Heterogeneous hydrogenation of substituted phenols over Al2O3 supported ruthenium

It is shown that catalytic heterogeneous hydrogenation over Ru/Al2O3 of mono- and di-substituted phenols (1–4) works and provides mixtures of the two or four possible isomers. Although cis and all-cis isomers (corresponding to all-syn H2 additions) are less stable, they are always major. It is also observed that large alkyl substituents and carbomethoxy groups have a tendency to increase the diastereoselectivity and that formation of larger amounts of the trans isomers is related to the presence of an OH group thus supporting intermediate formation of the corresponding ketone as already suggested.

Catalytic heterogeneous hydrogenation over Ru/Al2O3 of mono- and di-substituted phenols works and provides mixtures of isomers, the all-cis isomers (corresponding to all-syn H2 additions) being always major.Figure optionsDownload as PowerPoint slide