Synthesis of pyrazoles with fluorinated side-chain by cyclization of fluoroalkylated triketides

Synthesis and Solution Structure of 1H‐Benzo‐1,5‐diazepine Derivatives with a Perfluoroalkyl Side Chain

“…Yachevskii and co‐workers described the cyclocondensation of 1,2‐diaminobenzene with unsymmetrical perfluorinated 1,3,5 ‐ triketones . We have recently reported the synthesis of perfluorinated 3,5‐dioxoesters and their application to the synthesis of pyrazoles and isoxazoles . Herein, we wish to present, to the best of our knowledge, the first cyclocondensation reactions of perfluorinated 3,5‐dioxoesters with 1,2‐diaminobenzenes.…”

Selective Incorporation of Fluorine in Pyrazoles

“…Naturally, a desire for new methods to incorporate fluorinated substituents onto the pyrazole ring system is increasing. [12][13][14][15][16][17][18][19][20][21][22][23] To make this review easier to read, we have implemented color in the schemes and figures: fluoroalkyl substituents are highlighted in red, and aromatic fluorine containing moieties are shown in blue throughout the entire manuscript. Pyrazoles may be prepared in a variety of ways.…”

Regioselective Synthesis of Functionalized 3- or 5-Fluoroalkyl Isoxazoles and Pyrazoles from Fluoroalkyl Ynones and Binucleophiles

“…Formation of hydroxyisoxazolines 16 instead of isoxazoles 17 in the reaction of ynones 13 with NH 2 OH can be explained by the modest aromaticity of isoxazoles 43 along with the electron-withdrawing effect of the fluoroalkyl substituents, which stabilize hemiketals. 38 Further dehydration of hydroxyisoxazolines 16 to isoxazoles 17 required careful optimization of the reaction conditions, which were performed with 0.5 g of 16a as a model substrate (Table 2). The evaluated methods included acylation and sulfonylation of alcohols followed by β-elimination (entries 1− 4), as well as dehydration under acidic (entries 5−7) and basic (entry 8) conditions.…”

“…Finally, the best result was achieved when a solution of ynone 16a in THF was treated with a solution of presynthesized NH 2 OH (from NH 2 OH·HCl and NaHCO 3 ) in a minimal amount of H 2 O (99% on 0.5 g scale and 84% on 200 g scale). Formation of hydroxyisoxazolines 16 instead of isoxazoles 17 in the reaction of ynones 13 with NH 2 OH can be explained by the modest aromaticity of isoxazoles along with the electron-withdrawing effect of the fluoroalkyl substituents, which stabilize hemiketals …”

“…HCl for 8b ) would be hardly adaptable for the preparation of functionalized derivatives. Additionally, increased stability of fluoroalkyl-substituted hemiketal moiety in hydroxypyrazolines 7a and hydroxyisoxazolines 7b was previously reported to complicate the dehydration step; − therefore, revision of the dehydration conditions was necessary.…”