbon
resonances 3d: 55.4 and 54.7) and between the two carbon
resonances of the ethylene group 3d: 65.8 and 65.6).
Exchange of the thiocarbonyl sulfur atom for oxygen in
the usual way gave the oxo compounds 52 and 53 in yields
of over 90%. Finally, cross coupling of each compound with
the unsubstituted oxo compound 23 gave the monosubsti-
tuted ETderivatives 9 and 10 in reasonable yields 348 and
36%), along with ETand the disubstituted materials 54 and
55 as mixtures of diastereoisomers. Attempts to convert the
acetal groups in the organosulfur donors 9 and 10 to the
aldehyde 56 have been unsuccessful to date. For example,
treatment with 20% hydrochloric acid and THF at room
temperature did not hydrolyse the acetal, though under
more vigorous conditions the substrate was consumed.
22
3hydroxymethyl) derivative of ET3Scheme 6).
2.3. Synthesis of dialkoxymethyl derivatives of ET 9±10
With a view to preparing the ETderivative substituted with
an aldehyde group, 56, we have prepared the corresponding
acetals 9 and 10 by cross coupling methodologies. Thus, the
dimethyl acetal and ethylene acetal of acrolein 46 and 47
were brominated to give 48 and 49, and these were reacted
with the disodium salt of the dithiolate 4 to give the thiones
50 and 51 in 41 and 70% yields, respectively. Both acetal
groups are diastereotopic, due to their attachment to stereo-

N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
5021
Scheme 8.
The hydrolysis of ketals in related organosulfur donors has
been dif®cult, thus bis-ketal 5723 required re¯uxing in 15%
sulphuric acid in THF, and 58 could not be cleanly depro-
tected.14 The cyclic voltammograms of the derivatives 9 and
10 show two oxidation peaks, with E1/2 values typical of ET
derivatives 3Table 1). Several related organosulfur donors
containing vinyl aldehyde groups24 and the tetraacetal 59
have been reported 3Scheme 7).25
electrical properties of the corresponding radical cation
salts.
4. Experimental
4.1. General
NMR spectra were measured on a JEOL GX 270 machine at
1
270 MHz for H and at 67.8 MHz for 13C using CDCl3 as
Since these synthetic routes to ETderivatives make the
central double bond at the end of the synthesis, access to
an increasing range of monosubstituted oxo compounds
such as 36, 37, 52, and 53 opens up access to further
solvent and tetramethylsilane 3TMS) as standard, and
measured in ppm. down®eld from TMS, unless otherwise
stated. Coupling constants 3J) are given in Hz. IR spectra
were recorded on a ATI Mattson Genesis Series FTIR
machine as liquid ®lms or nujol mulls. Re¯ective Raman
spectra were measured with a Renishaw System 1000
Ramascope using a He±Ne laser 3lˆ632.8 nm) with
10 mm slits and £50 objective lens. Mass spectra were
recorded at the EPSRC Mass Spectrometry Centre. Flash
chromatography was performed on 40±63 silica gel
3Merck). Cyclic voltammograms were measured with a
PAR 263/273 electrochemical system using a platinum
foil anode 3ca 2 cm2) and over the range 20±1000 mV;
measurements were made on acetonitrile solutions
30.1 mM), using tetra n-butylammonium perchlorate
30.1 M) or tetra n-butylammonium hexa¯uorophosphate
30.1 M, unless indicated otherwise) under an atmosphere
of nitrogen, using a Ag/AgCl reference electrode. 3-
Methoxypropene was prepared by a literature method.26
unsymmetrically
substituted
organosulfur
donors,
providing that the second component in the synthesis has
a C2 axis, for example an enantiopure trans disubstituted
1,3-dithiolo-[4,5-b]-1,4-dithiin-2-one or a 6,6-disubstituted
1,3-dithiolo-[4,5-b]1,4-dithiepin-2-one such as 60. Thus,
cross coupling of 52 or 53 with 60 yielded 61 and 62 after
separation from self coupled products 3Scheme 8).
3. Conclusions
A series of monosubstituted derivatives of EThave been
prepared by short synthetic routes, and the intermediate
oxo compounds prepared in the course of this work are
now available for cross coupling reactions with other dithio-
lones to prepare further novel donors. Further studies to
prepare and investigate the radical cation salts of the donors
described here are to be undertaken. The availability of
HMET 2 now provides a molecule with a side arm for
linking the ETmoiety to other systems, or alternatively
the ETmoiety can be built up from an appropriately substi-
tuted allyl ether, and opens many possibilities. If more than
one molecule of HMETis to be attached to another
molecular species, the use of the single enantiomer form
will avoid the formation of more than one diastereoisomer
of product. Since HMETis available now in both enantio-
pure6 and racemic forms, there is an opportunity for
investigations of the effects of a chiral environment on the
4.1.1. 3-ꢀt-Butyldiphenylsilyloxy)prop-1-ene, 19. T o a
solution of allyl alcohol 30.52 g, 9.0 mmol) in dry DMF
320 ml) was added sequentially imidazole 36.80 g,
100 mmol) and t-butyldiphenylsilyl chloride 32.75 g,
10 mmol). After stirring at room temperature for 20 h,
water 390 ml) and dichloromethane 340 ml) were added,
the dichloromethane layer separated, and the aqueous
layer extracted twice more with dichloromethane
32£40 ml). The combined organic solution was washed
sequentially with ice-cold HCl 33 M, 3350 ml) and water
350 ml) and dried over MgSO4. Removal of the solvent

5022
N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
under reduced pressure afforded the silylated product 19
32.60 g, 96%) as a colourless oil: dH: 7.65 34H, m, Ar-H4),
7.38 36H, m, Ar-H6), 5.91 31H, ddt, Jˆ17.0, 10.4, 4.3 Hz,
2-H), 5.38 31H, ddt, Jˆ17.0, 1.9, 1.9 Hz, 1-H 3trans to
2-H)), 5.11 31H, ddt, Jˆ10.4, 1.9, 1.9 Hz, 1-H 3cis to
2-H)), 4.20 32H, m, 3-H2), 1.07 39H, s, 3£CH3); dC:
136.9, 135.5, 129.6 and 127.6 3Ar-C12), 133.6 32-C), 113.8
31-C), 64.6 33-C), 26.8 33£CH3), 19.3 3C3CH3)3); nmax
3evaporated ®lm): 3470, 3070, 2934, 1590, 1468, 1428,
1112, 822 cm21; found C, 77.4; H, 8.4%, C19H24OSi
requires C, 77.0; H, 8.2%; m/z 3CI): 314 3[M1NH31H]1,
65), 297 3[M1H]1, 100), 239 3M2C3CH3)3, 19%); HRMS:
3CI) found [M1H]1 297.1684, [C19H24OSi1H]1 requires
297.1675.
4.2.5. 2-ꢀ10-,20-Dibromoethyl)-1,3-dioxolane, 49. Addition
of bromine at 2708C then by the general method to give 49
as a colourless liquid 311.0 g, 84%) bp 888C. dH: 5.22 31H,
d, Jˆ6.4 Hz, 2-H), 4.26 31H, ddd, Jˆ7.7, 6.4, 2.9 Hz, 10-H),
4.11 32H, m, 4a-,5a-H), 3.99 32H, m, 4b-,5b-H), 3.79 32H,
m, 20-H2); dC: 101.8 32-C), 65.9 and 65.8 34-,5-C), 52.7
310-C), 31.5 320-C); nmax: 2963, 2887, 1472, 1425, 1378,
1279, 1230, 1154, 1121, 1066, 1033, 947, 911, 882, 732,
606 cm21
;
C5H7O2Br2 requires 256.8813.
HRMS: 3EI) found [M2H]1 256.8811,
4.3. General method for preparation of substituted 5,6-
dihydro-1,3-dithiolo[4,5-b]1,4-dithiin-2-thiones
To a stirred solution of the disodium salt of dithiolate 415,16 in
dry THF 3ca 0.5 M) under nitrogen at 08C was added a solu-
tion of the dibromo compound 31 equiv.) in THF 3ca 0.5 M) at
room temperature. After stirring for 12 h, the solvent was
removed under reduced pressure and the residue was extracted
with dichloromethane, washed three times with water, dried
over MgSO4 and concentrated in vacuo and puri®ed.
4.2. General method for brominations
To a stirred solution of the alkene in chloroform 3ca 1 M)
maintained at 08C was added slowly, dropwise, a solution of
bromine 31 equiv.) in chloroform 3ca 1 M). The resultant
mixture was stirred for a further 30 min at that temperature,
after which time it was allowed to warm to room tempera-
ture and stirred for a further 3 h. The solution was washed
twice with aqueous sodium thiosulfate solution and twice
with water, dried over MgSO4, and the solvent removed in
vacuo to afford the product.
4.3.1. 5-ꢀt-Butyldiphenylsilyloxy)methyl-5,6-dihydro-1,3-
dithiolo[4,5-b]1,4-dithiin-2-thione, 21. Puri®cation by
¯ash chromatography 3hexane/ethyl acetate 310:1)) afforded
21 34.97 g, 54%) as a yellow solid; mp 100±1028C. dH: 7.66
34H, m, Ar-H4), 7.37 36H, m, Ar-H6), 3.98±3.75 33H, 2£m,
CH2OSiR3 and 5-H), 3.31 31H, dd, Jˆ13.5, 5.8 Hz, 6-Ha),
3.19 31H, dd, Jˆ13.5, 2.8 Hz, 6-Hb), 1.08 39H, s, 3£CH3);
dC: 207.1 3CvS), 135.3, 132.3, 129.9 and 127.7 3Ar-C12),
123.7 and 121.9 33a-, 7a-C), 64.6 3CH2OSiR3), 45.1 35-C),
31.1 36-C), 26.7 33£CH3), 19.1 3C3CH3)3); nmax: 1109, 1062,
1025, 893, 821, 737, 704, 604 cm21; m/z: 3CI) 493
3[M1H]1, 20), 492 3M1, 20), 435 365), 239 335), 161
3100), 117 343), 105 329), 77 325%); HRMS: 3CI) found
[M1H]1493.0278, [C22H24OS5Si1H]1 requires 493.0278.
4.2.1. 3-ꢀt-Butyldiphenylsilyloxy)-1,2-dibromopropane,
20. Colourless oil 39.81 g, 91%), dH: 7.68 34H, m, Ar-H4),
7.39 36H, m, Ar-H6), 4.20 31H, m, 2-H), 4.09 31H, dd,
Jˆ11.3, 3.8 Hz, 3-Ha), 4.00±3.91 32H, m, 3-Hb and
1-Ha), 3.83 31H, dd, Jˆ10.2, 4.7 Hz, 1-Hb), 1.09 39H, s,
3£CH3); dC: 135.6, 135.5, 129.8 and 127.8 3Ar-C12), 64.6
33-C), 51.5 32-C), 32.6 31-C), 26.7 33£CH3), 19.3
3C3CH3)3); nmax 3evaporated ®lm): 3070, 2934, 2860,
1468, 1428, 1112, 702 cm21; found C, 49.9; H, 5.2%,
C19H24Br2OSi requires C, 50.0; H, 5.3%; HRMS: 3CI)
found [M1NH31H]1 472.0307, [C19H24OSiBr21NH31H]1
requires 472.0307.
4.3.2. 5,6-Dihydro-5-ethoxymethyl-1,3-dithiolo[4,5-b]1,4-
dithiin-2-thione, 35. Puri®cation by ¯ash chromatography
3ethyl acetate) afforded 35 as a reddish brown oil 3340 mg,
60%): dH: 3.81 31H, m, 5-H), 3.78 32H, m, CH2OEt), 3.57
32H, m, OCH2CH3), 3.33 32H, m, 6-H2), 1.21 33H, t, CH3);
dC: 208.0 3CvS), 123.7 and 122.3 33a-, 7a-C), 71.3
3CH2OEt), 67.2 3OCH2Me), 43.0 35-C), 31.6 36-C), 15.0
3CH3); m/z 3CI): 283 3[M1H]1, 100), 282 3M1, 10), 196
330), 85 325), 29 310%); HRMS: 3CI) found M1 281.9335,
C8H10OS5 requires 281.9335.
4.2.2. 1,2-Dibromo-3-methoxypropane, 32. Slightly
yellow liquid 336.3 g, 73%): dH: 4.26 31H, m, 2-H), 3.80
34H, m, 1-,3-H2), 3.45 33H, s, CH3); dC: 73.4 33-C), 59.2
3CH3), 48.9 32-C), 32.9 31-C); nmax 3neat): 2988, 2930, 2828,
2740, 1452, 1382, 1324, 1260, 1210, 1118, 1016, 958, 922,
876, 668 cm21
.
4.2.3. 1,2-Dibromo-3-ethoxypropane, 33. Colourless
liquid 311.94 g, 84%): dH: 4.18 31H, m, 2-H), 3.76 34H,
m, 1-, 3-H2), 3.52 32H, q, Jˆ7.0 Hz, CH2CH3), 1.16 33H,
t, Jˆ7.0 Hz, CH3); dC: 71.4 33-C), 66.7 3CH2CH3), 49.4
32-C), 33.4 31-C), 15.0 3CH3); nmax 3evaporated ®lm):
2976, 2872, 1444, 1378, 1356, 1260, 1232, 1124 and
4.3.3. 5,6-Dihydro-5-dimethoxymethyl-1,3-dithiolo-[4,5-
b]-1,4-dithiin-2-thione, 50. Puri®cation by ¯ash chromato-
graphy 3hexane/dichloromethane 1:1) gave 50 32.10 g, 41%)
as a yellow solid, mp 738C. dH: 4.52 31H, d, Jˆ7.7 Hz,
CH3OMe)2), 3.89 31H, dt, Jˆ7.7, 5.2 Hz, 5-H), 3.47 and
3.45 36H, 2£s, 2£OCH3), 3.25 32H, d, Jˆ5.2 Hz, 6-H2);
dC: 208.1 3CvS), 125.8 and 122.9 33a-,7a-C), 104.4
3CH3OMe)2), 55.4 and 54.7 32£OCH3), 47.6 35-C), 31.0 36-
C); nmax.: 1228, 1182, 1113, 1066, 973, 879, 721 cm21; found
C: 31.8, H: 3.4%. C8H10O2S5 requires C: 32.2, H: 3.4%.
988 cm21
.
4.2.4. 1,2-Dibromo-3,3-dimethoxypropane, 48. Addition
of bromine at 2708C, then by the general method to give
48 as a colourless oil 318.0 g, 80%) bp 70±718C, 0.1 mmHg.
dH: 4.54 31H, d, Jˆ4.4 Hz, 3-H), 4.21 31H, m, 2-H), 3.79
32H, m, 1-H2), 3.50 and 3.48 36H, 2£s, 2£OCH3); dC: 103.7
33-C), 55.8 and 55.5 32£OCH3), 51.3 32-C), 33.1 31-C);
4.3.4. 5,6-Dihydro-5-ꢀ10-,30-dioxolan-20-yl)-1,3-dithiolo-
[4,5-b]-1,4-dithiin-2-thione, 51. Residual dibromo compound
49 was distilled off by heating in vacuo. Chromatography of
the residue 3hexane/dichloromethane 5:1) gave 51 32.01 g,
n
max: 2992, 2934, 2832, 1446, 1357, 1311, 1239, 1196,
1114, 1066, 966, 876, 575, 476 cm21
.

N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
5023
70%) as a yellow solid, mp 98±1008C. dH: 5.16 31H, d,
Jˆ5.8 Hz, 20-H), 4.01 34H, m, 40-,50-H2), 3.79 31H, m, 5-
H), 3.28 32H, m, 6-H2); dC: 208.0 3CvS), 125.7 and 123.5
33a-,7a-C), 103.4 320-C), 65.8 and 65.6 340-,50-C), 48.8 35-C),
30.8 36-C); nmax: 1225, 1129, 1066, 1036, 1007, 973, 939,
892, 865, 800, 722 cm21; found C: 32.0, H: 2.8%.
C8H8O2S5 requires C: 32.4, H: 2.7%; HRMS: 3EI) found
M1 295.9117. C8H8O2S5 requires 295.9128.
found [M1NH31H]1 494.0772, [C22H24O2S4Si1NH31H]1
requires 494.0772.
4.3.8. 5-Methoxymethyl-5,6-dihydro-1,3-dithiolo[4,5-b]1,4-
dithiin-2-one, 36. Evaporation gave the oxo compound 36
as an oil which slowly solidi®ed 33.90 g, 92%), mp 348C,
dH: 3.90 31H, m, 5-H), 3.77 31H, dd, Jˆ9.6, 8.1 Hz,
CHaOMe), 3.57 31H, dd, Jˆ9.6, 5.9 Hz, CHbOMe), 3.40
33H, s, CH3), 3.32 32H, m, 6-H2); dC: 188.5 3CvO), 114.0
and 112.7 33a-,7a-C), 73.3 3CH2OMe), 59.1 3CH3), 44.3
35-C), 32.4 36-C); found C, 33.1; H, 3.0%. C7H8O2S4
requires C, 33.3; H, 3.2%.
4.3.5. Preparation of 5-ꢀmethoxymethyl)-5,6-dihydro-
1,3-dithiolo[4,5-b]1,4-dithiin-2-thione, 34. The tetra-
ethylammonium salt of the zinc complex of dithiolate 415
348.1 g, 0.067 mol) and 32 323.1 g, 0.1 mol) were stirred
together in acetonitrile 31 l) under nitrogen and warmed in
an oil bath at 708C for three days. The mixture was heated to
re¯ux for a further day. The solvent was removed in vacuo,
and the residue treated with dichloromethane 3300 ml) and
®ltered to remove salts. After evaporation of solvent, the
residue was subjected to Kugelrohr distillation 3708C,
0.02 mmHg) to remove residual 32. The residue was washed
thoroughly with chloroform 35£100 ml) and the washings
decanted from an oily phase and combined. After evapora-
tion of the solvent, the residue was puri®ed by ¯ash chro-
matography 3hexane/dichloromethane 32:3)). Three main
fractions containing the desired product were collected.
The ®rst contained a trace of 32 which was removed by
trituration with hexane, the second was pure by TLC, and
the third fraction required further chromatography 3hexane/
ether 31:1)). The combined puri®ed fractions of 34 313.1 g,
49%) were obtained as a yellow powder, mp 438C: dH: 3.89
31H, m, 5-H), 3.76 31H, dd, Jˆ9.6, 8.1 Hz, CHaOMe), 3.58
31H, dd, Jˆ9.6, 5.9 Hz, CHbOMe), 3.41 33H, s, CH3), 3.31
32H, d, Jˆ4.8 Hz, 6-H2); dC: 207.6 32-C), 123.6 and 122.1
33a-,7a-C), 73.2 3CH2OMe), 59.2 3CH3), 42.6 35-C), 31.4
36-C); nmax: 1308, 1178, 1112, 1072, 962, 878, 784,
723 cm21; found C, 31.3; H, 2.8%. C7H8OS5 requires C,
31.3; H, 3.0%; m/z: 3EI) 268 3M1, 75), 196 315%).
4.3.9. 5,6-Dihydro-5-ethoxymethyl-1,3-dithiolo[4,5-b]1,4-
dithiin-2-one, 37. Puri®cation by ¯ash chromatography
3hexane/ethyl acetate 4:1) afforded 37 30.90 g, 42%) as a
pale yellow oil: dH: 3.91 31H, m, 5-H), 3.79 31H, dd, Jˆ9.6,
8.5 Hz, CHaOEt), 3.61 31H, dd, Jˆ9.6, 5.7 Hz, CHbOEt),
3.55 32H, apparent dq, ABX3 system from OCH2Me), 3.33
32H, m, 6-H2), 1.21 33H, t, Jˆ6.9 Hz, CH3); dC: 188.7
3CvO), 114.2 and 112.7 33a-, 7a-C), 71.3 3CH2OEt), 67.0
3OCH2CH3), 44.6 35-C), 32.5 36-C), 15.0 3CH3); nmax
3evaporated ®lm): 2974, 1674, 1500, 1412, 1376, 1294,
1110, 890, 766 cm21; found C, 36.3; H, 3.7% C8H10S4O2
requires C, 36.1; H, 3.8%; m/z 3CI): 284 3[M1NH4]1, 50),
266 3M1, 100%).
4.3.10. 5,6-Dihydro-5-dimethoxymethyl-1,3-dithiolo-[4,5-
b]-1,4-dithiin-2-one, 52. Puri®cation by ¯ash chromato-
graphy 3hexane/ethyl acetate 5:1) gave 52 31.50 g, 92%)
as a pale yellow solid, mp 38±398C. dH: 4.53 31H, d,
Jˆ7.7 Hz, CH3OMe)2), 3.94 31H, dt, Jˆ7.7, 5.3 Hz, 5-H),
3.46 and 3.43 36H, 2£s, 2£OCH3), 3.25 32H, d, Jˆ5.3 Hz,
6-H2); dC: 188.5 3CvO), 116.1 and 113.3 33a-,7a-C), 104.1
3CH3OMe)2), 54.9 and 54.3 32£OCH3), 49.1 35-C), 31.6
36-C); nmax.: 1682, 1623, 1507, 1309, 1227, 1189, 1102,
1081, 1065, 965, 878, 875, 764, 666 cm21; found C: 33.8,
H: 3.6%. C8H10O3S4 requires C: 34.0, H: 3.6%.
4.3.6. General method for preparation of substituted 5,6-
dihydro-1,3-dithiolo[4,5-b]1,4-dithiin-2-ones. To a solu-
tion of the thione in chloroform 3ca 0.1 M) was added
glacial acetic acid 32 ml per 10 ml CHCl3) followed by
mercuric acetate 32.5 equiv.) and the reaction mixture was
stirred at room temperature for 2 h during which the solution
lightened in colour and a white precipitate was obtained.
The mixture was ®ltered, and the ®ltrate washed sequen-
tially with water, three times with aqueous NaHCO3 and
again with water 350 ml) and dried over MgSO4. T he
solvent was evaporated under reduced pressure.
4.3.11. 5,6-Dihydro-5-ꢀ10-,30-dioxolan-20-yl)-1,3-dithiolo-
[4,5-b]-1,4-dithiin-2-one, 53. Evaporation of solvent gave
53 31.00 g, 99%) as a pale yellow solid, mp 90±928C, dH:
5.16 31H, d, Jˆ6.1 Hz, 20-H), 4.00 34H, m, 40-,50-H2), 3.84
31H, m, 5-H), 3.30 32H, m, 6-H2); dC: 188.8 3CvO), 116.2
and 114.1 33a-,7a-C), 103.4 320-C), 65.7 and 65.6 34-,50-C),
50.5 35-C), 31.6 36-C); nmax.: 1694, 1625, 1500, 1222, 1133,
1032, 1007, 948, 908, 889, 863, 607 cm21; found C: 34.0, H:
2.9%. C8H8O3S4 requires C: 34.3, H: 2.9%; m/z: 3EI) 280
3M1, 25), 88 350), 76 347), 73 3[1,3-dioxolan-2-yl]1,100%).
4.3.7. 5-ꢀt-Butyldiphenylsilyloxy)methyl-5,6-dihydro-1,3-
dithiolo[4,5-b]1,4-dithiin-2-one, 22. Puri®cation by ¯ash
chromatography 3hexane/ethyl acetate 310:1)) afforded the
product 22 as a pale yellow oil 33.81 g, 99%): dH: 7.67 34H,
m, Ar-H4), 7.39 36H, m, Ar-H6), 3.99 31H, dd, Jˆ12.1,
9.9 Hz, CHaOSiR3), 3.83 31H, m, 5-H),3.82 31H, dd,
Jˆ12.1, 5.7 Hz, CHbOSiR3), 3.32 31H, dd, Jˆ13.3,
5.5 Hz, 6-Ha), 3.23 31H, dd, Jˆ13.3, 3.2 Hz, 6-Hb), 1.07
39H, s, 3£CH3); dC: 188.7 3CvO), 135.5, 132.7, 130.0
and 127.9 3Ar-C12), 114.4 and 112.7 33a-, 7a-C), 64.9
3CH2OSiR3), 47.1 35-C), 32.3 36-C), 26.8 33£CH3), 19.3
3C3CH3)3); nmax 3evaporated ®lm): 2958, 2858, 1678,
1590, 1468, 1262, 1112, 868 and 704 cm21; HRMS: 3CI)
4.4. General procedure for preparation of substituted
ET derivatives
A mixture of oxo compounds was heated in triethyl phos-
phite to 808C under nitrogen for 2 h to give an orange solu-
tion. Triethyl phosphite was removed by distillation in
vacuo, and the residue was stirred with chloroform for
10 min and ®ltered to remove ET. The products were sepa-
rated by chromatography.
4.4.1. 5-ꢀt-Butyldiphenylsilyloxy)methyl-5,6-dihydro-2-
ꢀ50,60-dihydro-1,3-dithiolo[4,5-b]-1,4-dithiin-20-ylidene)-
1,3-dithiolo[4,5-b]-1,4-dithiin, 24. From an equimolar

5024
N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
mixture of 22 and 23. Puri®ed by ¯ash chromatography
3hexane/ethyl acetate 5:1), collecting the band with Rf
0.52 gave 24 30.38 g, 39%), as an orange solid, mp 54±
568C. dH: 7.62 34H, m, Ar-H4), 7.41 36H, m, Ar-H6),
3.94 31H, dd, Jˆ10.4, 11.8 Hz, CHaOSiR3), 3.76 32H, m,
CHbOSiR3 and 5-H), 3.29 34H, s, 50-, 60-H2), 3.28
31H, dd, Jˆ13.2, 4.7 Hz, 6-Ha), 3.18 31H, dd, Jˆ13.2,
3.3 Hz, 6-Hb), 1.06 39H, s, 3£CH3); dC: 135.3, 132.6,
129.8 and 127.7 3Ar-C12), 114.6, 113.6 and 113.2 33a-,3a0-
7a-,7a0-C), 111.7 32a-,2a0-C), 64.9 3CH2OSiR3), 45.6 35-C),
31.8 36-C), 30.0 350- and 60-C), 26.7 33£CH3), 19.1
3C3CH3)3); found C, 49.6; H, 4.3%. C27H28OSiS8 requires
C, 49.7; H, 4.3%; nmax: 1284, 1106, 1001, 915, 820, 770,
737, 700, 608 cm21; m/z 3CI): 653 3[M1H]1, 4), 387 37),
297 3[Ph2SiC3CH3)3-OCH2CHvCH21H]1, 54), 256
3[Ph2SiC3CH3)3OH]1, 51), 239 336), 236 342), 196 383),
45 3100%).
dichloromethane 1:5) eluted some ET®rst. The second frac-
tion gave the desired cross coupled product 9 30.12 g, 48%)
as a pale orange solid, mp 1708C. dH: 4.48 31H, d, Jˆ8.0 Hz,
CH3OMe)2), 3.80 31H, m, 5-H), 3.46 and 3.42 36H, 2£s,
2£OCH3), 3.29 34H, s, 50-,60-H2), 3.14 32H, m, 6-H2); dC:
116.6, 114.4 and 113.8 33a-,3a0-,7a-,7a0-C), 112.1 and 111.9
32-,20-C), 104.9 3CH3OMe)2), 55.5 and 54.5 32£OCH3),
47.9 35-C), 31.8 36-C), 30.2 350-,60-C); nmax: 1288, 1259,
1183, 1114, 1051, 967, 907, 800, 770 cm21; found C:
33.6, H: 3.0%. C13H14O2S8 requires C: 34.0, H: 3.1%; m/z
3EI) 458 3M1, 100), 430 3[M2CH2CH2]1, 25), 356
3[M2CH2CHCH23OMe)2]1,45). The ®nal band gave a
mixture of stereoisomers of bis33,3-dimethoxypropylene-
1,2-dithio)tetrathiafulvalene 54 30.08 g, 52%) as an orange
solid, mp 1688C. dH: 4.49 3br. d, CH3OMe)2), 3.80 3m,
SCHC2), 3.45 and 3.42 32£s, OCH3), 3.14 3m, SCH2); dC:
116.61, 116.56, 114.35, 114.26, 112.24, 112.21 3sp2-C),
104.82 3CH3OMe)2), 55.43 and 54.47 3OCH3), 47.93 and
47.88 3S-CHC2), 31.76 and 31.71 3SCH2); nmax: 1303,
4.4.2. 5-Methoxymethyl-5,6-dihydro-2-ꢀ50,60-dihydro-
1,3-dithiolo[4,5-b]-1,4-dithiin-20-ylidene)-1,3-dithiolo[4,5-
b]-1,4-dithiin, 6. From a 4:3 molar ratio of 23 and 36. Flash
chromatography 3hexane/dichloromethane 1:1) gave some
ET. Further elution 3hexane/dichloromethane 1:2) gave 6
31.44 g, 45%) as a red oil which solidi®ed on prolonged
drying in vacuo, mp 91±928C: dH: 3.79 31H, m, 5-H),
3.69 31H, dd, Jˆ9.5, 8.2 Hz, CHaOMe), 3.51 31H, dd,
Jˆ9.5, 5.6 Hz, CHbOMe), 3.38 33H, s, CH3), 3.28 34H, s,
50-,60-H2), 3.20 32H, d, Jˆ4.7 Hz, 6-H2); dC: 114.3, 113.7
and 113.4 33a-, 3a0-, 7a-, 7a0-C), 111.7 and 111.4 32-, 20-C),
73.5 3CH2OMe), 59.1 3CH3), 43.0 35-C), 32.1 36-C), 30.1
350-, 60-C); nmax 3CHCl3 solution): 3002, 2930, 2830, 1412,
1290, 1190, 1114, 960, 914 cm21; found C, 33.4; H, 2.8%.
C12H12OS8 requires C, 33.6; H, 2.8%; m/z 3EI): 428 3M1,
65), 400 320), 356 337), 236 3100%). Elution with dichloro-
methane gave a mixture of stereoisomers of bis33-methoxy-
propylene-1,2-dithio)tetrathiafulvalene 38 30.57 g, 33%),
mp 1178C, dH: 3.79 3m, C2CHS), 3.693m, CHaOMe), 3.51
3m, CHbOMe), 3.38 3OCH3), 3.20 3m, SCH2); dC: 114.3,
114.2, 113.4, 111.7, 111.7, 111.6 3sp2 C), 73.5 3CH2OMe),
59.1 3CH3), 43.0 3C2CHS), 32.1 3CH2S); nmax 3CHCl3 solu-
tion): 2998, 2932, 2830, 1452, 1410, 1382, 1318, 1206,
1114, 960, 914 cm21; m/z 3EI): 472 3M1, 30), 400 325),
236 338), 208 3100%).
1227, 1183, 1146, 1114, 1053, 965, 915, 769 cm21
;
HRMS: 3EI) found M1 531.9113, C16H20O4S8 requires
531.9127.
4.4.5. 5,6-Dihydro-5-ꢀ100,300-dioxolan-200-yl)-2-ꢀ50,60-di-
hydro-1,3-dithiolo[4,5-b]-1,4-dithiiin-20-ylidene)-1,3-
dithiolo-[4,5-b]-1,4-dithiin, 10. From an equimolar mixture
of 23 and 53. Flash chromatography 3hexane/dichloro-
methane 2:1) eluted some ET®rst. The second fraction
gave the desired cross coupled product 10 30.40 g, 36%)
as an orange-yellow solid, mp 128±1308C. dH: 5.11 31H,
d, Jˆ6.3 Hz, 200-H), 3.97 34H, m, 400-,500-H), 3.69 31H, m,
5-H), 3.29 34H, s, 50-,60-H2), 3.22 32H, m, 6-H2); dC: 116.8,
115.1 and 113.8 33a-, 3a0-, 7a-, 7a0-C), 111.8 32-,20-C),
103.9 3200-C), 65.7 and 65.5 3400-,500-C), 49.4 35-C), 31.6
36-C), 30.2 350-,60-C); nmax: 1288, 1240, 1123, 1029, 971,
903, 769 cm21; found C: 34.1, H: 2.8%. C13H12O2S8
requires C: 34.2, H: 2.7%. The ®nal band gave a mixture
of stereoisomers of bis33-31,3-dioxolan-2-yl)ethylene-1,2-
dithio)tetrathiafulvalene 55 30.41 g, 30%) as an orange
solid, mp 144±1468C. dH: 5.10 3d, Jˆ6.3 Hz, CHO2), 3.97
3m, OCH2CH2O), 3.68 3m, SCHC2), 3.17 m, SCH2); dC:
116.6 and 115.0 33a-,3a0-,7a-, 7a0-C), 112.2 32-,20-C),
103.8 3CHO2), 65.7 and 65.5 3OCH2CH2O), 49.3
3SCHC2), 31.6 3SCH2); nmax: 1125, 1108, 1059, 1024,
977, 938, 908, 771 cm21; HRMS: 3EI) found M1
527.8797, C16H16O4S8 requires 527.8814.
4.4.3. 5-Ethoxymethyl-5,6-dihydro-2-ꢀ50,60-dihydro-1,3-
dithiolo[4,5-b]-1,4-dithiin-20-ylidene)-1,3-dithiolo[4,5-b]-
1,4-dithiin, 7. From a 3:2 molar ratio of 23 and 37. Flash
chromatography 3hexane/dichloromethane 31:1)) afforded 7
as a brown/red solid 30.27 g, 34%): mp 73±758C: dH: 3.73
32H, m, 5-H and CHaOEt), 3.54 33H, m, OCH2Me and
5-CHbOEt), 3.29 34H, s, 50-, 60-H2), 3.20 32H, m, 6-H2),
1.19 33H, t, Jˆ6.3 Hz, CH3); dC: 114.4, 113.9 and 113.4
33a-,3a0-,7a-,7a0-C), 111.8 and 111.7 32-, 20-C), 71.5
3CH2OEt), 67.0 3OCH2Me), 43.3 35-C), 32.3 36-C), 30.2
350-, 60-C), 15.1 3CH3); nmax 3evaporated ®lm): 2970,
2868, 1408, 1374, 1288, 1110, 918, 772 cm21; found C,
35.2; H, 3.1%, C13H14S8O requires C, 35.3; H, 3.1%. A
further fraction yielded 39 30.11 g, 24%).
4.4.6. 6,6-Diꢀmethoxyethoxymethoxymethyl)-5,6-dihydro-
2-ꢀ50-dimethoxymethyl-50,60-dihydro-1,3-dithiolo[4,5-b]-
1,4-dithiiin-20-ylidene)-7H-1,3-dithiolo[4,5-b]-1,4-dithie-
pine, 61. From an equimolar mixture of 52 and 60. Flash
chromatography 3hexane/ethyl acetate 2:1) eluted some ET
®rst. The second fraction gave the cross coupled material 61
30.12 g, 31%) as an orange solid, mp 88±908C, dH: 4.66
34H, s, 2£OCH2O), 4.45 31H, d, Jˆ8.0 Hz, CH3OMe)2),
3.76 31H, m, 50-H), 3.68 34H, s, 2£CH2OMEM), 3.57
38H, m, 2£OCH2CH2O), 3.43 and 3.41 36H, 2£s,
CH3OCH3)2), 3.36 36H, s, 2£OCH3), 3.11 32H, m, 60-H2),
2.72 34H, s, 5- and 7-H2); dC: 128.4 33a-,8a-C), 115.5, 114.2
and 113.3 320-,3a0-,7a0-C), 108.9 32-C), 103.8 3CH3OMe)2),
94.7 32£OCH2O), 70.7 and 65.9 32£OCH2CH2O), 68.5
32£CH2OMEM), 58.0 32£OCH3), 54.4 and 53.5
3CH3OCH3)2), 46.9 350-C), 43.2 35-, 7-C), 36.0 36-C), 30.7
4.4.4. 5,6-Dihydro-5-dimethoxymethyl-2-ꢀ50,60-dihydro-
1,3-dithiolo[4,5-b]-1,4-dithiiin-20-ylidene)-1,3-dithiolo-
[4,5-b]-1,4-dithiin, 9. From an equimolar mixture of oxo
compounds 23 and 52. Flash chromatography 3hexane/

N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
5025
360-C); nmax: 1114, 1061, 1039, 984, 960, 897, 846 cm21
;
dimethoxybutan-2,3-diol 31.20 g, 8.0 mmol), prepared by
literature procedures,21 and dry pyridine 31.3 ml) in
anhydrous diethyl ether 325 ml) was stirred at 08C and
treated with thionyl chloride 31.00 g, 8.4 mmol). After stir-
ring for 3 h, the mixture was ®ltered and washed with water
32£30 ml). The organic extracts were dried over Na2SO4
and distillation gave 4S,5S-5-di3methoxymethyl)-1,3,2-
dioxathiolane-2-oxide 41 as a colourless oil 31.28 g, 82%),
bp 1008C at 0.03 mmHg, dH: 4.93 31H, m, 4-H), 4.51 31H,
m, 5-H), 3.76 and 3.66 34H, 2£m, 2£CH2OMe), 3.45 and
3.41 36H, 2£s, 2£OCH3). This product 31.10 g, 4.6 mmol)
was dissolved in dichloromethane 330 ml), ruthenium
dioxide 320 mg) added, and the mixture vigorously stirrred
with a solution of sodium periodate 32.10 g. 9.8 mmol) in
water 315 ml). The solution turned from brown to green
sharply after 20 min. After a further 5 min the organic
layer was collected, stirred with isopropanol 31 ml) for
15 min, dried over Na2SO4 and ®ltered through Celite.
After evaporation of solvent, distillation of the residue
gave 42 as a colourless oil 31.01 g, 84%), bp 1508C at
0.02 mm Hg, found C: 34.3, H: 6.1%. C6H12O6S requires
C: 34.0, H: 5.7%. dH: 4.92 32H, m, 4-,5-H), 3.71 34H, m,
2£CH2OMe), 3.41 36H, s, 2£OCH3).
HRMS: 3EI) found M1 708.0179, C24H36O8S8 requires
708.0176.
4.4.7. 6,6-Diꢀmethoxyethoxymethoxymethyl)-5,6-dihydro-
2-ꢀ50-ꢀ100300-dioxolan-200-yl)-50,60-dihydro-1,3-dithiolo[4,5-
b]-1,4-dithiiin-20-ylidene)-7H-1,3-dithiolo[4,5-b]-1,4-di-
thiepine, 62. From an equimolar mixture of 53 and 60.
Flash chromatography 3hexane/ethyl acetate 2:3) eluted
some ET®rst. The second fraction gave the cross coupled
material 62 30.14 g, 37%) as an orange oil, dH: 5.10 31H, d,
Jˆ6.3 Hz, 200-H), 4.70 34H, s, 2£OCH2O), 4.98 34H, 2£m,
400-, 500-H2), 3.91 31H, m, 50-H), 3.71 34H, s,
2£CH2OMEM), 3.61 38H, 2£m, 2£OCH2CH2O), 3.37
36H, s, 2£OCH3), 3.18 32H, m, 60-H2), 2.75 34H, s, 5- and
7-H2); dC: 129.3 33a-,8a-C), 116.5, 115.2 and 114.8 320-,3a0-,
7a0-C), 109.8 32-C), 103.6 3200-C), 95.6 32£OCH2O), 71.6
and 66.8 32£OCH2CH2O), 69.5 32£CH2OMEM), 65.5 and
65.4 3400-,500-C), 58.9 32£OCH3), 49.2 350-C), 44.1 35-, 7-C),
36.9 36-C), 31.5 360-C); nmax: 1302, 1250, 1199, 1115, 1041,
974, 898, 848, 752, 664, 544 cm21; HRMS: 3EI) found M1
706.0021, C24H34O8S8 requires 706.0019.
4.4.8. Preparation of 5,6-dihydro-2-ꢀ50,60-dihydro-1,3-
dithiolo[4,5-b]-1,4-dithiin-20-ylidene)-1,3-dithiolo[4,5-b]-
1,4-dithiin-5-methanol, ꢀ^) 2 .Hydrochloric acid 318 ml,
20%) was added dropwise to a solution of 24 30.20 g,
0.31 mmol) in THF 330 ml) under nitrogen and stirred for
24 h. After neutralisation with sodium hydrogen carbonate,
the organic phase was separated, dried over Na2SO4, and
evaporated. The residue was puri®ed by chromatography on
silica eluting with dichloromethane to give racemic HMET
2 30.098 g, 75%) as a light orange solid; mp 1518C 3from
ethanol): dH: 3.74 33H, m, CH2OH and 5-H), 3.32 34H, s, 50-,
60-H2), 3.30 31H, dd, Jˆ13.5, 5.0 Hz, 6-Ha), 3.22 31H, dd,
Jˆ13.5, 3.4 Hz, 6-Hb), 1.58 31H, br, s, OH); dC: 114.5,
113.5, 113.0 33a-,3a0-,7a-,7a0-C), 111.2 and 111.1 32-,20-
C), 63.9 3CH2OH), 45.5 35-C), 31.7 36-C), 30.1 350-,
4.4.11. Preparation of 5R,6R,-5,6-dihydro-5-,6-di-
ꢀmethoxymethyl)-1,3-dithiolo[4,5-b]-1,4-dithiin-2-thione,
43. Cyclic sulfate ester 42 30.95 g, 4.5 mmol) was added to a
methanol solution 320 ml) of the disodium salt of dithiolate
4 3generated in situ by treatment of a 4,5-di3benzoylthio)-
1,3-dithiole-2-thione 31.95 g, 4.8 mmol) with two equiva-
lents of sodium methoxide) at 08C under nitrogen and left
to warm up to room temperature over 12 h. The solvent
was evaporated in vacuo and replaced by dry THF
320 ml) and the mixture re¯uxed for 4 h. The THF
was evaporated, the residue partitioned between
dichloromethane and water, and the organic layer separated
and dried over MgSO4. After evaporation of the solvent,
methyl benzoate was removed by distillation in vacuo,
and the residue puri®ed by chromatography 3hexane/
dichloromethane 1:1) to give the product as a yellow solid
371 mg, 5%), mp 67±688C, dH 3.65 34H, m, 2£CH2OMe),
3.60 32H, m, 5-,6-H), 3.40 36H, s, 2£OCH3); m/z: 3EI)
312 3M1, 54), 196 310), 120 318), 115 324), 76 324), 45
3100%).
60-C); nmax: 3400, 2860, 1405, 1260, 1020 and 802 cm21
;
found C, 32.0; H, 2.6%. C11H10S8O requires C, 31.9; H,
2.4%; m/z 3CI): 415 3[M1H]1, 40), 385 348), 207 3100),
151 375%).
4.4.9. Radical cation salts of HMET, 22 BF4, 22Cl, 22PF6.
Radical cation salts were prepared by constant current
electrocrystallisation of dichloromethane solutions 350 ml)
containing 2 310 mg) and the appropriate tetrabutyl-
ammonium salt 3100 mg), at a current ¯ow of 1 mA.
4.4.12. Preparation of 5R,6R,50R,60R-5,6-dihydro-2-
ꢀ50,60-dihydro-50,60-diꢀmethoxy-methyl)-1,3-dithiolo-
[4,5-b]1,4-dithiin-20-ylidene)-5,6-diꢀmethoxymethyl)-
1,3-dithiolo[4,5-b]1,4-dithiin, 8. Thione 43 355 mg,
0.18 mmol) was reacted with mercuric acetate 365 mg,
0.20 mmol) in chloroform 310 ml) and acetic acid 310 ml)
by the general procedure. The crude oxo product 44 was
heated with triethyl phosphite 35 ml) for 3 h. under nitrogen.
After distillation of triethyl phosphite in vacuo, chromato-
graphy 3hexane/ethyl acetate 1:1) of the residue gave the
product 8 321 mg, 43%) as an orange-red solid, mp 106±
1088C. dH: 3.68 38H, m, 4£CH2OMe), 3.52 34H, m, 5-,50-,6-,
60-CH), 3.37 312H, s, 4£OCH3); dC: 111.1 3br, 2-,20-,3a-,
3a0-,7a-,7a0-C), 73.9 34£CH2OMe), 59.2 34£OCH3), 41.9
35-,50-,6-,60-C); m/z: 3EI) 560 3M1, 100), 444
3[M23CH3OCH2CH),]1, 85), 300 345), 280 367), HRMS:
3EI) found M1 559.9431, C18H24O4S8 requires 559.9440;
22´BF4: Raman n4: 1464.0 cm21; found C, 29.1; H, 2.2; S,
56.4; F, 8.1%. C22H20O2S16BF4 requires C, 28.8; H, 2.2; S,
56.0; F 8.3%.
22Cl: Raman n4: 1466.7 cm21; found C, 30.6; H, 2.4; Cl,
4.2%. C22H20O2S16Cl requires C, 30.6; H, 2.3; Cl, 4.1%
22PF6: IR nmax 3KBr) 3436, 2919, 2837, 2355, 1731, 1625,
;
1414, 1335, 1267, 1173, 1120, 1079, 843, 668, 556 cm21
Raman n3: 1501.9, n4: 1464.0, cm21; found C, 27.6; H, 2.0;
F, 11.0%. C22H20O2S16PF6 requires C, 27.1; H, 2.1; F 11.7%.
4.4.10. Preparation of 4S,5S-5-Diꢀmethoxymethyl)-1,3,2-
dioxathiolane-2,2-dioxide, 42. A solution of 4S,5S-1,4-
293
[a]D ˆ11200 3cˆ0.05, dichloromethane).

5026
N. Saygili et al. / Tetrahedron 57 22001) 5015±5026
Auban-Senzier, P.; Jerome, D.; Batail, P. Adv. Mater. 1992,
Â
4, 579±581. 3b) Blanchard, P.; Salle, M.; Duguay, G.; Jubault,
Â
Acknowledgements
M.; Gorgues, A. Tetrahedron Lett. 1992, 33, 2685±2688.
12. Marshallsay, G. J.; Bryce, M. R.; Cooke, G.; Jorgenson, T.;
Becher, J.; Reynolds, C. D.; Wood, S. Tetrahedron 1993, 49,
6849±6862.
We should like to thank the EPSRC Mass Spectrometry
Service for data, the EPSRC Chemical Data Service27 and
the EPSRC for a grant 3GR/F/86021) and a studentship
3R. J. B.). We thank Dr F. Turksoy of the Marmara Research
Centre, Turkey for two cyclic voltammetry measurements,
and we thank Professor Robin Clark of the Chemistry Dept,
University College London for access to the Ramascope and
Dr Steven Firth for assistance with the measurements.
13. Ozturk, T.; Saygili, N.; Ozkara, S.; Pilkington, M.; Rice, C. R.;
Tranter, D. A.; Turksoy, F.; Wallis, J. D. J. Chem. Soc., Perkin
Trans. 1 2001, 407±414.
14. Horley, G. A.; Ozturk, T.; Turksoy, F.; Wallis, J. D. J. Chem.
Soc., Perkin Trans. 1 1998, 3225±3231.
15. Wang, C.; Batsanov, A. S.; Bryce, M. R.; Howard, J. A. K.
Synthesis 1998, 1615±1618.
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