New Chemical Modification of Polymers with Pendant Chloromethyl Groups Using 1,8-Diazabicyclo-[5.4.0]-7-undecene

Abstract

The esterification reaction of poly[(p-chloromethyl)styrene] (PCMS) with benzoic acid and acetic acid proceeded very smoothly to give the corresponding polymers with pendant ester residues using 1,8-diazabicyclo-[5.4.0]-7-undecene (DBU) as an organic base even at 30°C in aprotic polar solvents such as N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone, and dimethyl suloxide (DMSO). The reaction of poly(2-chloroethyl vinyl ether) (PCEVE) and poly(epichlorohydrin) (PECH) with benzoic acid in the presence of DBU in DMF also gave corresponding polymers with pendant benzoate moieties. However, the reactivities of PCEVE and PECH were lower than that of PCMS. Furthermore, the reaction of PCMS with N-protected amino acids such as Boc-L-alanine, Cbz-L-alanine, and Bz-DL-alanine afford corresponding polymers with pendant amino acid residues in high conversions using DBU in DMSO. From these results, it was concluded that DBU is the extremely useful organic base for the esterfication reaction of the pendant chloromethyl groups in the polymers with carboxylic acids under mild reaction conditions.