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• 610-64-0 1-(2-nitrobenzylidene)-2-phenylhydrazine 
• 100-63-0 phenylhydrazine 
• 552-89-6 2-nitro-benzaldehyde 

Relevant academic research and scientific papers

A General One-Pot Synthesis of 2H-Indazoles Using an Organophosphorus–Silane System

A simple and direct approach for the regioselective construction of the privileged 2H-indazole scaffold is described. The developed one-pot strategy involves phospholene-mediated N?N bond formation to access 2H-indazoles. The amount of organophosphorus reagent was minimized by recycling the phospholene oxide with organosilane reductants. Starting from functionalized 2-nitrobenzaldehydes and primary amines, a mild reductive cyclization, involving the use of commercially available phospholene oxide and silanes, delivered a wide variety of substituted 2H-indazoles in good to excellent yields.

Microwave-assisted Cadogan reaction for the synthesis of 2-aryl-2H-indazoles, 2-aryl-1H-benzimidazoles, 2-carbonylindoles, carbazole, and phenazine

(Chemical Equation Presented) The Cadogan reaction, a widely accepted route for the synthesis of nitrogen containing heterocycles, is modified by using microwave radiation as the source of heat instead of the conventional heating by reflux in a nitrogen atmosphere for several hours. Appropriate starting materials were mixed with triethyl phosphite or triphenylphosphine and irradiated with microwaves for several minutes at a specific power to give the desired products. The indazoles were prepared by irradiating N-(2-nitrobenzylidene) anilines with triethyl phosphite at 200 W for 12-14 min to give 85-92% product yields. Irradiation of the mixture of N-benzylidene-2-nitroanilines and triphenylphosphine at 200 W for 3-5 min yielded 93-96% of the benzimidazoles. The carbonylindoles were obtained in 61-68% yields by irradiating 2-nitrochalcone or alkyl 2-nitrocinnamates and triphenylphosphine with microwaves at 80-200 W for 8-11 min. The mixture of 2-nitrobiphenyl and triphenylphosphine yielded 96% of carbazole when irradiated with microwaves at 200 W for 2 min while 75% of phenazine was obtained by irradiating the mixture of 2-nitrodiphenylamine and triphenylphosphine with microwaves at 200 W for 3.5 min. These results show that microwave-assisted Cadogan reactions gave better product yields at shorter reaction times.

Pyrolysis of Aryl Azides. IX. Azomethines as Weak Neighbouring Groups

The following rates of pyrolysis (relative to azidobenzene at 120 deg C) have been measured in decalin solution: 2-azidobenzaldehyde, 28.8; 2-azidobenzylideneaniline, 59.5; 2-azidobenzaldehyde phenylhydrazone, 8.9; 2-azidobenzaldehyde oxime O-methyl ether, 1.3; 2-azidoacetophenone oxime O-methyl ether, 23.4; 2-azidobenzophenone phenylhydrazone, 9.7.It is argued that these relative rates are largely determined by the extent to which the ortho substituent is in the reactive conformation for an electrocyclic process.Indazoles substituted on N2 are isolated from pyrolysis of those azides with ortho-azomethine substituents.

1H- and 2H-Indazoles by Thermal and Photolytic Decomposition of o-Azidobenzoic Acid and o-Azidobenzaldehyde Derivatives

Ethyl o-azidobenzimidate (6) and o-azidobenzamidine (7) on thermolysis yield 3-ethoxy- (9; X=OEt) and 3-amino-1H-indazole (9; X=NH2), respectively.The former product is also obtained on irradiation of the imidate in methanol-tetrahydrofuran solution. 2-Aryl- and 2-heteroaryl-3-chloro-2H-indazoles have been prepared by the action of hot thionyl chloride on o-azidoanilides.The trichloro-2H-indazoles obtained by the action of phosphorus pentachloride on o-azidobenzanilide (12) and by the action of thionyl chloride on N-(o-azidobenzoyl)-2-aminopyridine have been identified as the 3,5,7-trichloro derivatives.The reductive dehalogenation, nitration, and reactivity of the halogen towards nucleophiles, of 3-chloro-2-phenyl-2H-indazole (19) are reported.A new practicable synthesis of o-azidobenzaldehyde (31; X=O) is described.Thermolysis of its phenylhydrazone and semicarbazone derivatives yields 2H-indazoles.