Reaction #1091

Reaction equation

methanol

2-carboxy-5-nitrobenzenesulfonic acid

thionyl chloride

→

2-methoxycarbonyl-5-nitrobenzenesulfonic acid

Solvents

DMF

Conditions

Workup

1. 1
   Temperatureis heated
2. 2
   OtherAfter separating off the insoluble constituents
3. 3
   Filtrationby filtration
4. 4
   Concentrationthe filtrate is concentrated
5. 5
   Otherresults
6. 6
   workup.ADDITIONWhen addition
7. 7
   OtherThe solid which precipitates
8. 8
   Filtrationis filtered off
9. 9
   Otherdried

Procedure

A suspension of 190.0 g (0.77 mol) of 2-carboxy-5-nitrobenzenesulfonic acid, 10 ml of DMF and 250 ml (3.43 mol) of thionyl chloride is heated at boiling for 3 h. After separating off the insoluble constituents by filtration, the filtrate is concentrated. 200 ml (4.94 mol) of methanol are added to the residue which results. When addition is complete the reaction mixture is cooled to 0° C. The solid which precipitates is filtered off and dried. 70.9 g (35.3% of theory) of colorless, crystalline 2-methoxycarbonyl-5-nitrobenzenesulfonic acid (m.p.: 92°-94° C.) are thus obtained. By distilling off the volatile components from the mother liquor, a second fraction (62.5 g, 31.1% of theory) is obtained.

Source