Pyrazolidine dihydrochloride → 2-(2-chlorobenzyl)-3-(2-methylsulfanyl-pyrimidin-4-yl)-6,7-dihydro-5H-pyrazolo[1,2-a]pyrazol-1-one

Participants

Reaction Steps

To a solution of 2-(2-chlorobenzyl)-3-(2-methylsulfanyl-pyrimidin-4-yl)-3-oxo-propionic acid tert-butyl ester, 6 (2.0 g, 5.7 mmol)) in pyridine (40 mL) is added pyrazolidine-bishydrochloride (1.2 g, 8.1 mmol). After stirring the reaction for 10 min at room temperature, the mixture i stirred at 90° C. for 2.5 hours and then at 60° C. for 17 hours. The solution i concentrated in vacuo and the resulting curd product is purified over silica (EtOAc followed by 20% MeOH/EtOAc) to afford 460 mg (22%) of the desired product: 1H NMR (300 MHz, CDCl3) δ 8.58 (d, J=5.1 Hz, 1H), 7.42-7.2 (m, 4H), 6.96 (d, J=5.1 Hz, 1H), 4.42-4.3 (m, 4H), 4.10 (s, 2H), 2.95-2.75 (m, 2H), 2.58 (s, 3H); ESI+ MS: m/z (rel intensity) 373.0 (100, M++H).

Provenance & Evidence