Triethylamine → 2,3-Dihydro-1,4-benzodioxin-5-amine

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Reaction Steps

Triethylamine in acetone was added dropwise to the solution of 2,3-dihydrobenzo[b][1,4]dioxine-5-carboxylic acid (360 mg, 2 mmol) in water and acetone at 0° C. To the mixture was added ethyl carbonochloridate in acetone slowly. The mixture was stirred for 4 h then a solution of NaN3 (196 mg, 3.02 mmol) in water was added dropwise. The reaction mixture was stirred for 1 h then it was poured into ice water and extracted with Et2O. The combined organic extracts were washed with brine, dried with MgSO4, and concentrated in vacuo. The residue was dissolved in anhydrous toluene and the mixture was heated on a steam bath until nitrogen evolution had ceased. The toluene was then removed in vacuo and 20% aq HCl (4 mL) was added and the solution was heated to reflux and stirred overnight. The reaction was concentrated under reduced pressure. The residue was dissolved in water, made strongly alkaline by the addition of 40% aq NaOH, then extracted with Et2O. The combined organic extracts were washed with brine, dried by MgSO4, and purified by flash chromatography on silica gel column (PE:EtOAc=5:1) to give 2,3-dihydrobenzo[b][1,4]dioxin-5-amine (intermediate 60) (270 mg, 70%). HPLC: 99%, RT 1.214 min. MS (ESI) m/z 152.1 [M+H]+.

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