Alkenes, reductive coupling hydrogenation

Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen... 

Ihmels H, Otto D (2005) Intercalation of Organic Dye Molecules into Double-Stranded DNA - General Principles and Recent Developments. 258 161-204 Iida H, Krische MJ (2007) Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen. 279 77-104 Imai H (2007) Self-Organized Formation of Hierarchical Structures. 270 43-72 Indelli MT, see Chiorboli C (2005) 257 63-102 Inoue Y, see Borovkov VV (2006) 265 89-146 Ishii A, Nakayama J (2005) Carbodithioic Acid Esters. 251 181-225 Ishii A, Nakayama J (2005) Carboselenothioic and Carbodiselenoic Acid Derivatives and Related Compounds. 251 227-246... 

Given the preferential complexation of an alkyne compared with an alkene to ruthenium, the notion that alkene-alkyne coupling (Scheme 1.5) would occur seemed remote. However, to the extent that formation of the ruthenacyclopentene occurs, it can become irreversible because there exists a low-energy pathway by which it can further react, namely (5-hydrogen elimination. A final reductive elimination then completes a catalytic cycle wherein an alkene and an alkyne couple to form a 1,4-diene. 

In the next step, the product-yielding fi-hydride elimination (step D) can occur only after an internal rotation (step C) around the former double bond, as it requires at least one fS-hydrogen to be oriented synperiplanar with respect to the halopalladium residue. In some cases, anti elimination was made possible by suitable substrates or conditions leading to an type mechanism [16, 17]. The subsequent syn elimination yielding an alkene and a hydridopalladium halide is, however, reversible, and therefore, the thermodynamically more stable (E)-alkene is generally obtained when the coupling reaction is performed with a terminal alkene. Reductive elimination of HX from the hydridopalladium halide, aided by the added base, regenerates the active catalyst and thereby (step E) completes the catalytic cycle. 

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