Claisen rearrangement catalytic

In these cases of course, the final tautomerization does not take place even when R = H, since there is no aromaticity to restore, and ketones are more stable than enols. Catalytic Claisen rearrangements of allyl vinyl ethers are well known. ... 

Jacobsen and co-workers [79] reported on an elegant asymmetric catalytic Claisen rearrangements (Scheme 6.30). They found that guanidinium ions efficiently... 

The high catalytic activity also enabled aza-Claisen rearrangements to form Al-substituted quaternary stereocenters (Fig. 26) [71]. The catalyst does not need to distinguish between differently sized substituents on the double bond of 49 (e.g., R = CDa, R = CHs, ee = 96%), indicating that coordination of the olefin is the stereoselectivity predetermining step. The imidate-N-atom subsequently attacks intermediate 47-1 from the face remote to the Pd-center totally resulting in a... 

Xin ZQ, Fischer DF, Peters R (2008) Catalytic asymmetric formation of secondary allylic amines by Aza-Claisen rearrangement of trifluoroacetimidates. Synlett 1495-1499... 

The Claisen rearrangement has attracted much attention as an attractive tool for the construction of new carbon-carbon bonds. Various catalytic systems have been developed to afford enantioselective versions of this process. On the other hand, relatively few chiral sulfur-containing ligands have been investigated for this type of reaction. As an example, Taguchi et al. have... 

A thio-Claisen rearrangement174 was used for the regioselective synthesis of thiopyrano[2,3-b]pyran-2-ones and thieno[2,3-b]pyran-2-ones (Eq. 12.76). A convenient method for the aromatic amino-Claisen rearrangement of N-(l,l-disubstituted-allyl)anilines led to the 2-allylanilines being produced cleanly and in high yield by using a catalytic amount of p-toluenesulfonic acid in acetonitrile/water (Eq. 12.77).175... 

Important advances in propargylic etherification have come from the use of copper-based systems that achieve efficient, catalytic O-progargylation of phenols (Scheme 8).245,246 While the mechanism of this transformation remains unclear, the products of these reactions have been readily converted into chromenes through subsequent Claisen rearrangement,... 

The conversion of [49] into [50] involves a Claisen rearrangement. Once this was realized it was less surprising that no specific catalytic groups on the enzyme are involved. Support for the Claisen-type mechanism comes from the inhibition shown by the bicyclic dicarboxylate [51], prepared by Bartlett and Johnson (1985) as an analogue of the presumed transition state [52], This same structure [51], coupled through the hydroxyl group to a small protein, was used as a hapten to induce antibodies, one (out of eight) of which mimics the behaviour of chorismate mutase, albeit less efficiently (Table 7). 

The ruthenium-catalyzed direct addition of saturated aliphatic alcohols to non-activated alkynes remains a challenge. Only ally alcohol has been successfully involved in the intermolecular addition to phenylacetylene to produce an ether and the enal resulting from Claisen rearrangement (Equation 10.7) [24]. Thus, in refluxing toluene, in the presence of a catalytic amount of RuCl(tris(pyrazolyl) borate) (pyridine)2, a 1 1 mixture of ally P-styryl ether and 2-phenylpent-4-enal was obtained in 72% overall yield. 

Bis(oxazoline) ligands have also been employed in the catalytic enantioselective aza-Claisen rearrangement of allylic imidates, " chirality recognition in the determination of the ee of l,l -bi-2-naphthol, " and the enantioselective formation of double and triple helicates. 

There has been a continuing effort to make the Baylis-Hillman reaction a catalytic asymmetric process. Scott Schnauss of Boston University recently reported (J. Am. Chem. Soc. 125 12094, 2003) an elegant solution to this problem, based on the use of Binol-derived Bronsted acids as catalysts. The product hydroxy enones such as 6 are interesting in themselves, and also as substrates for further transformation, for instance by Claisen rearrangement. 

Retro-Claisen rearrangement The formyl bicyclo[2.2.2]octane 1 when heated with a catalytic amount of HO Ac at 110° rearranges to the vinyl ether 2, probably because of relief of the strain associated with the vic-quatemary carbon centers. This retro-Claisen rearrangement occurs rapidly at 0° in the presence of BF3 0(C2H5)2 (0.1 equiv.).10... 

The Carroll rearrangement, a variation on the ester Claisen rearrangement, is a useful method for the preparation of y, 8-unsaturated ketones from allyl acetoacetates, and has been adapted to provide a method for the synthesis of a number of specific arylacetones. Thus, treatment of the p-quinol 1 with diketene and a catalytic amount of DMAP at room temperature gave a 72% yield of the arylacetone 2 together with 5% of the benzofuran 3. 

The decarboxylative Claisen rearrangement of allylic tosylacetate (5) and methyl tosylmalonate derivatives has been extensively studied. In the tosylacetate series, it has been found that acetate ions, base and a silylating agent, preferably N,0-bis(trimethylsilyl)acetamide (BSA), are all necessary, but in only catalytic quantities provided that BSA is used. Potassium acetate has been shown to be a suitable base. 

The Pd(II)-catalysed reaction of an allylic alcohol with the ketene acetal 476 at room temperature generates the ortho ester 477. Its Claisen rearrangement via 478 in boiling xylene with a catalytic amount of PdCl2(PhCN)2 gives the y,S-unsaturated ester 479 [204]. 

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