Flazasulfuron is a sulfonylurea herbicide used for controlling the unwanted growth of grass, broad-leaved weeds and sedges.

The mode of action of flazasulfuron is through the inhibition of the enzyme acetolactate synthase (ALS), which results in the inhibition of amino acid synthesis, cell division and ultimately plant growth.

Symptoms include leaf discolouration, desiccation, necrosis and ultimately plant death within 20 – 25 days of application.

[1] The synthesis of flazasulfuron begins with the one pot chlorination and chlorine/fluorine exchange of 3-picoline[2] (1).

An alternative strategy is to use (4) as nucleophile with the O-phenylcarbamate of 4,6-dimethoxy-1-aminopyrimidine (7) as electrophile in the presence of DBN.