What Is Ireland-Claisen Rearrangement?
The Ireland-Claisen rearrangement is a powerful [3,3]-sigmatropic rearrangement that converts allylic esters into γ,δ-unsaturated carboxylic acids through an in situ generated silyl ketene acetal. It is one of the most useful variants of the Claisen rearrangement because it combines reliable carbon-carbon bond formation with strong stereochemical control, making it especially valuable in the synthesis of complex natural products and chiral building blocks.
In the classical Ireland-Claisen process, an allyl ester is treated with a strong base such as LDA, then trapped with a silylating reagent such as TMSCl or TBDMSCl to give a silyl ketene acetal. Heating then triggers a thermally allowed [3,3]-sigmatropic rearrangement, and after hydrolysis, the product is a γ,δ-unsaturated carboxylic acid. The reaction is especially attractive because the enolate geometry can often be controlled before rearrangement, allowing the stereochemistry of the substrate to be transferred into the product.
A key feature distinguishing the Ireland variant from the classical Claisen rearrangement is that the C-O bond cleavage and C-C bond formation are enabled by the silyl group, which stabilizes the enolate and facilitates the rearrangement under much milder conditions.
- Reagents: Strong base (e.g., LDA, KHMDS), trialkylsilyl chloride (e.g., TMSCl, TBDMSCl), anhydrous solvent (THF, toluene), aqueous acid for workup.
- Reactants: Allylic ester (the substrate bearing an allyl group on the alcohol component).
- Products: γ,δ-Unsaturated carboxylic acid (after hydrolysis of the intermediate silyl ester).
- Reaction Type: [3,3]-Sigmatropic rearrangement (pericyclic reaction) proceeding via a chair-like transition state; specifically, a silyl ketene acetal variant of the Claisen rearrangement.
- Related Reactions: Classical Claisen rearrangement (allyl vinyl ethers), Eschenmoser-Claisen rearrangement (amide acetal), Johnson-Claisen rearrangement (orthoester), Bellus-Claisen rearrangement (allylic ethers + ketenes).
Fig 1. Ireland-Claisen rearrangement reaction and its mechanism. [1]
Mechanism of Ireland-Claisen Rearrangement
Mechanistically, the Ireland-Claisen rearrangement begins with deprotonation of the allylic ester to form an ester enolate. Silylation then produces a silyl ketene acetal, which undergoes a concerted [3,3]-sigmatropic rearrangement through a six-membered cyclic transition state. The immediate rearrangement product is typically a silylated carboxylate derivative, which is then hydrolyzed to the free acid.
Comparison with Related Claisen Variants
The Ireland-Claisen rearrangement is one member of a family of Claisen rearrangement variants that have been developed to address specific synthetic challenges.
| Variant | Substrate | Key Features |
| Classical Claisen | Allyl vinyl ether | High temperatures (>150 °C); no enolate intermediates |
| Ireland-Claisen | Allyl ester | Mild conditions (<100 °C); enolate geometry control; silyl ketene acetal intermediate |
| Eschenmoser-Claisen | Allylic alcohol + N,N-dimethylacetamide dimethyl acetal | Amide acetal intermediate; useful for introducing nitrogen functionality |
| Johnson-Claisen | Allylic alcohol + orthoester | Orthoester intermediate; produces γ,δ-unsaturated esters with a new alkyl group at C2 |
| Bellus-Claisen | Allylic ether + ketene | Ketene intermediate; proceeds at room temperature or below |
Application Examples of Ireland-Claisen Rearrangement
- Example 1: In a recent landmark synthesis, Gao and co-workers reported the construction of the tetracyclic skeleton of polycyclic norcembranoids sinudenoids B-D using a strategically placed Ireland-Claisen rearrangement. The sinudenoids feature a unique [5-5-6-6] tetracyclic framework and exhibit significant biological activity. [2]
- Example 2: Lee, Gladfelder, and Zakarian developed a consecutive Ireland-Claisen/enyne metathesis strategy for the rapid assembly of the substituted cyclohexene core present in several cyclic imine marine toxins, including pinnatoxin A and portimine A. These toxins have attracted significant attention due to their fascinating biological activities. The synthetic approach proceeds stepwise from chiral esters through an Ireland-Claisen rearrangement followed by enyne metathesis. This divergent strategy enables the rapid construction of the challenging substituted cyclohexene-diene motif and can be implemented in syntheses of cyclic imines or derivatives thereof. [3]
Fig 2. Synthetic examples via Ireland-Claisen rearrangement reaction.
Related Products
| CAS No. | Structure | Product | Inquiry |
| 18162-48-6 |  | T-Butyldimethylchlorosilane | Inquiry |
| 72047-94-0 |  | 2-(Trimethylsilylmethyl)allyl acetate | Inquiry |
| 133464-46-7 |  | Fmoc-Glu(OAll)-OH | Inquiry |
| 204251-86-5 |  | N-Alpha-(9-fluorenylmethyloxycarbonyl)-D-glutamic-acid-alpha allyl ester | Inquiry |
| 144120-54-7 |  | Fmoc-Glu-OAll | Inquiry |
| 144120-53-6 |  | Fmoc-Asp-OAll | Inquiry |
| 177609-12-0 |  | Fmoc-D-aspartic acid beta-allyl ester | Inquiry |
| 146982-24-3 |  | Fmoc-Asp(OAll)-OH | Inquiry |
| 2694-54-4 |  | Triallyl trimellitate | Inquiry |
| 29548-30-9 |  | Farnesyl Acetate | Inquiry |
| 2345-26-8 |  | Geranyl isobutyrate | Inquiry |
| 106-29-6 |  | Geranyl butyrate | Inquiry |
| 141-12-8 |  | Neryl acetate | Inquiry |
| 999-21-3 |  | Diallyl maleate | Inquiry |
| 5205-11-8 |  | Benzoic acid 3-methyl-2-butenyl ester | Inquiry |
| 103-54-8 |  | Cinnamyl Acetate | Inquiry |
References
- Jie Jack Li. Name Reactions-A Collection of Detailed Mechanisms and Synthetic Applications, Sixth Edition, 2021, 103-105.
- Gao, Xiaofei, et al. The Journal of Organic Chemistry 90.13 (2025): 4776-4780.
- Lee, Hye Joon, et al. Synlett 35.13 (2024): 1540-1544.
Please kindly note that our products are for research use only.
