Hydrochloric Acid → 7-chloro-2,3-dihydro-1H-pyrido[2,3-b][1,4]thiazine

Participants

Reaction Conditions

Reaction Steps

7-Chloro-1H-pyrido[2,3-b][1,4]thiazin-2(3H)-one (1.2 g, 5.98 mmol) was suspended in THF (5.0 mL), cooled to 0° C. and treated with BH3-THF (47.8 mL, 47.8 mmol, 1.0M in THF). The reaction was stirred at rt for 30 min and heated at 45° C. for 2 h. At this time more BH3-THF (47.8 mL, 47.8 mmol, 1.0M in THF) was added and the reaction was heated at 45° C. for 16 h. The reaction was then treated with 100 mL of MeOH and it was refluxed for 30 min. After this time the reaction was cooled to rt and acidified to pH 2 with aqueous HCl. The reaction was then basified to pH 14 with aqueous NaOH and the mixture was then extracted with EtOAc (3×80 mL). The separated organic layer was dried over MgSO4, filtered and evaporated in vacuo. The resulting white solid was triturated with hot EtOAc and the mixture was allowed to cool to rt for 20 min. After filtration, the precipitate was dried over MgSO4 and evaporated in vacuo to give 7-chloro-2,3-dihydro-1H-pyrido[2,3-b][1,4]thiazine as a white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 7.60 (1H, d, J=2.3 Hz), 6.85 (1H, d, J=2.2 Hz), 6.52 (1H, t, J=3.0 Hz), 3.43-3.50 (2H, m), 3.04-3.15 (2H, m). Mass Spectrum (ESI) m/e=187.0 (M+1).

Provenance & Evidence