Tandem catalysis for asymmetric coupling of ethylene and enynes to functionalized cyclobutanes

Cyclobutanes sourced right from ethylene Ethylene is one of the highest-volume commodity chemicals manufactured from fossil fuels. It is mainly used to make plastic, although its ready availability incentivizes its expanded use in pharmaceutical synthesis. Pagar and RajanBabu now report that a cobalt catalyst can couple ethylene with enynes (another comparatively inexpensive feedstock bearing carbon-carbon double and triple bonds) to make complex chiral molecules. Initially, the ethylene reacts with the enyne's triple bond to form an isolable cyclobutene compound. At longer reaction times, the same catalyst can add a second equivalent of ethylene enantioselectively to form cyclobutanes with a quaternary chiral carbon center. Science , this issue p. 68