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.     

Pd(II)-catalyzed aliphatic Claisen rearrangements of acyclic allyl vinyl ethers

Palladium (II)-catalyzed [3,3] sigmatropic rearrangement of acyclic allyl vinyl ethers delivers 2,3-anti disubstituted pentenal Claisen adducts with high diastereoselectivity. Reaction conditions for circumventing allyl vinyl ether cleavage that had previously plagued catalyzed rearrangement of α-unsubstituted vinyl ether substrates are described. Merging Pd(II) catalysis with the facile access to the Claisen substrates afforded by Ir(I)-catalyzed olefin isomerization provides an expedient procedure for realizing asymmetric anti-selective Claisen rearrangements.     

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.     

Synthesis of cyclic allyl vinyl ethers using Pt(II)-catalyzed isomerization of oxo-alkynes

Several alkynyl epoxides and one alkynyl allyl alcohol were isomerized to cyclic allyl vinyl ethers (3,4-dihydro-2H-1,4-oxazines) using PtCl₂ as the catalyst. Three of these allyl vinyl ethers were converted to 2-hydroxymorpholine derivatives by hydrolysis and two were converted to piperidine derivatives by thermal Claisen rearrangement.     

Enantioselective Claisen rearrangements with a hydrogen-bond donor catalyst

N,N'-Diphenylguanidinium ion associated with the noncoordinating BArF counterion is shown to be an effective catalyst for the [3,3]-sigmatropic rearrangement of a variety of substituted allyl vinyl ethers. Highly enantioselective catalytic Claisen rearrangements of ester-substituted allyl vinyl ethers are then documented using a new C2-symmetric guanidinium ion derivative.     

Carbanion-accelerated Claisen rearrangements 3. Vicinal quaternary centers

The preparation and Claisen rearrangement of highly substituted allyl vinyl ethers is described. It is demonstrated that the thermal and anionic versions of the Claisen rearrangement are capable of creating vicinal quaternary centers.     

Highly enantioselective catalytic asymmetric Claisen rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ethers

Progress in the catalytic asymmetric Claisen rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ether is reported. Application of a more Lewis acidic catalyst, [Cu{(S,S)-t-Bu-box}](H₂O)₂(SbF₆)₂, afforded β-chiral α-keto ester with an enantiomeric excess up to 99%. We suggest a highly polarized transition state for the Lewis acid-catalyzed Claisen rearrangement in order to explain the experimental results.     

Conversions of Allyl Ethers in a Superbasic Medium

Conversions of alkyl allyl and terpenoid allyl ethers in a superbasic medium (dimethyl sulfoxidepotassium hydroxide) are studied. The ethers with an unbranched alkyl substituent isomerize into propenyl ethers, the ethers with a branched unsaturated substituent decompose to give a hydrocarbon, and diallyl ethers isomerize into allyl vinyl ethers whose Claisen rearrangement gives rise to aldehydes.     

Tandem isomerization/Claisen transformation of allyl homoallyl and diallyl ethers into gamma,delta-unsaturated aldehydes with a new three component catalyst Ru3(CO)12/imidazolinium salt/Cs2CO3

The three component catalyst Ru3(CO)12/1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride/Cs2CO3 (molar ratio 1:3:6) successively promotes both allyl to vinyl isomerization and Claisen rearrangement from allyl homoallyl and diallyl ethers to selectively afford gamma,delta-unsaturated aldehydes.     

Rearrangement of allyl homoallyl ethers to gamma,delta-unsaturated carbonyl compounds catalyzed by iridium complexes

Iridium complexes were found to promote the conversion of allyl homoallyl ethers to gamma,delta-unsaturated carbonyl compounds. For example, treatment of 1-allyl-1-allyloxycyclohexane in the presence of catalytic amounts of [Ir(cod)Cl](2), PCy(3), and Cs(2)CO(3) in toluene at 100 degrees C afforded 4-cyclohexyliden-2, 3-dimethylbutanal in 74% yield. The reaction presumably proceeds through double bond migration to allyl vinyl ethers, which then undergo the Claisen rearrangement.     

Magnesium(II)-coordinated Claisen rearrangement: a direct approach towards ulosonic acid derivatives

Unprecedented magnesium dihalide-catalysed Claisen rearrangement of 2-alkoxycarbonyl allyl vinyl ethers derived from α-chloroglycidic esters is reported in the glucidic series. A first application of this reaction concerns the stereoselective construction of a disaccharide analogue including a galactosyl and an ulosonic isopropyl ester moieties.     

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.     

One-Pot synthesis of gamma,delta-unsaturated carbonyl compounds from allyl alcohols and vinyl or isopropenyl acetates catalyzed by [IrCl(cod)]2

One-pot synthesis of gamma,delta-unsaturated carbonyl compounds from allyl alcohols and vinyl or isopropenyl acetates was achieved through in situ generation of allyl vinyl ethers by the action of the [IrCl(cod)]2 complex followed by Claisen rearrangement of the resulting ethers. For instance, the reaction of trans-2-methyl-3-phenyl-2-propen-1-ol with isopropenyl acetate in the presence of [IrCl(cod)]2 (1 mol %) and Cs2CO3 (5 mol %) at 100 degrees C for 3 h followed by 140 degrees C for 15 h afforded 5-methyl-4-phenyl-5-hexen-2-one in 72% yield. When vinyl acetate was employed in place of isopropenyl acetate, 4-methyl-3-phenyl-4-pentenal was obtained in 83% yield.     

Formal synthesis of erythrodiene and spirojatamol via rhodium-catalysed Claisen rearrangement/hydroacylation

A novel procedure allows the synthesis of spiro[4.5]decane-1,6-dione 1, a key intermediate in the total synthesis of erythrodiene and spirojatamol. The key step is a combination of Claisen rearrangement of allyl vinyl ethers followed by an intramolecular hydroacylation catalysed by RhCl(cod)(dppe).     

Note Synthesis and Characterization of Poly-(2-Methallyl-p-cresol)

In spite of the low reactivity of allyl monomers, attempts have been made to prepare polymers by polyrecombination of allyl aromatic compounds. We were encouraged by the stability of allyl radicals [1-8]. The literature on the Claisen rearrangement of polyfunctional allyl aryl ethers contains some observations of the formation of tarry masses and resinification of polyfunctional aryl ethers. Details of the polymerization and the possible structures were not studied. We felt it interesting to synthesize this new monomer, 2-methyallyl-p-cresol, by the rearrangement, and to study in detail the polymerization and characterization of the polymer.     

Strategies for expanding structural diversity available from olefin isomerization-claisen rearrangement reactions

Boron-substituted di(allyl) ethers provide an efficient conduit for expanding the structural diversity available from olefin isomerization-Claisen rearrangement (ICR) reactions. Easily prepared allyl propargyl ethers undergo chemoselective Zr(IV)-catalyzed hydroboration to afford the boron-substituted ICR substrates. The boron-substituted allyl residue undergoes chemoselective Ir(I)-catalyzed olefin isomerization and in situ Claisen rearrangement to afford stereodefined beta-boryl aldehyde products. Functionalization of the C-B linkage by oxidation or Suzuki cross-coupling provides a route to Claisen adducts previously inaccessible from the ICR methodology.     

Transition-metal-mediated cascade reactions: the water-accelerated carboalumination-Claisen rearrangement-carbonyl addition reaction

[Chemical reaction: See text] A three-step cascade reaction involving a water-accelerated catalytic carboalumination, a Claisen rearrangement, and a nucleophilic carbonyl addition converts terminal alkynes and allyl vinyl ethers into allylic alcohols containing up to three contiguous asymmetric carbon centers. Stoichiometric quantities of water as an additive increase the rate of the [3,3] sigmatropic rearrangement as well as the diastereoselectivity of the carbonyl addition process. Reaction products contain 1,6-diene functionalities that are readily cyclized to substituted cyclopentenes. An extension of this methodology to a sequence involving a [1,3] sigmatropic shift was feasible with a cyclopropylmethyl vinyl ether substrate.     

Regioselectivity in aromatic Claisen rearrangements

Theoretical calculations and the isomeric product composition for a series of eight meta-substituted allyl aryl ethers confirm the reliability of a new (1)H NMR methodology used to predict aromatic Claisen regioselectivity from ground-state conformational preference of the reactant allyloxy group. Frontier HOMO-LUMO intramolecular orbital interactions, a classical approach in predicting reactivity and selectivity for Claisen rearrangements of allyl vinyl ethers, is shown to fail to mimic transition-state orbital interactions for aromatic Claisen rearrangements of meta-substituted allyl aryl ethers. B3LYP/6-31G(d,p) calculations on reactants and transition states are shown, however, to correctly predict the outcome of such aromatic Claisen rearrangements from either the preferential reactant ground-state conformation (theoretical predictions that agree with the NMR measurements) or the less energetic transition state, or both.     

Palladium(Ti)-Catalyzed Claisen Rearrangement of 1-Phenylethenyl 2-Propenyl Ethers

Allyl vinyl ethers containing phenyl group at a position of vinyl ether readily undergo the Claisen rearrangement in the presence of a palladium(II) catalyst to give phenyl homoallyl ketones in good yields.     

Stereocontrolled Synthesis of Vinyl Boronates and Vinyl Silanes via Atom‐Economical Ruthenium‐Catalyzed Alkene–Alkyne Coupling

The synthesis of vinyl boronates and vinyl silanes was achieved by employing a Ru‐catalyzed alkene–alkyne coupling reaction of allyl boronates or allyl silanes with various alkynes. The double bond geometry in the generated vinyl boronates can be remotely controlled by the juxtaposing boron‐ and silicon groups on the alkyne substrate. The synthetic utility of the coupling products has been demonstrated in a variety of synthetic transformations, including iterative cross‐coupling reactions, and a Chan‐Lam‐type allyloxylation followed by a Claisen rearrangement. A sequential one‐pot alkene‐alkyne‐coupling/allylation‐sequence with an aldehyde to deliver a highly complex α‐silyl‐β‐hydroxy olefin with a handle for further functionalization was also realized.