Transformative Masked Ortho-Quinone Chemistry: From Direct Guaiacol Activation to Lignin-Based Adhesives.

Guaiacol moieties (1-hydroxy-2-methoxy-benzenes) are among the most abundant structural motifs in renewable biophenolic feedstocks, representing a potential industrial-scale stream from softwood lignin through biorefinery valorization. Here, the transformative chemistry of masked ortho-quinones (MoQs) is introduced, yielding reactive guaiacol derivatives to enable thiol-guaiacol connectivity (TGC) polymers. Phenyliodine(III)diacetate (PIDA) oxidizes guaiacols to chemically pure MoQs within minutes at room temperature, generating activated triguaiacol monomers that undergo thiol-MoQ Michael-type polyaddition with multithiols. This bulk polymerization leads to TGC-adhesives, reaching professional performance lap-shear strengths up to 16.9 ± 0.9 MPa. The robust strategy is extended to directly activate technical lignin, generating curable multi-MoQ prepolymers which bond aluminum with lap-shear strengths of 9.1 ± 0.7 MPa, positioning MoQs as a sustainable platform chemistry to bridge from lignin to high-performance materials.