1-(tert-Butoxycarbonyl)-2-pyrroleboronic Acid → tert-Butyl 2-cyano-5-(2,4,4-trimethyl-1,4-dihydro-2H-3,1-benzoxazin-6-yl)-1H-pyrrole-1-carboxylate

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Reaction Conditions

Reaction Steps

tert-Butyl-5-(2,4,4-trimethyl-1,4-dihydro-2H-3,1-benzoxazin-6-yl)-1H-pyrrole-1-carboxylate was prepared according to the coupling procedure for Example 17 from 6-bromo-2,4,4-trimethyl-1,4-dihydro-2H-3,1-benzoxazine and 1-t-butoxycarbonylpyrrol-2-yl boronic acid. To a solution of tert-butyl-5-(2,4,4-trimethyl-1,4-dihydro-2H-3,1-benzoxazin-6-yl)-1H-pyrrole-1-carboxylate (1 g, 2.9 mmol) in anhydrous THF (20 mL) was added at −78° C. under nitrogen chlorosulfonyl isocyanate (0.35 mL, 4.0 mmol). The mixture was kept stirring at −78° C. under nitrogen for 2 hours, treated with anhydrous DMF (5 mL), and allowed to warm to room temperature. Aqueous ammonium sulfate solution (50 mL) and ethyl acetate (100 mL) was added and organic layer was separated, dried (MgSO4), and evaporated. The residue was purified by a silica gel column chromatography (hexane:ethyl acetate/4:1) to afford the title compound as a white solid (0.019 g, 1.78%): 1H-NMR (DMSO-d6) δ 7.48 (d, 1H, J=2.0 Hz), 7.36 (dd, 1H, J=8.3, 2.0 Hz), 7.32 (d, 1H, J=3.6 Hz), 7.14 (d, 1H, J=8.3 Hz), 6.46 (d, 1H, J=4.0 Hz), 5.35 (q, 1H, J=5.2 Hz), 1.58 (d, 3H, J=5.6 Hz), 1.56 (s, 3H), 1.51 (s, 3H), 1.38 (s, 9H); MS (ESI) m/z 366 [M−H]−.

Provenance & Evidence