Pd-catalyzed direct arylation of phenylpyrazole: Synthesis of fipronil derivatives with aryl boronic acids promoted by a stoichiometric amount of NIS

Palladium‐Catalysed CH Bond Electrophilic Fluorination of Highly Substituted Arylpyrazoles: Experimental and DFT Mechanistic Insights

“…Arylpyrazoles are easily made by CN bond formation (Scheme ) 14. We reasoned that a pyrazole unit might be an efficient directing group for CH bond fluorination as it has been nicely demonstrated for CC bond formation by the introduction of phenyl and nitrile groups 11,15,16. This approach gives access to a variety of substituted‐pyrazoles, usable as directing groups.…”

Sustainable protocols for direct C–H bond arylation of (hetero)arenes

“…as the sacrificial oxidant, affording good yields (≤88%) of the corresponding 4-arylated products 111, which are fipronil derivatives showing a potential biological activity (Scheme 46). 145 In 2015, Fuse et al reported the sequential synthesis of 1,3,4,5-tetrasubstituted pyrazoles from pyrazole, consisting of four orthogonal direct C-H arylation reactions, each of them performed in different conditions (including solvents). In particular, in the second step 1-arylpyrazoles 112 were treated with aryl iodides in H 2 O/acetonitrile 9 : 1 (v/v) at 60 °C, in the presence of 10 mol% [Pd(dppf )Cl 2 ]•CH 2 Cl 2 , 20 mol% JohnPhos and Ag 2 CO 3 , affording with high C5 regioselectivity and good yields (53-93%) the corresponding 1,5-diarylpyrazoles 113 (Scheme 47).…”

“…as the sacrificial oxidant, in an ethanol/water 3 : 1 (v/v) mixture, affording good yields (≤88%) of the corresponding 4-arylated products, which are fipronil derivatives with a potential biological activity (see section 3.1.2). 145 Ackermann et al proposed the use of tosylates and mesylates as arylating agents in palladium-catalyzed direct C-H arylation of oxazoles 168 and 1,2,3-triazoles 169 in DMF/t-BuOH mixture as the solvent. 210 In particular, reactions were carried out with 1.2 equiv.…”

The Synthesis of Fipronil Derivatives via Pd‐Catalyzed Direct Alkynylation of Phenylpyrazole with Terminal Alkynes in Green Solvents

“…In view of the biologically important fipronil, we have been devoted to the structural modification of fipronil parent in order to seek for its new analogs with highly biological activity and low toxicity to animals . For example, the compounds of 4‐aryl‐1‐phenylpyrazoles were successfully synthesized via the palladium‐catalyzed direct arylation of phenylpyrazoles with boronic acids . These works provided a series of fipronil derivatives with potential bioactivity.…”