Synthesis and Structure-Activity Relationships of Miticidal 4,5-Dihydropyrazole-5-thiones

Abstract

A series of novel 4,5-dihydropyrazole-5-thiones (DHPs) was synthesised by treating the corresponding dihydropyrazolones with Lawesson's reagent and evaluated for miticidal activity against two-spotted spider mites (Tetranychus urticae Koch). Of these, 3-(4-chlorophenyl)-4,4-dimethyl-1-phenyl-4, 5-dihydropyrazole-5-thione, 3-(4-chlorophenyl)-4-ethyl-4-methyl-l-phenyl-4,5-dihydropyrazole-5-thione, 3-(4-chlorophenyl)-1-phenyl-4,5-dihydropyrazole-5-thione-4-spirocyclopentane and 4,4-dimethyl-l-phenyl-3-(4-trifluoromethylphenyl)-4,5-dihydropyrazole-5-thione were highly active (pEC,, > 4-0) and were more effective than the miticide dicofol (pEC,, = 3.879), which has traditionally been used for the control of phytophagous mites. Structure-activity relationship (SAR) studies were performed on each position of the pyrazole ring of DHPs. The results indicated that the unsubstituted phenyl, 4-substituted phenyl and thioxo groups on the 1-, 3-and 5-positions of DHPs respectively were required for activity. Quantitative SAR studies using physicochemical parameters of substituents and the capacity factor k' as a hydrophobicity index suggested that: (a) the activities of all types of DHPs examined were mainly dominated by hydrophobicity, (b) the bulkiness of 4-substituents of the 3-phenyl ring favoured the activity and (c) the log k' optimum for all DHPs was 1.675, equivalent to a log Po, value of c. 5.0.

Polarized Helical Coumarins: [1,5] Sigmatropic Rearrangement and Excited-State Intramolecular Proton Transfer

“…We obtained a better result when silver triflate 23 was used (entry 6). In the presence of p -toluenesulfonic acid, 24 we synthesized the product with a moderate to good yield (59%). The best result, however, was obtained when we used propylphosphonic acid cyclic anhydride in dichloromethane 25 (T 3 P in DCM), a well-known reagent widely used in peptide chemistry.…”

4-Disubstituted Pyrazolin-3-Ones—Novel Class of Fungicides against Phytopathogenic Fungi

“…Due to the wide spectrum of the biological activity of disubstituted pyrazolones, new asymmetric methods for their synthesis are being actively developed [36][37][38][39][40][41]. C4-disubstituted pyrazolones are recognized as valuable antitumor agents [35,[42][43][44][45][46], antimicrobial substances [47], inhibitors of trypanosomal phosphodiesterase B1 [48], RalA inhibitors [49], and miticides [50]. However, their potential as effective fungicides has not been expected.…”

Synthesis of new Spiropyrazole derivatives under microwaves irradiation and docking study for inhibition the microbes and COVID-19

“…One of the bioactive drugs is compounds containing pyrazole moiety which are known with their antimicrobial and antiviral activities [7] , [8] , [9] , [10] , [11] , [12] . The class of spiropyrazoles are well known in literature with the phosphodiesterase inhibitors [13] , antitumor [ 14 , 15 ], analgesic [16] and anti-inflammatory activities [17] . The synthesis of heterocyclic compounds with biological activity for more than one disease is a difficult goal, in addition to synthesis of these derivatives with high yield in a short reaction time is a good goal.…”