Nuclear oxidation in flavones and related compounds - Part XXVI. Phytochemical methods of nuclear oxidation
It is suggested that phytochemical nuclear oxidation involves several processes. (1) A single stage direct process which is satisfactory for the para oxidation of flavones and related compounds, the model being Elbs persulphate oxidation method, has already been discussed in detail in Part XIII. (2) A multistage process, an aldehyde being an intermediate stage which subsequently undergoes oxidation (Dakin’s reaction), is illustrated by the recent synthesis of the flavonols, myricetin, robinetin and kanugin and essential oil components, elemicin and myristicin. Support for the existence of the stages can be obtained from a study of lichen acids. The mechanism of this process is discussed; it is quite suitable for ortho oxidations in flavones and related compounds, but the yields are rather poor in para-oxidations. Another multistage process involving ethylenic activity has been shown by Cook and others to be applicable to polycyclic hydrocarbons.