DONOR-SUBSTITUTED FURANS AND 1,2-BIS(TRIFLUOROMETHYL)ETHYLENE-1,2-DICARBONITRILE - THE HIDDEN CYCLOADDITIONS

2-p-Tolyloxyfuran or 2-methoxyfuran and BTE, the title compound rapidly establish equilibria with [2+2] and/or [4+2] cycloadducts as monitored by F-19 NMR analysis; finally, the irreversible opening of the furan ring and concomitant closure of a cyclopropane ring wins. Dissociation constants of four trans-adducts and one cis-adduct were measured over a temperature range of 90 degrees C; the reaction enthalpies and entropies art discussed.