Sodium Hydroxide → 3-Dipropylamino-5-aminochroman

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Reaction Steps

3-Dipropylamino-5-methyloxycarbonylchroman (Example 2; 1.0 g, 3.4 mmol) was dissolved in methanol (20 ml). Sodium hydroxide (0.16 g, 4.1 mmol) in water (1.0 ml) was added and the solution was refluxed with nitrogen overnight. The solution was evaporated to dryness, toluene (20 ml) was added and again the solution was evaporated to dryness. The residue was dissolved in toluene 20 ml, diphenylphosphoryl azid (1.87 g, 6.8 mmol) was added and the solution was refluxed for 2 hours. Methanol (2.0 ml) was added and reflux was continued for 4 hours. The solution was cooled, washed with water and extracted with dilute HCl (aq.). The acidic water phase was neutralized NaOH (aq.) and extracted with toluene. The toluene-phase was dried with sodium sulphate and evaporated to dryness. The residue was dissolved in ethanol containing 10% NaOH (20 ml) and the solution was refluxed overnight. The solution was cooled and diluted with toluene. Washing with water, drying of the organic phase and evaporation to dryness afforded the title compound as an oil, which was converted to a dihydrochloride salt. Mp 173°-174° C.

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