A mixture of (R)-2,3-dihydrobenzo[1,4]dioxine-2-carboxylic acid (167 mg, 0.93 mmol), thionyl chloride (338 μl, 551 mg, 4.63 mmol) and dry toluene was heated at 95° C. for 1.5 h and then evaporated to dryness. Toluene was added and the evaporation was repeated. The evaporation residue was dissolved in DCM (2 ml) and added slowly to a cold solution (0° C.) of 3-benzo[1,3]dioxol-5-yl-piperidine HCl (224 mg, 0.93 mmol) and DIPEA (0.324 ml, 240 mg, 1.85 mmol) in DCM (5 ml). The reaction mixture was stirred for 1 h 45 min at RT. Water was added, layers were separated and the organic phase was washed twice with 1 M HCl and sat. NaHCO3. The organic phase was dried (Na2SO4), filtered and evaporated to give 290 mg of the title compound.
