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 1382511Notes

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-b0677df9d48a4889bcc348afbf2da097
Source dataset: uspto-grants-1989_02
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US04806661

Reaction notes

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