tert-Butyl piperazine-1-carboxylate → (R)-tert-butyl 4-(7-acetoxy-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a solution of (5R)-4-chloro-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-7-yl acetate (0.5 g, 2.2 mmol) in NMP (10 mL) was added 1-Boc-piperazine (0.9 g, 4.8 mmol). The reaction mixture was heated to 110° C. for 12 hours. After cooling, the reaction mixture was diluted with ethyl acetate (200 mL) and washed with water (6×100 mL). The organic phase was dried and concentrated. The residue was purified by silica gel chromatography, eluting with ethyl acetate to give tert-butyl 4-((5R)-7-acetoxy-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate (0.6 g, 72%). 1H NMR (CDCl3, 400 MHz) δ 8.60 (d, 1H), 6.05-5.90 (m, 1H), 3.80-3.30 (m, 9H), 2.84 (m, 1H), 2.20-(m, 1H), 1.49 (s, 9H), 1.29-1.20 (m, 3H). MS (APCI+) [M+H]+377. The resulting mixture of the diastereomers was purified by chiral separation HPLC (Chiralcel ODH column, 250×20 mm, Hexane/EtOH 60:40, 21 mL/min). The first peak (RT=3.73 min) gave the tert-butyl 4-((5R,7R)-7-acetoxy-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate (0.144 g, 24%). The second peak (RT=5.66 min) gave the tert-butyl 4-((5R,7S)-7-acetoxy-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate (0.172 g, 29%). MS (APCI+) [M+H]+377.

Provenance & Evidence