An adventitious synthesis of 2,2′-dipyrryl disulfides

Article abstract of DOI:10.1071/C98112

Condensation of 1,2-diketones and a cyanothioacetamide gave hydroxy thiolactams which failed to give the expected 3-cyano methylene thiolactams on dehydration. Disulfides and a thiosulfonate were obtained from the dehydrations. A possible mechanism for th

Full text of DOI:10.1071/C98112

C S I R O P U B L I S H I N G
Australian Journal
of Chemistry
Volume 52, 1999
© CSIRO Australia 1999
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Aust. J. Chem., 1999, 52, 63–67
.
Short Communications
An Adventitious Synthesis of
2,20-Dipyrryl Disul des
Raju Adhikari,A Dionne Jones,A Andris J. LiepaA,B
and Maureen F. MackayC
A
CSIRO Molecular Science, Private Bag 10, Clayton South MDC, Vic. 3169.
Author to whom correspondence should be addressed.
School of Chemistry, La Trobe University, Bundoora, Vic. 3083.
B
C
Condensation of 1,2-diketones and a cyanothioacetamide gave hydroxy thiolactams which failed to
give the expected 3-cyano methylene thiolactams on dehydration. Disul des and a thiosulfonate were
obtained from the dehydrations. A possible mechanism for their formation is proposed. The crystal
structure of the disul de 4,40,5,50-tetramethyl-1,10-diphenyl-2,20-disulfanediyldi-1H -pyrrole-3-carbonitrile
(9) has been determined by X-ray di raction.
Introduction
sequence, commencing with a cyanothioacetamide (2;
X = S) in place of a cyanoacetamide (2; X = O),
could provide the required methylene thiolactam (4;
R = aryl, X = S).
A diverse array of biological activity is associated1
with , -unsaturated lactones, hence analogous unsatu-
rated lactams were envisaged as less common structures
which might also have the potential for biological activ-
ity.
Results and Discussion
Accordingly, 2-cyano-N -phenylthioacetamide (2;
R = Ph, X = S) was prepared by a literature procedure6
(with some minor modi cations). Condensation of (2;
R = Ph, X = S) with butane-2,3-dione readily gave the
previously unknown hydroxy thiolactam (7) (Scheme 2)
in 54% yield and base-catalysed (morpholine) conden-
sation with cyclohexane-1,2-dione gave the ring-fused
analogue (8) in 40% yield. These compounds were
characterized by the usual spectroscopic methods and
elemental analyses. Notwithstanding the successful
analogy to this point with the known lactam prepa-
ration, attempts to dehydrate either of these hydroxy
thiolactams under a variety of conditions failed to give
the desired methylene thiolactams. Instead, several
unexpected products were obtained.
Although compounds incorporating
a 3-cyano-
substituted methylene lactam (4; R1/R2 = various
groups, X = O) have been described,2,3 neither the
synthesis nor the biological properties of related methy-
lene thiolactams (4; X = S) have been reported. Con-
sequently, such sulfur analogues present a synthetic
target of interest in their own right as well as o ering
molecules with unexplored biological activity.
Formic acid had been found5 to be a convenient
dehydrating agent for converting hydroxy lactams (3;
X = O) into methylene lactams (4; X = O). However,
an attempted dehydration of the hydroxy thiolactam
(7) by heating in formic acid did not give the expected
analogous product. Instead, the reaction produced
a complex mixture from which an orange crystalline
material was separated as the only major component
in 16% yield. The proton n.m.r. spectrum of this com-
pound was disarmingly simple and included singlets at
2 30 and 2 06, as well as absorption due to aromatic
protons, resonances which integrated in the relative
ratio of 3 : 3 : 5. However, this product was clearly
not the expected methylene lactam. The spectroscopic
The inspiration for a plausible pathway to these
compounds was provided by a convenient procedure
reported for the preparation of simple hydroxy lactams
(3; R1 = alkyl, R2 = H or alkyl, X = O). Such com-
pounds form readily as the result of a condensation
between 2-cyanoacetamide (2; R = H, X = O) and
1,2-diketones (1)4 (Scheme 1). Further, it was found5
that under acidic conditions, dehydration of analogous
N -aryl-substituted intermediates (3; R = aryl, X = O)
gives rise to methylene lactams (4; R = aryl, X = O).
Consequently, it was envisaged that a similar reaction
Manuscript received 24 June 1998
᭧ CSIRO 1999
0004-9425/99/010063$ 05.00
10.1071/CH98112

64
Short Communications
evidence suggested the possibility that the elimination
of a molecule of water from (3; R1 = CH3, R2 = H,
X = S) combined with some reductive process might
have given rise to either a pyrrole (5) or a thiophen
(6), although neither an SH nor an NH resonance was
evident.
to form the observed disul de products (9) and (10)
(Scheme 2).
Since such possible alternatives could not be con-
veniently distinguished by spectroscopic means, the
material was subjected to analysis by X-ray crystal-
lography. Surprisingly, the product (9) (Scheme 2)
was in fact found to be a pyrrole disul de. Similarly,
reaction of the hydroxy thiolactam (8) with formic acid
at room temperature was found to form the analogous
tetrahydroindole disul de (10) in 27% yield.
Formation of these products from the hydroxy thi-
olactam may be rationalized as follows. It appears
that under the acidic reaction conditions the alcohol
(3) becomes protonated and subsequently eliminates
water to give a sulfenylium ion. This could be reduced
by formic acid to a transient pyrrolethiol (5) (Scheme
3) which could readily undergo oxidative dimerization
Reduction of the hydroxy lactams in the presence of
formic acid to give the dimeric products is not excep-
tional as the acid is known to act as a reducing agent
under certain conditions.7 Moreover, in the reaction of
(7) with formic acid, prior addition of 2-mercapto-1-
methylimidazole considerably enhanced the formation
of the pyrrole giving (9) in greater than 59% yield, this
combination presumably acting as a superior reducing
agent; however, no unsymmetrical disul de product
was isolated. On the other hand, these dimeric pyrroles
were also isolated when dehydration was attempted
under conditions which did not include the presence
of a recognizable reductant.
Phosphorus oxychloride–pyridine is a useful com-
bination for generating exocyclic double bonds from
cyclic tertiary alcohols.8,9 When the e ect of this
reagent upon (8) was investigated, the tetrahydroin-
dole disul de (10) was again isolated in 36% yield as
well as the thiosulfonate (11) in 15% yield. These
products can be accounted for by postulating the
formation of a sulfenyl chloride (12) (Scheme 3) as
an intermediate followed by hydrolysis during workup
to the corresponding sulfenic acid. Such acids are
known10 to readily disproportionate to give disul des
and thiosulfonates, accounting for the simultaneous
formation of (10) and (11).
Testing of these compounds for potential as crop
protection chemicals failed to reveal any signi cant
activity.
Experimental
Melting points were determined on a Reichert Ko er hot-
stage micro melting point apparatus and are uncorrected.
Microanalyses were performed by the National Analytical
Laboratory, Melbourne. Infrared spectra were recorded on
a Perkin Elmer 842 spectrophotometer (cm 1) and refer to
para n mulls. 1H and 13C n.m.r. spectra were recorded at 200
and 50 3 MHz respectively on a Bruker AC-200 spectrometer,
or at 500 and 125 7 MHz on a Bruker AM 500 instrument.
Chemical shifts ( ) are measured in ppm with tetramethylsilane

Short Communications
65
as an internal standard. The 15N n.m.r. spectrum was recorded
at 50 7 MHz on a Bruker AM 500 instrument without nuclear
Overhauser e ect in CDCl3 at 305 K with nitromethane as
external standard and is uncorrected for susceptibility. Positive
values of 15N denote absorption at higher frequencies than
the standard. High- and low-resolution chemical ionization
(c.i.) mass spectra and fast atom bombardment (f.a.b.) mass
spectra were obtained on a Jeol JMS-DX303 mass spectrometer,
with the M+1 ion (if observed) and principal ion peaks with
intensity >10% reported.
give an orange foam (638 mg). Radial chromatography on silica
(commencing with CH2Cl2/light petroleum (1 : 1) and progress-
ing to CH2Cl2) gave (9) as the major product as a yellow foam
(119 mg). Crystallization from CH2Cl2/light petroleum gave
(9) as orange crystals (108 mg, 16%), m.p. 184–186 (Found:
C, 68 6; H, 4 9; N, 12 0; S, 14 3. C26H22N4S2 requires C,
68 7; H, 4 9; N, 12 3; S, 14 1%).
1554w, 1491m, 1270w, 1169w, 760w, 696w cm
(Nujol) 2220m, 1595w,
1
max
.
1H n.m.r.
(200 MHz, CDCl3) 7 47–7 26, m, 10 aromatic H; 2 30, s,
CH3; 2 06, s, 2 CH3. 13C n.m.r. (CDCl3) 136 8; 135 6;
2
Analytical thin-layer chromatography was performed on
polyester-backed plates precoated with silica gel 60 (SIL
G/UV254). Radial thin-layer chromatography was performed
on a Harrison Research Chromatron (7924T) with 4-mm thick
silica plates (silica gel 60 PF254, Merck No. 7749). Light
petroleum refers to the fraction with a b.p. of 40–60 .
128 9; 128 7; 123 8; 120 0; 114 6; 107 6; 11 5; 10 2. Mass
spectrum: m/z 259 (10%), 257 (11), 230 (17), 229 (100), 228
(43), 227 (54).
(B) To a mixture of (7) (500 mg, 2 1 mmol) and 2-mercapto-
1-methylimidazole (480 mg, 4 2 mmol) was added formic acid
(10 ml) and the mixture was stirred at room temperature for
4 h. The orange solution was diluted slowly with water and
the precipitate collected by ltration, washed with water and
dried in air to give (9) as an orange-yellow solid (283 mg, 59%),
m.p. 180–183 . The 1H n.m.r. spectrum of the product was
identical with the material described above. An additional
impure sample of (9) (149 mg) was obtained by extracting the
ltrate as in (A) above.
2-Cyano-N -phenylethanethioamide (2; R = Ph, X = S)
To a stirred solution of sodium ethoxide [prepared from
sodium (7 8 g, 0 34 mol) and dry ethanol (200 ml)] at 5–10
(internal temperature) under argon was added ethyl cyanoac-
etate (39 0 g, 0 34 mol) dropwise. On completion of the
addition, phenyl isothiocyanate (46 0 g, 0 34 mol) was added
dropwise whilst maintaining the temperature between 5–10 .
The reaction mixture was re uxed for 2 h, cooled in ice–
water and a solution of sodium hydroxide (136 g, 3 4 mol) in
water (450 ml) added. The reaction mixture was then left
overnight and heated to re ux for 2 h. The solution was
cooled to room temperature, extracted with ether, chilled and
carefully acidi ed with concentrated hydrochloric acid. The
precipitated yellow solid was collected by ltration, washed
with water and dried under vacuum yielding 58 6 g (98%) of
(2; R = Ph, X = S), m.p. 104–106 (lit.6 111 ). 1H n.m.r.
(200 MHz, CDCl3/(CD3)2SO) 11 37, br s, NH; 7 67–7 63, m,
2H; 7 33–7 11, m, 3H; 3 91, s, 2H.
7a-Hydroxy-1-phenyl-2-thioxo-2,4,5,6,7,7a-hexahydro-1H -
indole-3-carbonitrile (8)
To a stirred, cooled (ice) solution of (2; R = Ph, X = S)
(2 0 g, 11 4 mmol) in dimethylformamide (10 ml) were added
cyclohexane-1,2-dione (1 4 g, 12 5 mmol) and a few drops of
morpholine. The reaction mixture was allowed to warm to
room temperature overnight, diluted with water (30 ml) and
extracted with dichloromethane (3 30 ml). The combined
extracts were washed with water (3 50 ml), dried (MgSO4)
and evaporated under vacuum to give a brown viscous oil
(2 5 g). Radial chromatography on silica (commencing with
ethyl acetate/light petroleum (1 : 4) and progressing to 1 : 1)
and subsequent trituration of the product with dichloromethane
a orded (8) as a bright yellow solid (1 2 g, 40%), m.p. 176–
5-Hydroxy-4,5-dimethyl-1-phenyl-2-thioxo-2,5-dihydro-1H -
pyrrole-3-carbonitrile (7)
178 (Found: MH+ , 271 0895. C15H14N2OS requires MH+
271 0827). (Nujol) 3394s, 2240m (CN), 1634m, 1592w,
1495w, 14045s, 1313m, 1294m, 1259w, 1175w, 1119w, 1086w,
,
To a stirred, cooled (ice–water) solution of (2) (2 0 g,
11 4 mmol) in dimethylformamide (10 ml) was added butane-
2,3-dione (1 0 g, 11 6 mmol) dropwise. The reaction mixture
was left in the bath for 30 min, allowed to warm to room
temperature and diluted with water. The resulting solution was
extracted with ether, and the combined extracts were washed
with water, dried (MgSO4) and evaporated under vacuum to
give (7) (2 4 g). Crystallization from dichloromethane/light
petroleum gave a bright yellow crystalline solid (1 5 g, 54%),
m.p. 175–177 . An analytical sample was obtained by drying in
the presence of P2O5 under vacuum at 40 for 2 days (Found:
C, 63 9; H, 5 0; N, 11 1; S, 13 4. C13H12N2OS requires C,
max
1
1066w, 1011w, 699m cm
.
1H n.m.r.
(200 MHz, CDCl3)
7 54–7 28, m, 5 aromatic H; 3 60, br s, OH (D2O); 3 13–2 95,
m, 1H; 2 81–2 58, m, 1H; 2 30–2 10, m, 2H; 1 80–1 35, m,
4H. 13C n.m.r.
(CDCl3/(CD3)2SO) 188 9; 172 0; 136 1;
129 2; 128 5; 125 9; 112 2; 112 1; 96 5; 37 9; 27 9; 27 0;
21 0. Mass spectrum: m/z 271 (M+1, 100%), 245 (10).
1,10-Diphenyl-4,405,50,6,60,7,70-octahydro-2,20-disulfanediyldi-
1H -indole-3-carbonitrile (10)
A stirred solution of (8) (700 mg, 2 6 mmol) in formic acid
(20 ml) was left at room temperature for 20 h. The reaction
mixture was diluted with cold water (40 ml) and the precip-
itate collected by ltration and washed with water to give a
yellow solid (530 mg). The ltrate, on extraction with ether,
was found by thin-layer chromatography (silica; CH2Cl2/light
petroleum (1 : 2)) to contain unreacted (8). Radial chromatogra-
phy on silica (commencing with CH2Cl2/light petroleum (1 : 8)
and progressing to 1 : 4) gave (10) as a yellow solid (232 mg).
Recrystallization from dichloromethane/ethanol gave an orange
63 9; H, 5 0; N, 11 5; S, 13 1%).
(CN), 1636m, 1594w, 1589w, 1488m, 1419s, 1299s, 1166m,
1117w, 1097w, 1007w, 965w, 825w, 755w cm
(500 MHz, CDCl3) 7 57–7 30, m, 5 aromatic H; 3 80, s, OH;
2 36, s, CH3; 1 48, s, CH3. 13C n.m.r.
(CDCl3) 188 7;
168 8; 135 8; 129 5; 129 2; 128 9; 116 3; 112 3; 98 1; 22 0;
13 2. 15N n.m.r. (CDCl3) 112 3, CN; 194 9, NCS. Mass
spectrum: m/z 245 (M+1, 100%), 229 (20), 227 (25).
(Nujol) 3402s, 2239m
max
.
1H n.m.r.
1
4,40,5,50-Tetramethyl-1,10-diphenyl-2,20-disulfanediyldi-1H-
pyrrole-3-carbonitrile (9)
crystalline solid (180 mg, 27%), m.p. 227–228 (Found: MH+
,
507 1589.
(Nujol) 2216m, 1595w, 1550w, 1496m, 761m, 704m cm
n.m.r.
C
30H27N4S2 requires MH+ , 507 1599).
max
1H
1
(A) A stirred solution of (7) (700 mg, 2 9 mmol) in formic
acid (5 ml) was left at room temperature for 30 min and then
gently warmed at 60 for a few minutes. After cooling, the
reaction mixture was diluted with water (10 ml) and extracted
with ether. The combined extracts were washed with water
(3 50 ml), dried (MgSO4) and evaporated under vacuum to
.
(200 MHz, CDCl3) 7 63–7 13, m, 10 aromatic H;
2 78–2 47, m, 4H; 2 41, br s, 4H; 2 06–1 69, m, 8H. 13C
n.m.r. (CDCl3) 138 5; 136 3; 128 9; 128 4; 124 1; 122 5;
114 4; 106 0; 23 2, 22 7, 21 9, 8 CH2. Mass spectrum: m/z
507 (M+1, 10%), 283 (21), 255 (100), 253 (40).

66
Short Communications
Reaction of (8) with Phosphorus Oxychloride to Give (10)
and S-(3-Cyano-1-phenyl-4,5,6,7-tetrahydro-1H -indol-
2-yl) 3-Cyano-1-phenyl-4,5,6,7-tetrahydro-1H -indole-2-
thiosulfonate (11)
for which I > 3 (I ) considered observed. The non-hydrogen
atoms were re ned with anisotropic temperature factors; the
positional coordinates of the C 7 and C 70 methyl hydrogen
atoms were calculated and all other hydrogen-atom coordinates
re ned, the atoms being given isotropic temperature factors.
The function minimized in the re nement was w(Fo Fc)2,
Phosphorus oxychloride (2 4 g, 15 5 mmol) was added drop-
wise to a stirred, cooled solution of (8) (500 mg, 1 8 mmol) in
pyridine (5 ml). After 5 min, the reaction mixture was removed
from the cooling bath and left stirring at room temperature
for 1 5 h. The reaction mixture was then carefully poured into
ice/water (50 ml) with stirring. Attempted extraction of the
resulting solution with ether (20 ml) produced a precipitate
which was collected by ltration and washed with water and a
small quantity of ether to give a yellow solid (230 mg). Thin-
layer chromatography (silica; CH2Cl2/light petroleum (1 : 2))
of the solid indicated that a mixture containing two compounds
had been isolated. The combined ltrate and washings were
extracted by the addition of dichloromethane/ether (20 ml,
1 : 1). The organic phase was separated, washed with satu-
rated sodium bicarbonate (2 50 ml), water (2 50 ml), dried
(MgSO4), and evaporated under vacuum to give more of the mix-
ture isolated previously as a yellow solid (192 mg). The isolated
solids were combined and subjected to radial chromatography
on silica (commencing with CH2Cl2/petroleum ether (1 : 2)
and progressing to 2 : 1). Subsequent recrystallization from
dichloromethane/ethanol gave (10) as orange crystals (165 mg,
36%), m.p. 226–228 (dec). Compound (11) was obtained as
the second component of the mixture after chromatography.
Recrystallization from dichloromethane/ethanol gave (11) as
2
1
with w = [ 2(F)+0 0052F
]
. At convergence the conven-
tional reliability indices for the observed data were R 0 043
and wR 0 070 with S 0 907 (362 variables). The maximum and
minimum residual electron-density peak heights were +0 24
3
and 0 19 e A
. An extinction parameter was applied to
the Fc terms with SHELX-76;11 the extinction coe cient was
1 30(7) 10 6. Final atomic parameters are given in Table 1;†
Fig. 1 was prepared from the output of ORTEP-II13 and shows
the atomic labelling scheme used.
Table 1. Final atomic coordinates and equivalent isotropic
temperature factors for C26H22N4S2 (9)
Values for C and N have been multiplied by 104; values for S
have been multiplied by 105. Estimated standard deviations
are in parentheses. Beq = (8 2/3)
jai*aj*ai.aj
i
Atom
x
y
z
Beq (A)2
N(1)
C(2)
C(3)
C(4)
C(5)
S(1)
N(2)
C(6)
9425(2)
8385(2)
8056(2)
8888(2)
9722(2)
76480(6)
6223(3)
7037(3)
8845(3)
10801(3)
10058(2)
10384(3)
11009(3)
11307(3)
10977(4)
10367(3)
5339(2)
6334(2)
6705(2)
5930(3)
5096(3)
70130(6)
8556(3)
7728(3)
6021(4)
4072(3)
4660(2)
4481(3)
3797(4)
3328(3)
3512(3)
4192(3)
1564(2)
1233(3)
594(3)
4154(1)
4133(2)
3435(2)
3019(2)
3473(2)
48041(5)
2972(2)
3189(2)
2221(2)
3332(3)
4758(2)
4559(2)
5141(3)
5906(3)
6105(3)
5526(2)
3192(1)
3374(2)
2667(2)
2053(2)
2397(2)
43102(5)
2545(3)
2606(2)
1200(2)
2027(3)
3746(2)
4029(3)
4559(3)
4801(3)
4513(3)
3991(2)
3 11(6)
3 09(6)
3 43(7)
3 79(8)
3 50(7)
3 72(2)
6 43(1)
4 22(8)
5 83(1)
5 37(11)
3 23(7)
4 08(9)
5 03(10)
5 76(12)
6 49(10)
4 93(10)
3 37(6)
3 20(7)
3 52(7)
3 93(8)
3 69(7)
3 76(2)
6 58(11)
4 30(9)
5 98(12)
5 30(11)
3 62(7)
4 99(10)
6 44(14)
6 11(12)
6 24(13)
4 88(10)
528(3)
1139(3)
16927(7)
359(3)
yellow crystals (70 mg, 15%), m.p. 176–179 (Found: MH+
,
68(3)
48(4)
C
30H27N4O2S2 requires MH+ , 538 1497).
C(7)
C(8)
C(9)
538 1482.
max
1310(5)
2278(3)
3395(3)
4084(4)
3662(4)
2552(4)
1851(4)
2467(2)
2967(3)
2948(3)
2448(3)
2150(3)
33629(7)
3626(4)
3347(3)
2243(5)
1584(5)
2335(3)
1231(4)
1116(5)
2088(6)
3208(5)
3341(4)
(Nujol) 2220w (CN), 1597w, 1560w, 1496m, 1342m, 1129m,
785w, 703m. 1H n.m.r. (200 MHz, CDCl3) 8 00–6 86, m,
10 aromatic H; 2 91–1 60, m, 8 CH2. 13C n.m.r. (CDCl3)
140 6; 139 8; 135 4; 134 9; 129 8, 129 1, 128 9, 10 aromatic
C; 124 1; 123 9; 114 4; 112 2; 105 7; 104 3, 23 2, 22 4,
21 9, 21 7, 8 CH2. The sample was not stable to c.i. mass
spectrometric analysis. F.a.b. m/z 539 (M+H, 8%), 524 (14),
507 (22), 378 (13), 304 (15), 269 (51), 263 (100), 223 (24).
C(10)
C(11)
C(12)
C(13)
C(14)
N(10)
C(20)
C(30)
C(40)
C(50)
S(10)
N(20)
C(60)
C(70)
C(80)
C(90)
C(100)
C(110)
C(120)
C(130)
C(140)
Crystallography
Crystal Data for (9)
C
c 17 082(2) A,
26H22N4S2, M 454 6, monoclinic, a 12 992(2), b 11 172(1),
102 15(1) ,
V
2423 9(8) A3, Dc(Z = 4)
1
1 246 g cm 3, F (000) 1056, (Cu K ) 21 4 cm
group P 21/c.
.
Space
Accurate cell dimensions were determined at 291(2) K by
least-squares re nement of 25 automatically centred re ec-
tions in the range 36 < 2 < 68 , measured with Cu K
(graphite-monochromatized) radiation ( 1 5418 A).
Description of the Structure of 4,4 0,5,5 0-Tetramethyl-1,1 0-
diphenyl-2,2 0-disulfanediyldi-1 H-pyrrole-3-carbonitrile (9)
Structure Determination
The molecule has approximate twofold symmetry and the
torsion angles N(1)–C(2)–S(1)–S(10) of 85 6(3) and N(10)–
C(20)–S(10)–S(1) of 80 5(3) show that the S–S bridge is
approximately orthogonal to the pyrrole rings, while the C(2)–
S(1)–S(10)–C(20) torsion angle of 58 4(2) illustrates the twist
about the S–S bond. The pyrrole and phenyl rings are planar
to within experimental error and their relative orientations
are given by the torsion angles C(2)–N(1)–C(9)–C(14) and
C(20)–N(10)–C(90)–C(140) of 67 2(4) and 71 7(4) respectively.
The S(1)–S(10) bond distance of 2 140(1) A is signi cantly
longer than that usually observed for the S–S bond while
the C(2)–S(1) and C(20)–S(10) bond lengths of 1 720(4) and
Intensity data were measured with Cu K radiation from a
cleaved specimen of dimensions c. 0 128 by 0 180 by 0 305 mm
aligned on a Rigaku-AFC four-circle di ractometer, recorded
by an ω–2 scan with 2 scan rate 2 0 min 1, and 10-
s stationary background counts. Three reference re ections
monitored every 100 re ections showed no decay. Data to a
2
130 yielded 4074 unique terms; corrections for Lorentz
max
and polarization e ects were applied; analytical absorption
corrections were made with SHELX-7611 (transmission factors
0 659–0 802). The structure was solved by direct methods with
SHELXS-8612 and the least-squares re nements were carried out
with SHELX-7611 on a VAX8800 computer with the 2792 terms
2
2
R = ||Fo| |Fc||/ |Fo|, wR = ( w||Fo| |Fc|| / w|Fo| )1/2
.
† Crystallographic data for compound (9), namely tables of structure factor amplitudes, bond distances and angles, anisotropic
thermal parameters and hydrogen atom parameters, have been deposited. Copies can be obtained from the Australian Journal
of Chemistry (until 31 December 2004), P.O. Box 1139, Collingwood, Vic. 3066.

Short Communications
67
Acknowledgments
We thank E. I. DuPont de Nemours and Co.,
Agricultural Products Department, for the evaluation
of fungicidal activity. We also thank Mr I. Vit for
measurement of mass spectra and Mr R. I. Willing
for measurement of 1H and 15N n.m.r. spectra.
References
1
Davidson, B. S., Chem. Rev., 1993, 93, 1771; Hopper, A.
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Appl. US 5,283,165 (Cl. 430–522; G03C1/84), 01 February
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3
Fallert, M., and Hartke, K., Arch. Pharm. (Weinheim,
Ger.), 1986, 319, 1098 (Chem. Abstr., 1987, 106, 102014g).
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Liepa, A. J., unpublished data.
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Paquette, L. A., ‘Encyclopedia of Reagents for Organic
4
5
Fig. 1. Perspective view and atom labelling of the structure
of (9). Thermal ellipsoids are at the 50% probability level.
Hydrogen atoms are denoted by spheres of arbitrary radius.
6
7
1 714(3) A are signi cantly shorter than values tabulated by
Van Wart, Shipman and Scheraga.14 It has been suggested that
the double-bond character indicated by the C–S bond lengths,
the lengthening of the S–S bond and the near-orthogonality of
C–C–S angles is consistent with p –d interactions between
the aromatic carbon atom and the sulfur.15 Although the
C–S–S angles of 102 7(1) and 102 9(1) are smaller than other
reported values, they are consistent with the dihedral angle of
44 4(2) between the two pyrrole rings. A similar situation
was also noted for 2,2-diaminodiphenyl disul de.15 There is
delocalization around the pyrrole rings with the mean N–C
bond length of 1 384(4) A (mean deviation 0 006 A) and the
C–C bond lengths range from 1 373(4) to 1 408(4) A and the
angles have a mean value of 108 0(3) (mean deviation 1 3 ).
The C(6)–N(2) and C(60)–N(20) bond lengths of 1 149(5) and
1 146(4) A and the C(3)–C(6)–N(2) and C(30)–C(60)–N(20)
angles of 178 2(3) and 177 4(3) are similar to other reported
values for cyano groups.
Synthesis’ Vol. 4, p. 2593 (Interscience: New York 1995).
Barton, D. H. R., Campos-Neves, A. da S., and Cookson,
R. C., J. Chem. Soc., 1956, 3500.
Sauers, R. R., J. Am. Chem. Soc., 1959, 81, 4873.
Hogg, D. R., in ‘Comprehensive Organic Chemistry’ (Ed.
D. N. Jones) Vol. 3, p. 269 (Pergamon: Oxford 1979).
Sheldrick, G. M., SHELX-76, Program for Crystal Structure
Determination, University of Cambridge, Cambridge, U.K.,
1976.
Sheldrick, G. M., SHELXS-86, Structure Solution Package,
University of Gottingen, Federal Republic of Germany,
1986.
Johnson, C. K., ORTEP-II, Report ORNL-5138, Oak Ridge
National Laboratory, Tennessee, 1976.
Scheraga, H. A., Shipman, L. L., and Van Wart, H. E., J.
Phys. Chem., 1975, 79, 1436.
Bryant, M. W. R., and Lee, J. D., Acta Crystallogr., Sect.
B, 1970, 26, 1729.
8
9
10
11
12
13
14
15