Reaction #2045032

Reaction equation

(4-Aminophenoxy)acetic acid 2-[2-(4-aminophenoxy)acetoxy]ethyl ester

(4-Amino-phenoxy)-acetic acid-2-[2-(4-amino-phenoxy)-acetoxy]-ethyl ester

dioxane

triphosgene

dioxane

→

44

Yield 44.2%

(4-Isocyanatophenoxy)acetic acid-2-[2-(4-isocyanatophenoxy)acetoxy]ethyl ester

Yield 44.2%

Conditions

Workup

1. 1
   Temperatureand cooled to below 20° C
2. 2
   Temperaturemaintained for 2½ hours
3. 3
   workup.DISTILLATIONThe condenser was then arranged for distillation and solvent
4. 4
   Otherremoved by distillation at atmospheric pressure until the volume of the reaction mixture
5. 5
   workup.ADDITIONFresh dry dioxane (50 ml) was added
6. 6
   workup.DISTILLATIONthe solvents were distilled off under vacuum
7. 7
   OtherThe residue was re-evaporated two times from dry dioxane
8. 8
   Otherto give crude 44
9. 9
   OtherCrude 44 was recrystallised from a mixture of toluene:hexane (1:3)

Procedure

(4-Aminophenoxy)acetic acid 2-[2-(4-aminophenoxy)acetoxy]ethyl ester 43 (5 g, 14.3 mmol) was dissolved in dry dioxane (80 ml) under nitrogen atm. and cooled to below 20° C. A solution of triphosgene (7 g, 23.6 mmol) in dry dioxane (20 ml) was added drop wise. The mixture was heated slowly to 75-80° C. and maintained for 2½ hours. The condenser was then arranged for distillation and solvent removed by distillation at atmospheric pressure until the volume of the reaction mixture was reduced to approximately one third. Fresh dry dioxane (50 ml) was added and the solvents were distilled off under vacuum. The residue was re-evaporated two times from dry dioxane to give crude 44. Crude 44 was recrystallised from a mixture of toluene:hexane (1:3) to give pure 44 (2.6 g, 44.2%) as a white powder. M.p: 96-98° C.

Source