ARYL MIGRATIONS DURING PULPING

Aryl migrations taking place during pulping processes are described. Migrations from C(alpha) to C(beta) are given by "condensed" beta-O-4 units and result in fragmentation and the formation of potential chromophoric systems of the stilbene type. Migrations from C(beta) to C(alpha), on the other hand, are observed with stilbenoid units and their precursors (beta-1 and beta-5 units) and afford 1,1-diaryl-2-oxo structures. Both types of aryl migration proceed via 3-membered spiro-cyclohexadienone intermediates. The direction of the aryl migrations may affect the ease and extent of lignin fragmentation and the formation of potential chromophoric groups during pulping processes.