Реакция #56547

Уравнение реакции

retinal

hydrochloric acid

→

beta-carotene

Выход 85.0%

Растворители

tetrahydrofuran

Условия реакции

Обработка

1. 1
   ЭкстракцияThe solution was extracted several times with ether
2. 2
   Промывкаwashed with saturated aqueous sodium chloride solution
3. 3
   Сушкаdried over magnesium sulfate
4. 4
   Концентрированиеconcentrated by solvent removal at the rotary evaporator
5. 5
   ДругоеThe residue was purified by chromatography on silica gel
6. 6
   ПромывкаElution with hexane

Методика

A slurry of titanium trichloride (1.54 gm, 10.0 mmol) in 30 ml dry tetrahydrofuran was prepared under an inert atmosphere (nitrogen or argon), and powdered lithium aluminum hydride (190 mg. 5.0 mmol) was cautiously added. The resulting solution was stirred for two hours at room temperature to form the Ti(II) reagent, and a solution of retinal (1.42 gm, 5.0 mmol) in 5 ml dry tetrahydrofuran was added. The solution was stirred a further fifteen hours at room temperature, and then poured into 50 ml 2 N aqueous hydrochloric acid. The solution was extracted several times with ether, and 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 purified by chromatography on silica gel. Elution with hexane gave 1.14 gm (85% yield) beta-carotene which was identified by thin-layer chromatographic comparison with an authentic sample, by its characteristic ultraviolet spectrum, and by its melting point: mp 180°-182°.

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