1,4-Dioxane → 2-(4-Isocyanatophenoxy)-propionic acid 2-[2-(4-isocyanatophenoxy)-propionyloxy]-ethyl ester

Participants

Reaction Conditions

Reaction Steps

2-(4-Aminophenoxy)-propionic acid 2-[2-(4-aminophenoxy)-propionyloxy]-ethyl ester 32 (5.3 g, 13.6 mmol) was dissolved in dry dioxane (80 ml) under nitrogen atmosphere 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 reaction mixture volume was reduced to approximately one third. Fresh dry dioxane (50 ml) was added and the solvent then distilled off under vacuum. The residue was re-evaporated two times from dry dioxane to give pure 33 (4 g, 66.5%) as a light brown liquid.

Provenance & Evidence