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Related Concept Videos

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

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All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
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Basicity of Heterocyclic Aromatic Amines01:25

Basicity of Heterocyclic Aromatic Amines

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Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
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Aryldiazonium Salts to Azo Dyes: Diazo Coupling01:11

Aryldiazonium Salts to Azo Dyes: Diazo Coupling

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The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the...
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Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

4.0K
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom,...
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Related Experiment Video

Updated: Jul 17, 2025

Facile Preparation of 4-Substituted Quinazoline Derivatives
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Facile Preparation of 4-Substituted Quinazoline Derivatives

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Structural optimization based on 4,5-dihydropyrazolo[1,5-a]quinazoline scaffold for improved insecticidal activities.

Shuai Yang1, Benjie Li1, Jiahong Tang1

  • 1National Key Laboratory of Green Pesticide, Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, College of Plant Protection, South China Agricultural University, Guangzhou 510642, People's Republic of China.

Pesticide Biochemistry and Physiology
|September 4, 2023
PubMed
Summary

Novel insecticides based on the 4,5-dihydropyrazolo[1,5-a]quinazoline (DPQ) scaffold show high efficacy against pests like Plutella xylostella. Compound 12, a potent GABA receptor antagonist, demonstrates significant insecticidal activity and potential for agrochemical development.

Keywords:
4,5-dihydropyrazolo[1,5-a]quinazolineBaitsInsect GABA receptorInsecticidal activitiesInsecticides

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Area of Science:

  • Agrochemistry
  • Insect toxicology
  • Medicinal chemistry

Background:

  • Insecticide resistance and environmental concerns necessitate novel pest control agents.
  • The 4,5-dihydropyrazolo[1,5-a]quinazoline (DPQ) scaffold offers a new mode of action, targeting insect γ-aminobutyric acid receptors (GABAR) with no cross-resistance.
  • Previous research identified pyraquinil as a highly insecticidal DPQ.

Purpose of the Study:

  • To design and synthesize novel DPQ derivatives.
  • To evaluate the insecticidal activity of these compounds against key agricultural pests.
  • To investigate the mode of action of promising candidates.

Main Methods:

  • Synthesis of a new series of DPQ compounds based on pyraquinil.
  • Evaluation of insecticidal activity against Plutella xylostella, Spodoptera exigua, Spodoptera frugiperda, and Solenopsis invicta.
  • Electrophysiological studies using Xenopus oocytes to assess GABAR antagonism.
  • Molecular docking and density functional theory (DFT) calculations to understand structure-activity relationships.

Main Results:

  • Compounds 6 and 12 exhibited superior insecticidal activity against P. xylostella compared to existing insecticides like fipronil.
  • Compound 12 showed high efficacy against Solenopsis invicta, with a 98.89% mortality rate at 0.5 mg/L.
  • Electrophysiological data confirmed compound 12 as a potent GABAR antagonist.
  • Molecular docking revealed key interactions between compound 12 and P. xylostella GABAR.

Conclusions:

  • The DPQ scaffold is a promising basis for developing new insecticides with novel modes of action.
  • Compound 12 displays significant insecticidal potential and warrants further development as an agrochemical candidate.
  • This study provides valuable insights for the rational design of DPQ-based pesticides.