| Ferrier rearrangement | |
|---|---|
| Named after | Robert J. Ferrier |
| Reaction type | Rearrangement reaction |
| Identifiers | |
| RSC ontology ID | RXNO:0000229 |
The Ferrier rearrangement is an organic reaction that involves a nucleophilic substitution reaction combined with an allylic shift in a glycal (a 2,3-unsaturated glycoside). It was discovered by the carbohydrate chemist Robert J. Ferrier. [1] [2]
In the first step, a delocalized allyloxocarbenium ion (2) is formed, typically with the aid of a Lewis acid like indium(III) chloride or boron trifluoride. This ion reacts in situ with an alcohol, yielding a mixture of the α (3) and β (4) anomers of the 2-glycoside, with the double bond shifted to position 3,4. [3]
| Lewis acid | Alcohol | Conditions | Results |
|---|---|---|---|
| InCl3 | methanol | in dichloromethane | α:β = 7:1 [4] |
| dioxane | water | heating | 75% yield [5] |
| SnCl4 | methanol | in dichloromethane, –78 °C, 10 min | 83% yield, α:β = 86:14 [6] |
| BF3·O(C2H5)2 | isopropanol | in dichloromethane, RT, 24 hr | 95% yield [7] [8] |
| ZnCl2 | ethanol | in toluene, RT, 30–60 min | 65–95% yield, α:β = 89:11 [9] [10] |
| BF3·O(C2H5)2 | benzyl alcohol | in dichloromethane, –20 °C to RT, 1 hr | 98% yield [11] |
By replacing the alcohol with a silane, C-glycosides can be formed. With triethylsilane (R'=H), the reaction yields a 2,3-unsaturated deoxy sugar. [3]
An analogous reaction with nitrogen as the heteroatom was described in 1984 for the synthesis of the antibiotic substance streptazolin. [12]
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