Synthesis and aromatization of 2+2 cycloadducts of butadienes and tetrafluoroethylene

Article abstract of DOI:10.1016/S0022-1139(00)80399-1

Passing tetrafluoroethylene (TFE) and hydrocarbon dienes down a hot tube at 600 deg C with a contact time of a few seconds produces substituted fluorobenzenes.Specifically, tetrafluoroethylene and butadiene form 1,2-difluorobenzene.The aromatics produced bythe pyrolysis of TFE and methyl-substituted butadienes do not necessarily result from eliminating HF from 2+4 adducts of the starting materials.Solid-acids such as alumina or silica/alumina accelerate the ring-expansion elimination of the 2+2 cycloadducts.Aromatic products result from the preformed 2+2 cycloadducts at temperatures 200 deg C lower than the corresponding thermal reaction.The solid-acids can also influence product regiochemistry.