Perchloric Acid → (S)-ethyl 2-(7-(4-(allyloxy)-4-methylpiperidin-1-yl)-2-(3-bromophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-(tert-butoxy)acetate

Participants

Reaction Steps

To a stirred solution of (S)-ethyl 2-(7-(4-(allyloxy)-4-methylpiperidin-1-yl)-2-(3-bromophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-hydroxyacetate (8.5 g, 15.64 mmol) in DCM (250 mL) and t-butyl acetate (175 mL) was added perchloric acid (4.03 mL, 46.9 mmol) at rt. After 3 h, the reaction mixture was diluted with DCM (100 mL), carefully quenched with sat. NaHCO3 (50 mL), organic layer separated and washed with brine (100 mL), dried (Na2SO4), filtered and concentrated to give yellow liquid. This was purified by flash column chromatograpgy on silica gel column using (10-50% EtOAc/Hex as eluant) to afford the desired (S)-ethyl 2-(7-(4-(allyloxy)-4-methylpiperidin-1-yl)-2-(3-bromophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-(tert-butoxy)acetate (5 g, 8.34 mmol, 53.3% yield) as light yellow solid. 3 g of starting material was also recovered. 1H NMR (500 MHz, CDCl3) δ 8.23-8.11 (m, 1H), 7.94 (d, J=7.7 Hz, 1H), 7.56-7.51 (m, 1H), 7.33 (t, J=7.9 Hz, 1H), 6.81 (s, 1H), 6.10 (br. s., 1H), 6.00 (br. s., 1H), 5.49 (d, J=16.6 Hz, 1H), 5.28 (d, J=10.2 Hz, 1H), 4.30-4.14 (m, 2H), 4.10-4.00 (m, 2H), 2.65 (s, 3H), 2.09-1.85 (m, 3H), 1.74 (br. s., 1H), 1.38 (s, 3H), 1.28-1.16 (m, 12H). 4 missing piperidine hydrogens. LCMS (M+H)=601.5.

Provenance & Evidence