Selective Synthesis of 3-Arylbenzo-1,2,3-triazin-4(3H)-ones and 1-Aryl-(1H)-benzo-1,2,3-triazoles from 1,3-Diaryltriazenes through Pd(0) Catalyzed Annulation Reactions

Article abstract of DOI:10.1021/acs.joc.7b02023

Pd(0) catalyzed carbonylative annulation reaction of 1-(2-iodophenyl)-3-aryltriaz-1-enes in the presence of DABCO and 1 atm of carbon monoxide in toluene at 80 °C gave the corresponding 3-arylbenzo-1,2,3-triazin-4(3H)-ones with high selectivity and in exc

Full text of DOI:10.1021/acs.joc.7b02023

Subscriber access provided by University of Virginia Libraries & VIVA (Virtual Library of Virginia)
Article
Selective synthesis of 3-arylbenzo-1,2,3-triazin-4(3H)-
ones and 1-aryl-(1H)-benzo-1,2,3-triazoles from 1,3-
diaryltriazenes through Pd(0) catalyzed annulation reactions
Attoor Chandrasekhar, and Sethuraman Sankararaman
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b02023 • Publication Date (Web): 06 Oct 2017
Downloaded from http://pubs.acs.org on October 7, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
The Journal of Organic Chemistry is published by the American Chemical Society.
1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 27
The Journal of Organic Chemistry
1
2
3
4
Selective synthesis of 3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones and 1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀ
5
6
triazoles from 1,3ꢀdiaryltriazenes through Pd(0) catalyzed annulation reactions
7
8
9
Attoor Chandrasekhar and Sethuraman Sankararaman*
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
sanka@iitm.ac.in
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
CO
N
O
N
N
N-N-N skeletal CO insertion
1 atmosphere CO
Ar
X = I, Br
6 membered cyclization
X
N
Pd(0), DABCO
toluene
up to 97%
Bromo/iodo triazene CO insertion
Scale up to gram scale
X = I, 24 examples
X = Br, 10 examples
N
Ar
N
H
N2
Ar
Wide substrate scope
Mild reaction conditions
N
N
N
cataytic amount of
CO or PPh3
Abstract
Pd(0) catalyzed carbonylative annulation reaction of 1ꢀ(2ꢀiodophenyl)ꢀ3ꢀaryltriazꢀ1ꢀenes in the
o
presence of DABCO and 1 atmosphere of carbon monoxide in toluene at 80 C gave the
corresponding 3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones with high selectivity and in excellent yields.
Substrate scope of this reaction is demonstrated with 24 examples with various halo, alkyl and
alkoxy substituents on either of the aromatic rings. Bromo substituted triazenes were less
reactive as starting materials towards the carbonylative annulation reaction and yielded 3ꢀ
arylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones in good to moderate yields only in the presence of xantphos
as an additive. In the absence of CO (under N2 atmosphere) the reaction did not proceed and only
starting material was recovered. However, in the presence of catalytic amount of CO or in the
presence of Ph3P in catalytic amounts as additives the reactions proceeded to yield the
corresponding 1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀtriazoles selectively in good yields. Based on control
experiments, a plausible reaction mechanism for the selective formation of 3ꢀarylbenzoꢀ1,2,3ꢀ
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 2 of 27
1
2
3
4
triazinꢀ4(3H)ꢀones in the presence of CO and1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀtriazoles in the absence of
5
6
CO through a common intermediate has been proposed.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Introduction
Benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀone is an important heterocyclic scaffold in medicinal chemistry.
Derivatives of benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀone exhibit a wide variety of biological activities such
as sedative,1 diuretic,2 anesthetic,3 antiarthritic,4 antitubercular5 and antitumor activities.6 The
structures of a few representative examples of biologically active benzoꢀ1,2,3ꢀtriazinꢀ4(3H)-ones
are shown in Figure 1.
Figure 1.Representative examples of biologically active benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones.
Benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones are also useful starting materials in organic synthesis for the
synthesis of isoquinolones by metal catalyzed denitrogenative transannulation reactions with
allenes and alkynes.7 Conventionally benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones were synthesized through a
multistep route from methyl anthranilates and anthranilamides using diazotization of the amino
functional group (Scheme 1).8 Recently an oxidative annulation of 2ꢀaminobenzamides with
nitromethane using tertꢀbutyl hydroperoxide and KI as oxidant9 is reported. Copper catalyzed
ACS Paragon Plus Environment

Page 3 of 27
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Ullmann type coupling of benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones with aryl iodides and aryl boronic
acids has been reported for the synthesis of 3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones.10 Pd catalyzed
denitrogenative carbonylation of aryltriazenes in acidic conditions yields amides.11
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. Literature methods for the synthesis of benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones.
Although transition metal catalyzed carbonylative annulation reaction has been applied to the
synthesis of a variety of heterocyclic scaffolds,12 it has not been applied to the synthesis of
benzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones. Our interest in Pd(0) catalyzed carbonylation reactions13 using
carbon monoxide as a one carbon source led us to the investigation of carbonylative annulation
of 1ꢀ(2ꢀXꢀphenyl)ꢀ3ꢀphenyltriazꢀ1ꢀene (X = Br, I). In general carbon monoxide insertion of CꢀBr
bond requires harsher reaction conditions in comparison to insertion to CꢀI bond and may need
high pressure of CO. Especially, CO insertion between aryl bromide and amine has been
reported at high pressures of carbon monoxide.14 Herein we demonstrate the synthesis of 3ꢀ
arylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones from 1ꢀ(2ꢀbromophenyl)ꢀ3ꢀaryltriazꢀ1ꢀenes (4) under 1
atmosphere CO pressure. Using the carbonylative annulation strategy a facile synthetic method
has been developed for the synthesis of 3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones. Interestingly in the
presence of only catalytic amount of carbon monoxide the reaction led to the formation of 1ꢀarylꢀ
(1H)ꢀbenzoꢀ1,2,3ꢀtriazoles. Cu(I) (via CꢀX activation where X = Br and I)15 and Pd(II) (via CꢀH
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 4 of 27
1
2
activation)16 catalyzed synthesis of 1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀtriazoles from 1,3ꢀdiaryltriazꢀ1ꢀenes
is reported in literature.15,16 A plausible mechanism involving a common intermediate for the
selective formation of either 3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones or 1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀ
triazoles has been proposed.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Results and discussion
Under basic conditions 1,3ꢀdiaryltriazꢀ1ꢀenes undergo facile cis-trans isomerization reaction.17
We anticipated the cis isomer to be particularly useful for Pd(0) catalyzed intramolecular
amination and carbonylative amination reactions to yield 1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀtriazoles and
3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones, respectively. We began our investigation on the
carbonylative annulation with 1ꢀ(2ꢀiodophenyl)ꢀ3ꢀphenyltriazꢀ1ꢀene 1a under 1 atmosphere of
carbon monoxide in presence of Pd(PPh3)2Cl2 in toluene at 80 oC in the presence of Et3N as base
(entry 1, Table 1). Under these conditions 2a was formed in 87%. Reaction also proceeded
smoothly to give 95% of 2a when DABCO was used as the base (entry 4, Table 1). Under these
conditions 3a was not at all formed. The reaction conditions were optimized by screening
various Pd source as catalysts, bases and solvents (Scheme 2, Table 1). All the reactions were
carried out at 80 oC as there was no reaction at room temperature. From entries 2 and 4 (Table 1)
it is evident that both Et3N and DABCO gave good yields of 2a selectively without the formation
of 3a. Surprisingly no reaction was observed when DBU was used as the base (entry 3, Table 1).
When the solvent was changed from toluene to acetonitrile or THF a mixture of 2a and 3a was
formed and the reaction did not proceed at all in DMF (entries 5ꢀ7, Table 1). Both Pd(OAc)2 and
Pd(CH3CN)2Cl2 (entry 8 and 9, Table 1) were ineffective as catalysts for the above
transformation in toluene. When the reaction was carried out with 2 mol% of Pd(PPh3)2Cl2 as
ACS Paragon Plus Environment

Page 5 of 27
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
catalyst the yield of 2a dropped to 80%. From entry 4 it is evident that a combination of
Pd(PPh3)2Cl2 (3 mol%) as the catalyst, DABCO (3 equiv) as base18 and toluene as solvent at 80
oC was most effective for above transformation. Under these conditions 2a is formed with high
selectivity and excellent yield. Therefore subsequent reactions were carried out under these
optimized conditions.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 1: Optimization of reagents and conditions for Pd catalyzed annulation reaction of 1ꢀ(2ꢀ
iodophenyl)ꢀ3ꢀphenyltriazꢀ1ꢀene (1a).
Yield(%)
S.No
Pd sourcea
Base
Et3N
Solvent Time (h)
2a
87
3a
0
1
2
3
4
5
6
7
8
9
PdCl2(PPh3)2
PdCl2(PPh3)2
PdCl2(PPh3)2
PdCl2(PPh3)2
PdCl2(PPh3)2
PdCl2(PPh3)2
PdCl2(PPh3)2
Pd(OAc)2
toluene
24
36
36
15
24
36
15
36
36
pyridine toluene
DBU toluene
trace
0
NRb NRb
DABCO toluene
DABCO CH3CN
95
60
40
0
30
DABCO
DABCO
THF
15
DMF
NRb NRb
DABCO toluene
25
0
0
PdCl2(CH3CN)2 DABCO toluene
trace
Reaction conditions: a1a (0.5 mmol), Pd cat (3.0 mol%), base (3 equiv), solvent (4 mL)
bNR = no reaction
The scope of substrates is amply demonstrated by varying the substituents on both the aryl rings.
From the data presented in Scheme 2 the following conclusions can be drawn. Both electron
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 27
1
2
3
4
5
6
7
8
9
donating groups (methoxy, methyl and tꢀbutyl) as well as electron withdrawing groups (fluoro,
chloro, bromo and iodo) are tolerated in the 3ꢀaryl ring. Substrates with electron donating groups
reacted faster than the ones with electron withdrawing substituents. Ortho and para methyl
substituents on 3ꢀaryl ring (1b and 1c) showed considerable rate difference. While para methyl
substituted substrate 1c took 8 h for the completion of the reaction to give 90% of triazinone 2c,
under similar conditions ortho methyl substituted substrate 1b reacted within 4 h to give 92% of
triazinone 2b. Similarly ortho halo substituted triazenes reacted faster than para substituted halo
triazenes. Ortho substituted derivatives are sterically more hindered and hence reacted faster
perhaps due to the increased rate of reductive elimination step of the reaction. Diiodo substituted
triazene 1x also reacted cleanly with carbon monoxide under optimized reaction conditions to
give mono iodotriazinone 2x in moderate yield. The products (2a-x) were thoroughly
characterized by spectroscopic data. In addition, the structures of 2q and 2w were established
unequivocally by single crystal Xꢀray data (SI).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

Page 7 of 27
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Reaction conditions: 1 (0.5 mmol), PdCl2(PPh3)2 (3 mol%), DABCO (3 equiv),
toluene (4 mL).
Scheme 2. Pd catalyzed carbonylative annulation of 1ꢀ(2ꢀiodophenyl)ꢀ3ꢀphenyltriazꢀ1ꢀene.
In order to make the methodology more versatile, carbonylative annulation of 1ꢀ(2ꢀ
bromophenyl)ꢀ3ꢀaryltriazꢀ1ꢀenes (4a-k) to the corresponding 3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀ
ones was investigated (Table 2). Firstly 1ꢀ(2ꢀbromophenyl)ꢀ3ꢀphenyltriazꢀ1ꢀene 4a was treated
with CO under optimized reaction conditions of Table 1, yield of the desired product 2a was
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 8 of 27
1
2
3
4
5
6
7
8
9
only 12 % after prolonged reaction for 72 h. (Table 2). When the reaction was carried out with
10 mol% of Pd catalyst yield of 2a improved slightly. Further addition of mono and biꢀdentate
ligands such as PPh3 and 1,2ꢀbis(diphenylphosphino)ethane (dppe) (entries 3ꢀ5, Table 2) did not
improve the yield of 2a. However, when reaction was carried out in the presence of xantphos as
ligand the desired product 2a was obtained in 60% within 26 h. Only trace amount of 2a was
obtained when Pd(OAc)2 was used as the catalyst. Under optimized reaction conditions (entry 6,
Table 2) scope of substrates was demonstrated and results are listed in Table 3. 2ꢀ
Bromotriazenes substituted both at the ortho and para positions on the 3ꢀphenyl ring were
tolerated under optimized reaction conditions and yielded the corresponding triazinones (2b-c,
2f-g, 2h-i) in good to moderate yields. Ortho substituted derivatives reacted faster and gave
better yields of the corresponding triazinones (2) compared to the para substituted derivatives.
Surprisingly the desired product 2y was not observed in case of 1ꢀ (2ꢀbromophenyl)ꢀ3ꢀ(3ꢀ
chlorophenyl)triazꢀ1ꢀene (4y), the only product obtained was triazole 3y in 56 % yield. In case of
triazene 4z the expected carbonylated product was obtained in 35% yield.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

Page 9 of 27
The Journal of Organic Chemistry
1
2
3
4
Table 2: Reaction optimization for Pd catalyzed carbonylation of 1ꢀ(2ꢀbromophenyl)ꢀ3ꢀ
5
6
phenyltriazꢀ1ꢀene.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Entry Pd catalysta
base
Ligand
ꢀ
Time(h) Yield(%)
1
2
3
4
5
6
7
bPdCl2(PPh3)2 DABCO
PdCl2(PPh3)2 DABCO
PdCl2(PPh3)2 DABCO
PdCl2(PPh3)2 DABCO
72
72
72
68
72
26
26
12
23
ꢀ
PPh3
dppe
dppe
31
30
PdCl2(PPh3)2
K2CO3
0
PdCl2(PPh3)2 DABCO xantphos
Pd(OAc)2 DABCO xantphos
60
trace
Reaction conditions: a4a (0.5 mmol), Pd cat (10 mol%), ligand (10 mol%) base (3 equiv),
solvent (3 mL), b3 mol% of PdCl2(PPh3)2.
Table 3: Pd catalyzed carbonylative annulation of bromotriazene (4) derivatives.
Entrya
R1
R2
R3 Time 2, Yield
4
(h)
26
18
24
20
26
22
28
26
(%)
1
2
3
4
5
6
7
8
H
H
H
2ꢀ Me
4ꢀMe
2ꢀF
H
H
H
H
H
H
H
H
2a, 60
2b, 79
2c, 62
2f, 58
2g, 55
2h, 71
2i, 51b
2n, 51
4a
4b
4c
4f
H
H
H
4ꢀF
4g
4h
4i
H
2ꢀCl
4ꢀCl
H
H
Me
4n
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 10 of 27
1
2
3
4
5
6
7
8
9
Me
H
4ꢀCl
H
H
26
28
2v, 53b
2y, 0b,
3y, 56c
2z, 35b
4v
4y
10
Cl
11
H
2ꢀ Me Me
24
4z
Reaction conditions: a 4 (0.5 mmol), PdCl2(PPh3)2 cat (10 mol%),
ligand (10 mol%), DABCO (3 equiv), toluene (3 mL), b PdCl2
was used, c nonꢀcarbonylated product, triazole 3y was obtained.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
To examine the efficiency of the carbonylation reaction in gram scale, the reaction was carried
out with 1.1 g (3.4 mmol) of 1ꢀ(2ꢀiodophenyl)ꢀ3ꢀphenyltriazꢀ1ꢀene 1a and desired product 2a
obtained in 92% yield (Scheme 3).
Scheme 3: Synthesis of 2a in gram scale reaction
In order to understand the reaction mechanism the following control experiments were carried
out. When 1a, 1e and 1h were reacted separately in the absence of carbon monoxide (under N2
atmosphere) but otherwise under identical conditions as in Scheme 2, only starting materials
were recovered after 48 h (Scheme 4). The anticipated amination products 3a, 3e and 3h,
respectively, were not formed under these reaction conditions. However, when the reaction of 1a
was carried out in THF and acetonitrile the anticipated benzotriazole derivative 3a was formed in
moderate yield.
ACS Paragon Plus Environment

Page 11 of 27
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 4. Effect of solvent polarity on the formation of benzotriazoles in the absence of CO.
In another set of experiments several iodoꢀ1,3ꢀdiaryltriazenes (1) were reacted separately under
optimized conditions with 10 mol% of PPh3 as an additive. In the presence of PPh3 as an additive
the reaction proceeded smoothly to yield the anticipated amination products, namely the
triazoles, (3) in good yields (Scheme 5).
Scheme 5. Effect of PPh3 as additive in the absence of CO towards formation of benzotriazole
derivatives.
Scheme 6. Effect of catalytic amount of CO towards formation of benzotriazole derivatives.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 12 of 27
1
2
3
4
5
6
7
8
9
The effect of CO, solvent polarity and PPh3 as additive in the formation of benzotriazoles was
studied. The results of this study are summarized in Table 4. The reaction of 1a and 1b in the
absence of PPh3 and in the presence of catalytic amount of CO (20 mL of CO was taken in a
syringe and bubbled into the reaction mixture) under otherwise conditions identical to Scheme 2,
proceeded to furnish 3a and 3b in 20% and 40% yields respectively in 10 h (Scheme 6). From
these experiments we conclude that CO acts as the reducing agent in toluene and reduces Pd(II)
to Pd(0)19 which is the catalytically active species. In toluene DABCO does not reduce for Pd(II)
to Pd(0). However in acetonitrile and THF the reaction proceeded in the absence of CO
indicating that solvent polarity plays a major role in forming the catalytically active Pd(0). In
toluene either catalytic amount of PPh3 or CO was necessary as additives (as reducing agent for
Pd(II)) and perhaps as stabilizing ligands for the formation of catalytically active Pd(0) and
under these conditions the reaction proceeded to give benzotriazole derivatives (3) as the sole
product (Table 4).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 4. Effect of CO, solvent polarity and PPh3 as additive in the formation of benzotriazoles
entry substratea
CO
absent
PPh3
absent
absent
absent
absent
absent
solvent Time(h) Yield(%)
1
2
toluene
toluene
toluene
THF
48
48
48
48
48
24
10
18
10
10
NR
1a
1e
1h
1a
1a
1a
1b
1c
1a
1b
absent
NR
3
absent
NR
4
absent
3a, 55
3a, 62
3a, 73
3b, 85
3r, 55
3a, 20
3b, 40
5
absent
CH3CN
6
absent
10 mol% toluene
10 mol% toluene
10 mol% toluene
7
absent
8
absent
9
cat. amountb
cat. amountb
absent
absent
toluene
toluene
10
ACS Paragon Plus Environment

Page 13 of 27
The Journal of Organic Chemistry
1
2
3
4
5
Reaction conditions: : a 1 (0.5 mmol), PdCl2(PPh3)2 (10 mol%), solvent 3 mL,
b20 mL of CO added from a syringe.
6
7
8
9
Based on the above observations a plausible mechanism for the formation of benzoꢀ1,2,3ꢀtriazinꢀ
4(3H)ꢀones (2) in the presence of CO and (1H)ꢀbenzoꢀ1,2,3ꢀtriazoles (3) in catalytic amount of
CO is proposed (Scheme 7). According to literature20 1,3ꢀdiaryltriazene can undergo cis-trans
isomerization under basic conditions. Subsequently the cis isomer undergoes oxidative addition
to in situ generated Pd (0) to produce intermediate I (Scheme 7). The fact that in the presence of
CO, benzotriazinone 2 was formed with high selectivity indicates that intermediate I in the
catalytic cycle is effectively trapped by CO through insertion reaction. The rate of CO insertion
with intermediate I must be much faster than the alternative route of PdꢀN bond formation
leading to the formation of intermediate IV. Thus I serves as a common intermediate for the
formation of 2 and 3 and the presence or absence of CO controls, respectively the rate of CO
insertion to form II vs the rate of PdꢀN bond formation to intermediate IV. In the case of Pd
catalyzed CO insertion of bromotriazenes 4 metal catalyst may get additional stability in
presence of xantphos and undergoes oxidative addition21 with triazene 4 and subsequent reaction
of CO followed by reductive elimination of metal produces CO inserted annulated product 2.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 7. Catalytic cycle for the formation of 2 and 3
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 14 of 27
1
2
3
4
Conclusion
5
6
7
8
A new methodology based on Pd(0) catalyzed carbonylative amination of 1ꢀ(2ꢀXꢀphenyl)ꢀ3ꢀ
aryltriazꢀ1ꢀenes (X = Br and I) (1) has been developed for the synthesis of the corresponding 3ꢀ
arylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones (2) with high selectivity and in excellent yields under 1
atmosphere of carbon monoxide. The substrate scope for this reaction is amply demonstrated
with 24 examples. The less reactive bromo derivatives required catalytic amount of xantphos as
ligand for the reaction to proceed to yield 2. No reaction was observed in the absence of CO
(under N2 atmosphere). However, in the presence of catalytic amount of either CO or
triphenylphosphine the reaction of 1 proceeded to give the corresponding benzotriazoles (3) in
good yields. Thus the methodology developed in the present study allows the synthesis of either
3ꢀarylbenzoꢀ1,2,3ꢀtriazinꢀ4(3H)ꢀones (2) or 1ꢀarylꢀ(1H)ꢀbenzoꢀ1,2,3ꢀtriazoles (3) in a highly
selective manner. Based on some control experiment a mechanism involving a common
intermediate (I in Scheme 7) for the formation of 2 and 3 is proposed.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Experimental section:
General Procedure for Synthesis of Triazenes (1a-1x, 4)
All the triazenes (1a-1x, 4) were synthesized as follows according to reported procedure16 with
minor changes. To a stirred solution of water (7 mL) and conc. HCl (0.7 mL) in 50 mL round
bottom was added 2ꢀhaloaniline (1 mmol) at room temperature. The resulting mixture was
o
cooled to 0 C and then an ice cold solution of NaNO2 (1 equiv) in water (3 mL) was added.
After reaction mixture was stirred for 10 min at same temperature was added partner aniline drop
o
wise and the mixture was allowed to stir for 15 min at 0 C. To the resulting clear solution
(where partner aniline was not completely soluble acetone (1 mL)was added until it became clear
ACS Paragon Plus Environment

Page 15 of 27
The Journal of Organic Chemistry
1
2
3
4
solution) a solution of sodium acetate (1.5 g) in water (6 mL) was added and stirring was
5
6
o
continued for next 1h at 0 C.The resulting precipitate was filtered through a buchner funnel,
7
8
9
washed with ice cold water 3 times and then dried at room temperature. The solid triazenes (1aꢀ
1x, 4aꢀ4k) thus obtained were used in further reactions without any purification.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
General procedure for the synthesis of benzo-1,2,3-triazine-4-ones (2) from 2-iodotriazenes
(1)
To a 10 mL oven dried schlenk round bottom flask kept under N2 atmosphere was added
PdCl2(PPh3)2 (3 mol%, 11 mg) and triazene (1) (0.5 mmol) followed by DABCO (1.5 mmol, 168
mg) then toluene (4 mL). The reaction mixture was flushed 3 times with CO from a balloon and
stirred at 80 oC under CO (1 atm). Progress of the reaction was monitored by TLC. After stirring
for the required period of time (see Scheme 2), the reaction mixture was cooled to room
temperature and passed through a celite pad, washed with CH2Cl2. The combined filtrate was
concentrated under vacuum and the crude product thus obtained was purified by column
chromatography on silica gel.
General procedure for Synthesis of benzo-1,2,3-triazine-4(3H)-ones (2) from
bromotriazenes (4). To an oven dried schlenk reaction tube kept under N2 atmosphere was
added Pd(PPh3)2(Cl)2 catalyst (10 mol%), triazene (4) (0.5 mmol), DABCO (1.5 mmol, 168 mg)
followed by xantphos (10 mol%, 29 mg) then toluene (3 mL). The reaction mixture was flushed
o
3 times with CO from a balloon and stirred at 90 C under CO (1 atm). Progress of the reaction
was monitored by TLC. After stirring for the required period of time (Scheme3), the reaction
mixture was cooled to room temperature and passed through a celite pad, washed with CH2Cl2.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 16 of 27
1
2
3
4
5
6
The combined filtrate was concentrated under vacuum and crude product was purified by column
chromatography on silica gel.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Synthesis of 2a in gram scale reaction:
To a 50mL oven dried schlenk round bottom flask kept under N2 atmosphere was added
PdCl2(PPh3)2 (5 mol%, 120 mg) and triazene (1a) (3.4 mmol, 1.1 g) followed by DABCO (10.2
mmol, 1.15 g) then toluene (18 mL). Reaction mixture was flushed 3 times with CO from a
balloon and stirred at 80 oC under CO (1 atm) for 15h. Progress of the reaction was monitored by
TLC. Reaction mixture was cooled to room temperature and passed through a celite pad, washed
with CH2Cl2. The combined filtrate was concentrated under vacuum and crude the product was
purified by column chromatography on silica gel. 2a was obtained in 92% yield (700 mg).
3-Phenylbenzo-1,2,3-triazin-4(3H)-one (2a)9 :
o
o
1
White solid, yield 105 mg (95%), mp 129 C (lit. 127ꢀ129 C), H NMR (400 MHz, CDCl3): δ
8.44 (dd, J = 8 , 1.2 Hz, 1H), 8.22 (d, J = 8 Hz, 1H), 7.98 (dt, J = 7.2, 1.2 Hz, 1H), 7.86ꢀ7.82 (m,
13
1H), 7.67ꢀ7.64 (m, 2H), 7.57ꢀ7.54 (m, 2H), 7.51ꢀ7.47 (m, 1H); C NMR (100 MHz, CDCl3 ): δ
155.3, 143.8, 138.9, 135.2, 132.8, 129.1, 129.0, 128.6, 126.1, 125.7, 120.5; IR (KBr): cmꢀ1 1680;
HRMS (ESI, m/z) Calcd for C13H9N3ONa 246.0643 (M+Na), found 246.0667.
3-(2-Methylphenyl)benzoꢀ1,2,3-triazin-4(3H)-one (2b)9 :
o
o
1
Pale yellow solid, yield 109 mg, (92%), mp 151 C (lit. 153ꢀ155 C), H NMR (500 MHz,
CDCl3): δ 8.44 (dd, J = 1, 7.5 Hz, 1H), 8.25 (d, J = 8 Hz, 1H), 8.01 (dt, J = 1.5, 7.5 Hz, 1H),
7.87ꢀ7.84 (m, 1H), 7.46ꢀ7.36 (m, 4H), 2.20 (s, 3H); 13C NMR (125 MHz, CDCl3): δ 155.2,
144.1, 137.9, 135.6, 135.2, 132.8, 131.3, 130.0, 128.7, 127.8, 127.1, 125.7, 120.4, 17.8.
ACS Paragon Plus Environment

Page 17 of 27
The Journal of Organic Chemistry
1
2
3-(4-Methylphenyl)benzo-1,2,3-triazin-4(3H)-one (2c)9 :
3
4
5
6
o
o
1
White solid, yield 106 mg, (90%), mp 139 C (lit. 139ꢀ141 C), H NMR (400 MHz, CDCl3): δ
7
8
9
8.43 (d, J = 8 Hz, 1H), 8.21 (d, J = 8.4 Hz, 1H), 7.98 (t, J = 7.6 Hz, 1H), 7.83(t, J = 7.2 Hz, 1H),
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13
7.52 (d, J = 8.4 Hz, 2H), 7.35 (d, J = 8 Hz, 2H), 2.44 (s, 3H); C NMR (100 MHz, CDCl3): δ
155.4, 143.8, 139.1, 136.4, 135.1, 132.7, 129.8, 128.5, 125.9, 125.7, 120.5, 21.3.
3-(4-tert-Butylphenyl)benzo-1,2,3-triazin-4(3H)-one (2d)9 :
o
o
1
White crystalline solid, yield 135 mg, (97%), mp 148 C (lit. 144ꢀ146 C), H NMR (500 MHz,
CDCl3): δ 8.44 (td, J = 1, 8 Hz, 1H), 8.21 (d, J = 8 Hz, 1H), 8.00ꢀ7.96 (m, 1H), 7.85 ꢀ 7.82 (m,
1H), 7.57 (s, 4H), 1.38 (s, 9H); 13C NMR (125 MHz, CDCl3) : δ 155.4, 152.2, 143.8, 136.3,
135.1, 132.7, 128.5, 126.2, 125.7, 125.6, 120.5, 34.9, 31.4.
3-(4-Methoxyphenyl)benzo-1,2,3-triazin-4(3H)-one (2e)9 :
o
o
1
Pale yellow solid, yield 118 mg (94%), mp 148 C (lit. 151ꢀ153 C), H NMR (400 MHz,
CDCl3): δ 8.42 (dd, J = 0.8, 8.8 Hz, 1H), 8.20 (d, J = 8.4 Hz, 1H), 7.97 (dt, J = 1.2, 7.2 Hz, 1H),
13
7.85ꢀ7.81 (m, 1H), 7.56 and 7.05 (AA’BB’ pattern J = 8.8, 9.2 Hz, 4H), 3.87 (s, 3H); C NMR
(100 MHz, CDCl3): δ 159.9, 155.5, 143.8, 135.1, 132.7, 131.8, 128.5, 127.4, 125.7, 120.5, 114.4,
55.7.
3-(2-Fluorophenyl)benzo-1,2,3-triazin-4(3H)-one (2f)22 :
Off white solid, yield 104 mg, (87%), mp 132 C, 1H NMR (500 MHz, CDCl3): δ 8.44 (dd, J =
o
1.5, 8 Hz, 1H), 8.25ꢀ8.23 (m, 1H), 8.03ꢀ7.99 (m, 1H), 7.88ꢀ7.85 (m, 1H), 7.57ꢀ7.50 (m, 2H),
7.37ꢀ7.29 (m, 2H); 13C NMR (125 MHz, CDCl3): δ 158.4, 156.4, 154.9, 143.8, 135.4, 133.1,
131.58, 131.52, 129.1, 128.8, 126.7, 126.6, 125.7, 124.93, 124.90, 120.3, 116.9, 116.8.
3-(4-Fluorophenyl)benzo-1,2,3-triazin-4(3H)-one (2g)22 :
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 18 of 27
1
2
o
o
White crystalline solid, yield 93 mg (78%), mp 147 C (lit. 151ꢀ153 C), 1H NMR (400 MHz,
CDCl3): δ 8.44 (dd, J = 0.4, 7.6 Hz, 1H), 8.23 (d, J = 8.4 Hz, 1H), 8.02ꢀ7.98 (m, 1H), 7.88ꢀ7.84
(m, 1H), 7.66ꢀ7.63 (m, 2H), 7.26ꢀ7.22 (m, 2H); 13C NMR (100 MHz, CDCl3): δ 155.4, 143.7,
135.3, 133.0, 128.7, 128.1, 128.0, 125.7, 120.4, 116.2, 116.0.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3-(2-Chlorophenyl)benzo-1,2,3-triazin-4(3H)-one (2h)7 :
Pale yellow solid, yield 107 mg (84%), mp 110 oC, 1H NMR (500 MHz, CDCl3): δ 8.46ꢀ8.44 (m,
1H), 8.26ꢀ8.25 (m, 1H), 8.04ꢀ8.00 (m, 1H), 7.89ꢀ7.85 (m, 1H), 7.63ꢀ7.61 (m, 1H), 7.54ꢀ7.48 (m,
3H); 13C NMR (125 MHz, CDCl3): δ 155.0, 143.9, 136.6, 135.4, 133.0, 132.4, 131.2, 130.6,
129.6, 128.8, 127.9, 125.7, 120.4.
3-(4-Chlorophenyl)benzo-1,2,3-triazin-4(3H)-one (2i)9 :
o
o
White solid, yield 104 mg, (82%), mp 176 C (lit. 178ꢀ180 C), 1H NMR (500 MHz, CDCl3): δ
8.43 (dd, J = 1, 7.5 Hz, 1H), 8.22 (d, J = 8 Hz, 1H), 8.01ꢀ7.98 (m, 1H), 7.87ꢀ7.84 (m, 1H), 7.63
and 7.52 (AA’BB’ pattern J = 9, 9 Hz, 4H); 13C NMR (125 MHz, CDCl3): δ 155.2, 143.7, 137.3,
135.3, 134.9, 133.0, 129.3, 128.7, 127.3, 125.8, 120.3.
3-(2-Bromophenyl)benzo-1,2,3-triazin-4(3H)-one (2j):
Yellow solid, yield 105 mg, (70%), mp 110 oC, 1H NMR (400 MHz, CDCl3): δ 8.45 (dd, J = 7.6,
1.2 Hz 1H), 8.26 (d, J = 8 Hz, 1H), 8.04ꢀ8.00 (m, 1H), 7.89ꢀ7.85 (m, 1H), 7.80 (d, J = 8 Hz, 1H),
7.54ꢀ7.51 (m, 2H), 7.44ꢀ 7.40 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 155.0, 144.0, 138.2,
135.4, 133.7, 133.0, 131.4, 129.8, 128.9, 128.6, 125.8, 122.3, 120.5; IR (KBr): cmꢀ1 1695;
HRMS (ESI, m/z) Calcd for C13H9N3OBr 301.9929 (M+H), found 301.9904.
3-(4-Bromophenyl)benzo-1,2,3-triazin-4(3H)-one (2k) :
White crystalline solid, yield 128 mg, (85%), mp 187 oC, 1H NMR (400 MHz, CDCl3): δ 8.43 (d,
J = 7.6 Hz, 1H), 8.22 (d, J = 8 Hz, 1H), 8.00 (t, J = 7.2 Hz, 1H), 7.86 (t, J = 7.2 Hz, 1H), 7.86 (d,
ACS Paragon Plus Environment

Page 19 of 27
The Journal of Organic Chemistry
1
2
13
3
4
J = 7.2 Hz, 2H), 7.57 (d, J = 7.2 Hz, 2H); C NMR (100 MHz, CDCl3): δ 155.2, 143.7, 137.8,
5
6
7
8
135.4, 133.1, 132.3, 128.7, 127.6, 125.8, 122.9, 120.3; IR (KBr): cmꢀ1 1693; HRMS (ESI, m/z)
Calcd for C13H8N3OBrNa 323.9627 (M+Na), found 323.9637.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
6-Chloro-3-phenylbenzo-1,2,3-triazin-4(3H)-one (2l)9 :
o
o
1
Pale yellow solid, yield 100 mg (81%), mp 175 C (lit. 175ꢀ177 C), H NMR (400 MHz,
CDCl3): δ 8.40 (d, J = 2.4 Hz, 1H), 8.17 (d, J = 8.8 Hz, 1H), 7.92 (dd, J = 2.4, 8.8 Hz, 1H), 7.65ꢀ
7.63 (m, 2H), 7.58ꢀ7.56 (m, 2H), 7.52ꢀ7.48 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 154.3,
142.1, 139.3, 138.6, 135.8, 130.3, 129.3, 129.2, 126.1, 125.3, 121.7.
3-(4-tert-Butylphenyl)-6-chlorobenzo-1,2,3-triazin-4(3H)-one (2m) :
o
Pale orange solid, yield 124 mg, (80%), mp 161 C, 1H NMR (500 MHz, CDCl3): δ 8.40 (d, J =
1.6 Hz, 1H), 8.16 (d, J = 6.8 Hz, 1H), 7.91 (dd, J = 6.8, 2 Hz 1H), 7.59ꢀ7.54 (m, 4H), 1.38 (s ,
9H); 13C NMR (125MHz, CDCl3): δ 154.3, 152.4, 142.2, 139.2, 136.0, 135.7, 130.2, 126.3,
125.5, 125.3, 121.7, 34.9, 31.4; IR (KBr): cmꢀ1 1686; HRMS (ESI, m/z) Calcd for C17H17N3OCl
314.1060 (M+H), found 314.1063.
6-Methyl-3-phenylbenzo-1,2,3-triazin-4(3H)-one (2n)9:
o
1
White crystalline solid, yield 105 mg (89%), mp 155 C (lit. 151ꢀ153oC), H NMR (400 MHz,
CDCl3): δ 8.22 (s , 1H), 8.10 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 8.4 Hz, 1H), 7.65 (d, J = 7.6 Hz,
13
2H), 7.55 (t, J = 7.6 Hz, 2H), 7.50ꢀ7.46 (m, 1H), 2.60 (s, 3H); C NMR (100 MHz, CDCl3): δ
155.5, 144.2, 142.1, 139.0, 136.5, 129.1, 128.9, 128.5, 126.2, 125.1, 120.3, 22.0.
6-Methyl-3-(2-methylphenyl)benzo-1,2,3-triazin-4(3H)-one (2o):
Off white solid, 103 mg, (83%), mp 126 oC, 1H NMR (400 MHz, CDCl3): δ 8.22 (d, J = 0.4 Hz,
1H), 8.13 (d, J = 8.4 Hz, 1H), 7.80 (dd, J = 8.4, 1.6 Hz, 1H), 7.45ꢀ7.35 (m, 4H), 2.60 (s, 3H),
2.19 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 155.4, 144.2, 142.5, 138.1, 136.5, 135.6, 131.2,
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 20 of 27
1
2
129.9, 128.6, 127.8, 127.1, 125.0, 120.3, 22.0, 17.8; IR (KBr): cmꢀ1 1688; HRMS (ESI, m/z)
Calcd for C15H13N3ONa 274.0956 (M+Na), found 274.0962.
3
4
5
6
7
8
9
6-Methyl-3-(4-methylphenyl)benzo-1,2,3-triazin-4(3H)-one (2p):
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
o
White crystalline solid, yield 116 mg (93%), mp 144 C, 1H NMR (400 MHz, CDCl3): δ 8.21 (s,
1H), 8.09 (d, J = 8.4 Hz, 1H), 7.77 (dd, J = 8, 1.2 Hz, 1H), 7.51 (d, J = 8 Hz, 2H), 7.34 (d, J = 8
13
Hz, 2H), 2.59 (s, 3H), 2.44 (s, 1H); C NMR (100 MHz, CDCl3): δ 155.6, 144.0, 142.2, 139.0,
136.5, 136.4, 129.7, 128.4, 126.0, 125.1, 120.3, 22.0, 21.3; ; IR (KBr): cmꢀ1 1680; HRMS (ESI,
m/z) Calcd for C15H13N3ONa 274.0956 (M+Na), found 274.0942.
3-(4-tert-Butylphenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2q):
o
1
White solid, yield 118 mg (81%), mp 184 C, H NMR (500 MHz, CDCl3): 8.22 (s, 1H), 8.10
13
(d, J = 6.8 Hz, 1H), 7.78 (dd, J = 6.8, 0.4 Hz, 1H), 7.56 (s, 4H), 2.60 (s, 3H), 1.38 (s, 9H); C
NMR (125 MHz, CDCl3): δ 155.6, 152.1, 144.0, 142.2, 136.4, 128.5, 126.2, 126.1, 125.6, 125.1,
120.3, 34.9, 31.4, 22.0; IR (KBr): cmꢀ1 1689; HRMS (ESI, m/z) Calcd for C18H20N3O 294.1606
(M+H), found 294.1617.
3-(4-Methoxyphenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2r):
o
1
Off white solid, yield 125 mg (94%), mp 152 C, H NMR (400 MHz, CDCl3): δ 8.21 (s, 1H),
8.09 (d, J = 8 Hz, 1H), 7.55 and 7.05 (AA’BB’ pattern, J = 9.2 Hz, 8.8 Hz, 4H). 7.77 (dd, J =
13
8.4, 2 Hz, 1H), 3.87 (s, 3H), 2.59 (s, 3H); C NMR (100 MHz, CDCl3): δ 159.9, 155.6, 144.0,
142.2, 136.4, 131.9, 128.4, 127.4, 125.1, 120.3, 114.3, 55.7, 22.0; IR (KBr): cmꢀ1 1680; HRMS
(ESI, m/z) Calcd for C15H13N3O2Na 290.0905 (M+Na), found 290.0912.
3-(2-Fluorophenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2s):
Pale orange solid, yield 115 mg (91%), mp 133 C, 1H NMR (400 MHz, CDCl3): δ 8.22 (s, 1H),
o
8.12 (d, J = 8 Hz, 1H), 7.80 (d, J = 8 Hz, 1H), 7.57ꢀ7.49 (m, 2H), 7.36ꢀ7.26 (m, 2H), 2.60 (s,
ACS Paragon Plus Environment

Page 21 of 27
The Journal of Organic Chemistry
1
2
3H); 13C NMR (100 MHz, CDCl3): δ 158.7, 156.2, 155.1, 144.4, 142.2, 136.6, 131.4, 131.3,
129.1, 128.7, 126.8, 125.1, 124.89, 124.86, 120.1, 116.9, 116.7, 22.0; IR (KBr): cmꢀ1 1693;
HRMS (ESI, m/z) Calcd for C14H10N3OFNa 278.0706 (M+Na), found 278.0685.
3-(4-Fluorophenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2t):
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
o
White solid, yield 113 mg (89%), mp 156 C, 1H NMR (400 MHz, CDCl3): δ 8.21 (s, 1H), 8.11
13
(d, J = 8.4 Hz, 1H), 7.81ꢀ7.78 (m, 1H), 7.66ꢀ7.61 (m, 2H), 7.26ꢀ7.21 (m, 2H); C NMR (100
MHz, CDCl3): δ 163.8, 161.4, 155.5, 144.4, 142.1, 136.6, 135.0, 128.6, 128.1, 128.0, 125.1,
120.2, 116.2, 116.0; IR (KBr): cmꢀ1 1694; HRMS (ESI, m/z) Calcd for C14H10N3OFNa 278.0706
(M+Na), found 278.0692.
3-(2-Chlorophenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2u):
o
1
Pale yellow solid, yield 98 mg (73%), mp 152 C, H NMR (400 MHz, CDCl3): δ 8.23 (s, 1H),
8.13 (d, J = 8 Hz, 1H), 7.81 (dd, J = 8.4, 1.6 Hz, 1H), 7.62ꢀ7.60 (m, 1H), 7.54ꢀ7.47 (m, 3H), 2.60
13
(s, 3H); C NMR (100 MHz, CDCl3): δ 155.2, 144.4, 142.3, 136.7, 136.6, 132.5, 131.1, 130.5,
129.7, 128.7, 127.9, 125.2, 120.2, 22.0; IR (KBr): cmꢀ1 1694; HRMS (ESI, m/z) Calcd for
C14H10N3OCl 294.0410 (M+Na), found 294.0430.
3-(4-Chlorophenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2v):
o
1
White solid, yield 110 mg (82%), mp 192 C, H NMR (400 MHz, CDCl3): δ 8.21(s, 1H), 8.10
(d, J = 8 Hz, 1H), 7.79 (dd, J = 8.4, 1.6 Hz, 1H), 7.62 (d, J = 8.8 Hz, 2H), 7.51 (d, J = 8.8 Hz,
2H), 2.60 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 155.4, 144.4, 142.0, 137.5, 136.6, 134.8,
129.3, 128.6, 127.3, 125.1, 120.2, 22.1; IR (KBr): cmꢀ1 1695; HRMS (ESI, m/z) Calcd for
C14H10N3OClNa 294.0410 (M+Na), found 294.0428.
3-(2-Bromophenyl)-6-methylbenzo-1,2,3-triazin-4(3H)-one (2w):
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 22 of 27
1
2
o
Brown solid, yield 112 mg (71%), mp 142 C, 1H NMR (400 MHz, CDCl3): δ 8.23 (dd, J = 1.2,
3
4
5
6
7
8
0.4 Hz, 1H), 8.14 (d, J = 8.4 Hz, 1H), 7.83ꢀ7.78 (m, 2H), 7.53ꢀ7.51 (m, 2H), 7.43ꢀ7.39 (m, 1H),
2.60 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 155.1, 144.4, 142.3, 138.3, 136.7, 133.7, 131.3,
129.8, 128.8, 128.6, 125.2, 122.4, 120.3, 22.0; IR (KBr): cmꢀ1 1694; HRMS (ESI, m/z) Calcd for
C14H11N3OBr 316.0085 (M+H), found 316.0086.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3-(2-Iodophenyl)benzo-1,2,3-triazin-4(3H)-one (2x):
o
1
White solid, yield 84 mg (62%), mp 175 C, H NMR (400 MHz, CDCl3): δ 8.47ꢀ8.45 (m, 1H),
8.27 (d, J = 8.4 Hz, 1H), 8.05ꢀ8.01 (m, 2H), 7.90ꢀ7.86 (m, 1H), 7.59ꢀ7.54 (m, 1H), 7.50ꢀ7.48 (m,
1H), 7.28ꢀ7.24 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 154.9, 144.1, 141.6, 140.1, 135.4,
133.0, 131.4, 129.6, 129.2, 128.9, 125.8, 120.6, 97.5; IR (KBr): cmꢀ1 1694; HRMS (ESI, m/z)
Calcd for C13H8N3OINa 371.9610 (M+Na), found 371.9595.
3-(2,5-Dimethylphenyl)benzo-1,2,3-triazin-4(3H)-one (2z):
White solid, yield 44mg (35%), mp 126 oC, 1H NMR (500 MHz, CDCl3): δ 8.44 (dd, J = 1, 8 Hz,
1H), 8.25 (d, J = 8 Hz, 1H), 8.02ꢀ7.99 (m, 1H), 7.87ꢀ7.84 (m, 1H), 7.30ꢀ7.24 (m, 2H), 7.19 (s,
1H), 2.39 (s, 3H), 2.15 (s, 3H); 13C NMR (125 MHz, CDCl3): δ 155.3, 144.1, 137.7, 137.0,
135.2, 132.8, 132.3, 131.1, 130.8, 128.6, 128.2, 125.7, 120.4, 20.9, 17.3; IR (KBr): 1680 cmꢀ1 ;
HRMS (ESI, m/z) Calcd for C15H13N3ONa 274.0956 (M+Na), found 274.0928.
1-Phenyl-(1H)-benzo-1,2,3-triazole (3a)23 :
o
1
White solid, yield 71 mg (73%), mp 93 C (lit. 90ꢀ92oC), H NMR (400 MHz, CDCl3): δ 8.14
(AA’BB’ pattern J = 8.4, 1H), 7.80ꢀ7.73 (m, 3H), 7.63ꢀ7.59 (m, 2H), 7.56ꢀ7.48 (m, 2H),7.45ꢀ
7.41(m, 1H); 13C NMR (100 MHz, CDCl3): δ 146.6, 137.1, 132.4, 129.9, 128.7, 128.3, 124.5,
123.0, 120.4, 110.4.
1-(2-Methylphenyl)-(1H)-benzo-1,2,3-triazole (3b)23 :
ACS Paragon Plus Environment

Page 23 of 27
The Journal of Organic Chemistry
1
2
o
1
White solid, yield 89 mg, (85%), mp 61 C (lit. 60ꢀ63oC), H NMR (400 MHz, CDCl3): δ 8.15
3
4
5
6
13
(AA’BB’ pattern J = 8.4, 1H), 7.52ꢀ7.33 (m, 7H), 2.13 (s, 1H); C NMR (100 MHz, CDCl3): δ
7
8
9
145.7, 135.4, 135.3, 134.0, 131.8, 130.1, 128.1, 127.1, 127.0, 124.2, 120.2, 110.2, 17.9.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1-(2-Bromophenyl-(1H)-benzo-1,2,3-triazole (3j)15 :
o
1
Pale orange solid, yield 67 mg, (49%), mp 132 C, H NMR (400 MHz, CDCl3): δ 8.16 (d, J =
13
8.4 Hz, 1H), 7.84 (dd, J = 8.4, 1.2 Hz, 1H), 7.57ꢀ7.41 (m, 5H), 7.36 (d, J = 8.4 Hz, 1H). C
NMR (100 MHz, CDCl3): δ 145.7, 135.8, 134.2, 133.8, 131.6, 129.5, 128.7, 128.2, 124.3, 120.9,
120.3, 110.6.
6-Methyl-1-(4-methylphenyl)-(1H)-benzo-1,2,3-triazole (3p)16 :
o
o
1
Pale yellow solid, 90 mg (80%), mp 90 C (lit. 92ꢀ93 C), H NMR (400 MHz, CDCl3): δ 7.99
(d, J = 8.4 Hz, 1H), 7.63 (d, J = 8.4 Hz, 2H), 7.47 (s, 1H), 7.39 (d, J = 8.0 Hz, 2H), 7.24 (dd, J =
13
8.8, 1.2 Hz, 1H), 2.53 (s, 3H), 2.47 (s, 3H); C NMR (100 MHz, CDCl3): δ 145.1, 138.8, 138.7,
134.7, 133.0, 130.4, 126.6, 123.0, 119.7, 109.6, 22.1, 21.3.;
1-(4-Methoxyphenyl)-6-methyl-(1H)-benzo-1,2,3-triazole (3r) :
o
1
White solid; yield 62 mg (55%), mp 85 C, H NMR (400 MHz, CDCl3): δ 7.98 (d, J = 8.4 Hz,
1H), 7.64 and 7.10 (AA’BB’ pattern, J = 8.8 Hz, 9.2 Hz, 4H), 7.42 (t, J = 0.8 Hz, 1H), 7.23 (dd,
13
J = 8.8, 1.2 Hz, 1H), 3.90 (s, 3H), 2.52 (s, 3H); C NMR (100 MHz, CDCl3): δ 159.8, 145.0,
138.8, 133.2, 130.2, 126.5, 124.7, 119.7, 115.0, 109.5, 55.7, 22.1; HRMS (ESI, m/z) Calcd for
C14H13N3ONa 262.0956 (M+Na), found 262.0963.
1-(2-Fluorophenyl)-6-methyl-(1H)-benzo-1,2,3-triazole (3s) :
o
1
Pale yellow solid, 69 mg (61%), mp 89 C, H NMR (400 MHz, CDCl3): δ 8.00 (d, J = 8.8 Hz,
1H), 7.70ꢀ7.66 (m, 1H), 7.56ꢀ7.51 (m, 1H), 7.40ꢀ7.35 (m, 2H), 7.26ꢀ7.24 (m, 2H), 2.52 (s, 3H);
13C NMR (100 MHz, CDCl3): δ 157.0, 154.5, 144.6, 139.2, 134.1, 131.0, 130.9, 127.9, 126.7,
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 24 of 27
1
2
3
4
5
6
125.3, 125.2, 124.8, 124.7, 119.6, 117.3, 117.1, 109.8, 109.7, 22.1; HRMS (ESI, m/z) Calcd for
228.0925 (M+H), found 228.0932.
7
8
9
1-(4-Chlorophenyl)-6-methyl-(1H)-benzo-1,2,3-triazole (3v)15 :
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
White solid, 93 mg (77%), m
p 131 oC (lit. 128ꢀ130 oC), 1H NMR (400 MHz, CDCl3): δ 8.00 (d, J
= 8.4 Hz, 1H), 7.72 (d, J = 8.8 Hz, 2H), 7.57 (d, J = 8.8 Hz, 2H), 7.46 (d, J = 0.4 Hz, 1H), 7.26
13
(d, J = 8.4 Hz, 1H), 2.54 (s, 3H); C NMR (100 MHz, CDCl3): δ 145.3, 139.4, 135.8, 134.4,
132.7, 130.1, 126.8, 124.1, 120.0, 109.4, 22.2.
1-(3-Chlorophenyl)-(1H)-benzo-1,2,3-triazole (3y)23:
o
o
1
Pale yellow solid, 64 mg (56%), mp 106 C (lit. 108ꢀ110 C), H NMR (500 MHz, CDCl3): δ
8.16 (d, J = 8.5 Hz, 1H), 7.84 (t, J = 2 Hz, 1H), 7.76 (d, J = 8.5 Hz, 1H), 7.73ꢀ7.71 (m, 1H),
7.61ꢀ7.54 (m, 2H), 7.50ꢀ7.45 (m, 2H); 13C NMR (125 MHz, CDCl3): δ 146.6, 138.1, 135.7,
132.1, 131.0, 128.8, 128.7, 124.8, 123.0, 120.8, 120.6, 110.2.
Supporting Information
The supporting information is available free of charge on the ACS publication website at DOI:
Copies of 1H and 13C NMR spectra of derivatives of 2 and 3 and CIF files of 2q and 2w.
Acknowledgment
We thank the Department of Chemistry, IIT Madras for infrastructure and Mr. Venkatachalam
Ramkumar for the XRD data and structure solving. AC thanks UGC, New Delhi for a
fellowship.
Corresponding Author
*Eꢀmail: sanka@iitm.ac.in
Notes:
The authors declare no competing financial interest.
ACS Paragon Plus Environment

Page 25 of 27
The Journal of Organic Chemistry
1
2
3
4
5
6
References :
7
8
9
1. Gadekar, S. M.; Ross, E. J. Org. Chem. 1961, 26, 613.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2. Gadekar, S. M.; Frederick, J. L. J. Org. Chem. 1962, 27, 1383.
3. Caliendo, G.; Fiorino, F.; Grieco, P.; Perissutti, E.; Santagada, V.; Meli, R.; Raso, G. M.;
Zanesco, A.; Nucci, G. D. Eur. J. Med. Chem. 1999, 34, 1043.
4. Zandt,V.; Michael, C. PCT Patent, WO 9,743,239, 1997.
5. Kumar, K. S.; Rambabu, D.; Krishna, G. R.; Reddy, C. M.; Misra, P.; Pal, M. Bioorg.
Med. Chem. Lett. 2012, 22, 1146.
6. Rosowsky, A. PCT Patent, WO 9,304,051, 1993.
7. a) Fang, ZꢀJ.; Zheng, SꢀC.; Guo, Z.; Guo, JꢀY.; Tan, B.; Liu, XꢀY. Angew. Chem. Int. Ed.
2015, 54, 9528. b) Wang, H.; Yu, S. Org. Lett. 2015, 17, 4272. c) Yamauchi, M.;
Morimoto, M.; Miura,T.; Murakami, M. J. Am. Chem. Soc. 2010, 132, 54. d) Miura, T.;
Yamauchi, M.; Murakami, M. Org. Lett. 2008, 10, 3085.
8. a) Colomer, J. P.; Moyano, E. L.; Tetrahedron Lett. 2011, 52, 1561. b) Clark, A. S.;
Deans, B.; Stevens, M. F. G.; Tisdale, M. J.; Wheelhouse, R. T.; Denny, B. J.; Hartley, J.
A. J. Med. Chem. 1995, 38, 1493. c) Heyningen, E. V. J. Am. Chem. Soc. 1955, 77, 6562.
9. Yan, Y.; Nu, B.; Yu, K.; Yu, J; Zhi, H.; Liu, Y. Adv. Synth. Catal. 2016, 358, 212.
10. a) Kumar, K. S.; Sandra, R. S.; Rambabu, D.; Krishna, G. R.; Reddy, C. M.; Misra, P.;
Pal, M. Bioorg. Med. Chem. Lett. 2012, 22, 1146. b) Sugahara, M.; Ukita, T. Pharm.
Bull. 1997, 45, 719.
11. Li, W.; Wu, X. F. Org. Lett. 2015, 17, 1910.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 26 of 27
1
2
3
4
5
6
7
8
9
12. a) Wu, X. F.; Neumann, H.; Beller, M. Chem. Rev. 2013, 113, 1; b) Wu, X. F.; Neumann,
H.; Beller, M. Chem. Soc. Rev. 2011, 40, 4986; c) Zeng, F.; Alper, H. Org.Lett. 2010, 12,
3642; d) Neumann, K. T.; Laursen, S. R.; Lindhardt, A. T.; Andersen, B. B.; Skrydstrup,
T. Org. Lett. 2014, 16, 2216.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13. Chandrasekhar, A.; Ramkumar, V.; Sankararaman, S. Eur. J. Org. Chem. 2016, 4041.
14. a) Cho, C. S.; Lee, J. W.; Lee, D. Y,; Shim, S. C.; Kim, T. J. Chem. Commun. 1996,
2115. b) Shim, S. C.; Jiang, L. H.; Lee, D. Y.; Cho, C. S. Bull. Korean. Chem. Soc. 1995,
16, 1064. c) Tilley, J. W.; Coffen, D. L.; Schaer, B. H.; Lind, J. J. Org. Chem. 1987, 52,
2469.
15. Mukhopadhyay, C.; Tapaswi, P. K.; Butcher, R. J. Org. Biomol. Chem., 2010, 8, 4720.
16. a) Kumar, R.K.; Ali, M. A.; Punniyamurthy. T. Org. Lett. 2011, 13(8), 2102; b) Liu, Q. –
L; Wen, D. –D.; Hang, C. –C.; Li, Q. –L.; Zhu, Y. –H. Helv. Chim. Acta. 2010, 93(7),
1350.
17. Zhou, J.; He, J.; Wang, B.; Yang, W.; Ren, H. J. Am. Chem. Soc. 2011, 133, 6868.
18. DABCO as a base for primary amine CO insertion reactions: Uozumi, Y.; Arii, T.;
Watanabe, T. J. Org. Chem. 2001, 66, 5272.
19. Reduction of Pd(II) to Pd(0) by CO: a) Giri, R.; Lam, J. K.; Yu, J. Q. J. Am. Chem. Soc.
2010, 132, 686. b) Willcox, D.; Chappell. B.G.N.; Hogg, K. F.; Calleja, J.; Smalley, A.
P.; Gaunt, M. J. Science 2016, 354, 851.
20. Zhang, H.; Barra, M. J. Phys. Org. Chem. 2005, 18, 498.
21. a) Yin, J.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 124, 6043. b) Fujita, K.; Yamashita,
M.; Puschman, F.; Falcon, M. M. A.; Incarvito, C. D.; Hartwig, J. F. J. Am. Chem. Soc.
2006, 128, 9044.
ACS Paragon Plus Environment

Page 27 of 27
The Journal of Organic Chemistry
1
2
3
4
22. Gli, C.; Schwogler, A.; Brase, S. J. Comb. Chem. 2004, 6, 38.
5
6
23. Chen, Q.; Yu, H.; Xu, Z.; Lin, L.; Jiang, X.; Wang, R. J. Org. Chem. 2015, 80, 6890.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment