Nucleus Exchange Reaction

A chemical method to degrade lignin in a medium consisting of boron trifluoride and excess phenol was originally developed by Funaoka and Abe (1978a,b, 1980a,b, 1982a,b,c,d,e,f,g). In this method, Cα-aryl carbon-carbon linkages in phenylpropane units are selectively and quantitatively cleaved, following phenolation at the Cα position, releasing phenyl nuclei typified by guaiacol (1) (see Fig. 6.6.1 for structures of compounds) from guaiacyl (softwood) lignins. The guaiacol subsequently is partially demethylated to catechol (2). These transformations are illustrated in Fig. 6.6.2. The key step in this sequence, the release of a phenyl nucleus on reaction with phenol, was termed nucleus exchange (NE) by the original authors.