Study of Claisen rearrangement catalyzed by Bismuth(III) salts

Among the Lewis acids studied, the hydrated bismuth(III) triflate was widely used because it proved to be more efficient than the other Lewis acids. Its catalytic potential was noted in the Claisen rearrangement of aryl allyl ethers, acetates of Baylis-Hilman adducts, substituted 2-alkoxycarbonyl allyl vinyl ethers and in the [1,3] rearrangement of aryl prenyl ethers. It was also effective in the double Claisen rearrangement of aryl allyl ethers. Hydrated bismuth(III) triflate has been shown to be an effective catalyst for [3,3] and [1,3] rearrangements of aryl allyl ethers. Depending on the selected conditions, hydrated bismuth(III) triflate can selectively catalyze [3,3] or [1,3] rearrangements. Moreover, our conditions have been successfully applied in the rearrangement of acetates of Baylis-Hilman adducts. The results obtained showed that this type of rearrangement is stereoselective. For substituted 2-alkoxycarbonyl allyl vinyl ethers, reactivity and stereoselectivity depend on the structure of the starting material.