Thionyl Chloride → 5,6-difluoro-2,4-dihydro-1H-3,1-benzoxazine-2,4-dione

Participants

Reaction Steps

A solution of 108 ml of thionyl chloride in 300 ml of tetrahydrofuran was added dropwise while cooling with ice to a solution of 100 g (366 mmol) of 2-(tert.-butoxycarbonyl)amino-5,6-difluorobenzoic acid in 1.5 I of dry tetrahydrofuran, whereupon the mixture was stirred at room temperature for 16 hours. The brown solution was evaporated and the brown solid obtained was triturated with methylene chloride. The beige powder obtained was filtered off and dried in a high vacuum. There were obtained 56.5 g (77%) of 5,6-difluoro-2,4-dihydro-1H-3,1-benzoxazine-2,4-dione as a beige powder of m.p. >240°.

Provenance & Evidence