Functionalized Polymers

The IUPAC definition of functional polymers includes those polymers that possess particular chemical groups or those that have specific chemical, physical, pharmacological, biological, or other uses, based on their distinct chemical or functional groups [ 1 ]. Indeed, functional polymers are macromolecules that are functionalized and incorporate the green benefits of small molecules possessing the same functional groups. The use of polymer-functionalized materials in organic transformations dates back to 1946 [ 2 ], although key contributions were reported somewhat later by Merrifield, Lestinger, Frechet, Sherrington, Hodge, Hunt, and among others [ 3–9 ]. To my knowledge, the first report on the use of functional polymers in the synthesis of organic compounds was made by Merrifield in 1963, when he used the chloromethylated polystyrene as a solid support in multistep synthesis of polypeptides ( Scheme 2.1 ) [ 3 ]. In 1984, Merrifield received the Nobel Prize in chemistry for his groundbreaking achievement. In the Merrifield’s synthesis of peptides, first, the covalent attachment of an N -protected amino acid to the solid support, followed by deprotection of amine group, yields polymer (I) which further reacts with another N -protected amino acid molecule that its carboxylic acid group is activated by N , N’ -dicyclohexylcarbodiimide (DCC). The successive addition of further N -protected amino acids to the resulted polymer (II) and deprotection in an alternating manner produce the desired peptide which is then removed from the support by cleavage of the ester linkage. Finally, the peptide was isolated from the polymer by filtration. In the Merrifield’s method of peptide synthesis, his solid phase technique was used for the preparation of oligodeoxyribonucleotides [ 6 ], oligosaccharides [ 7 , 10 ], oligonucleotide [ 11 ], poly(amidoamines) [ 12 ], and natural peptides or their analogues [ 13 ].