G Model
CCLET 5532 No. of Pages 2
Chinese Chemical Letters
Communication
Metal-free synthesis of 1,2,3-benzotriazines
a,c
d
b,
Jin-Yang Chen , Ying-Wu Lin , Wei-Min He *
a
College of Chemistry and Chemical Engineering, Yangtze Normal University, Chongqing 408000, China
Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation, Changsha University of Science and Technology, Changsha
b
4
10114, China
c
School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001, China
d
A R T I C L E I N F O
A B S T R A C T
Article history:
The recent molecular iodine catalyzed [1,2]-rearrangement of aryl amines and 3-amino-1H-indazolesfor
Received 13 February 2020
Received in revised form 5 March 2020
Accepted 10 March 2020
Available online xxx
the synthesis of 1,2,3-benzotriazines is highlighted.
©
2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Keywords:
Iodine
Metal-free
Rearrangement reaction
1,2,3-Benzotriazines
Moleculariodineisausefulreagentinmodernorganicsynthesis,
Generally, rearrangement reaction could construct compli-
cate molecules from easily available substrates. Therefore,
rearrangement reaction could be an alternative strategy for
the synthesis of 1,2,3-benzotriazines. Very recently, the research
group of Professor Xiuling Cui and Professor Chao Pi from
Zhengzhou University reported an elegant rearrangement
approach for the synthesis of 1,2,3-benzotriazines through
N-centered [1,2]-rearrangement of 3-aminoindazoles with ani-
lines without using diazonium salts or azides (Scheme 1) [7]. In
which could function as an iodinating reagent, a mild oxidant, or a
mild Lewis acid. Compared with chlorine and bromine, iodine has
the lowest homolytic dissociation energy (151 kJ/mol), which
makes single-electron-transfer processes easy. Additionally, iodide
anionsareeasilyoxidizedintomoleculariodinebyvariousoxidants.
More importantly, iodine and its salts have a relatively low toxicity
rendering them green reagents in the viewpoint of sustainable
chemistry [1]. Due to the above-mentioned advantages, a plethora
of iodine-catalyzed/mediated organic transformations have been
developed in the past decades [2–5].
this reaction, C
¼N and N ꢀꢀ N bonds are simultaneously formed.
Correspondingly, various N-aryl-1,2,3-benzotriazin-4(3H)-imines
3 were obtained in the presence of aryl amine 1 (0.12 mmol),
N-Heterocyclic1,2,3-benzotriazine is an important class of
scaffold, which is extensively found in the fields of organic
synthesis, pharmaceutical chemistry and material chemistry, due
to its unique chemical activities and bioactivities [6]. Among them,
2
3-amino-1H-indazole 2 (0.1 mmol), I (10 mol%), tert-butyl hydro-
peroxide (TBHP, 2 equiv.) and tetra-butylammonium iodide (TBAI,
ꢁ
1.5 equiv.) in 1-propanol (2 mL) at 80 C under air atmosphere for
4-substituted-1,2,3-benzotriazines are the core structure of some
12 h (Scheme 1a).
significant molecules with anti-inflammatory and antitumor
activities. Generally, the conventional strategies for the synthesis
of 4-substituted-1,2,3-benzotriazines require the use of the highly
active reactants such as diazonium salts and azides under harsh
conditions. Consequently, the exploration of novel and efficient
procedures for the construction of 4-substituted-1,2,3-benzotria-
zines from easily-handled-reagents under mild conditions is
highly desirable and attractive.
In the substrate scope, it was found that a large number of
functional groups were compatible in this protocol, affording the
corresponding1,2,3-benzotriazineproductsinmoderatetoexcellent
yields. Overall, 30 examples were successfully achieved. Moreover,
the secondary amines including N-methyl-1-phenylmethanamine
and N-methylaniline were well tolerated. Additionally, no steric
effects were observed in this reaction. Similarly, the electronic
effects were not obvious, while some substrates bearing strong
3 2
electron-withdrawing groups (e.g., CF , NO ) did not work in this
procedure (Scheme 1b).
A plausible mechanism of the [1,2]-rearrangement reaction
was proposed as shown in Scheme 1c. First, in the present of TBHP
*
001-8417/© 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
1
Chen, Jin-Yang
