Palladium catalyzed rearrangement

Scheme 4.38 Synthesis of allenylsulfones by palladium-catalyzed rearrangement.

Palladium-catalyzed rearrangement of 2-allyloxypyrimidines gives A -allyl-2(l//)-pyrimidinones <1996CHEC-II(6)93>, but otherwise this approach has been little utilized. 

In a related rhodium- or palladium-catalyzed rearrangement of 7-oxaquadricyclane 1, which follows a different mechanism, a third type of regioisomer 2 was formed,52,64 which was different from the product of thermal rearrangement 3.49 51... 

A major practical disadvantage of the palladium-catalyzed rearrangement is the need to disgorge the PdCl2 residue from the product diene by treating it with KCN. Fortunately, as the reaction shown in equation (30) demonstrates, more crowded substrates do not give products containing palladium. The selectivity of this reaction is an improvement over the... 

In the synthesis of racemic 3-phosphoshikimic acid derivatives a palladium-catalyzed rearrangement of a cyclohexenyl phosphate was used for the stereochemical control of the C-3 oxygen function29. This rearrangement is considerably slower than the analogous reactions of allylic acetates and requires a stoichiometric amount of bis(acetonitrile)palladium(II) chloride. 

Low 1,2-diastereoselection is also found in the thermal rearrangement of trichloroacetimidates derived from chiral <5-amino allylic alcohols54 55, which is contrary to the results of the palladium-catalyzed rearrangement (see Section 7.6.1.2.). 

Palladium-catalyzed rearrangements of dienylcyclopropanes have also been reported. Vinylcyclopropane (64) gave cyclopentene (65) without regard to the ( /(Z) composition of the diene (equation 27). Similar results with respect to (E) and (Z) mixtures were also observed in the more-substituted case of (66) with moderate stereoselectivities (3 1) observed upon reclosure (equation 28). It has been suggested that the palladium-catalyzed rearrangement is in fact a nucleophilic-like opening followed by reclosure. Such transformations are discussed in Section 8.1.3.4 in the context of the stepwise opening of activated vinylcyclopropanes with iodide and other nucleophiles. 

Hydroxyketones are versatile intermediates in the synthesis of pharmaceutical intermediates and heterocyclic molecules. a-Aryl hydroxyketones have been prepared by reaction of aryl aldehydes with 1,4-dioxane followed by reduction with lithium aluminum hydride (LAH) and by the selective LAH reduction of a-silyloxy a,P-unsaturated esters." WissneC has shown that treatment of acid chlorides with tris(trimethylsilyloxy)ethylene affords alkyl and aryl hydroxymethyl ketones. 1-Hydroxy-3-phenyl-2-propanone (3) has been generated by the osmium-catalyzed oxidation of phenylpropene and by the palladium-catalyzed rearrangement of phenyl epoxy alcohoP both in 62% yield. 

Trost and Runge announced in 1981 the use of simple allyl carbonates and described even earlier the Pd(0)-catalyzed rearrangement of allyl ethers of enolic /3-ketoesters into the isomeric a-allyl-/S-ketoesters (Scheme 5). Allyl ethers of enolic /3-ketoesters are vinylogous of allyl carbonates In 1980 Tsuji and co-workers described a similar rearrangement,declaring that the palladium-catalyzed rearrangement of a similar cyclic ether has been presented in a lecture by B.M. Trost at the 1st Intern. Kyoto Conf. Org. Chem., Dec., 6,1979. ... 

K.2.2 PALLADIUM-CATALYZED REARRANGEMENTS OF OXYGEN FUNCTIONS 2953 5% PdClj... 

DeKorver, K. A., Hsung, R. R, Song, W. Z., Wang, X. N., Walton, M. C. (2012). An intramolecular 2-1-2 cycloaddition of ketenimines yia palladium-catalyzed rearrangements of N-allyl-ynamides. Organic Letters, 14, 3214-3217. 

Shimizu I, Yamada T, Tsuji J. Palladium-catalyzed rearrangement of allylic esters of acetoacetic acid to give y, 8-unsaturated methyl ketones. Tetrahedron Lett. 1980 21 3199-3202. 

Trost BM, Tanoury GJ. An unusual mechanism of a palladium-catalyzed intramolecular carbametalation. A novel palladium-catalyzed rearrangement. J. Am. Chem. Soc. 1988 110 1636-1638. 

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