Construction of Multifunctionalized Azopyrazoles by Silver‐ Catalyzed Cascade Reaction of Diazo Compounds

Abstract

Av ariety of multisubstituted azopyrazoles were synthesized in good yield from an efficient onepot silver trifluoromethanesulfonate (AgOTf)-catalyzed cascade reactiono fa-diazo-b-keto esters with two arylhydrazines or twoa rylhydrazine hydrochlorides.T his cascade reactioni ncluded pyrazolone formation, N À Hi nsertion, and oxidation. Fort he synthesis of more diverse azopyrazoles bearing two different aromatic rings,t he silver(I)-catalyzed cascade reactiono f4 -diazopyrazol-3-one with arylhydrazine hydrochloridesw as also developed. Thea dvantages of these methodologies are easy handling, mild reaction conditions,a nd an effective and non-toxic catalyst usage.

Indium(iii)-catalyzed efficient synthesis of 3-arylhydrazonoindolin-2-ones and their fluorescent metal sensing studies

“…12 We previously established a methodology for the synthesis of azopyrazoles via silver-catalyzed cascade reaction of α-diazo-β-keto esters with two arylhydrazines. 13 However, synthetic strategies for the preparation of 3-arylhydrazonoindolin-2-ones from diazo compounds and arylhydrazine are still unexplored. As an ongoing study, we envisioned the development of a novel protocol for installing arylhydrazone moieties at the 3-position of the indolin-2-one starting from diazo compounds.…”

Iodine-mediated construction of polyfunctionalized arylazopyrazoles from β-ketoesters or 2-arylpyrazol-3-ones and arylhydrazines

“…17 General procedure for synthesis of arylazopyrazoles from arylpyrazol-3-ones To a solution of 5-methyl-2-aryl-2,4-dihydro-3H-pyrazol-3-one (0.5 mmol) and arylhydrazine (0.6 mmol) in 1,2-dichlroethane (3.0 mL) were added I 2 (126 mg, 0.25 mmol), acetic acid (0.03 mL, 0.5 mmol) and AgNO 3 (8 mg, 10 mol%) and the reaction mixture was heated at 70°C under a nitrogen atmosphere until the completion of reaction as indicated by TLC. 17 General procedure for synthesis of arylazopyrazoles from arylpyrazol-3-ones To a solution of 5-methyl-2-aryl-2,4-dihydro-3H-pyrazol-3-one (0.5 mmol) and arylhydrazine (0.6 mmol) in 1,2-dichlroethane (3.0 mL) were added I 2 (126 mg, 0.25 mmol), acetic acid (0.03 mL, 0.5 mmol) and AgNO 3 (8 mg, 10 mol%) and the reaction mixture was heated at 70°C under a nitrogen atmosphere until the completion of reaction as indicated by TLC.…”

“…17 Nevertheless, more environmentally benign and simple approaches for the construction of arylazopyrazoles from commercially available starting materials with high diversity are still in strong demand. 17 Nevertheless, more environmentally benign and simple approaches for the construction of arylazopyrazoles from commercially available starting materials with high diversity are still in strong demand.…”

Electrooxidation Is a Promising Approach to Functionalization of Pyrazole-Type Compounds

“…One of the most popular methods for the synthesis of azoarenes is the oxidation of corresponding amines ( Scheme 17 ), predominantly by chemical oxidants (BaMnO 4 [ 147 ], Pb(OAc) 4 [ 148 ], HgO [ 149 ], K 2 FeO 4 [ 150 ], TCICA [ 151 ], t-BuOI [ 152 ]) or oxidation systems (CuBr-pyridine-O 2 [ 153 ], I 2 -t-BuOOH [ 154 ], t-BuOCl-NaI [ 155 ]). The synthesis of polyfunctional azopyrazoles by silver catalyzed cascade conversion of diazo compounds [ 156 ] is also of interest.…”

“…Moreover, the approach A is useful for previously unexplored chemical and electrochemical N–N cross-coupling of aminopyrazoles [ 162 ] ( Table 7 ), and yields of the target azo compounds 1k – 2k and 4k – 5k were 48–50%. Such results create prospects for obtaining useful multifunctional azo compounds [ 152 , 156 ].…”