α-Substituent Effect on -Vinylbenzaldehyde Cyclopolymerization.

The cationic cyclopolymerization of -vinylbenzaldehydes initiated by boron trifluoride is described. Unlike the incomplete conversion of -vinylbenzaldehyde () at 0 °C, α-methyl-substituted monomers () and () undergo cyclopolymerizations with complete conversions at -78 °C. On the other hand, α-phenyl-substituted monomer () generated indenyl alcohol () when subjected to cationic polymerization conditions.