Arylalkoxy urea derivatives

The compounds of the 3-aryl-1-alkoxy-l-alkylurea group, closely related to the 3-aryl-1,1-dialkylureas, can be derived from the oxyureas  

They have a lower biological activity and persistence than the aryl-dialkyl ureas discussed above, but their selectivity is greater. These derivatives can safely be used as selective weed killers in sensitive crops. 

Of the many variants four compounds found so far have received widespread application in agriculture monolinuron, 3-(4-chIorophenyl)-l-methoxy-I-methylurea, (20) linuron, 3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea, (21) metobromuron, 3-(4-bromophenyl)-l-methoxy-l-methylurea, (22) chlorbrom-uron, 3-(3-chloro-4-bromophenyl)-l-methoxy-l-methylurea (23). 

Three other experimental herbicides belonging to this group are 3-(3-chloro-4-ethoxyphenyl)-1 -methoxy-1 -methylurea (24), 3-(3-chlorodifluoromethylphenyl)-1 -methoxy-l-methylurea (25), and 3-(4-fluorophenyl)-l-carboxymethoxy-l-methylurea (26). 

3-Aryl-l-aIkoxy-l-alkyIureas can be synthesised by various methods. For example, for the synthesis of monolinuron the following reaction routes have been used  

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