pubs.acs.org/Macromolecules Published on Web 08/02/2010 r 2010 American Chemical Society 6968 Macromolecules 2010, 43, 6968–6979 DOI: 10.1021/ma101048z Novel, Metal-Free, Superacid-Catalyzed “Click” Reactions of Isatins with Linear, Nonactivated, Multiring Aromatic Hydrocarbons M. Carmen G. Hernandez, Mikhail G. Zolotukhin,* Serguei Fomine, Gerardo Cedillo, and Salvador L. Morales Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, CU,Coyoacan 04510, Mexico D. F., Mexico Nils Fr€ ohlich, Eduard Preis, and Ullrich Scherf Macromolecular Chemistry Group, Wuppertal University, Gauss-Str. 20, D-42097 Wuppertal, Germany Manuel Salm on, Maria Isabel Ch avez, and Jorge C ardenas Instituto de Quı´mica, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, CU, Coyoacan 04510, Mexico D. F., Mexico Alberto Ruiz-Trevino Departamento de Ingenierı´as y de Ingenierı´a y Ciencias Quı´micas, Universidad Iberoamericana, Prol. Paseo de la Reforma No. 880, M exico, D.F. 01219, Mexico Received May 11, 2010; Revised Manuscript Received July 9, 2010 ABSTRACT: A novel series of linear, high-molecular-weight polymers was synthesized by one-pot, metal- free superacid-catalyzed reaction of isatins (1a-d) with linear, nonactivated, multiring aromatic hydro- carbons: biphenyl (A), p-terphenyl (B), p-quaterphenyl (C), 2-(4-biphenylyl)-6-phenylbenzoxazole (D), 9H- fluorene (E), 9,9-dimethyl-9H-fluorene (F), 2,2 0 -[2,5-bis(trifluoromethyl)-1,4-phenylene]bis(9,9-dimethyl- 9H-fluorene) (G), oligo-9,9-bis(2,6-ethylhexyl)-9H-fluorene (H), biphenol (I), and bi-2-napththol (J). The reactions were performed at room temperature in the Brønsted superacid trifluoromethanesulfonic acid (CF 3 SO 3 H, TFSA) and in a mixture of TFSA with methylene chloride or TFA tolerant of hydroxyl, carboxy, and cyano groups. The polymers obtained were soluble in most common organic solvents, and flexible transparent films could be cast from the solutions. 1 H and 13 C NMR analyses of the polymers synthesized revealed their linear structure with para-substitution in the phenylene fragments of the main chain. The molecular weights M w and M n of the polymers ranged from 54200 to 742000 and from 40140 to 438500 g/mol, respectively. Most of the polymers also possess narrow polydispersity (1.15-1.50). The oxindole groups of the polymers react smoothly with alkyl bromides under basic conditions in N-methylpyrrolidinone (NMP). The amount of “click”able allyl- and propargyl- functionalities is readily controlled by adjusting the reaction ratio of polymer to alkyl bromides. The demonstrated efficiency and orthogonality of isatin-based polymer chemistry shows it to be an essential addition to the family of polymer “click” reactions. 1. Introduction Discovery of new polymer-forming reactions comprises one of the most fascinating topics of polymer chemistry. In principle, there are two basic directions in this area. The first one involves new reactions of functional groups. The second direction involves an increase of synthetic potential of known chemical reactions by means of new catalysts, uncommon monomers, etc. It should be noted that synthetic methodologies used in organic chemistry are not always applicable to polymer chemistry. Only regioselective and highly efficient reactions give rise to high-molecular-weight polymers. (Highly pure monomers are absolutely necessary in order to obtain the desired macromolecules.) This is why deve- lopment of new polymer-forming reactions presents a promising but challenging area. One recent example is Cu(I) catalysis of the Huisgen 1,3- dipolar cycloaddition reaction of organic azides and alkynes (also termed CuAAc) introduced by Meldal and Sharpless. 1,2 Because of high efficiency, regio-specificity and excellent tolerance toward functional groups, this reaction (and this type of chemistry) was defined by Sharpless as “Click” reaction (chemistry). 3 In recent years, “click” chemistry has attracted increasing attention and, since 2004, has been extended to polymer science. 4 (It should be noted that some existing polymer-forming reactions meet the criteria needed for “click” polymer chemistry. 8 ) It is really remarkable how popular CuAAC reactions became for polymer syntheses (including macromolecules of complex topologies) and coupling of polymer fragments into block copo- lymers. It has also been used for grafting and surface modifica- tions. More than 20 reviews and three “click” chemistry themed journal issues have been published (see refs 5-7 and references cited therein). It is also important that the success of click chemistry helped to create new strategies of click-assisted, one-pot, multistep reactions 8 and created a strong drive to develop organic reactions *Corresponding author. E-mail: zolotukhin@iim.unam.mx.