2-(Benzenesulfonyl)-3-phenyloxaziridine → Ethyl 2-(7-chloro-2-(3-chlorophenyl)-3,5-dimethylpyrazolo[1,5-a]pyrimidin-6-yl)-2-hydroxyacetate

Participants

Reaction Steps

To a cold (−78° C. dry ice/acetone) stirred solution of 0.91 M KHMDS in THF (32 ml, 29.1 mmol) in additional THF (100 ml) was added ethyl 2-(7-chloro-2-(3-chlorophenyl)-3,5-dimethylpyrazolo[1,5-a]pyrimidin-6-yl)acetate (8.3 g, 21.94 mmol) in THF (100 ml), by dropwise addition over 30 min. The mixture was stirred for 20 min, and then a solution of 3-phenyl-2-(phenylsulfonyl)-1,2-oxaziridine (7.45 g, 28.5 mmol) in THF (50 ml) was added. The reaction was stirred for 2.5 hrs at −78° C. The orange reaction mixture was quenched with sat. NH4Cl (100 mL), diluted with EtOAc (300 mL), washed with water (200 mL), brine (100 mL), dried (Na2SO4), filtered and concentrated to give a yellow solid. The crude residue was loaded onto a flash silica gel column and eluted with 10%-30% EtOAc in hexanes. Product fractions were pooled and concentrated under reduced pressure, affording ethyl 2-(7-chloro-2-(3-chlorophenyl)-3,5-dimethylpyrazolo[1,5-a]pyrimidin-6-yl)-2-hydroxyacetate (5.4 g, 11.40 mmol, 51.9% yield) as a yellow solid. 1H NMR (500 MHz, CDCl3) δ: 7.89-7.84 (m, 1H), 7.74 (dt, J=7.2, 1.6 Hz, 1H), 7.44-7.36 (m, 2H), 5.73 (s, 1H), 4.32-4.26 (m, 2H), 3.65 (br. s., 1H), 2.63 (s, 3H), 2.51 (s, 3H), 1.24 (t, J=7.02 Hz, 3H). LCMS (M+H)=394.06.

Provenance & Evidence