Preparation method 1

Preparation of isopropylaminosulfonyl chloride First, isopropylamine is reacted with hydrochloric acid to produce isopropylamine hydrochloride, dehydrated in a yield of 90% to 95%, and then isopropylamine hydrochloride is reacted with a sulfonyl chloride in an acetonitrile solvent. Got it. The ratio of raw materials to isopropylamine hydrochloride: sulfonyl chloride: acetonitrile = 1:3:6; in the boiling reflux reaction,> 60 °C, the time is not less than 16h, the final reaction temperature 60 ~ 70 °C.

Preparation of o-Aminobenzoic acid methyl ester Firstly, phthalic anhydride is reacted with aqueous ammonia and sodium hydroxide to obtain o-carboxamide benzoate. It is then prepared by reacting sodium ortho-formamide benzoate with sodium hypochlorite, sodium hydroxide, and methanol.

The synthesis of bentazone uses toluene as a solvent, ammonia as an acid binding agent (or using an organic base such as tri-n-butylamine), adding isopropylaminosulfonyl chloride to methyl anthranilate, and heating to form N-isopropylamine. Sulfonylmethyl anthranilate (50-55). This step of reaction to control the reaction pH value, can get higher yield, it is reported that the pH value of 5 ~ 6.5 is appropriate, do not acid. The use of helium temperature (-5 ~ 5 °C) cooling method to improve product quality, in order to ensure the success of the follow-up reaction.

Then the cyclization reaction was carried out in sodium methoxide solution, and the reaction was carried out at 60-65° C. for 30 min, and then acidified to obtain bentazone.

Preparation method two

Industrial clomazone can be synthesized using phthalic anhydride as raw material.