DONOR-SUBSTITUTED FURANS AND ,2-BIS(TRIFLUOROMETHYL)ETHYLENE-1,2-DICARBONITRILE - A NOVEL REARRANGEMENT AND ITS STERIC COURSE

Opening of the furan ring and concomitant closure of a cyclopropane ri ng was observed in the reaction of 2-methoxy- and 2-p-tolyloxyfuran wi th 2,3-bis(trifluoromethyl) fumaronitrile (trans-BTE). Electrophilic 5 -attack gives rise to a zwitterion which can rotate about the acceptor bond, dissociate to reactants, or furnish diastereoisomeric cis-3-cyc lopropylacrylates. In the presence of pyridine, 1,3-prototropy convert s the zwitterion to 5-substituted furans.