Aliphatic Allyl Vinyl Ethers Research Articles

Aromatic Claisen Rearrangements of Benzyl Ketene Acetals: Conversion of Benzylic Alcohols to (ortho‐Tolyl)acetates

Claisen rearrangements of benzyl vinyl ethers are much less facile than those of aliphatic allyl vinyl ethers, and their synthetic utility has remained relatively unexplored. A one‐pot procedure is reported for the generation and Claisen rearrangement of benzyl vinyl ethers that contain an activating α‐alkoxy substituent on the vinyl group. A [3,3]‐sigmatropic mechanism was supported by trapping of the intermediate isotoluene in an intramolecular Alder–ene reaction.

Claisen Rearrangement of Aliphatic Allyl Vinyl Ethers from 1912 to 2012: 100 Years of Electrophilic Catalysis

This review summarizes, from a personal perspective, the development of catalytic asymmetric Claisen rearrangements from 1912 to 2012. 1 Introduction 2 Gosteli–Claisen Rearrangement 3 Claisen Rearrangement Using Stable Enols: Kojic Acid and Diosphenols 4 The Early Years: Catalysis by Bronsted Acids 5 Lewis Acid Mediated Claisen Rearrangements: The Aluminum Age 6 Catalysis by Precious Metals 7 Catalysis by σ-Lewis Acids 8 Catalysis by Achiral Organocatalysts 9 Catalytic Asymmetric Claisen Rearrangements 10 Conclusion

Claisen Rearrangement of Aliphatic Allyl Vinyl Ethers in the Presence of Copper(II) Bisoxazoline

The Claisen rearrangement of 1-methyl-2-isopropyoxycarbonyl-6-propyl allyl vinyl ether catalyzed by copper(II) bisoxazoline (Cu-box) has been investigated using density functional theory. Both the phenyl- and tert-butyl-substituted Cu-box systems have been studied. Three different reaction media (vacuum, CH2Cl2, CH3CN) have been considered. In vacuum, the phenyl Cu-box catalyzed reaction yields a (1R,6R) configured major product with a low selectivity. The solvent induces a higher selectivity and a reversal of the absolute configuration (1S,6S). However, the tert-butyl Cu-box catalyzed reaction yields (1R,6R) as the major product both in the gas phase and in the solvent with a good selectivity. Although chair-like TSs are lower in energy than boat-like TSs, the energy difference is small. This is because in the presence of the catalyst the distance between the allyl and vinyl parts of the substrate is relatively large, and thus the steric repulsion between them is smaller than would normally be expected for boat-like structures. The enantioselectivity of tert-butyl Cu-box originates from the steric interactions between the substrate and the catalyst, which are less important for the phenyl Cu-box where the enantioselectivity is determined by the solvent effects.

Highly Regioselective [3,3] Rearrangement of Aliphatic Allyl Vinyl Ethers Catalyzed by a Metalloporphyrin Complex, Cr(TPP)Cl.

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Highly regioselective [3,3] rearrangement of aliphatic allyl vinyl ethers catalyzed by a metalloporphyrin complex, Cr(TPP)Cl

The Claisen rearrangement of simple aliphatic allyl vinyl ethers catalyzed by a metalloporphyrin, Cr(TPP)Cl, is described. The porphyrin-based Lewis acid catalyst can effectively accelerate the rearrangement via a concerted [3,3] pathway with a minimal degree of bond ionization of the substrates, providing the corresponding Claisen products in moderate to high yields and almost perfect regioselectivity at low catalyst loading.

Metalloporphyrin Cr(TPP)Cl‐Catalyzed Claisen Rearrangement of Simple Aliphatic Allyl Vinyl Ethers and Its Unique Stereoselectivity.

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Metalloporphyrin Cr(TPP)Cl-catalyzed Claisen rearrangement of simple aliphatic allyl vinyl ethers and its unique stereoselectivity

The catalytic Z-selective Claisen rearrangement of simple aliphatic allyl vinyl ethers can be achieved using a chromium(III) porphyrin complex, Cr(TPP)Cl, as a catalyst: Cr(TPP)Cl significantly enhances reversal of E– Z selectivity in the thermal Claisen rearrangement of allyl vinyl ethers, especially, 4,5- and 4,6-disubstituted derivatives, at low catalyst loading.

Catalyzed Olefin Isomerization Leading to Highly Stereoselective Claisen Rearrangements of Aliphatic Allyl Vinyl Ethers.

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Catalyzed olefin isomerization leading to highly stereoselective Claisen rearrangements of aliphatic allyl vinyl ethers.

Iridium(I)-catalyzed olefin isomerization in bis(allyl) ethers is integrated into a generally applicable strategy for affecting highly stereoselective Claisen rearrangements. Catalyzed alkene isomerization affords allyl vinyl ethers from easily prepared di(allyl) ethers; direct thermolysis of these reaction mixtures leads to highly diastereoselective [3,3] sigmatropic rearrangements affording syn-2,3-dialkyl-4-pentenal derivatives. An easily executed strategy for realizing asymmetric variants of the isomerization-Claisen rearrangement (ICR) reactions is also described.

Catalysis of the Claisen Rearrangement of Aliphatic Allyl Vinyl Ethers

The thermal Claisen rearrangement of allyl vinyl ethers is generally regarded as high-performance method for diastereoselective C−C bond formation. Substrate-induced diastereoselectivity and reagent-induced enantioselectivity with stoichiometric amounts of external chiral auxiliaries have frequently been exploited to control the stereochemical course of the Claisen rearrangement. This review summarizes the attempts to catalyze the Claisen rearrangement of acyclic aliphatic allyl vinyl ethers with chiral and achiral catalysts. The best suited catalysts for the Claisen rearrangement so far identified are Lewis acids. Finally, bis(oxazoline)copper(II) complexes have found a further useful application as chiral catalysts for the first catalytic, enantioselective Claisen rearrangement − 90 years after Ludwig Claisen originally reported a [3,3]-sigmatropic rearrangement of an allyl vinyl ether.