tert-butyl 4-(2-fluoroethyl)piperazine-1-carboxylate

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:30.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Crude 1,1-dimethylethyl 4-(2-fluoroethyl)-1-piperazinecarboxylate was dissolved in 40 mL of MeOH and 40 mL 37% HCl. Reaction was stirred for 1 h. Carefully neutralized with solid K2CO3 and concentrated in vacuo being careful not to heat the H2O bath past 30° C. The resulting residue was taken up in diethyl ether and the solids were filtered and washed with diethyl ether and DCM several times. Filtrate was concentrated in vacuo, again being careful not to heat the H2O bath past 30° C., to give desired product 1-(2-fluoroethyl)piperazine (5.2 g, 73% over 2 steps) which was used without further purification. 1H NMR (400 MHz, DMSO-d6) δ ppm 4.40-4.57 (m, 2H), 2.64-2.73 (m, 4H), 2.53-2.61 (m, 1H), 2.46-2.53 (m, 2H), 2.29-2.40 (m, 4H). Reaction concentrated in vacuo the solids were filtered washed with diethyl ether and DCM several times Filtrate was concentrated in vacuo to heat the H2O bath past 30° C.

Conditions: temp:85.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a sealed tube, 1,1-dimethylethyl 1-piperazinecarboxylate (10.0 g, 54.0 mmol) was dissolved in 100 mL of THF. K2CO3 (11.2 g, 81.0 mmol) and 1-fluoro-2-iodoethane (11.3 g, 64.8 mmol) were added and the reaction was heated to 85° C. for 16 h. The reaction was cooled to rt and solids were filtered and washed with DCM. The filtrate was concentrated in vacuo being careful not to heat the H2O bath past 30° C. The resulting crude product, 1,1-dimethylethyl 4-(2-fluoroethyl)-1-piperazinecarboxylate was carried on to the next step without further purification. 1H NMR (400 MHz, DMSO-d6) δ ppm 4.48 (dt, JHF=47.8 Hz, J=4.9 Hz, 2H), 3.24-3.28 (m, 4H), 2.57 (dt, JHF=28.7, J=4.9 Hz, 2H), 2.31-2.36 (m, 4H), 1.34 (s, 9H). The reaction was cooled to rt solids were filtered washed with DCM The filtrate was concentrated in vacuo to heat the H2O bath past 30° C The resulting crude product, 1,1-dimethylethyl 4-(2-fluoroethyl)-1-piperazinecarboxylate was carried on to the next step without further purification

Conditions: temp:50.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To the solution of 1,1-dimethylethyl 4-(2-fluoroethyl)-1-piperazinecarboxylate (from a different batch than previously described) (160 g, 0.68 mol) in MeOH (500 mL) was added HCl/MeOH (5M, 1000 mL), and the mixture was heated at 50° C. for 1 h before evaporating most of the solvent. The residue was filtered and washed with MeOH to give the title compound of Step B (122 g, 87% yield). 1H NMR (400 MHz, D2O) δ ppm 3.60-3.78 (m, 10H), 4.80 (t, J=4.4 Hz, 1H), 4.92 (t, J=4.4 Hz, 1H) before evaporating most of the solvent The residue was filtered washed with MeOH

Conditions: temp:85.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a sealed tube, 1,1-dimethylethyl 1-piperazinecarboxylate (10.0 g, 54.0 mmol) was dissolved in 100 mL of THF. K2CO3 (11.2 g, 81.0 mmol) and 1-fluoro-2-iodoethane (11.3 g, 64.8 mmol) were added and the reaction was heated to 85° C. for 16 h. The reaction was cooled to rt and solids were filtered and washed with DCM. The filtrate was concentrated in vacuo being careful not to heat the H2O bath past 30° C. The resulting crude product, 1,1-dimethylethyl 4-(2-fluoroethyl)-1-piperazinecarboxylate was carried on to the next step without further purification. 1H NMR (400 MHz, DMSO-d6) δ ppm 4.48 (dt, JHF=47.8 Hz, J=4.9 Hz, 2H), 3.24-3.28 (m, 4H), 2.57 (dt, JHF=28.7, J=4.9 Hz, 2H), 2.31-2.36 (m, 4H), 1.34 (s, 9H). The reaction was cooled to rt solids were filtered washed with DCM The filtrate was concentrated in vacuo to heat the H2O bath past 30° C The resulting crude product, 1,1-dimethylethyl 4-(2-fluoroethyl)-1-piperazinecarboxylate was carried on to the next step without further purification

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Add 4 N HCl in 1,4-dioxane (21.52 mL, 86.1 mmol) to a stirred solution of 4-(2-fluoro-ethyl)-piperazine-1-carboxylic acid tert-butyl ester (2.00 g, 8.61 mmol) in dry dichloromethane (60 mL) at room temperature under nitrogen. Stir overnight under nitrogen. Concentrate the reaction under reduced pressure to afford the title compound (1.78 g). ES/MS m/z 133 (M+1). Concentrate the reaction under reduced pressure

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Charge a reaction vessel with N-tert-butoxycarbonylpiperazine (1.600 g, 8.590 mmol), potassium carbonate (3.56 g, 25.77 mmol), sodium iodide (catalytic) (10 mg, 66.7 mmol), 1,4-dioxane (20 mL), and 1-bromo-2-fluoroethane (704.0 μL, 9.45 mmol). Heat the mixture with stirring at reflux temperature overnight. Upon reaction completion, cool to room temperature and concentrate under reduced pressure. Partition the resulting residue with ethyl acetate and water. Separate the organic layer and dry over anhydrous sodium sulfate, filter, and concentrate under reduced pressure to afford pure 4-(2-fluoro-ethyl)-piperazine-1-carboxylic acid tert-butyl ester. GC-MS m/z 232 (M). Heat the mixture at reflux temperature overnight Upon reaction completion concentrate under reduced pressure Partition the resulting residue with ethyl acetate and water Separate the organic layer dry over anhydrous sodium sulfate filter concentrate under reduced pressure

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Trifluoroacetic acid (3 ml, 17.5 mmol) was added to a solution of 4-(2-fluoroethyl)-piperazine-1-carboxylic acid tert-butyl ester (350 mg, 1.5 mmol) in methylene chloride (12 ml). The reaction mixture was stirred at ambient temperature for 40 minutes, before the solvent was evaporated under high vacuum. The residue was azeotroped with toluene to give 1-(2-fluoroethyl)-piperazine diTFA salt (377 mg, 96%). was evaporated under high vacuum The residue was azeotroped with toluene