Cesium carbonate → Tert-butyl 4-(2-(4-ethoxy-4-oxobutoxy)phenyl)-piperazine-1carboxylate

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of tert-butyl 4-(2-hydroxyphenyl)-piperazine 20 (1 g, 0.0035 mol.) and cesium carbonate (2.34 g, 0.0071 mol.) in 5 mL of DMF anhydrous was added a solution of ethyl 4-bromobutanoate (6a) at rt. The resulting mixture was heated at 70° C. overnight (12 h). The progress of the reaction was monitored by thin layer chromatography (TLC). After the reaction was complete, the reaction mixture was diluted with 25 mL of ethyl acetate and filtered to remove cesium carbonate. The filtrate was washed with saturated aqueous NaHCO3 solution, dried over Na2SO4 and evaporated to give tert-butyl 4-(2-(4-ethoxy-4-oxobutoxy)phenyl)-piperazine-1carboxylate 21a which was purified by silica gel chromatography using a gradient elution of ethyl acetate and hexane. Colorless oil (1.1 g, 78%). 1H NMR (400 MHz, CDCl3): δ 1.25 (t, J=6.4 Hz, 3H); 1.45 (s, 9H); 2.14 (q, J=7.2 Hz, 2H); 2.53 (t, J=7.2Hz, 2H); 3.00 (br s, 4H); 3.58 (br s, 4H); 4.04 (t, J=6.4 Hz, 2H); 4.12 (q, J=6.4 Hz, 2H); 6.84-6.97 (m, 4H).

Provenance & Evidence