Polymer-based acylating agents

Scheme 16.82. A polymer-supported imide-based acylating agent.

Polymeric amines can be proton acceptors, acyl transfer agents, or ligands for metal ions. The 2- and 4-isomers of poly(vinylpyridine) (11) and (12) and the weakly basic ion exchange resins, p-dimethylaminomethylated PS (2) and poly(2-dimethylaminoethyl acrylate), are commercial. The ion exchange resins are catalysts for aldol condensations, Knoevenagel condensations, Perkin reactions, cyanohydrin formation and redistributions of chlorosilanes. " The poly(vinylpyridine)s have been used in stoichiometric amounts for preparation of esters from acid chlorides and alcohols, and for preparation of trimethylsilyl ethers and trimethylsilylamines from chlorotrimethylsilane and alcohols or amines. Polymer-suppored DBU (l,8-diazabicyclo[5.4.0]undec-7-ene) (52) in stoichiometric amounts promotes dehydrohalogenation of alkyl bromides and esterification of carboxylic acids with alkyl halides. The protonated tertiary amine resins are converted to free base form by treatment with aqueous sodium hydroxide. 

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