Synthesis and Herbicidal Activities of 3‐(4‐Chloro‐2‐fluoro‐5‐substituted phenyl)benzo[d][1,2,3]triazin‐4(3H)‐one Derivatives

A series of 3‐phenyl benzo[d][1,2,3]triazin‐4(3H)‐one derivatives were synthesized through the condensation of phenol E and alkyl (alkenyl, alkynyl) chlorides (bromides, iodide) or alkyl chloroacetates or N‐alkyl chloroacetamides using K₂CO₃ as the acid acceptor in N,N‐dimethylformamide. Phenol E was prepared from starting material, 5‐amino‐2‐chloro‐4‐fluorophenyl ethyl carbonate, in four steps involving in amidation, reduction, diazotization, and deprotecting‐group reaction. The herbicidal activities of the title compounds were tested against two dicotyledonous plants and two monocotyledonous plants, in which some of them exhibited high herbicidal activities against two dicotyledonous plants in preemergence and postemergence treatments. Moreover, when the dosage was decreased to 180 and 90 g/ha, compounds F1 , F8 , and F9 showed highly selective inhibitory activities against amaranth pigweed, alfalfa, asteraceae, field sowthistle, morning glory, purslane, and velvetleaf in postemergence treatment but had no herbicidal efficacy on rape except F1 , suggesting that it be possible to find a kind of herbicides to inhibit dicotyledonous weeds in the field of dicotyledonous crops with the same genus as aforementioned weeds.     

Synthesis and Herbicidal Activity of α-Hydroxy Phosphonate Derivatives Containing Pyrimidine Moiety

A series of α‐hydroxy phosphonate derivatives containing pyrimidine moiety were designed and synthesized. Their structures were characterized by IR, ¹H NMR, MS and elemental analysis. The results of preliminary herbicidal activities (in vitro) showed that some of the title compounds 2 exhibited moderate herbicidal activities against dicotyledonous weeds (Brassica campestris L), and most of compounds 2 showed better activity against dicotyledonous weeds than monocotyledonous weeds (Echinochloa crus‐galli). Further bioassays (in vivo) indicated that some of the title compounds 2 possessed good and selective herbicidal activity against amaranth pigweed (A. retroflexus) in both pre‐ and post‐emergence treatments at the dose of 1.5 kg/ha. For exmple, compounds 2a , 2b and 2e exhibited 100% inhibition against A. retroflexus in pre‐emergence treatment, and 91.7%, 98.8% and 99.5% inhibition in post‐emergence treatment at the dose of 1.5 kg/ha, respectively.     

Synthesis,Characterization, and Herbicidal Activities of New 1,3,4‐Oxadiazoles, 1,3,4‐Thiadiazoles,and 1,2,4‐Triazoles Derivatives Bearing (R)‐5‐Chloro‐3‐fluoro‐2‐phenoxypyridine

Synthesis of some novel 1,2,4‐triazoles, 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles bearing a (R) 5‐(1‐(4‐(5‐chloro‐3‐fluoropyridin‐2‐yloxy)phenoxy)ethyl) unit, as a moiety of commercial herbicide, using their thiosemicarbazides in an alkaline, iodine and acidic media is reported, respectively. The structure of the synthesized compounds was characterized by IR, ¹H, ¹³C NMR spectroscopic data, and elemental analyses. The herbicidal activities of synthesized compounds were evaluated against Echinochloa cruss‐galli, Avena fatua, and Sorgum halepense weeds. Compounds 7 and 12a showed potential herbicidal activity against gramineous weeds. Our results may provide some guidance for synthesis development of some novel oxa or thiadiazole and triazole‐based herbicidal lead structures.     

Design,Synthesis and Herbicidal Activities of Tetrahydroisoindoline‐1,3‐dione Derivatives Containing Alkoxycarbonyl Substituted 2‐Benzoxazolinone

Several different alkoxycarbonyl‐substituted 2‐benzoxazolinone moieties have been incorporated into a tetrahydroisoindoline‐1,3‐dione scaffold to provide 25 compounds ( 1a – 1u and 2a – 2d ). The structures of these compounds were confirmed by ¹H and ¹³C NMR, HRMS and X‐ray single‐crystal diffraction. Some of these compounds ( 1g , 1h , 1j , 1k ) exhibited excellent herbicidal activities against Abutilon theophrasti, Amaranthus retroflexus and Echinochloa crus‐galli at a rate of 375 g AI·ha^?1. Among them, compounds 1h and 1j displayed the best post‐emergence herbicidal effect against Abutilon theophrasti with ED₅₀ values of 1.8 and 5.3 g AI·ha^?1, respectively, which are superior to that of the commercial acifluorfen (44.3 g AI·ha^?1). Field trials demonstrated that compound 1h exhibited similar herbicidal activity to a high concentration atrazine, and found to be safer for maize than atrazine. The results of this study therefore show that compound 1h could potentially be used as a post‐emergence herbicide for maize fields.     

Transition Metal Complexes of N‐(4,6‐Dimethoxypyrimidin‐2‐Ylcarbamothioyl)Benzamide: Design,Synthesis and Herbicidal Activity

Transition metal (Cu(II), Zn(II), Co(II)) complexes of N‐(4,6‐dimethoxypyrimidin‐2‐ylcarbamothioyl)benzamide were prepared. The structures of all the newly synthesized complexes were identified by elemental analyses, IR, ¹H NMR, XPS, MS and TG. Their herbicidal activities were evaluated against a variety of weeds. The preliminary results showed that the target complexes had moderate biological activities against both broad leaf weeds and monocotyledon plants. More importantly, the complexes exhibited some improved herbicidal activities over their non‐complexed counterparts. The present work provides a novel class of transition metal‐based derivatives with potent herbicidal activities for further optimization.     

Synthesis and Herbicidal Activity of 2‐Alkyl(aryl)‐4‐amino‐3‐[alkyl(alkoxy)carbonyl]‐5‐cyano‐6‐[(3‐trifluoromethyl)phenoxy]‐pyridines

To find novel bleaching herbicide lead compounds, a series of novel 2‐alkyl(aryl)‐4‐amino‐3‐[alkyl(alkoxy)carbonyl]‐5‐cyano‐6‐[(3‐trifluoromethyl)phenoxy]‐pyridines was designed and synthesized by the multistep reactions. N,S‐acetal 1 reacted with 2 to obtain multisubstituted pyridines 3 in the presence of zinc nitrate as the catalyst. The target compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l were formed by the oxidation of 3 , followed by the substitution with 3‐(trifluoromethyl)phenol in the presence of potassium carbonate. Their structures were confirmed by IR, ¹H NMR, EI‐MS, and elemental analyses. The preliminary bioassays indicated that some of them displayed moderate herbicidal activity against dicotyledonous weed Brassica campestris L at the concentration of 100 mg/L.     

Synthesis and Biological Activity of Ethyl 4‐Alkyl‐2‐(2‐(substituted phenoxy)acetamido)thiazole‐5‐carboxylate

A series of novel ethyl 4‐(methyl or trifluoromethyl)‐2‐(2‐(substituted phenoxy)acetamido)thiazole‐5‐carboxylates 7a , 7b , 7c , 7d , 7e and 8f , 8g , 8h , 8i , 8j , 8k , 8l , 8m , 8n , 8o , 8p , 8q , 8r were synthesized, and their structures were confirmed by IR, ¹H‐NMR, MS spectra and elemental analysis. The results of preliminary bioassays show that some of the title compounds exhibit moderate to good herbicidal activities. Compared with the fluorine free compounds 7a , 7b , and 7e , the compounds bearing fluorine 8g , 8j , and 8q showed higher herbicidal activities with 70–100% inhibition against Capsella bursa‐pastoris, Amaranthus restroflexus, and Eclipta prostrata at the dosage of 150 g/ha, which indicated that the trifluoromethyl on the thiazole ring was beneficial for the herbicidal activity. Furthermore, compounds 8f , 8g , 8h , 8i , 8j , 8k , 8l , 8m , 8n , 8o , 8p , 8q , 8r were tested for fungicidal activity against Pseudoperonospora cubensis at 500 µg/mL. Compounds 8f and 8q showed the best fungicidal activity with more than 80% inhibition.     

Synthesis and Herbicidal Activity of 5‐Alkyl(aryl)‐3‐[(3‐trifluoromethyl)anilino]‐4,5‐dihydro‐1H‐pyrazolo[4,3‐d]pyrimidin‐4‐imines

A series of novel 5‐alkyl(aryl)‐3‐[(3‐trifluoromethyl)anilino]‐4,5‐dihydro‐1H‐pyrazolo[4,3‐d]pyrimidin‐4‐imines were designed and synthesized by the multistep reactions. 1 reacted with 3‐(trifluoromethyl)aniline to obtain N,S‐acetals 2 in the presence of 10 mol% DBU. 2 reacted with hydrazine to form 5‐amino‐3‐[(3‐trifluoromethyl)anilino]‐1H‐pyrazol‐4‐ nitrile 3 , the target compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m were obtained by the reaction of 3 with triethyl orthoformate followed by the cyclization of 4 with various amines. Their structures were confirmed by IR, ¹H NMR, EI‐MS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate herbicidal activity against dicotyledonous weed Brassica campestris L at the concentration of 100 mg/L. For example, compounds 5f , 5g , 5h , and 5j possessed 60.1%, 63.4%, 67.1%, and 61.3% inhibition against Brassica campestris L at the concentration of 100 mg/L.     

Synthesis and Bioactivities of Novel N‐(4‐(2‐Aryloxythiazol‐5‐yl)but‐3‐yn‐2‐yl)benzamides

A series of novel N‐(4‐(2‐aryloxythiazol‐5‐yl)but‐3‐yn‐2‐yl)benzamide derivatives were designed and synthesized. Their structures were identified by ¹H NMR and elemental analyses. Preliminary bioassays indicated that some title compounds provided >80% control of Sclerotinia sclerotiorum at 50 µg/mL and >70% herbicidal activities against B. campestris at 100 µg/mL. Their structure‐activities relationships were also discussed.     

Synthesis and Biological Activity of O‐Methyl Methyl 1‐(Substituted Phenoxyacetoxy)‐1‐(thien‐2‐yl)methylphosphinates

A series of novel O‐methyl methyl 1‐(substituted phenoxyacetoxy)‐1‐(thien‐2‐yl)methylphosphinates 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h were synthesized. Their structures were confirmed by IR, ¹H NMR, mass spectroscopy, and elemental analyses. The results of preliminary bioassays show that some of the title compounds exhibit moderate to good herbicidal and fungicidal activities. For example, the title compounds 5c , 5d , and 5g possess 90–100% inhibition against the tested plants at the concentration of 10 mg/L and 100 mg/L, whereas the title compounds 5a , 5b , 5c , and 5h possess 70–94% inhibition against Phyricularia grisea and Sclerotinia sclerotiorum at the concentration of 50 mg/L.     

Synthesis and Herbicidal Evaluation of 3‐N‐Substituted Amino‐6‐benzyloxypyridazine Derivatives

A variety of 3‐N‐substituted amino‐6‐benzyloxypyridazine derivatives were designed and synthesized in satisfactory yields. Their structures were confirmed by IR, ¹H‐NMR, and elemental analysis; compound 5j was further determined by X‐ray diffraction crystallography. Their herbicidal activities were evaluated through barnyard grass and rape cup tests in laboratory bioassays. Most of the title compounds 5 displayed moderate herbicidal activities against the dicotyledonous plant Brassica campestris L. The most active compounds in the laboratory were also evaluated in the greenhouse.     

Synthesis and Herbicidal Activity of Muti‐Substituted Pyrido[4,3‐d]pyrimidin‐4‐ones

A series of novel muti‐substituted pyrido[4,3‐d]pyrimidin‐4‐one derivatives 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l were designed and synthesized by the muti‐step reaction. N,S‐acetal 1 reacted with acetyl acetamide in the presence of zinc nitrate to obtain muti‐substituted pyridine 2 , which reacted with triethyl orthoformate to give 8‐cyano‐5‐methyl‐7‐methylthio‐pyrido[4,3‐d]pyrimidin‐4‐one 3 ; the target compounds 5 were obtained in good yields by the oxidation of 3 with H₂O₂ in a catalytic amount of sodium tungstate then by the substitution with various substituted phenols. Their structures were confirmed by IR, ¹H NMR, EI‐MS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate herbicidal activity against dicotyledonous weed Brassica campestris L. at the concentration of 100 mg/L. For example, compounds 5a , 5f , and 5g possessed 76.0%, 62.7%, and 60.2% inhibition against B. campestris at the concentration of 100 mg/L. Moreover, 5a exhibited 58.2% inhibition against B. campestris at the concentration of 10 mg/L.     

Novel 5‐Methyl‐2‐[(un)substituted phenyl]‐4‐{4,5‐dihydro‐ 3‐[(un)substituted phenyl]‐5‐(1,2,3,4‐tetrahydroisoquinoline‐2‐yl)pyrazol‐1‐yl}‐oxazole Derivatives: Synthesis and Anticancer Activity

Eleven novel 5‐methyl‐2‐[(un)substituted phenyl]‐4‐{4,5‐dihydro‐3‐[(un)substituted phenyl]‐5‐(1,2,3,4‐tetrahydroisoquinoline‐2‐yl)pyrazol‐1‐yl}‐oxazole derivatives were synthesized and characterized by elemental analysis, ESI‐MS, ¹H NMR and ¹³C NMR. All of the compounds have been screened for their antiproliferative activities against PC‐3 cell (human prostate cancer) and A431 cell (human epidermoid carcinoma cancer) lines in vitro. The results revealed that compounds 4g , 4j and 4k exhibited the strong inhibitory activities against the PC‐3 cell lines (with IC₅₀ values of 2.8±0.11, 3.1±0.10 and 3.0±0.06 μg/mL, respectively).     

Synthesis and Herbicidal Activity of Acylpyrazole Derivatives Containing 1,2,3‐Thiadiazole Moiety

A series of novel acylpyrazole derivatives containing 1,2,3‐thiadiazole ring 3a – 3m were synthesized by the condensations of 1‐phenyl‐3‐methyl‐4‐(substituted benzal or 4‐methyl‐1,2,3‐thiadiazole‐5‐carbonyl)‐5‐hydroxypyrazole 2 with 4‐methyl‐1,2,3‐thiadiazole‐5‐carbonyl chloride or substituted benzoyl chloride. Their structures were confirmed by IR, ¹H‐NMR, mass spectroscopy, and elemental analyses. The results of preliminary bioassays showed that some of the title compounds 3 exhibited moderate to good herbicidal activities against dicotyledonous plants (Brassica campestris L.) at the concentration of 100 mg/L. For example, compounds 3e , 3f , 3g , and 3k possessed 74.6%, 72.2%, 70.3%, and 84.5% inhibition against B. campestris L., respectively, whereas commercially available herbicide Sulcotrione showed only 35.0% inhibition at the same concentration. Moreover, these compounds displayed higher herbicidal activity against B. campestris L. than Echinochloa crus‐galli. However, these compounds showed weak activities at the concentration of 10 mg/L.     

Synthesis and Herbicidal Activity of Novel 4‐Acyl‐2,5‐disubstituted‐3‐hydroxypyrazoles and 4‐Arylcarbonyl‐3‐substitutedisoxazol‐5‐ones

Two series of novel 4‐acyl‐2,5‐disubstituted‐3‐hydroxypyrazoles 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h and 4‐arylcarbonyl‐3‐substitutedisoxazol‐5‐ones 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i were synthesized by the Scotton–Baumann reaction of 2,5‐disubstituted‐2,4‐dihydro‐pyrazol‐3‐ones 1 or 3‐substituted‐4H‐isoxazol‐5‐ones 6 and various acyl chlorides, followed by the Fries rearrangement in the presence of calcium hydroxide and calcium oxide as the catalyst. Their structures were confirmed by IR, ¹H NMR, mass spectroscopy, and elemental analyses. ¹H NMR indicated that compounds 3 existed in enol forms and compounds 7 in keto configurations. The results of preliminary bioassays showed that some of the title compounds 3 and 7 exhibited moderate to good herbicidal activities against Brassica campestris L. at the concentration of 100 mg/L. Isoxazole compounds 7 showed better herbicidal activity against B. campestris L. than pyrazole compounds 3 did at the concentration of 100 mg/L. Moreover, most of the isoxazole compounds displayed higher herbicidal activity against B. campestris L. than Echinochloa crus‐galli. However, these compounds showed weak herbicidal activities at the concentration of 10 mg/L.     

Synthesis and Biological Activity of 1‐(Substituted phenoxyacetoxy)‐1‐(pyridin‐2‐yl or thien‐2‐yl)methylphosphonates

A series of novel O,O‐dimethyl 1‐(substituted phenoxyacetoxy)‐1‐(pyridin‐2‐yl or thien‐2‐yl)methylphosphonates 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j , 6k , 6l , 6m , 6n and 7a , 7b , 7c , 7d were synthesized. Their structures were confirmed by IR, ¹H NMR, mass spectroscopy, and elemental analyses. The results of preliminary bioassays show that some of the title compounds exhibit moderate to good herbicidal and fungicidal activities. For example, the title compounds 6a , 6c , 6l , 6m , and 7d possess 90–100% inhibition against most of the tested plants at the dosage of 1500 g ai/ha, whereas the title compounds 6b , 6g , 6h and 6n possess 92–100% inhibition against Fusarium oxysporum, Phyricularia grisea, Botrytis cinereapers, Gibberella zeae, Sclerotinia sclerotiorum, and Cercospora beticola at the concentration of 50 mg/L.     

Design,synthesis and biological evaluation of novel 6,7,8,9‐tetrahydro‐2‐(2‐aryloxypyrimidin‐4‐yl)‐2H‐[1,2,4]triazolo[4,3‐a]azepin‐3(5H)‐ones

A series of novel 6,7,8,9‐tetrahydro‐2‐(2‐aryloxypyrimidin‐4‐yl)‐2H‐[1,2,4]triazolo[4,3‐a]azepin‐3(5H)‐ones were designed and efficiently synthesized. Their structures were determined by IR, ¹³C and ¹H NMR, mass spectroscopy, and elemental analysis. These compounds were screened for herbicidal activities against rape and barnyard grass. Compounds 5a‐5f and 5m exhibited moderate herbicidal activity against rape. In addition, the synthesis of the intermediate 1‐(azepan‐2‐ylidene)‐2‐(2‐chloropyrimidin‐4‐yl)‐hydrazine ( 3 ) was studied and the reason for the low yield in the initial procedure is discussed as well.     

Synthesis and Fungicidal Activity of (E)‐5‐[1‐(2‐Oxo‐1‐oxaspiro[4,5]dec/non‐3‐en‐3‐yl)ethylidene]‐2‐aminoimidazolin‐4‐one Derivatives

The novel fungicidal agents, (E )‐5‐[1‐(2‐oxo‐1‐oxaspiro[4,5]dec/non‐3‐en‐3‐yl)ethylidene]‐2‐aminoimidazolin‐ 4‐one derivatives, were designed and synthesized in moderate to excellent yields in four steps using α ‐hydroxyketone and diketene as raw materials and characterized by HR‐ESI‐MS , ¹H NMR and X‐ray diffraction. The preliminary bioassay showed that some of these compounds, such as 5e , 6a , 6e , and 7 h exhibit 87.8%, 91.3%, 89.9% and 87.8% inhibition rates against Sclerotinia scleotiorum , 3b , 3c , 4c and 7 h exhibit 96.4%, 92.5%, 90.3% and 76.9% inhibition rates against Phytophthora capsici at the concentration of 50 µg/mL , respectively. These compounds exhibited significant fungicidal activities against S. scleotiorum and P. capsici with EC₅₀ values of 2.56–11.60 µg/mL , and compounds 6e and 7 h exhibited weak inhibition against the spore germination of S. scleotiorum , while the spore germination of P. capsici was strongly inhibited by compound 7 h solution. Scanning electron microscopy (SEM ) and transmission electron microscopy (TEM ) observation indicated that compound 7 h had a significant impact on the structure and function of the hyphal cell wall of P. capsici mycelium.     

Design,Synthesis, and Herbicidal Activities of 3‐Aryl‐4‐substituted‐5‐[3‐(trifluoromethyl)phenoxy]‐1,2,4‐triazoles

In order to find novel bleaching herbicide lead compounds, a series of novel 3‐aryl‐4‐substituted‐5‐[3‐(trifluoromethyl)phenoxy]‐1,2,4‐triazoles were designed and synthesized by the multi‐step reactions. N‐(Arylformamido)phenylthioureas undergo ring closure in the presence of sodium hydroxide to generate 3‐aryl‐4‐substituted‐4H‐[1,2,4]triazol‐5‐thiols 1 , which reacted with methyl sulfate in the presence of K₂CO₃ to give 3‐aryl‐5‐methylsulfanyl‐4‐substituted‐4H‐[1,2,4]triazoles 2 . The target compounds 4 were synthesized by the oxidation of 2 in the presence of H₂O₂ and Na₂WO₄, followed by the substitution with 3‐(trifluoromethyl)phenol in moderate to good yields. Their structures were confirmed by IR, ¹H NMR, EI–MS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate to good selective herbicidal activity against Brassica campestris L at the concentration of 100 µg/mL. Compounds 4c and 4i possessed 75.0% and 82.6% inhibition against Brassica campestris L at the concentration of 100 µg/mL. However, the target compounds 4 showed weak herbicidal activity against Echinochloa crus‐galli at the concentration of 100 and 10 µg/mL.     

The Synthesis and Herbicidal Activity of 5‐(Substituted‐phenyl)‐4,6‐dioxo −4,5,6,7‐tetrahydropyrazolo[3,4‐d]pyrimidines

5‐(Substituted‐phenyl)‐4,6‐dioxo‐4,5,6,7‐tetrahydropyrazolo[3,4‐d]pyrimidines derivatives were designed and synthesized, and their structures were identified by spectroscopic data and elemental analysis. From the result of the herbicidal activities, several compounds demonstrated good herbicidal activity. Compound 5f showed better inhibition rate against Zinnia elegans in comparison to 5a , 5b , 5c , 5d , 5e and 5g in the post‐emergence test.