Английская Википедия:Ferrier carbocyclization
Шаблон:Distinguish The Ferrier carbocyclization (or Ferrier II reaction) is an organic reaction that was first reported by the carbohydrate chemist Robert J. Ferrier in 1979.[1][2] It is a metal-mediated rearrangement of enol ether pyrans to cyclohexanones. Typically, this reaction is catalyzed by mercury salts, specifically mercury(II) chloride.
Several reviews have been published.[3][4]
Reaction mechanism
Ferrier proposed the following reaction mechanism:
In this mechanism, the terminal olefin undergoes hydroxymercuration to produce the first intermediate, compound 2, a hemiacetal. Next, methanol is lost and the dicarbonyl compound cyclizes through an attack on the electrophilic aldehyde to form the carbocycle as the product. A downside to this reaction is that the loss of CH3OH at the anomeric position (carbon-1) results in a mixture of α- and β-anomers. The reaction also works for substituted alkenes (e. g. having an -OAc group on the terminal alkene).
Ferrier also reported that the final product, compound 5, could be converted into a conjugated ketone (compound 6) by reaction with acetic anhydride (Ac2O) and pyridine, as shown below.
Modifications
In 1997, Sinaÿ and co-workers reported an alternative route to the synthesis (shown below) that did not involve cleavage of the bond at the anomeric position (the glycosidic bond).[5] In this case, the major product formed had maintained its original configuration at the anomeric position.
Sinaÿ proposed this reaction went through the following transition state:
Sinaÿ also discovered that titanium (IV) derivatives such as [TiCl3(OiPr)] worked in the same reaction as a milder version of the Lewis acid, i-Bu3Al,[6] which goes through a similar transition state involving the retention of configuration at the anomeric center.
In 1988, Adam reported a modification of the reaction that used catalytic amounts of palladium (II) salts, which brought about the same conversion of enol ethers into carbosugars in a more environmentally friendly manner.[7]
Applications
The development of the Ferrier carbocyclization has been useful for the synthesis of numerous natural products that contain the carbocycle group. In 1991, Bender and co-workers reported a synthetic route to pure enantiomers of myo-inositol derivatives using this reaction.[8] It has also been applied to the synthesis of aminocyclitols in work done by Barton and co-workers.[9] Finally, Amano et al. used the Ferrier conditions to synthesise complex conjugated cyclohexanones in 1998.[10]
References
- Английская Википедия
- Страницы с неработающими файловыми ссылками
- Carbohydrate chemistry
- Carbon-carbon bond forming reactions
- Name reactions
- Rearrangement reactions
- Страницы, где используется шаблон "Навигационная таблица/Телепорт"
- Страницы с телепортом
- Википедия
- Статья из Википедии
- Статья из Английской Википедии
