Stereochemistry palladation

Alkenes can be palladated to yield a complex which can be opened trans by an amine nucleophile. The resulting o-pidladium species can be woiked up oxidatively to yield an amino alcohol (as its acetate ester). This depalladation occurs with inversion, yielding overall cis stereochemistry (Scheme 54). If the acetic acid in step iii is replaced with phenol, a -phenoxyamine is produced. 

Tri-O-benzyl-D-arabinofuranose stirred at 0° with a mixture of ethanethiol and anhydrous Mg-sulfate satd. with HGl, and the product treated with benzoyl chloride in pyridine 4-0-benzoyl-2,3,5-tri-0-benzyl-D-arabinose diethyl di-thioacetal (Y 94%) added with Drierite to henzyl alcohol, stirred 1 hr. after addition of Cd-carbonate and HgClg the product isolated after 2 hrs. -> 4-0-benzoyl-2,3,5-tri-0-henzyl-D-arabinose dibenzyl acetal (Y 80%) stirred 16 hrs. under reflux at 56-58° with BaO, Drierite, methyl iodide, and dimethylformamide, the resulting crude 2,3,5-tri-0-henzyl-4-0-methyl-D-arabinose dibenzyl acetal hydrogenated ca. 2.5 hrs. with palladous chloride in methanol, and the product refluxed 1.5 hrs. in 0.5 N HGl to hydrolyze the methyl glycoside present 4-0-methyl-y -D-arabinopyranose (Y 64%). — This pathway is not dependent on the stereochemistry of the aldose. H. G. Fletcher, Jr., and H. W. Diehl, J. Org. Ghem. 30, 2321 (1965). 

Another study used a novel approach involving a nonchelating diolefin, which forms a stable 77-allyl complex upon hydroxypalladation. As shown in Scheme 9 the stereochemistry of the consistent complex was only with anti addition. Some of the objections applied to previous studies apply here. The solvent is not pure water and the system is chloride starved. However, an even more important objection applies in this example. Thus, as will be discussed in Sect. C, cyclohexene-type structures undergo anti hydroxy-palladation even under the usual Wacker conditions. Thus, the cyclohexadiene is not a valid model for the acyclic olefins of interest. 

Stifle JK, James DE, Hines LR Stereochemistry of methoxy-palladation of 2-butenes. J. Am. Chem. Soc. 1973 95 5062-5064. 

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