Uracil herbicides, terbacil

Methyl acetoacetate (MAA) and ethyl acetoacetate (EAA) are the most widely used esters they are found ia the pharmaceutical, agricultural, and allied industries. Both esters are used extensively as amine protecting agents ia the manufacture of antibiotics and synthetic sweeteners (Dane Salts) (147). Principal outiets for MAA are the manufacture of the organophosphoms insecticide dia2inon [33341-5] (148,149) and the uracil herbicides bromacil [31440-9] and terbacil [5902-51-2] (150,151) (see Insect conztiol technology Herbicides). 

Use pattern Terbacil is a substituted uracil herbicide used primarily to control annual and perennial grass and broadleaved weeds in apple orchards, alfalfa, asparagus, mint and sugar cane. Other minor uses include blueberries, strawberries and seed grasses... 

Uracil derivatives can also function as herbicides by inhibition of the enzyme protoporphyrinogen-IX-oxidase (PRO), which is involved in the biosynthesis of chlorophyll <2006H(68)561>. Commercial examples of such PPO inhibitors include isocil 1104, bromacil 1105, terbacil 1106, flupropacil 1107, lenacil 1108, butafenacil 1109, and benzfendizone 1110 (Figure 9). 

The most commonly used pyrimidine herbicides are the uracils, e.g. bromacil and terbacil, which have the following structures... 

Unsubstituted uracils have no herbicidal activity but certain derivatives substituted in the 3,5,6-positions are active. The most important examples are bromouracil, terbacil, and lenacil. These compounds were introduced by DuPont in 1963. These herbicides are applied to the soil and are used for selective weed control. Bromacil and terbacil are pre- and postemergence herbicides they control a wide spectrum of grass and broadleaf weeds when applied early in the growing season. These compounds must be carried to the roots by soil moisture, where they are absorbed and translocated to the rest of the plant. This family of herbicides is used for asparagus, sugar cane, pineapple, apple, and citrus crops. 

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