Synthesis of <i>p</i>‑Xylene from Ethylene

As oil supplies dwindle, there is a growing need to develop new routes to chemical intermediates that utilize alternative feedstocks. We report here a synthesis of <i>para</i>-xylene, one of the highest volume chemicals derived from petroleum, using only ethylene as a feedstock. Ethylene is an attractive alternative feedstock, as it can be derived from renewable biomass resources or harnessed from large domestic shale gas deposits. The synthesis relies on the conversion of hexene (from trimerization of ethylene) to 2,4-hexadiene followed by a Diels–Alder reaction with ethylene to form 3,6-dimethylcyclohexene. This monoene is readily dehydrogenated to <i>para</i>-xylene uncontaminated by the <i>ortho</i> and <i>meta</i> isomers. We report here a selective synthesis of <i>para</i>-xylene, uncontaminated by the <i>ortho</i> or <i>meta</i> isomers, using ethylene as the sole feedstock.