Phosgene → 7-isocyanato-4-methyl-2H-chromen-2-one

Participants

Reaction Conditions

Reaction Steps

A 200-mL three-neck flask fitted with a dry ice condenser and magnetic stirrer was charged with a solution of 20% phosgene in toluene solution (2.0 mL) and dioxane (80 mL). To this mixture was added 7-amino-4-methyl-2H-chromen-2-one (2.00 g, 11.4 mmol). The mixture was stirred at 100° C. for 12 h. The initial yellow colour disappeared and a white solid precipitated. An additional 20% phosgene in toluene solution (7.0 mL) was added and the mixture heated for an additional 5 h, at which time the solution cleared. Excess phosgene and traces of HCl was removed by bubbling nitrogen gas through the solution. The cloudy solution was filtered to remove unreacted 7-amino-4-methyl-2H-chromen-2-one and concentrated to give 76 (0.5 g, 25%) as a white solid. H1 NMR (500 MHz, CDCl3): δ=7.50 (1H, d, J=7.40 Hz, ArH), 7.46 (2H, s, ArH), 6.20 (1H, s, ArH), 2.35 (3H, s, CH3): ir (CH2CL2) 2314 (N═C═O), 1726 and 1615 cm−1.

Provenance & Evidence