Tetrabutylammonium Fluoride → (2S)-ethyl 2-(2-amino-7-(8-fluoro-5-methylchroman-6-yl)-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-(tert-butoxy)acetate

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A mixture of (2S)-ethyl 2-tert-butoxy-2-(7-(8-fluoro-5-methylchroman-6-yl)-5-methyl-2-((2-(trimethylsilyl)ethoxy)carbonylamino)pyrazolo[1,5-a]pyrimidin-6-yl)acetate (2.3 g, 3.74 mmol), 1M TBAF (4.49 mL, 4.49 mmol) in THF (20 mL) was stirred at rt for 3 h. It was then concentrated, diluted with water, and extracted with EtOAc. The organic phase was washed with water, dried over MgSO4, filtered and concentrated to yield 1.5 g (85%) of (2S)-ethyl 2-(2-amino-7-(8-fluoro-5-methylchroman-6-yl)-5-methylpyrazolo[1,5-a]pyrimidin-6-yl)-2-(tert-butoxy)acetate as a oil which solidified upon standing for one day. 1H NMR (500 MHz, CDCl3) δ 6.87 (d, J=10.56 Hz, 1H), 5.88 (s, 1H), 4.85 (s, 1H), 4.33 (t, J=5.04 Hz, 2H), 4.08-4.14 (m, 4H), 2.76 (t, J=6.38 Hz, 2H), 2.71 (s, 3H), 2.13-2.21 (m, 2H), 1.87 (s, 3H), 1.20 (t, J=7.17 Hz, 3H), 1.16 (s, 9H). LCMS (M+H)=471.36.

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