- Making endo-cyclizations favorable again: A conceptually new synthetic approach to benzotriazoles via azide group directed lithiation/cyclization of 2-azidoaryl bromides
-
Although benzotriazoles are important and ubiquitous, currently there is only one conceptual approach to their synthesis: bridging the two ortho-amino groups with an electrophilic nitrogen atom. Herein, we disclose a new practical alternative-the endo-cyclization of 2-azidoaryl lithiums obtained in situ from 2-azido-aryl bromides. The scope of the reaction is illustrated using twenty-four examples with a variety of alkyl, alkoxy, perfluoroalkyl, and halogen substituents. We found that the directing effect of the azide group allows selective metal-halogen exchange in aryl azides containing several bromine atoms. Furthermore, (2-bromophenyl)diazomethane undergoes similar cyclization to give an indazole. Thus, cyclizations of aryl lithiums containing an ortho-X = Y = Z group emerge as a new general approach for the synthesis of aromatic heterocycles. DFT computations suggested that the observed endo-selectivity applies to the anionic cyclizations of other functionalities that undergo "1,1-additions" (i.e., azides, diazo compounds, and isonitriles). In contrast, cyclizations with the heteroatomic functionalities that follow the "1,2-addition" pattern (cyanates, thiocyanates, isocyanates, isothiocyanates, and nitriles) prefer the exo-cyclization path. Hence, such reactions expand the current understanding of stereoelectronic factors in anionic cyclizations.
- Ageshina, Alexandra A.,Chesnokov, Gleb A.,Topchiy, Maxim A.,Alabugin, Igor V.,Nechaev, Mikhail S.,Asachenko, Andrey F.
-
supporting information
p. 4523 - 4534
(2019/05/17)
-
- Synthesis, reactions, and structural and NMR features of [2.2]metacyclophane monoenes and their tricarbonylchromium and cyclopentadienyliron(+) complexes
-
8,16-Dimethyl-, 5,8,13,16-tetramethyl-, and 4,6,8,12,14,16- hexamethyl[2.2]metacyclophanene have been synthesized from the corresponding methyl-substituted 3-thia[3.2]metacyclophane precursors via a Wittig rearrangement-Hofmann elimination procedure. Simp
- Mitchell, Reginald H.,Zhang, Limin
-
p. 7140 - 7152
(2007/10/03)
-
- Halogenation Using Quaternary Ammonium Polyhalides. VI. Bromination of Aromatic Amines by Use of Benzyltrimethylammonium Tribromide
-
The reaction of aromatic amines with benzyltrimethylammonium tribromide in dichloromethane-methanol containing calcium carbonate powder for 0.5 h at room temperature gave bromo-substituted aromatic amines in good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Inoue, Kazuhisa,Kondo, Manabu,Nakamura, Hiroko,et al.
-
p. 597 - 599
(2007/10/02)
-