Sodium Hydroxide → 3-(4-Chlorophenyl)-1H-pyrrole-2-carboxylic acid

To a solution of ethyl 3-(4-chlorophenyl)-1H-pyrrole-2-carboxylate [see step 2 ACI-02] (8 g, 32.0 mmol) in DMSO (30 mL) was added NaOH (2.56 g, 64.1 mmol) and the reaction mixture was stirred at 70° C. for 20 h. An additional portion of NaOH (0.5 g, 12.5 mmol) was added and stirring at 70° C. was continued for 30 min. The reaction mixture was cooled in an ice bath and acidified with aqueous 1M KHSO4 (80 mL). The solid was filtered off and washed with aqueous 1M KHSO4 (20 mL), H2O (3×25 mL) and heptane (3×25 mL) and dried on air. The residue was dissolved in EtOAc (600 mL), dried (Na2SO4) and the solvent was removed in vacuo. The product was stirred in i-Pr2O/heptane (1:1, 100 mL). The solid was filtered and off dried in vacuo to give the desired product as a a white solid (6.04 g, 85%).

1. stirringstirring at 70° C.
2. waitwas continued for 30 min
3. temperatureThe reaction mixture was cooled in an ice bath
4. filtrationThe solid was filtered off
5. washwashed with aqueous 1M KHSO4 (20 mL), H2O (3×25 mL) and heptane (3×25 mL)
6. customdried on air
7. dissolutionThe residue was dissolved in EtOAc (600 mL)
8. dry with materialdried (Na2SO4)
9. customthe solvent was removed in vacuo
10. stirringThe product was stirred in i-Pr2O/heptane (1:1, 100 mL)
11. filtrationThe solid was filtered
12. customoff dried in vacuo

ORD record

ord-fb4ed8e93e644695b7e9da3591ad46fd

Source dataset

uspto-grants-2016_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09302988B2