Reaction #715754

Reaction equation

biphenyl-3,3′,4,4′-tetraamine

4-aminobenzoic acid

water

→

product

Yield 97.5%

4,4′-(1H,3′H-5,5′-Bibenzo[d]imidazole-2,2′-diyl)dianiline

Yield 97.5%

Solvents

MeOH

Conditions

Workup

1. 1
   workup.ADDITIONwas added portionwise
2. 2
   workup.STIRRINGThe mixture was stirred at 200° C. for 2.5 h
3. 3
   TemperatureThe mixture was cooled (to <100° C.)
4. 4
   workup.STIRRINGThe resulting mixture was stirred until a uniform green precipitate
5. 5
   Otherhad formed
6. 6
   FiltrationThe solid was filtered off
7. 7
   Washwashed with aqueous K2CO3 and water
8. 8
   Otherdried under suction
9. 9
   OtherThe crude product was purified by column chromatography (99:1 EtOAc-NEt3 to 89:10:1 EtOAc-MeOH-NEt3)
10. 10
    Otherto afford a yellow solid
11. 11
    Concentration1M HCl, and then concentrated in vacuo
12. 12
    workup.STIRRINGstirred in aqueous NaHCO3
13. 13
    FiltrationThe solid was filtered
14. 14
    Washwashed with water
15. 15
    Otherdried (vacuum oven)

Procedure

A homogenous mixture of biphenyl-3,3′,4,4′-tetraamine (500 mg, 2.34 mmol) and 4-aminobenzoic acid (640 mg, 4.67 mmol) was added portionwise to stirred PPA (20 mL) at 200° C. The mixture was stirred at 200° C. for 2.5 h. The mixture was cooled (to <100° C.) and poured into water. The resulting mixture was stirred until a uniform green precipitate had formed. The solid was filtered off and washed with aqueous K2CO3 and water, then dried under suction. The crude product was purified by column chromatography (99:1 EtOAc-NEt3 to 89:10:1 EtOAc-MeOH-NEt3) to afford a yellow solid. This was dissolved in MeOH and 1M HCl, and then concentrated in vacuo. The material was then ground to a fine powder and stirred in aqueous NaHCO3. The solid was filtered, washed with water and dried (vacuum oven) to give the product as a yellow solid (475 mg, 49%).

Source