Butyrolactone sulfonylureas

Synthesis and Herbicidal Activity of Conformationalty Restricted Butyrolactone Sulfonylureas... 

Herbicidal Activity. Table I summarizes herbicide data for two representative o-butyrolactone sulfonylureas of formula 4 and provides a comparison with their open-chain counterparts. These data were obtained from greenhouse tests in both pre-and postemergence applications on a variety of weeds and crops. For the sake of clarity, results are presented only for three or four grass weeds, three broadleaf weeds and wheat. The numbers reported in Table I represent percent injury of the particular plant species tested relative to an untreated check (0% injury). 

Within the series of lactones themselves, the unsubstituted y-butyrolactone sulfonylureas 4a displayed the highest levels of herbicidal activity. The y-valerolactones of formula 4b were less active as were the isomeric butyrolactones of formula 16. Substitution on the phenyl ring had little or no effect on the overall level or spectrum of activity. 

The herbicidal activity of sulfonylureas derived from phenylacetic esters is enhanced when the carboxylate moiety is tied up to form a butyrolactone ring. Extension of this structural modification to weakly herbicidal sulfonylureas derived from cinnamate esters gives vinylogous butyrolactones which display significantly improved efficacy. Structure-activity relationships in these two classes of compounds are discussed along with their synthesis involving a novel benzothiazinone dianion and rf/h9-metallation chemistry. 

The orr/w-butyrolactone sulfonamide 6 and y-valerolactone sulfonamide 13 (mixture of diastereomers) were readily converted to the corresponding sulfonylureas using the base DBU (l,8"diazabicyclo[5.4.0]undec-7-ene) as shown in Equation 3 ( ). 

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