Реакция #56550

Уравнение реакции

retinal

hydrochloric acid

→

beta-carotene

Выход 65.0%

Растворители

tetrahydrofuran

Условия реакции

Обработка

1. 1
   ТемператураAfter refluxing for a further two hours
2. 2
   Экстракцияextracted with ether
3. 3
   Промывкаwashed with saturated aqueous sodium chloride solution
4. 4
   Сушкаdried over magnesium sulfate
5. 5
   Концентрированиеconcentrated by solvent removal at the rotary evaporator
6. 6
   ПромывкаElution with hexane

Методика

Zinc dust (654 mg, 10.0 mmol) was slurred in 20 ml dry tetrahydrofuran under an inert atmosphere (nitrogen or argon), and a solution of titanium tetrachloride (0.55 ml, 5.0 mmol) in 3 ml dry benzene was rapidly added. The resulting solution was refluxed overnight to form active Ti(II) reagent, and a solution of retinal (710 mg, 2.5 mmol) in 5 ml dry tetrahydrofuran was added. After refluxing for a further two hours, the solution was cooled to room temperature, poured into 50 ml 2 N aqueous hydrochloric acid, and extracted with ether. The ether extracts were combined, washed with saturated aqueous sodium chloride solution, dried over magnesium sulfate, and concentrated by solvent removal at the rotary evaporator. The residue was purfied by chromatography on a silica gel column. Elution with hexane gave 430 mg (65% yield) of beta-carotene which crystallized in the flask. The beta-carotene was identified by tlc comparison with an authentic sample, and by melting point comparison of a recrystallized sample; mp 180°-182°.

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