Dimerization of terminal alkynes catalyzed by a nickel complex having a bulky phosphine ligand

Abstract

Ni(cod)(2)/P(t)Bu(3) system catalyzed the dimerization of terminal alkynes to give (E)-head-to-head dimerization products, in which the stannylacetylene dimer could be applied to a one-pot synthesis of a conjugated enyne, when combined with Migita-Stille coupling.

Ligand‐Controlled Cross‐Dimerization and ‐Trimerization of Alkynes under Nickel Catalysis

“…[11] As for the first step of the nickel-catalyzed reactions of terminal silylacetylenes via C(sp) À H bond cleavage, oxidative addition of the acetylenes to nickel(0) species to give (R 3 SiCC)(H)Ni(II) complexes is usually postulated. [5,9] It may be reasonable to consider that the subsequent insertion of the internal acetylene or successive double insertion of internal and terminal acetylenes to the Ni À C or Ni À H bonds of the key intermediates and reductive elimination afford enynes and dienynes. It was confirmed that enyne 3aa did not react with 2a under the conditions used for entry 7 in Table 1.…”

“…[7] In the course of our study of regioand stereoselective alkyne cross-couplings using sil-A C H T U N G T R E N N U N G ylacetylenes, [4c,e,8] we have examined the reactions via C(sp) À H bond cleavage using Ni, since such reactions with this metal have been less explored. [5,9] It has been found that the combination of NiA C H T U N G T R E N N U N G (cod) 2 together with a pyridine-based ligand such as 4-(N,N-dimethyl-A C H T U N G T R E N N U N G amino)pyridine effectively catalyzes the cross-dimerization of diphenylacetylene with trimethylsilylacety-A C H T U N G T R E N N U N G lene. In contrast, the 1:2 cross-trimerization of the substrates takes place selectively using a triarylphosphine ligand in place of the pyridine.…”

Regio- and Stereoselective Homodimerization of Monosubstituted Acetylenes in the Presence of the Second Generation Grubbs Catalyst

“…Many examples of effective run of the process in the presence of transition metal complexes have been described. Catalytic activity in the process has been reported to be shown by complexes of such metals as palladium [4,[7][8][9][10][11][12][13], rhodium [14][15][16][17][18][19], ruthenium [20][21][22][23][24][25][26][27][28][29], nickel [30], iridium [31][32][33], osmium [34,35], iron [36] and the f-block metals [37][38][39]. However, a highly selective synthesis of conjugated enynes by dimerization is still a challenging process.…”

Nickel‐Catalyzed Addition of Pyridine‐N‐oxides across Alkynes

“…[7] A plausible mechanism for this hydroheteroarylation reaction is shown in Scheme 1. We consider that the alkynecoordinated nickel(0) species A [8] undergoes oxidative addition to the C2 À H bond, [9,10] giving the pyridyl(hydride)nickel species B. Hydronickelation in a cis fashion then provides the alkenyl(pyridyl)nickel intermediate C.…”