反应详情

A mixture of the rac.-3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-acetonitrile from Example 7 (14.8 g), 10.2 g (155 mmoles) of 85% KOH, 9 ml of water and 83 ml of ethylene glycol was stirred and refluxed for 17.5 hr. The resulting solution was cooled to room temperature and diluted with 250 ml of water. The pH of the solution was adjusted to 8 with 3 N aqueous HCl and the resulting mixture was extracted with three portions of ether (the ether extracts were discarded). The aqueous phase was further diluted with water and acidified by the dropwise addition of 3 N aqueous HCl. The resulting precipitate was filtered off and washed with water, then dried under high vacuum at room temperature for 24 hr to give 8.05 g (75%) of rac.-(6-hydroxy-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)acetic acid as a tan solid m.p. 169°-172° C.,

1. temperaturerefluxed for 17.5 hr
2. extractionthe resulting mixture was extracted with three portions of ether (the ether extracts
3. additionThe aqueous phase was further diluted with water
4. additionacidified by the dropwise addition of 3 N aqueous HCl
5. filtrationThe resulting precipitate was filtered off
6. washwashed with water
7. customdried under high vacuum at room temperature for 24 hr