The more general reaction,hydroalkenylation, is the formal insertion of an alkene into the C-H bond of anyterminal alkene. The reaction is catalyzed bymetal complexes. A representative reaction is the conversion ofstyrene and ethylene to 3-phenybutene:[1]
Thedimerization of ethylene which gives1-butene is another example of a hydrovinylation. In theDimersol andAlphabutol 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 to2-butenes, which is used inolefin conversion technology to givepropylene.
The addition can be done highly regio- and stereoselectively, although the choices of metal, ligands, and counterions often play very important role. Many metals have also been demonstrated to form active catalysts, including nickel[3][4][5] and cobalt.[6][7][8]
In a stoichiometric version of a hydrovinylation reaction, nucleophiles add to an electrophilictransition metal alkene complex, forming a C-C bond. The resulting metal alkyl undergoes beta-hydride elimination, liberating the vinylated product.[9]
Hydroarylation is again a special case of hydrovinylation. Hydroarylation has been demonstrated for alkyne and alkene substrates. An early example was provided by theMurai reaction, which involves the insertion of alkenes into a C-H bond ofacetophenone. The keto group directs the regiochemistry, stabilizing an aryl intermediate.[10]
A Murai reaction (X = directing group, typically X = O).
When catalyzed by palladium carboxylates, a key step iselectrophilic aromatic substitution to give a Pd(II) aryl intermediate.[11] Gold behaves similarly.[12]Hydropyridination is a similar reaction, but entails addition of a pyridyl-H bond to alkenes and alkynes.[13]
^T. V. RajanBabu; G. A. Cox (2014). "5.32 Hydrovinylation Reactions in Organic Synthesis".Hydrovinylation Reactions in Organic Synthesis.Comprehensive Organic Synthesis II (Second Edition). Vol. 5. pp. 1582–1620.doi:10.1016/B978-0-08-097742-3.00533-4.ISBN978-0-08-097743-0.
^Ho, C.-Y.; He, L. (2010). "Catalytic Intermolecular Tail-to-Tail Hydroalkenylation of Styrenes with alpha-Olefins: Regioselective Migratory Insertion Controlled by a Nickel/N-Heterocyclic Carbene".Angew. Chem. Int. Ed.49 (48):9182–9186.doi:10.1002/anie.201001849.PMID20853303.
^Ho, C.-Y.; He, L. (2012). "Shuffle Off the Classic Beta-Si Elimination by Ni-NHC Cooperation: Implication for C–C Forming Reactions Involving Ni-Alkyl-Beta-Silanes".Chem. Commun.48 (10):1481–1483.doi:10.1039/c1cc14593b.PMID22116100.
^Hilt, G.; Danz, M.; Treutwein, J. (2009). "Cobalt-Catalyzed 1,4-Hydrovinylation of Styrenes and 1-Aryl-1,3-butadienes".Org. Lett.11 (15):3322–5.doi:10.1021/ol901064p.PMID19583205.
^Jia, C.; Kitamura, T.; Fujiwara, Y. (2001). "Catalytic Functionalization of Arenes and Alkanes Via C-H Bond Activation".Acc. Chem. Res.34 (8):633–639.doi:10.1021/ar000209h.PMID11513570.
^Shen, Hong C. (2008). "Recent advances in syntheses of heterocycles and carbocycles via homogeneous gold catalysis. Part 1: Heteroatom addition and hydroarylation reactions of alkynes, allenes, and alkenes".Tetrahedron.64 (18):3885–3903.doi:10.1016/j.tet.2008.01.081.
