Dichlorobenzenesulfonyl chlorides

The Step 2 product (1.0 mmol) dissolved in 5 ml THF at —40°C was treated with 1.1 ml 1M sodium hexamethyldisilazide (1.1 mmol) in THF and after 30 minutes the mixture was further treated with 2,5-dichlorobenzenesulfonyl chloride (1.1 mmol). The solution was stirred overnight at ambient temperature and then treated with saturated NH4C1 solution and concentrated. The residue was dissolved in EtOAc, then washed with brine, dried with Na2S04, concentrated, and an oil isolated. The residue was purified by MPLC using EtOAc/hexane, 2 1, and the product isolated as a colorless viscous oil. 

Disubstitutions around the phenyl ring were investigated by preparing sulfonamides from the commercially available dichlorobenzenesulfonyl chlorides. The activity for these compounds is summarized in Table IV. While all the compounds have good levels of in vitro activity, only the 2,6-dichloro (52) has good levels of activity on grass and broadleaf weeds. The activity on broadleaf weeds is better when one ortho substituent is present, which can be seen by comparing the activity of 52 and 53 to that of 54. 

However, when the chlorosulfonation of the dichlorobenzenesulfonanilides 369 was carried out at 50-60 °C, the conditions successfully used in the chlorosulfonation of the analogous dichlorobenzoic acid anilides, nitrogen-sulfur bond cleavage occurred to yield the corresponding dichlorobenzenesulfonyl chlorides 371 (Equation 116). 

Other derivatives, such as the 3,4-dichlorobenzenesulfonyl ester of starch, " have also been prepared by treating starch with the acid chloride in the presence of sodium hydroxide. 

It was discovered that 2,4-dichloro-, 2,5-dichloro- and 3,4-dichlorobenzenesulfo-nanilides 369 react with excess chlorosulfonic acid (four equivalents) at low temperature (—10 to 8 °C) for 2 hours to give good yields (60-85%) of the corresponding A -(dichlorobenzenesulfonyl) sulfanilyl chlorides 370 (Equation 116).3 ... 

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