Reaction ofp-Hydroxycinnamyl Alcohols with Transition Metal Salts. 1. Oligolignols and Polylignols (DHPs) From Coniferyl Alcohol

Treatment of coniferyl alcohol with iron, cobalt, or manganese salts gave a variety of oligolignols and polylignols (DHPs). Conditions could be adjusted to favor high or low molecular weight products and to give different inter-unit linkage distributions. Oxidation with iron and manganese salts generally gave structures containing β-O-4, β-5, and β-β linkages. Oxidation with iron and manganese salts under highly alkaline conditions also generated α-O-4 structures. The cobalt salt K3Co(CN)6 was unique in that a novel β-γ linkage was generated in high yield. Reactions in the absence of solvent also resulted in the formation of oligolignols and DHPs.