(R)-1-methyl-3,3-diphenylhexahydropyrrolo[1,2-c][1,3,2]oxazaborole toluene → (S)-ethyl 6-(2-ethoxy-1-hydroxy-2-oxoethyl)-7-iodo-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a stirred yellow solution of ethyl 6-(2-ethoxy-2-oxoacetyl)-7-iodo-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate (6.4 g, 14.8 mmol) in anhydrous toluene (300 mL) was added 1.1M (R)-1-methyl-3,3-diphenylhexahydropyrrolo[1,2-c][1,3,2]oxazaborole/toluene (5.40 mL, 5.94 mmol). The mixture was cooled to −35° C. and a solution of 50% catechoborane/toluene (5.09 mL, 20.78 mmol) was added over the course of 10 min. After 30 min, the reaction mixture was slowly warmed to −15° C. and stirred for additional 2 h, then diluted with EtOAc (600 mL) and sat. aq. Na2CO3 (100 mL). The mixture was stirred vigorously for 30 min, and the organic phase was washed with sat. aq. Na2CO3 (2×100 mL), dried (Na2SO4), filtered, concentrated. The residue was purified by silica gel chromatography (5-100% EtOAc/hexane) to afford the desired (S)-ethyl 6-(2-ethoxy-1-hydroxy-2-oxoethyl)-7-iodo-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate (5.3 g, 12.2 mmol, 82% yield) as an off-white solid. 1H NMR (500 MHz, CDCl3) δ 7.33 (s, 1H), 5.75 (d, J=2.4 Hz, 1H), 4.52 (qd, J=7.1, 1.1 Hz, 2H), 4.38-4.29 (m, 2H), 3.59 (d, J=2.4 Hz, 1H), 2.63 (s, 3H), 1.48 (t, J=7.2 Hz, 3H), 1.27 (t, J=7.2 Hz, 3H). LCMS (M+H)=434.2.

Provenance & Evidence