Competitive reactivity of the aryl isothiocyanate dipolarophile at N=C versus C=S with nucleophilic 1,3-dipoles: A combined experimental and theoretical study. The reactions of substituted 1,2,3-triazolium-1-aminide 1,3-dipoles with aryl isothiocyanates: New tricyclic thiazolo[4,5-d][1,2,3]triazoles

Article abstract of DOI:10.1039/a705233b

Substituted 1,2,3-triazolium-1-aminide 1,3-dipoles react with aryl isothiocyanates at both the N=C and C=S sites to give mixtures of substituted imidazolo[4,5-d][1,2,3]triazoles and new thiazolo[4,5-d][1,2,3]triazoles including tricyclic derivatives with the C-3a and C-6a bridgeheads linked via (CH₂)₄ and phenanthro groups. The product distribution is controlled by the para-substituent of the aryl isothiocyanate. Theoretical calculations, 3-21G* and 6-31G*, suggest that linear triple bonded canonical forms of the aryl isothiocyanate system play a key role in the ambident reactivity of these systems.

Full text of DOI:10.1039/a705233b

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Competitive reactivity of the aryl isothiocyanate dipolarophile
at N᎐C versus C᎐S with nucleophilic 1,3-dipoles: a combined
᎐
᎐
experimental and theoretical study. The reactions of substituted
1,2,3-triazolium-1-aminide 1,3-dipoles with aryl isothiocyanates:
new tricyclic thiazolo[4,5-d][1,2,3]triazoles
Richard N. Butler,*,a Denise C. Grogan,a Peter D. McDonalda and
Luke A. Burke*,b
a Chemistry Department, University College Galway, Ireland
b Chemistry Department, Rutgers University, Camden, New Jersey 08102, USA
Substituted 1,2,3-triazolium-1-aminide 1,3-dipoles react with aryl isothiocyanates at both the N᎐C and
᎐
C᎐S sites to give mixtures of substituted imidazolo[4,5-d][1,2,3]triazoles and new thiazolo[4,5-d][1,2,3]-
᎐
triazoles including tricyclic derivatives with the C-3a and C-6a bridgeheads linked via (CH2)4 and phenanthro
groups. The product distribution is controlled by the para-substituent of the aryl isothiocyanate.
Theoretical calculations, 3-21G* and 6-31G*, suggest that linear triple bonded canonical forms of
the aryl isothiocyanate system play a key role in the ambident reactivity of these systems.
Because of their high reactivity, thiones have been classified as
R
N
super dipolarophiles among the hetero-double bond 2π-systems
N
Ph
in reactions with a range of 1,3-dipoles.1–4 A favourable charge-
transfer orientation complex as well as a strong HOMO–
LUMO interaction has been suggested as the principal reason
for the high thione reactivity towards nitrone 1,3-dipoles.4
+
–
N
N
Ph
R
1
+
YC6H4
N
C
S
When the C᎐S moiety is part of the isothiocyanate cumulene
᎐
system cycloaddition reactions are often observed on both the
N᎐C and C᎐S bonds in a competitive manner and the C᎐S site
᎐
᎐
᎐
R
R
R
R
N
N
N
N
is not the exclusive reactive centre. Thus diphenyl nitrile imide
reacted with phenyl isothiocyanate to give a mixture of 58%
of the C᎐S adduct and 24% of the N᎐C adduct,5 while
N
Ph
N
Ph
Ph
᎐
᎐
S
N
N
N
C-trifluoromethyl-N-phenyl nitrile imide gave only 14% of the
YC6H4
Ph
C᎐S adduct with methyl isothiocyanate.6 Nitrone 1,3-dipoles
᎐
N
S
may also react with substituted isothiocyanates at the N᎐C or
C6H4Y
᎐
C᎐S sites.7–9 Some cyclic nitrones have been reported to react
᎐
4
2
with benzoyl isothiocyanate exclusively at C᎐S but with phenyl
᎐
and methyl isothiocyanates at N᎐C.7,10 Herein we describe the
reactions of the dipoles 1 with aryl isothiocyanates where com-
᎐
Ph
Ph
R
R
6
N
1
N
+
6a
petitive reactivity at both the N᎐C and C᎐S sites has been
N
N
N
N
᎐
᎐
2
+
N
5
N
observed. Substituents on the aryl isothiocyanate had a large
influence on the competition between the alternative reaction
sites and the factors influencing the relative behaviour of the
S
YC6H4
N
3a
–
4
S
N 3
R
R
Ho (8.20–8.30)
YC6H4
Ho (8.10–8.20)
3 R = (CH2)4
7 R = Ph
cumulene C᎐S and N᎐C bonds for a given 1,3-dipole are
᎐
᎐
5 R = (CH2)4
9 R = Ph
assessed through experimental product distributions and calcu-
lated bond distances and atomic charges.
8 R, R =
10 R, R =
Results and discussion
R
N
a, Y = MeO; b, Y = Me; c, Y = H;
d, Y = Cl; e, Y = NO2; f, Y = Br
Products
N
Ph
When the substituted dipoles 1 were treated with a series of
p-substituted phenyl isothiocyanates, mixtures of the corre-
sponding imidazolo[4,5-d][1,2,3]triazoles 5, 9 and 10, and the
new substituted thiazolo[4,5-d][1,2,3]triazoles 3, 7 and 8, were
obtained (Scheme 1, Table 1). These products, which are not
interconvertible, arose from the cycloaddition–rearrangement
sequence via the intermediates 2 and 4, which we have estab-
lished11,12 as a general reaction pathway for the dipoles 1 with
many dipolarophiles. Throughout the series of reactions,
electron-withdrawing groups at the para-position of the phenyl
N
R
6 R = Ph
Scheme 1
isothiocyanates oriented the reaction strongly towards the
C᎐S site, and a good correlation of the log 3:5 ratio with the
Hammett σp value of this substituent was observed for the ser-
ies with the dipole 1 [R,R = (CH2)4] (r2 = 0.9813, slope 0.7102,
intercept 0.239 63). The log of this 3:5 ratio also correlated
᎐
J. Chem. Soc., Perkin Trans. 1, 1997
3587

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Table 1 Product distribution from reaction of 1 with p-substituted aryl isothiocyanates
Products
Entry
Y (σp)
Ratioa 3:5
Comp.
Mp (T/ЊC)
Yield (%)
Comp.
Mp (T/ЊC)
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
MeO (Ϫ0.27)
Me (Ϫ0.17)
H (0)
Cl (0.23)
NO2 (0.78)
MeO
H
NO2
MeO
Me
1:1
3a
3b
3c
3d
3e
9a
9c
9e
132–134
140–142
140–142
144–146
126–128
109–111
126–128
98–100
—
—
—
210–211
209–211
42.5
49
58
63.5
75
40.5
52
60.5
—
—
—
22
5a
5b
5c
5d
5e
7a
7c
7e
8a
8b
8c
8f
186–188
209–211
211–212
213–215
241–243
231–232
265–266
247–248
216–218
219–221
227–228
238–239
—
42.5
37
30
22.5
13
48.5
46.3
20.2
60
55
65
46
—
1.3:1
1.9:1
2.8:1
5.8:1
1:1.2b
1.1:1b
3:1b
—
—
—
—
—
c,d
—
c,d
—
—
10f
10e
c,d
H
Br
NO2
c
44
—
a In acetone at 20 ЊC. b 9 : 7 product ratio. c Not detected. In each of these reactions 2-phenyl-2H-phenanthro[9,10-d]triazole was isolated in 18–25%
yield. d Reactions at 90 ЊC in toluene.
with the resonance enhanced σp values with lower correlation
coefficient (r2 = 0.9540, slope 0.3848, intercept 0.298 28). The
products 7 were unstable and broke down to the corresponding
4,5-diphenyl-2-aryl-1,2,3-triazole 6 and a mixture of isothio-
cyanates on being heated or under prolonged stirring. In a
previous study13 with the dipoles 1 (R = Ph) this decomposition
occurred unknowingly under the conditions employed which
involved heating and this prevented the detection of the new
ring system 7. The new tricyclic systems 3 and 8 were more
stable but with the phenanthro series heat was necessary for
the reaction and the products 8 also tended to decompose to
2-phenyl-2H-phenanthro[9,10-d]triazole which was always
encountered (Table 1, entries 9–13). Hence the reaction with the
dipole 1 [R,R = (CH2)4], which gave clean high-yield mixtures
of the stable products 3 and 5, was the most suitable for assess-
ing the reactivity of the separate unsaturated bonds of the aryl
isothiocyanate system with the triazolium-1-aminide 1,3-dipole
(Table 1, entries 1–5). The product ratios (Table 1, entries 1–5)
were obtained by direct analysis of the product mixture using
270 MHz proton NMR spectroscopy prior to separation. For
any 3–5 pair the ortho-H atoms, Ho, of the azimine moiety in 5
were about 0.1 ppm more deshielded and readily distinguished
from those in 3. These assignments and ratios were fully con-
firmed within experimental error ( 1%) by direct isolation
of both products. The ratio quoted for the products from p-
nitrophenyl isothiocyanate is obtained by direct separation and
isolation of the products 3e and 5e since there was an overlap of
the Ho proton signals with those of the H atoms ortho to the
NO2 substituent. The results for the product series 3 and 5 were
the same for reactions carried out at ambient temperatures
in either of the solvents acetone, ethyl acetate, acetonitrile or
toluene and product decomposition was not a problem.
spectra of the series 5 the imidazole N-atoms N-4 and N-6
appeared at Ϫ234 to Ϫ235 ppm (from MeNO2) while in com-
pound 3e the thiazole N-6 appeared at Ϫ256 ppm and the other
signal was replaced by the exocyclic imino C᎐N at Ϫ146 ppm.
᎐
All of the compounds showed the azimine nitrogens, N-1 and
N-3 at Ϫ63 to Ϫ76 ppm and 2-N-Ph at Ϫ84 to Ϫ94 ppm.
Theoretical method
All calculations were carried out using the gamess (US) pro-
gram.14 The aryl isothiocyanate structures were optimised with
the 3-21G* basis set using gradient methods. As there is some
question as to the experimental structure of phenyl and other
isothiocyanates15–17 optimisations were also performed on
HNCO, HNCS, MeNCO, MeNCS, PhNCO and PhNCS at the
3-21G* and 6-31G* levels. The results for the detailed dimen-
sions and energy values for this series will be published separ-
ately. The main features relevant to the current synthetic work
are as follows. The NCX bond angle is slightly less than linear,
Ϫ175Њ, as has been found theoretically for many other cumu-
lenes.18 The Z᎐N᎐C bond angle varies from 125Њ to 180Њ accord-
᎐
ing to species and theoretical method. In all cases the 3-21G*
basis set gives linear or near linear angles. With the 6-31G* set,
the Z᎐N᎐C angles in HNCO, MeNCO and PhNCO are 125Њ,
᎐
143Њ and 142Њ, while the barriers to their linear counterparts are
7, 1 and 1 kcal molϪ1, respectively. Only HNCS of the thio
molecules gave a bent Z᎐N᎐C angle of 142Њ with a barrier of
᎐
0.4 kcal molϪ1. At least at the Hartree–Fock level, methyl and
phenyl isothiocyanates are nearly linear, while the isocyanates
are angular but with small barriers to the linear structure. Pre-
liminary studies using large basis sets and high level correlation
techniques for the H and Me molecules show similar trends,
with electron correlation slightly increasing with barriers.
Since explaining the effects of substituents on the synthetic
product distributions is the primary object of this study, fifteen
aryl isothiocyanate structures were optimised at the 3-21G*
level. These were: H, p-Cl, m-Cl, p-Me, m-Me, p-CN, m-CN,
p-NH2, m-NH2, p-NO2, m-NO2, p-OH, m-OH, p-COMe,
p-OMe. From the optimised structures, bond distances and the
Mulliken charges were obtained. Of particular use are the total
atomic and π orbital charges on the N and S atoms. The π
orbital charges were obtained by summing the charges of the
two 2pz orbitals on N and the two 3pz and appropriate 3dz
orbitals on S, z being the direction involved in the conjugated π
system in the aryl and NCS moieties. π Orbital charges typically
vary from zero, one and two corresponding to an empty p
orbital, a one electron atomic orbital contributing to a π
molecular orbital, and a lone pair in resonance structures, 13,
12 and 11 for the N atom and 11, 12 and 13 for the S atom,
respectively. The calculated values of bond lengths, charges and
HOMO–LUMO energies are given in Table 2.
Structure of the products
The structures of the products were established from micro-
analyses, IR, proton, carbon-13 and nitrogen-15 NMR spectra
which showed all of the expected signals. The products 9 have
been previously reported13 and fully characterised. The com-
pounds 5 and 10 showed the expected similar spectral features.
In these compounds the key quaternary N᎐C᎐N bridgehead
carbons appear at 93–106 ppm in the carbon-13 NMR spectra
and the thioamido carbon appears at 182–186 ppm. In the new
fused ring systems 3 the N᎐C᎐N bridgehead appeared in the
range 94–96 ppm while the S᎐C᎐N bridgehead appeared at 87–
89.5 ppm. The ortho H-atoms of the exocyclic imino aryl group
(YC H ) of the series 3 lie under the N᎐C in an endo direction
᎐
6
4
towards the bent fused bicyclic 5,5-structure and it shows
exceptional shielding at 6.8–7.0 ppm in the proton NMR spec-
trum. In compounds 5 these ortho H-atoms of the YC6H4 group
appear in the normal aromatic envelope. In the N-15 NMR
3588
J. Chem. Soc., Perkin Trans. 1, 1997

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Table 2 Bond distances (Å), Hammett and enhanced σ values, total Mulliken and π orbital charges on the N and S atoms, and highest occupied
(HOMO) and lowest unoccupied molecular orbital (LUMO) energies (au)
Bond
distance
CN/Å
Bond
distance
CS/Å
(S) Total
Mulliken
charge
(S) π
orbital
charge
(N) Total
Mulliken
charge
(N) π
orbital
charge
Energy
HOMO/
au
Energy
LUMO/
au
Hammett
σ
Enhanced
σ ϩ/Ϫ
Y
H
p-Cl
m-Cl
1.158 870 0
1.159 958 1
1.160 112 2
1.158 489 2
1.158 703 0
1.161 240 5
1.160 784 8
1.157 404 5
1.158 365 1
1.162 213 0
1.161 316 7
1.158 465 4
1.159 298 5
1.597 230 0
1.594 224 9
1.593 593 3
1.598 460 2
1.597 814 9
1.590 702 8
1.591 832 0
1.602 750
1.598 225 9
1.588 005 0
1.590 276 4
1.598 831 6
1.595 727 4
1.593 431 1
1.599 889 5
0.00
0.22
0.37
Ϫ0.16
Ϫ0.07
0.70
—
0.11
—
16.058 578 1.761 23 7.041 981
16.043 879 1.752 78 7.051 541
16.041 144 1.750 81 7.051 096
16.064 229 1.765 90 7.042 317
16.061 390 1.762 45 7.043 042
16.026 963 1.739 15 7.060 261
16.032 265 1.746 47 7.058 731
16.082 926 1.782 87 7.036 921
16.061 686 1.761 76 7.041 473
16.013 646 1.728 51 7.065 560
16.024 375 1.742 26 7.061 898
16.065 065 1.769 72 7.042 710
16.051 578 1.755 58 7.047 843
16.040 775 1.747 25 7.053 363
16.070 189 1.772 87 7.041 576
1.428 28 Ϫ0.3195
1.433 39 Ϫ0.3251
1.435 19 Ϫ0.3290
1.424 94 Ϫ0.3128
1.427 71 Ϫ0.3167
1.440 35 Ϫ0.3357
1.437 85 Ϫ0.3358
1.412 09 Ϫ0.2848
1.429 41 Ϫ0.3013
1.445 66 Ϫ0.3463
1.440 21 Ϫ0.3406
1.422 24 Ϫ0.3087
1.432 75 Ϫ0.3203
1.435 74 Ϫ0.3278
1.419 95 Ϫ0.3026
0.0875
0.0737
0.0744
0.0914
0.0887
0.0465
0.0595
0.1108
0.0947
0.0148
0.0228
0.0965
0.0836
0.0522
0.1007
p-CH3
m-CH3
p-CN
m-CN
p-NH2
m-NH2
p-NO2
m-NO2
p-OH
m-OH
Ϫ0.31
—
0.99
—
Ϫ1.30
—
1.28
—
Ϫ0.92
—
0.61
Ϫ0.57
Ϫ0.09
0.78
0.71
Ϫ0.38
0.13
p-COCH3 1.160 192 7
p-OCH3
0.47
Ϫ0.27
0.84
Ϫ0.78
1.158 069 0
Ar N–
11
C
S+
Ar N+
13
C
S–
fested in enhanced Hammett values) may need to be accounted
for in these linear cumulene systems.
Ar
N
C
S
12
Scheme 2
Experimental
Ambident behaviour of aryl isothiocyanates
Aryl isothiocyanates exhibit an exceptional linear structure
Mps were measured on an Electrothermal apparatus. IR spec-
tra were measured with a Perkin-Elmer 983G spectrophotom-
eter. NMR spectra were measured on JEOL JNM-GX270 and
GXFT400 instruments with tetramethylsilane as internal
reference and deuteriochloroform or hexadeuteriodimethyl
sulfoxide as solvent. NMR assignments were supported by
decoupled, off-resonance decoupled and DEPT spectra. J
Values are given in Hz. Microanalyses were measured on a
Perkin-Elmer model 240 CHN analyser. The 1,3-dipole sub-
strates 119,20 were prepared as previously described. The follow-
ing are typical examples.
between Ar and ᎐N᎐C᎐S parts, or at least a low barrier of
᎐ ᎐
linearity, compared with isocyanates and most triatomic cumu-
lenes ᎐X᎐Y᎐Z. This suggests strong resonance contributions
᎐ ᎐
from the forms 11 and 13 each of which contains a triple bond.
The contribution of 13 should be enhanced by electron donat-
ing groups and that of 11 by electron withdrawing substituents.
Due to the well known relationship between bond order and
bond length rather good linearity can be expected from a plot
of total charge to CS or CN bond length. These plots are avail-
able as supplementary material (Sup 57307; 6 Pages) deposited
with the British Library. Details are available from the editorial
office. The values greater than 16 or 7 show greater negative
charge (electron density) on the S and N atoms respectively,
thus favouring more lone pairs (single bond character) on struc-
ture 13 with electron donating groups and on 11 for withdraw-
ing groups.
Reaction of N,2-diphenyl-4,5,6,7-tetrahydro-2H-benzo[1,2,3]-
triazol-1-ium-1-aminide with phenyl isothiocyanate (Entry 3,
Table 1)
A solution of 1 [R,R = (CH2)4] (0.5 g, 1.72 mmol) in dry acet-
one was treated with phenyl isothiocyanate (0.22 ml, 1.8 mmol),
stirred at room temperature for 2 h, evaporated under reduced
pressure and the residue, in dichloromethane (3 ml), placed on
a silica gel column (230–400 mesh, ASTM) and eluted with a
gradient mixture of petrol (bp 40–60 ЊC)–diethyl ether. The first
product from the column was 2,6-diphenyl-5-phenylimino-
3a,5,6,6a-tetrahydro-3a,6a-butano-3H-thiazolo[4,5-d][1,2,3]tri-
azol-2-ium-3-ide 3c (0.42 g, 58%); mp 140–142 ЊC (EtOH)
(Found: C, 70.2; H, 5.2; N, 16.4. C25H23N5S requires C, 70.5;
H, 5.4; N, 16.5%); δH(CDCl3) 1.13, 1.89, 2.15, 2.75 (8H, 4 × m,
cyclohexyl, 4 CH2), 6.80–6.83 (2H, d, Ho of 5-imino Ph, J 8.1),
6.88–7.6 (11H, m, aromatic protons), 8.06–8.09 (2H, d, Ho of
2-N-Ph, J 7.3); δC(CDCl3) 88.1, 95.4 (C-3a, C-6a resp.), 18.05,
21.3, 30.1, 34.35 (CH2)4, 140.8, 122.5, 128.9, 129.3 (C-1Ј, C-2Ј,
C-3Ј and C-4Ј resp. of 2-N-Ph), 139.2, 121.8, 127.6, 129.1 (C-1Ј,
C-2Ј, C-3Ј and C-4Ј resp. of 6-N-Ph), 151.8, 123.3, 128.6, 131.8
When plotting π atomic charge on S to C᎐S bond length
᎐
(linear, r2 = 0.9770, slope 0.285 63, intercept 1.093 84) one can
see where the average value of 1.7 electrons for S corresponds to
a bonding description between C᎐S|| (1 eϪ) and C᎐S ||| (2 eϪ).
᎐
As the π charge on S increases with donating groups, struc-
ture 13 is favoured; while the average charge of 1.4 on N
increases with withdrawing groups, favouring structure 11 (plot
of Mulliken π orbital charge on the N atom to C᎐N bond
᎐
length, A, linear, r2 = 0.9092, slope 0.149 91, intercept 0.945 03).
Triple bonds are more reactive than double bonds in 1,3-
dipolar cycloadditions. Hence we envisage that form 13 enters
the cycloaddition to favour 4 and ultimately the products 5
while products 3 arise from cycloaddition where form 11 is
favoured. Plots of Hammett σ and enhanced σ constants against
CS and CN bond lengths give rather good correlations con-
sidering that one is plotting reactivity indices with minute
changes in bond length measured in the thousandths of
(C-1Ј, C-2Ј, C-3Ј and C-4Ј resp. of 5-imino Ph), 157.9 (C᎐N).
᎐
The second product eluted off the column was 2,4,6-tri-
phenyl-5-thioxo-3,3a,4,5,6,6a-hexahydro-3a,6a-butanoimidaz-
olo[4,5-d][1,2,3]triazol-2-ium-3-ide 5c (0.22 g, 30%); mp 211–
212 ЊC (EtOH) (lit.,13 mp 211–212 ЊC) (Found: C, 70.1; H,
5.8; N, 16.7. Calc. for C25H23N5S: C, 70.5; H, 5.4; N, 16.5%);
δH(CDCl3) 1.48–1.69 (4H, m, cyclohexyl protons), 1.89–2.13
(4H, m, cyclohexyl protons), 7.23–7.62 (13H, m, aromatics),
8.21–8.24 (2H, d, Ho of 2-N-Ph, J 7.7); δC(CDCl3) 93.3 (C-3a,
C-6a), 17.3, 27.9 (CH2)4, 137.4, 129.6, 128.9, 132.3 (C-1Ј, C-2Ј,
C-3Ј and C-4Ј resp. of 2-N-Ph), 140.1, 128.3, 129.2, 122.7
(C-1Ј, C-2Ј, C-3Ј and C-4Ј resp. of 4- and 6-N-Ph), 181.1
angstroms (plot of Hammett σ values to C᎐S bond length, r2,
᎐
0.9668, slope, Ϫ0.009 423 9, intercept 1.596 93; plot of Ham-
mett σ values to C᎐N length, r2, 0.9502, slope 0.003 160 8,
᎐
intercept 1.159 10). For the product ratios there seems to be a
better correlation with the ordinary σ values than with the
enhanced ones but the synthetic yields are subject to 1%
errors. However the total charge contributed from the σ and
perpendicular π systems as well as the conjugated π system
(where the extra resonance effect of a para substituent mani-
J. Chem. Soc., Perkin Trans. 1, 1997
3589

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15
(C᎐S); δ N(CDCl3) Ϫ60.7 (N-1, N-3), Ϫ89.7 (N-2), Ϫ234.2
This was followed from the column by 5-(p-bromophenyl-
᎐
(N-4, N-6).
imino)-2,6-diphenyl-3a,5,6,6a-tetrahydro-3H-3a,6a-(biphenyl-
2,2Ј-diyl)thiazolo[4,5-d][1,2,3]triazol-2-ium-3-ide 8f (0.14 g,
22%), mp 210–212 ЊC (MeCN) (Found: C, 66.1; H, 3.6; N, 11.5.
C33H22N5SBr requires C, 66.0; H, 3.7; N, 11.7%); δH(CDCl3)
6.78 and 7.93 (4H, 2 × d, Hm and Ho resp. of 5-imino-N-
C6H4Br, AAЈBBЈ, JAB 8.2), 7.02–7.52 (16H, m, aromatics), 8.10
(2H, d, Ho of 2-N-Ph); δC(CDCl3) 91.4 (C-3a and C-6a), 140.4,
122.9, 129.1 and 127.6 (C-1Ј, C-2Ј, C-3Ј and C-4Ј of 2-N-Ph),
137.6, 123.6, 128.5 and 129.9 (C-1Ј, C-2Ј, C-3Ј and C-4Ј of 4-N-
Ph), 137.1, 123.7, 127.9 and 112.9 (C-1Ј, C-2Ј, C-3Ј and C-Br of
Reaction of N,2,4,5-tetraphenyl-2H-[1,2,3]triazol-1-ium-1-
aminide with phenyl isothiocyanate (Entry 7, Table 1)
A solution of 1 (R = Ph) (0.5 g, 1.29 mmol) in dry acetone (10
ml) was treated with phenyl isothiocyanate (0.17 ml, 1.4 mmol),
stirred at room temperature for 4 h, evaporated under reduced
pressure and the residue, in dichloromethane (3 ml), placed
on a silica gel column (230–400 mesh ASTM) and eluted with
a petrol (bp 40–60 ЊC)–diethyl ether gradient mixture. The
first product from the column was 2,3a,6,6a-tetraphenyl-
5-phenylimino-3a,5,6,6a-tetrahydro-3H-thiazolo[4,5-d][1,2,3]-
triazol-2-ium-3-ide 7c (0.35 g, 52%); mp 126–128 ЊC (EtOH)
(Found: C, 75.8; H, 4.7; N, 12.9. C33H25N5S requires C, 75.7;
H, 4.8; N, 13.4%); δH(CDCl3) 8.18–8.21 (2H, d, Ho of 2-N-Ph,
J 7.3), 6.93–7.69 (23H, m, aromatic protons); δC(CDCl3) 94.7
and 103.1 (C-3a and C-6a), 152.2, 146.4, 140.6, 140.3, 132.8,
130.0, 129.7, 129.1, 128.9, 128.6, 128.4, 128.2, 128.1, 126.7,
126.1, 124.7, 124.0, 123.3, 122.4 and 119.2 (aromatics), 157.7
5-imino-N-C H Br), 149.5 (C᎐N), remaining aromatics; 124.4,
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129.5, 129.7, 130.4, 131.4, 131.7, 132.2 and 133.0.
References
1 R. Huisgen and X. Li, Tetrahedron Lett., 1983, 24, 4185.
2 R. Huisgen and E. Langhals, Tetrahedron Lett., 1989, 30, 5369.
3 R. Huisgen, L. Fisera, H. Giera and R. Sustmann, J. Am. Chem.
Soc., 1995, 117, 9671.
4 R. Sustmann, W. Sicking and R. Huisgen, J. Am. Chem. Soc., 1995,
117, 9679.
5 R. Huisgen, R. Grashey, M. Seidl, H. Knupfer and R. Schmidt,
Ann., 1962, 658, 169.
6 K. Tanaka, O. Honda, K. Minoguchi and K. Mitsuhashi,
J. Heterocycl. Chem., 1987, 24, 1391.
7 D. St. C. Black and K. G. Watson, Tetrahedron Lett., 1972, 4191.
8 G. Zinner and E. Eghtessad, Arch. Pharm., 1979, 312, 907 (Chem.
Abstr., 1980, 92, 11 093m).
9 S. Kajigaeshi, S. Matsuoka, S. Kanemasa and M. Noguchi,
Heterocycles, 1984, 22, 461.
10 D. St. C. Black and K. G. Watson, Aust. J. Chem., 1973, 26, 2473.
11 For a review see R. N. Butler and D. F. O’Shea, Heterocycles, 1994,
37, 571.
12 R. N. Butler, F. A. Lysaght and L. A. Burke, J. Chem. Soc., Perkin
Trans. 2, 1992, 1103.
(N᎐C).
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The second product off the column was 2,3a,4,6,6a-penta-
phenyl-5-thioxo-3,3a,4,5,6,6a-hexahydroimidazolo[4,5-d]-
[1,2,3]triazol-2-ium-3-ide 9c (0.31 g, 46%); mp 265–266 ЊC
(EtOH) (lit.,13 mp 265–266 ЊC) (Found: C, 75.8; H, 4.9; N,
13.05. Calcd. for C33H25N5S: C, 75.7; H, 4.8; N, 13.4%);
δH(CDCl3) 8.48–8.51 (2H, d, Ho of 2-N-Ph, J 7.3), 6.97–7.68
(23H, m, aromatics); δC(CDCl3) 101.1 (C-3a and C-6a), 139.9,
138.5, 135.2, 132.8, 129.5, 129.2, 128.5, 127.8, 127.7, 127.6,
127.5 and 122.9 (aromatics), 185.0 (C᎐S).
᎐
Reaction of 9,10-bis(phenylazo)phenanthrene with p-bromo-
phenyl isothiocyanate (Entry 12, Table 1)
A solution of 9,10-bis(phenylazo)phenanthrene (0.4 g, 1.04
mmol) in dry toluene (20 ml) was treated with p-bromophenyl
isothiocyanate (0.67 g, 3.12 mmol), stirred at 90 ЊC for 40 h,
evaporated under reduced pressure and the residue, in dichloro-
methane (3 ml), placed on a silica gel column (230–400 mesh
ASTM) and eluted with a gradient mixture of petrol (bp 40–
60 ЊC)–dichloromethane (1:0–1:1.5 v/v). The first product
from the column was 2-phenyl-2H-phenanthreno[9,10-d]-
triazole (16%). The next product eluted off the column was 6-
(p-bromophenyl)-2,4-diphenyl-5-thioxo-3,3a,4,5,6,6a-hexahydro-
3a,6a-(biphenyl-2,2Ј-diyl)imidazolo[4,5-d][1,2,3]triazol-2-ium-3-
ide 10f (0.28 g, 46%), mp 238–239 ЊC (MeCN) (Found: C,
66.4; H, 3.8; N, 11.5. C33H22N5SBr requires C, 66.0; H, 3.7; N,
11.7%); δH(CDCl3) 7.15 and 7.92 (4H, 2 × d, Hm and Ho, resp.
of 6-N-C6H4Br, AAЈBBЈ, JAB 8.6), 6.80–7.53 (16H, m, aromat-
ics), 8.24 (2H, d, Ho of 2-N-Ph); δC(CDCl3) 93.8 (C-3a), 94.1
(C-6a), 139.8, 122.7, 128.9 and 128.2 (C-1Ј, C-2Ј, C-3Ј and C-4Ј
of 2-N-Ph), 137.5, 123.5, 129.1 and 129.4 (C-1Ј, C-2Ј, C-3Ј and
C-4Ј of 4-N-Ph), 136.6, 123.6, 129.6 and 123.0 (C-1Ј, C-2Ј, C-3Ј
13 R. N. Butler and D. M. Colleran, J. Chem. Soc., Perkin Trans. 1,
1992, 2159.
14 M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S.
Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S. J.
Su, T. L. Windus, M. Dupuis and J. A. Montgomery, J. Comput.
Chem., 1993, 14, 1347.
15 M. Onda, S. Kambayashi, T. Sakaizumi and I. Yamaguchi, J. Mol.
Struct., 1976, 34, 299; R. J. Higgins, L. Combs, T. B. Molloy Jr. and
R. L. Cook, J. Mol. Struct., 1975, 28, 121.
16 C. V. Stephenson, W. C. Coburn and W. S. Wilcox, Spectrochim.
Acta, 1961, 17, 933; N. S. Ham and J. B. Willis, Spectrochim. Acta,
1960, 16, 279.
17 H. Leung, R. J. Suffolk and J. D. Watts, Chem. Phys., 1986, 109, 289.
18 L. A. Burke, J. Elguero, G. Leroy and M. Sana, J. Am. Chem. Soc.,
1976, 98, 1685.
19 R. N. Butler, A. M. Evans, A. M. Gillan, J. P. James, E. McNeela,
D. Cunningham and P. McArdle, J. Chem. Soc., Perkin Trans. 1,
1990, 2537.
20 R. N. Butler, F. A. Lysaght, P. D. McDonald, C. S. Pyne, P. McArdle
and D. Cunningham, J. Chem. Soc., Perkin Trans. 1, 1996, 1623.
and C-Br of 6-N-C H Br), 182.6 (C᎐S), remaining aromatics;
127.7, 129.7, 129.9, 131.4, 132.2, 132.4 and 133.2. One signal
overlapped in the 129–132 ppm region.
Paper 7/05233B
Received 21st July 1997
Accepted 12th August 1997
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3590
J. Chem. Soc., Perkin Trans. 1, 1997