New facile tandem route to oxo- and thioxo[1,2,4]triazolo[1,5-a]pyridinium salts

Article abstract of DOI:10.1021/jo061361l

(Chemical Equation Presented) 2-Arylsulfanyl- and benzylsulfanylpyridinium N-arylimides (2), easily available from tetrazolo[1,5-b]-pyridinium salts (1), participate in 1,3-dipolar cycloaddition with aryl isothiocyanates and aryl isocyanates to result in

Full text of DOI:10.1021/jo061361l

New Facile Tandem Route to Oxo- and
Thioxo[1,2,4]triazolo[1,5-a]pyridinium Salts
Roberta Palko´, Zsuzsanna Riedl, Orsolya Egyed, La´szlo´ Fa´bia´n, and Gyo¨rgy Hajo´s*
Chemical Research Center, Hungarian Academy of Sciences, H-1025 Budapest, Pusztaszeri u´t 59. Hungary
ghajos@chemres.hu
ReceiVed June 30, 2006
2-Arylsulfanyl- and benzylsulfanylpyridinium N-arylimides (2), easily available from tetrazolo[1,5-b]-
pyridinium salts (1), participate in 1,3-dipolar cycloaddition with aryl isothiocyanates and aryl isocyanates
to result in formation of fused thioxo- and oxo[1,2,4]triazolium salts (5 and 12), respectively. This
transformation is interpreted as a regular 1,3-cycloaddition followed by spontaneous elimination of the
aryl- or benzylsulfanyl group. Formation of these triazolium salts can be followedsunder appropriate
reaction conditionssby ring-opening reactions to afford some new triazolyldienes (6). Recognition of
the intermediate participation of the thiolate anion along the pathway 1 f 5 allowed elaboration of a
simple procedure to 5 implying a tandem reaction sequence.
Introduction
isothiocyanates and isocyanates as 1,3-dipolarophiles will be
described. These reagents, containing cumulated double bonds,
proved to be suitable dipolarophiles in several cases.4,5,6,7
Experiments with reactions of several derivatives of 2 with
aryl or benzyl isothiocyanates in dichloromethane led to
unexpected results. In most cases a mixture was obtained
containing two components: a fused thioxotriazolium salt (5,
A ) Cl) and a triazolyldiene (6, Schemes 2 and 3). To the best
of our knowledge, few examples for oxo or thioxo derivatives
of this ring system have been published.8 To rationalize the
surprising formation of a salt containing a chloride anion it had
to be assumed that isothiocyanates react with 2 in a 1,3-dipolar
cycloaddition but, in contrast to the above-mentioned earlier
cases, with a different regioselectivity. If it is C-2 besides the
exo nitrogen atom in 2 that participates in the cycloaddition, a
cycloadduct (7) can be formed from which a spontaneous
elimination of the arylthiolate anion can occur to yield the fused
thioxo[1,2,4]triazolium arylthiolate salt 8 as a second intermedi-
ate. As the isolated salt (5, A ) Cl) contained a chloride anion,9
In our recent papers1,2 we described that tetrazolopyridinium
salts (1), available from 2-aminopyridines in two simple reaction
steps in high yields,3 can conveniently be transformed to
2-arylsulfanylpyridinium arylimides (2) of zwitterionic structure
(mesomeric betaines) by reaction with aryl- or benzylthiolates.
These strongly dipolar derivatives (2) proved to be suitable
starting compounds for various cyclizations and subsequent ring
transformations. Thus, these compounds undergo 1,3-dipolar
cycloaddition (e.g., with N-phenylmaleimide) to give tetrahy-
dropyrazolo[1,5-a]pyridines (3) as cycloaddition products, and
this transformation was followed by a facile ring transformation
to tetrahydropyrrolo[3,2-b]pyridines (4) in good yields. In these
reactions the 1,3-dipolar cycloadditions proceeded in a regi-
oselective manner with the exclusive participation of C-6 and
the exo nitrogen atom of the sulfanylpyridinium arylimide
compound (2) (Scheme 1).
Results and Discussion
In this paper the continuation of these studies will be
discussed, and reaction of the mesomeric betaines (2) with
(4) Bast, K.; Behrens, M.; Durst, T.; Grashey, R.; Huisgen, R.; Schiffer,
R.; Temme, R. Eur. J. Org. Chem. 1998, 379.
(5) Valenciano, J.; Sanches-Pavon, E.; Cuadro, A. M.; Vaquero, J. J.;
Alvarez-Builla, J. J. Org. Chem. 2001, 66, 8528.
(6) Devi, I.; Harsha, N.; Bhuyan, P. J. Tetrahedron Lett. 2004, 45, 2405.
(7) Ritter, T.; Carreira, E. M. Angew. Chem., Int. Ed. 2005, 44, 936.
(8) (a) Molina, P.; Alajarin, M.; Arques, A.; Hernandez, H. J. Chem.
Soc. Perk. Trans. I 1984, 1891. (b) Palazzo, G.; Baiocchi, L. Gazz. Chim.
Ital. 1966, 96, 1020.
* To whom correspondence should be addressed. Phone: +36-1-4381110.
Fax: +36-1-4381140.
(1) Riedl, Zs.; Ko¨ve´r, P.; Soo´s, T.; Hajo´s, Gy.; Egyed, O.; Fa´bia´n, L.;
Messmer, A. J. Org. Chem. 2003, 68, 5652.
(2) Messmer, A.; Ko¨ve´r, P.; Riedl, Zs.; Go¨mo¨ry, AÄ .; Hajo´s, Gy.
Tetrahedron 2002, 58, 3613.
(3) Messmer, A.; Gelle´ri, A.; Hajo´s, Gy. Tetrahedron 1986, 42, 4827.
10.1021/jo061361l CCC: $33.50 © 2006 American Chemical Society
Published on Web 09/02/2006
J. Org. Chem. 2006, 71, 7805-7812
7805

Palko´ et al.
SCHEME 1
SCHEME 2
its origin can exclusively be the dichloromethane solvent. Thus,
it had to be anticipated that the liberated arylthiolate anion
reacted with dichloromethane to yield formaldehyde diarylth-
ioacetal (10) and chloride anion.10 In accordance with these
considerations, a thorough chromatographic analysis of the
mother liquor obtained after work up of the reaction mixture
allowed detection and identification (by mass spectrometry) of
acetal 10 (Scheme 2). For analytical purposes the chloride salts
5 (A ) Cl) were transformed to the more stable tetrafluoroborate
salts 5 (A ) BF4).
Formation of dienes 6 can easily be rationalized based upon
some earlier observations:11-13 azolopyridinium salts containing
bridgehead nitrogen atom can react with nucleophiles so that
first an addition product (9) is formed which undergoes retro-
electrocyclization to yield dienes. As arylthiolates are formed
in the above transformations (Scheme 2), these fairly nucleo-
philic species are capable of such additions and can easily lead
to arylsulfanyldienes (6). Ring opening of triazolium salt 5 to
diene 6 has also been supported experimentally: the isolated
salt 5b was reacted with p-tolylthiophenolate and pyrrolidine
to give the appropriate 1-arylsulfanyl-4-triazolyldiene (6b) and
1-pyrrolidinyl-4-triazolyldiene (11), respectively (Scheme 4).
Comparison of the relative yields for 5 and 6 in various
experiments indicates that these ratios can vary to a considerable
(9) Direct evidence of the presence of chloride anion in derivative 5b
(A ) Cl) and 12e (A ) Cl) was provided by both elemental analysis and
observation of HCl fragment in EI mass spectra.
(10) Similar reactions of thiolates and dichloromethane or dibro-
momethane in the presence of strong base or acid have been reported earlier,
see: (a) Bertaina, B.; Rouvier, E.; Cambon, A. J. Fluorine Chem. 1994,
66, 287. (b) Weissflog, E. Phosphorus Sulfur 1981, 12, 89. (c) Ono, N.;
Miyake, H.; Saito, T.; Kaji, A. Synthesis 1980, 11, 952. (d) Patney, H. K.
Org. Prepr. Proc. Int. 1994, 26, 377. Quite recently such transformation in
the presence of weak base and rhodium catalyst has also been observed,
see: Tanaka, K.; Kaori, A. Org Lett. 2005, 7, 1537. It should be noted that
the present case represents a third experimental condition as neither base
nor acid is present in the reaction mixture.
(11) Messmer, A.; Hajo´s, Gy.; Tima´ri, G. Tetrahedron 1992, 48, 8451.
(12) Hajo´s, Gy.; Kotschy, A. Acta Chim. SloVenica 1998, 45, 285.
7806 J. Org. Chem., Vol. 71, No. 20, 2006

Oxo- and Thioxo[1,2,4]triazolo[1,5-a]pyridinium Salts
SCHEME 3
SCHEME 4
SCHEME 5
extent, and these differences could not be correlated to any
properties of the starting compounds (Table 1). Thus, the
question arose whether the reaction could be directed to either
the triazolium or the diene product; thus, elaboration of a
practical procedure to selectively obtain either of these com-
pounds was desirable.
highly crystalline triazolium salts could be isolated in high
yields. If these triazolium salts were treated in a separate
experiment with arylthiolates, dienes 6 could be obtained only
as products. This was demonstrated for the case of 5b (A )
Cl): when this compound was first transformed to the soluble
tetrafluoroborate salt 5b (A ) BF4) and then this salt was reacted
with 4-tolylthiolate, diene 6b was obtained in good yield
(Scheme 4).
The fact that in the above-discussed procedure the triazolium
salts (5) are obtained from tetrazolium salts (1) in two synthetic
steps (i.e., via formation of 2) with intermediate participation
of the arylsulfanyl group has an interesting consequence. As
the arylthiolate anion enters the tetrazolium salt in the first step
to give the zwitterions 2 and then is eliminated in the second
step to give the triazolium salt, the question arises whether these
two consecutive transformations could be carried out with much
lower amount of arylthiolate. In other words, the question arose
whether triazolium salt (5) could be prepared by a one-pot
tandem procedure by reacting tetrazolium salt 1 with an aryl
isothiocyanate reagent in the presence of a small amount of
arylthiolate.
As triazolium salt (5) seemed to be an intermediate in the
pathway leading to the arylsulfanyldiene (6), a possible reason
for a relatively high ratio of the triazolium salt in some cases
(e.g., entries 8 and 10 in Table 1) could be its poor solubility
which hinders its participation in the subsequent ring opening.
This idea led to the recognition that the yield of the triazolium
salt might be increased by changing the chloride anion to another
anion, causing even lower solubility. In line with this consid-
eration, reactions of 2 with aryl isothiocyanates were carried
out in dibromomethane (method C), and the resulting bromide
products (5, A ) Br) were obtained in high yield without
formation of a detectable amount of the diene 6 (Entry 3, Table
1). Similar improvement of the yield of triazolium salt 5 was
achieved when the reaction was carried out in dichloromethane
containing tetrabutylammonium bromide (Entry 2, Table 1).
This also solved the problem of the selective preparation of
the dienes. The above-mentioned experiments showed that the
Experiments in this respect proved to be successful. Two
selected tetrazolium salts (1a and 1b) were treated with phenyl
and benzyl isothiocyanate in the presence of 0.1 equiv of
4-chlorophenyl and 4-tolylthiolate. The data shown in Scheme
(13) Nagy, I.; Ko´nya, D.; Riedl, Zs.; Kotschy, A.; Tima´ri, G.; Messmer,
A.; Hajo´s, Gy. Tetrahedron 2003, 59, 7485-7489.
J. Org. Chem, Vol. 71, No. 20, 2006 7807

Palko´ et al.
TABLE 1. Yields of Selected Derivatives of 2-Thioxo-2,3-dihydro-1H-[1,2,4]triazolo[1,5-a]pyridin-4-ium Salts 5 and Aryl- or
Aralkylsulfanylbutadienyl}-2,4-dihydro-3H-[1,2,4]triazole-3-thiones (6)a
entry
method
2a-e,g
R1
5a-e,h,i
yield
A
6a,c,e,f,g,h,i,k
yield
82%
1
2
3
4
5
6
7
8
A
B
C
A
A
A
A
A
A
A
A
2b
2b
2b
2c
2c
2a
2d
2e
2d
2e
2g
4-NO2-C6H4
4-NO2-C6H4
Ph
5e
5e
5b
5c
5i
5d
5a
5h
5d
5e
5d
5%
Cl
Br
Br
Cl
Cl
Cl
Cl
Cl
Cl
Cl
6h
73%
88%
60%
44%
6%
52%
80%
13%
60%
Ph
6c
6k
6g
6a
-
6e
6f
6i
11%
18%
58%
41%
C6H5CH2
4-NO2-C6H4
Ph
C6H5CH2
4-NO2-C6H4
4-NO2-C6H4
4-NO2-C6H4
9
10
11
77%
15%
92%
a Method A: reaction of 2 and isothiocyanate in dichloromethane. Method B: reaction of 2 and isothiocyanate in dichloromethane in the presence of
tetrabutylammonium bromide. Method C: reaction of 2 and isothiocyanate in dibromomethane.
SCHEME 6
SCHEME 7
5 reveal that the expected thioxotriazolium salts 5a, 5b, 5g, and
5h were obtained in good to excellent yields.
presence of a third component in a small (max. 11%) amount
which was separated by column chromatography. X-ray analysis
of this isolated and strongly fluorescent yellow solid14,15
Reaction of pyridinium arylimidates 2 with aryl isocyanates
led to further interesting findings. Similar to the transformations
with aryl isothiocyanates, in these cases formation of two main
products has been observed also: the oxo-substituted dihydro-
triazolo[1,5-a]pyridinium salts (12) and oxotriazolyldienes (13),
obviously formed by the same reaction mechanism as discussed
above (Scheme 6).
(14) Compound 14: C36H31N5O7, Mr ) 654.66, yellow needle, size 0.50
× 0.17 × 0.13 mm, triclinic, space group P-1, a ) 10.5170(1) Å, b )
12.589(1) Å, c ) 13.541(1) Å, R ) 72.45(1)°, â ) 70.51(1)°, γ ) 70.07-
(1)°, V ) 1588.7(3) Å3, Z ) 2, Fcalc ) 1.350 g/cm3, µ ) 0.787 mm-1, T )
293(2) K. The final model (437 parameters) was refined to wR2 ) 0.1802
for all data (6603 reflections), R1 ) 0.0575 for reflections with I > 2σ(I)
(4966), and GOF) 1.105.
Analysis of the mother liquor obtained from reaction of 2c
with 4-methoxyphenyl isocyanate, however, also indicated the
(15) ORTEP representation of the dienyltriazolone 14 is given in the
Supporting Information. Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
7808 J. Org. Chem., Vol. 71, No. 20, 2006

Oxo- and Thioxo[1,2,4]triazolo[1,5-a]pyridinium Salts
structure refinement (SHELXL-9721). Hydrogen atoms were placed
in ideal positions and refined isotropically in the riding mode.
Syntheses of tetrazolo[1,5-b]pyridinium salts (1)3 and 2-arylsul-
fanyl- and 2-benzylsulfanylpyridinium-N-arylimides1,2 (2) have been
published earlier. Novel derivatives (i.e., 1b, 2b,c,e,f,h,i) have been
prepared according to these literature procedures.
3-(4-Tolyl)-3H-tetrazolo[1,5-a]pyridin-4-ium Tetrafluorobo-
rate (1b). Yield 53% (1.6 g); colorless crystals; mp >300 °C. Anal.
Calcd for C12H11BF4N4 (298.05): C, 48.36; H, 3.72; N, 18.80.
Found: C, 48.42; H, 3.62; N, 18.76.
2-(4-Tolylsulfanyl)pyridinium-N-(4-tolyl)imide (2b). This com-
pound was obtained from 3-(4-methylphenyl)-3H-tetrazolo[1,5-a]-
pyridin-4-ium tetrafluoroborate (1b, 1.5 g, 5 mmol) and sodium
4-tolylthiolate generated from 4-tolylthiophenol (0.7 g, 5.8 mmol)
and sodium hydride (0.26 g, 108 mmol). Yield 1.39 g, (90%); red
crystals; mp 116-120 °C. 1H (CDCl3) δ (ppm): 8.54 (1H, dd, J )
6 + 1.5 Hz, H2), 7.54 (2H, m, H2′′ + H6′′), 7.30 (2H, m, H3′′ +
H5′′), 6.96-7.14 (4H, m, H2′ + H3′ + H5′ + H6′), 6.85 (2H, m,
H3 + H4), 6.54 (1H, dd J ) 8.5 + 1.5 Hz, H5), 2.44 (3H, s, CH3),
2.29 (3H, s, CH3). 13C (CDCl3) δ (ppm): 20.8 (CH3), 21.3 (CH3),
118.4 (C2′ + C6′), 120.4 (C3), 122.7 (C5), 123.8 (C4), 126.4 (C4′),
130.2 (C3′′ + C5′′), 130.3 (C4′′), 131.0 (C3′ + C5′), 132.2 (C2),
136.0 (C2′′ + C6′′), 140.6 (C1′′), 148.6 (C6), 149.4 (C1′). Anal.
Calcd for C19H18N2S (306.42): N, 9.14; S, 10.46. Found: N, 8.96;
S, 10.36.
showedsand NMR spectral data supportedsthat a new oxot-
riazolyldiene was formed bearing a ring-closed dioxoimida-
zolone substituent at the end of the diene chain (14). Because
of the fact that this imidazolone ring contained two R1
substituents on the ring nitrogen atoms deriving from the aryl
isocyanate reagent, the reaction mechanism for formation of
14 shown in Scheme 7 had to be anticipated.
The presence of the diene moiety in this product clearly
indicated that in the course of the reaction to 14 a nucleophilic
attack on the oxotriazolium salt (12) took place. If some amount
of unreacted aryl isocyanate is present at that stage of the
reaction when arylthiolate anion has already been formed,
reaction of these two speciessin accordance with literature
sources16scan occur to yield anion 15. Reaction of this anion
with 12 results in formation of a diene (16a), which can also
be represented by valence-bond structure 16b. This dipolar
structure convincingly shows the possibility of the ring closure
to the dioxoimidazoline moiety to yield the final product 14.
This mechanism seemed to be supported by the finding that
the protonated species of 15 was isolated from the reaction
mixture.
2-(4-Tolylsulfanyl)pyridinium-N-(4-methoxyphenyl)imide (2c).
Red crystals (1.39 g, 85%); mp 96-99 °C.
Conclusion
2-(4-Chlorophenylsulfanyl)pyridinium-N-(4-tolyl)imide (2e).
Red crystals (1.25 g 74%); mp 135-138 °C.
2-(4-Chlorophenylsulfanyl)pyridinium-N-(4-methoxyphenyl)-
imide (2f). Orange crystals (1.41 g, 81%); mp 95-115 °C.
2-(4-Benzylsulfanyl)pyridinium-N-(4-tolyl)imide (2h). Red
crystals (1.3 g, 85%); mp 127-134 °C.
The present findings show that reaction of the easily
accessible arylthio- and benzylthiopyridinium arylimidates (2)
with isocyanates and isothiocyanates can open a way to hitherto
unknown group of heterocyclic derivatives and, furthermore, a
convenient procedure to the new oxo- and thioxo dihydro[1,2,4]-
triazolo[1,5-a]pyridinium salts implying a tandem reaction
sequence has been elaborated. Investigation of the possible
generalization of ring openings to dienes related to 14 as well
as elaboration of feasible experimental procedures to these
compounds are in progress. Detailed further investigations are
planned for rationalization of the regioselectivity of these
cycloadditions with cumulenes which proved to be in contrast
to reactions with other dipolarophiles. It should be noted that
this difference might be due to the concerted or stepwise course
of these cycloadditions.17
2-(4-Benzylsulfanyl)pyridinium-N-(4-methoxyphenyl)imide (2i).
Red crystals (1.58 g, 97%); mp 100-114 °C.
General Procedure for Reaction of Aryl- and Benzylsulfa-
nylpyridinium Arylimides (2) with Aryl Isothiocyanates. A
solution of the appropriate pyridinium arylimide (2, 2 mmol) and
aryl isothiocyanate (2.4 mmol) in abs. dichloromethane (22 mL)
was stirred at room temperature, and the progress of the reaction
was monitored by TLC. After disappearance of the starting material
(5-20 h) the deposited colorless crystals were filtered off and
washed with dichloromethane to give the corresponding 1,3-diaryl-
2-thio-2,3-dihydro[1,2,4]triazolo[1,5-a]pyridinium chloride (5, A )
Cl). This salt was converted to the appropriate tetrafluoroborate
salt using tetrafluoroboric acid. The filtrate was then evaporated
and subjected to column chromatography on alumina by a hexane-
ethyl acetate mixture 4:1 as an eluent. Separation of the main
fraction around Rf ) 0.6 gave the appropriate 1-arylsulfanyldienyl-
4-(1,4-diaryl[1,2,4]triazol-5(1H)thione (6).
3-(4-Methoxyphenyl)-1-(4-nitrophenyl)-2-thiooxo-2,3-dihydro-
1H-[1,2,4]triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5f, A
) BF4). This compound was prepared from 2f (0.684 g, 2 mmol)
and 4-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.31
g of product (37%); colorless crystals; mp 256-257 °C. 1H (DMSO-
d6) δ (ppm): 8.71 (1H, dd, J ) 7.1 + 1.2 Hz, H5), 8.61 (2H, m,
H3′ + H5′), 8.39 (1H, ddd, J ) 9 + 8.2 + 1.2 Hz, H7), 7.98 (2H,
m, H2′ + H6′), 7.90 (1H, dd, J ) 9 + 1 Hz, H8), 7.77 (1H, ddd,
J ) 8.2 + 7.1 + 1 Hz, H6), 7.69 (2H, m, H2′′ + H6′′), 7.37 (2H,
m, H3′′ + H5′′), 3.90 (3H, s, OCH3). 13C (DMSO-d6) δ (ppm):
56.6 (OCH3), 111.0 (C8), 117.2 (C3′′ + C5′′), 121.4 (C6), 122.2
(C1′′), 126.5 (C3′ + C5′), 127.0 (C5), 130.6 (C2′ + C6′), 132.0
(C2′′ + C6′′), 137.2 (C1′), 141.4 (C4′), 142.4 (C7), 149.4 (C2),
163.0 (C8a), 166.8 (C4′′). Anal. Calcd for C19H15BF4N4O3S
(466.22): C, 48.95; H, 3.24; N, 12.02; S, 6.88. Found: C, 49.11;
H, 3.20; N, 11.92; S, 6.91.
Experimental Section
X-ray Crystallography. Crystals of 14 were mounted on glass
fibers. The data set was collected on an Enraf-Nonius CAD4
diffractometer with graphite-monochromated Cu KR radiation at
room temperature. Lattice parameters were determined by a least-
squares fit for 25 reflections. The intensities of three standard
reflections were monitored every hour, and no decay was indicated.
All reflections were corrected for Lorentz and polarization effects.18
Absorption correction was applied using ψ-scan data.19 The space
groups were determined from the unit cell parameters and intensity
statistics. The structures were solved by direct methods (SHELXS-
9720). All non-hydrogen atoms were modeled anisotropically in the
(16) Ulrich, H.; Tucker, B.; Sayigh, A. A. R. J. Org. Chem. 1967, 32,
3938.
(17) Matsouka, T.; Harano, K. Tetrahedron 1995, 51, 6451.
(18) Harms, K. XCAD4 Data Reduction Program for CAD4 Diffracto-
meters; Philipps-Universita¨t Marburg: Germany, 1996.
(19) Reibenspies, J. DATCOR Program for Empirical Absorption Cor-
rection; Texas A & M University: College Station, TX, 1989.
(20) Sheldrick, G. M. SHELXS-97 Program for Crystal Structure
Solution; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(21) Sheldrick, G. M. SHELXL-97 Program for Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
J. Org. Chem, Vol. 71, No. 20, 2006 7809

Palko´ et al.
3-(4-Chlorophenyl)-1-phenyl-2-thiooxo-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5a, A ) BF4).
This compound was prepared from 2d (0.694 g, 2 mmol) and phenyl
isothiocyanate (0.324 g, 2.4 mmol) to give 0.39 g of product (52%);
colorless crystals; mp >300 °C.
3-(4-Tolyl)-1-phenyl-2-thiooxo-2,3-dihydro-1H-[1,2,4]triazolo-
[1,5-a]pyridin-4-ium Tetrafluoroborate (5b, A ) BF4). This
compound was prepared from 2e (0.652 g, 2 mmol) and phenyl
isothiocyanate (0.324 g, 2.4 mmol) to give 0.59 g of product (83%);
colorless crystals; mp > 300 °C.
2-(4-Methoxyphenyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-1,3-dien-
1-yl}-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (6c). This
compound was prepared from 2c (0.644 g, 2 mmol) and phenyl
isothiocyanate (0.324 g, 2.4 mmol) to give 0.1 g of product (11%);
mp 122-124 °C.
5-[(1Z,3E)-4-(benzylthio)buta-1,3-dien-1-yl]-2-(4-chlorophe-
nyl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (6d). This
compound was prepared from 2g (0.652 g, 2 mmol) and phenyl
isothiocyanate (0.324 g, 2.4 mmol) to give 0.54 g of product (58%);
yellow crystals; mp 102-105 °C.
2-(4-Chlorophenyl)-5-{(1Z,3E)-4-[(4-chlorophenyl)thio]buta-
1,3-dien-1-yl}-4-(4-nitrophenyl)-2,4-dihydro-3H-1,2,4-triazole-
3-thione (6e). This compound was prepared from 2d (0.694 g, 2
mmol) and p-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to
give 0.82 g of product (77%); yellow crystals; mp 189-191 °C.
5-{(1Z,3E)-4-[(4-Chlorophenyl)thio]buta-1,3-dien-1-yl}-2-(4-
tolyl)-4-(4-nitrophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione
(6f). This compound was prepared from 2e (0.652 g, 2 mmol) and
4-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.15 g of
product (15%); yellow crystals; mp 170-179 °C.
2-(4-Chlorophenyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-1,3-dien-
1-yl}-4-(4-nitrophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (6g).
This compound was prepared from 2a (0.652 g, 2 mmol) and
4-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.77 g of
product (58%); yellow crystals; mp 136-142 °C.
3-(4-Methoxyphenyl)-1-phenyl-2-thiooxo-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5c, A ) BF4).
This compound was prepared from 2c (0.644 g, 2 mmol) and phenyl
isothiocyanate (0.324 g, 2.4 mmol) to give 0.44 g of product (60%);
colorless crystals; mp 264-265 °C.
3-(4-Cholorophenyl)-1-(4-nitrophenyl)-2-thioxo-2,3-dihydro-
1H-[1,2,4]triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5d, A
) BF4). This compound was prepared from 2a (0.652 g, 2 mmol)
and 4-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.06
g of product (6%); colorless crystals; mp 294-298 °C.
3-(4-Tolyl)-1-(4-nitrophenyl)-2-thiooxo-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5e, A ) BF4).
This compound was prepared from 2a (0.612 g, 2 mmol) and
4-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.03 g of
product (4%); colorless crystals; mp 298-300 °C.
2-(4-Tolyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-1,3-dien-1-yl}-4-
(4-nitrophenyl) -2,4-dihydro-3H-1,2,4-triazole-3-thione (6h). This
compound was prepared from 2a (0.612 g, 2 mmol) and 4-nitro-
phenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.8 g of product
(82%); yellow crystals; mp 158-164 °C.
1-Benzyl-3-(4-cholorophenyl)-2-thiooxo-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5g, A ) BF4).
This compound was prepared from 2a (0.612 g, 2 mmol) and benzyl
isothiocyanate (0.357 g, 2.4 mmol) to give 0.02 g of product (2%);
colorless crystals; mp 219-222 °C.
5-[(1Z,3E)-4-(Benzylthio)buta-1,3-dien-1-yl]-2-(4-chlorophe-
nyl)-4-(4-nitrophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (6i).
This compound was prepared from 2g (0.652 g, 2 mmol) and
4-nitrophenyl isothiocyanate (0.432 g, 2.4 mmol) to give 0.93 g of
product (92%); yellow crystals; mp 170-180 °C.
1-Benzyl-3-(4-tolyl)-2-thiooxo-2,3-dihydro-1H-[1,2,4]triazolo-
[1,5-a]pyridin-4-ium Tetrafluoroborate (5h, A ) BF4). This
compound was prepared from 2e (0.652 g, 2 mmol) and benzyl
isothiocyanate (0.357 g, 2.4 mmol) to give 0.59 g of product (80%);
colorless crystals; mp 198-199 °C.
4-Benzyl-2-(4-methoxyphenyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-
1,3-dien-1-yl}-2,4-dihydro-3H-1,2,4-triazole-3-thione (6k). This
compound was prepared from 2c (0.644 g, 2 mmol) and benzyl
isothiocyanate (0.358 g, 2.4 mmol) to give 0.17 g of product (18%);
yellow crystals; mp 100-112 °C.
1-Benzyl-3-(4-methoxyphenyl)-2-thioxo-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (5i, A ) BF4).
This compound was prepared from 2c (0.644 g, 2 mmol) and benzyl
isothiocyanate (0.358 g, 2.4 mmol) to give 0.34 g of product (44%);
colorless crystals; mp 217-220 °C.
4-Benzyl-5-[(1Z,3E)-4-(benzylthio)buta-1,3-dien-1-yl]-2-(4-
chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (6l). This
compound was prepared from 2g (0.652 g, 2 mmol) and benzyl
isothiocyanate (0.358 g, 2.4 mmol) to give 0.45 g of product (48%);
yellow crystals; mp 122-124 °C.
4-Benzyl-5-[(1Z,3E)-4-[(4-benzylthio)buta-1,3-dien-1-yl}-2-(4-
tolyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (6m). This com-
pound was prepared from 2h (0.612 g, 2 mmol) and benzyl
isothiocyanate (0.358 g, 2.4 mmol) to give 0.24 g of product (26%);
yellow crystals; mp 109-111 °C.
Reaction of 2b with 4-Nitrophenyl Isothiocyanate in the
Presence of Tetrabutylammonium Bromide: 3-(4-Tolyl)-1-(4-
nitrophenyl)-2-thiooxo-2,3-dihydro-1H-[1,2,4]triazolo[1,5-a]py-
ridin-4-ium Bromide (5e, A ) Br). This compound was prepared
from 2b (0.612 g, 2 mmol), 4-nitrophenyl isothiocyanate (0.432 g,
2.4 mmol), and tetrabutylammonium bromide (0.966 g, 3 mmol)
to give 0.65 g of product (73%); colorless crystals; mp >300 °C.
The signals of this product in the NMR spectra were identical with
those of 5e (A ) BF4). Anal. Calcd for C19H15BrN4O2S (443.32):
C, 51.48; H, 3.41; N, 12.64. Found: C 51.32; H, 3.41; N, 12.31.
Reaction of 2b with Phenyl Isothiocyanate in Dibro-
momethane: 3-(4-Tolyl)-1-phenyl-2-thiooxo-2,3-dihydro-1H-
[1,2,4]triazolo[1,5-a]pyridin-4-ium Bromide (5b, A ) Br). This
compound was prepared from 2b (0.306 g, 1 mmol) and phenyl
isothiocyanate (0.162 g, 1.2 mmol) in dibromomethane (11 mL) to
give 0.35 g of product (88%); colorless crystals; mp > 300 °C.
The signals of this product in the NMR spectra were identical with
those of 5b (A ) BF4). Anal. Calcd for C19H16BrN3S (398.32): C,
4-Benzyl-2-(4-chlorophenyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-
1,3-dien-1-yl}-2,4-dihydro-3H-1,2,4-triazole-3-thione (6j). This
compound was prepared from 2a (0.652 g, 2 mmol) and benzyl
isothiocyanate (0.357 g, 2.4 mmol) to give 0.35 g of product (37%);
1
yellow crystals; mp 112-114 °C. H (CDCl3) δ (ppm): 8.0 (2H,
m, H2′′ + H6′′), 7.44 (2H, m, H3′′ + H5′′), 7.34 (2H, m, H2IV
+
H6IV), 7.29 (5H, m, H2′′′ + H3′′′ + H4′′′ + H5′′′ + H6′′′), 7.20
(1H, ddd, J ) 14.5 + 11.5 + 1 Hz, H3′), 7.11 (2H, m, H3 IV + H5
IV), 6.83 (1H, d, J ) 14.5 Hz, H4′), 6.46 (1H, dd, J ) 11.5 + 11.5
Hz, H2′), 5.63 (1H, dd, J ) 11.5 + 1 Hz, H1′), 5.38(2H, s, CH2),
2.28 (3H, s, CH3). 13C (CDCl3) δ (ppm): 21.4 (CH3), 47.9 (CH2),
105.1 (C1′), 123.9 (C4′), 125.2 (C3′′ + C5′′), 127.3 (C2′′ + C6′′),
128.1 (C1IV), 128.4 (C4′′′), 128.9 (C3′′′ + C5′′′), 129.2 (C2′′′ +
C6′′′), 130.4 (C3IV + C5IV), 132.9 (C2IV + C6IV), 133.4 (C4IV),
135.0 (C1′′′), 137.2 (C4′′), 137.7 (C2′), 139.1 (C1′′), 140.6 (C3′),
148.5 (C5), 166.5 (C3). Anal. Calcd for C26H22ClN3S (476.06): C,
65.60; H, 4.66; N, 8.83; S, 13.47. Found: C, 65.53; H, 4.83; N,
8.70; S, 13.59.
2-(4-Chlorophenyl)-5-{(1Z,3E)-4-[(4-chlorophenyl)thio]buta-
1,3-dien-1-yl}-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione
(6a). This compound was prepared from 2d (0.694 g, 2 mmol) and
phenyl isothiocyanate (0.324 g, 2.4 mmol) to give 0.4 g of product
(41%); yellow crystals; mp 162-163 °C.
2-(4-Tolyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-1,3-dien-1-yl}-4-
phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (6b). This com-
pound was prepared from 2b (0.612 g, 2 mmol) and phenyl
isothiocyanate (0.324 g, 2.4 mmol) to give 0.05 g of product (6%);
yellow crystals; mp 168-174 °C.
7810 J. Org. Chem., Vol. 71, No. 20, 2006

Oxo- and Thioxo[1,2,4]triazolo[1,5-a]pyridinium Salts
57.29; H, 4.05; N, 10.55; S, 8.05. Found: C 57.12; H, 4.01; N,
10.40; S, 8.09.
(C5), 129.2 (C2′ + C6′), 132.0 (C2′′ + C6′′), 140.2 (C8a), 141.2
(C7), 148.1 (C2), 161.3 (C4′), 162.8 (C4′′). Anal. Calcd for C20H18-
ClN3O3 (383.83): C, 62.58; H, 4.73; N, 10.95; Found: C 62.52;
H, 4.71; N, 10.75.
3-(4-Chlorophenyl)-2-oxo-1-phenyl-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (12a, A ) BF4).
This compound was prepared from 2a (0.652 g, 2 mmol) and phenyl
isocyanate (0.285 g, 2.4 mmol) to give 0.13 g of product (18%);
colorless crystals; mp > 300 °C.
3-(4-Tolyl)-2-oxo-1-phenyl-2,3-dihydro-1H-[1,2,4]triazolo[1,5-
a]pyridin-4-ium Tetrafluoroborate (12b, A ) BF4). This com-
pound was prepared from 2b (0.612 g, 2 mmol) and phenyl
isocyanate (0.285 g, 2.4 mmol) to give 0.32 g of product (47%);
colorless crystals; mp > 300 °C.
3-(4-Chlorophenyl)-1-(4-methoxyphenyl)-2-oxo-2,3-dihydro-
1H-[1,2,4]triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (12c,
A ) BF4). This compound was prepared from 2e (0.652 g, 2 mmol)
and 4-methoxyphenyl isocyanate (0.357 g, 2.4 mmol) to give 0.2
g of product (26%); colorless crystals; mp >300 °C.
Formation of Dienes (6b and 11) by Reaction of Triazolium
Salt (5b) with 4-Tolylthiophenole and Pyrrolidine. 2-(4-Tolyl)-
5-{(1Z,3E)-4-[(4-tolyl)thio]buta-1,3-dien-1-yl}-4-phenyl-2,4-di-
hydro-3H-1,2,4-triazole-3-thione (6b). To a mixture of sodium
hydride (0.041 g, 17 mmol), p-thiocresol (0.112 g, 0.9 mmol), and
abs. THF (2 mL), a solution of 5b (A ) BF4) (0.2 g, 0.6 mmol) in
abs. acetonitrile (4 mL) was added, and the reaction mixture was
stirred for 6 h at room temperature. The product was isolated by
column chromatography to give 6b, 0.126 g (46%). All physical
and spectroscopic data of this product were identical with earlier
isolated compound obtained from 2b and phenyl isothiocyanate.
2-(4-Tolyl)-4-phenyl-5-[(1Z,3E)-4-pyrrolidin-1-ylbuta-1,3-
dien-1-yl]-2,4-dihydro-3H-1,2,4,triazole-3-thione (11). To a sus-
pension of 5b (A ) BF4) (0.12 g, 0.3 mmol) in abs. acetonitrile (1
mL), pyrrolidine (0.042 g, 0.6 mmol) was added at room temper-
ature. A brown solution was formed, and the product was
precipitated. The solid was filtered off to give 0.04 g of product
(64%); yellow crystals; mp 143-152 °C.
Direct Formation of 3-(4-Chlorophenyl)-1-phenyl-2-thiooxo-
2,3-dihydro-1H-[1,2,4]triazolo[1,5-a]pyridin-4-ium Tetrafluo-
roborate (5a, A ) BF4) from 3-(4-chlorophenyl)-3H-tetrazolo-
[1,5-a]pyridin-4-ium Tetrafluoroborate (1a). Tandem Route.
After generation of sodium 4-chlorothiophenolate (sodium hydride
(0.0086 g, 0.36 mmol), 4-chlorothiophenol (0.025 g, 0.18 mmol),
in abs. THF (1 mL)) the solution was cooled to -40 °C, and a
mixture of 1a (0.51 g, 1.6 mmol) and phenyl isothiocyanate (0.256
g, 1.9 mmol) in abs. acetonitrile (8 mL) was added gradually. The
reaction mixture was allowed warm to room temperature and stirred
for 28 h, and after evaporation of solvent the residue was treated
with Et2O to give white precipitate, which was recrystallized from
acetonitrile to give 0.63 g (92%) of 5a (A ) BF4).
The same procedure was applied for the following conversions.
1a (0.51 g, 1.6 mmol), benzyl isothiocyanate (0.283 g, 1.9 mmol),
p-thiocresolate prepared from sodium hydride (0.0086 g, 0.36
mmol) and p-thiocresol (0.023 g, 0.18 mmol) gave 0.64 g (92%)
of 5g (A ) BF4). 1b (0.50 g, 1.6 mmol), phenyl isothiocyanate
(0.256 g, 1.9 mmol), p-thiocresolate prepared from sodium hydride
(0.0086 g, 0.36 mmol) and p-thiocresol (0.023 g, 0.18 mmol) gave
0.43 g (63%) of 5b (A ) BF4). 1b (0.50 g, 1.6 mmol), benzyl
isothiocyanate (0.283 g, 1.9 mmol), 4-chlorothiophenolate prepared
from sodium hydride (0.0086 g, 0.36 mmol) and 4-chlorothiophenol
(0.025 g, 0.18 mmol) gave 0.55 g (78%) of 5h (A ) BF4).
General Procedure for Reaction of Aryl- and Benzylsulfa-
nylpyridinium Arylimides (2) with Aryl Isocyanates. A solution
of the appropriate pyridinium arylimide (2, 2 mmol) and aryl
isocyanate (2.4 mmol) in abs. dichloromethane (22 mL) was stirred
at room temperature, and the progress of the reaction was monitored
by TLC. After disappearance of the starting material (5-20 h) the
deposited colorless crystals were filtered off and washed with
dichloromethane to give the corresponding 1,3-diaryl-2-oxo-2,3-
dihydro[1,2,4]triazolo[1,5-a]pyridinium salts (12). The filtrate was
then evaporated and subjected to column chromatography on
alumina by a hexane-ethyl acetate mixture 4:1 as eluent. Separation
of the main fraction around Rf ) 0.6 gave the appropriate
1-arylsulfanyldienyl-4-(1,4-diaryl[1,2,4]triazol-5(1H) one (13)
1,3-Bis(4-methoxyphenyl)-2-oxo-2,3-dihydro-1H-[1,2,4]tria-
zolo[1,5-a]pyridin-4-ium Chloride (12e, A ) Cl). This compound
was prepared from 2c (0.644 g, 2 mmol) and 4-methoxyphenyl
isocyanate (0.348 g, 2.4 mmol) to give 0.33 g of product (41%);
colorless crystals; mp 294-295 °C. 1H (DMSO-d6) δ (ppm): 8.62
(1H, dd, J ) 6.5 + 1 Hz, H5), 8.27 (1H, ddd, J ) 8.5 + 7.5 + 1
Hz, H7), 7.74 (2H, m, H2′ + H6′), 7.70 (1H, dd, J ) 8.5 + 1.5
Hz, H6), 7.63 (1H, ddd, J ) 7.5 + 6.5 + 1.5 Hz, H6), 7.60 (2H,
m, H2′′ + H6′′), 7.32 (2H, m, H3′ + H5′), 7.25 (2H, m, H3′′ +
H5′′), 3.90 (3H, s, OCH3), 3.85 (3H, s, OCH3). 13C (DMSO-d6) δ
(ppm): 56.4 (OCH3), 56.6 (OCH3), 110.3 (C8), 116.2 (C3′′ + C5′′),
116.9 (C3′ + C5′), 119.9 (C6), 121.1 (C1′′), 122.8 (C1′), 126.7
1-(4-Methoxyphenyl)-3-(4-tolyl)-2-oxo-2,3-dihydro-1H-[1,2,4]-
triazolo[1,5-a]pyridin-4-ium Tetrafluoroborate (12d, A ) BF4).
This compound was prepared from 2e (0.652 g, 2 mmol) and
4-methoxyphenyl isocyanate (0.348 g, 2.4 mmol) to give 0.53 g of
product (72%); colorless crystals; mp >300 °C.
5-[(1Z,3E)-4-(Benzylthio)buta-1,3-dien-1-yl]-2-(4-tolyl)-4-phenyl-
2,4-dihydro-3H-1,2,4-triazol-3-one (13b). This compound was
prepared from 2h (0.612 g, 2 mmol) and phenyl isocyanate (0.285
g, 2.4 mmol) to give 0.3 g of product (43%); yellow crystals; mp
1
163-166 °C. H (CDCl3) δ (ppm): 7.91(2H, m, H2′′ + H6′′),
7.61 (′H; ddd, J ) 14.5 + 11.5 + 1 Hz, H3′), 7.18-7.58 (12H,
m), 6.69 (1H, d, J ) 14.5 Hz, H4′), 6.34 (1H, dd, J ) 11.5 + 11.5
Hz, H2′), 5.44 (1H, dd, J ) 11.5 + 1 Hz, H1′), 4.10 (2H, CH2),
2.35 (3H,CH3). 13C (CDCl3) δ (ppm): 21.0, 36.8, 106.3, 118.7-
(2C), 123.7, 127.5(2C), 128.5, 128.7(2C), 128.8(2C), 128.9, 129.5-
(2C), 129.6(2C), 132.7, 135.0, 135.2, 135.5, 136.3, 137.4, 143.4,
144.0. Anal. Calcd for C26H23N3OS (425.55): C, 73.38; H, 5.45;
N, 9.87; S, 7.54. Found: C, 73.22; H, 5.38; N, 9.87; S, 7.75.
2-(4-Chlorophenyl)-5-{(1Z,3E)-4-[(4-tolyl)thio]buta-1,3-dien-
1-yl}-4-phenyl -2,4-dihydro-3H-1,2,4-triazol-3-one (13a). This
compound was prepared from 2a (0.652 g, 2 mmol) and phenyl
isocyanate (0.285 g, 2.4 mmol) to give 0.44 g of product (49%);
yellow crystals; mp 112-119 °C.
2-(4-Chlorophenyl)-4-(4-methoxyphenyl)-5-{(1Z,3E)-4-[(4-
tolyl)thio]buta-1,3-dien-1-yl}-2,4-dihydro-3H-1,2,4-triazol-3-
one (13c). This compound was prepared from 2e (0.652 g, 2 mmol)
and 4-methoxyphenyl isocyanate (0.348 g, 2.4 mmol) to give 0.37
g of product (39%); yellow crystals; mp 119-123 °C.
5-[(1Z,3E)-4-(Benzylthio)buta-1,3-dien-1-yl]-2-(4-chlorophe-
nyl)-4-(4-methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (13d).
This compound was prepared from 2g (0.652 g, 2 mmol) and
p-methoxyphenyl isocyanate (0.348 g, 2.4 mmol) to give 0.54 g of
product (67%); colorless crystals; 156-166 °C.
Isolation of Compound 14. (E)-5-((E)-3-(1,4-Bis(4-methoxy-
phenyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)allylidene)-1,3-
bis(4-methoxyphenyl)imidazolidine-2,4-dione (14). This com-
pound was isolated by column chromatography (alumina, hexane:
EtOAc as eluent) from the reaction mixture of 2c (0.644 g, 2 mmol)
and 4-methoxyphenyl isocyanate (0.348 g, 2.4 mmol) to give 0.07
g of product (11%); yellow crystals; mp 215-227 °C. 1H (CDCl3)
δ (ppm): 8.45 (1H, dd, J ) 15.5 + 12 Hz, H2′), 7.96 (2H, m,),
7.39 (2H, m), 7.24 (2H, m), 7.21 (2H, m), 7.04 (2H, m), 7.02 (2H,
m), 7.0 (2H,m), 6.94 (2H, m), 6.05 (1H, dd, J ) 15.5 + 1 Hz,
H3′), 5.90 (1H, dd, J ) 12 + 1 Hz, H1′), 3.8-3.9 (12H, s, OCH3).
Anal. Calcd for C36H31N5O7 (645.66): C, 66.97; H, 4.84; N, 10.85.
Found: C, 66.97; H, 4.84; N, 10.55.
Isolation of Compound 15. S-(4-Tolyl)(4-methoxyphenyl){[(4-
methoxyphenyl)amino]carbonyl}thiocarbamate (15). This com-
pound was isolated by column chromatography (alumina, hexane:
EtOAc as eluent) from the reaction mixture 2c (0.644 g, 2 mmol)
J. Org. Chem, Vol. 71, No. 20, 2006 7811

Palko´ et al.
and 4-methoxyphenyl isocyanate (0.348 g, 2.4 mmol) to give 0.06
g of product (7%); colorless crystals; mp 175-176 °C. Anal. Calcd
for C23H22N2O4S (422.50): C, 65.38; H, 5.25; N, 6.63; S, 7.59.
Found: C, 65.47; H, 5.36; N, 6.50; S, 7.43.
Thanks are due to the valuable discussions with Dr. Andra´s
Kotschy.
Supporting Information Available: More detailed information,
NMR spectra of all compounds, 1H NMR data (Tables 2-4),
elemental analysis (Table 5), crystallographic information file (CIF),
and ORTEP diagram of compound 14. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. Financial support (OTKA T047317,
NKFP 1A/005/2004, and project (GVOP-3.2.1-2004-04-0311/
3.0)) for the elemental analyzer is gratefully acknowledged.
JO061361L
7812 J. Org. Chem., Vol. 71, No. 20, 2006