反应详情

In a dried flask under N 2, a suspension of 47.2 g (1.10 mol) of 56 percent by weight sodium hydride in mineral oil in 1000 ml of tetrahydrofuran was stirred as 209.4 g (1.15 mol) of trimethyl phosphonoacetate was added over 2.25 hr. The white paste was stirred for 0.25 hr and then a solution of 132.2 g (0.50 mol) of (±)-6-acetoxy-2-hydroxy-2,5,7,8-tetra- methylchroman in 1000 ml of tetrahydrofuran was added over 0.50 hr. The pale yellow suspension was stirred at 23° C for 18 hours and then heated at reflux for 4.0 hours. The cooled solutions from two such reactions were stripped of solvent and worked up and dried by the procedure given in Example 1 to give a cloudy red-brown oil containing (±)-methyl-(6-acetoxy-2, 5,7,8-tetramethylchroman-2-yl) acetate. To a solution of this material in 2000 ml. of ethanol, there was added 2000 ml. of H 2 0 and 240 g. (6.0 mol.) of NaOH. The solution was stirred at 23° C. for 4 hours, washed with petroleum ether (b.p. 30°-60° C.), diluted with 6000 ml. of ice-H 2 O and acidified by the dropwise addition over 0.50 hour of 600 ml. of concentrated aqueous HCl. The solid was removed by filtration, washed with H 2 O and crystallized from ethanol-H 2 O to give (±) -(6-hydroxy-2,5,7,8- tetramethylchroman-2-yl) acetic acid as a light tan powder: m.p. 168°-171° C.

1. additionwas added over 2.25 hr
2. stirringThe pale yellow suspension was stirred at 23° C for 18 hours
3. temperatureheated
4. temperatureat reflux for 4.0 hours
5. customdried by the procedure
6. customto give a cloudy red-brown oil
7. stirringThe solution was stirred at 23° C. for 4 hours
8. washwashed with petroleum ether (b.p. 30°-60° C.)
9. additiondiluted with 6000 ml
10. additionof ice-H 2 O and acidified by the dropwise addition over 0.50 hour of 600 ml
11. customThe solid was removed by filtration
12. washwashed with H 2 O
13. customcrystallized from ethanol-H 2 O