N-ETHYLBENZISOXAZOLIUM TETRAFLUOROBORATE

Recrystallise it from MeCN/EtOAc to give magnificent crystals. It is not hygroscopic but on long exposure to moisture it etches glass. It is light-sensitive and should be stored in brown glass bottles. UV (H2O), max 258nm ( 13 100) and 297nm ( 2 900), IR (CH2Cl2):max 1613 (C=N) and 1111-1000 (BF 4 ) [UV, IR, NMR: Kemp & Woodward Tetrahedron 21 3019 1965].