The DFRC method for lignin analysis. 7. Behavior of cinnamyl end groups

The behavior of cinnamyl end groups of lignins during the derivatization fo llowed by reductive cleavage (DFRC) procedure has been investigated using l ignin model compounds. On AcBr treatment, hydroxycinnamyl alcohols give ris e mainly to 1-aryl-1,3-dibromoprapanes from which 1-aryl-3-bromopropanes an d arylcyclopropanes are formed by zinc reduction. Arylpropene derivatives a re also significant among DFRC products of etherified cinnamyl end-group mo dels. Major monomers from DFRC of hydroxycinnamaldehydes are arylcyclopropy l acetates produced by reductive ring closure of 1-acetoxy-3-aryl-1,3-dibro mopropanes. Although the reactions are not as clean as the ether-cleaving r eactions that form the basis of the DFRC method, end groups produce diagnos tic compounds that provide valuable markers for studying end groups in lign ins.