SYNTHESIS AND HERBICIDAL ACTIVITY OF 3-ARYL-5-(HALOALKYL)-4-ISOXAZOLECARBOXAMIDES AND THEIR DERIVATIVES

A series of unique 3-aryl-5-(haloalkyl)-4-isoxazolecarboxamides have b een prepared which exhibit, in both greenhouse and field studies, sign ificant preemergent and postemergent herbicidal activity in the grams per hectare range against broadleaf and narrowleaf weeds. The key step in the formation of the fully substituted isoxazole ring 2 is 1,3 dip olar cycloaddition of a haloalkyl-substituted acetylenic ester and a n itrile oxide intermediate. The 3-aryl-5-(halo alkyl)-4-isoxazolecarbox ylate esters 2 are converted to isoxazole-4-carboxamide herbicides 5 a nd 6, secondary amides 7, and amino acid derivatives 8. Greatest activ ity was observed with compounds having a combination of three substitu ents: a substituted phenyl ring in the 3-position, a primary or second ary carboxamide in the 4-position, and a difluorochloromethyl group in the, 5-position of the isoxazole ring.