Isopropyl iodide → 4-(2-Isopropoxyphenyl)piperidine

To a solution of 1-(tert-Butyloxycarbonyl)-4-(2-hydroxyphenyl)piperidine 5a (5 g) in dry THF (100 ml) was added potassium tert-butoxide (2.2 g). After stirring for 5 minutes 2-iodopropane (9 g) was added and the mixture was refluxed for 3 hours. Additionally 1.1 g of potassium tert-butoxide was added and reflux was continued overnight. After cooling to room temperature inorganic salts were filtered off and the solvents evaporated in vacuo. The remaining oil was purified by filtering through silica gel (eluted with a 7:3 mixture of heptane and ethyl acetate). Yield: 4.5 g of 1-(tert-butyloxycarbonyl)-4-[2-(2-propyloxy)phenyl]piperidine all of which was dissolved in a mixture of dichloromethane (90 ml) and trifluoroacetic acid (40 ml). After stirring for one hour at room temperature all volatile material was evaporated in vacuo. To the remaining oil was added ethyl acetate (200 ml) and water (200 ml). pH was adjusted to >10 by addition of diluted aqueous NH4OH. The organic phase was separated and washed with brine (2×50 ml). Work-up of the organic phase as above yielded 2.6 g of 4-[2-(2-propyloxy)phenyl]piperidine. A mixture of the thus isolated 1-unsubstituted piperidine (2.5 g), 1-(4-chloro-1-butyl)-3-(4-fluorophenyl)-2-imidazolidinone 2a (3.0 g), potassium carbonate (1.6 g), and potassium iodide (0.5 g) in MIBK (50 ml) was refluxed overnight. Inorganic salts were filtered off and MIBK evaporated in vacuo. The remaining crude product was purified by column chromatography on silica gel (eluted with 4% triethylamine in ethyl acetate). Pure title compound 6a crystallized from ethyl acetate. Yield: 2.6 g, mp: 130-131° C. 1H NMR (CDCl3) δ 1.45 (d, 6H); 1.60 (t, 4H); 1.70-1.90 (m, 4H); 2.00-2.15 (m, 2H); 2.40 (t, 2H); 2.90-3.05 (m, 3H); 3.35 (t, 2H); 3.45 (t, 2H); 3.75 (t, 2H); 4.55 (h, 2H); 6.80-6.90 (m, 2H); 7.00 (t, 2H); 7.10 (dt, 1H); 7.15 (dd, 1H); 7.50 (dd, 2H).