Synthesis and Bioactivities of α-Aminophosphonate Derivatives Containing Benzothiazole and Thiourea Moieties

Research Progress of Benzothiazole and Benzoxazole Derivatives in the Discovery of Agricultural Chemicals

Benzoxazole and benzothiazole have a broad spectrum of agricultural biological activities, such as antibacterial, antiviral, and herbicidal activities, which are important fused heterocyclic scaffold structures in agrochemical discovery. In recent years, great progress has been made in the research of benzoxazoles and benzothiazoles, especially in the development of herbicides and insecticides. With the widespread use of benzoxazoles and benzothiazoles, there may be more new products containing benzoxazoles and benzothiazoles in the future. We systematically reviewed the application of benzoxazoles and benzothiazoles in discovering new agrochemicals in the past two decades and summarized the antibacterial, fungicidal, antiviral, herbicidal, and insecticidal activities of the active compounds. We also discussed the structural-activity relationship and mechanism of the active compounds. This work aims to provide inspiration and ideas for the discovery of new agrochemicals based on benzoxazole and benzothiazole.

Synthesis and Biological Importance of 2-(thio)ureabenzothiazoles

The (thio)urea and benzothiazole (BT) derivatives have been shown to have a broad spectrum of biological activities. These groups, when bonded, result in the 2-(thio)ureabenzothizoles (TBT and UBT), which could favor the physicochemical and biological properties. UBTs and TBTs are compounds of great importance in medicinal chemistry. For instance, Frentizole is a UBT derivative used for the treatment of rheumatoid arthritis and systemic lupus erythematosus. The UBTs Bentaluron and Bethabenthiazuron are commercial fungicides used as wood preservatives and herbicides in winter corn crops. On these bases, we prepared this bibliography review, which covers chemical aspects of UBTs and TBTs as potential therapeutic agents as well as their studies on the mechanisms of a variety of pharmacological activities. This work covers synthetic methodologies from 1935 to nowadays, highlighting the most recent approaches to afford UBTs and TBTs with a variety of substituents as illustrated in 42 schemes and 13 figures and concluded with 187 references. In addition, this interesting review is designed on chemical reactions of 2-aminobenzothiazoles (2ABTs) with (thio)phosgenes, iso(thio)cyanates, 1,1′-(thio)carbonyldiimidazoles [(T)CDI]s, (thio)carbamoyl chlorides, and carbon disulfide. This topic will provide information of utility for medicinal chemists dedicated to the design and synthesis of this class of compounds to be tested with respect to their biological activities and be proposed as new pharmacophores.

One-pot synthesis, structure and structure-activity relationship of novel bioactive diphenyl/diethyl (3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-yl)(arylamino)methylphosphonates

BACKGROUND

N-Pyridylpyrazole derivatives have received continuous attention in agrochemical research during the last decade owing to their remarkable insecticidal or fungicidal potentials. To look for novel heterocyclic agrochemicals for increasing production of agriculture, a series of novel α-aminophosphonate derivatives containing N-pyridylpyrazole moiety were synthesized.

RESULTS

The structures of the title compounds were confirmed via melting point, IR, ¹ H NMR, ¹³ C NMR, ³¹ P NMR, HRMS and elemental analysis. The single crystal structure of diethyl (3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-yl)(2,6-dimethylphenylamino)methylphosphonate (compound 12b) was first reported. Moreover, the bioassays displayed that the title compounds exhibited modest or weak insecticidal activities against oriental armyworm at 200 μg mL^-1 . The first investigation on the fungicidal potential of chlorantraniliprole showed no significant activities towards the six tested fungi found in this study, however, most of the title compounds displayed apparent in vitro fungicidal activity against some plant fungi, in particular excellent activities towards Physalospora piricola. Compounds 11a and 11b had EC₅₀ values of 18.8 and 17.4 μg mL^-1 , respectively, which were comparable with that of fungicide control triadimefon (EC₅₀  = 24.7 μg mL^-1 ) against Physalospora piricola. In addition, some compounds exhibited modest in vivo control efficacy at 0.5 mg mL^-1 towards Sclerotinia sclerotiorum (11b: 30.1(±1.8)%), Rhizoctonia cerealis (11a: 20.4(±2.1)%; 11b: 30.2(±2.2)%), and Erysiphe graminis (11a: 30.3(±1.8)%; 12d: 40.2(±0.9)%).

CONCLUSION

Compounds 11a, 11b and 12d could be promising new lead structures for the development and discovery of novel fungicides towards Physalospora piricola and Erysiphe graminis. The structure-activity relationship (SAR) analysis provided useful guidance and new understanding for the design of novel pyridylpyrazole-containing agrochemicals. © 2019 Society of Chemical Industry.