Potassium Phosphate, Tribasic → tert-butyl 5-(4-(methoxycarbonyl)phenyl)-2H-1,4-oxazine-4(3H)-carboxylate

Participants

Reaction Conditions

Reaction Steps

Tert-butyl 5-((diphenoxyphosphoryl)oxy)-2H-1,4-oxazine-4(3H)-carboxylate (20 g, 46.1 mmol) and (4-methoxycarbonylphenyl)boronic acid (9.0 g, 49.8 mmol) were dissolved in acetonitrile (300 ml). A solution of potassium phosphate (19.6 g, 92.3 mmol) in water (75 ml) was added, followed by bis(tri-tert-butylphosphine)palladium (0) (2.36 g, 4.61 mmol). Nitrogen was bubbled through the stirred mixture for 40 minutes, then the mixture was heated to 65° C. for 2 hours. The mixture was cooled and diluted with ethyl acetate (1 L) and water (200 ml). The organic phase was separated and washed with sat NaHCO3 (3×200 ml), then brine (200 ml), dried (MgSO4), filtered and partially concentrated to 50 ml. Solid material was removed by filtration (700 mg). The filtrate was concentrated to a brown solid. The crude was purified on silica gel, eluting with 0-10% ethyl acetate/petrol. This gave the title compound as a white solid (7.4 g, 50%); 1H-NMR (CDCl3) 1.13 (9H, s), 3.80 (2H, t), 3.93 (3H, s), 4.20 (2H, t), 6.36 (1H, s), 7.31 (2H, d), 7.98 (2H, d); 13C-NMR (CDCl3) 27.7, 41.5, 52.0, 66.8, 124.5, 129.6, 133.7; MS ES(+) 264.1 (M+-tBu); Anal. Calcd for C12H21NO5: C, 63.94; H, 6.63; N, 4.38. Found: C, 63.83; H, 6.53; N, 2.23.

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