The dimerization of ethylene gives 1-butene is another example of a hydrovinylation. In the Dimersol and Alphabutol Processes, alkenes are dimerized for the production of gasoline and for comonomers such as 1-butene. These processes operate at several refineries across the world at the scales of about 400,000 tons/year (2006 report).[2] 1-Butene is amenable to isomerization to 2-butenes, which is used in Olefin conversion technology to give propylene.
Hydroarylation
Hydroarylation is again a special case of hydrovinylation. Hydroarylation has been demonstrated for alkyne and alkene substrates. An early example was provided by the Murai reaction, which involves the insertion of alkenes into a C-H bond of acetophenone. The keto group directs the regiochemistry, stabilizing an aryl intermediate.[3]
When catalyzed by palladium carboxylates, a key step is electrophilic aromatic substitution to give a Pd(II) aryl intermediate.[4] Gold behaves similarly.[5]Hydropyridination is a similar reaction, but entails addition of a pyridyl-H bond to alkenes and alkynes.[6]
In organic synthesis
As first reported by Alderson, Jenner and Lindsey, hydrovinylation uses rhodium- and ruthenium-based catalysts. Catalysts based on iron, cobalt, nickel, and palladium have also been demonstrated. The addition can be done highly regio- and stereoselectively, the choices of metal centers, ligands, substrates and counterions often play very important role.[7][8][9] N-heterocyclic carbene complexes of Ni allow the selective preparations of functionalized geminal olefins or 1,1-disubstituted alkenes.[10][11]
