Potassium Hydroxide → (3,4-dihydro-6-methoxy-2,5,7,8-tetramethyl-2H-benzopyran-2-yl)acetic acid
Reaction equation
C([O:3][C:4](=[O:27])[CH:5]([C:11]1([CH3:26])[CH2:16][CH2:15][C:14]2[C:17]([CH3:25])=[C:18]([O:23][CH3:24])[C:19]([CH3:22])=[C:20]([CH3:21])[C:13]=2[O:12]1)C(OCC)=O)C.[OH-].[K+]>C(O)CO.O>[CH3:24][O:23][C:18]1[C:19]([CH3:22])=[C:20]([CH3:21])[C:13]2[O:12][C:11]([CH3:26])([CH2:5][C:4]([OH:27])=[O:3])[CH2:16][CH2:15][C:14]=2[C:17]=1[CH3:25]Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Procedure
A mixture of 1.29 g (3.41 mmoles) of rac.-3,4-dihydro-2,5,7,8-tetramethyl-6-methoxy-2H-1-benzopyran-2-ylpropanedioic acid diethyl ester, 1.68 g of potassium hydroxide, and 75 ml of 9:1 parts by volume ethylene glycol-water mixture was stirred and refluxed for 6 hours. The resulting mixture was poured on ice and extracted with ether (the ether extract was discarded). The aqueous solution was acidified with 3N HCl and the precipitated acid was extracted 3 times with ether. The combined ether extracts were washed with brine, dried (MgSO4), filtered and concentrated in vacuo. Purification of the residue by preparative thick layer chromatography gave 0.72 g (75.9%) of rac.-3,4-dihydro-6-methoxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-acetic acid, as a colorless solid, mp 96°-98° C. Dimethylation using the procedure of example 14 gives rac.-3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-acetic acid which can be converted to alpha-tocopherol as described in Helv. Chim. Acta. 59, 290 (1976).