Tetramethylammonium hydroxide (TMAH) thermochemolysis of lignin: Formation of (E)-5-formyl-2,3,3′,4′-tetramethoxystilbene and its origins

This paper addresses the identification of (E)-5-formyl-2,3,3′,4′-tetramethoxystilbene (11), a major tetramethylammonium hydroxide (TMAH) thermochemolysis product of guaiacyl dehydrogenation polymer (DHP). It was carried out by comparing the mass spectral data and chromatographic behavior with those of authentic (E)-11, which was prepared by off-line preparative TMAH thermochemolysis of 3-[2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[b]furan-5-yl]prop-2-enal (14). As the origins of 11, internal β-5 subunits III connected with other subunits by β-O-4 linkages at both sides via the phenolic and β-alcoholic hydroxyl groups, and phenolic β-5 subunits IV connected with other subunits by β-O-4 linkages at one side via the β-alcoholic hydroxyl group were proposed.