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Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of α,β-Unsaturated Compounds and Alkynes
Published on: December 16, 2019
α-Substituent Effect on o-Vinylbenzaldehyde Cyclopolymerization
Bora Inci1, Pin-Nan Cheng1, Kyle Beljanski1
1Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States.
Abstract:
The cationic cyclopolymerization of o-vinylbenzaldehydes initiated by boron trifluoride is described. Unlike the incomplete conversion of o-vinylbenzaldehyde (1) at 0 °C, α-methyl-substituted monomers (2) and (3) undergo cyclopolymerizations with complete conversions at -78 °C. On the other hand, α-phenyl-substituted monomer (4) generated indenyl alcohol (7) when subjected to cationic polymerization conditions. The proposed mechanism for o-(α-methyl)vinylbenzaldehyde polymerization explains the importance of reaction temperature for polymer formation. Resulting amorphous poly(o-(α-methyl)vinylbenzaldehyde (10) exhibited good thermal stability (Tonset = 340 °C) with a Tg of 153 °C. Polymer (10) is a brittle and glassy plastic with a storage modulus (E') of 3 × 108 Pa and elongation at break of ∼3%.
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