Reactions of lignin model beta-aryl ethers with acetyl bromide

The reactivities of several softwood lignin model compounds with acetyl bromide have been examined in a number of good lignin solvents. Primary (gamma-)alcohols acetylate more rapidly than phenolic hydroxyls, whereas benzylic (alpha-)hydroxyls are converted to bromides via their acetates. Models treated under mild conditions with acetyl bromide cleanly produced acetylated alpha-bromo derivatives. Benzyl aryl ethers are cleaved rapidly and quantitatively to yield aryl acetates and acetylated alpha-bromo products. The rate order for the observed reactions is: primary (gamma-)OH acetylation > benzyl aryl ether cleavage/bromination > benzylic secondary (alpha-)OH acetylation > benzylic acetate to benzylic bromide interconversion much greater than phenolic OH acetylation. These reactions are synthetically useful and have further potential in analytical methodologies.