Vinyl ether, formation from free-phenolic

Figure 1. Quinone methide and vinyl ether formation from free-phenolic lignin units.

High-molecular-weight A-substituted maleimides have been prepared and used as polymeric food antioxidants which can achieve the desired gastrointestinal nonabsorption. A-(3,5-Di-t-Bu -hydroxyphenyl)maleimide was prepared in two steps (a) formation of 2,6-di-t-Bu-4-aminophenol either from 2,6-di-(-Bu-phenol by nitration followed by reduction, or from 4-aminophenol by alkylation, (b) amida-tion of maleic anhydride with the 2,6-di-t-Bu-4-aminophenol followed by dehydration. The nonabsorbable poly(A-(3,5-di-t-Bu-4-hydroxyphenyl)maleimide)s were prepared from the monomeric maleimides by free radical homo- and copolymerization with comonomers of alkyl vinyl ethers (Scheme 5.5) [43]. 

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