tert-Butyl acetate → (S)-Methyl 2-(2-(3-bromophenyl)-7-chloro-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-(tert-butoxy)acetate

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Reaction Steps

A mixture of (S)-methyl 2-(2-(3-bromophenyl)-7-chloro-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-hydroxyacetate (7.81 g, 19.02 mmol), t-butylacetate (160 mL) in DCM (330 mL) was added perchloric acid (3.43 mL, 57.1 mmol) and the mixture was stirred at rt for 3 h. It was then quenched with sat.aq.NaHCO3 (adjusted to pH=7-8 by the addition of solid NaHCO3). This mixture was diluted with EtOAc and the organic phase was washed with water. The organic phase was dried (MgSO4), filtered, and concentrated in vacuo to obtain ˜7 g of crude product as an oil. Filtration through 70 g of silica gel eluting with CH2Cl2 gave (S)-methyl 2-(2-(3-bromophenyl)-7-chloro-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-(tert-butoxy)acetate (5.71 g, 12.23 mmol, 64.3% yield). 1H NMR (400 MHz, CDCl3) δ 8.20 (t, J=1.6 Hz, 1H), 7.95 (dt, J=7.8, 1.1 Hz, 1H), 7.63-7.53 (m, 1H), 7.37 (t, J=7.9 Hz, 1H), 6.94 (s, 1H), 5.69 (s, 1H), 3.76 (s, 3H), 2.70 (s, 3H), 1.30 (s, 9H). LCMS (M+H)=466 and 468.

Provenance & Evidence