Catalytic Dimerization of Alkynes

Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

“…The structure motif of 1,3-enynes can be found in several natural products, e.g., histrionicotoxins ( histrionicotoxin 283A ) ( Stork and Zhao, 1990 ) and gephyrotoxin ( Daly et al, 1977 ), found in the skin of poison frogs of the family Dendrobates histrionicus , in drugs, e.g., terbinafine, which acts as an antifungal ( Leyden, 1998 ) or oxamflatin, which acts as a HDAC inhibitor ( Kim et al, 1999 ), and moreover in functional materials ( Figure 1 ). ( García-Garrido, 2014 ).…”

“…In recent years, several synthetic routes toward 1,3-enynes have been described. One of the most used synthetic methods is palladium-catalyzed cross-coupling reactions, e.g., Sonogashira reactions ( Adamson et al, 2019 ) or Heck-type reactions ( Wen et al, 2011 ) which are generally performed in excellent yields and good regio- and defined stereoselectivities ( García-Garrido, 2014 ). Besides, the Wittig olefination ( Karatholuvhu and Fuchs, 2004 ) of propargylic aldehydes/ketones, elimination reactions starting from propargylic alcohols ( Sartori et al, 1996 ; Ye et al, 2018 ) for the construction of the carbon-carbon double bond, or rearrangement reactions in Corey-Fuchs-type reactions ( Shi Shun and Tykwinski, 2003 ) of vinyl ketones have been described.…”

“…One big drawback of all mentioned synthetic methods is the rather low atom economy for olefination or rearrangement reactions and the synthesis of the used starting materials, e.g., alkynyl-bromides or iodides (light-sensitive materials) or vinyl-halides. Because of the sometimes challenging syntheses, the hydroalkynylation (= dimerization) of an easily accessible terminal alkyne with another alkyne is an interesting and highly atom economic approach toward 1,3-enynes ( García-Garrido, 2014 ; Trost and Masters, 2016 ). Also, some reports with main group ( Dash and Eisen, 2000 ; Hasenbeck et al, 2019 ) and lanthanide catalysts ( Nishiura et al, 2003 ; Ge et al, 2007 ; Platel and Schafer, 2012 ), early transition metal- ( Cembellín et al, 2020 ), but mainly noble-metal-catalyzed dimerization protocols have been published (e.g., Ru ( Barsu et al, 2020 ), Rh ( Katagiri et al, 2008 ), Ir ( Ohmura et al, 2000 ), Pd ( Chen et al, 2013 )) ( Trost and Masters, 2016 ).…”

Dimerization of Terminal Aryl Alkynes Catalyzed by Iron(II) Amine-Pyrazolyl Tripodal Complexes with E/Z Selectivity Controlled by tert-Butoxide

“…Catalytic dimerization of terminal alkynes provides a simple and atom economic preparative route to conjugated enynes, which are useful building blocks for the synthesis of functional materials and biologically active compounds, and a number of transition metal complex catalysts of precious metals, such as palladium, ruthenium, and rhodium, have been developed. 1−3 Despite these advances, effective control of regio- and stereoselectivity has been a long-standing challenge due to the potential formation of a mixture of ( E )- and ( Z )-isomers and gem -stereoisomer, which limits the application of this process. 1−3 The nature of the metal, specific ligand sphere, and substituents on alkyne substrate are the main parameters that govern the regio- and stereoselectivity of the catalyst.…”

“…1−3 Despite these advances, effective control of regio- and stereoselectivity has been a long-standing challenge due to the potential formation of a mixture of ( E )- and ( Z )-isomers and gem -stereoisomer, which limits the application of this process. 1−3 The nature of the metal, specific ligand sphere, and substituents on alkyne substrate are the main parameters that govern the regio- and stereoselectivity of the catalyst. 2 Solvents could also play a role in the selectivity, as observed in the reaction catalyzed by the combination of Rh(CO)(PPh 3 ) 2 Cl/K 2 CO 3 /ICH 3 .…”