Study on Radical Telomerization of Esters of Methacrylic Acid by Using Bromotrichloromethane and Characteristics of the Resulting Telomers III. Aryl Methacrylates

Abstract

Radical telomerization of phenyl (PhMA). 1-naphthyl (1-NMA), and 2-naphthyl (2-NMA) methacrylates was carried out using bromotrichloromethane (BTCM) as a telogen at 50, 70, and 90°C. The telomerization of these aryl methacrylates showed similar product distributions and tacticity as those of methyl methacrylate (MMA), but without formation of lactones. The order of the apparent rate of telomerization was as follows: MMA≅PhMA>1-NMA>>2-NMA. The n[Monomer]:[BTCM] adducts, that is, the n-mers (n=1—3), were separated by silica gel column chromatography. The aryl methacrylate and MMA telomers differed remarkably from each other in reactivity. The elimination reaction of the aromatic telomers with triethylamine was labile and complicated in comparison with that of the MMA telomers, and the dimers were subject to scission of the principal chain besides the normal elimination reaction. The catalytic lactonization of the aromatic dimers with silica gel was slower than that of the MMA dimers. The pyrolysis of the aromatic dimers gave unsaturated compounds in preference to lactones, which were exclusively obtained in the pyrolysis of the MMA dimers. Furthermore, the pyrolysis of the NMA dimers resulted in the diastereoisomerization through depolymerization.