Synthesis And Bioactivity Studies On The N-methyl Amino Formic Acid Aromatic Ester

This paper aimed to develop a simple and effective method of preparation of N-methyl aryl carbamtes. 18 novel N-methyl aryl carbamtes were prepared, and the structures were characterized by IR, ¹HNMR, ¹³CNMR, and part of the them were characterized by ESI-MS. The insecticidal and fungicidal activities were also investigated.(1) A series of 2-amino-5-alkyl-1, 3, 4-thiadiazoles 17a¹7i were prepared using amino thiourea and organic carboxylic acids as starting material. Then, reactions of intermediates 17a¹7i with salicylaldehyde yielded the corresponding diathiazolyl substituted Schiff bases 18a¹8i;in addition, 12 Schiff Base 18j¹8u were synthesized by reactions of substituted anilines with salicylaldehyde or p-hydroxybenzaldehyde. The effect of the reaction conditions on the yields of Schiff bases were investigated and it was found that the yields were the highest when the reactions catalyzed by TsOH in refluxing ethanol. When the R-group attached on the thidaizolyl moiety was an aryl group gave higher yield than an alkyl group. Furthermore, when the substituent on the phenyl ring was an electron-donor group gave higher yield than an electron-withdrawing group.(2) Reduction of these Schiff Bases 18 by sodium borohydride in methanol afforded aminomethyl phenols 19a¹9u, and found the yields of the reduction of the thiadiazolyl substituted Schiff Bases were lower than those of the reduction of N-aryl substituted Schiff Bases. At the same time, we also employed"one pot"reaction to synthesize aminomethyl phenol 19, in which Schiff bases were not separated and purified before reduction by NaBH₄. It was found that "one pot" reactions gave much higher yields than those of"step by step"reactions. Generation of less waste and easy purification of the products made the procedure very simple. This is a green method.(3) 18 novel N-methyl-O-aryl carbamates were prepared in moderate yields by reaction of aminomethyl phenol 19 with methyl isocynate in the presence of triethyl amine. The biological activities of the targated products were evaluated. Generally, the results show the products exhibite excellent fungicidal activity although low insecticidal activity. The fungicidal activity against Rhizoctonia solani was the best as shown by compounds 20b, 20e, 20f, 20i, 20j, 20n, 20t, 20u (100% activity at concentration of 500mg/L). The tested compounds exhibited the second higest activity against Sclerotonia sclerotiorum as shown by compounds 20p, 20t (90.8% at concentration of 25mg/L) and by 20b, 20k, 20l (>70%). For insecticidal activity, compounds exhibited higer activity against Aphis fabae than Tetrancychus urticae.