Synthesis of Vitamin A Acetate OH PBr, PhSO,Na sO,Ph Vinyl-B-ionol 1) KO'Bu 2) Br OEt SO,Ph OEt OAc Elimination in base.

Introductory Chemistry For Today
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ISBN:9781285644561
Author:Seager
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Chapter9: Acids, Bases, And Salts
Section: Chapter Questions
Problem 9.15E
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Please check if everything is alright with my synthesis of Vitamin A acetate (see image) as well as the experimental setup. Thank you!

Here is the tentative experimental setup:

Step one:

In a round bottom flask, add Vinyl-b-ionol in carbon tetrachloride solvent. Next, attach the condenser setup with a heating mantle firmly grasping the flask. Pour in the calculated amount of phosphorus tribromide and reflux for 1 hour. Let it cool to room temperature, then add hexane. Filter off the precipitates.

Step two:

Transfer to two-necked round bottom flask and add THF. Next, add sodium benzenesulfinate and stir at 40°C for 6 hours. After, cool to room temperature and remove any precipitates by filtration. Purify the reaction mixture in the acetonitrile-ethylacetate system of recrystallization.

Step three:

Cool the THF solution to 0°C then add potassium tertiary butoxide, dropwise. Stir for 15 minutes then add drops of bromo ester as well. Stir at room temperature for 10 hours. Add water and extract with ethyl acetate. Purification by column chromatography may be done.

Step four:

Add sodium tertiary butoxide at 0°C to the solution and stir once more for 16 hours. Finally, check TLC for completion. If initial reagents are present add more base and heat.

Also, can I get a brief explanation on the chemistry of each step of the synthesis? like why the phosphorus tribromide attacks the vinyl-b-ionol in the first step etc.

Synthesis of Vitamin A Acetate
PBr,
PhSO,Na
SO,Ph
Vinyl-B-ionol
1) КОВи
2)
Br
OEt
SO,Ph
OEt
OAC
Elimination in base,
potassium alkoxides
Transcribed Image Text:Synthesis of Vitamin A Acetate PBr, PhSO,Na SO,Ph Vinyl-B-ionol 1) КОВи 2) Br OEt SO,Ph OEt OAC Elimination in base, potassium alkoxides
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