Dimethoxypyrimidines as Novel Herbicides. Part 1. Synthesis and Herbicidal Activity of Dimethoxyphenoxyphenoxypyrimidines and Analogues

Abstract

A number of 6-(4-phenoxyphenoxy)pyrimidines and triazines were synthesized and their herbicidal activity was measured. Compounds with the methoxy groups at the 2-and 4-positions on the pyrimidine and triazine rings exhibited high herbicidal activity. Introduction of a substituent into the 5-position of the pyrimidine ring diminished the activity. In the phenoxyphenoxy substructure at the 6-position, the central ether bond can be replaced by a methylene group without loss of activity. The optimum substituent on the terminal phenyl ring was 3-trifluoromethyl. The compounds showed a strong Hill reaction inhibition, but unfortunately showed poor selectivity between weeds and crops.

Gas Phase Chemistry of Li+with Amides: the Observation of LiOH Loss in Mass Spectrometry

“…One class of amides that are of interest are pesticide precursors, such as 2-(4, 6-dimethoxypyrimidin-2-ylsulfanyl)-N-phenylbenzamide and its derivatives [44,45]. Here we report our studies of the gas phase chemistry of Li + adducts of these compounds upon ESI-MS/MS, and among the fragment ions we observe are those reflecting loss of LiOH.…”

Synthesis and herbicidal activity of novel substituted 2- and 4-pyrimidinyloxyphenoxypropionate derivatives

“…The synthesis was performed according to the reported method 29 with some modification. Briefly, a solution of (R)-2-(4-hydroxy-phenoxy)-propanoate 1 (10 mmol), anhydrous K2CO3 (2.5 equiv, 25 mmol) in CH3CN (50 ml) was stirred at room temperature for 0.5 h. After another 0.5 h of reflux, the solution of 4-chloropyrimidine 5, 10 (10 mmol) or 2-methylsulfonyl pyrimidine 7, 9 (10 mmol) in CH3CN (20 ml) was added dropwise and the mixture heated at reflux for another 4 h. After evaporation of the solvent, water was added and the mixture was extracted with ethyl acetate and the organic phase was dried over MgSO4.…”

Gas-phase smiles rearrangement reactions of deprotonated 2-(4, 6-dimethoxypyrimidin-2-ylsulfanyl)-N-phenylbenzamide and its derivatives in electrospray ionization mass spectrometry

“…O-pyrimidinylsalicylates show very strong herbicidal activity under pre-and postemergent treatment conditions against various grasses and broadleaf weeds [1,2]. Also, the 2-(4,6-dimethoxypyrimidin-2-ylthio)benzoic acid derivatives are found to exhibit herbicidal activities against grasses and broadleaf weeds over a wide range of growth stages [3,4].…”