rac-3,4-dihydro-2,5,7,8-tetramethyl-2-(2-propenyl)-6-(phenylmethoxy)-2H-1-benzopyran → (6-Benzyloxy-2,5,7,8-tetramethylchroman-2-yl)acetaldehyde

HRID 580375Notes

Reaction equation

O=[O+][O-].[O:4]=O.[CH3:6][C:7]1([CH2:28][CH:29]=C)[CH2:12][CH2:11][C:10]2[C:13]([CH3:27])=[C:14]([O:19][CH2:20][C:21]3[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=3)[C:15]([CH3:18])=[C:16]([CH3:17])[C:9]=2[O:8]1>CO>[CH3:6][C:7]1([CH2:28][CH:29]=[O:4])[CH2:12][CH2:11][C:10]2[C:13]([CH3:27])=[C:14]([O:19][CH2:20][C:21]3[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=3)[C:15]([CH3:18])=[C:16]([CH3:17])[C:9]=2[O:8]1

Participants

Conditions

Temperature: -78 °C

Procedure

An ozone-oxygen gas mixture is passed into a solution of 0.67 g (2 mmoles) of rac-3,4-dihydro-2,5,7,8-tetramethyl-2-(2-propenyl)-6-(phenylmethoxy)-2H-1-benzopyran in 100 ml of methanol, with stirring, at -78° C. After the starting olefin has been consumed, the ozone flow is stopped and the solution is treated with excess dimethyl sulfide and allowed to warm to room temperature. The solution is concentrated in vacuo. The residue is chromatographed on silica gel giving rac-3,4-dihydro-2,5,7,8-tetramethyl-6-(phenylmethoxy)-2H-1-benzopyran-2-acetaldehyde, which can be converted to Vitamin E by the procedures in Helv. Chim. Acta set forth in Example 8.

Workup

customAfter the starting olefin has been consumed
additionthe solution is treated with excess dimethyl sulfide
temperatureto warm to room temperature
concentrationThe solution is concentrated in vacuo
customThe residue is chromatographed on silica gel

Sources & evidence

ORD record: ord-95465a65c4164dbdb912a878af53938e
Source dataset: uspto-grants-1988_06
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US04752646

Reaction notes

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