title: Synthesis and electronic factors in thermal cyclodimerization of functionalized aromatic trifluorovinyl ethers.
abstract: A series of 19 p-substituted aromatic trifluorovinyl ether compounds were prepared from versatile intermediate p-Br-C(6)H(4)-O-CF=CF(2) and underwent thermal radical mediated cyclodimerization to new difunctional compounds containing the 1,2-disubstituted perfluorocyclobutyl (PFCB) linkage. The synthetic scope demonstrates the functional group transformation tolerance of the fluorovinyl ether, and the dimers are useful as monomers for traditional step-growth polymerization methods. (19)F NMR spectra confirmed that p-substitution affects the trifluorovinyl ether group chemical shifts. The first kinetic studies and substituent effects on thermal cyclodimerization were performed, and the results indicated that electron-withdrawing groups slow the rate of cyclodimerization. The data were further analyzed using the Hammett equation, and reaction constants (rho) of -0.46 at 120 degrees C and -0.59 at 130 degrees C were calculated. This study presents the first liner free energy relationship reported for the cyclodimerization of aromatic trifluorovinyl ethers to PFCB compounds.
authors.affiliation: Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, South Carolina, USA.
authors.forename: Bryan K
authors.initials: BK
authors.lastname: Spraul
authors.forename: S
authors.initials: S
authors.lastname: Suresh
authors.forename: Jianyong
authors.initials: J
authors.lastname: Jin
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Smith