Unprecedented selective heterogeneously catalysed “green” oxidation of betulin to biologically active compounds using synthetic air and supported Ru catalysts

Selective oxidation of betulin to biologically active betulinic aldehyde is demonstrated for the first time over Ru/C catalyst mixed with a basic hydrotalcite and using SiO2 as a dehydrating agent in synthetic air at 108 °C in toluene with conversion of 41% in 24 h and 67% selectivity to betulinic aldehyde, whereas without SiO2 with Ru/C the corresponding conversion and selectivity values were 20% and 66%, respectively. Over another, acidic Ru/C catalyst even higher conversion was achieved, giving, however, allobetulin as a main product. These results indicate that basicity and absence of water are crucial for selective botulin oxidation over Ru catalysts. The conversion levels are comparative with the results in the oxidation of hydroxymathylfurfural, which contains a hydroxymethyl group attached to the heterocyclic ring.