isopropyl 2-[N-(N-butylaminocarbonyl)aminosulfonyl]-4-chlorobenzoate → (1-Methylethyl)-4-chloro-2-(isocyanatosulfonyl)benzoate

Participants

Reaction Conditions

Reaction Steps

A mixture of 388.2 g (1-methylethyl)-2-[(butylaminocarbonyl)aminosulfonyl]-4-chlorobenzoate and 3 L of xylene was azeotropically dried, then cooled to ~100° C. and 1.0 g of 1,8-diazabicyclo[2.2.2.]octane was added. The mixture was heated to ~141° C. and the addition of liquefied phosgene was begun. After 90 ml of phosgene had been added, the reaction temperature was 128° C. The temperature had risen to 132° C. after 1 hr., and an additional 10 ml phosgene was added. Heating was continued the remainder of the day, then the reaction mixture was allowed to cool overnight under a nitrogen atmosphere. The following morning, the reaction mixture was heated to reflux (133° C.) and 24 ml of phosgene was added over 1 hr. The mixture was heated an additional 2 hrs. (temperature--124° C.) and then cooled to ambient temperature. The reaction mixture was filtered under nitrogen, and the filtrate was concentrated in vacuo. The title compound (400.1 g) was isolated as an oil of sufficient purity for the subsequent coupling reaction.

Provenance & Evidence