Cyclization of 1,2,4-triazenes to 1,2,4-triazoles using oxidizing reagents - NaClO, Ca(ClO)2, Dess-Martin periodinane and Ley's TPAP/NMO

Article abstract of DOI:10.1016/S0040-4020(01)00976-0

A simple and efficient approach to 1,3,5-trisubstituted 1,2,4-triazoles via cyclization of 1,2,4-triazenes employing commonly used oxidizing agents such as NaClO, Ca(ClO)₂, Dess-Martin periodinane and Ley's oxidizing agent (TPAP/NMO) is described. The reaction proceeds under mild conditions and is compatible with various functional groups. Extension of this approach to prepare triazoles on solid support has also been investigated.

Full text of DOI:10.1016/S0040-4020(01)00976-0

TETRAHEDRON
Pergamon
Tetrahedron 57 12001) 9677±9682
Cyclization of 1,2,4-triazenes to 1,2,4-triazoles using
oxidizing reagentsÐNaClO, CaꢀClO)2, Dess±Martin periodinane
and Ley's TPAP/NMO
K. Paulvannan,p,² Ron Hale, Daniel Sedehi and Tao Chen
Affymax Research Institute, 3410 Central Expressway, Santa Clara, CA 95051, USA
Received 28 June 2001; accepted 11 October 2001
AbstractÐA simple and ef®cient approach to 1,3,5-trisubstituted 1,2,4-triazoles via cyclization of 1,2,4-triazenes employing commonly
used oxidizing agents such as NaClO, Ca1ClO)2, Dess±Martin periodinane and Ley's oxidizing agent 1TPAP/NMO) is described. The
reaction proceeds under mild conditions and is compatible with various functional groups. Extension of this approach to prepare triazoles on
solid support has also been investigated. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
H2O2 mediated cyclization of triazene 6.4 Due to its limited
functional group compatibility, this approach could not be
used in our medicinal chemistry program to prepare combi-
natorial libraries of triazoles. After a systematic investi-
gation, we recently reported an improved synthesis of
1,3,5-trisubstituted 1,2,4-triazole 7 via a Ag2CO3 mediated
cyclization of triazene 6 1Scheme 1).5 The mild reaction
conditions and tolerance to a wide range of functional
Compounds containing 1,2,4-triazole moiety have received
considerable attention among medicinal chemists because
molecules with these structural features have been found to
display a wide range of potent biological activities, such as
antihypertensive,1 antifungal2 and antibacterial.3 Buzykin et
al. reported a simple approach to 1,2,4-triazole 7 through a
Scheme 1. 1a) C6H6, room temperature, 12 h; 1b) 1.5 equiv. of NCS, 3.0 equiv. of DMS, CH2Cl2, 0 to 2788C to room temperature; 1c) 1.2 equiv. of 5,
1.2 equiv. of TEA 12.4 equiv. for 5d), CH3CN, room temperature, 15 h; 1d) 1.2 equiv. of Ag2CO3, CH3CN, 2 h; 1e) NaClO, CH3CN, 24 h; 1f) 2.0 equiv. of
Ca1ClO)2, CH3CN, 24 h; 1g) 1.5 equiv. of DMP, CH2Cl2, 3 h; 1h) 0.2 equiv. of TPAP/1.5 equiv. of NMO, CH3CN, 3 h.
Keywords: hydrazone; nitrilimines; cycloaddition; triazoles.
Corresponding author. Tel.: 11-650-266-3634; fax: 11-650-266-3501; e-mail: kpaulvannan@sunesis.com
Current address: Sunesis Pharmaceuticals, Inc., 341 Oyster Point Boulevard, South San Francisco, CA 94080, USA.
p
²
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020101)00976-0

9678
K. Paulvannan et al. / Tetrahedron 57 )2001) 9677±9682
Table 1. Preparation triazoles using various oxidizing agents
Entry
Triazole
R1±CH2±NH2
Yield 1%)
Dess±Martin periodinane
a
Ag2CO3
NaClO
68
Ca1ClO)2
TPAP/NMO
79
1
7a
7b
69
65
81
69
2
3
51
63
51
60
7c
47
73
45
59
63
73
52
86
45
75
4
7d
MeO2C±1CH2)3±NH2
a
See Ref. 5.
groups make this approach very attractive synthetic route
for rapid synthesis of molecules with 1,2,4-triazole skeleton.
As part of our efforts directed toward the preparation of
combinatorial libraries6 of small molecules to identify
novel biologically active compounds, we became interested
in constructing combinatorial libraries of 1,3,5-trisubsti-
tuted 1,2,4-triazoles on solid support7 using our Ag2CO3
mediated cyclization approach. Unfortunately, the use of
Ag2CO3 on solid support made the washing process very
dif®cult and the resin could not be ef®ciently separated
from Ag2CO3. In order to eliminate the practical dif®culties
associated with the use of Ag2CO3, we wanted to ®nd
alternative reagents that could promote the cyclization of
1,2,4-triazene to 1,2,4-triazole in solution and on solid
support. Herein we report the result of this investigation
which led to the identi®cation of various oxidizing agents
such as NaClO,8,9 Ca1ClO)2,10 Dess±Martin periodinane
11,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-311H)-one,
DMP)11 and Ley's oxidizing agent 1tetra-n-propylammo-
nium perruthenate 1VII)/4-methylmorpholine N-oxide,
TPAP/NMO)12 to cyclize the triazene 6 to triazole 7.
and the triazene 6a was chosen as the model system to
investigate the cyclization reaction. The requisite triazene
6a was readily prepared using literature procedure.4,5 Reac-
tion of the hydrazone 3, prepared from condensation of
benzaldehyde 11) and phenylhydrazine 12), with a N-chloro-
succinimide 1NCS)/dimethyl sul®de 1DMS) complex13 gave
the hydrazonyl chloride 4. Treatment of 4 with 1.2 equiv. of
benzylamine 15a) and 1.2 equiv. of triethylamine 1TEA) in
CH3CN for 15 h followed by removal of the solvent and
excess TEA provided the crude triazene 6a. The triazene
6a was then allowed to react with various reagents to
promote the cyclization and the reaction progress was
monitored by thin layer chromatography 1TLC) and LC/MS.
14
Assuming that the oxidizing property of Ag2CO3 was
responsible for the cyclization of triazene 6a to triazole
7a, we speculated that the reaction of triazene 6a with an
oxidizing agent would promote the cyclization to give the
triazole 7a. To test our hypothesis, initially, NaClO solution
1sodium hypochlorite, Aldrich) was chosen because it is
readily available and has been widely used as an oxidizing
agent in organic synthesis.8,9 As predicted, treatment of
triazene 6a in CH3CN with NaClO solution for 24 h
smoothly promoted the cyclization and yielded the triazole
7a in 68% overall yield for two steps, after a simple aqueous
work-up and ¯ash column chromatography 1Table 1, entry
2. Results and discussion
Our initial optimization study was carried out in solution
Scheme 2. Cyclization of triazene 6 to triazole 7.

K. Paulvannan et al. / Tetrahedron 57 )2001) 9677±9682
9679
Scheme 3. 1a) 10.0 equiv. of Cs2CO3, 10.0 equiv. of 4-hydroxybenzaldehyde, 858C, DMF, 12 h; 1b) 10.0 equiv. of phenyl hydrazine, 10.0 equiv. of BF3. Et2O,
DMF, room temperature, 12 h; 1c) 7.0 equiv. of NCS, 14.0 equiv. of DMS, CH2Cl2 0 to 2788C to room temperature; 1d) 20.0 equiv. of 5, CH3CN, room
temperature; 12 h; 1e) 10.0 equiv. of DMP, CH2Cl2, room temperature, 12 h: 1f) 1.0 equiv. of TPAP/12.0 equiv. of NMO, CH3CN, room temperature, 12 h; 1g)
95:5 TFA/H2O, 2 h, room temperature.
1). Comparison of the LC/MS data of the reaction mixture
before and after the addition of NaClO clearly indicated that
NaClO was essential to promote the cyclization. Similar to
NaClO, reaction of the triazene 6a with commercially
available solid Ca1ClO)2 1calcium hypochlorite, Lan-
caster)10 in CH3CN for 24 h also smoothly promoted the
cyclization and furnished the triazole 7a in 65% overall
yield for two steps, after removal of the solvent and puri®-
cation 1Table 1, entry 1). The above yields 168 and 65%) are
comparable with the yield of 7a 169%) obtained using
Ag2CO3 method5 1shown in Table 1, entry 1 for compari-
son), which clearly indicates that the NaClO and Ca1ClO)2
mediated triazole syntheses are as ef®cient as the Ag2CO3
method.5 In addition to the mild reaction condition
and simple work-up procedure, the reagents, NaClO and
Ca1ClO)2, are commercially available, inexpensive and
environmentally friendly, which make this approach
superior to our previously reported Ag2CO3 method.5
not been fully exploited. While our study was in progress,
Nicolaou et al. reported a DMP and 2-iodoxybenzoic acid
1IBX)15 induced cyclization of unsaturated anilides to
prepare various nitrogen heterocycles.16,17 The oxidizing
property, solubility in organic solvents and ease of handling
encouraged us to choose the above reagents for our cycli-
zation study. Treatment of the triazene 6a with 1.5 equiv. of
DMP in CH2Cl2 or 0.2 equiv. of TPAP and 1.5 equiv. of
NMO in CH3CN for 3 h smoothly promoted the cyclization
and provided the triazole 7a in 81 and 79% yields, respec-
tively, after puri®cation. The reactions were very clean and
did not require any aqueous work-up. Removal of the
solvent followed by puri®cation of the crude reaction
mixture provided the triazole 7a. It is important to note
that in the absence of TPAP, NMO did not promote the
cyclization of triazene 6a, which clearly indicated the
important role of TPAP in the cyclization reaction. To our
knowledge, these are the ®rst examples utilizing oxidizing
reagents DMP and TPAP/NMO to convert 1,2,4-triazene to
1,2,4-triazole. The yields of triazole 7a obtained using DMP
and TPAP/NMO methods 181 and 79%, respectively) are
superior to the yield 169%) obtained using the Ag2CO3
method 1Table 1, entry 1). Since IBX has been shown to
have oxidizing property similar to DMP, IBX would also be
expected to promote the cyclization of triazene 6 to triazole
7. Buzykin et al. proposed a mechanism to account for the
formation of triazoles through cyclization of triazenes in the
presence of an oxidizing reagent 1Scheme 2).4 The key role
Having isolated the triazole 7a in good yields using the
hypochlorite oxidizing agents, we then extended our study
to other commercially available and commonly used oxi-
dizing reagents such as DMP11 and TPAP/NMO.12 Although
these two reagents have been extensively used in organic
synthesis as oxidizing agents to prepare aldehydes and
ketones from the corresponding primary and secondary
alcohols, respectively, the synthetic usefulness of these
reagents to perform other chemical transformations has

9680
K. Paulvannan et al. / Tetrahedron 57 )2001) 9677±9682
of an oxidizing reagent in this reaction is to oxidize the
triazene 6 into an azoimine intermediate A, which then
undergoes tautomerization, cyclization and oxidation in a
tandem sequence to provide the triazole 7. However, no
further mechanistic study was carried out to con®rm the
proposed mechanism in Scheme 2.
using readily available and commonly used oxidizing agents
such as NaClO, Ca1ClO)2, DMP and TPAP/NMO. The reac-
tions were carried out under mild reaction conditions and
the products were isolated in moderate to good yields. The
approach was successfully extended to prepare triazoles on
solid-support, which would allow preparation of combi-
natorial libraries of 1,2,4-triazoles. Construction of combi-
natorial libraries of triazoles on solid support and biological
activities will be reported in due course.
To further probe the synthetic scope of our oxidizing agent
promoted triazole synthesis, the reaction was then extended
to triazenes with different functional groups 6b±d, prepared
from hydrazonyl chloride 4 and amines 5b±d 1Table 1,
entries 2±4). Reaction of triazenes 6b±d with the above
oxidizing agents proceeded smoothly and yielded the
desired triazoles 7b±d in moderate to high yields 1Table
1, entries 2±4). Under the reaction conditions, the presence
of vinyl and pyridyl groups did not yield the corresponding
epoxide and N-oxide products, respectively, as evident from
the LC/MS data of the reaction mixtures 1Table 1, entries 2
and 3). The vinyl and ester functionalities present in tri-
azoles 7b and d, respectively, could be used as handles to
introduce additional structural diversity.
4. Experimental
4.1. General methods
All solvents and reagents were purchased from commercial
sources and used without further puri®cation. H NMR
1
spectral data were obtained on a Varian Gemini 400 instru-
ment with the solvents noted. Chemical shifts were reported
in the d scale in ppm relative to TMS 10.00 ppm) as internal
standard. 13C NMR spectra were obtained by using the
above instrument operating at 100 MHz with solvents
noted. DMP and Ca1ClO)2 were purchased from Lancaster.
TPAP and NaClO were obtained from Aldrich. ArgoGel±
Wang±Cl was obtained from Argonaut Technologies.
Next we turned our attention to examine the adaptability of
this approach to solid-phase synthesis, which would allow
preparation of combinatorial libraries of 1,2,4-triazoles.6,7
Since DMP and TPAP/NMO are soluble in organic solvents,
they were chosen as the reagents of choice for our solid-
phase triazole synthesis. Acid cleavable ArgoGel±Wang±
Cl 1loading 0.39 mmol/g) resin 8 was selected to carry out
the solid-phase triazole synthesis 1Scheme 3). Treatment of
8 with 10.0 equiv. of 4-hydroxybenzaldehyde in the
presence of 10.0 equiv. of Cs2CO3 in DMF at 858C for
12 h provided the resin-bound aldehyde 9, which was then
condensed with phenylhydrazine 12) in the presence of BF3.
Et2O 110.0 equiv.) to provide the hydrazone 10. Initial
attachment of 4-hydroxybenzaldehyde moiety on solid
support and conversion of the aldehyde 9 to hydrazone 10
were readily monitored by the appearance and disappear-
ance of the aldehyde signal in the solid phase magic angle
spinning 1SPMAS) NMR spectrum.18 Reaction of the resin-
bound hydrazone 10 with 7.0 equiv. of NCS/DMS complex
provided the resin-bound hydrazonyl chloride 11, which
was then treated with amines 5a, b, e, f to give the corre-
sponding triazenes 12a±d. Treatment of the triazenes
12a±d with DMP or TPAP/NMO smoothly promoted the
cyclization and furnished the corresponding resin-bound
triazoles 13a±d, which upon treatment with 95% TFA
followed by chromatographic puri®cation provided the
triazoles 14a±d in 16±47% overall yields for six steps
1Scheme 3). In the case of triazenes 12b and c, the triazoles
14b and c were isolated in low yields as a result of the
formation a 1,3-disubstituted triazole5 as the side product.
No further optimization study was carried out to improve
the yields of triazoles 14b and c. Commercial availability of
diverse primary amines, hydrazines and hydroxybenzalde-
hydes makes this approach very attractive to prepare large
numbers of 1,2,4-triazoles in a short period of time.
4.2. General procedure for the preparation of triazenes
6a±d: representative procedure for compound 6a
To a solution of hydrazonyl chloride 1250 mg, 1.09 mmol,
1 equiv.) in CH3CN 110 mL) were added benzylamine 15a)
10.14 g, 1.31 mmol, 1.2 equiv.) and TEA 10.13 g, 1.31
mmol, 1.2 equiv.) and the reaction mixture was stirred at
room temperature for 15 h. Removal of the solvent and
excess TEA provided the crude triazene 6a, which was
then subjected to the cyclization condition.
4.3. Typical procedure for the preparation of triazoles
7a±d using NaClO: representative procedure for
compound 7a
To a solution of the crude triazene 6a 11.09 mmol) in
CH3CN 110 mL) was added NaClO solution 15 mL) and
the reaction mixture was stirred at room temperature for
24 h. The reaction mixture was diluted with EtOAc
125 mL) and washed with H2O 11£20 mL). The organic
layer was drained, dried and evaporated, and the residue
was puri®ed by ¯ash column chromatography 1hexane/
20% EtOAc) to provide triazole 7a 10.220 g, 68% yield).
4.4. Typical procedure for the preparation of triazoles
7a±d using CaꢀClO)2: representative procedure for
compound 7a
To a solution of the crude triazene 6a 11.09 mmol, 1.0
equiv.) in CH3CN 110 mL) was added Ca1ClO)2 10.31 g,
2.18 mmol, 2.0 equiv.) and the reaction mixture was stirred
at room temperature for 24 h. The solvent was evaporated
and the residue was puri®ed by ¯ash column chroma-
tography 1hexane/20% EtOAc) to provide triazole 7a
10.210 g, 65% yield).
3. Conclusion
We have described an ef®cient approach to 1,3,5-trisubsti-
tuted 1,2,4-triazoles through cyclization of 1,2,4-triazenes

K. Paulvannan et al. / Tetrahedron 57 )2001) 9677±9682
9681
4.5. Typical procedure for the preparation of triazoles
7a±d using Dess±Martin periodinane: representative
procedure for compound 7a
amine 15a, b, e, f, 23.40 mmol, 20.0 equiv.) and the reaction
mixture was agitated at room temperature for 12 h. Excess
amine was drained and the resin was washed with DMF
13£30 mL) and CH2Cl2 13£30 mL) to give the correspond-
ing triazene 112a±d).
To a solution of the crude triazene 6a 11.09 mmol) in
CH2Cl2 110 mL) was added DMP 10.69 g, 1.64 mmol,
1.5 equiv.) and the reaction mixture was stirred at room
temperature for 3 h. The solvent was evaporated and the
residue was puri®ed by ¯ash column chromatography
1hexane/20% EtOAc) to provide triazole 7a 10.262 g, 81%
yield).
4.11. General procedure for the preparation of triazoles
14a±d using Dess±Martin periodinane
To a suspension of a triazene 112a±d) 10.59 mmol, 1 equiv.)
in CH2Cl2 125 mL) was added DMP 12.50 g, 5.9 mmol,
10 equiv.) and the mixture was agitated at room temperature
for 12 h. Excess reagents were drained and the resin was
washed with DMF 13£20 mL), MeOH 13£20 mL), and
CH2Cl2 13£20 mL). Treatment of the resin with 95% TFA
120 mL) at room temperature for 2 h followed by removal of
TFA and puri®cation 1hexane/EtOAc) provided the corre-
sponding triazole 114a±d).
4.6. Typical procedure for the preparation of triazoles
7a±d using TPAP/NMO: representative procedure for
compound 7a
To a solution of the crude triazene 6a 11.09 mmol) in
CH3CN 110 mL) were added TPAP 177.0 mg, 0.22 mmol,
0.2 equiv.) and NMO 10.19 g, 1.64 mmol, 1.5 equiv.) and
the reaction mixture was stirred at room temperature for
3 h. The solvent was evaporated and the residue was puri®ed
by ¯ash column chromatography 1hexane/20% EtOAc) to
provide triazole 7a 10.256 g, 79% yield).
4.12. General procedure for the preparation of triazoles
14a±d using NMO/TPAP
To a suspension of a triazene 112a±d) 10.59 mmol, 1 equiv.)
in CH3CN 130 mL) were added NMO 10.83 g, 7.08 mmol,
12 equiv.) and TPAP 10.21 g, 0.59 mmol, 1 equiv.), and the
reaction mixture was agitated at room temperature for 12 h.
Excess reagents were drained and the resin was washed
with DMF 13£20 mL), MeOH 13£20 mL) and CH2Cl2
13£20 mL). Treatment of the resin with 95% TFA
120 mL) at room temperature for 2 h followed by removal
of TFA and puri®cation 1hexane/EtOAc) provided the corre-
sponding triazole 114a±d).
4.7. Preparation of aldehyde 9
To a suspension of ArgoGel±Wang±Cl resin 8 1loading
0.39 mmol/g, 12.0 g, 4.68 mmol, 1 equiv.) in DMF 1100
mL) were added 4-hydroxybenzaldehyde 15.72 g, 46.80
mmol, 10 equiv.) and cesium carbonate 115.25 g, 46.80
mmol, 10 equiv.) and the reaction mixture was heated at
858C for 12 h. Excess reagents were drained, and the resin
was washed with 1:1 H2O/DMF 13£80 mL) and DMF
13£80 mL) to provide the resin-bound aldehyde 9.
4.8. Preparation of hydrazone 10
To a suspension of 9 12.34 mmol, 1 equiv.) in DMF 160 mL)
were added phenylhydrazine 12.53 g, 23.40 mmol, 10
equiv.) and BF3´Et2O 13.32 g, 23.40 mmol, 10.0 equiv.),
and the reaction mixture was agitated at room temperature
for 12 h. Excess reagents were drained, and the resin was
washed with DMF 13£50 mL) and CH2Cl2 12£50 mL) to
provide the resin-bound hydrazone 10.
1
4.12.1. Compound 14a. H NMR 1DMSO-d6) d 6.88 1d,
Jˆ8.8 Hz, 2H), 7.39±7.52 1m, 10H), 7.93 1d, Jˆ8.8 Hz,
2H), 9.82 1s, 1H); 13C NMR 1DMSO-d6) d 115.5, 121.4,
125.7, 127.6, 127.8, 128.6, 128.7, 129.1, 129.5, 130.0,
138.0, 154.2, 158.7, 161.0; HRMS m/z calcd for
C20H15N3O 313.1215, found 313.1222.
4.9. Preparation of hydrazonyl chloride 11
To a solution of N-chlorosuccinimide 12.18 g, 16.38 mmol,
7 equiv.) in CH2Cl2 180 mL) at 08C was added dimethyl
sul®de 12.06 g, 32.76 mmol, 14 equiv.), and the mixture
was stirred at 08C for 10 min. Then the reaction was cooled
to 2788C and the resin-bound hydrazone 10 12.34 mmol,
1 equiv.) was added and the mixture was gently stirred at
2788C for 1 h, and then slowly warmed to room tempera-
ture and stirred for additional 3 h. Excess reagents were
drained and the resin was washed with CH2Cl2 13£50 mL)
to give the resin-bound hydrazonyl chloride 11.
4.12.2. Compound 14b. 1H NMR 1DMSO-d6) d 5.72 1d, Jˆ
11.2 Hz, 1H), 6.34 1d, Jˆ17.2 Hz, 1H), 6.63 1dd, Jˆ17.2,
11.2 Hz, 1H), 6.86 1d, Jˆ8.4 Hz, 2H), 7.55±7.64 1m, 5H),
7.90 1d, Jˆ8.8 Hz, 2H); 13C NMR 1DMSO-d6) d 115.5,
121.4, 121.8, 123.6, 125.3, 127.6, 129.1, 129.6, 136.7,
152.3, 158.7, 160.9; HRMS m/z calcd for C16H13N3O
263.1059, found 263.1065.
4.10. General procedure for the preparation of triazene
12
To a suspension of the resin-bound hydrazonyl chloride 11
11.17 mmol, 1 equiv.) in CH3CN 117 mL) was added an

9682
K. Paulvannan et al. / Tetrahedron 57 )2001) 9677±9682
Soc., Perkin Trans. 1 1998, 3293. 1b) Booth, S.; Hermkens,
P. H. H.; Ottenheijm, H. C. J.; Rees, D. C. Tetrahedron 1998,
54, 15385. 1c) James, I. W. Tetrahedron 1999, 55, 4855.
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7. Triazoles on solid support: 1a) Katritzky, A. R.; Qi, M.; Feng,
D.; Zhang, G.; Grif®th, M. C.; Watson, K. Org. Lett. 1999, 1,
1189. 1b) Wilson, M. W.; Hernandez, A. S.; Calvet, A. P.;
Hodges, J. C. Mol. Diversity 1998, 3, 95.
1
4.12.3. Compound 14c. H NMR 1DMSO-d6) d 4.22 1s,
2H), 6.84 1d, Jˆ8.4 Hz, 2H), 7.12 1d, Jˆ7.2 Hz, 2H), 7.19
1m, 1H), 7.26 1m, 2H), 7.49±7.57 1m, 5H), 7.85 1d, Jˆ
8.8 Hz, 2H), 9.76 1s, 1H); 13C NMR 1DMSO-d6) d 31.9,
115.5, 121.6, 125.0, 126.6, 127.5, 128.4, 128.5, 128.9,
129.5, 136.2, 137.1, 154.8, 158.5, 160.6; HRMS m/z calcd
for C21H17N3O 327.1372, found 327.1365.
8. 1a) Stevens, R. V.; Chapman, K. T. Tetrahedron Lett. 1982,
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59, 7549.
4.12.4. Compound 14d. 1H NMR 1CDCl3) d 1.39 1d,
Jˆ6.4 Hz, 6H), 3.18 1m, 1H), 6.78 1dd, Jˆ8.8, 2.0 Hz,
2H), 7.46 1m, 2H), 7.52±7.58 1m, 3H), 7.88 1dd, Jˆ8.8,
2.0 Hz, 2H); 13C NMR 1CDCl3) d 21.4, 26.1, 116.1,
120.3, 126.0, 128.6, 129.9, 130.0, 136.8, 158.9, 160.3,
161.5; HRMS m/z calcd for C17H17N3O 279.1372, found
279.1366.
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Acknowledgements
The authors would like to thank Dr Ted Baer, Dr Mike
Needles and Dr Dennis Solas for helpful discussions. The
authors also thank Mr George Detre and Ms Nigar Garizi for
getting SPMAS NMR spectra and Mr Nikhil Shah for mass
spectroscopic assistance.
13. Patel, H. V.; Vyas, K. A.; Pandey, S. P.; Fernandes, P. S.
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