反应详情

A mixture of methyl 2-hydroxyimino-2-(isothiazol-4-yl)acetate (anti isomer) (3.41 g.), 36% aqueous solution of formaldehyde (24 ml.), conc. hydrochloric acid (12 ml.) and water (24 ml.) was stirred for 7 hours at 90° to 100° C. The reaction mixture was allowed to stand overnight in a refrigerator to precipitate crystals. The crystals were collected by filtration, washed with a small amount of ice-water and then dried to give 2-(isothiazol-4-yl)glyoxylic acid (2.09 g.). The mother liquor was extracted with ethyl acetate to give the same compound (0.34 g.), mp 145° to 148° C.

1. waitto stand overnight in a refrigerator
2. customto precipitate crystals
3. filtrationThe crystals were collected by filtration
4. washwashed with a small amount of ice-water
5. customdried