Synthesis and insecticidal activity of 1,2,4-triazole derivatives

Eight novel compounds were synthesized and their insecticidal activities were tested. The compounds of 3d, 3e and 3g showed insecticidal activity against Aphis rumicis Linnaeus . All the title compounds were characterized on the basis of IR, 1 H NMR and HRMS.


Results and Discussion
The synthetic route of the title compounds was seen in Scheme 2.
The intermediates, 1 and 2, were synthesized according to the literature 14,15 and got the accept yield.The synthetic conditions of the title compounds were investigated, such as temperature, time and base.The temperature had great effect on the yield of the title compounds.The low temperature will prolong the reactive time, otherwise, the by-product will become more when the temperature is beyond 40 o C. We hold the room temperature about 30 o C and got the satisfied yield.The effect of strong base was better than that of weak base clearly.General Preparation of the title compounds 3a-h: 1 (2 mmol) and NaH (2 mmol) were solved in DMSO (10 mL).The mixture were stirred for 1 hour in the flask (50mL) by magnetic stirrer at the room temperature.Then, 2 (2 mmol) was added into the mixture and continued stirring for about 10 hours.The reactive process was monitored by TLC until the starting material nearly disappeared.The reactive mixture was poured into water (20 mL), extracted by chloroform (30 mL), drying over MgSO 4 , the solvent was filtered and evaporated under the reduced pressure, the residue was purified by flash chromatography (petroleum ether/ethyl acetate = 2:1) to afford the title compound then crystallized from methanol.
Judging from the structure of the intermediate 2, the product should contain another isomer which substituted the 4-Cl atom.But, the TLC results showed that there is only one new compound during the whole reactive process, and we only get one substituted compound through the flash chromatography.The reason might be that the carbonyl group of the pyridazinone moiety make the reactivity of 5-C atom is higher than that of 4-C atom.So, we don't find the compound substituted the 4-Cl atom.
All the title compounds' bioactivity was screened by the method of leaf-dip.A stock solution of title compounds (1000ppm) in DMSO was used for preparing various concentrations for bioactivity screening.The compounds of 3d, 3e and 3g showed insecticidal activity against Aphis rumicis Linnaeus.They have the insecticidal rate 45%, 38% and 30% at the concentration of 500ppm.The insecticidal activity decreased clearly when the concentration was decreased.

Experimental Section
General Procedures.Infrared spectra were taken on a Nicolet FT-IR-20SX spectrometer using KBr disks; HRMS spectra on a Micromass GCT instrument; and 1 H NMR spectra on a Brucker WP500SY(500 MHz) spectrometer with DMSO-d 6 or CDCl 3 as solvent and TMS as internal standard.Melting points were measured by a digital melting point apparatus made in Shanghai and were uncorrected.All reactions were followed by TLC.

Materials.
Unless otherwise stated, these were commercial samples.All organic solvents were of analytical quality and used as purchased.Solvent mixtures are defined by volume ratios (v/v).(10), 104(18).