Bicyclic sulfonylureas

One of the many research programs which developed from George Levitt s discovery of herbicidal benzenesulfonylureas was the preparation and testing of bicyclic sulfonylureas 1. Their general structure contains a benzene ring, fused to a second ring in which the 3-position is attached via a carbon atom. X represents a heteroatom, or is a carbonyl group. 

We have demonstrated a wide variety of known and adaptive measures to prepare previously unknown bicyclic sulfonylureas. These compounds are herbicidally active at low rates and have some crop selectivity. This information has expanded our QS AR knowledge in tiie area, which will aid us in directing future research. 

Representative synthetic methods include Claisen rearrangement, Friedel-Crafts acylation and directed metallation. Bicyclic arylsulfonamides are used to prepare herbicidally active sulfonylureas. Biological activity of these sulfonylureas is discussed. 

The alkaline hydrolysis of a sulfonylurea herbicide, A - [(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl -l-methyl-4-(2-methyl-2//-tetrazol-5-yl)-l//-pyrazole-5-sulfonamide (azimsulfuron) (87) yields, via attack at the carbonyl group, two products, the bicyclic sulfonamide (88) and 2-amino-4,6-dimethoxypyrimidine (89). An alternative reaction pathway is via deprotonation of the sulfonamidic proton, but this possibility was not discussed. 

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