Influence of electron donating aromatic substituents on the ruthenium tetroxide-catalysed oxidation of (±)-podocarpa-8,11,13-trienes

Abstract

Whereas the (±)-podocarpa-8,11,13-trienes 3b-e, incorporating a phenolic hydroxyl or methyl ether functionality at C-11 and C-14, and C-14 respectively, on oxidation with sodium metaperiodate - catalysed by ruthenium tetroxide give (±)-winterin, through chemoselective degradation of the aromatic ring, the unsubstituted 3a, isomeric methyl ethers 3f-i, and cis-podocarpa-8,11,13-triene undergo only benzylic oxidation resulting in the respective ketones 8d, 8a-c, 8e and the diketone 9. Similar oxidation reaction of the hexahydrophenanthrene 7a led to the α, β-unsaturated tricyclic ketone 11a and the tetrahydronaphthalene dicarboxylic anhydride 12. In contrast, 7b produced the diketone 10b and the α ,β-unsaturated ketone 11b as the sole isolated products.