REACTIONS OF LIGNIN MODEL BETA-ARYL ETHERS WITH ACETYL BROMIDE

The reactivities of several softwood lignin model compounds with acety l bromide have been examined in a number of good lignin solvents. Prim ary (gamma-)alcohols acetylate more rapidly than phenolic hydroxyls, w hereas benzylic (alpha-)hydroxyls are converted to bromides via their acetates. Models treated under mild conditions with acetyl bromide cle anly produced acetylated alpha-bromo derivatives. Benzyl aryl ethers a re cleaved rapidly and quantitatively to yield aryl acetates and acety lated alpha-bromo products. The rate order for the observed reactions is: primary (gamma-)OH acetylation > benzyl aryl ether cleavage/bromin ation > benzylic secondary (alpha-)OH acetylation > benzylic acetate t o benzylic bromide interconversion much greater than phenolic OH acety lation. These reactions are synthetically useful and have further pote ntial in analytical methodologies.